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Thread: 65 ReIssue Super Reverb Midrange Pot change

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    65 ReIssue Super Reverb Midrange Pot change

    Hi Guys,

    I am trying to achieve a particular guitar tone and I believe (might be wrong) this mod may get me closer. I've read that if the stock 10k Fender pot on the midrange control is exchanged for a 25k, the midrange will really come on gangbusters. Can anyone verify this by having done it?
    Can't seem to find anyone on youtube who has.
    Do you know any tricky temporary non-permanent way to do it for a test? The amp is all circuit boards and things are hard to get at. If I have to, I will dive in ... just hoping one of yaz is gonna save me that hastle

    I feel that mod, as well as, finding or winding a pair of really honky/nasally/hollow sounding humbuckers, will get me to my goal. Here is a great example of what I'm trying to achieve; you'll hear it in the first ten seconds - enjoy https://www.youtube.com/watch?v=vdyvPg0c6bI

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by old guy View Post
    if the stock 10k Fender pot on the midrange control is exchanged for a 25k, the midrange will really come on gangbusters. Can anyone verify this by having done it?
    Yes, it works. And as you dial up the midrange you'll find bass & treble pots have less effect on the tone. You could even go 50K, at full whack it more or less bypasses the tone controls. Remember what Mesa did in their first generation Boogie, the lead tone was accomplished by inserting a 47K resistor in series with the mid pot. Honkerooooo-yah!

    Do you know any tricky temporary non-permanent way to do it for a test? The amp is all circuit boards and things are hard to get at. If I have to, I will dive in ... just hoping one of yaz is gonna save me that hastle
    Be prepared to dive in, there's no e-z way thru the pc board experience. You could open 'er up, cut circuit trace to one side of the mid pot (just 2 terminals are used, it's effectively a variable resistor in this circuit), insert a fixed resistor or pot, give it a play & decide whether to commit. Also a good idea to score a replacement pot that will fit on Fender's PC board. Short of replacing the pot, if you find a resistance value that puts you in the tone ballpark, you could leave a fixed resistor bridging the trace you cut to experiment, and the stock pot will leave you some range of adjustment.

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    Bent Member Chuck H's Avatar
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    I just want to add that increasing the mid pot value with stock BF capacitor values will usually (to my ears anyway) increase the LOW mid frequencies too much. The end result adds too much LF to the tone. The 25k pot works much better if the cap values are changed to .022 bass and .022 mid cap values. But then the WHOLE amp sounds different at all settings!?!

    Something you might like is an old Randall/Fender trick that was later used by Dan Torres and then Mesa. An additional cap in parallel to the treble cap in the tone stack. One of my favorite circuits for it's versatility and effectiveness with little drawback. The Randall and Mesa circuits are similar in that they parallel a moderate value cap, say 500pf to 750pf, with the stock 250pf treble cap. The Torres circuit is one Dan calls a Varitone and it uses a rotary switch to choose one of five different cap values up to .01uf. Which is huge and IMO entirely too large. I'd suggest that the mod be put on a switch. Mesa uses a mini toggle and Fender used a push/pull pot. For your amp I'd use the push/pull pot to avoid any hole drilling. Experiment with cap values between 500pf and 2200pf and choose the one that works best for you. This is a mod I think is totally worth doing to almost any BF topology amp that will be played overdriven some of the time.

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    "Never bet your life on somebody else doing their job." SoulFetish's good friend

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

    "Back to the amp. It makes horrible sounds when I play my guitar thru it... because I suck at playing guitar." Mike6158

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    Thanks guys!
    I will be ordering parts Monday for this. Retarded, is the word I choose for doing this, as I already have an exceptional tone combination with my ES-335 and Super Reverb.
    I had that sound of Freddie King in the OP video with 3 other ES335 guitars so I know, it is not the varitone switch. It's either the wood, pickups or speakers and amp.
    I have a little more than just a 'hint' of what I seek by having flipped a magnet for out-of-phase performance on the Seth Lover PAF clones ... it just ain't enough.

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    Bent Member Chuck H's Avatar
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    I may have a bead on what you're saying. Have you tried wiring the pickups in series instead of parallel? With the pickups out of phase it's a very unique sort of sound that hints of a fixed wha pedal.

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    "Never bet your life on somebody else doing their job." SoulFetish's good friend

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

    "Back to the amp. It makes horrible sounds when I play my guitar thru it... because I suck at playing guitar." Mike6158

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    Thanks Leo/Chuck!!
    Although I did not get the half-cocked wah/woody/Mick Ronson, Boston or Freddie King tones I seeked, I did get a TERRIFIC mod accomplished by simply adding 1 10k resistor ... piggy-backing it on top of the existing one attached to the stock 10k pot.

    I hate pedals for anything and this mod takes my BB PreAmp out of my life.

    I now get terrific breakup and a substantial volume boost at 2.5 on my dial as opposed to 4 before which also, cleans up with the guitars volume pot nicely. I'm glad I took your advice for the experiment with gator clips first. Anybody wanna buy a new 25k Fender pot?

    Sadly, the quest for that Freddie King tone continues.

    I've tried a few ES345s with Varitone switches ... they are not the answer.
    I have flipped a magnet in bridge pup and do achieve a wonderful out of phase tone however, it is maybe 20% the tone I seek.
    The GREAT news is - I nailed the tone 101% by trying an LR Baggs Para DI with Mid turned up almost full.
    More great news is I also nailed the tone 101% more by trying my mid 70s Dunlop wahwah ... even better that LR Baggs unit.
    Problem is, Freddie never used those gadgets!

    So here it is ... not being a 'techie', I need to find out how to extract that half cocked wah tone and install it into a pot of some kind and stuff it into my ES335.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Quote Originally Posted by old guy View Post
    I did get a TERRIFIC mod accomplished by simply adding 1 10k resistor ... piggy-backing it on top of the existing one attached to the stock 10k pot..

    I now get terrific breakup and a substantial volume boost at 2.5 on my dial as opposed to 4 before which also, cleans up with the guitars volume pot nicely.
    Are you sure the existing resistor is attached to the stock mid pot? I don't see a resistor in series with the mid pot on the 65 SR schematic. The existing resistor looks like it is the slope resistor (R18 100k). Adding a 10k in parallel means you now have a 9k slope resistor which is very low, probably too low for the input stage to drive without clipping hence the "terrific breakup".

    Click image for larger version. 

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    Last edited by Dave H; 02-15-2017 at 06:13 PM. Reason: added schematic

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Dave H View Post
    Are you sure the existing resistor is attached to the stock mid pot? I don't see a resistor in series with the mid pot on the 65 SR schematic. The existing resistor looks like it is the slope resistor (R18 100k). Adding a 10k in parallel means you now have a 9k slope resistor which is very low, probably too low for the input stage to drive without clipping hence the "terrific breakup".
    I concur with Dave H's observations. But "if the shoe fits..." so what if your improved tone came by way of a misteak? No harm done, no smoke's coming out nor will it. And it's very reversible should you choose to sell the amp in stock condition.

    For other choices in "cocked wah" tones, consider building or having built for you a "Tea Philter" mid boost box:

    https://www.tubesandmore.com/product...ilter-t-filter

    I built one for a customer and he's happy as could be with it.

    Same outfit also sells the circuit board for a standard wah, you could fit that into a box and have a knob to set your favorite frequency. Also consider there were some outlandish mods done even back in the 60's. One of my customers took a wah board, chiseled a space for it and a battery in his LP junior and let the crowd wonder "how the XXXX does he get that sound?" I'm sure others did similarly.

    https://www.tubesandmore.com/product...dunlop-crybaby

    There's also some speakers that have pronounced mid boost character. Some Pyles used to drive me crazy back in 70's & 80's with their r-r-r-r-r tone, you couldn't dial away from it with amp EQ. Who knows, for you that might be just the thing. There's something to keep every ear happy.

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    Quote Originally Posted by Dave H View Post
    Are you sure the existing resistor is attached to the stock mid pot? I don't see a resistor in series with the mid pot on the 65 SR schematic. The existing resistor looks like it is the slope resistor (R18 100k). Adding a 10k in parallel means you now have a 9k slope resistor which is very low, probably too low for the input stage to drive without clipping hence the "terrific breakup".

    Click image for larger version. 

Name:	Fender-65-Super-Reverb-Schematic-1.png 
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    OOoopzz ... my bad. Apologies to Leo. I misread what he said. "leave a fixed resistor bridging the trace" is what he said ... Sorry Leo.

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by old guy View Post
    OOoopzz ... my bad. Apologies to Leo. I misread what he said. "leave a fixed resistor bridging the trace" is what he said ... Sorry Leo.
    No worries, if you got a tone you love that's what counts.

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    Quote Originally Posted by Leo_Gnardo View Post
    I concur with Dave H's observations. But "if the shoe fits..." so what if your improved tone came by way of a misteak? No harm done, no smoke's coming out nor will it. And it's very reversible should you choose to sell the amp in stock condition.

    For other choices in "cocked wah" tones, consider building or having built for you a "Tea Philter" mid boost box:

    https://www.tubesandmore.com/product...ilter-t-filter

    I built one for a customer and he's happy as could be with it.

