My Trinity OSD Kit Build

[Matt J]

Update:

Due to a kidney stone attack (something I would never wish upon anyone!) I had to take a break from the amp for a bit.

I've tested the amp some more. I can't really make any judgments on the tone just yet since I don't have the combo cabinet it is going to be housed in just yet. As for now, I've been running it on my work bench with the speaker sitting behind it, cone facing down. Obviously this isn't the optimal way to hear the amp, so I will see how things go once I get everything installed in the cabinet.

I have noticed a noise issue, potentially caused by a grounding problem. The amp is buzzy, particularly with my Les Paul. You do hear changes in the buzz as you move your hand around or above the amp's chassis as it is running. I'll try testing wires with chopsticks soon to see if this changes anything, but I am cautious about the relay board wiring. I notice on original Dumble amps, the relay and footswitch ground all attach to near the relay power supply at the top left corner of the chassis (when looking down and towards the control pots). With Trinity's OSD, the relay power supply and footswitch both ground at the same preamp ground point since the relays are powered by 5v tap from the PT. The power supply and rectifier are all built into the relay PCB board. Should I perhaps reroute were these ground points go?

There's also the possibility that my house could be causing some of the noise. This house is old, built in the 1940s, and there is the chance that the ground wiring could be a little suspicious. I may take the amp chassis to my uncle's house and see if the same issues persist there.

I'm posting a lot of close up pictures of the build. If anything stands out as odd, or if you see a wire I should move to prevent noise and oscillations, please feel free to point it out!
- Matt J.

[Matt J]

I have decided to replace two things:
The 250Kl trim pot on the back of the amp. The taper just seems off for some reason and, as wired from the layout, it seems to work backwards. (Full clockwise shuts off the OD, full counter-clockwise provides max gain). I've ordered a 100Kl replacement so it is closer to the actual value of the internal trim pot from #124.

The 1uf tantalum presence cap seems to have very little effect, so I'm going to try a 2.2uf replacement.

[Matt J]

More closeups

[Matt J]

More

[Matt J]

Last ones

[67plexi]

The trim 250k pot is wired backwards use coax It kind of burns my A$$ I started that extra pot on the back of the amp 10 years ago.

001 (2).JPG

[67plexi]

I don't see a filter choke just a 500r resistor how about a top chassis photo.

[Matt J]

I don't see a filter choke just a 500r resistor how about a top chassis photo.

Yep, no choke. Just the 500r. This kit does not include a choke, but I am willing to consider adding one in if it will benefit the tone and lower any noise.

[erwin_ve]

The filter caps for both V1 and V2 are grounded at the earth point near the input jack on #124.
I'm sure your V2 filter ground is somewhere else, I'm not sure on V1 filter ground. Where is it grounded?

[Matt J]

The filter caps for both V1 and V2 are grounded at the earth point near the input jack on #124.
I'm sure your V2 filter ground is somewhere else, I'm not sure on V1 filter ground. Where is it grounded?

V1, V2, and V3 filter caps all ground to the same point, a ground point just above the PS board labeled "PW2" on the layout.

Here is an overhead shot of the bottom of the chassis. I noticed that the transformers (when you install them per the corresponding holes in the chassis) are not installed with the bell ends perpendicular to each other, as I see in most amps. I've read this can cause noise issues, but I'm not certain. With my caliper I measured about a 2.6 inch/66 mm distance between the ends of the two bells.

- Matt J.

[pompeiisneaks]

The filter caps for both V1 and V2 are grounded at the earth point near the input jack on #124.
I'm sure your V2 filter ground is somewhere else, I'm not sure on V1 filter ground. Where is it grounded?

V1, V2, and V3 filter caps all ground to the same point, a ground point just above the PS board labeled "PW2" on the layout.

Here is an overhead shot of the bottom of the chassis. I noticed that the transformers (when you install them per the corresponding holes in the chassis) are not installed with the bell ends perpendicular to each other, as I see in most amps. I've read this can cause noise issues, but I'm not certain. With my caliper I measured about a 2.6 inch/66 mm distance between the ends of the two bells.

- Matt J.

You should absolutely rotate one or the other, they should be done that way to avoid coupling. it 'may' be far enough away but it will still induce some hum/sound if you have them too close and not off axis by 90deg

~Phil

[Matt J]

The filter caps for both V1 and V2 are grounded at the earth point near the input jack on #124.
I'm sure your V2 filter ground is somewhere else, I'm not sure on V1 filter ground. Where is it grounded?

V1, V2, and V3 filter caps all ground to the same point, a ground point just above the PS board labeled "PW2" on the layout.

Here is an overhead shot of the bottom of the chassis. I noticed that the transformers (when you install them per the corresponding holes in the chassis) are not installed with the bell ends perpendicular to each other, as I see in most amps. I've read this can cause noise issues, but I'm not certain. With my caliper I measured about a 2.6 inch/66 mm distance between the ends of the two bells.

- Matt J.

You should absolutely rotate one or the other, they should be done that way to avoid coupling. it 'may' be far enough away but it will still induce some hum/sound if you have them too close and not off axis by 90deg

~Phil

Thanks Phil!

I'm really leaning towards that now, and redoing some of the grounding. In fact, I'm considering pulling out the current OT that was supplied and replacing it with a 50w 2x6L6GC OT from Classictone and reworking things from there. Having tried it with the 6V6s, they seemed just a little too mushy to me when the master was up. It was interesting that they included this option with the kit, but I prefer a cleaner 6L6 sound on these types of amps.

- Matt J.

[Matt J]

Oh, and I just noted a major goof I made too...

I replaced the bias probes recently with some from Hoffman, since the ones included with the kit had really really large probe attachments that did not fit either of my DMM probes. Looks like I forgot to solder back into place the wire from the pins 1 + 8 jumper on V4 to the bias probe point.

Well, time to warm up the soldering iron!

- Matt J.

[pompeiisneaks]

Good catch! I keep finding things I've forgotten or done wrong on my current dumble build. I hope I find them all before power on

~Phil

[Matt J]

Good catch! I keep finding things I've forgotten or done wrong on my current dumble build. I hope I find them all before power on

~Phil

It's certainly not the first goof I've made!

I've really enjoyed your build videos on YT too. I can't wait to see how it goes when you power it up! I need to catch up on some of the recent live streams. That kidney stone knocked me out of commission for a bit.

- Matt J.