YBA-1A with 6l6's

[tommy d]

Just bought this amp: late 60's with bumper trim, sidefan and no pop top. This amp had been modded to take 6l6 from EL34's and sounded just OK when I bought it but the iron looked good, a pair of RCA 6L6GW's and three Phillips (Great Britain) 12AX7's so I thought why not?

$230.00 and mid 90's NOS Sovteks 6L6's (12AXYWA, 12AXYWA, 12AXYWB) and wow, this amp rips! My buddy who just came off tour doing stage sound with Bob Seger and Steely Dan was there when I fired it up with the new tubes and his comment was "extreme sack". Love it

Will recap and reverse engineer the 6L6 mod and others: the tone circuit looks stock (YBA-1A comes stock with 500K pots) and gain stages have not been single channeled (I do use a jumper cable).

Will build 2x12 EVM 12L open-back cab and call it a day. BTW EVM 12L are now being sold by EV again 8 and 16 ohm!!! http://www.electrovoice.com/products/410.html $194 http://www.zzounds.com/item--ELVEVM12LCLSC

[loudthud]

The YBA-1A wants an 8 ohm load. Because of the 560V B+, a 4 ohm load is rather hard on the output tubes. With EVM 12L's it will be extremely loud, hearing protection is advised.

[tommy d]

I don't exactly know what to do about the volume besides a master volume... However, I'm sold on the EVM's b/c of the clarity, durability and power handling so I'm stuck with monstrous tone and volume. I'll live - trust me! I've wanted this tone for twenty + years.

I have a fender set neck tele and will put in EMG's (if they work) to try to keep the volume in check by front loading the gain stages.

Any ideas would be appreciated (18 watts excepted!)

[tommy d]

Fast forward two years --> I got a 20 watt YGM-3 and a Blues Jr! I restored the YBA-1A and just use it for bass, like it was meant for. Rest assured that the YBA sits unmolested by plexi hack jobs!

[loudthud]

Those Plexi hack jobs don't sell very well on ebay. Sellers seem to think they are worth more than a stock YBA ha ha. Have you tried any other speakers in the Guitar Mate?

[tommy d]

I was lucky, it came with an Weber Blue Dog alnico 30 watt and beam blocker and I am just thrilled. IMO, it is the "right" speaker for the amp, perfect with a tele! I can't imagine what would be better but for the sake of conversation, what did you have in mind?

[loudthud]

I don't have any recommendations, just curious on you experience. An EVM 12L might be good because of it's efficiency and clarity but that might not be what you want. Lots of possibilities from Eminence, too many for me to buy one of each and try. Weber, people swear by them not at them. Don't remember ever hearing a bad report on them.

[mac1amps]

I just finished overhauling a YBA-1(A) for a client of mine.'Love those nice Hammond transformers. Personally, I can't imagine why someone would convert one of those to take 6L6's, the EL34's in this one sound excellent (not to mention, that's what the O.T. was made for). My client also had me cascade the two channels. Damn! this baby screams!! Unfortunately I'm gonna' have to put a master volume in it (I HATE master volumes), but in spite of that, this sucker's STILL going to be a Monster.

[tommy d]

My client also had me cascade the two channels. Damn! this baby screams!! Unfortunately I'm gonna' have to put a master volume in it (I HATE master volumes), but in spite of that, this sucker's STILL going to be a Monster.

The perma cascade! The jumper was not good enough huh? Without doubt a fantastic sounding amp stock. I did run Sovtek 5881's safely for quite a while in this amp - it was never "converted", I was mistaken, the RCA's 6L6 were left to die with 535V on the plate. I was surprised but the 5881 could take the pressure and they sounded awesome, they broke up sooner and with NOS Mullard in 1 and 2 it was a vicious chugger, still good with svet EL34 but I prefered the 6L6's. Apparently the sovtek 5881 were designed as servo actuators in aircraft (military: so they could fly after nuclear holocost?) and can withstand all sorts of things the 6L6 couldn't dream of like rough shock and 600v B+.

Are you installing the TW post PI, double gang MV? I had bought the parts but decided the old gal was perfect just the way she was: LOUD

[tommy d]

Unfortunately I'm gonna' have to put a master volume in it (I HATE master volumes), but in spite of that, this sucker's STILL going to be a Monster.

BTW how did that master volume sound after all said and done?

[mac1amps]

Actually, it came out pretty well (as master volumes go). I used the dual 500K/ Lin. post-phase-inverter configuration. My client was very happy with it as well.