blackface kit recommendations: twin or super reverb

[Roe]

I'll try to take pics when I'm done tweaking
also, I'll try to compare the neos to the real deal once the neos are broken in. but already now it seems clear that the neos have that jbl vibe, much more so than the california

[Flames1950]

Not sure if I would get blocking distortion in the reverb circuit or not; by the time I crack the reverb knob up to 1-2 it's as much reverb as I can stand anyway. If I could stand it any higher I bet it will drive things way too hard. That's why I have a dual pot sitting out to put in, to act as a voltage divider/extra grid resistance going into the reverb at V2. May also have to consider less resistance to ground at the V3a input and output where the signal joins back in with the dry signal. (That's relative to this build, where V2 is the paralleled 12AT7 reverb driver, and V3 is the 7025/12AX7 reverb recovery/gain stage after mixing.)

It is minimalistic -- I wasn't interested in two channels or the tremolo for this (especially since it loads the signal down and "deadens" it to my ears -- I have a BYOC Tremolo pedal if I want it) and I wanted a smoother overdrive character than a blackface Fender typically gives. The preamp's two stages and tone control values are stock AB763-and-later Twin Reverb. The reverb started as stock AB763 but we've already established that it will change some to my tastes! The phase inverter and power amp are pretty much the 6G6-A Twin values, with 820 and 6.8K for the PI cathode and tail. I think I ended up at a 33K feedback resistor instead of 56K, going to the old 5K presence pot instead of the 22K pot/4700K resistor that the 6G6-A used (funny how Fender had that figured out almost a decade-and-a-half before Marshall......) I used a 150pF bright cap over the volume with no switch to remove it either.

It's directly based off a Bruno Cowtipper that forum member "Joruke" sent me to mod. You've never heard such a lifeless $3000 USD amplifier as that Bruno was, and after I made some other changes it was "Joruke's" idea to try the blonde power section -- I actually balked at the idea at first!!! He was right on the money with that combination, and I found myself missing that amp when it went back to him, so this is the result.

I'm really happy with how well it moves into overdrive at higher volume settings, much smoother than any Twin Reverb I've had around and totally appropriate for a lot of classic rock and blues gigs -- but at too high a volume of course!! (Maybe I should have based it on a 50 watt Pro Reverb instead?)

These are the Magnetic Components "ClassicTone" trannies by the way, and I'm really pleased with their tone. Plus being able to select the impedance for a variety of speaker cabs makes it more flexible than a typical Fender too.

[Roe]

yes, the vibrato circuit loads down the signal but you get a push pull rev pot so that you can cut the ground connection of the vibrato circuit. another trick is to use a 25k/50kA/100kA mid pot

[Flames1950]

Sure....if I'd cared about the tremolo anyway. But I rarely use it so I just couldn't bring myself to worry about it.

[Roe]

I see personally I like the blackface tremolo although I mainly use it the few times I play with my country/psychedelica band

premature pics
http://folk.ntnu.no/roef/twincab
http://folk.ntnu.no/roef/twinguts

[myfoot]

heh heh, may have to use that Loud/Quiet on my AA as well

[Flames1950]

You've got an extra tube off to the side. Do you have plans for a "boost" channel in place of the Normal channel?

[Roe]

yeah, I'll try to make a switchable boost on the normal channel. but the amp almost breaks up enough already. original plan was 6g6b bass channel. will try some different circuits

after experimenting with voltages, I come to the following results:
preamp sounds best at 250-260v, giving good clean and dirty sound
PI sounds good and punchy at 290-300v. I'll try with v0 around 200v

[MikeO]

These are the Magnetic Components "ClassicTone" trannies by the way, and I'm really pleased with their tone. Plus being able to select the impedance for a variety of speaker cabs makes it more flexible than a typical Fender too.

Glad to hear that! They seem like a great company based on email replies I've received from them. I'm about to buy their redesigned OT for a Fender Hot Rod amp and use it for an old Silvertone 1484. The smaller size of it should fit & work out great compared to a Bassman-style OT.

[Flames1950]

That's why I have a dual pot sitting out to put in, to act as a voltage divider/extra grid resistance going into the reverb at V2. May also have to consider less resistance to ground at the V3a input and output where the signal joins back in with the dry signal. (That's relative to this build, where V2 is the paralleled 12AT7 reverb driver, and V3 is the 7025/12AX7 reverb recovery/gain stage after mixing.)

Incidentally, this is why you don't brainstorm these little schemes when cold medicine has kept you up most of the night. Even more embarassing is that I didn't even think about it a couple of days later, but wired it up -- with the first dual pot leaking enough signal to ground that the amp was quite quiet (given a choice between going through the 3M resistor or the 250K pot to ground, where would you go??)

Simply balancing the "mix" of the dry and wet signals by adjusting the 3M resistor down to 1M was much more pleasant to the ear, and far less dumb to boot!!!