Whydoesn't my Super Reverb clone sound like a Super

[Bob-I]

History...

It started as a Weber kit. I won't go into details but the transaction was less than smooth. I built it using 100% Weber components and it was ok. Very early breakup, not much low end and not really the charactor I was looking for.

To my ears a Super is controllable at less than #3 on the volume, clean, tons of bottom so you have to run the bass control at about 2-3, stays clean and crisp until you get to about 6 then it starts a nice smooth breakup.

My Super clone sounded thin, not enough bottom end, broke up at #2 on the volume and never gave that classic Fender tone.

So I relaced many components. All caps were changed to 6PS ODs of Mallory 150s. Resistors changes to 1 watt xicon CF. Output transformer changed to MM and of course all tubes. I have a selection of JJ's, EH and JAN Phillips 12AT7's as well as Chinese 6L6's on the output. I've tried many.

My impression is the PI is distorting very early. I swapped in a 12AU7 and it's better. I'm thinking the unique preamp is driving things hard, overdriving the PI.

BTW, I swapped the Weber OT back in, it actually sounds better than the MM, go figure.

I swapped out the Weber Signature Alnicos with 2 Fender ceramic's and 2 WHS 10". Again better but not that tight bright Super tone.

So where to look?

Any help is appreciated

[Structo]

That sucks that it's not living up to your expectations.

Just today I was browsing Weber's site looking at his kits.

Certainly seems to have the best prices around even with the included head or combo cabs.

I noticed he mentions that he now includes Carling switches and Neutrik jacks.
I know there was a lot of complaining about some of the smaller parts like that.

Have you compared the schematic you built it from to an actual Fender?

Off topic but isn't Ted ill right now and his son or somebody else minding the store?
I wonder if that has anything to do with some bad reviews lately?

[stoo]

sounds like too much NFB.
Stew'

[billyz]

I am curious, you say you have a unique preamp ? Could that explain the unique sound your getting?
If I were building a clone of a Super Reverb, I would use Carbon Comp resistors and try to source old Blue molded caps or other similar vintage ones. The Mallories are Polyester metalized film, don't remember what the ODS are but some are Polypropylene. Neither of these will give you the Fender tone. I once changed all the caps in a Princeton to ODS and it sounded very high fi like and a bit sterile, I learned my lesson. For modern caps I would try the SOZO's , also, they are coming out with a Blue Molded Cap soon. The Taper on alot of new Pots is not the same as the old fender pots either. I find most come on way too fast. I prefer the PEC pots as the best modern brand and the taper is good . Don't know if they will fit in the Super reverb though. Short of that, CTS or maybe the new Bourns. Try first before assuming they have the right taper though. The best sounding Super Reverb I ever played had Jensen c10n speakers, but another one sounded almost as good with the later dark brown frame Alnico mags( and much lighter. They might have been CTS speakers. They need to be broken in before the bass comes around .

Good luck.

[Darkbluemurder]

To my ears a Super is controllable at less than #3 on the volume, clean, tons of bottom so you have to run the bass control at about 2-3, stays clean and crisp until you get to about 6 then it starts a nice smooth breakup.

My Super clone sounded thin, not enough bottom end, broke up at #2 on the volume and never gave that classic Fender tone.

My impression is the PI is distorting very early. I swapped in a 12AU7 and it's better. I'm thinking the unique preamp is driving things hard, overdriving the PI.

Any help is appreciated

Bob,

Since you are much more experienced than I am (I only built 2 amps so far) you probably have tested everything but is the tail resistor really 22k and not 2k2? A 2k2 would make the PI distort.

I know it sounds weird but I once wired a 470k PI cathode resistor instead of a 470R and of course wondered why the amp lost all of its volume.

And I also guess that the feedback values are 820R and 100R to ground (and not 820k).

Can you please describe the unique preamp? That would be a departure from a Super clone, wouldn't it?

Cheers Stephan

[Andy Le Blanc]

I've a nice old super in the shop, You cant really account for 40 years of use.
No matter what you've been led to believe. Turn it on, and leave it on for a
week, or two. Take it out to a few really loud jams and pound the crap out of it.
leave in the back of a truck and go four wheeling, bring it home and
share a few beers with it. Then check the bias.

[Bob-I]

Thx everyone.

A Few comments. The AB763 is a unique animal, lots of stages between reverb, return, trem etc so that's what I was talking about with unique. Lots of stuff to go wrong.

I'll double check all the resistor values, I'm colorblind so mistakes are very possible.

I agree that different caps can make a big tonal difference, but the gain structure seems off, way too much swing going into the PI (I think)

Too MUCH NFB? I was thinking too little. I'll put a pot in and tweak.

Pot taper may be an issue but I've measured and it seems about right.

I agree that amps need a burn in time, but it seems to be going backwards. More breakup at lower volumes over time. I want that CLEAN Fender tone. Compared to a brand new re-issue it breaks up way too early and has way less girth to the tone.

[billyz]

Since you are color blind ( so is my brother -in-law) You will have to extremely careful to measure every value. Super reverbs have quite a bit of negative feedback, stock. But , even more will kill your amps tone. 820/100 or 8 to 1 ratio is more than most already. for example a vintage marshall with 100k/5k would be 20 to 1 ratio.
What OT are you using? If you come off the wrong secondary it will change the ratio further. I think you want the 2 ohm tap. and the tail resistor from 22k to say 2.2k would be dramatic as well.

Pot taper on audio pots is very hard to measure meaningfully , you can hear it better than you can measure it.

Keep at it and good luck.

Pics would be good too, maybe someone with sharp eyes will see something useful ( not me ).

[billyz]

Just out of curiosity, What are you biasing your tubes at ? 25-35 ma should be good.

[jaysg]

Can you determine the clean output power? I'd be suspicious of the PT until proven otherwise.

[Bob-I]

Thx.

Yes, I'm biased at 33ma, dual bias controls and checked for PI balance. I've gone all the way from 25ma to 45ma and I like 33 best.

I've tried 2 OT's but the same PT. The Weber OT has 2 4 and 8 ohm taps. I've tried rewiring the cab for 8 ohms and switching the tap. The NFB is off the 2 ohm tab so the ratio is not what you think it is. I dropped down to a 50ohm shunt so the NFB is about 6.4 closed loop gain. The Marshall would be ~10

I haven't measure clean output power. I think the next step will be to check that, and also look more closely at where the distortion starts. I suspect the PI by the sound of it, but I haven't really checked.

[M Fowler]

I used to have a nice silverface super reverb but then I made a mistake and had Dan Torres make it into a Super Texan and the amp sounds like crap now.

I think I will get some new trannies and rework the old amp back to better than stock condition, without Dan's gain channel and effects loop.

Mark

[Structo]

Is it true that you can check for PI balance on the plates by measuring with your meter set to AC volts?

So when it reads 0 the two halves are balanced?

[Bob-I]

Is it true that you can check for PI balance on the plates by measuring with your meter set to AC volts?

So when it reads 0 the two halves are balanced?

I really don't know about that method. I use a scope.

Apparently there's something off in the reverb ckt as the signal out looks nothing like the signal in. Unfortunately my cheepy sine wave generator is flaky, I can't get a sine wave.

[Firestorm]

I've seen a lot of Supers and I've never seen two that sounded exactly the same. Still, yours sounds like there's a serious voltage issue (AC or DC). Get the "Normal" channel right; then the "Vibrato" channel should be easier.