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PostPosted: Sat Dec 07, 2019 3:32 pm 
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mitch m wrote:
The voltage at the cathodes of the preamp tubes is very low, around 1 or 2 volts. So electrolytic capacitors rated at 50 volts would be suitable.


Ahh, yes, now why didn't I realize that? :) Typical electrolytics are polarized, I assume the + side goes to the tube and the - side goes to ground, right?


mitch m wrote:
The way I read it, the mods suggested specify what goes on the cathode of V1.
...


Thank you again, what you wrote is what I thought was the case, just wanted to make sure. Stephen needs to get you on Trinity's payroll for all the help you've given me!


mitch m wrote:
The rule of thumb with tube amps is the voltage can vary + or - 10%. If it's 20% over at V4 pin 6 that's starting to get on the high side. The voltage at pin 1 of V4 is good so it's just variance with the tube and not a problem with your circuit. You could try a different 12AT7 there if it bothers you, but the higher voltage isn't exceeding the tube's specs so if it sounds good I wouldn't worry about it.


Awesome. I choose not to worry about it!


mitch m wrote:
Thanks for the compliment about my DR504. It was actually my second tube amp project. The first one was a Trinity TC-15 I built about a year earlier, but I had been building electronic projects for over 30 years by that time. The assembly work for the original Hiwatt amps was contracted out to an outfit in England that also did work for the British Navy. The wiring was very neat and close to military specifications. I tried to emulate that as closely as possible when I built mine. Also I started with a fairly big chassis, like the originals had, so it was easier to keep the wiring from looking cluttered.


Your wiring is a work of art.

Ah, I just figured out my excuse: if I wired my amps that neatly, it would distract from playing, because I'd just want to look at the neat work. So I did less tidy wiring to minimize distractions! ;)

Do you still have and play the Trinity TC-15? Based on the description, that should be very similar to my Dizzy30. Curious what your sonic impressions of the TC-15 are, and how it compares to your Hiwatt-style amps. I like my Triwatt, no doubt, but I feel there is something special about the EF86 channel on my C-30 clone.

By the way, I was playing on the Triwatt last night. I was still at "polite" volume, but I opened up the overdrive channel. Using the "link" input, with the overdrive engaged, literally gives three knobs just on preamp gain tweaking and tone shaping. Anyway, the dynamics of this amp allowed me to get a setting with that overdrive channel where the general tone was almost perfectly clean, but I could get some noticeable crunch if I strummed harder. So with only a minute of two of messing around, I found what I thought was a very expressive setting, allowing me to control not just volume, but overdrive as well, simply by varying pick attack. And I feel like I'm just scratching the surface of what this can do tonally.


mitch m wrote:
Here's a picture of the outside of the chassis.


Is that piece of metal between the big caps and the power tubes like a heat shield?


Hankules wrote:
In any case, sure is "priddy" (Okie for pretty).


+1 to that!


mitch m wrote:
I'm happy to answer your questions, but this is sort of hijacking Matt's post about his successful Triwatt build. I have lots more pictures of my DR504 project and I can post some of them in the Dressing Room section if anyone is interested in seeing what a Triwatt's big brother looks like.


No worries! I've been doing online discussion forums so long (starting back in the dialup BBS days, then Usenet), I'm no stranger to thread detours. Can't say I haven't caused a few myself!


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PostPosted: Sat Dec 07, 2019 9:00 pm 
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Sorry, Matt :oops: I just wasn't sure from Mitch's first pic and couldn't tell what I was seeing. Mitch, YES! Always looking for techniques :thumbsup:

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PostPosted: Sun Dec 08, 2019 5:49 pm 
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Looking at the schematics, a TC-15 is pretty close to a DC-30 running at half power. So it should sound pretty much like your Dizzy 30 with two of its output tubes shut off. I still have my TC-15 and I really like it, but I haven't played it too much lately. I also have a Trinity Tweed Deluxe that I play most of the time.

The metal piece between the output tubes and the filter capacitors on my 504 is a heat shield like the original Hiwatts had. A couple of EL34 tubes get fairly hot so it helps to keep the capacitors from getting too warm. Some Hiwatts have four EL34s so they would get even hotter.


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PostPosted: Sun Jan 05, 2020 6:29 pm 
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Hey Matt,

I am very glad to hear that my pictures helped you out.
Ultimately, that was the reason for me to document all the different steps with high-res pictures.

Enjoy your amp!


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