Larry Strowbridge [mailto:strowbridgeprocess@yahoo.com]


How Can I Tame My ES 175 (Howlin' Wolftone) 

I've been really enjoying your publication - it's nice to get expert advice
 from folks who aren't trying to sell you something. Keep up the good work.
 
 For several years, I've been using a Carvin "vintage tube" 50W combo with
 EL84's, and have always really liked the sound of the amp. However, I
 recently got more into jazz and have switched from a Strat to an ES 175. For
 some reason, when playing that guitar through the Carvin amp, certain
 low-frequency notes feed back horribly as soon as I even touch them, even at
 low volumes. My questions are:
 
 1 - What causes this? (I've heard it described as some sort of "resonant"
 thing between the guitar and amp)
 
 2 - Is there anything I can do about it, other than avoiding that guitar/amp
 combination?
 
 3 - Do you have any general suggestions about amps that work well with
 hollow-body jazz guitars (open vs. closed back, 6L6's vs EL84's, etc.)?

David Wilson of TQ forwarded me your question. I shall copy him back as
well, in case he also knows someone else on the Board of TQR who can
supply additional information.

I am not totally sure I understand what's causing the phenomenon you
mentioned but I'll take a stab at it.

ANSWER

First of all most people who play through EL84 equipped amps do it
because of the unique crunchy tone that those tubes exhibit. Right away that is kind of contrary to the JAZZ thing, especially on big hollow body axes like an
ES-175. I remember a few years ago I invested in a beautiful old Blonde
1950 Gibson ES-5 (pre-switch) and took it, the following weekend, to
play in the band I had at the time, which was a big R&B thing with 10 
pieces, 5 of them horns. Well, that thing fed back like there was no
tomorrow, and I was using a '64 Super Reverb. Needless to say it didn't
get used again. I found that when I played it I had to pay special
attention to damping the strings otherwise the big acoustic chamber of the body of
the guitar was a feedback arena. I also play pedal steel guitar and have
used, since 1977, a PEAVEY LTD 400 solid state amp. The steel needs
tremendous low end and lots of CLEAN power behind in. Now I do not have
to deal with an acoustic chamber in that, but the point is that total
clean power really brings out the best when dealing with clean tones and
especially JAZZ stuff. Most Jazzers that I know do NOT want any upper
level harmonic distortion in their tone to be able to spit out all those
Kenny Burell and George Van Epps riffs if you know what I mean.

It could be that your amp is giving you just the right amount of crunch
to produce upper level harmonic feedback right off the note as you hit
it. Try using the CLEANEST setting that your amp has, eliminating
anything to do with tube crunch or distortion. Keep the F-holes away
from direct penetration of sound from the amp. Turn the guitar away from
the speakers and get off-center form them as well. Try using damping
techniques as long as it doesn't hamper your playing style, and maybe
even take your ES-175 to your local Music Store and try several
different amps there to see if the phenomenon is there on different kinds of amps.
Even try some solid state stuff as that may make a difference. I know
that sounds like sacrilege, but solid state does have it's place as I
mentioned with the pedal steel thing. Every pedal steeler I know uses a
Peavey (or equivalent) solid state thing. So there may be some hope
there. If you stay with tubes, 6L6's have a tendency to have more
headroom then an EL84, you might try that too. Make settings on your
amps stay as CLEAN as they can get.

I really can't recommend anything specific in the way of open
back/closed back designs. Closed back amps have a tendency to be more
direct and disperse the sound LESS filling then an open back, which more
or less fills the room. That might be a way to attempt to go, but it
will be through experimentation on your part. I have to admit that as an
electric player, most of my gigs are done through solid body guitars and
occasionally through thinline hollow bodies like ES-335's or Telecaster
Thinlines. Feedback is a problem with those guitars but MUCH LESS then a
big jazz box due to the center block through the body for the pickups.
But I still have to be aware of it. In those cases I try to get the
guitar away from directly in front of the amp where it can pickup less
frequencies. Larger rooms help a lot too, as they eliminate the chance of
sound coming back into the F-holes and disperse it better. High ceiling
clubs are real nice for that too.

You have a tough one, I hope this small bit of info is helpful and maybe
David Wilson can also forward your question on to one or two others.
Best of luck with it.

David Boze

 

What are FREDS, Why Do I Need  Them and Where Can I Get Them!?!

A FRED is a diode. It performs the same function as the standard 1N4007 diodes most guitar amplifiers employ. Like a 1N4007, it has an anode and a cathode. The cathode on a 1N4007 is designated by a white band on the diode body. The cathode in a schematic drawing is designated by a line in front of an arrow. On Fender schematics, the cathode is distinguished further by a "+"; the anode with a "-". Upon inspection of your amplifier, it should be easy to find and understand which end is which. Please remember that not all amplifiers look the same under the hood. On a Fender amp, it will be quite easy to sniff out the 1N4007's..well, on old Fenders anyway..some others may take a little snooping around. If you cannot locate the silicon diodes in your amp or are unsure at all about which end is which, HIRE A QUALIFIED TECH to perform the mod. In experienced hands this swap should take 10 minutes.

