Metropoulos Forum

kewl! Thanks for all your help guys

If you still have the 100k hooked up, could you take a better picture showing where the alligator go for other builders, my pic did not quite show it well enough. Don't take the Iskras out yet until you fire it up again and see if it sounds better. I hate to see CC's pushing Iskras out of the old neighborhood.

was thinking the same thing - taking this section of my build thread and making a forming cap thread with pics for future use.

not to worry, iskras will get their fair shake. how unpatriotic is it to work on President's Day...

amp's back on line and the initial feedback is very good. I think the best way to summarize the recent changes is in the bass pot. the lower preamp filter and the higher PI filter seemed to work very well together, allowing the bass to be turned up and make the sound bigger, fatter, not flubby. before anything over 2 just didnt sound right. now i have it on 10 and its huge. you can pound on the low E (D) on Unchained and it chugs as it should. Very nice. I'll keep it this way for a while and get some clips out. Eric, Mike and I are set to do another summit this Saturday.

update
spent the weekend forming caps (bumped PI to 100 and dropped preamp to dual 16), replacing cement resistors with Iskras and a couple other mods. It was apparent from the start that something went the wrong way so I put the dual 32 preamp Erie back on and did some research on excessive metallic distortion and decided to bump the 820s on v1 up to 1.1k ccs to account for the drift supposedly measured on "the plexi". the result is here:

http://www.soundclick.com/player/single ... 59944&q=hi" onclick="window.open(this.href);return false;

i spent less than a minute dialing in the chamber reverb but it gets the point across.

most of the clip the volume's on 8, guitar pot varies and resonance mod is about halfway (on an audio taper pot...).

Mic is dead center about a cm from the prerola dust cap. any further and the results were muddy and this gave the best woody type tone for JC.

Where to go next?

Hmm..I think your tone was better than this on your previous clips...

at this point there's just as much struggle to get the right sound into the mic as there is tuning the amp. that phone clip does sound "better" than that mic'd clip from last night. its more airy, not as stuffy. remember my cabinet is split with V30s and i know people dont like them but the combination sounds great in the room and I'm having a hell of a time getting a recording, at least with one mic, that puts a real smile on my face like it does live. I think the experience speaks to how much effort went into micing the first record. A second mic out in front of the cabinet would be helpful. Although Ralle and Strat get good results so I'll keep digging...

actually after listening to the JC iso clip its not too far off. the album is not truly dry on the left side and that lends some air to the signal. my notes tell me that when i removed the 500pf silver mica bright channel mixer and 47pf PI cap for vintage dogbones the tone became a bit less crisp. I think I'll go back and see how that sounds. If i can get more clarity I think I'd be pretty happy. The rest could be recording mojo.

Where you guys getting your Iskra's from?

Flea bay. Some guy in Italy I think. Good seller w good communication.

YMI5150? wrote:Flea bay. Some guy in Italy I think. Good seller w good communication.

Ok, that's they guy I've been looking at. What values are you using? All preamp and the 10K's?

ISKRA'S
Some of what we want is up right now. The NOS accurate 1/2watt ones measure d=4.3mm, L= 11mm and the larger 1 and 2watt 10k's are available too. I see the correct 1/2w 68k's, 820ohm, 470ohm, 1meg, and again the 1 and 2watt 10k's. It's very difficult to find correct 1/2watt 470k, 220k, 82k and the impossible to find 1/2 watt 100k (I would gladly pay allot if anybody has them)! There are some 1.5k 1watt's there too for your grid stoppers.

I may unlease some ebay fury later today on those.

BTW...ISKRA is Russian for "spark". So if you ever get a dog, call them "ISKRAY"

good trivia!

I'm losing my marbles with all this stuff, particularly when trying to get things recorded. the room sounds amazing, especially when i run both cabinets and the right side with lexicon verb.

i want to try and focus the gain a bit, will put the Isra 820s back on v1 and see how that does over the 1.1 CCs.

I pulled the .68 mustard off v2 last night and tried a 33uf electrolytic after rethinking the whole fat cap thing. not sure what I'll put on there for tomorrow's summit. it still works but I have to rely on my resonance mod for both caps so we'll see how that flushes out.

i am also thinking of trying a higher NFB circuit to help tighten things up too. just a few things to evaluate after work before tomorrow...

Think I'll name my next kid "Iskra".
I sent one of the 790's Pihers that was in Ben's amp, try that in v1b or v2a instead of the 820. That will give you a little more radical demonstration of the gain change and focus. I only see the fat cap working if we are taming the low E string flub with a mxr 6 band.