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Vintage threads from the first ten years

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previous: Two Tone Those 2 caps donĀ“t make no differe... -- 3/20/2004 9:26 PM View Thread

Re: Why does my RI Orange sound better than my vintage one?

3/21/2004 4:40 PM
Re: Why does my RI Orange sound better than my vintage one?
Both amps have SED EL-34's in them, both running at about 65% max plate dissipation. The plate voltage is a tad higher in the 70's head (by about 12V), so the specs aren't exactly the same. But they're running as proportional as I could get them.  
Yeah, the 70's head had the PI with the 390K plate resistor. Which I was surprised of because I thought that was just a post '74 thing. The schematics dated '72 that i've seen have a different PI. I guess they used that for a year or 2, and went back to the one with the 390K. I've tried both in my 90's head and I liked the 390K one a bit better. It was more fuzzy, and a bit less dymanic, but seemed to have more punch and a tighter sound.  
At any rate, do you think that head may need a recap?  
It had been sitting a while before it came to me. I wasn't really getting any hum. But for the first hour or so, if I REALLY cranked it, you could hear the voltage swing dropping. It would take a second to catch up. That went away just from rocking it at high volumes for about an hour and it's been flawless ever since. My meter isn't strong enough to measure the big electrolytics to see how far they've drifted. But the amp is either a '70 or a '71 and every component in it is original. In cluding the filter caps.  
I'd hate to track down the 100mfd 500V cans, and fork over another $50-60 and do all that work, and still have it sound not up to par.  

Two Tone I would by all means change ALL cap... -- 3/21/2004 6:27 PM