The FRED is different in appearance than the familiar cylindrical shape of silicon diodes. It is square shaped with a metal plate on the back which extends beyond the body. The two leads (cathode/anode) extend from the diode body on the same side; this is different than a silicon diode which has the leads extending from opposite sides of the diode body. The cathode on the FRED is the left lead when looking at the FRED from the top with the leads facing you. There is some printing on the FRED body..this is the top; the metal plate is on the back side. The metal plate is also the cathode. Let me repeat that. THE METAL PLATE IS ALSO A CATHODE CONNECTION. You don't need to know why; you just need to know that it is. (in some applications this plate is used as a heat sink--this is not applicable in vacuum tube amps because the current is so low..) When we install FREDS, we wrap the plate and body with electrical tape to insure that it doesn't inadvertently short against other components.

The actual installation is quite simple. Once the original silicon diodes are identified, remove them and insert the FRED in its place. In Fender amps, one FRED will take the place of the 3 diodes in series on the small eyelet board in the upper left hand side of the chassis. There typically will be six 1N4007's total--3 for each side of the B+ winding (red leads coming out of power transformer). Use one FRED for each side. This will differ depending on model and year, but the concept is basically the same. One exception is later Fenders and most Marshall/Hiwatt style amps. On these, there will be 4 diodes. On the schematic they form a "square" with two of the anodes going to ground. ALL FOUR must be replaced on amplifiers employing this type of rectification. If there is any doubt in your mind, let someone who is more knowledgeable perform the mod. Remember to insulate the metal plate with good electrical tape to avoid any contact with other components. It is also a good idea to use a heatsink (a hemostat will work nicely) when soldering the FRED; the heat of your soldering iron can damage the little bugger. And at risk of sounding redundant, remember that the cathode is the banded end of the 1N4007 and is the LEFT HAND LEAD on the FRED when looking at it from the top with the leads facing you. Pretty straightforward stuff..

As I mentioned in the article in  TQR, the installation of FRED's in the power supply of your amplifier will make the amp smoother and more musical. It's a mod that you will be glad you performed.

We have 11A 1200V FRED's for sale for $6.00 a piece plus a nominal shipping charge of $5.00. We also are offering a complete diode/negative bias supply board that will drop right in on older hardwired Fenders. It is available for $30.00 plus $5.00 shipping. Please specify model of amp it's going in when ordering.

Parts can be ordered by e-mailing us at

MarkBaier@VictoriaAmp.com or calling us at 630-820-6400/630-369-3527

Please leave a message if you get the machine..when we're testing amplifiers, we can't hear the phone ring!

Hope this helps clear up what's involved when installing these groovin' diodes!!

Keep jammin',

Mark Baier

Best Speakers for a Vibrolux Reverb? 

Hello Dave:

 I am planning on purchasing a Fender Vibrolux Reverb amp in the
 future. I am trying to find one in the 60's-70's era. In order to
 bring it back to Black Face specs, do I need to replace the stock
 speakers? Any recommendations? I am looking for a "warm" sound. I am
 currently playing a PRS McCarty Rosewood guitar. Also, is there any particular distortion (not harsh) pedal and delay pedal that you can recommend?

 Thanks for your help.

 Jerry LaBrecque
 Saco, Maine 

ANSWER:

With the exception of original Jensen C10N's I personally find any other
Vibrolux Reverb OEM speakers to be junk, especially Oxford and CTS
Ceramics. While I do NOT endorse anybody's speakers, I have heard great tones from>
the following 10's (all at 8 ohms, for your amp, by the way):
Jensen Reissue C10Q
WeberVST C10Q, C10N
Celestions
Eminence 50 watt ceramics
Mojo 50 watt ceramics.

There are others too. I just haven't heard all of them.

All of these speakers will produce slightly different tones and making a decision
will depend on your ears and what you like to play. If your speakers
have a Fender BLUE label, put them in a box, save them as
original and upgrade to something I mentioned above. You'll have to
experiment and hear what you like best. The Oxford ceramics are
especially DOGS.

If you get a silverface Vibrolux Reverb, be sure to have it converted to blackface
specs. Maybe you'll be lucky and find a '66 VR with original Jensens in it. It doesn't get much better then that!! My personal '66 VR has those, and they are luscious.
I really don't use any stompboxes but I do own a couple that I can
stomach. The first and favorite is a REAL TUBE, the one with a real
12AX7 in it and it has a 3-band EQ (not the one with the tone knob), and
I own an original Ibanez TS-9 Tube Screamer. I've had others and hated
them all, but my playing now is usually sans effects. I go straight in
to an old Fender and that's all I need in 98% of my playing.
David Wilson, publisher of TQR, swears by the Klon Centaur. He says they
are THE BEST HANDS DOWN. I have not tried one, but others have said the
same to me.
 

Can I use a guitar cord to connect my amp to an extension speaker cabinet?

More Tone From My Blues Junior?

I happen to have a Blues Jr. in my shop at the moment and (now that it's fixed) I'm trying to figure a little on your request.: The one I have here doesn't really sound "bassy", I'd say it was fairly even, though it is a little "small box" sounding. A few suggestions assuming your amp essentially is working properly:

The ToneQuest Report is a great publication. I have a reissue ‘65 Blackface Deluxe. How do these measure up to the originals?

Can I Bring My RI Vibroverb Up To "Original" Specs?

Maintenance On a '65 Super?

I just purchased a '65 Fender Super Reverb that appears to have been well-played but never modified in any way. The amp has not been serviced in a while, I'm sure. What would you recommend before I start gigging with it?

Thanks for your help.

Brian 

ANSWER:

Brian - Now, this is what I do -- I can’t vouch for anybody else, since some techs just "fix problems, " and there are "mills" that specialize in fixing electronic gear of all kinds, and they are not necessarily going to meticulously check every thing that I do. That's the way it is in the repair business, so please keep that fact in mind.

Here are some basic checks that should be performed on any amp when it’s on the bench to be "tuned up":  

1. Replace filter caps as needed.
2. Check values of voltage dropping resistors and change any that are off more than 10%. 

3) Re-tension all tube sockets

4) Check and replace tubes as needed.

5) Set bias current on power tubes.

6) Clean all pots, jacks and switches.

7) Check all coupling caps for leaking DC (especially in tweed and brown and/white Fenders and any other '50's amps). Replace as necessary.

8) Replace all pre-amp electrolytic caps (on the cathodes).

9) Replace bias electrolytic cap.

10) Check values of screen and grid resistors on the power tubes and replace any that are off in value.

11) Replace junky components like chocolate drop coupling caps in Fender amps.

12) Inspect for cracked solder joints and repair if needed (several key spots are always suspect, and I’ve learned which ones they are).

13) Inspect all grounds for evidence of problems, re-solder as necessary 

14) Check all key voltage points in the amp.

15) Inspect speaker cone for evidence of cracking or rubbing coil. Clean out any dirt accumulated around surround (otherwise it acts as sandpaper to destroy the outer edges of the cone).

16) Check the polarity of the speakers. You'd be surprised how many speakers

are wired out of phase in multiple speaker amps (when the original speakers have been changed).

Most good techs will give the thing a total going over so that it will save the customer another bench charge very soon in case another problem surfaces in the near future. Like in many cases once you change filter caps, it raises voltages in the amp, and some components may stress out due to that. Plus I have found that in almost all cases most players care enough to have the BEST tone they can get coming out of their amp. In order to do this, one needs to assure that all parameters of the amp are functioning to factory specs.

As far as changing parts, I ALWAYS GET the customer's approval BEFORE doing it so there are no surprises. I have, on rare occasions, had people LIKE the sound better BEFORE it got tuned. Tweed Fenders are suspect here. Apparently, they liked the sound the 'aged' components gave them. Go figure. Then what you do is put all the old parts back in and send them on their way. 

If an amp has a two prong plug, I usually leave it as is unless requested to do otherwise, as I HATE replacing power cords, but I do them all the time (I just don't volunteer to do them!).

Dave Boze, Detroit, MI 

Upgrades for a Tele Deluxe
I just bought an American Deluxe Tele after trying out hundreds of Teles and deciding I'd have to custom build one if I wanted everything I was looking for. This is a great axe but it doesn’t get that dry midrange snarl with the noiseless pickups. These PUs are beautiful sounding and I don't want to replace all of them--just the bridge so I can get the '52 Broadcaster sound.  My question is what PU do you recommend and how will replacing 1 PU affect the "mix" of all 3 PUs?  Also, what else might I do (bridge, saddles, etc.) that may enable a more traditional Tele tone without altering the guitar too much? Thanks!

Chris Wallop
email: chris.wallop@arm.com

ANSWER:
Chris – great guitar!  We like the scooped out “strat” back and the fret work on these guitars a lot.  The "noiseless" pickups in your new Tele are hum-cancelling stacked single coils.  We recommend that you stick with a hum-cancelling design if you're going to replace just 1 pickup, and our first choice would be a Joe Barden Tele bridge pickup. Expect zero noise and hum and a dramatically broader range of Tone – lots of bite, but much, much fatter all the way around.  The only potential drawback to the Barden is that you won’t maintain the classic look of a traditional Tele bridge pickup since the Barden is a double-blade design.  Seymour Duncan also makes "noiseless" stacked single coil pickups for Telecaster guitars and one member of our advisory board, James Pennebaker, uses these pickups in specific studio applications (see Pennebaker Interview, The ToneQuest Report Volume 1, Number 1.)  But we can’t recommend them for a “snarl and spank” player.  Our first choice for more traditional single-coil Tele Tone and appearance are Harmonic Design Vintage Plus pickups.  With the Vintage Plus you’ll get classic looks and slightly more output and a wider tonal range than vintage Tele pickups, and the neck pickups can be ordered with covers to match your pickguard, giving you a cool Esquire illusion from Row 10!  No matter what you choose, Chris, we suspect that the vintage snarl and spank you’re seeking could prove to be very elusive with your stock pickups, and if you replace the bridge pickup first, the neck pickup will soon follow.  I’ve done the same thing myself more than once!

Regarding relatively uncomplicated and easily reversible upgrades to your Telecaster—you might consider installing new, vintage-style brass bridge saddles and while you're at it, upgrade the nut by replacing the original with one made from bone – a simple job for a competent guitar repair shop.  My favorite guitar tech here in Atlanta buys pre-packaged, sanitized dog bones to make his nut blanks!  Does that make my Tele bark?  I dunno, but you should have no trouble finding someone to cut and fit a bone nut in your guitar.  It will make a difference that you’re likely to appreciate.  If you don't like the appearance of brass saddles with your steel bridge plate and other chrome hardware, try the vintage steel saddles.  Neither the vintage steel or brass saddles are individually adjustable for intonation on each string, but you’ll get more than “close enough” and the potential increase in sustain will be worth the compromise.

How Do I Get Blackfoot Marshall Tone?
A few years back, I had the pleasure of opening for Ricky Medlocke
(Blackfoot). His tone was remarkable. I noticed he was using Marshall
superleads, but I didn't get a chance to see what else he was using. Since
that time, I have tried several amp/effect combinations, and have not been
able to capture the magic. I'm not a big fan of master volume amps and I'm
sure plugging straight into a superlead is not the answer. Is there anyone
that can help me capture the tone I am searching for?

David Mattingly
fraziertm@navair.navy.mil

ANSWER:
Yeah, the opening riff of "Train Train" always gave me quite a charge. Not being a fan of master volumes either, I'd highly recommend a stock 70's non-master 4-input Marshall (with EL34's please), either 50 watt or a Superlead 100, and a straight-front Marshall 412 cab with 25's or 30's from the same period. Use a THD Hot Plate Power Attenuator between the amp and cab to bring the volume to a respectably sane 90's stage volume. Turn every knob on 10, pull out your favorite Gibson and trusty guitar cable (no pedals needed) and I do believe you'll find that tone.

- Peter Stroud
The Sheryl Crow Band 

Pro Reverb Mods?
Hello. Before my question, I just want to say thanks for the cool
page full of great information!! OK here's my situation: As a
musician/student on a tight budget (imagine that) I'm looking
for one versatile amp for small club gigs. Style is blues/rock/funk
with jazz leanings (ie: Grant Green, Kenny Burrell). I've played
some great smaller amps (BF Vibrolux, BF Pro Reverb) but they
don't stay clean enough for my style at band volume; Twins are
the opposite extreme. So...I'm looking at a 70 watt Pro Reverb
as a (hopefully) good compromise (w/ a TubeScreamer or
FullDrive 2 for overdrive but still keeping a nice clean option for
jazz) Opinions? Are there mods you can recommend to improve
the sound of this amp (ie: 'un-sterilize' or 'open it up' a bit)?
Thanks!

Paul DiGirolamo
paul_d@mindspring.com 

ANSWER:
I am not the world's biggest fan of the (so-called) 70 watt Pro Reverb
(or for that matter, the 70 watt Super and the 135 watt Twin). But, 
I have worked on many of them and managed to get them to sound a whole
lot better. In reality, they really aren't 70 watts -- something less, actually, 
but what you are talking about are the amps with the so-called 'ultra linear' transformers.

One thing that works to your favor is that
this model PRO has no rectifier tube. It's solid state, as on a
Twin. That increases headroom a lot and prevents a lot of the sag
associated with a BF amp. Some really like that, but it sounds like you
have the opposite preference for your style, and that's fine. These amps have
Master Volume, which I find worthless, and also the dreaded pull-boost, which
has got to be one of the worst attempts at distortion on the planet.
Having said that, one thing you can do right away is disconnect all that
junk and replace certain voltage dropping resistors in the power
section to get them more in-line with what a Blackface version would
have been. A big Zener diode can sometimes be placed in the
power section to lower all the voltages, but in your case, since you're 
looking for more headroom, I would not mess with it.

Other things you can do include:

1) Remove all the 'tone sucking' caps off the reverb and power sections
(a CBS invention to 'help' things out, they rob a lot of tone)
2) Install a .002 uF cap between the pre-amp and power sections (instead
of that awful .01 uF that's there that gives nasal midrangey tones).
3) As stated above, remove MV and pull boost features
4) As stated above, change the power section voltage dropping resistors
(to be more in line with BF specs). It'll still have the high voltage on
the plates, which is what you want.
5) Change any inefficient chocolate drop coupling or tone section
capacitors to better ones (I like Sprague 715 Orange Drops, much more
efficient). To me this opens the amp up a bit more.
6) In the pre-amp section, change some of the post BF stuff to more like
BF. This means adding an electrolytic cap here and there, mostly to the
cathodes of the pre-amp tubes (ref BF layouts). Typically it involves slightly
rewiring the reverb section, too.
7) Rebuild the power section so you can bias it. You can't with the
current design (this is a rebuild to BF specs). In these amps, the bias
adjust pot is on the BACK of the amp, not in it's normal BF position.
8) Change the speakers.....the originals are, in my mind, pretty bad
sounding (usually Oxford ceramics). Something like a Jensen (new or old)
C12N or a Weber (or one of many others ie JBL, EV, etc.) will make a huge improvement.
These amps can never be quite like their blackface predecessors due to the
'ultra-linear' transformers and the lack of both a rectifier tube and a
choke coil (CBS decided to save money and use resistors instead of the
choke coil). BUT, I recently worked on a SF Super Reverb
that was virtually the same chassis as yours (with exception of a 2
ohm output transformer). I made all of the changes I've mentioned and
replaced the junk speakers with a quad set of old Jensen C10Q's. I have
to tell you it was really a great sounding amp when completed. It did have a lot
more headroom then a stock SR, but overall the clean sound was really solid,
had a lot of tone, and I could play games with the overall sound by the type
of tubes I used and being able to set the bias of the power tubes. It
was one great sounding amp, and I think maybe similar to what you are looking
for. The 12" speakers of the Pro will help you more too. 

Dave Boze

Princeton Mods?
I'm thinking of buying a '68 Princeton Reverb that I saw in the store the other day. It sounded 
real nice for its size (the only thing I felt it lacked was low end -- I am hoping the mods will 
help). So here are my questions: what is a fair price for a '68 SFPR, and how much should I 
expect to pay for the mods that you suggested in the "Whoop Ass" article? Also, can you
recommend a good tech in Austin, TX?

Thanks, Rob
rturknett@mail.utexas.edu

ANSWER:
I always HATE having to guess current market value for stuff, so I 
usually have to qualify it by asking if you want the 'selling' price or the 
'sitting on the shelf forever and collecting dust' price? Amps seem to be going up daily. 
It's hard to keep up with whatever people are paying this week for anything. I'd say a FAIR price
for a SFPR would be $300-$475, depending on what needed to be done to
it. If it was totally serviced and set up with fresh NOS American power
tubes, it would be toward the high end. If it needs a tune up and tubes, then
towards the low end. You have to decide what it's worth for you.

The parts I mentioned in the article are only a few dollars and probably
need to be matched and installed by a competent tech. When I do them, I
insist on a tune up at the same time to get the amp running in tip-top shape
(caps, tubes, cleaning, bias set, etc.). Then I convert to Blackface specs,
which is almost no work at all (change a couple fairly easy things),
then do the 'enhancement'. So in reality, I never just do the enhancement
on it's own, but if I did, I wouldn't charge too much, maybe for parts
AND labor about $65 or so. But usually, I wrap it up into a total tune up
and BF conversion, so the actual cost gets skewed into that.

Keep in mind that when you do this, a BETTER speaker is ESSENTIAL to
noticing any difference at all. If you use the wimpy little original (unless it's a
stock old Jensen C10N), you'll hardly hear a difference, since that speaker
is so inefficient. You have to junk it and get a better 10" or for
that matter, cut another baffle and put a huge 12" in there (lot's
to choose from, a WEBER or a Jensen Reissue C12N is most pleasing!). You
can cut a new baffle board for it and install repro cloth, or you can
cut the original baffle (in SF amps, I don't lose sleep over cutting a
baffle). But I generally recommend that people keep original parts
intact, so a quick trip to the lumber yard for a small piece of 5/8"
plywood is really worth it and won't cost you more than a few bucks. Then
if you decide to sell the amp later, you can put the original baffle back
on.

Low end will improve dramatically with the circuit enhancement I described, plus a
better speaker, preferably a 12". I even run mine through a 15 EV-SRO
in an extension cabinet sometimes. Talk about low end!!!

Little PR's are one of the best amps going.

Now..go get it!! As for a tech in your area, I'm pretty far away to be
able to do that ....Detroit.., why don't you go onto the WEBER VST amp
board and ask that question. Ted posts a guide of amp techs around the
country on his website 'www.webervst.com. It's a great site anyway, by a
guy who makes some great products

Dave Boze
Best Amp Repair

Z90's?
In my eternal search for pickups with "my sound", I have finally found P-90's. They appear to be  somewhere between the single coil and humbucker - basically, a "fat" single coil. I want a  hollow body for the "acoustic response". My budget does not allow for an old(or new)Gibson ES330, but a used Korean Epiphone Casino is not bad and can be had for a reasonable buck. Here's the dilemma. I've gotten different reports from manufacturers as to whether replacement  P-90's will fit a Korean Epiphone. Do you know anything about this? Also, any recommendations  as to choice of replacements? I've used many Duncans in my Strat over the years and am basically  happy with them. Fralin comes highly recommended. There's a new VP-90 by Harmonic Design that sounds promising. Any first hand experiences with a Z-90?, it's a single coil replacement for a humbucker cavity, also by Harmonic Designs. Any and all subjective observations are welcome. 

Mark Rabin
email: rabin@atecone.net

ANSWER:
Mark - We just completed an evaluation of the Harmonic Design Z90, which is indeed a replacement "P90" for guitars that are routed for a standard-size humbucking pickup. Our review will appear in the February issue of TQR, but for now, I can tell you that we recommend the Z90 very, very highly. The VP90 is intended to be a direct screw-on replacement for standard P90's. Our experience with Harmonic Design pickups has been consistently impressive. Call Scott Petersen and chat  with him about your needs, and I'm sure you'll be thrilled with the results.

Dave Boze

Fair Price for a Vibrolux Reverb
I read "Under 40 Watt of Whoop Ass" with some interest. What is a fair price for a 65/67 Vibrolux? Would you ever buy an amp sight unseen?  I'm a little reluctant to make a large purchase over the internet or mail order. Also, your writing really hit home. I'm playing a Fender VibroKing and I really like it but I'm sick of lugging it around and it is usually overkill for the venues I'm playing.  I have had one problem with the amp, it blows speakers.  My repair guy tells me the stock speakers are cheesy -- a real pisser considering the cost.  Can you suggest a replacement speaker that might be more durable and may even sound better?    Don McDevitt

ANSWER:
It will be hard to find a Blackface Vibrolux Reverb in good original condition for less than $1,000 and we’ve seen them listed as high as $1,600 recently.  However, the silver face models produced after 1967 can easily be converted to blackface specs, and with a speaker upgrade, you'll have an outstanding amp that’s every bit as good as a blackface model for $600-$800.

The Internet is a terrific source for vintage amps, but it's essential that you ask plenty of questions before making a decision.  Speak to the seller directly to discuss the amp's condition and maintenance history, and ask for Web references.  Jpegs are fine to drool over, but they are no substitute for verbal verification.  Crucial to Tone are the following considerations: Has the amp been serviced, and if so, what was done, when, and by whom.  If possible, get contact information for the tech that worked on the amp.  Are the transformers original?  If the seller doesn’t know, have the date codes on the trannies verified before you agree to purchase the amp.  Replacement transformers on vintage amps can dramatically alter the tone and not always for the better.  Ask to verify the date codes on the speakers – they should be of the same series.  Have the speakers been reconed?  This may be unimportant if you plan to upgrade, but reconed vintage speakers can be as good as the originals or worse than a cheap imitation depending upon who reconed them. Unless the seller has personally replaced the tubes, plan to replace them.  Also budget  $50-$75 to have the amp checked out after you receive it.  Original filter caps may need to be replaced, and if you plan to install new tubes you’ll want to have the bias on the power tubes adjusted.

     We've had great success finding desirable amps on the Internet at good prices, but get all of the details you need to avoid surprises.  And be sure to specify how the amp will be packed with the seller.  That means packed upside down with the weight of the amp chassis at the bottom of the box.  The amp should be double-wrapped in bubble wrap and floated in packing peanuts with the power tubes and rectifier tube removed, wrapped in bubble wrap, taped to a piece of cardboard and tucked inside the amp.  The amp should also be packed in a box of sufficient dimensions to allow at least 6 inches of space between the amp and the box on all sides. And don’t forget insurance at full value!

Regarding replacement speakers for your VibroKing -- we recommend Jensen vintage reissue P10R speakers, which Fender now offers as the stock speaker in the VibroKing (we assume the speakers your tech is referring to as "cheesy" are not Jensens.) But be sure to buy P10R’s with date codes after January 1999.  The tone of the early versions is inferior to that of the later models.       

VibroKing Pots
My VibroKing's volume pot seems to be extra sensitive. There is a very
wide range in volume between 0 and 4. The amp's loudness seems to be
maxed out a little above 4. Any adjustments in volume need to be made
in tiny increments. Why does this control seem so "condensed". 

ANSWER:
To me it sounds like you have a linear taper pot in there instead of a
log (audio) taper pot. I'll bet somebody changed it out (for whatever
reasons) and put in the correct value (500K ohm), but didn't realize
they put in a linear taper. Some people don't understand that there is a
difference. If you are not solder impaired, pull the brain and try to
replace the pot yourself. It should be a 500K ohm audio taper pot, but
there is a minor problem. In those (I just worked on one), the volume
pot is ganged with another pot. It's two pots in one, controlled by the
same shaft, I believe. On the schematic it's listed as R4A, and R4B is
fed in from the reverb circuitry. I remember seeing it when I worked on
that last VibroKing. You'll probably have to go to an real electronics
store to get the right pot if that is the problem. They don't sell those
at Radio Shack I am quite sure. Try that. Sure sounds like it to me.
That's got to be it, all linear pots exhibit that same characteristic
you described when they are in an audio type circuit. Good luck. Maybe
that's why it's messed up, the last guy could only find a ganged pot
that was a linear taper, and he figured that was good enough.

Negative Feedback Loop on a '65 Super Reverb
I have 65 Super Reverb that I disconnected the negative feedback
on. This seems to give it much more gain, which I desire. Are there any
long or short term side effects to this mod. Also, when turned up
past 6, I hear ghost notes riding on top of the original signal.
Is this because I disconnected the negative feedback loop or do
you think it's just the filter caps. The caps are about 2 years old.
Any help would be greatly appreciated. Thanks
Gary

ANSWER:
No, you really can't hurt anything by disconnecting the negative feedback
loop. It does just what it does as you mentioned. With any modification
to factory originality, one can always experience abnormalities, but I
usually don't hear of that problem associated with the feedback thing.
But who knows, those electrons do crazy things!!

The ghost note thing can be many things. Since your filter caps were
changed just 2 years ago, I really doubt if that's it. A couple
suggestions just to try out:

If you play exclusively in channel two (most everybody does), check to
see if it's prevalent in channel one as well. If so, you pretty much
know it's in the power section. If not, it's in the pre-amp section of
channel 2.

1) Reconnect the feedback loop. Do the ghost notes still appear when
cranked? If they are still there, you know that it's NOTHING to do with
anything you did.

