How can I turn a 2 channel Twin amp into a 1 channel Twin ?

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How can I turn a 2 channel Twin amp into a 1 channel Twin ?

Post by dumbangel » Thu May 14, 2009 8:33 am

I love the tone of my Twin Reverb Reissue, but it's unnecessary loud for recording instrument after instrument like I do at home.

I heard one could easily turn this amp into a mono channel amp by removing a few valves and disconnecting 1 of the 2 speakers. Does anyone have more information about this?

Also I never use the reverb/vibrato channels, can I remove any valve that is unnecessary as a result ? Is it bad for the amplifier ?

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Post by asmara » Thu May 14, 2009 8:42 am

The Fender Twin is a fantastic performing amp but I agree completely about recording volume problems. I would say leave it alone and get a nice princeton reverb. The Silverface ones are ridiculously good tone and killer reverb for recording. They will never make it on stage or even in a normal rehearsal but very nice set-up for recording. If you insist on the mod I would give Jeff at Savage Amps a call for some advice.

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Post by Sean Sullivan » Thu May 14, 2009 9:45 am

I'm pretty sure if you take half the power tubes out, you will cut the power in half.

The reverb and vibrato are great, but if you don't use them I suggest a different amplifier. If you don't ever use the vibrato or reverb, get a Fender Princeton (not a Princeton Reverb). They are only about $400.
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Post by themagicmanmdt » Thu May 14, 2009 9:54 am

i take it it's too loud for recording because the 'sweet spot' you hear happens when you turn it up to about 6? twins run pretty clean up to and past halfway on your volume knob.

here's the skinny on the two things to do with the twin:

first - power tubes - the twin operates with two pairs of tubes - if you're looking at the back of the amplifier, and counting from left to right, tube 1 and 2 work together, and tube 3 and 4 work together.

if you want to cut the power in half, pull either tubes 1 and 3 or 2 and 4. they have to be pulled in a pair like this!

what will you get? about a 50w amp. you'll be clean up to about 4 on your input volume.

second - preamp tubes - you mentioned 'disabling' the normal channel. if you pull the preamp tube for that channel (which would be the tiny tube all the way on the right hand side), you're simply drawing less amplifier current and you'll get more headroom and also gain out of your vibrato channel. though, if you're pulling the pair of power tubes, you're going to get this headroom+gain anyways, so I suggest for your purposes to leave that preamp tube in. but, unplug it and listen! you won't harm the amp.

sell the reissue - the princeton is a great small amp - I'd also suggest a super reverb with a master volume -
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Post by sound for sandwiches » Thu May 14, 2009 10:04 am

Just a word of caution to those considering removal of 2 power tubes from a 4 tube amp: this will affect bias as well as output impedance and will cause variations in current draw as well as voltage variations all over the circuit. Twins are pretty robust so you most likely will not have any damage to your output transformer, and you may not even notice any negative effects on tone. But this "trick" can be hard on amps, especially ones that aren't overbuilt in the power stage. Just wanted to point this out.

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Post by standup » Thu May 14, 2009 11:39 am

Could be another case of internet info-mangling. I did a bunch of stuff to a blackface Showman (pretty much the same thing with no reverb) and according to my "research" (google)

-- the tube pairs are the two OUTSIDE tubes vs the two INSIDE tubes. Now I don't know if that's right or if 1+3 and 2+4 are correct, I'm just telling you what I googled up. I pulled the two outside tubes.

-- I read on them internets that this is hard on the transformer, and that putting a 16 ohm load on the amp would help rectify this. It also cuts the power of the amp down some more, so I put a 15" weber on it, 16 ohms.

-- and last, I put in a couple of THD Yellowjackets. These are adapters that let you run the amp off of EL84s instead of 6L6's, cutting the power down again and changing the tone to something a little less clean.

After all this it sounds pretty great, I'm using it at low volumes and it hasn't suffered any problems (except when I pulled it out of the truck and destroyed the fuse holder).

And with all these mods IT'S STILL LOUD AS HELL. I don't think I've needed run it over 4 or 5 on the knob since the mods.

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Post by oldguitars » Thu May 14, 2009 2:26 pm

after doing this, you will realize that it won't be much quieter, just a little less headroom.

Just get a smaller amp...

an attenuator would work too...
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Post by ubertar » Thu May 14, 2009 3:11 pm

Sounds like you'd be better off with a Champ than a Twin.
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Post by Winstontaneous » Thu May 14, 2009 3:56 pm

I've played gigs as a bassist with a guitarist using a 2-tube/1 speaker Silverface Twin--it's still painfully loud. Even when it breaks up it's more of a forceful grit, with none of the sag of a Champ/Princeton/Deluxe/Bassman.

In any case plugging into input 2 on either channel will reduce input gain & let you drive the power tubes a bit hotter at a given volume.

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Post by standup » Thu May 14, 2009 7:25 pm

In my case I have a small amp kicking around too. The showman project was more in the vein of what-if-I-did-this. Then this. And that. It sounds good, I like where it ended up.

Around here people are trying to sell Princetons for $1000 or more. Small amps are great, but sometimes I need a big sound, and the showman is great for that.

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Post by RefD » Thu May 14, 2009 9:16 pm

this is why i record with small amps and gig with large ones.

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Post by jaguarsg » Fri May 15, 2009 1:55 am

sell it and get a deluxe reverb.

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Post by ashcat_lt » Fri May 15, 2009 7:11 am

Wubbeneezer Garibaldi wrote:In any case plugging into input 2 on either channel will reduce input gain & let you drive the power tubes a bit hotter at a given volume.
How's that then? I think you'd ought to examine the schematic, and then re-examine the logic of this statement.

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Post by asmara » Fri May 15, 2009 7:26 am

ashcat_lt wrote:
Wubbeneezer Garibaldi wrote:In any case plugging into input 2 on either channel will reduce input gain & let you drive the power tubes a bit hotter at a given volume.
From my experience input 1 and 2 are equivalent in actual output volume.
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Post by lysander » Fri May 15, 2009 7:27 am

Show me a $400 Princeton and I'll show you a solid state amp.

Twins have great low-volume tone -- what's the problem? Add a Rat pedal and you've got the overdrive.

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