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theraygun
04-13-2010, 01:27 PM
I've got a Traynor YGM-3 that was modded with a master volume. The amp is a but too loud and I was wondering if putting a different value pot in would significantly alter the taper of the MV. Right now it's pretty freaking loud on 1 with the normal volume on 3.

tlpruitt
04-13-2010, 01:36 PM
Could be a linear taper pot. If it is you might try an audio taper.

More info on the pot value and its location in the circuit would be helpful.

Blue Strat
04-13-2010, 01:40 PM
I don't think a different value will help with the response of the pot and 1 Meg is the optimal value for least tone suckage.

Find out if the pot has an audio taper or not. If not, switching to an audio taper should help.

phsyconoodler
04-13-2010, 01:59 PM
It also depends on what TYPE o master volume was installed in it.
A PPIMV is more gradual and the crossline is not.

donnyjaguar
04-13-2010, 02:14 PM
Could be a linear taper pot. If it is you might try an audio taper.

More info on the pot value and its location in the circuit would be helpful.

Yeah, and there could be other modifications in the rig too.

theraygun
04-15-2010, 09:00 AM
Thanks for the tips. I'm just going to put in an audio pot as the current one has no markings. Below is a gut shot, the master is on the bottom far right with a cut control next to it on the left.

theraygun
04-15-2010, 09:06 AM
http://i99.photobucket.com/albums/l282/jonrayer/IMG_0705.jpg

theraygun
04-20-2010, 07:23 AM
Well, I switched out the pot and it was a 250k audio. I replaced with a 1M audio, but still not much sweep. Is the location of the MV the problem? Any takers?

Blue Strat
04-20-2010, 08:09 AM
Well, I switched out the pot and it was a 250k audio. I replaced with a 1M audio, but still not much sweep. Is the location of the MV the problem? Any takers?


We'd have to see a schematic to tell you that.

If you don't mind losing the capability to dime the amp, you can hook a 1M or higher fixed resistor in series with the pot on the "feed" (as opposed to the ground) leg. That would give you more range on the pot.

hasserl
04-20-2010, 09:55 AM
In general, the smaller the pot value, the more the effective range if spread out over the sweep of the pot, but also the more the preceding stage is loaded down, resulting in some loss of the signal strength; the larger the pot the more the effective range gets concentrated to the low end of the pot causing it to react more like a switch, it tends to be all On or all Off, small adjustments of the pot result in large changes in volume, but it also loads down the preceding stages less, maintaining the strength of the signal level.

tlpruitt
04-20-2010, 04:57 PM
From the picture it looks like the master you have is the post PI "phase cancelling" type of master volume like Matchless amps use. I believe Matchless used a 1M audio pot in their master volume.

There are other post PI master volumes that use a stacked type pot and are popular. Somewhere on the web are the Ken Fischer Trainwreck pages that describe how to do the other post PI master volume controls.

theraygun
04-24-2010, 07:13 AM
Thanks for the tips. The cut control and master volume are wired between C14 & C15. The wires are to the center and right lug of the pot. Here's a schematic. Any pointers on a different way to wire this up?

http://i99.photobucket.com/albums/l282/jonrayer/730911_YGM3_4.gif

A high resolution copy can be found at http://www.lynx.net/~jc/730911_YGM3_4.gif

tlpruitt
04-24-2010, 08:30 AM
Go to the link below and scroll down to page 41 :
http://angela.com/thetrainwreckpages.aspx

I believe you currently have the type 3 master volume shown on page 43. The type 1 and type 2 master volumes are both popular. Both require a "stacked" pot.

theraygun
04-26-2010, 11:12 AM
Thanks for the link! Looking at type 1 & 2, how do I figure out the cap and resistor values in the middle?

tlpruitt
04-26-2010, 11:35 AM
Those caps correspond with C14 and C15 in the YGM schematic you posted. You can leave them as .1uf value caps.

hasserl
04-26-2010, 12:43 PM
Note that on the type 1 MV the caps are effectively in Series. Capacitance value of caps in series equals C1*C2/C1+C2. The total value will be less than the value of the smallest cap. You can't get to .1uf final capacitance by using the stock .1uf caps and adding another cap in series with it, it will always be smaller. However, you could get real close. If you used a 10uf cap in series with the stock .1uf cap the result would be .099uf, which is close enough for rock & roll (not to mention there is some kind of tolerance in all caps anyway, so nothing is perfect). The 10uf cap, if used on the downside of the pot would not have to be high voltage, you could use a low voltage cap there that will only see the voltage of the AC signal and the DC bias voltage. So a standard 120v 10uf film cap would work fine. Personally, I like some reduction in capacitance at that stage (helps to control blocking distortion), as .1uf tends to be too large IMO, so I would use four .1uf caps, which would reduce the total capacitance to .05uf.

theraygun
04-27-2010, 05:38 AM
So, by using 4 caps, do you mean to replace the two on the board and then use the other two on the pots?

Roe
04-27-2010, 06:29 AM
I recommend a larmar with a dual 100k pot http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV

hasserl
04-27-2010, 10:06 AM
So, by using 4 caps, do you mean to replace the two on the board and then use the other two on the pots?

I don't know your specific case, but theoretically you could replace all 4, or you could use the 2 that are already in the amp and simply add 2 more. What works best for you is kind of up to you.

The 4 caps isolate the pot from all DC. I've installed many of these types of MV's in amps, they work very well, very transparent; but most of my installations have been on pcb amps, so I typically pull the stock caps and use all new caps when I install the MV.