2) Check the cathode bypass (pre-amp tubes) electrolytic caps there (the
little 25uF/25V caps). Original ones leak all the time and might
contribute to it.

3) A coupling cap may be leaking some amount of DC into the circuit. If
you have any chocolate drops, I'd advise changing them to Sprague 715's
or other good quality couplers. Leaky DC causes goofy things to happen.

4) Tubes. Try changing some out, with known good tubes. Isolating the
problem to 'pre' or 'power' amp will help you here.

5) Speakers- sometimes make mechanical noises (even new ones) and can be
heard as a ghost note. Try another speaker cabinet to see if that's it.

Hope that helps. By the way, you have one great amp there. I just love
BFSR's, most especially the '64 with the C10R Jensens!!

Dave Boze

Blackface Mods for Super Reverb
I have an early 70's (71or72) Super Reverb and would like to "blackface"
it. Some companies sell "blackface" kits and high performance cap kits.
Are all silverface amps generic in the sense that one kit will fit all.
Or is there more to it than that. I would like to do this myself instead
of taking to a tech. Any recommendations? Thanks, Mike.

ANSWER:
This is a tough question. The Super Reverb in particular went through
several aberrations, some better then others in the '70's.

The bottom line with Supers is that you really don't know what you have
until you open it up and that will determine what you exactly need to do
to the amp to make it into a Blackface, tone wise.

As long as it has a choke coil (looks like another transformer) you will
be fine.

I have a procedure that I go through to check out all amps thoroughly
and proceed to Blackface them. First off you will need a schematic and
layout of a REAL Blackface Super Reverb model AB763. There are several
sources for this, most notably the Pittman or the Weber Books.

In addition to converting it to BF, you also need to TUNE UP the amp (as
I call it) and install 'up to snuff' filter caps, pre-amp electrolytics,
bias cap, fresh tubes, clean pots, set bias, etc. as well. This is just
as important as the BF'ing.

Really the only truely sure way to BF an amp, you have to go through it
component by component and compare what you have to the AB763 layout and
schematic. ALWAYS BE SURE TO DRAIN ANY FILTER CAP BEFORE STARTING WORK.
Amp voltages can kill you if you don't know what you are doing.

I start underneath the amp, first thing change ALL the filter caps, then
verify that the voltage dropping (2 watt) resistors are the correct
value. They might or might not be. Replace them if either out of spec or
the wrong values. While the amp is turned over, replace the tubes that
need it. Retention all the power tube and rectifier tube sockets.

Flip amp over, replace all the cathode pre-amp electrolytics (25uF@25V),
then start comparing. Most likely you can snip of the .002 caps on the
reverb jack and on the power tubes. Just throw them away. The power
section will for sure need to be rebuilt. The bias cap should be
changed. The bias pot needs rewired. The whole inverter will probably
have the wrong value resistors, check and change them out to proper
values. In the pre-amp section there is probably a couple of WRONG
values resistors, you'll just have to look at the values and see what's
different. Be sure to change the cap that couples between the pre and
power sections. CBS put in a .01, it's way too big, replace it with a
.001uF or .002uF as a maximum value. As I said there are a lot of little
things that all add up.

I'd really advise if you don't know what you are doing to get it to a
good tech and let them do the work. You'll have it done right and it
won't be dangerous for you. There are so many subtle little things that
you have to do, it's really impossible to detail all of them, since I
don't know which version of the amp you have. After all of this, the
bias of the power tubes will need to be set. Don't forget to clean all
the pots and switches and jacks, too, with good contact cleaner. If
there are any of the crummy 'chocolate' drop caps, replace them. I use
Sprague 715 Orange drops. The Chocolate drops are awful.

If your amp has a master volume or the dreaded pull boost, I'd advise
you to disconnect whatever is there for those and convert to exactly as
a BF one is.

I hope this helps. Really, I'd advise you to seek out a tech you trust
and have them do the work, but that's your call. Get a good soldering
iron and be patient.

Dave Boze

Leslie 16

Recently acquired a Leslie 16 which I have no tech. data at all I've determined that it's not a stand alone unit, but is to be used in conjunction with my amp (mesa dc2 studio). Question what about overall impedance Leslie is probably a 4 ohmmer and my mesa has 8, 4, and 4 ohm outputs. Which and why? Please!!!

Hi: David Wilson (ToneQuest) asked me to attempt to answer your question, so here goes....

Ahhhhh, I just LOVE leslies, and actually you are speaking my language, it's the ONLY effect I use. Every Leslie 16 or Fender Vibratone I've had and/or worked on has a huge Oxford 4 ohm speaker. I am the first one to tell you to match the load to the transformer but quite honestly I use mine with just about every amp I own and really can't detect much of a difference, and I've never hurt an Output transformer either.

I would say from a theory perspective, a 4 ohm is the best. I'd put your selector for what is best for your current speaker in the guitar amp. You'll only use it a few times a night, and I'd leave it on what you are going to run your guitar speaker optimally. If you are recording and just driving the leslie, then use "4".

