NAD: '72 Traynor YBA-1A
 

New Canadian Bass Head Day Eh!

So long story short, I tell my friend with who I play in my second project that I'm looking specifically for a Traynor YBA-1 Bassmaster head, he reply by this: "Oh, a bassmaster right? Yeah, I got one of those". So he really did had the exact head I was looking for, after some harassment he decided to sell it to me. Funny fact: He's also the former owner of the Big B cab I also own. So its a stack back together now!

Specs:

Traynor YBA-1 "Bassmaster"
Year made: Somewhere between 1966 and 1968
45 watt @ 8 ohm output
2 separate channel with their own volume pots (high/low input for both)
2x EL34 power tubes
3x 12AX7 preamp tubes

I haven't compared yet the amp to the original schematics, but I can tell for sure that some mods have been done.

- The originals RCA 6CA7 tubes have been replaced by EL34, dunno if the bias has been changed.
- One of the channel's input jacks has been removed and disconnected.
- The power chord has been upgraded with a three legged chord and the ground lift has been removed.
- I can see that some capacitors has been changed, but most seems stock.
- One of the powertube socket has also been changed
- It looks like that the output transfomer has been changed/moved.

So here are the pics, I'll now begin to work on it this afternoon and tomorrow. Hope to make it work right so I can begin to mod it.

Behold the Canadian stack of dooooooooooom







According to the serial number, I can tell for sure that it has been made somewhere between 1966 and 1968



Cap-cans, one seems stock, other left one is different



Power Transformer look stock according to my research, might have to contact Hammonds to get their exact specs. Same goes with the Output Transformer on the right.





And now, the gut shots. Look at all the place I have to screw around!



Volume pots for both channel.



Input jacks, or what's left of them.



Some other pots. Caps seems stocks, but I'll compare the value to the schematic.



Standby switch and pilot light, wich doesn't look stock either.



Power tube sockets. One is different than the other, according to the resistor attached to it I'd say that the right on is newer.



Preamp tube socket. Not much to say. Wiring is old, haven't said that yet, so here's something to say.



Power chord, as I said, this isn't stock has it has a ground on it. (Trombone isn't part of the circuit)



Rectifier diodes PH 204 DSI, after a quick search they seems to be some old silicon diodes.



Those are connected with the input jacks. Those capacitors are obvisouly really young compared to the rest. After a comparison with an schematic, those are 100pf and 22pf cap, replacing the originals 125pf



So thats pretty much it for pictures. I will not begin to try and understand how this little amp works. Not much is stock, seems that a couple of mods has been done, I'll try to get them all. I have some mods on my mind, we'll see how it'll turn out.

Cheers

FYI, The serial number indicates the amp was made in April of 1972. It was the 896th one made up until that date.

Enjoy,

TD

PS - If you want to clean the crap off of the grill cloth on the YC810 cabinet, pull the grill frame off the front of the cabinet (at the bottom) and take it outside and spray it with Spray 9 cleaner on both sides. Wait for 5-10 minues then hose it down and let it sit to dry. Works wonders.

What sort of mods are you planning?

Looks like a neat project.... hnad!

Nice gear. I have a YBA1 and a Big B cabinet as well and like both of them.

Hey man, cheers, you are totally right about the serial number, I forgot to fix this part of the post when I copied this thread from Sevenstring.org. But thanks for the clearup and the cleaning tip!

An effect loop, a bright switch, another swich to add/remove the channel two, replace EL34 by KT88 and add a bias pot, for now

Thanks man!

Nice, those seems to be found everywhere in Canada, I see plenty in the classified, hope to bring mine back to its past glory. Cheers!

Best bump up the filter caps to 50uF for the KT88's, the trani's can handle it.

Sorry for the newb question, but I'm just beginning to mod/build amps.

What would be the advantages of doing this changes? I could always order some new cap-cans when I'll get the tubes

Cheers!

