1972 traynor yba-1 bassmaster questions

[Kevin]

hey fellas,

i got rid of the ol' 5150 in favor of a traynor yba-1 bassmaster. it's a '72 and the circuit has some minor differences from previous years. i've attached the schematic. i don't plan to do a marshall conversion - at least not yet. however, i do plan to revert it to old bassmaster specs and try out a ppimv. right now, it's stock, other than 1k5w screen resistors and a 33k bias resistor. so, a couple of questions:

1) is the typical 500k dual ganged pot appropriate for ppimv in this circuit?

2) i want to start by converting the tone stack to a cathode follower and to get rid of the coupling caps, swamp resistors, etc., between v2a and v2b. my question is regarding the v2b plate resistor, of 63k. do i simply delete it? the schematic shows 350v going the the preamp, which is lowerered by the plate resistors, right? will this voltage be too high going straight to the v2b plate?

thanks in advance for any responses. i'll probably have a bunch of questions about this amp for you guys in the near future.

kevin.

[tubetramp]

congrats on losing the evh fuzz box and moving up to an amp that is a real monster when a few simple tricks are applied i would disuade you from screwin that beast up with a master anything on it. build an attenuator or buy one they dont really work right with post phase or any other kind of master blaster on em. get a geek macdaddy ts9 for indoor gunnery practice . you dont want to turn that classic into the monstrosity you just got rid of.if you get scared ...just turn the volume up louder my yba was puttin out 100 watt volume levels so i understand your dilemma .there are several shematics on attentuators this is a good one.

[Star*Guitar]

congrats on losing the evh fuzz box and moving up to an amp that is a real monster when a few simple tricks are applied i would disuade you from screwin that beast up with a master anything on it. build an attenuator or buy one they dont really work right with post phase or any other kind of master blaster on em. get a geek macdaddy ts9 for indoor gunnery practice . you dont want to turn that classic into the monstrosity you just got rid of.if you get scared ...just turn the volume up louder my yba was puttin out 100 watt volume levels so i understand your dilemma .there are several shematics on attentuators this is a good one.

The tube man speakth...and rightly so...

I agree completely!!! A master volume amps equals...an amp that is a master of nothing.....LOL...

[novosibir]

2) i want to start by converting the tone stack to a cathode follower and to get rid of the coupling caps, swamp resistors, etc., between v2a and v2b.

That network is a mid attenuator. So when you remove it, you'll get more gain and probably honky mids, as long as you don't diminish the treble cap to a reasonable value (390p...500p)!

my question is regarding the v2b plate resistor, of 63k. do i simply delete it? the schematic shows 350v going the the preamp, which is lowerered by the plate resistors, right? will this voltage be too high going straight to the v2b plate?

V2b is a split load converter (cathodyn stage) with a gain of 1, means ZERO amplification, so you won't loose any gain anyway, if you make it to a direct coupled CF like in Marshalls.

Tie v2a's plate directly to V2b's grid and skip V2b's 68K plate resistor (which you've misread for 63K) entirely. Enhance the cathode R to 100K and skip the 2.2K - now tie the tone stack to the cathode.

Don't worry about the 350V on the plate, because this value you're reading between the plate and ground. But a tube only cares about the voltage between its plate and cathode which is due to the large cathode R much less than 350V!

Shure you shouldn't exceed the max. filament to cathode voltage, but this is 200V with a 12AX7 - so no problem again!

Larry

[Kevin]

thanks for the responses, guys.

i was just about to go buy a pot for the MV. i'm glad you guys talked some sense into me. i'll look into that attenuator. it is kinda scary and humbling to play an amp like this after years of fuzzy MVs. like when i first fired up the engine in my nova.

anyway, i jumped the gun and did the other tweaks. the mid attenuator is gone and i swapped the treble cap with a 560p (just cuz it was around - i'll probably throw in a 270p, which is the older traynor value) and converted to a CF as per a marshall layout. thanks larry, i was concerned about overly-high voltages - i've still got a lot to learn about this stuff.

hey tramp, have you done anything to your yba? mine has no bypass caps, so i might chuck somethin' in across one o' them Rks. we'll see.

thanks again, fellas.

[jharasym]

Hi Kevin,
If you're still around, would you be able to post your schematic? I picked up a '72 with the 500K vol pots and cannot find an electronic version online.
Thanks
John