# YBA-2 clone (6V6 version) conception



## anaerobe

Hi all,

I have decided to accumulate all the parts needed to build an early clone (or something very close to) a Traynor YBA-2 Bass Mate using 6v6 tubes for output. I would add a few things such as a standby switch and a safety item - grounded power cord, but otherwise would stay close to the plan.

Here is an article on the original:

Traynor YBA-2 Bass Mate

The earliest version is 5y3 rectified, which is what I will do. From what I can gather, the original (and difficult to locate) schematic used a 6AV6 in V1 with a 12AX7 in V2. Looks a lot like a Fender Harvard circuit:

http://tubeamplifierparts.com/layouts/fender_harvard_5f10_layout.gif

Here is a version of the (later version) YBA-2 schematic:

http://ralfthedestroyer.com/wp-content/uploads/traynor_bassmate_yba2.gif

and a link to a pic of the control panel:

http://www.0rigami.com/vb/yba-2__BM_Control_2_DSC_0458.JPG

Simple!

Later versions used a 12AU7 in V1.

Successes: 
- Hammond A0-63 organ chassis at a local location. The chassis itself is almost the right size (big like most Traynor stuff from the day). It has an absolute gigantic PT and OT (too big).

- CTS 15" speaker ca. ~ late 1970's - not perfect but close.

- Healthy PT with a 325 VAC centre tap on the secondary high voltage leads (well over 600 VAC untapped!).

- 2122 Bell mono-block with dead PT to give up its 6v6's (healthy as tested on my Stark tester), chicken knobs, switches, output tranny tapped for 4, 8 and 16 ohm outputs. (I'm not committed to the OT from the Bell, and might buy a Hammond that is closer in spec to the original in the YBA-2).










Challenges:

Finding an actual schematic of the tube rectified variant. Does anyone have any leads for me?

Thanks,

Ian


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## torndownunit

Oh man the people at an old Traynor Yahoo group sent me schematics for like every Traynor amp. Those guys were awesome for that. I have no idea if that group even exists anymore though, and I definitely don't have the files.

I wish I still owned my YBA-2 head. I loved that amp. One of the only pieces of gear I regret selling.

EDIT: says it still up and running. I am pretty sure this is the group: Yahoo! Groups


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## traynor_garnet

That's my old amp in the article!

TG


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## zurn

I'm pretty sure it's my amp now


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## traynor_garnet

Well, actually your amp and the tube rectified combo in the vintage guitar article were both mine! 

I may have the schematic for the tube rectified bassmate around. Let me look.

TG


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## anaerobe

Wow, this is great... the support rocks.

Thanks TG, torndownunit... if you guys could help me get old diagram it'll make things much much simpler. Zurn thats a GREAT pic... helps a lot.

The electrolytic caps on the upper left look much like the what the later schematic specifies here:

http://www.0rigami.com/vb/traynor_bassmate_yba2.pdf

eg, a 30 MF, a 20 MF, and a 30 MF.... which is somewhat different from the 16, 16 and 16 of the basic Fender Harvard - I think I'll stick to the Traynor filter cap specs.


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## anaerobe

Last evening I test fit the new (old but functional) power transformer.










Here's a pic. Because its a flush-mounted PT, I made a base from a piece of stainless. Did I mention my function-over-beauty credo? 

When I'm testing the power transformer taps, I bring things up to speed slowly with my variac. I found this one many moons ago (below).










This tranny has two low voltage secondary paired leads... one at 7.6 VAC and the other at 6.1 VAC. I'll use the latter for the heaters on the 6v6's and preamp stage, and hopefully knock down the 7.6 to ~ 5 VAC-ish for the rectifier. A 5Y3 tube draws 2 A, so I will need to drop 2.6VAC/2A = around 1.3 ohms. This resistor will need to dissipate around 5 watts, so will look for a 10 watt overkill @ 1.3 ohms on one side, or paired 0.68 ohms on each leg (tap lead).
Make sense?

(OR - I could wire up a second small PT with known 5 VAC taps. Not a terribly elegant solution).

EDIT: I did neither, see below.

Finally, I'm reusing the old rectifier socket, looks to be in good shape.


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## epis

Unloaded transformer always give you higher voltages readings, 7.6V is your 6.3V heater windings, 6.1V is actually 5V rectifer heater windings.
You're good to go without additional resistors and transformer.


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## anaerobe

Thanks. I tried other trannys from my horde and one or two gave me 6.3V ... but what you say makes sense and I will try by wiring it up as you recommend. This is my first try building from scratch (have done kits, but this is a different ballgame).

EDIT -> Epis, you were right. I wired up rectifier socket with the 6.1 unloaded leads and the high voltage leads, plugged an old 5Y3 in - et voila - the voltage on the pins were 5.3 V with the tube glowing as it should and the variac cranked to 100%. Many thanks. 

Progress.


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## torndownunit

anaerobe said:


> Wow, this is great... the support rocks.
> 
> Thanks TG, torndownunit... if you guys could help me get old diagram it'll make things much much simpler. Zurn thats a GREAT pic... helps a lot.
> 
> The electrolytic caps on the upper left look much like the what the later schematic specifies here:
> 
> http://www.0rigami.com/vb/traynor_bassmate_yba2.pdf
> 
> eg, a 30 MF, a 20 MF, and a 30 MF.... which is somewhat different from the 16, 16 and 16 of the basic Fender Harvard - I think I'll stick to the Traynor filter cap specs.


I'll see if I can find my old posting on that group.


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## anaerobe

Thanks torndownunit!

Zurn, could you please flip the amp over and take a pic so I can get the numbers on the Output Transformer?
The OT is a big part of the sound of these little guys IMHO.

For now, I'm going with the old OT from the Bell 2122 mono block, but Mercury Magnetics or even Trinity Amps might have something for me.

Thank you again (great forum!)


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## zurn

anaerobe said:


> Thanks torndownunit!
> 
> Zurn, could you please flip the amp over and take a pic so I can get the numbers on the Output Transformer?
> The OT is a big part of the sound of these little guys IMHO.
> 
> For now, I'm going with the old OT from the Bell 2122 mono block, but Mercury Magnetics or even Trinity Amps might have something for me.
> 
> Thank you again (great forum!)


Sure i'll try and do it tonight, mine's the head version so I have to take it out of the shell.


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## zurn

Ok I had time at lunch so I took it out on the deck for a photo shoot 

The rest of the 70 pics are here


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## anaerobe

Very nice, thanks for doing this!

A Hammond 1750E OT might be a good substitute for the OT in the pic.


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## traynor_garnet

Even if you build an early tube rectified circuit, I would suggest incorporating the separate bass and treble control on the later 6V6 units. The early units with the single "tone" knob are certainly cool and sound great, but there are no ill effects/negative consequences of changing to separate bass and treble controls as Traynor did on the slightly later 6V6 units.

Having owned every incarnation of the early bassmates (several tube rectified units, SS rectified "tone knob" only units, and later SS rectifiers with separate treb and bass controls), I have heard no real differences in the amps' basic sound. IOW, the circuit doesn't get screwed up with the added controls, you just get the ability to dial in the treble and bass independently; this can be really helpful when changing guitars or cabs.

TG


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## anaerobe

traynor_garnet said:


> Even if you build an early tube rectified circuit, I would suggest incorporating the separate bass and treble control on the later 6V6 units. The early units with the single "tone" knob are certainly cool and sound great, but there are no ill effects/negative consequences of changing to separate bass and treble controls as Traynor did on the slightly later 6V6 units.
> Having owned every incarnation of the early bassmates (several tube rectified units, SS rectified "tone knob" only units, and later SS rectifiers with separate treb and bass controls), I have heard no real differences in the amps' basic sound. IOW, the circuit doesn't get screwed up with the added controls, you just get the ability to dial in the treble and bass independently; this can be really helpful when changing guitars or cabs.
> TG


Thanks TG. I really appreciate that comment. I am definitely going with the tube rectified circuit. (That part is already wired up and tested). With the boxful of parts that I have is that I can definitely think about later versions. To be honest I haven't seen a schematic or layout that specs bass and treble controls vs one "tone" control per se, but I will research it****. The fun part will be to build one version, see how that sounds, then play with small changes.

