|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
97.105.99.138
In Reply to: RE: Opinions on 6P3S for Hi-Fi ? posted by awesterner on May 07, 2017 at 23:01:07
That's very interesting, for several reasons. I've come to believe over the last few years that the larger 6P3S-E needs more than +400V to sound right. Most of the amps I'm rebuilding are right around that voltage, and that's one of the reasons I asked about the smaller 6P3S. I did try the 6P3S in a +400V amplifier several years ago, and I saw the red plating that Steve O mentions below. That particular amplifier was originally equipped with US 6L6GCs, but it ran them at +400V, well under their spec. That's the reason I thought the 6P3S might be OK. I don't remember the anode current now, but even at 35mA each, they'd be operating at much less than the common online spec of 20W dissipation.
Maybe the 6P3S needs to be limited to dissipation below 15W or so in order to keep the plates from showing color. If that's correct, it might be a better candidate for amplifiers using +350V or less. In fact, I've wondered if it would be useful as a high quality 6V6 substitute, and it's interesting to hear that you've tried that with good results. I do have several 6V6 amps to rebuild, and a larger filament transformer would be an easy addition. That type of modification is certainly less expensive than buying quads of NOS or upper-end 6V6 reissues.
--------------------------
Buy Chinese. Bury freedom.
Follow Ups:
An often-overlooked solution is to go with 12V6 instead of 6V6. I build from scratch, my own designs, and I use 12 volt heater circuits because it is easy to rectify and filter and, after the circuit is loaded down, it comes right in at 12 VDC or maybe a fraction of a volt over every time. This does help reduce hum.
NOS 12V6 is every bit as good as NOS 6V6 but WITHOUT the hefty price tag. you can still get NOS 12V6 all day long. The Conn Organ ones are usually black plates. They are simply rebranded tubes. So, you have options.When I stated "as I recall, i used 35 ma per tube," that was the last amp I built using them, and I did use a higher B+ than I would have liked. I think that is why I ran them at 35 ma. I THINK on lower voltage B+ I used quiescent current in the low 40s. It's been quite some time, so details are a little fuzzy in my mind. I haven't played with them much in the last 3 years or so.
I have branched off into screen drive with sweep tubes, and that is more forgiving of high B+.
Edits: 05/08/17
Yes, I'm a big fan of 12V equivalent tubes. The thing is, NOS sleeves or matching quads (same date codes) of 12V6s are becoming difficult to find. I have a decent stash, but I'm still thinking about building all my new designs with a 6V/12V switch for the outputs. There's probably no point in substituting the 6P3S into any of these amplifiers.
--------------------------
Buy Chinese. Bury freedom.
http://vacuumtubes.net/
worth browsing through.
That's Jim Cross in Orlando, FL. He screwed me on a large purchase of defective 7-pin 1625 sockets some time back. He offered to make good on a few, then stopped communicating. Cost me almost $100, and it was nearly a total loss.
--------------------------
Buy Chinese. Bury freedom.
ewwww. Sorry. I was led to believe this outfit was thee major supplier for smaller vendors. Guess I better break out the tube tester. I got a batch of the 12-volt 9-pin version of 6SN7 from him, 12FQ7.
I was quite happy to see this post - I really like the 6P3S . A while ago I purchased 36 of them and proceeded to current match them on my modified ST-70 . I swopped the 5AR4 in the ST-70 for a Russian 5C4M - this reduced Anode voltage to about 415V . I then adjusted bias to minimum and set balance adj. to the center position . I then use the ST-70 as a tube tester to current match the tubes , and then sort them into matched or closely matched quads .The spread at 415V range ( within my 36 valves ) from 30 to 50 mA . One tube ran over 70 mA and two in the mid to high 50's . I gave the highest current quad to fellow South African valve aficionado , warning him that this was the hottest running quad and should be used at low anode voltages .
The hotter running remaining tubes ( 40-50 mA ) I run in Quad 2 monoblocks with the same 5C4M rectifier ( 5C3S also works ) , with bias resistors values increased from 180e to 250e ( 4x 1K 1 watt resistors in parallel ) .
The cooler running quads ( 30-40 mA ) I use in the Dynaco and bias to ~85% dissipation ( ~17W per tube ) using Rob Robinette's online bias calculator to find desirable bias setting .
Compared to a Quad of vintage CV1947's , and 3 sets of EL34's ( Mullard , JJ EL34L's and EH's ) they sound pretty good ; in the Quad 2's or ST-70 . I love 'em . :)
For the money , I reckon you can't go wrong .
" When in doubt, do the courageous thing. " - Jan Smuts
Edits: 05/25/17
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: