Guyatone TD-1 tube distortion scored on the Japanese auction

[Rambozo96]

Yet another impulse snipe bid at the wee hours of 4 am. This one’s been on my list for a while as I have a thing for Guyatone stuff, the other overlooked G brand. This is the Japanese domestic version that runs on 100v as opposed to 120 in the states so it maybe kosher to run it as is with the expense of the plate voltage being a bit higher but I may up dropper resistors just to be safe. Though not a starved plate design like most tube pedals like the BK Butler there are hard clipping diodes that I believe may be doing a lot of the leg work so I may lift the legs of the anti parallel diode pair to see what this circuit does with just the tubes.

 

[beinhard]

Interesting!
But are you sure about that schematic? The location of those diodes does not look quite right to me.

beinhard

 

[Rambozo96]

Interesting!
But are you sure about that schematic? The location of those diodes does not look quite right to me.

beinhard

I’ll have to trace it to see. I find their location questionable though I’m no expert.

 

[Rambozo96]

Additional schematics of the Guyatone unit (Westbury unit was made by Guyatone.) and the TO-2 which best I can tell is a different sounding circuit. I’ll have to trace mine to see if I can’t get to the bottom of it. I wonder if it’s like putting diodes in an opamps feedback section.

 

[Guildedagain]

Gut shots?

Here's the one I had, it's the same?

 

[Rambozo96]

Gut shots?

Here's the one I had, if the same?

Looks like the one. Was it noisy? That transformer is awfully close to some signal wired. Then again where else could they possibly put it in the enclosure lol.

 

[Rambozo96]

It still resides in Japan so I probably won’t be able to do any gut shots until next week if the gods of DHL and the US customs office smile upon me

 

[Guildedagain]

I don't remember it being noisy at all, just a bit thick sounding like most of the tube driver type pedals. I personally couldn't stand the Butler tube driver pedals, but that didn't stop me from buying every single one I could get my hands on, and usually turning them as I think it was Gilmour that "popularized" these.

Back to the Westbury, internally fused, how cool is that?

 

[Rambozo96]

I don't remember it being noisy at all, just a bit thick sounding like most of the tube driver type pedals. I personally couldn't stand the Butler tube driver pedals, but that didn't stop me from buying every single one I could get my hands on, and usually turning them as I think it was Gilmour that "popularized" these.

Back to the Westbury, internally fused, how cool is that?

Well the BK Butler ran on 12vdc IIRC so a starved plate design that some people (you and me included apparently.) don’t care much for. This Westbury runs the plates at voltages seen in a preamp stage in a amp so it would be potentially dangerous to not have a fuse. I have plans on seeing potential mods to mine. I hope they don’t end up being extremely collectible in a few years lol

 

[Guildedagain]

Gotta check out these Japanese sites, as if I didn't already have a wicked spending habit ;]

 

[Rambozo96]

Gotta check out these Japanese sites, as if I didn't already have a wicked spending habit ;]

I recommend Buyee. Please be careful with the shipping rates however.

 

[Default]

Cowboy math says 256v off the power transformer before it goes through the bridge rectifier. Schnikes!

 

[Rambozo96]

Cowboy math says 256v off the power transformer before it goes through the bridge rectifier. Schnikes!

Probably a smart idea to up the dropper resistor then. I’ll see if 47k ain’t overkill. Post rectifier would be about 360vdc which is pretty high.

 

[Default]

Maybe a zenier diode. The amp guys use those when modern voltage puts the b+ on the spicy side.

 

[Rambozo96]

Maybe a zenier diode. The amp guys use those when modern voltage puts the b+ on the spicy side.

I’ll have to look into that. Would it just be in series with the B+ or maybe set as a clamping diode?

 

[Default]

Link here with interesting stuff and diagrams.

zener diode trick to lower B+ volts

Hoffman Amplifiers Tube Amp Forum, zener diode trick to lower B+ volts

el34world.com

 

[Default]

Here are the diagrams for posterity.

 

[Default]

You will probably have to make two, because your heater windings will be too high too.

 

[Guildedagain]

I remember the Zener diodes from all my years of BSA/Triumph/Norton motorcycle ownership. Hanging from the lower triple tree between the forks with a neat looking radial fins for cooling.