One big change I have made to the classic YBA-2 circuit is to add a standby switch in addition to on/off.

****Edit: http://www.0rigami.com/vb/traynor_bassmate_yba2_all.pdf

Bingo! Found this at Velvet Black. See the third page in the figure. Schematic of the YBA-2A, solid state diode rectified, drawn in 1966, weirdly, before the YBA-2 with the 12AU7 in V1 (marked as 1967). This version uses EL84's, but gives the tone stack as TG mentioned.


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## anaerobe

Here is some progress.. I have installed the tube sockets V1 - V5. V1 = 6aV6, V2 = 12AX7, V3 and V4 are 6v6 and V5 = 5Y3. Because the 6AV6 is a weird 7 pin mini socket, its smaller than a typical 9 pin base.










I used a unibit to drill the hole for the 7 pin socket:









The V5 rectifier is hidden behind the PT.








On the face far left is the standby switch, Then the 2A fuse, the on/off switch and then the lamp jewel.









And, the new sockets...









Today's jobs - wire up the heaters and test voltages. I ordered an eyelet circuit board from Hoffman amps - so I'll drill holes and test fit all the hardware in the meantime.


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## jb welder

traynor_garnet said:


> I may have the schematic for the tube rectified bassmate around. Let me look.
> TG


Any luck with this? I think you used to have it:
ISO Traynor YBA2 schematic, 5Y3 rectifier


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## anaerobe

There are so many versions. That page has a schematic for a EL84 powered, ss rectified, bass and treble control variant with a 12AX7 in V1:


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## traynor_garnet

And viola!


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## cboutilier

Since this isn't a true exact clone, why not replace the 6AV6 with a 12AX7?


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## traynor_garnet

cboutilier said:


> Since this isn't a true exact clone, why not replace the 6AV6 with a 12AX7?


 One great reason is that you can buy NOS 6AV6s for dirt cheap and they sound great. Of course, 12ax7s are easier to source so there are pros and cons.


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## anaerobe

traynor_garnet said:


> One great reason is that you can buy NOS 6AV6s for dirt cheap and they sound great. Of course, 12ax7s are easier to source so there are pros and cons.


Cost: Yes! I bought 4 NOS RCA 6AV6 for twelve $CDN, from a local gent in Winnipeg.
Intangibles: The 6AV6 tube is quite rare in its usage in guitar amps, and its a big part of the gestalt of the early Bass Mate.
Engineering: Lots of amps don't use more than one triode section in V1, and the 6AV6 fills the single triode, high gain requirement. They can be swapped for the 6AT6 for less gain IIRC.
Historical POV: The YBA-2 owes much to the 5F10 Fender schematic both used these weird little seven pin tubes.

*Thanks TG for the great schematic!! *Its a beautiful resource on the web and for the CDN community. A "eureka" moment for me, anyway.


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## jb welder

Thanks TG.
Not meaning to gripe, but that's not an official Traynor drawing, so I guess a factory schematic does not really exist.
Someone has edited in the rectifier section (different font) and dated it 2009. (Don Doucette?)

It's greatly appreciated and is most likely accurate, I was just real curious about the history of the rectifier version.


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## anaerobe

Progress:

It Lives! I wired up all the heaters from the lamp, a la early tweed style wiring approaches. The final volts reading on the loaded heater circuit (taken at V1 pins 3 and 4) was 6.8 VAC... a little high, but good enough for me.



