Finished my amp.....................finally!!!

[Humbucker]

Hey guys,

This is an update on a 1970 Traynor YBA-1 BassMaster amp that I bought appx.4-5 months ago. I've asked many questions on this board and on other BBS too, concerning this particular amp, so I thought that I should post a follow-up.

The power supply caps look fairly recent, so I left them alone.

I split the cathodes on V1 and made one side, the "Normal" channel(820 ohm/250uF) and the other side is the "Bright" channel(2.7K/0.68uF). I replaced the stock 4 Meg volume pot for the "Normal" channel with a 1 Meg Volume pot with a built-in OFF switch, when this volume pot is fully CCW it disconnects the "Normal" channel, so the amp works as a single channel amp. This feature turned out to be a VERY good idea, it makes the "Bright" channel much more crunchy and fat! You've got to try this mod out, it's great!!!

I also replaced the stock 4 Meg volume pot for the "Bright" channel with a 1 Meg volume push-pull pot, when pulled out it's a Plexi-style "mid-boost" switch, pretty cool! Gives an added midrangey crunch, very nice!

I replaced the stock 0.02uF input cap for the "Bright" channel with a 0.0022uF cap.

I added a pot in the NFB loop, to adjust the NFB between 47K and 97K. I also rewired the Presence control to Bassman/Plexi Presence control specs.

I undid the U.L. taps on the U.L. output transformer in my amp(not stock) and installed a couple of 470ohm/5W resistors for the usual screen supply, and I installed some 1.5K/2W grid resistors too.

The amp now has a trimpot for adjusting bias. I tried doing the Ken Fisher master volume "type-3" deal, the one where you connect a 1 Meg pot between pins 6 of each output tube. I didn't like it at all, so I'm going to strip it out.

One other thing that I did was to add a missing node to drop the voltage on the preamp tubes.

When I fired this thing up tonight, the first thing I did was set the bias. I've got the two Sylvania 6CA7 power tubes running at about 43ma at 440V on the plates. I'm not sure if 6CA7 tubes are rated at 25 watts, like most 6L6 and EL34 tubes?

And now we move into how it all sounds...........

Good lord!!! What a kick-ass rockin' amp this thing finally turned out to be!
8^)

Nice old-school crunch with tons of singing harmonics. It's like the voice of GOD. Oh my! This amp has FAR exceeded my expectations, I had a feeling that it would sound good but I just can't get over the final results. This is going to be my main amp from now on.

Plugging in my 4x12" closedback cab with Celestion Greenbacks just rocks. I'm surprised at how much crunch I can get from this amp, mmaaaaaaannnnnn!

Anyway, enough gushing already. I just want to thank everybody that helped me out on this project and to let you know how it turned out.

Thank you all!

Regards,
Charlie

[Humbucker]

Something else that I did was to replace the stock "bright" cap with a 100pF Silver Mica cap. I also replaced the "Treble" cap with a 250pF Silver Mica cap. The stock 0.1uF "Bass" cap was replaced with a 0.02uF cap.

I also replaced the stock 100K mix resistors with 270K resistors and put a 500pF Silver Mica cap in parallel with the 270K mix resistor on the "Bright" channel.

I left the stock 47K slope resistor alone, kinda in between Fender and Marshall!
8^)

The "mid-boost " function which is switched by the "Bright" channel's push-pull Volume knob, is actually a 0.68uF cap in parallel with V2's 820 ohm cathode resistor.

I should mention that this amp had already been tampered with by a previous owner and part of the circuit board had a big burn hole in it, so I didn't mess with a dead mint Traynor.

[Humbucker]

Update..................................

Hi,

Here's a little update on this YBA-1 if anyone's interested.

I noticed that the tone controls were acting a little weird, if I turned the Bass or Low(actually midrange) knobs, nothing much happened unless the Treble knob was set really low and even then the Bass and Low knobs didn't have a great effect on the tone.

