What Gives a Twin Reverb Its Sound?

[trber]

Background: I recently bought a 1969 Twin from the original owner and IDd it as an AC568 circuit with the help of responders on this forum. I replaced the filter and bypass capacitors and a 2.2k resistor in the dog house that had drifted. Someone previously removed the large cathode resistors on the power tubes and the capacitors and wiring that were part of the bias circuit on the chassis side wall. Otherwise, it's stock with Oxford speakers and RCA 6l6gc that may be on their way out. I am hoping to get them tested this weekend. Preamp tubes are a mix of vintage and Groove Tube 12ax7s, I believe.

Question: What gives these amps their sound characteristics?

I am a low watt amp, home player. I normally play a Silverface Champ through a 2x12 cab or a Princeton 10" kit thought the cab and a 12" extension cab, so I am familiar with multiple speaker amp set-ups. Because of hearing sensitivity, I can't get on with high wattage, loud amps. So, I am not referring to the sound of an opened-up Twin moving lots of air and getting the amp and tubes in the sweet spot.

I am asking about the full, deep, rich and broad sound that comes from this amp at around 2-2.5 on the volume. It's like no other amp I've heard before. Maybe it's like other large size and wattage Fender amps: Supers, etc. but I have not played those. Once, in a Vintage Guitar and Amp store in LA, I heard someone play what I thought was a Blackface Deluxe or maybe Twin and it was amazing: similar low volume sonic bliss.

So, what is it? Tubes (large 6l6), transformers, speakers, cab, circuit, some combination of these things?

This amp has really reset my expectations and desires for what tube amps can be.

Thanks for any feedback!

 

[Boreas]

I don't know much about the electronics, but pure POWER gives any amp testicles and authority at any given level.

 

[trber]

I don't know much about the electronics, but pure POWER gives any amp testicles and authority at any given level.

I actually thought about that, but with the few high watt amps I have played, they were just loud, not as detailed, but that may be down to context, etc.

Thanks for the comment! I'll check into this more.

 

[Jasonpatrick]

I don't know much about the electronics, but pure POWER gives any amp testicles and authority at any given level.

That giant output transformer is definitely one of the testicles

 

[Phrygian77]

The TR allows you to get the bass level up more than other amps. The TR also has a mid control, and most people don't realize that you have to crank it to about 8 to get the same level of mids as the non-mid control Fenders, so you get more mid scoop. BF/SF Champs and Vibro Champs have a 15k mid resistor, so they have even more mids.

 

[trber]

The TR allows you to get the bass level up more than other amps. The TR also has a mid control, and most people don't realize that you have to crank it to about 8 to get the same level of mids as the non-mid control Fenders, so you get more mid scoop. BF/SF Champs and Vibro Champs have a 15k mid resistor, so they have even more mids.

Ah, thanks for comment on the mids! I actually saw a video noting the mids on a TR compared to a Deluxe and that's exactly what was discussed...the effect of the mid pot in relation to the non-mid control Fenders. So, is the mids, the bass, and the large single testicle the source of the sound?

 

[Blue Bill]

I think the two side-by-side speakers contributes to the character of the sound. I figure it's just a very well-designed amplifier circuit. It's always been my favorite amp.

 

[Boreas]

I actually thought about that, but with the few high watt amps I have played, they were just loud, not as detailed, but that may be down to context, etc.

Thanks for the comment! I'll check into this more.

Indeed - the details are in the guts, not the testicles. I have had "high power" solid state amps that certainly did not have the nuance. Hot, glowing tubes are responsible for much of that!

 

[Boreas]

I think the two side-by-side speakers contributes to the character of the sound. I figure it's just a very well-designed amplifier circuit. It's always been my favorite amp.

Don't forget the legs! Tilting any amp gives it a great deal of definition.

 

[corliss1]

Amp sound, of any amp, is always preamp and speakers.

 

[trber]

I think the two side-by-side speakers contributes to the character of the sound. I figure it's just a very well-designed amplifier circuit. It's always been my favorite amp.

Well, as a Jerry fan, that makes sense!

The Twin new to me, but I have to say, I'm really liking it. Maybe this amp is unique in the greater world of amplifiers, and I just learned this important fact. Lol.

I have other multi speaker set-ups, and that alone does not seem to be the single factor...

So far, it's the transformer, speakers, mids and bass that make a Twin!

 

[trber]

Don't forget the legs! Tilting any amp gives it a great deal of definition.

I have not even returned the chassis to the cab yet, so I am looking forward to trying the legs! I am hoping that using them to redirect the sound a bit will take the edge off for me and make it more likely I'll keep the amp. It's a bit loud for me right now. I'm definitely looking forward to trying that, thanks!

 

[trber]

Amp sound, of any amp, is always preamp and speakers.

No arguing that! I wonder, do you think the pre-amp, tubes and circuit in a Twin, are unique? These Oxford speakers are not particularly highly regarded, I believe. Far less attention that I've seen compared to the JBLs that are sometime found in these year Twins.

 

[Boreas]

I have not even returned the chassis to the cab yet, so I am looking forward to trying the legs! I am hoping that using them to redirect the sound a bit will take the edge off for me and make it more likely I'll keep the amp. It's a bit loud for me right now. I'm definitely looking forward to trying that, thanks!

I would say if you can LIFT it, keep it! They aren't making those old ones any more. You could consider an attenuator, but I believe that would be sacrilege.

They are certainly not the best all-round amp. They were designed for stage work (where they excel) and cutting through a mix, and that is about it.

What would Jerry do?? If you keep it, embrace the testicles!

 

[DugT]

Do you mean plugged in or unplugged?

 

[glenlivet]

I always thought it was the 2 12's that just filled up the space.

 

[Ronkirn]

I don't know much about the electronics, but pure POWER gives any amp testicles and authority at any given level.

this is pretty much the basis for quality sound in ANY audio system... The momentary transients can consume huge amounts of power for very brief intervals.. if the amp doesn't have it.. something is lost.. and that's Dynamic range..

Few realize that at Normal listening levels.. the audio source will only consume a few watts of power, but the clash of cymbals, or a loud crescendo can increase that by several orders of magnitude.. the ability to accommodate such is known as "Headroom" ya either gottit or ya don't..

 

[Chiogtr4x]

No arguing that! I wonder, do you think the pre-amp, tubes and circuit in a Twin, are unique? These Oxford speakers are not particularly highly regarded, I believe. Far less attention that I've seen compared to the JBLs that are sometime found in these year Twins.

I don't know if unique, so much as desirable?
I know Jerry Garcia ( say from mid '70's > ON) ran only the Twin Reverb's preamp ( 2 TR chassis, vertically in a cab, one was a backup) into SS Power Amps and JBL cabs.

( I know not everyone likes Jerry's playing/tone, or big clean Fender tones, you can use stand-alone, or manipulate w/OD's- but I do!)

 

[TelZilla]

There’s no one thing of course, but I think size and type of speaker(s) as well as broken-inness (broked-inness?) and the cab situation have a gigantic impact.

If you play d a deluxe reverb head through a huge 2x12 Twin cab, I bet it would sound a lot like a twin.

 

[trber]

I always thought it was the 2 12's that just filled up the space.

You might be right, but my other multi-speaker set-ups don't fill the space in the same way, at all...I think there's something(s) else going on here. Whatever it is, it's pretty cool.