Holland Amp

[sonicmojo]

Got the last parts! Home stretch to connect wiring, tidy up, and test/tweak. I sure hope it works out with the existing power amp section but I can replace that too if I don't like it. I'm planning to give it to my daughter for her 17th birthday.

[pompeiisneaks]

The image is too small for me to make out much. I think if you were to adjust the lead dress a bit to separate differing kinds of wires it may help, that seems a bit crazy with wires all over the map. Good stuff, though, hope all goes well!

~Phil

[sonicmojo]

The image is too small for me to make out much. I think if you were to adjust the lead dress a bit to separate differing kinds of wires it may help, that seems a bit crazy with wires all over the map. Good stuff, though, hope all goes well!

~Phil

Sorry about that small last picture, I just replaced it with a bigger version. It was before I actually attached the wiring mess. This new picture is the near final and it worked first try!

It is sounding pretty good on first test! I'll have to take some measurements over the next couple of days but it works correctly based on what I documented on the original Holland amp. The reverb is pretty sweet on this circuit. The dwell and mix controls really make it interesting.

I just need to decide if I want to make the far left pot a presence or pre-PI master control. If I make it a presence, I'll have to tap into the power amp board which I don't really want to mess with. This was a quick and dirty amp revision for about $50 in parts that I didn't already have on hand and most of that was the small scale reverb tank 9AB3C1B.

Last task with be to button it all up in the cab and redo the labels for the new controls. I was able to erase the old ones and preserve all the numbering, lines, etc. Just need to find a good way to relabel them without going full bore on a new faceplate. I may have to order some vinyl stickers or something simple and easy. Oh yes, I also need to still wire up the footswitch jack to control reverb on/off.

[pompeiisneaks]

ahh gotcha, now that looks excellent, nice work! Glad it sounds like you want it to!

And I can see that pic way better.

~Phil

[sonicmojo]

Finished up with temporary labels until I figure something better. A nice little clean amp now. Not too loud which is nice for its purpose as a bedroom amp mainly.

[sonicmojo]

Well I went at this again with a new build. This time a Princeton Reverb sized version. Everything is working well except I am getting oscillation when the reverb mix is turned up with a 12AX7 or 12AT7 or 5751 in V2. If I pull V1, I still get oscillation. If I use a 12AU7 in V2, no oscillation and reverb is still sounding good but I'd like to fix it to work with a 12AX7. Both V1 and V2 are dedicated only to reverb.

Perhaps my tight chassis is part of the issue. Does anyone see anything I can change or move? I've also attached the original layout trace from the first page of this thread again.

sonicverb1.jpg

HollandTrace.JPG

[sluckey]

I love hand drawn layouts like this. Very neat and artsy.

[joeboo88]

could it be where your blue/red reverb tranny wires are laying across v1 pin 1. maybe reroute them?
or put a terminal strip near there to re-route?

[sonicmojo]

could it be where your blue/red reverb tranny wires are laying across v1 pin 1. maybe reroute them?
or put a terminal strip near there to re-route?

Good thought but I figured it out! I had the loose tank sitting on one of the wires from my bias probe! Oops.

Only thing left is I have a slight hum coming out of V3. Changing tubes doesn't help. The reverb transformer is sandwiched in between V2 and V3. I'm fearing that may be inducing the hum.

[sonicmojo]

It seems to be a ground loop. I'm going to change up my grounding scheme a little bit and ground all the pots except presence to a point near the jack and see if that sorts it.

[sonicmojo]

Yes, grounding all preamp grounds near the input solved it.

One last strange thing. It seems the reverb tank only likes to be mounted on its side or it induces some buzz. Doesn’t matter if it is 2 feet away from the amp or not in any direction. I will probably just mount it in the head cab this way but why would this be? I’ve tried different tanks, tubes, and cables.

[joeboo88]

Glad you solved your issues. I built a sluckey deluxe reverb, and I also had to put the tanks on the side away from the speaker.
I don’t the technical reason... but am still happy it’s quiet..

[tubeswell]

Yes, grounding all preamp grounds near the input solved it.

One last strange thing. It seems the reverb tank only likes to be mounted on its side or it induces some buzz. Doesn’t matter if it is 2 feet away from the amp or not in any direction. I will probably just mount it in the head cab this way but why would this be? I’ve tried different tanks, tubes, and cables.

Could be unwanted EMF coupling between the PT and the reverb pan's output transducer. Did you try orienting the pan so that the (coupling-sensitive) output transducer end is situated furthest away from the PT?

[martin manning]

Yes, grounding all preamp grounds near the input solved it.

One last strange thing. It seems the reverb tank only likes to be mounted on its side or it induces some buzz. Doesn’t matter if it is 2 feet away from the amp or not in any direction. I will probably just mount it in the head cab this way but why would this be? I’ve tried different tanks, tubes, and cables.

Could be unwanted EMF coupling between the PT and the reverb pan's output transducer. Did you try orienting the pan so that the (coupling-sensitive) output transducer end is situated furthest away from the PT?

Sonicmojo says it buzzes even if it's two feet away, and in any directional orientation. Puzzler.

[sonicmojo]

Yes, it is a puzzle. The reverb on this is super deep so it probably would help the noise floor to tone it down a little bit. The best orientation is turned 180 degrees on its side and very near the chassis. If I keep it that orientation and move it away a foot or two, the buzz starts to appear again but is always worse when it is turned flat as normal. I know the tank pretty much acts like a single coil so I'm not looking for absolute perfection. Not worth beating myself up and just mount it the way it seems to prefer!