Below is a darker shot to show all those nicely glowing heaters. A big difference from the 12AX7 and 6AV6 tubes is that there is no tap to supply two heaters. Just a single pair of pins used for the single triode. The particular 6AV6 shown is an ancient Marconi.


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## cboutilier

anaerobe said:


> Cost: Yes! I bought 4 NOS RCA 6AV6 for twelve $CDN, from a local gent in Winnipeg.
> Intangibles: The 6AV6 tube is quite rare in its usage in guitar amps, and its a big part of the gestalt of the early Bass Mate.
> Engineering: Lots of amps don't use more than one triode section in V1, and the 6AV6 fills the single triode, high gain requirement. They can be swapped for the 6AT6 for less gain IIRC.
> Historical POV: The YBA-2 owes much to the 5F10 Fender schematic both used these weird little seven pin tubes.
> 
> *Thanks TG for the great schematic!! *Its a beautiful resource on the web and for the CDN community. A "eureka" moment for me, anyway.


I do love how cheap 6AV6 tubes are. I have a single 6V6 powered Pepco head that has two of them in the preamp. My only fear is that the supply of 7 pin tubes may eventually dry up. If they were available in new production I think you would see a lot more of them in use.


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## traynor_garnet

jb welder said:


> Thanks TG.
> Not meaning to gripe, but that's not an official Traynor drawing, so I guess a factory schematic does not really exist.
> Someone has edited in the rectifier section (different font) and dated it 2009. (Don Doucette?)
> 
> It's greatly appreciated and is most likely accurate, I was just real curious about the history of the rectifier version.


I'm not sure who exactly did the schematic but I've never seen another with the 6AV6 V1 or tube rectifier. More than one tech I've used has worked with the schem and didn't note any problems or errors. I think somebody sent this to me way back years ago via the Yahoo group. 

As for the history of the tube rectifier units I cannot say much outside of noting they are rare and were only produced at the very beginning of the model.


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## anaerobe

traynor_garnet said:


> I'm not sure who exactly did the schematic but I've never seen another with the 6AV6 V1 or tube rectifier. More than one tech I've used has worked with the schem and didn't note any problems or errors. As for the history of the tube rectifier units I cannot say much outside of noting they are rare and were only produced at the very beginning of the model.


Rare and lovely.

My circuit board just arrived from Hoffman amps. Doug Hoffman drilled out the board for me, really nice quality material. More pics soon.
If anyone has a used CTS 15" driver with the square back (60's) for sale, please let me know. 

Ian


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## anaerobe

Progress!

I populated the new eyelet circuit board. This is a layout that is close to the 5F10 Harvard circuit. My plan is to go through the Traynor schematic provided in this thread and make changes until I think I can do justice to the YBA-2 specs.

Three 68 k resistors on the upper right side of the board are rigged for 3 inputs which is something I will retain from the 5F10 circuit.

A small change I made in "Traynorizing" the circuit includes losing the fixed bias selenium diode set up (? - weird) on the left hand side of the board (far left in this picture) and replacing it with the YBA-2 spec 250 ohm resistor and a (in my case, 22 uF) cap. I used a big 10 watt resistor just like many of the vintage Traynors I've seen. The Fender-spec selenium diode is a real odd-ball, and when they wear out, is sometimes replaced with a 1N4007 diode.

I will Traynorize further, including the resistor layout. I need to be cognizant and tread lightly here, as the B+ voltage between the two designs (e.g., YBA-2 vs 5F10 Harvard) is very different. The Traynor is around 380 V or so according to the schematic; the Harvard was a measly 305 V. My PT puts out about 325V so hopefully I'm the goldilocks equivalent. Lots of variables to control in this attempt at emulating Traynor.

Resistors:
In the power section, the 5F10 circuit has a 22 k voltage dropping resistor after the first 4700 ohm resistor, and the YBA-2 calls for a 10 k resistor.

