"Twenty" v2: Traynor Bass Mate YBA-2

[xtian]

This build is based on the Traynor Bass Mate YBA-2. Super simple, with two 12ax7, and two 6V6.

Ready to drill the chassis tomorrow. Happy Caturday!

[Bear]

I don't think I'd ever seen anybody mount a radial power cap like that -- pretty clever way to keep costs down and layouts tight. Do you need to give them a shot of glue to hold them in place or anything like that?

I thought the Bassmates were EL-84. Were there 6V6 variants or are you just changing it up?

[rdjones]

I don't think I'd ever seen anybody mount a radial power cap like that -- pretty clever way to keep costs down and layouts tight. Do you need to give them a shot of glue to hold them in place or anything like that?

I thought the Bassmates were EL-84. Were there 6V6 variants or are you just changing it up?

YBA-2 6V6
YBA-2A, YBA-2B 6BQ5

The above info is from the Traynor site, but I have seen both 6V6 and 6BQ5 versions of both the head and combo.

rd

[xtian]

The e-caps are light in weight, and have sturdy leads, so they feel quite solid when soldered this way. However, when I mounted the board in the chassis and tried to install my input jack, CRASH! no enough clearance. So you'll see my solution tomorrow when I post new photos.

RD is right about the 6v6 vs EL84 variants.

[rdjones]

... 6v6 vs EL84 variants.

[xtian]

Finished, fired up, and fun!

As I imagined, the .05 coupling caps let too much bass thru. Too mushy. Will try 0.02's.

It's fun to swap 12au7 and 12ax7 in V1--large difference in gain and distortion. Sounds great opened up all the way.

The Tone control, also as expected, isn't great. Sucks a lot of gain out of the signal.

I like the "IEC Connector, Chassis Mount, EMI Filtered [430], Item #:216-1017, Unit price:$1.25 USD" from surplus-electronics-sales.com. Nice and solid with a metal plate for the bolt holes instead of plastic.

Strangely, I have DC on the guitar cable (heard as scratchy volume pot). Measures 0.1v with amp's volume at zero, and 0.25v with amp's volume maxed. Where could this be coming from?!?

[Reeltarded]

Excellent chimpery!! You are good at this.

DC.. ok, what have you done to the cap there? Have you made something bleed?

Crafty.

[xtian]

Excellent chimpery!! You are good at this.

Thanks, man! Monkey needs more bananas!

DC.. ok, what have you done to the cap there? Have you made something bleed?

What cap? The input signal is connected thru a 33K resistor directly to the grid of V1. So, is there DC leaking thru the valve?

[Reeltarded]

I looked all over for what it would be..

Are you getting DC with any tube in v1?

[markr14850]

So, is there DC leaking thru the valve?

Might be grid current. Maybe you're biased a bit hot? Or B+ is a bit low. Or try some other tubes.

[Reeltarded]

That is what I was thinking too. I have been messing with larger plate loads and umm... well, the big ones nibble at my fingers just a touch.

I was wondering if the difference in the au7 might be the difference. Just a wag though. I am a real monkey not a pretend one.

[xtian]

Yes, some tubes are better, with little or no DC leak on the input.

With a 12ax7 in V1, I've got 115 on the plate and 0.68 on the cathode. 110 and 106v on the plates of the PI. Sounds a bit low, huh?

I changed coupling cap C2 to 0.01; still too much bass. And I might describe the high end when driven as crispy or grainy. Could be sweeter. Think this would improve with higher voltage?

In the various schematics, there's another that's nearly identical to this one, except the first dropping resistor is 4.7K instead of 47K. Maybe that's my next target.

[Reeltarded]

That sounds like a good way to go!

Maybe you need a capacitor on your input before the nanner bites you.

[M Fowler]

Nice looking amp.

[xtian]

Settled on 0.0033uF coupling cap after V1. This cleared up the fatty bass response.

Replaced 47K first dropping resistor with 10K. Much better voltages: V1 plate and cathode 179 and 1.12, and PI plates at about 172.

Power tube plates at 320, cathode at 16.1, which gives me damn near 20 watts.