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

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Strat78
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Re: Stock 68 spec W/2"OT and such...

Post by Strat78 » Tue Mar 05, 2013 7:30 am

I had to use a 5.6k bias resistor to make that 27k slider work. Oh, and that loose wire, I was just in the process of alligator clipping in different value caps for the bass pot, it's fixed now.

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

Post by Strat78 » Fri Apr 19, 2013 4:38 pm

Put in the Marstran tranny's and noticed right away how much woodier they sound. The sag was not as crazy as I had hoped but I need to work with it some more. I think the 33k nfb with the 16ohm tap sounded best but I was lured by the added gain that a 8ohm tap and a 82k nfb produced. But, I don't think that gain is right at all and the amp starts to get this arrrrrggggg tone that bugs me, so back to the 33/16. I'm getting really obsessed with getting a nice fluidity to the wire dress, Here are the two latest builds with mostly NOS goodies.
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Re: Stock 68 spec W/2"OT and such...

Post by JimiJames » Fri Apr 19, 2013 11:53 pm

man the GE fatso's are fricken killer ! I know I said it before, but man, that RS slider is just balls out man!
So woodier is goodier & 33/16 sounded better and feels betterer. Is there a difference in plate voltage between the 2?
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Re: Stock 68 spec W/2"OT and such...

Post by Tone Slinger » Sat Apr 20, 2013 9:39 am

Thats a .022 instead of a .0022 huh ?
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Re: Stock 68 spec W/2"OT and such...

Post by Strat78 » Sat Apr 20, 2013 12:11 pm

I keep the plates around 377v on both. The woodiness of the Marstran's is good and less modern sounding than Chris's PT with the MM 2.2 OT. The 33k nfb and the 16 ohm tap has everything, the drumminess the gain and sparkle and seems to bring out the color of the tranny's much better. Those are .0022's but they look like the same size as the 022. Note the cool 1957 ceramic 9 pin sockets! 8)

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

Post by rgorke » Sat Apr 20, 2013 1:23 pm

Are you liking the chicklet .68s better than mustards? And why? {Edit: I have had a chicklet over V1 and a mustard over V2A I switched the mustard for the chicklet and what I heard was a much brighter, biting, cutting tone. The mustard seemed to take the sharp point off the tone. Granted, I am attenuating and at low attenuation levels, the chicklet sounded really good, but when I turn the attenuator volume up, it seemed to get overly bright. Again, this is MY amp and YMMV.}

Weren't you down to 27k on the NFB at one point?

Those are EH 6CA7s, right?
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Re: Stock 68 spec W/2"OT and such...

Post by Strat78 » Mon Apr 22, 2013 7:52 am

Those are GE's from tube tramp. :D I like the way George's 12382 sounds and it has some sort of chicklet stock in those positions. I believe the 12301 pre board at least looked exactly like the 12382 before any stupid "mods" were inflicted (the big round ceramic grid resistors are odd in the 12382, but George said they can be seen in Marshall Majors as well, so again they can be considered oddball stock). The amp with chris's PT sounded best with a chicklet and a mustard and totally hit a new high with Ralle's latest discoveries, in fact it was a much sweeter tone than the 12301 and left me scratching my head as to why I continue to pursue that amp. :mrgreen: At first I thought the 5600pf was too high for the vol pot but now I think it is the only way to go, because you don't have to back to far out of the warm gain realm before you start hearing the effects of that cap, vs. with a 4700pf things just get a little cold by the time you start getting the right bite. Still, every amp is different.

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

Post by Strat78 » Fri Apr 26, 2013 7:49 am

I really like the old RS sliders for the bias but it is hard to get the ones that are in a practical range. Like for the 25k slider on the amp pictured above, I had to use a 5,6k bias resistor to get it in range. I have a 5k and several 2,2meg sliders that I want to use, is there a formula I can use to figure out what bias resistor will get me in range? I usually just start by blindly trying resistors but I don't want to tear into a new amp just to find out that these particular sliders won't work.

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

Post by Tone Slinger » Sat Apr 27, 2013 5:20 am

Lets hear it :drool:
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Re: Stock 68 spec W/2"OT and such...

Post by Tone Slinger » Tue Apr 30, 2013 6:32 am

I just discovered that the little Panasonic .68uf caps that ValveStorm is selling really give you that sizzle on v1b. They are polypropelyne. Very noticable guy's. Mucho clarity. Give one a try.
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Re: Stock 68 spec W/2"OT and such...

Post by vh junkie » Tue Apr 30, 2013 3:12 pm

Yep! I have pulled the chicklets outta mine for those as well... might be what Suhr is using as well?
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Re: Stock 68 spec W/2"OT and such...

Post by Strat78 » Tue Apr 30, 2013 6:14 pm

Worked with the polypro's way back around page 17. Ben never liked them, I liked one in v1B or the PI couplings, but we found mustards sounded best in those spots. With the polypro's the sizzle was great but a little sterile. The chicklets are metalized polycarbonate film, which has it's own sound, good and bad, but I like the openness.

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

Post by harddriver » Tue Apr 30, 2013 8:55 pm

Strat78 wrote:Worked with the polypro's way back around page 17. Ben never liked them, I liked one in v1B or the PI couplings, but we found mustards sounded best in those spots. With the polypro's the sizzle was great but a little sterile. The chicklets are metalized polycarbonate film, which has it's own sound, good and bad, but I like the openness.
Great looking builds there Phil! Metalized Polycarbonate film huh! I''ve read that the manufacture of Polycarbonate capacitors was very expensive versus metalized Polyester/Polypropylene hence you don't see many around now. Supposedly these are revered in the HIFI world.

I like the little SSSSSSSSS curve to your V1a plate resistor! :rock:

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

Post by Strat78 » Wed May 01, 2013 5:36 pm

harddriver wrote:
Strat78 wrote: I like the little SSSSSSSSS curve to your V1a plate resistor! :rock:
Ha ha, that's my little Iskra guardian serpent, put there to repel any "moders" who try installing a MV, cascade or ppimv. :twisted:

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

Post by stef » Wed May 01, 2013 6:12 pm

:whistle:
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