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PostPosted: Sat Oct 20, 2018 3:52 pm 
Mark II
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Joined: Tue Feb 26, 2008 2:23 am
Posts: 79
Location: West Chester, PA
afu wrote:
dtrax wrote:
afu wrote:
I updated the page regarding the voicing circuit, gain, and load resistor.

Thanks for sharing. Your site is one of the inspirations for me learning about tube amps. :mrgreen:

Thanks, I appreciate that.

FYI, I found that I made a couple of mistakes with the math for the "Design Concepts' articles. There were a couple of really misguided articles I deleted. I hadn't thought everything through as well as I could have, but I've fixed most of it. I'm just really ill all of the time, so my blog has not even taken a backseat, because it's in the trunk.

Jumpering the cap on the Output pot, in practice, restores some of the low end lost when using Loop Active. IOW, it sounds a bit fuller (e.g., less tone suck). In theory I'm unsure why this is TBH. That pot has a 330K resistor in parallel tying the input to the wiper, with said cap in series. In my limited knowledge, I assumed this was a bright cap, but the opposite effect occurred when I jumpered it. It wasn't a night and day difference, but as with most things, small increments here and there contribute to the bigger picture. The brightness/fizziness is still present, but that can be dialed back with the treble/presence pots to some degree. For example, I keep the Treble at 2:00 with Loop Bypassed, but dial it back to 1:00 with Loop Active.

It's a treble bleed. I've done a similar thing on the pot to one of my guitars. You don't have to jumper it. Having both components removed is the best thing for a mod. A jumper will allow a bypass path for a signal.

You're right. And I misspoke (typed?) about jumpering it - I did simply lift it off the pcb.

It's worth the effort for lower volume playing (a bit fuller). For gig volumes I didn't notice much difference. I've always kept the channel master for modern mode somewhere in the 10-11 oclock area. Seems to sound the best and balance well enough with CH1 to get a reasonably clean tone if needed.

One mod I'd like to do is disable NFB for CH1. That would eliminate all volume balancing issues. Plus I vastly prefer no NFB as a whole, for dirty and clean sounds. But I'm not savvy enough to be messing with relays and such. One day... :mrgreen:

Ibanez '98 RG7620 (EMG 81-7H, 60-7H)
Triple Recto 3CH (modded), Studio Preamp (MK2C+ mods), 2x12 Recto Vertical cab
Mark V head, Rectoverb series 2 combo, F-30 combo, V-Twin rack pre

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