Why do my Deluxe Reverb and Twin Reverb sound so different?

[stratcat62]

The Twin can't achieve the same clarity, sparkle, and overall desirable tone that my DRRI can. The cleans on the Twin don't even approach those on the Deluxe. With a clean boost in front of the Deluxe I'm getting serious 'Texas Flood' tone (Like "Lenny" clean and clear). Why wouldn't the Twin be able to produce the same clarity as the Deluxe? Is it all in the power amp or are the pre-amp circuits fairly different?

[Alexo]

Are these amps using the same types of speakers? Might want to plug the drri into the twin's speakers, just to eliminate that variable and boil it down to the amps themselves.

Strictly speaking, the only real differences between these two amps are that one uses a pair of 6V6's while the other uses a quad of 6L6's - not an insignificant difference - and the deluxe uses less negative feedback and has a fixed mid control (set on about "7"). But that's about it.

But if they're using different speakers, that's your #1 suspect.

[Colossal]

Stratcat, have you tried swapping the same preamp and PI tube set from your DRRI to your Twin and back (in the same order)? Just wondering if your Twin has a not-so-sparkly tube in the lineup.

Barring that, like Alexo said, maybe it's the speakers. This is a really great question as I've been wondering about the qualitative differences between these amps since they're both the AB763 circuit with different power tubes (and a bit more headroom on the Twin right?). Eric Johnson has used a pair of both Twins and I think Deluxe Reverbs in stereo for his clean setup (or maybe they were Vibroluxes...). I'm really interested which of the two amps might give the lushest clean and sparkle.

[Structo]

This is a diagram of EJ's rig a few years back in 2001.

[stratcat62]

I'm using both amplifiers through the same speaker/speakers which makes the difference even more pronounced than with the stock speaker in the Deluxe. I'm using Eminence Delta Pro-12As with the Twin and Deluxe. The Deluxe Reverb sounds amazing through the Delta Pro.

I've tried swapping all the tubes between the two amps. I've had my better set in my Twin, but the tone isn't the same. Would a difference in the amount of negative feedback have an effect like that?

[Structo]

You also have to consider the tolerance of components which could vary as much as 20%.

Some amps just come together right with the right combination of parts and tolerances.

Kind of like car engines back in the 60's. I had a Chevelle that I put a rebuilt 283 in.
I had the balance checked on the crank and it was perfect.
That engine ran so smooth and had tons of horse power for a small V8.


Consider yourself lucky that you at least have one exceptional amp.

[ampdoc1]

"Some amps just come together right with the right combination of parts and tolerances."

I did amp repairs full time for 10 years, and probably worked on at least a thousand tube amps in that time. One Fender I worked on I tried the usual fixes (new filter caps, replacement of coupling and cathode caps, etc). Nothing I tried would bring that amp to "life". My thinking finally oriented with the statement above.

ampdoc1

[Zippy]

Not all "Twins" sound the same - even if they are all loud. Which one do you have?

[jaysg]

Not all "Twins" sound the same - even if they are all loud. Which one do you have?

and any chance it's been modified? Smells like tonestack caps and missing 10pF.

[wscrane]

Since rp and mu vary between tubes and with signal level, combinations of tubes never give the full output you expect on paper. I way prefer the clean of a Twin to a Deluxe. The two speakers are a big factor but the more complex output stage definitely adds some "tubey-ness."

A funny thing about this is that I've read articles where people caution against hooking two amps to the same cab, but thats exactly what you're doing when you put tubes in parallel.

[Alexo]

A funny thing about this is that I've read articles where people caution against hooking two amps to the same cab, but thats exactly what you're doing when you put tubes in parallel.

Not exactly...

An OT with an "8 ohm tap" wants to see an 8 ohm load, but that tap usually has an actual secondary z of maybe one or two ohms. So if you hook another OT in there, this second OT will not see an 8 ohm cab in parallel with an 8 ohm OT, it'll see 8 ohms in parallel with one or two ohms, and the same applies to the other OT, so the loads will be wayy off. Not to mention, who knows what kinds of crazy interactions you'll get when one amp's OT is being used as an reverse input transformer since the signal from amp number 2 will be gained up and fed to the plates of amp 1 and vice versa. Not a good idea.

[jelle]

What twin do you have? The UL 135W with NFB connected is very dull IMHO.

Also OT's vary a lot.

jelle

[stratcat62]

It's a 1970 that's been blackfaced back to AB763 spec. I've got two Delta Pro 12As in the Twin's cabinet wired for 4 ohms. When I use the Deluxe, I unwire one of the speakers and plug the wired speaker into the Deluxe. I wanted to replace the stock Jensen with a Delta Pro, but the choke is the in the way of where the speaker would be. Do I have any other options speaker wise? The EVM12L seems equally large. It sounds so good that I really don't want a different speaker, but I'd like to not have to bring the Twin to practices and gigs strictly as a cabinet (it's a bit heavy for a cabinet).

[skeezbo]

The Deluxe Reverb has a small bright cap permanently wired on the volume pot, doesn't it? I am at work (lunch break) and I can't look up the value, but I think it is smaller than the one on the Twin Reverb bright switch. This could certainly cause a difference in clarity and sparkle, especially if the bright switch in the Twin is off.

Skeezbo

[jelle]

What kind of twin was it before it was modded and were the UL transformers replaced as part of the Blackface mod? Otherwise your amp is stuck somewhere between BF and SF...I suppose a lot of them are.

The Bright cap is 47pf in the Deluxe Reverb BTW. Twin has a 120pf. Of course the caps are ceramic so who knows the actual value unless measured. Same goes for the 250pf cap in the TSC and the 10pf cap across the Reverb mixer resistor.

Other difference is the NFB. This is very different between the amps as is the behavior and input sensitivity of the different powertubes.

What are the voltages on v1 in both amps?

Also if the amps came from different eras of fender production, the type of materials used, caps resistors etc is different. Gut shots?

jelle