    Same outfit also sells the circuit board for a standard wah, you could fit that into a box and have a knob to set your favorite frequency. Also consider there were some outlandish mods done even back in the 60's. One of my customers took a wah board, chiseled a space for it and a battery in his LP junior and let the crowd wonder "how the XXXX does he get that sound?" I'm sure others did similarly.

    https://www.tubesandmore.com/product...dunlop-crybaby

    There's also some speakers that have pronounced mid boost character. Some Pyles used to drive me crazy back in 70's & 80's with their r-r-r-r-r tone, you couldn't dial away from it with amp EQ. Who knows, for you that might be just the thing. There's something to keep every ear happy.
    Yeah ... I've been looking for a quad set of Pyles for many years now. Mine may be too efficient.
    Thanks for the stomp box idea but, I can't handle footpedals or any kind of outboard gear. I will set my mind to somehow extracting that tone out of my wahwah and stuffing it into a Varitone style switch. It is only the one tone ... no need for variable. Bypass and On is the only function I need.

    Do you guys think I'm causing any damage or future malfunction by having my 'new' mod?
    Leo, I'm not experienced enough to cut a trace so when I tried what I eventually did, I jumped out of my skin and back again.
    Thanks.

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    Quote Originally Posted by Dave H View Post
    Are you sure the existing resistor is attached to the stock mid pot? I don't see a resistor in series with the mid pot on the 65 SR schematic. The existing resistor looks like it is the slope resistor (R18 100k). Adding a 10k in parallel means you now have a 9k slope resistor which is very low, probably too low for the input stage to drive without clipping hence the "terrific breakup".

    Click image for larger version. 

Name:	Fender-65-Super-Reverb-Schematic-1.png 
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    Hey Dave ... thanks for bringing that to my attention - something I need to pay more of! Will this 'clipping' cause problems in 4 hours of operation? Will under powering the 'input stage' have any adverse effect? There is no extra hum or anything to indicate a problem to the ears.

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by old guy View Post
    Leo, I'm not experienced enough to cut a trace so when I tried what I eventually did, I jumped out of my skin and back again.
    HAH! but you got something out of it, all to the better.

    A guitar tech could mount a wah board inside your guitar, you'd need a battery to run it. Would be a good idea to have a trimpot to set the boost frequency, park the trimpot where it sounds best to you, then mount whatever kind of switch you like in the varitone position to select your boost on or off.

    Might have to snoop out old Pyles. I've heard recently made 10" Pyles and they don't have that mid peak.

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    Quote Originally Posted by old guy View Post
    Will this 'clipping' cause problems in 4 hours of operation? Will under powering the 'input stage' have any adverse effect?
    No, it will be fine as Leo said. If it sounds good and there's no smoke it is good.

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    Quote Originally Posted by Leo_Gnardo View Post
    HAH! but you got something out of it, all to the better.

    A guitar tech could mount a wah board inside your guitar, you'd need a battery to run it. Would be a good idea to have a trimpot to set the boost frequency, park the trimpot where it sounds best to you, then mount whatever kind of switch you like in the varitone position to select your boost on or off.

    Might have to snoop out old Pyles. I've heard recently made 10" Pyles and they don't have that mid peak.
    Hey Leo ... back in the late 60s, when the world changed, when we'd blow speakers, we'd just go across the Detroit River to Windsor Ontario and buy a brand of speaker called Radio Speakers of Canada (RSC). They were absolutely awesome, inexpensive replacements. Buy today's standards they were junk yet if they came back today, I have no doubt they'd be the rage again for rock 'n rollers. I ran 4 - 15" for guitar. Check out the pic. Mine's the Gibson Black Beauty.
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    Quote Originally Posted by old guy View Post
    I ran 4 - 15" for guitar. Check out the pic. Mine's the Gibson Black Beauty.
    4 x 15s! That would get your flairs flapping.

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    Old Timer Leo_Gnardo's Avatar
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    Some band! "The Public Utility Commission" hm, why not, there was Chicago Transit Authority, and Pacific Gas & Electric. Whatever happened to those kool speakers? In recent years maybe this will explain:

    Mysterious noise escalates in Windsor, Ont. - Windsor - CBC News

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    Don't forget the joker g1's Avatar
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    Ok, looking at that picture I think I can see where the problem may be. Look back at the video you linked in the first post.
    Clearly you have your strap on the wrong shoulder for that Freddie tone.
    j/k, here's another version from the show Freddie did with Grand Funk in '72. (Your afro reminded me of Don Brewer)

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    I don't know if there's a 25K that will fit, but there's a 50K reverse audio, part number 0037602000. Of course you forget the PC mount, put a 16mm in the panel, and connect the pot to the PCB with leads.

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