Observation: The YBA-2 set up keeps the circuit behind it at a higher voltage than the 5F10 - which may emphasize cleans. But this is not a clean amp... hm. More below.... 


This is the board set up for the YBA-2 specs - with a fender-style layout.


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## anaerobe

*1. Circuit comparison - Tuning the V1 gain and distortion of the Bass Mate 
or
What Traynor may have been thinking with this circuit.*

V1 is often said to be the most important tube in the preamp stage. Everything it does is pushed downstream through the circuit.

Something I found:

"Lower supply voltage & lower plate resistor value --> lower gain (volume), less headroom, higher distortion.

Higher supply voltage & higher plate resistor value-->higher gain, more headroom, lower distortion.

The tables on page 3 of the datasheet below are revealing…."

http://www.mif.pg.gda.pl/homepages/frank/sheets/010/e/ECC83.pdf

So, for a 12ax7 tube (functionally a doubled up 6AV6), from that table (beautiful!) –

- the original 5F10 circuit the cathode resistor is up around 1500 ohms, then gain (volume) is relatively low, and distortion is on the higher side.

- the 5F10 runs a 1500 ohm cathode resistor on V1, whereas the 5E3 (for example) runs an 820 ohm cathode resistor – the latter gets more gain (volume) from V1.

Edit - looks like the anode and cathode resistors to V1 of the Harvard and the YBA-2 are identical... a good thing. No mods required.

+++++++++++

*Circuit comparison # 2. NFB or no NFB*

The 5F10 fender has a negative feedback circuit. It fed into the single speaker jack and consisted of a couple of resistors in series.

BUT

The YBA-2 does not. Nada. (Probably this helps to contribute to its unique tone).

So... I'm debating whether to leave the NFB installed on the board but unconnected or perhaps wire it up and make it switchable.

What do you guys think??? Let me know.


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## jb welder

Most people who try the NFB on a switch either like it or not, and leave the switch in one position. So I would say try it with a clip lead and hardwire it whichever way you like, no switch needed.


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## anaerobe

jb welder said:


> Most people who try the NFB on a switch either like it or not, and leave the switch in one position. So I would say try it with a clip lead and hardwire it whichever way you like, no switch needed.


Sounds good.. I have wired everything thing up to give it a go. If I don't like it I'll clip it at the board.

Progress:

Here is my version of the YBA-2 board, with flying leads and soldering done. To get the cathode bias segment done, I copied a bit of the 5E3 circuit. While the original Traynor used two boards, I stuffed everything onto one board. BTW the Hoffman board is a really nice to work with.

Home-cooked Bass Mate circuit (top)



Bottom with hidden wiring


I roasted the right side of the tong holding the board. As my grandfather said to me once,

"Sonny, you've got the touch of a blacksmith." 

The butane fired iron that I use gets hella hot.


Edit: My OT arrived this week - a Hammond 1750E shipped from Next Gen Guitars in Ottawa.
Fast shipping.

nextgenguitars.ca


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## anaerobe

Progress - The OT went in this weekend.



Then I realized that I was going to likely move V1 and V2 over to put them proximal to their matching leads from the board.

So I cut two more holes for those valves. Ugh.... not big into re-dos... and the chassis is beginning to look like a dog's breakfast.



Test fitting the board.



Here's another pic of the OT, showing where the original location of V1 and V2 were... that plan is now toast.



V1 and V2 are now right shifted beyond the OT and beside it, respectively.

Now I can finally install the Volume and Tone pots, and wiring the whole thing together (thinking of referring to these controls as "Balls" and "Grit")... 

I need to spend some time getting the wiring tidy.

Then test voltages... then.. the moment of truth.

I also need ideas for a clone name for this little YBA-2...

The...

- No Braynor
- '66 YBA-2
- Little Big Man
- (Paper) Chase Mate
- Single Tee Special (triode)
- Resurrector
- El Gordito
- Y Not Eh Too

Fire away with your ideas, I'm open to suggestions...


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