Guild Thunder T1-12

[fearless]

Thanks Gazza. Yep, I use a step-down transformer at the moment to power the T-1. It would have been too good to be true if you'd had a spare 240V input trannie to suit.

This might be a silly question (and it is certainly a veer), but do you happen to know a Guild-interested amp tweaker in Melbourne?
Reason I ask that in the 5 or so years that I've owned them, I've never gotten around to fixing up either of my T-1s. I'm thinking that maybe the right person would fix both for me in return for keeping one.

It may be obvious that I am not a retired man...!

 

[coastie99]

Thanks Gazza. Yep, I use a step-down transformer at the moment to power the T-1. It would have been too good to be true if you'd had a spare 240V input trannie to suit.

This might be a silly question (and it is certainly a veer), but do you happen to know a Guild-interested amp tweaker in Melbourne?
Reason I ask that in the 5 or so years that I've owned them, I've never gotten around to fixing up either of my T-1s. I'm thinking that maybe the right person would fix both for me in return for keeping one.

It may be obvious that I am not a retired man...!

Are you kidding ??

I don't even know where Melbourne is !! :lol: :lol:

But seriously, no. I'm sorry I don't.

 

[fronobulax]

Chairman Meow says .. "Never feed your cat anything that doesn't match the carpet "

Just noticed that and I am pleased to report that all of the coffee i sprayed was cleaned up before the computer was damaged. Thank you.

 

[coastie99]

Chairman Meow says .. "Never feed your cat anything that doesn't match the carpet "

Just noticed that and I am pleased to report that all of the coffee i sprayed was cleaned up before the computer was damaged. Thank you.

So long ?? Frono, you are a disappointment to me !!

 

[Csquare4]

Some additional insight into the output transformer -

I disconnected the OT and wanted to try and figure out the Impedance that the tubes would be seeing reflected back from the speakers with the 8ohm load. Interestingly, the output has a series 120 ohm and 0.1uF in parallel with the speaker outs, which I suppose is there for rolling off the low frequencies hitting the speaker. Dunno.

So, I found out that the turns ratio N=33.2, so the Impedance ratio of the OT is Z=1100 (approx). With an 8 ohm speaker load, the reflected impedance into the tube is 8.8k ohms - which seems entirely normal for most power tubes, but not the 6WG8's...which according to the tube data sheet is looking for about 48k ohm. So, either this is horribly mis-matched, which means it would probably be better matched with a 16 or 32 ohm speaker load, or the RCA tube data spec sheet has a terribly important typo on it.

After much, and I mean much, head scratching over this one, I think I have read every entry on the whole dang world wide web that may pertain to a 6GW8 tube. Finally, I came across an interesting Mullard design for a 10W amp using this tube in a push-pull configuration. Which really looks like a cool audio amp, btw. But regardless, according to the BOM and specifications, the output transformer they use has a 9kOhm primary. This matches up exactly with what I measured, so all is well in the world. For one night anyways. Here is a schematic for anyone interested. Also, a pretty good write up and description of this amp is here. I may actually build one of these, looks pretty sweet.

Craig

 

[capnjuan]

... Finally, I came across an interesting Mullard design for a 10W amp using this tube in a push-pull configuration. Which really looks like a cool audio amp, btw .... I may actually build one of these, looks pretty sweet.

That Mullard design uses the EF86 found in Vox designs and is line-stage only.

With an adapter, could pipe in an MP3 player ... that'd be fun!

 

[Csquare4]

**Update**

I found some NOS Siemens 6GW8's and replaced all the electrolytics, including the 4x40uF can cap which I found a direct replacement at AES, as well as the power supply resistors. After doing the work, I powered it up and have been playing it for a few days now. I am liking the tone...obviously, its pretty limited as far as features go, but I have found some settings that respond really well with my S100 and M75.

Basically, 3 o'clock on Bass and Treble, Bright "off", Trem "off" and this sounds really good at very manageable volumes. Nice warm break up starts coming into play at about 1 o'clock on the volume, then by just past 3 o'clock it is well into saturation and sounds fantastic. The circuit is very quiet, virtually no hum.

Speakerwise, it still has the stock Guild CTS speaker, which actually starts breaking up as well and adds a bit of character to the sound, much like my vintage 10" Celestion 7442's. Kind of a "barky" dry distortion on top of the tube saturation. Not sure if I want to change this out or not now. Maybe I will do a swapout to at least find a reference, but seriously, at the volume this thing is pushing, these actually sound pretty decent.

The tremolo still sucks a bit of the tone, I am not real impressed with that, but I haven't done any mods to that part of the circuit. I will probably go in and change all the resistors/caps there at some point to see if it helps, but I don't use tremolo much, and without a foot-switchable option, probably wouldn't use it at all since I have other amps that do (such as my super-sweet Traynor 4x8 StudioMate - love the tremolo/reverb on that thing!).

So for about $250 all in, I have gotten a great little practice amp...not something I am going to haul over to one of our jams as there is absolutely no way this will keep up with our drummer. Best part, the wifey isn't throwing shoes at me to turn it down.

Craig

 

[capnjuan]

... So for about $250 all in, I have gotten a great little practice amp ...

Hi Craig; thanks for looking into the OT question. Without your checking it out, I and maybe others would have continued to believe that the 6GW8s/T1 OT were something of a technical dead.

If you get a chance, think about posting a sample of what the amp sounds like; I and I'm sure others would like to hear it. John

 

[Csquare4]

... So for about $250 all in, I have gotten a great little practice amp ...

Hi Craig; thanks for looking into the OT question. Without your checking it out, I and maybe others would have continued to believe that the 6GW8s/T1 OT were something of a technical dead.

Hey no problem there John, without the threads you guys created earlier, I would not have even known where to start with this thing. There really isn't a lot of info on the web about this amp. I have been having a blast playing it. It really has some pretty good tone, unique in a way. Almost a EL84 grind with a bit of spank at reasonable volume when you open up the volume a bit. With a tube screamer in front of it, I can really churn with some nice lead tones. Maybe it's just "new" and I am infatuated with it for now, but I am digging it.

If you get a chance, think about posting a sample of what the amp sounds like; I and I'm sure others would like to hear it. John

Ha ha...well, others may want to hear it, but I am not sure they would want to hear *me* play it! I will see if I can get something up soon.

 

[Default]

I'd like to hear it! I have a chassis sitting waiting for some tubes and I'd like to hear what it'll sound like before I convert it to 6bm8's. :wink: