trinityamps.com

There is a thread on AX-84.com and 18watt.com about doing a mod like power dampening by Mojave. I tried it and it works pretty well. I still need to try some different values , tho, just to be sure.
Here's what I did:
I put a 1meg linear pot in series between the PI's cathodes and the 820 cathode resistor. I wired it as a rheostat, one leg to center wiper and one leg to an outside terminal on the pot. Very simple and very effective. This could warrent drilling another hole in my (amp's ) chassis.

Here are the links to the threads:
http://www.18watt.com/modules.php?name= ... 927#157755

and:
http://ax84.com/bbs/dm.php?thread=295946

Try it.

LeeMo

We'd be interested in your results leemo. We're just getting into power control. Simple is always best.

By "it works pretty well", what do you mean? power dampening = = power control/scaling type thing?

Can you add some specifics? You might be on to some thing.

It works pretty well as in sounding just like the amp cranked up, but at much much lower levels. I didn't get to run it thru its paces today as much as I would have liked to. The wife was in "Spring Fix-up" mode and I was painting shutters in the sunshine. They look great by the way, so I can't fuss too much.
This mod is very easy. Two wires and a pot. The exact pot size isn't that important. I tried it with a 500k audio pot on my first successful try. I went to 1meg linear trying to adjust the sweet spot. Basically , lift R15 from its connection to the PI cathodes and solder one wire to it and the other wire to the cathodes. Those two wires connect to the wiper and either one of the outside lugs of the pot. The other lug is empty. If the action of the pot is backwards, move the outside wire to the opposite side lug. It acts very similarly to a master volume but sounds more full and compressed. Try it, you might like it.


LeeMo

Like this? Sounds too simple to not try it out.

Yep, that's it exactly.
Starving the PI. 1 meg might be too cold. On more extreme settings the distortion stars to sound ragged on lower guitar volume settings. It's not as noticeable whn the 'buckers are blairin'.

LeeMo

How was it with 500K then?? Better? Or are you still sampling this?

Actually, I've been playing with it this morning. I believe that the 1 meg was going the wrong direction. I put a 250k in and got a more useable swing. It's an audio taper so its more sensative at the upper end. The original posts on Hoffman's forum suggested a reverse audio 50 k. I don't have a RA. I measured the resistance on the 250k pot at the lowest useable (to my poor worn ears) level to be 100k, so the 50k wouldn't be too far off. The RA slope would smooth out the swing. I'll try to find one locally and pop it in this evening.

LeeMo

LeeMo - did you settle on a good value? I'd like to try this out.

I'm back to using a 47k linear pot. I haven't been afforded the time to 'speriment of late. There are two or three sweet spots that I need to measure. I'm thinkin' that a rotary switch with varying resistors and a jumper in the last position would be an easy mod.


LeeMo

Cool, keep us posted. I have lots of rotary switches!

coco,
I ran by the "shack" at the mall and picked up a two pole six position switch (275-1386) and an assortment of 1/2 watt carbon film resistors(271-306) 5% tolerence. A whopping $10.
Since I had good luck with the 47k pot I started from 56k and worked my wa thru to 0 ohm (straight wire). I used the following: 56k, 22k, 15k, 10k, 4.7k, and a piece of cutt-off wire from the end of a resistor.
I slipped the resistor wire thru the hole from the inside until the body almost touched the terminal. I soldered it and waited for it to cool before bending it straight up out of the way and trimming the excess. I worked my way around the switch soldering one at a time until I had all five resistors and the jumper done. Then I started just above the resistor bodies and bent the unsoldered end at a right angle so that it would contact the one to its left. I trimmed the tails off and then worked my way around the semi-circle soldering .
The two wires that I had run to interrupt R15 were then soldered to the common terminal on the switch and the top semi-circular buss, respectively.
Now I have six positions that range from stock to bedroom level. I'll give it a two thumbs way up. It works much more solidly than the pot.

LeeMo

LeeMo..How's this?

Perfect!


LeeMo

Hi!
Did you select these values based on some "sweet spots" on a pot or just random?
Stew

I played with the pot and then measured it several times. I would think that I was close but it would be different each time. I knew what it sounded like at 47k and I knew that I wanted zero , or straight wired. When I got the resistors from Radio Shack I looked to see what was close to 47k. The closest was 56 k. I took this and zero as my "brackets". That left four in between. I knew that since my cathode resistor was 820ohms I should at least double that to 1.64k to even hear a difference. That left seven resistors available in that pack between 56k and 820. The first two were 1k and 2.2k. I also pulled 100k to test. I made a hook-like cradle in the end of each wirewhich allowed me to lay each resistor so it would touch both wires and complete the circuit. I quickly ruled out 1k and 2.2 k. There wasn't enough difference between those and straight wire. That left 100k on the other end. It was too much for my tastes. So, that's how I came to use those values. I tried each one and the progression was such from one to the next that I didn't feel the need to split hairs.
One could use a separate switch and another bank of resistors on the other half of the rotary and either series or parallel them to obtain other values but I felt that would be a waste of time since most of these values don't get used either.
Feel free to try alternates. You might find a sweet spot that I stumbled past. There was very little science in my choices.

LeeMo

this sounds like an idea worth trying out. my radio shack wall mount attenuator sucks tone at the most extreme settings, so i'm open to other cheap fixes, so i don't bug my wife and/or neighbors too much with my playing.

Haven't seen this thread before. This looks very doable. I'd like to try. I don't have the V6, do you think it would work on the sIII.
The thread died, so Coco, did you ever try this?
Leemo, what were your final observations?
liquidsuspension,
Thanks for dragging the thread out.
Later, Jac

I havent tried it but it should perform the same in the sIII as the v6.

My Radio Shack attenuator is the auto-transformer style [not the L-Pad]and it is decent. liquid - which model did you use? There is a thread here with the good models to use.

I have the radio shack attenuator , I just think this is already in the amp, easy to use and no extra box . Once she's up and running, Easy to try.

i forget the actual model #, but its the 50w x 2 stereo model. i have it wired to run 16 ohm. it sounds decent up until the last 2 clicks, and then it strangles it.