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Discussion Starter #1
Bill,

Thought you might have some insight into what mods or tweaks can be done to a YBA-2B combo for guitar. I decided to pull the trigger on this amp based on reviews and my desire to own an old Traynor. I'd be very interested in what can be done to it to make it into a rockin guitar machine. Some people say this thing already rocks your socks off and breaks up early on the high channel, other people say it needs a cap job or a few values changed before it really smooths out. I was interested in your take on this and what you would point out in the preamp part of the circuit or value wise anywhere else.

Thanks!:rockon2:
 

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Bill,

Thought you might have some insight into what mods or tweaks can be done to a YBA-2B combo for guitar. I decided to pull the trigger on this amp based on reviews and my desire to own an old Traynor. I'd be very interested in what can be done to it to make it into a rockin guitar machine. Some people say this thing already rocks your socks off and breaks up early on the high channel, other people say it needs a cap job or a few values changed before it really smooths out. I was interested in your take on this and what you would point out in the preamp part of the circuit or value wise anywhere else.

Thanks!:rockon2:
Hey KP! This is going to be fun!

First off, there were FIVE different versions of the BassMate! I've never found a schematic that says exactly "YBA-2B". So we need to know a few things, like does your amp use 6V6's or EL84/6BQ5 tubes in the output? Do you have two 12AX7's or just one 12AU7 before the output tubes?

The plate resistors on the phase inverter 12AX7 that drives the output tubes, are they both 100k or is one of them the traditional blackface 82k?

I need to know specifically what we have to work with. Some models only used half of the 1st 12AX7, which means it's still there for us to hook up.

If you go to http://www.schematicheaven.com and find the file for YBA-2BUsersmanual it contains 3 of the schematics. The file "YBA-2x" has the rest. We need to compare them to yours and find out which is a match. There may still be a couple of minor differences. Pete often changed things faster than someone could update the schematics.

Whatever, I would lean towards the YGM-2 GuitarMate circuit. Is yours the one with fixed bias instead of using a bigass cathode resistor? A switch on the back to toggle between the 2 modes would be fun!

Tell me what we need to know so that we are working from the same page and let's get started! There are notes to play and apartment leases to break!:rockon2:

:food-smiley-004:
 
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Can beg you two to keep a running record of this conversation here on the board? This is fascinating. :smile:
 

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Discussion Starter #4
Well, I will have to wait to get it but in the meantime I can ask the seller to look at the year it was issued and can compare based on the schematics (which I downloaded). I know it runs the EL84/6BQ5 tubes in the output stage and there are 2 12ax7 in preamp. I am pretty sure that with the combos, both halves of the first 12ax7 were used but again, we won't know till i crack it open and look at that as well as the other questions you have asked! I don't mind documenting it for everyone this forum either. It looks to be a fairly simple layout with a ton of room to work in. (unlike that damn weber which had no room to work in - sounds great though). I'm still a beginner builder but the stuff you asked made sense to me so there is hope after all for me to become an amp guru one day :)
 

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Discussion Starter #5
Ok back for the attack.. got the mp in hand and its inners are in good shape as well as its exterior cosmetics... When i cranked it, it had a bit of raspy distortion... broke up, but nowhere as full as I would like. So with that, here I am with the answers to your post Wild Bill:

2 (EL84)/6BQ5 tubes in the output. There are 2 two 12AX7's in the preamp stage, both halves of the preamp stages seem to be used as there are wires going to every pin.

long tail pair - 3 to one resistors in the PI are 3 470K resistors.Where would the plate resistors be here?I have tried researching but it is a confusing subject and visually i don't get it. Building an amp was easy, just followed the schema and layout but knowing what is what by name is hard for me.In theory should it not run off one of the pins of the 2nd 12ax7?

Looks to be fixed bias with no trimpot anywhere. There is also a diode in place here like the YBA-1A has.

Sorry I cannot be more specific , I am rusty!
 

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Ok back for the attack.. got the mp in hand and its inners are in good shape as well as its exterior cosmetics... When i cranked it, it had a bit of raspy distortion... broke up, but nowhere as full as I would like. So with that, here I am with the answers to your post Wild Bill:

2 (EL84)/6BQ5 tubes in the output. There are 2 two 12AX7's in the preamp stage, both halves of the preamp stages seem to be used as there are wires going to every pin.

long tail pair - 3 to one resistors in the PI are 3 470K resistors.Where would the plate resistors be here?I have tried researching but it is a confusing subject and visually i don't get it. Building an amp was easy, just followed the schema and layout but knowing what is what by name is hard for me.In theory should it not run off one of the pins of the 2nd 12ax7?

