Tube Driver & BK Butler ?

[Amp Kat]

I have two of these in and one is bad and was wondering if anyone may have a schematic for it. The two or a little different inside and the older reportedly sounds the best. I did some simple checks and found the filaments of the tubes run on 12VAC not DC and the op-amps were +/-16.5.
The new ones I'm told are being built by Butlers son Jason and has added a mod called bias to the back and signed on the bottom BK Butler. What do you guys think of these as they are getting harder to find ?

[bulldogguitars]

free information society

Theirs a schematic of the Tube Driver On the Free Information Society. Try this link. http://www.freeinfosociety.com/elect...w.php?id=1128r

[Amp Kat]

Thanks Bulldog I didn't find them at first but after searching somemore I found the motherload Love those Migs they rock,

[Matt T.]

I went through a few versions years ago but none were the more desirable early 'non-wall-wart' version. The only one I kept was the only one I really liked...a rackmount Chandler Tube Driver. These have a Bias control and a Contour control and mine sounds much better with both controls full clockwise...if I couldn't adjust those two controls (especially the bias) I don't think I would have kept it. One of these days I'm gonna trace it because through the right amp it sounds fantastic. Very EJ-like even though I'm apparently not running it the way he does.

Try a 12AU7 in there (heck, try all sorts of tubes). In mine, with the Bias control full-up, a 12AU7 doesn't really seem to reduce the gain that much but there is less 'fuzz' to the tone and the clarity is much better...it's like I can actually hear the 'string' better. And the attack is better...it has that 'cello' quality to it that I like.

Oh yea...surprisingly quiet too.

[Amp Kat]

Man everything you just put in that thread is exactly what I'm dealing with and the customer has done and said. He has two, one old and one new. The new one has the bias mod and the old one he says sounds better. The new one has a 12AU7 in it and he explained the pick attack just as you did I mean to the T. This guy is a touring guitar tech and a damn good one at that so I respect you guys opinions as they are spot on. After going over that schemo with the starved tube I wonder why they didn't use a Cathode follower to pull the signal as it isn't really amplifying anything. The heater are AC and can easily be DC'ed but as you say is pretty quiet. I still have some more tinkering to do and I appreciate the reply. I'll post back soon.,

[David Schwab]

I have an old BK Butler Blue tube, and that also sounds great with an 12AU7 in it. It came with an AX7, but it doesn't have enough output without totally fuzzing out. Also the output impedance seems too high, and it gets loaded down by certain inputs easily.

[Matt T.]

Where did you get the schematic? From that link above? I checked around there a bit but it gave me a headache trying to navigate through it so I gave up.

PS - I heard/read that EJ has had the bias mod on his for a long time but...who knows.

[Amp Kat]

Where did you get the schematic? From that link above? I checked around there a bit but it gave me a headache trying to navigate through it so I gave up.

PS - I heard/read that EJ has had the bias mod on his for a long time but...who knows.

Yeah I got it at that link and yes had to go thru hell to get to it but theres thousands of schemo's and I'm finding several differences with this schematic but some things are a go. I read on Butlers sight that he modded or built boxes for EJ,Satch & Gilmore and the bias mod was $125 extra. I haven't scoped it out yet but will today.
Dave I also agree that the output impedance of that 12ax7 which is about 91k would wreak havok with that tone stack and the lower impedance of the AU would work better which also leads me to believe that a Cathode follower would drive that tone stack better with it's low impedance but we'll see.

[David Schwab]

I hadn't even thought about the difference in output impedance in the AU tube... I had one laying around and thought I'd give it a try, and liked it better because it had less gain. I have an AX in there now and lost the AU... I'll have to get a new one. I was trying out different tubes I had around... I have an old Sylvania 12AX7 that sounds nice.

I'm probably going to build an op amp buffer for the output. My tube knowledge is pretty basic.

[Amp Kat]

http://www.freeinfosociety.com/elect...ew.php?id=1128

Heres that link guys and this dude has everything : BTW the problem on the Tube driver is there two 100 ohm resistors instead of a fuse and a ten ohm. Still some differences in the two but very slight.

[Slobrain]

Look at the BK butler TD on Ebay

http://cgi.ebay.com/Vintage-Original...QQcmdZViewItem

Man, I had a used one of these that I paid $50.00 for in 1995, it was an 80's unit. Darn, I shoulda kept it and sold it on Ebay

Hey AmpKat, Can you reverse engineer the bias and post as I would like to see what the bias does. Maybe even build one of these.

Thanks SLO

[Andrew M]

I didn't realize they sold for that much. I have one that needs a power adaptor (the original is long gone) Anyone know the specs of the original, I think its just 12vac and 1 amp?

Thanks,
Andrew.

[Amp Kat]

http://cgi.ebay.com/Vintage-Original...QQcmdZViewItem

Man, I had a used one of these that I paid $50.00 for in 1995, it was an 80's unit. Darn, I shoulda kept it and sold it on Ebay

Hey AmpKat, Can you reverse engineer the bias and post as I would like to see what the bias does. Maybe even build one of these.

Thanks SLO

In the process as we speak just need some time to trace it out. I do know one thing from what I can see so far the mod uses pin 9(half of the 12 VAC) with two 470uf e-cap and a 470k in parallel going to it and a bias pot to vary the signal but the Cathode trace Dremeled and going nowhere which doesn't make sense so I'm wondering if maybe this is wired wrong. I'll let you know.

[Amp Kat]

I didn't realize they sold for that much. I have one that needs a power adaptor (the original is long gone) Anyone know the specs of the original, I think its just 12vac and 1 amp?

Thanks,
Andrew.

It's direct AC (no wall wart) and a step-down transformer mounted to the steel chassis. The two AC voltage wires run the whole unit after the Full wave bridge. Pretty swift circuit.

Ooops OK (EDIT) Your talking about the original Chandler which did use a wall wart. I'm thinking 12 VAC but not sure how many ma's you would need. I'll do some checking.

[Walking Eagle]

Augh, guys! Some of you would know tell me the voltage measured or + (pin 8) and - (pin 4) on the 4558?
In the schematic that I downloaded are indicated +12.5 and -13 Volts ...
Has anyone tried what happens with the 12AT7/ECC81 (like the original '80s) or 12AY7/6072A?
You hear a difference by replacing the 4558 with the TL072?

Thanks, Alex