Stock 68 spec W/2"OT and such...

[Strat78]

Wow, that little quote from Ben really brought tears to my eyes, I don't understand why he is not hear with us and I never will. Anyway, I did use the variac to bring the voltage down from the wall to 110v. It seems like the 2" in my other 68 is pretty aggressive but I really need to make a clip first to see how this new amp with the 1.5" 2.2k OT gets interpreted in a recording. The good news is, my wire dress seems to have been a success as far as eliminating unwanted nois. No need to braid the secondaries from the OT!

I still have my original Metro 68 and 69 kits, but I have not fired them up in over a year. They are totally sick just the way they are, those were some great times here at Metro. Ultimately I want to have three different amp stations set up with everything needed for that particular rig. The two metro's will be a slave setup, my 50w and one of my 68 homebuilds will be a daisy chain set up and then there will be this latest amp with only the head and cab with an echoplex. The next build will have a jose master After that, I have one chassis left! Itching to do a JTM 45/100 if I can only find someone who makes the chassis with the end blocks.

[vanhalen5150]

Yeah, Ben was pretty cool in that respect. I always got the feeling he would go out of his way for anybody. And that he did.

I have 2 12000 chassis left. That will total 4 12000's when I'm done. I'm the Agustus Gloop of Metroamp. Still working on a 2204 as well. Id really like to try some of the mods I've recently got in one. Maybe a correct Jose master would be ideal. Maybe even a switchable gain stage for that extra tube socket. It's hard to beat the straight up none mv though.

Also thinking of a variplex design. Just not enough hours in the day.

[vanhalen5150]

Oh yeah, also waiting on some resistors for a ****** mod on the Sovtek.

[Strat78]

Some rare 470k iskras on eBay right now, get them while you can!

[vanhalen5150]

Some rare 470k iskras on eBay right now, get them while you can!

I'm ahead of you. I unleashed the fury this morning.

[Strat78]

So here is a short clip. The tone in the room was horrid and the feedback was beyond control, I seriously wanted to hang it up today. However, somehow something better came through on the recording, it's not great, but the gain and hair is sort of nice. I'm going to switch the tap over to 16ohm and look into waxing this old Mighty Mite #1300. Still frustrated though, kind of just spinning my wheels here.
http://soundclick.com/share.cfm?id=11683786" onclick="window.open(this.href);return false;

[vh junkie]

Yeah, there's a lot of good things going on there! Great to see your getting back in to the swing of things! SO, this is the new amp w/ the MM trannies? What does the PT come out to at wall voltage? Variacing a bit? Your tone is really singing, especially on the single notes/bends!

[Tone Slinger]

Fuckin Awesome there Strat78 ! That is pretty much all there is too it right there('realistic' vh1 tone). Hair splittin is all thats left over the minor details. Loved the playing too

[emmjaydubya]

Wow! So your power tranny is putting out around 400 volts and you drop wall voltage to 110? What's your B+ right about now? EH 6CA7s again I assume? You always seem to get way closer than anyone else, that thing is screaming right out of the box!!

[Strat78]

I have to agree, the tone is pretty wild for an amp right off the bench, with no boosts, perhaps the combo of pihers and iskras worked some magic, still it was frustrating trying to keep the amp and cab from flying away at the edges. The tubes are NOS GE 6ca7's and the cab has 70's black backs.

I had the variac down to 110 where the plates were 411 and after biasing , the plates were down to 395. I forgot that I wanted to run this tranny closer to 120, so I'll try that tomorrow. Yes, these are the new MM tranny's the VZS OT and the 100-400 PT, this just might be a good combo.



Robert, when calculating the bias without the 1ohm resister, do I use the 17.5 el34 standard rating for the formula:

17.5/395 *2 *18R(resistance between tap and V5 pin3 amp off) = 1.50 target.

Or:

.706(voltage between tap and V5 pin3 with amp fully on)/18R *395v = 15.4

Do I plug 15.4 into the first formula or the 17.5 or is 15.4 simply the voltage output at idle?



I'll try a stiffer bias tap tomorrow but I hate to cheat rather than just work on controlling the amp in other ways. I spent some time trying different bright caps from 1000pf to 5000pf, and to my surprise I found that they really stifled the character of the amp, so I left it out.

[vh junkie]

when calculating the bias without the 1ohm resister, do I use the 17.5 el34 standard rating for the formula:

17.5/395 *2 *18R(resistance between tap and V5 pin3 amp off) = 1.50 target.

Or:

.706(voltage between tap and V5 pin3 with amp fully on)/18R *395v = 15.4

Do I plug 15.4 into the first formula or the 17.5 or is 15.4 simply the voltage output at idle?

The first formula is correct
17.5/395 *2 *18R(resistance between tap and V5 pin3 amp off) = 1.50 target.
But, I get 1.59v target.

[vanhalen5150]

That sounds great already.

Where did you get the 8.2K and 10k 2 watters? I can't find any.

[rgorke]

Some rare 470k iskras on eBay right now, get them while you can!

I'm ahead of you. I unleashed the fury this morning.

Is it the auction with 10 of them?

[vanhalen5150]

Yeah, pricey eh?

Also these:
http://www.ebay.ca/itm/380443309413?ssP ... 1439.l2649" onclick="window.open(this.href);return false;

[Strat78]

10k 1w and 2w seem to be plentiful but I have never seen 8,2k 1w and 2w Iskras. I got a couple of 8,2k Pihers last year, but looking now, I guess I got kind of lucky. Try carbon comps in these positions, they sound pretty good! I've been going through the Amp Archives site checking out all the original 68 100w amps. Most are exclusively Iskra's.