I took another look inside the amp and found that somebody had disconnected one end of the slope resistor!
8^)

So I hooked it up and talk about a lot of low end now! With this much increased low end the amp just about blows you out of the room when it's cranked, way louder than before or so it seems anyway. It's insanely loud now.

So this got me to thinking that maybe I should reconsider putting in a master volume control. I stripped out the Triode/Pentode toggle switch that I originally put in and decided to find the room to install that post phase inverter master volume that Bruce Collins outlined. I thought, I've got the parts already, so what do I have to lose?

I've been playing this amp for a few days now with the added master volume control and I must say that I'm TOTALLY happy with the results! I can basically get the same cranked tones as before but now I can dial it in at bedroom levels. Very nice mod, thank you Bruce! I'm so glad I added this master volume control, I also don't notice any negative effects to my amp's natural tone. It's a win win situation.

[Enzo]

I am glad you stuck with it and have found success. Way to go.

[roknroll]

Yba-1

Humbucker
I've been a YBA-1 fan for quite some time. If you are interested I have some time and have had excellent success with modding them into great sounding amps. There are some clips at the link below. Just scroll down to the YBA1 folder. I don't play with a pick. Recorded with Hamer Studio thru a Marshall 1936 cab, cheap mic into a cassette recorder and transferred to the hardrive. I did add just a little echo nothing else.
Regards



http://briefcase.yahoo.com/roknroll50

[Humbucker]

Awesome!!!

Hey Roknroll,

That sounds amazing dude! Great playing too, I might add.

Did you do any heavy modifications to this particular YBA-1? Did you install a master volume on this amp? Sounds sweet, nice work!

[roknroll]

Hey Roknroll,

That sounds amazing dude! Great playing too, I might add.

Did you do any heavy modifications to this particular YBA-1? Did you install a master volume on this amp? Sounds sweet, nice work!

HUM
I was just reading your reply and I reread what I wrote and realized the wording of my paragraph was a little wacked. O well, that' what sometimes happens when you use a wireless keyboard. Every now and then the receiver does not pick up the signal and you end up sounding either weird or not knowing English. Unfortunately these replies cannot be edited once they are posted. Anyway, back to important stuff.
The amp is completely modified. There is no "Traynor" circuit left. It's a single channel with v1a cascaded in to v1b (marshall style), standard pre PI master volume w a 100k resistor just before the .022 entrance to the PI. New electrolytic values and dropping resistors all changed. Also dual bias, and a switch to toggle between 47k and 100k fb.
I was never a follower of the saying that a YBA-1 is a "poor man's plexi" because it is not a plexi at all. Referring to them as plexi is like saying a Ford and a Cadilac are the same because they each have tires, a gas tank, a steering whee and rear view mirrorsl. The 2 amps very different. It certainly can be made in to a plexi and a great one at that to rival any marshall. It also makes a great moderate hi gain amp.
Regards
PS thanks for the compliments
jack

[Humbucker]

So you totally changed your amp, that figures.

I was going to say that while my YBA-1 sounds great, it doesn't rock-out as much as your amp, judging by your soundclips.

But I'm quite happy with my amp all the same, it has a beautiful clean beefy sound and it can grind pretty good but not like yours does. Both are valid amps IMHO. Mine is still basically a Fender Bassman when all is said and done.

Nice job on your amp, it sounds kick-ass!

[nakina]

hey humbucker, what exactly did you do to lower the preamp voltage?

thanks.

kevin

[Amp Kat]

Nice job dude and my regards as well !!

[Humbucker]

Hey, sorry that I took so long to reply, I've been away.

Nakina,
All that I did to lower the preamp volume was to add one or two dropping resistors and I added a bit more filtering too. I basically followed a schematic of an early YBA-1 and modified my amp to match it.

Amp Kat,
I'm not sure if you're refering to me or not, if you are, thanks for the kind words!
8^)