Looks to be fixed bias with no trimpot anywhere. There is also a diode in place here like the YBA-1A has.

Sorry I cannot be more specific , I am rusty!
Hey KP! This is starting to help!

The plate resistors that are important are the ones used for the phase inverter, which would be the last 12AX7 in the string and the one that feeds the output tubes. They would be attached to pins 1 and 6. They might be 82k and 100k, or both 100k or even 47k.

Actually, if we can't absolutely indentify the model it really doesn't matter. You've got all the pieces to change the amp to a YGM 3 Guitar Mate! Just get the right schematic and make all the small part changes.

In fact, your amp will likely then sound BETTER than a Guitar Mate! Pete would have used an output transformer beefy enough to handle those low bass notes. The lower the frequency limit in an OT the more iron and size it needs to do the job. That's just physics. So your converted Bass Mate will have a much better low end response than the standard Guitar Mate.

We're getting there!

:food-smiley-004:
 

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Discussion Starter #7
From 1st pin of second 12AX7 - 100 K resistor which feeds into a .10 uf cap
From 6th pin of second 12AX7- 82 K resistor which feeds into the 100 K resistor and another .10 uf cap.

So this is the phase inverter porion of the circuit eh? Interesting.

so would you then suggest that i find the YBA-2B schematic that corresponds to this and A/B it with a guitar mate schema in this same section and do some swapping?

:banana:
 

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Can beg you two to keep a running record of this conversation here on the board? This is fascinating. :smile:
Ya I am interested as well.

I got my YBA-2A with plans on modding it. As soon as I plugged it in though, I realized I probably didn't need to. I like how it sounds stock better then I liked the YGM-3 I had....and it sounded great!

The only thing I would like to change is the bass on it. It's got a fantastic bottom end, but I basically have to play with the bass dialed down to 1 on the knob. It would be nice to have a little more play there.
 

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So your converted Bass Mate will have a much better low end response than the standard Guitar Mate.
I can echo those sentiments as well. My YGM-3 had a nice clean sound but my Bass Master is closer to the sound I was looking for.

I got my YBA-2A with plans on modding it. As soon as I plugged it in though, I realized I probably didn't need to. I like how it sounds stock better then I liked the YGM-3 I had....and it sounded great!
Couldn't have said it better, my sentiments exactly. I plan on building a cab and going with a 12" Weber.
 

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I mainly use my Tele, and my Reverend which has Filtertrons on it. The Reverend pickups are the closest I get to humbuckers. I have a feeling the tone of the amp might be a little muddy unmodded with humbuckers. It sounds great with single coils and the Filtertrons though.
 

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I'm using Kinman Broadcasters; no pedals with Groove Tubes. I prefer JJ's but at the time GT's were all I could get. They actually sound pretty good. Btw, tdu, could you possibly post a pick of the back of your amp. I'd like to see the shape of the rear panel. Mine is missing and I'd like to make one. Thanks.
 

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brian, my camera is at work right now. I will bring it home next week and snap some photos for you.

I saw your post about this in another thread, but I thought you had the combo version.
 

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Discussion Starter #16
Bill, did you have a chance to see my last post on the YBA-2B and what mods I should proceed with? I was intersted in a bit more guidance and wondered what your thoughts might be.

Thanks!
 

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Bill, did you have a chance to see my last post on the YBA-2B and what mods I should proceed with? I was intersted in a bit more guidance and wondered what your thoughts might be.

Thanks!
Even simpler, KP! It sounds like your amp has everything you need to convert it to a Guitar Mate. I would get a GM schematic and change the entire preamp.

You'll find that the output stage and power supply will need little or no modding.

As I had said, I think that a converted BassMate will sound BETTER!

:food-smiley-004:
 

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Discussion Starter #19
Thanks, I'll have a look. Is there a particular version of the guitarmate or model that I should look to? Is there as much variance with his guitar amps as there was with the bass amps? I suppose the best way would be to head on over to schematic heaven and have me a looksie.
 
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