blackface kit recommendations: twin or super reverb

[Roe]

yes but TAD is expensive. their kits are very close to mojo

The TAD cabs are made by Mojo - at least they were a few years ago.

yes. its cheaper to buy straight from mojo.

[Roe]

Update: the marsh twin kit lives. it sounds like its supposed to but I havent burned it in yet

plate voltage is 452v, screens the same - shouldn't the screens be lower?
heathers are high: 6.8-6.9v

tremolo seems to be too fast. may have to change a .01 cap to .02 or something

[Roe]

amp is starting to sound like a beast. managed to get a singing lead tone from a strat without pedals (but with a 28k mid pot dimed). however, heather voltage is too high (7v). seem that I need .o1ohm resistor

[Mars Hall]

amp is starting to sound like a beast. managed to get a singing lead tone from a strat without pedals (but with a 28k mid pot dimed). however, heather voltage is too high (7v). seem that I need .o1ohm resistor

Yeah, BF era amps are a mid-scoop design. Leo was on the quest for "clean" headroom.

[Roe]

amp is starting to sound like a beast. managed to get a singing lead tone from a strat without pedals (but with a 28k mid pot dimed). however, heather voltage is too high (7v). seem that I need .o1ohm resistor

Yeah, BF era amps are a mid-scoop design. Leo was on the quest for "clean" headroom.

the cool thing is that a 25k pot will give you all the classic tone plus some fatter tones - works great. on the normal channel, I'm even using a 100kA mid pot. 1-3 is classic BF fender whereas higher settings sound more dumblish.

[Roe]

I've experimented with filtering. much prefer 100uf on the mains over 50uf.
tried 20, 30, 40 and 50uf on the screens. ended up with 40. this is not only because of tightness but because these particular caps had a nicer highend. (f&t 30uf was worst; atom 80s in series best; tad 20uf good)

using the 240v secondary I get 6.7v on the heaters but only 432v on the plates :-/ . wall voltage is 228-237v

[Mars Hall]

I've experimented with filtering. much prefer 100uf on the mains over 50uf.
tried 20, 30, 40 and 50uf on the screens. ended up with 40. this is not only because of tightness but because these particular caps had a nicer highend. (f&t 30uf was worst; atom 80s in series best; tad 20uf good)

using the 240v secondary I get 6.7v on the heaters but only 432v on the plates :-/ . wall voltage is 228-237v

When you say 100uf, is that the value of each cap or the value of them both once they are in series? So did you use 2 100uf caps in series or the 220uf caps in series?

On my 66 BFSR I used the 2 220uf caps in the mains. I had ghosting issues at high volumes. I got the idea from Gerald Weber. I really like what it did for the low end. It tightened up the bass real nice.

[Roe]

I mean 100uf in total. I'm experimenting with the different PIs now. the rivera (rev. II) pi had good note separation but lacked the classical sound. I like both the BF and SF values. the SF values can drive the power amp real hard, the BF values seems more lofi - the pi distorts more but doesn't drive the output section as hard

[Roe]

after trying all the different phase inverters I came to the following conclusions:
- ab763 (standard): work well with 12ax7s but not really tuned for 12at7s. distorts quite a lot in a slightly lofi way. bass can get muddy. personally I didn't like the 33k tail resistor, I prefer 15k or 22k
- aa769: as expected, this is cleaner and more articulate. bass is much tighter, esp. when running flat out. it drives the power section hard, resulting in plenty of distortion when running flat out. although the phase inverter doesn't distort much, it can drive the power amp real hard. for some reason, people overlook this since they dont run the amps hard enough. I didn't care for the 33k tail resistor, favouring the 22k
- 100w specs: 470R K and .01uf input cap. Sound almost like a mixture of ab763 and aa769
- rivera/reverb II: articulated, good note definition. has a signature sound but lacks the classical fender sound. cool if you have 100 amps and can have one with this phase inverter.
Conclusion: I can do without the rivera and 100w specs but not the ab763 and aa769. Since I already have duzin of amps with the standard specs (ala ab763) I went with the aa769 now. the 69 specs is more articulated, and gives you better response and control when running flat out. its much better suited for 12at7s than the ab763

[Roe]

I've tried a lot of tweaks in my amp, basically all the 70s specs as well as the allen and clark specs. I prefer the ab763 with the following exceptions:
- PI as mentioned
- higher mains filtering - helps with bass and gives a faster attack. the twin used the same filtering as the 35w-40w amps and is underfiltered when running flat out, at least by modern standards
- 25k mid pot - give all the classic tones plus some fatter tones
- reducing the 500pf reverb input cap a little (am using 300pf now - others have used 250pf) - this reduces reverb on the deep bass
- upping .01u to .02 in trem to slow it down

amp sounds absolutely great even with new production tubes. I got some of the coolest lead tones ever with a p90 korina jr into a cranked reverb channel and a weber 12f150t

[Flames1950]

I've been playing a Twin/Twin Reverb mongrel I built for a few weeks now (BF Twin Reverb preamp and reverb section, blonde 6G6 Twin PI and power amp but still using a 12AT7 in the PI) and I'm about to the point of modding the reverb section as well. I switched from a long decay to a medium decay tank, swapped in lower gain tubes -- the stock Fender circuit is still too splashy and sensitive for the rest of the amp. I may roll off both some highs and lows, and I may go to a dual pot to work both the input and output levels at the same time to make the reverb pot more flexible.

Not sure why my reverb is so touchy and splashy -- this amp was based directly off a Bruno Cowtipper I modded for a forum member which didn't seem to have an overbearing reverb........once I'm done modding this reverb to my satisfaction I may build a JTM45 with a reverb in it for s***s and giggles.

[MikeO]

great thread, thanks for posting all that! I've got a '74 Twin Reverb that I rebuilt to AB763 specs but I'm not totally happy... time to experiment

[Flames1950]

I still haven't gotten around to reworking the reverb in this, I've been enjoying having a high powered "Fender" to play too much to tear it apart yet.......

[Roe]

Very nice work Andy. Would you care to share more details? I got blocking distortion in v3/reverb driver when running volume and treble at 10 but adding a grid resistor solved the problem without killing audible highs


my twin reverb is less minimalistic but sounds great. the overdriven sounds are better than I thought and I've tamed that blackface bass flabbiness. I'm running some weber Neomags with give me great jbl tone without the weight

[shakti]

Got any pics, Roe? And I'd love to hear how the Weber Neomags compare with the real D120Fs...