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This amp was built from a kit and the workmanship seems to be decent, but what is strange is how tiny the heyboar (partridge style) transformers are. They are like minitures compared to a Hiwatt or Sound City amp. The power transformer is about the same size as the output. I suppose as long as it can supply enough current to drive the heaters and tubes I shouldn't worry, but the question is; Is this typical for the kit build?

The other odd thing is; when the amp is in the boost mode, the tone is much like a half cocked 'wah-wah' pedal. In other words, it has a real nasally tone to it. This is somewhat evident too out of boost mode, but not as noticable. I'm running the Chinese KT66 tubes that came in it and was thinking of getting rid of those first in favor of some EL33 or 6L6s if the transformers can drive them.

Finally, are there schematics available online? I'd like to jumper the boost switch to the rear jack so I can turn it on and off via a foot switch.

Overall, the tone is pretty nice and I think the amp has a ton of potential. I'd just like to get the EQ leveled out a bit better.

Thanks in advance for any info!

Here are a few pix

You can find the schematics in the Resource section
viewtopic.php?f=12&t=1567.
Stew

Not sure what you mean by the undersized transformers but that iron is very large for a 20W amp. The prototype went through a bunch of different transformers before that set was picked.

The Triwatt isn't an exact Hiwatt clone, just something to keep in mind.

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http://pdfelectronics.com

The Transformers are 50 watt capable, same size as original partridge 50W. Are you comparing to the 100 watt models?

Stock, this amp can run 6V6 or KT66. No one has ever called it nasally. The TRIWATT shows every nuance, so tubes can make a big difference. Best to try Tung Sol or Mullard RI, Jan 12AT7 in PI and good 6V6s. You must rebias for 6V6.

See docs in the resource section. Seller had full manual and schematics / layouts.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Awesome!! Thanks for the schematic and layout link!

Yeah, there is something odd going on with the amp in boost mode. It sounds exactly like a wah pedal that is about half way in the sweep. Maybe nasally is a poor term, but it's not a natural sound. I'm running Tung-sol reissues in the preamp and phase inverter. I have a 12AT7 Mullard tube I can try.

I tried some JJ 6V6 tubes yesterday. With the bias switch in the 6V6 position I had 437dcv on the plates and the current maxed out at 32mA ( at the end of the pot sweep). I checked the amp bias reading with my bias-rite and they both agree, so that's a good thing. So unless there is something I don't understand in setting the current via a VOM in the voltage mode ( conversion factor? ) ... it seems the sweep should allow me to go beyond 32mA. It makes me wonder what the KT66s were running at that came in the amp considering the plate voltage is probably 450-460ish? , I'm betting it was impossible to set the bias properly on those tubes. I may have to check those bias resistors. This was a kit built amp, so obviously there is room for error, I just have to debug it.

Regarding, the size of transformers. I was comparing to a 100W DR103 ... and I've never owned a 50W Hiwatt... so, my mistake.


Thanks for the good info and help !!

No, but it's *very* close to being one, apart from the different output tubes. The preamp is a hybrid of two different vintage Hiwatt preamp designs, so even in that respect it's still pure vintage Hiwatt DNA. So it's kind of a Hiwatt model they never actually built.


I believe you've got some positive feedback inside the preamp when running in boost mode. The gain level with the Overdrive on is up in SLO100 territory. Putting in a 12AT7 is a band-aid and will somewhat defeat what the Overdrive is for. The right way to fix this issue is to work on the lead dress and use shielded wire for the longer signal connections.

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Great tones come in small glass jars!

+1 to what Zaphod said. The overdrive section of this amp is VERY sensitive to lead dress issues & also outside interference. There's a lot going on there signal wise in a very tight space. In mine, IIRC, I used a shielded wire for the "hot" signal going from the board to the OD switch/pot (or was it from the vols to the switch/pot?) & that cured most of my issues. It still took some wire twiddling to get it just right. Once I did that & got it in the cab with the bottom shielded it became perfectly stable.

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SG + Brit tube head = Nirvana

The amp is whisper quiet at idle and that's something I don't want to mess up. Usually wire routing is more of a noise problem than a tone coloration issue, but who knows, stranger things have happened. I was thinking more along the lines of a RC value is wrong or has too loose a tolerance maybe in the tone stack? I'll dig into it more and see what I can find out.

Here is another thing that I don't know if it's right or not, but when the boost switch is pulled out, the jump in volume is huge unless it is dialed back to around 8 or 9 oclock. Does that sound normal or should it be more moderate?

Boost is very sensitive, around 1/4 to 1/3 works pretty well. OTW, you just set it up to what you want and run with it and dont switch on the fly.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps