77 twin reverb

[majwild1]

I have a couple of 77 twins yes the ultralinear I am going to retube one of them for my boy it has groove tube 12ax7's and mullard at7's, ruby tube 6l6gcm-str power tubes I was checking out tubestores tube chart, now I'm not sure if you've ever played with the ultra linear twin or not but what if I dropped in some 5751 or ran all 12at7's I know it would drop the gain down but what do you think it would do to the tone of the amp? he wants to mellow the amp down a little. Any advice would be helpful. Just decided to go with the jan phillips 5751,and getting some phillips 6l6gc's my buddy had some extras tried them out big difference

[phantomman]

I have a couple of 77 twins yes the ultralinear I am going to retube one of them for my boy it has groove tube 12ax7's and mullard at7's, ruby tube 6l6gcm-str power tubes I was checking out tubestores tube chart, now I'm not sure if you've ever played with the ultra linear twin or not but what if I dropped in some 5751 or ran all 12at7's I know it would drop the gain down but what do you think it would do to the tone of the amp? he wants to mellow the amp down a little. Any advice would be helpful. Just decided to go with the jan phillips 5751,and getting some phillips 6l6gc's my buddy had some extras tried them out big difference

The 135-watt UL Twin is basically a real loud, real clean amp -- period. If by "mellowing the amp down" you mean re-tubing it for more grunt and compression at lower volumes, you're pretty much outta luck. You can try a power brake (attenuator) or the TAD EL84 power tube adapters -- they might git you somewhere (as might the 5751 substitution in the V1 and V2 positions). But subbing the output stage with small-bottle tubes will cost you most of the traditional Fender tone. And even using a power brake will not give you the same type of break-up and compression as say a Supah Reverb or a Bassman.

I basically use my '78 model as a linear power amp and rely on outboard effects to create the tones and voicings I need for a given toon. I dime the master volume and keep the pre-amp down around 2 or 2½. depending upon the size of the venue.

HTH

[majwild1]

Hey phantom, have you ever used the phillips 6l6's in any of your and the balance control did you change yours over to a true bias circuit?

[phantomman]

No to both questions. Stock "balance" bias adjust and JAN Tung-Sols. My other Twin (BF re-issue type) came with Groove Tubes which I promptly hook-shot into the nearest dumpster and replaced with Mullards. I hate them GTs......(one more FMIC marketing gimmick).

[majwild1]

I just shot you a email. But thanks for the info, Aren't gt's just renamed sovtek tubes? By the way was going to ask you are you down by Nogales?

[Kap'n]

I just shot you a email. But thanks for the info, Aren't gt's just renamed sovtek tubes?

Or Chinese, or what have you, for the most part.

GT matches a bunch of tubes, and usually weeds out the really bad ones. For that, they charge you an arm and two legs. But don't worry, the "GT mojo" and orange paint will make everything sound magical.


At least they're not worse than the identical tubes you can buy at 1/3 the cost.

[phantomman]

At least they're not worse than the identical tubes you can buy at 1/3 the cost.

LMFAO!!!

[majwild1]

Or Chinese, or what have you, for the most part.

GT matches a bunch of tubes, and usually weeds out the really bad ones. For that, they charge you an arm and two legs. But don't worry, the "GT mojo" and orange paint will make everything sound magical.


At least they're not worse than the identical tubes you can buy at 1/3 the cost.

Well, Kapn I do say I like your sense of humor LMAO

[majwild1]

Hey NT, Just curious if this is going to mess up this amp at all I was talking to a buddy and he said to put a 12ax7 in the phase inverter to help it break up a little earlier at lower volumes, by god if it didn't work, I'm just curious if this would effect anything seeing that it's looking for the 12at7 and being mis biased in the at7 circuit.

[Wilko]

I've got one of these amps. It has a pull "boost" and a master volume. It's actually very versatile.

You can do those tube value changes and a very simple NFB mod that helps get a more natural overdrive.

They do take pedals well, and with a blend of master volume and a little pedal, you can get a real nice sound with them. They have so much power that there is always plenty of "grunt" on reserve. Great for "thud" on palm muted stuff.

It's got a SS rectifier and way too much power, so the clean sound is great, but not as "fat" sounding as some of the other popular Fender amps like the Deluxe, Pro, Vibrolux, or Super. Where these really shine is the louder stuff where you get that oomph and clarity.

