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6G15 vs. RI w/mods

11/26/2000 4:32 AM
Dave Waller
6G15 vs. RI w/mods
Hey all,  
I just got though doing a minor repair on a friends '64 6G15 Reverb unit. While it was in the house I compared the sound to my RI. As you mihgt guess, NO COMPARISON!!! The original sounded smoother and warmer in all settings without that harsh sound of my RI. The question is: Is it worth trying to get these RI's to sound like the 6G15? Do you have to put in a whole new PTP breadboard, change some vital componets on the PCB, 6K6, or what? I know John Stokes wrote earlier this year about converting his RI w/ a Hoffman kit. All I remember him saying was that it was a bitch. Don't recall if the sonic results were worth the time, cost and effort. Any info to share? Thanks, Dave Waller
11/26/2000 5:15 AM

"I know John Stokes wrote earlier this year about converting his RI w/ a Hoffman kit. All I remember him saying was that it was a bitch. Don't recall if the sonic results were worth the time, cost and effort. Any info to share?"
As I remember J.Stokes really noticed no difference socically betweent the stock RI and the RI w/board kit. The reason I remembered that was it confirmed what I found when I did a side-by-side comparison between a dead stock 65' Reverb unit.  
The only change we made to the 65' was replace the original 6K6 with with a NOS RCA 6K6. I completly retubed mine with NOS 12AX7, 12AT7, and a RCA 6K6. Sat them down and pluged the guitar into the reverb unit into the amp. And just switched the cords back and forth between the two and couldn't hear any difference--the guy I did this with has great ears, way better than mine and he couldn't hear a difference.  
One change I should note on mine. The stock reverb pan mounting was removed and the pan was directly bolted to the front panel of the unit. Don't know why, was that way when I got it. Not sure if the pan is original or not--been meaning to double check the numbers for a couple of years now.  
Anyway, I originally bought it with the full intention of replacing the PCB with a PTP board, but after that comparision I didn't see the need. Remember J.Stokes saying he did the replacement because he was having a problem and didn't want to play with the PCB at all.  
my opinion for what is worth--replace the tubes with some good stock replacements if you haven't already.  
11/27/2000 6:28 PM
Dave Waller

Thanks for all the advice. I have retubed with NOS Amperex bugle boys in the 12AT and AX positions. I guess I need that 6K6 instead of the 6V6. I also have a couple vintage tanks I can try including one of those great folded line tanks made by "beautiful girls under controlled atmospheric conditions in Wisconsin." Never have really noticed that they are superior to any Hammond unit but the label sticker was the greatest in the business.  
Thanks again guys,  
11/26/2000 5:48 AM

Hey Dave,  
Funny thing about reverb units - no two are the same! This is not surprising since there is a lot of electro-mechanical (and mechanical-elecrical) transfer going on inside these things.  
The advice I saw about getting some good NOS tubes is very good, and it will get you close to the original sound. The single discriminating factor I have found between old and new reverb units is the reverb tank itself. The old tanks just seem to have more depth (splash) at deep dwell settings, without the long decay. Obviously, this is a very subjective. What I have noticed is that new tanks seems to have more dwell than old ones, which many times results in mush at deep dwell settings when using reissues. I play surf music, have built my own reverb units, own 60's and 70's reverb units, and kind of know what the hell I am talking about when it comes to reverb Fender-style. NOS tubes will get you most of the way there, but an original reverb tank will take you the rest of the way.  
My advice - in addition to NOS tubes, try different tanks with your reissue. Some of the late 60's and early 70's tanks are just as sweet as the early 60's units. I don't know exactly what you are after, but experiment and have fun! Exchanging tanks is easy and non-invasive, so what could be better? Beg, borrow, and do whatever to try different units in your RI and see what you like. You might be surprised.  
Best of luck in your quest,  
11/26/2000 6:59 PM

What would you recommend as a good reverb tank to use in a 6G15 DIY? I've got no experience with Fender Reverb, as far as owning or building, so I've not looked at, compared, and thought about reverb tanks like I have for other aspects of Fender tube amps. But I digress...  
If I recall correctly, there are 'medium' and 'long' delay reverb tanks. They also come in different sizes, different numbers of sprins, different manufacuturers, I think. What do you think would work well in this circuit?  
Just curious about your (or anyone's) opinion. thanks a lot!  
11/27/2000 7:08 PM

The standard Fender tank (part number 4AB3C1B) is what I recommend and use for Fender reverb units. Even among reverb tanks with the 4AB3C1B number, the characteristics (sound) can and do vary widely. Early and mid-60s tanks seem best for that authentic deep surf reverb and somewhat quick decay. Tanks from the 70s are usually somewhat darker, but a good second choice. Newer tanks are brighter with a longer decay, at least as my experience goes. The tank you will like best will depend on what you play - I want a deep reverb for surf music. Most folks on this board are into overdriven guitar tones, so a deep reverb would only muddy up the sound.  
I have tried some of the other tanks (like the 3-spring), but the sound is not right for me. The important thing is to match the impedances to the circuitry you have as best as you can. There are a ton of old and new Fender tanks out there to try, so try different ones from your friend's amps or wherever and see what you like. Since these things are mechanical as well as electrical, you will never find two that sound exactly the same.  
Here's a link with some Accutronics tank info:  
11/27/2000 7:17 PM
Steve A.

    Just wondering if the reverb springs may fatigue a bit over time, which might be why the older ones sound different to you (with a username like that I would guess that you are a real conneisseur of reverbs!)  
    Maybe there could be a market for NOS reverb springs...?   ;)    
Steve Ahola  
P.S. The transducers use magnets- right? so maybe the older tanks have lost some of their magnetism (just like old pickups).
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