vintageHIWATTconvention.com

I think it looks great! Lots of stuff going on in that one.

The Fender guys are big on signal cap burn-in. Seems odd no one has marketed "pre burned" caps yet.

Dave

It's a bit more complicated than a DR103 or DR504, but not terribly so.

I am excited about the new PT's with 120v, 225, and 240v. taps. believe it or not, this new PT actually simplifies and unclutters the biggest busy/messy spot in the amp pictured.

It sounds F'ing awesome with the HT2121, and the HT4122 prototype.
It sounds best through the 4x12 when really pushed, as the output is a bit on the small side when mated to a 300w. cab.

I can't wait for you to come out and try it!

Is there an optocoupler? I haven't seen it on any schematic

Dr. Hiwatt just take it slow and don't rush

Yeah, Mark opted for an optocoupler help make for a more quiet switching mechanism.

Dr.HIWATT wrote:Yeah, Mark opted for an optocoupler help make for a more quiet switching mechanism.

Ahh, very interesting, bravo

Dr.HIWATT wrote: I can't wait for you to come out and try it!

Looking forward to it! Just have to get this pesky move and house sale behind us.

Dave

I'd love to mod mine to use an optocoupler...is there any way to get the instructions without the kit? The regular switching mechanism, where the signal travels down that looong wire, really makes for a lot of noise when the footswitch is hooked up and it's running with full gain.

I don't know how you would go about doing it with your current PT.
Ours has a low voltage tap to power that circuit.

Maybe Mark could work around your set up?

Would be cool if it could be done...but if it's done on a separate tap on your PT it might not be possible with mine.

shakti wrote:Would be cool if it could be done...but if it's done on a separate tap on your PT it might not be possible with mine.

Maybe you could use a voltage divider to lower voltage?

It would be a little tricky, since you need a few mA at a fairly low voltage. Getting this from a 450v supply would be difficult and inefficient. You could always just add a small filament transformer.

--mark

> 22uF
I shake my head when people worry about these things, like 16+32 vs. 32+32. The amount of capacitance in the power section has a major effect on the tone, but once you get to the preamp, adding more capacitance only reduces hum, it does not affect the tone in any other way...IMHO.

--mark

Not sure if I necessarily agree with that...the difference between 16+32 and 32+32 is veeeery subtle, true...at least compared to the very stiff filtering of the power stage. In Marshalls though, with much less overall filtering, the difference between 16 and 32 can be quite noticeable. It's a "feel" thing more than a "sound" thing though.

But in the case of a Hiwatt I guess you're right.

I'm looking forward to a 100 JP kit