Yba-4 V2B

[dano-rator]

I just picked up a Traynor Yba-4, and while I do like the way it sounds now, it has a little more gain than I would like. Upon inspection, at some point someone had biased the first stage with 820/220uf instead of the 1k5 that was original. So I put it back to the original value. It is still a little to raw for my taste: break up comes on too early and it isn't quite smooth enough.

This amp is in really good shape, not hacked up or anything. Although it came fully loaded with el cheapo chinese tubes, I haven't tried swapping anything decent yet.

Anyhow, I think I would like to steer this thing toward more of a TW rocket type tweaked JTM kinda thing. Is that wrong? So, I'm looking at changing V2B to a cathode follower arrangement. Anyone have any suggestions?

Schematic attached (sorry, it's a crappy cell phone picture of a print out of a scan of a copy). It is available at schematic heaven, but it isn't all that good there either

http://www.webphix.com/schematic%20heav ... r_yba4.pdf

[Wiktor D]

The YBA-4 is just a YBA-1 as a combo. The circuit was constantly being tweaked, sometimes not matching the schematic that was included with the amp. The best reference (and my favorite circuit) is the original schematic from 1966. I got a YBA-4 from the late 70's for a song and by then the circuit had been heavily modified from its JTM origins, so I gutted it and put in the 66' circuit. Throwing a 5751 in V1 as well as modding it for 6550s makes it a killer bass amp.

Check the following site, it has an amazing amount of information on the amps as well as different eras of the circuit. Also it lists the common mods made to these amps to get more oomf out of them.

http://www.0rigami.com/vb/models.html

[renshen1957]

This amp is in really good shape, not hacked up or anything. Although it came fully loaded with el cheapo chinese tubes, I haven't tried swapping anything decent yet.

Anyhow, I think I would like to steer this thing toward more of a TW rocket type tweaked JTM kinda thing. Is that wrong? So, I'm looking at changing V2B to a cathode follower arrangement. Anyone have any suggestions?

Schematic attached (sorry, it's a crappy cell phone picture of a print out of a scan of a copy). It is available at schematic heaven, but it isn't all that good there either

http://www.webphix.com/schematic%20heav ... r_yba4.pdf

Hi

For goodness sakes, change out the Chinese preamp tubes for some NOS or UOS tubes, and get some reissue 6CA7 tubes to replace the EL34s. You may like the sound better.

Peter Traynor's Bassmaster was originally based on the 5F6-A Tweed Bassman amp with industrial versions of the 6L6, the 7027. The 6CA7 version became available (North American Beam Tetrode version of the EL34, sounds more like a hybrid with a 6L6), with a higher 540 Volt rail and raw bias voltage on G3 (a Mullard Hi-Fi notes application) which linearized the tubes for a loud and clean sound, about 75-80 Watts. It had a cathode follower as did the 4 power tube Custom Special. Later Bassmaster Versions changed the CF to Gainstage, date from 1972.

Later versions of the Custom Special (4 tube version) replaced the CF with a gain stage and the tone stack has an additional tube (active EQ) before the PA stage which may or may not have a MV. (Peter Traynor's Amps had master volumes before everyone else, 1958 for a custom build, early 1960s for some production models, this is where Fender stole the idea before Marshall did later)

The Schematic Heaven link has a gain stage instead of of the amp, so probably dates from thelater version of the Bassmaster

Check out http://www.webphix.com/schematic%20heav ... i_yba1.pdf

Which has three schematics for price of one (free).

I haven't heard the later versions of the preamp; consensus in literature has most players preferring the CF early version of the preamp.

More than one Bassmaster has been modded into Plexi with a few component value changes and changing G3 connection to Ground (Earth). You might want to use a switch so you can have G3 either connected to Bias or Grounded.

My Son has the head version YBA1-1A (or Mk II) and its a great bass amp; it is anything but raw.

It's chock full of Mullard Mustard Caps, and the Angels will look down from heaven and weep soft tears if you remove these; unless these are leaky Caps, then they'll just sniffle a little.

Best Regards,

Steve

PS Kevin O'Connors The Ultimate Tone Vol. 3 has two Chapters devoted to the Bassmaster (early 7027 version, later 6CA7) and its derivative amps, the Custom Special and Super Custom Special. The

[dano-rator]

Thanks renshen1957 and Wiktor D for the info & advice. This one was wired per the later schematic with the gain stage not the cathode follower, so I redid it as a per the earlier Bandmaster schematic. I think that made the amp much more controllable, a really great blues amp, but still cleans up nicely! I haven't tried it with the bass yet, but I am loving it with my Tele. I am still fooling around with different values here and there to really bring it together, but as of right now I am really happy with it.

She still has all mustard signal caps and I have no intention of swapping them out as they don't seem to be leaky or bad so the angels can sleep peacefully. I changed out the EL34's for some Sylvania 6CA7's that came in a MusicMan I've had and that helped quit a bit as well.

I'm going to try the G3 raw bias switch when I get a little more time to dig into it.

Anyway, thanks again for the help!

Dan