[majwild1]

wilco, were can I find this mod?

[NTBluesGuitar]

Hey NT, Just curious if this is going to mess up this amp at all I was talking to a buddy and he said to put a 12ax7 in the phase inverter to help it break up a little earlier at lower volumes...

Shouldn't hurt anything. I've seen lots of folks do this. However, with tubes like a 12AZ7 or other odd, low gain tube, the cathode resistor/capacitor needs adjusting.

You're feeding it a bit more gain from the preamp to the power amp n your case. It may sound harsh when the volume steps up though. Or it may not.

[majwild1]

so basically the nfb mod is just clipping the smaller wire on the speaker jack and taping it off? wilko what did you do in your amp ad a pot, switch, or just tape it off?

[Wilko]

I used a pot and put it in the extra speaker jack location.

[majwild1]

Is there somewhere I can find a schematic of the mod, or is it something I should take in.

[Wilko]

It's a pretty subtle thing. It's not really neccesary as the amp already has a master volume.

Just put the master on about 2-3 and dial in some dirt with the channel volume.

[majwild1]

Thanks wilco , I had sent nt a pick of the inside of the amp and it looks like the mod has already been done, I did put in new 12ax7's in plus one in the phase inverter gave it nice breakup at lower volumes ( I can take out my ear plugs now LOL.) I'm going to post a pic of the inside see if you can figure out what they did.



http://c1.ac-images.myspacecdn.com/i...db2b9e02ac.jpg


It looks like the green and yellow wire from the output trans has been moved to the resistors for the NF the the white wire come of the same terminal and goes back to the speaker jack. the bottom link is a bigger pic.

[yankeerob]

You're feeding it a bit more gain from the preamp to the power amp n your case. It may sound harsh when the volume steps up though. Or it may not.

Good call Teej, I'll guarantee harshness if yer stickin' higher gain bottles where they don't belong... 'specially if it's a Fender... I mess around more with dropping gain in stages than bumping 'em up and have found good 12AY's and AT/ECC81's worth their weight in gold for makin' an amp sweeter... the way to aproach the 135W UL is to see it for what it is - an amp that was designed not to distort - get it sounding good clean and deep and then stick a good pedal in front of it - save the pennies you might spend on tube adapters and attenuators and buy some decent pedals - I wasn't big on pedals but I bought a Black Star DS-2 and it works with my bassman clone - which now does 57W RMS with KT-77's in for big gigs - and brings out interesting surprises when I stick it in front of my three smaller amps - find one that works for you with that UL platform - or get someone to stick it in a head cab and use it as a bass amp - I knew a guy who used a SF Dual Showman head with a coupla 2x15 Sunn cabs and that rig drove that band considerin' the guitarists had a HiWatt/4x12 and a Twin respectively...

[majwild1]

Well I found a goody today, I found this at family estate sale, My boy just about fell of his rocker when he seen it. The people were selling most of their stuff and moving to AZ. elderly couple I kinda feel bad for getting it so cheap but they didn't even know if it worked, it was there sons who passed away in Nam. $300.00

[phantomman]

BE STILL MY BEETING HEART!!!

[Wilko]

I'll be dipped in...

Dayum! That's the grail amp right there. No need to look any further.

[Wilko]

Oh, It' looks to be modified.. at least the power tubes... Are those 6L6?

And the rect is either gone or replaced by SS inside. Typical mods in the 70s.

[Kap'n]

Oh, It' looks to be modified.. at least the power tubes... Are those 6L6?

And the rect is either gone or replaced by SS inside. Typical mods in the 70s.

That's what it looks like to me. If it's working, he's got diodes soldered across the socket.

Nice score!

[majwild1]

They're 6550 tubes in it, I'm going to open it up in a few put in on the table and see if she works, I'll take some pics of the inside also.

[Wilko]

6550 are basically 6L6s.

[Kap'n]

6550 are basically 6L6s.

But with a lot more filament current requirements - 0.7A per tube.

Stick a quad in there, and you're stressing the filament winding by nearly 3A.

Bad idea.

[NTBluesGuitar]

Dayum! That's the grail amp right there. No need to look any further.

I concur!

I'd love to see some gut shots of that guy if you get a chance!