YBA-1A mods for bass
 

IMO this is a perfect amp to mod to use 6550 power tubes.
Did this many years ago with my own 'buggy bumper' 70's version. Got some notes on my changes somewhere. It involved changing the screen resistors, maybe some socket rewiring.
Also modified the preamp section to an approximate SVT preamp, complete with Ampeg style tone stack (modified Baxandall). Lifted all the values from Ampeg SVT schematic with mild tweaking to account for slightly different gain structure. It really is a nice amp for bass now. More power/headroom, and tone controls that work.
If interested, I'll try to find my notes. At least it's a good starting point.
If the fan is noisy, there is usually a little cover in the middle of the fan blade, that can be removed, and oil can be added to quiet it down. Not all the fans are the same, though. Be careful.

If you can find those note, I'm totally in. Mine doesn't have a fan though, dunno how necessary those are lol. But for the rest, I'm highly interested!

I don't think you should consider the KT88 for this amp. The tube sockets are fairly close which will crate "hot spots" on the tube envelopes.

Hmm I had that in mind for a while, thought that I read somewhere that someone used KT88s but can't find one that actually gives a positive result....

Anyway, I took my ruler: center to center the tube sockets measure 5.5cm. JJ's KT88 are 5.2mm large, means that the tube would be 3mm appart, wich is quite close. Tung Sol's reissue 6550 are also 5.2cm large, however JJ's 6550 are 4.3 cm large, so they'd be about 1.2 cm appart.

That raises a question: how close does it begin to be dangerous? Think I'll do some research on my side.

You don't have to re-invent the wheel. As I recall, that's a nice-sounding little head stock.

IIRC the original Mazda Octal data and application notes for the KT88 state that they should be a minimum of 3" apart. At that spacing they need to have certain pins in a line to keep the coolest part of the envelopes facing each other.

If you are thinking that these tubes will equate to more power output you are incorrect. There will be no discernible difference.

Don't worry guys, I'm aware of all of that. Thing is, this amp was already in bad shape and modded when I got it. I want to learn how to mod and fix amps, since this amp is pretty easy to understand and have a lot of space in it, plus I got it for pretty cheap, I want to practice myself on it. First I'll fix it, then I'll mod it. Maybe I'll bring it back stock after, I'll try to not add any holes to it. But in the end, I want to do some experiences with it.

Just to add, I bought a Weber kit some time ago, here's the building thread on SSO: http://www.sevenstring.org/forum/lut...ng-thread.html

This amp is just too hard to begin with, reason I needed this to have something easier to learn with.

Just wanted to clear that up, I'm not mad or anything. I'm looking for any help or opinion to learn though.

Cheers! :bassist:

Just realized that that's a YBA-1 not YBA-1A
 

Looking at the pictures again, and the fact that there's no fan.
= YBA-1 not YBA-1A
The "1A" had a much higher plate voltage. Don't think the YBA1 is suitable for the 6550 or KT88 tubes.
This amp will sound good with 6L6 or KT66 tubes for bass.
This is just not a very powerful amp. It can, however, be set up for some really nice bass tones ala Fender Bassman or Ampeg SB12/15.
If you need more power, the YBA1 is a very nice guitar head with either Marshall or Fender preamp topology mods and output tubes appropriate to each setup.
I have one of each. When I used to use the Marshally version for guitar, the other guys in the band would make nice comments.
Not to discourage you, but, that head will barely keep up with a drummer, let alone with one or two other guitar amps in the 50 watt range blasting away.

If you are talking the original KT66, they're even larger than the '88. I've have a pair that I have owned for going on fifty years. I guess I should use them one day! :D

yeah the YBA1a is one of my holy grail amps. The last one I owned would push at least 90 watts out of a pair of EL34. My amp tech at the time couldnt believe his scope.
The YBA1 sounds almost as good, but there is a certain raw primal quality of the YBA1a running EL34 tubes at the outer limits of their performance. Ever been to quarter drag race? Yeah like that.

Well thanks for the clearup! Wasn't sure what was the difference between the YBA1A and YBA1. Guess those who ran KT88/6550 had the A version then. Oh well, I'll see what I'll do, new EL34, KT77, 6CA7 or 6L6 then. You ain't discouraging me, don't worry. If I can use it in my current project, good enough, else it'll just be my practice amp. Either way I'll do some testing :D

Oh well, maybe I'll look for a YBA1-A someday then ahaha

Cheers and thanks for all the inputs!