Yes, you are right, it is a stand alone unit. I even have an owner's manual from one, if you need it I can Xerox and mail to you. Doesn't tell you much though about how to use it. You must drive it from whatever guitar amp you are playing. Simply pull the 1/4" plug from your speaker in the amp, replace it with the 1/4" plug that's on the Leslie footswitch, then replug your speaker into the female 1/4" plug that's on the Leslie wiring harness.

One of the footswitch buttons switches between the leslie and the guitar amp speaker (It's like a speaker select switch), the other controls the speed of the rotor, either fast or slow. I personally prefer the slow speed, it's the world's biggest phase shifter that way. Put in on SLOW and play "The Wind Cries Mary", really dreamlike and beautiful!! Then the fast is the Hammond thing.

(djmboze@ameritech.net). BTW, the only difference between a 16 and a Vibratone is that the Vibratone has a crossover module that sends some frequencies back to your amp's speaker when the leslie is activated. What this does is adds an ambience to the sound of the leslie, making up for a lack of a soundwell for lower frequencies. A model 16 sends all the power right to the leslie, instead of dividing it. 16's were for organs, Vibratones made specifically for guitar, but if you mike your 16 on stage, it'll make no dif at all. I have to mike my Vibratone on stage all the time. It just usually won't cut it above the rest of the band on it's own. For big situations, I have a real leslie 145 that has no amp in it and I drive it just like your 16. WOW, a wall of sound!! Having a 15" on the bottom and a top horn rotor, it really gives you some neat frequencies, plus the motors turn opposite each other for some jet plane type effects...too cool!! The slow speed on that thing knocks you right out. Hope that helps.

More Princeton Mod Info

I'm thoroughly enjoying your columns,but i need a little help with your suggested mod to Princeton Reverbs. I own a brown tolex Princeton, without reverb, already fitted it with a 12". Could what you prescribed be done to my model? If so,kindly walk me throught it cause I didn't fully follow your recipe as how to perform these changes,(the match up & the blueprinting in the phase inverter).I had also heard that disableing the tremolo can also add some output to the amp!         I'm not a technician,but know how to identify most things on a schematic,& can safely operate a soldering gun  while sober! thanks,Kenny 

Hi: David Wilson (Tonequest) asked me to attempt this, so here goes....

What I talked about last month is an old trick I got from a guy named Dan Torres. Dan is a guy who takes a lot of HEAT from some people as he can be known to turn some old amps into shread machines, something I don't like or do. BUT........I have found over the years that everybody who's been doing this over the years has some good info to share. I find the PR trick especially wonderful and involves virtually no changes at all to original circuitry, just an upgrading of the quality of some of the components in the power section. Quite honestly, it's fairly detailed and too much for me to type in here. However it can be had one of two ways:

1) Buy Torres Book

2) I have a copy on 11 x 17 from an approx 6 year old Vintage Guitar Magazine.

If you really want to attempt it, or get a copy, if you send me your mailing address, I can get you a copy. HOWEVER having said that I really would NOT recommend you do the work yourself, unless you know what you are doing. There are voltages there that can linger in capacitors and unless you discharge all of them properly, those voltages can kill, even with the amp unplugged. A qualified technician is a way better way to go. You have to be able to have equipment to match components, and to do that you have to stock a lot of parts to be able to test and match, finding the right two that are matched. It gets complex. 

I can match up some components and resell to you, I guess, if you have no other way to do it. Plus the nice thing about this is that if you do the work right, you can always go back to what you had before, no one would ever know anything was disturbed if you solder cleanly. Nobody's gonna care what's been changed once they hear the amp, anyway. 

I have done this one time to a brown Princeton. The customer was very happy with the sound after I did it, it's the same principle as in a BF model. Correct the slight mismatch in the PI, and then match all the power section components up and it really does wonders to the fullness of the tone and adds a bit more volume. Just an enhancement of the great tones already there, NOT A SHRED MACHINE!!!!

On the other hand I've done at least 25 of those on BF and SF Princeton Reverb models and it really makes a big dif

I really cannot give people advice how to tech amps over the net, but can provide guidance as to how things should be properly done. That's why I recommend you get it to a tech who knows this stuff, let him also perform a "tune-up" on the amp at the same time to further enhance everything (tubes, caps, cleaning, etc...)

As for disconnecting the trem, sure it can be done. I usually do not recommend that. It may increase and enhance things a bit, but I love that trem that's in your Princeton. I'd leave it. What some do is put a pull pot on the front and put that disconnect on the pull pot, no drilling required and you can go back to trem if you want it. Again, I personally do NOT recommend that. With the exception of the "mod" I mentioned, I pretty much am a purest. Leo did a pretty good job in the design dept. The reason I don't mind messing with this "mod" is that the Princetons were designed to be a practice amp, very cheap. Putting in high quality stuff would have sacrificed profit on a low end amp. It made no sense business wise. But here we are today, and we can slightly enhance it, by simply putting the "good" parts in.

Ask ToneQuest 

Stumped on the best choices for a new amp? Thinking about a new set of pickups for your favorite Strat? Tired of buying and trading stomp boxes looking for the purrfect overdriven Tone? Got a question about tubes for your '65 Deluxe Reverb? Whatever your question, leave it with us and we'll see what we can do about getting you a definitive answer. Selected questions will be answered in print in future issues of The ToneQuest Report with our thanks.

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