| Cool, I'll let you know how mine turns out [message #9551 is a reply to message #9550] |
Tue, 14 February 2006 07:56   |
Old Brown Eyes
Messages: 25
Registered: May 2009
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My setup is simpler. A 6sn7 split load inverter (direct coupled to 6sn7 voltage amp) with 22K load(s). Grid is around 100vdc with 300vdc B+ and 0.47uF coupling caps. I don't need to swing much for triode strapped 6V6 tubes. My chokes are 1,000 henry, M6, with a DCR just under 4K. I used them on the grid of the voltage first but have decided the 6V6's are the correct place to use them (but I liked the sound enough to buy another pair and thought I had some bass boost:). I am waiting on the other pair to arrive. Did you measure the "Cw" or was it provided to you?
Russ
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| Re: Cool, I'll let you know how mine turns out [message #9552 is a reply to message #9551] |
Tue, 14 February 2006 12:08 |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Cw - well, no - unfortunately, for now I don`t have almost anything of measuring equipments. Without scope you are blind :-).
I mean, ears are not enough - in the last few days I changed so many things and went through many cascode versions...everything is so similar sounding and interactive... 
And clever ideas on paper mostly aren`t "good enough" in practice.6SN7 concertina - I tried it with 27+27k, first stage 56k/620 Ohms. 5687/E182CC concertina - 10+10k, first stage 27k/330 Ohms. I have a plan to change this 27k to CCS in my DIY monoblocs...5687 is a good sounding in many circuits, but I`m little dissapointed with it in the cascode driver...50Vrms out isn`t a joke, though.
If you have a scope and sig. generator - look for the sharp peak around 10Hz - enlarging of coupling caps would probably result in little lower peak, in magnitude and frequency. Keep us posted.
Did you see this - seems interesting PC measurements system?!
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| Cascode....hmmmm...have you considered/tried [message #9553 is a reply to message #9552] |
Wed, 15 February 2006 08:28 |
Old Brown Eyes
Messages: 25
Registered: May 2009
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Chancellor |
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6H30 (or 6N6)? Might mate well with the slightly romantic sound of a 300B. Something like 12-13ma, bias the lower tube around 4 volts, shoot for low 200's on the top tube's plate...I forget your B+ but maybe around 14K-12K load resistor? Also consider ditching the resistor between the two tubes and biasing the top tube's grid from a voltage divider (Allen always hated me showing self biased cascodes). Don't forget grid stoppers and do float the upper tubes heater with B+ voltage divider:) Might be better as a direct coupled cascade with a 1:1.25 IT to the 300B but now we have a different amp (and no place for your grid chokes). Totally agree that ears alone are not enough and also think in this day and age a computer based testing system makes sense. But you still need a rather good sound card and I'd say at least 16 bit resolution (on the PC scope part)....so it still isn't cheap by any means. Besides we would drive ourselves crazy with FFT plots and THD values...LOL! Russ
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| Re: Cascode....hmmmm...have you considered/tried [message #9554 is a reply to message #9553] |
Wed, 15 February 2006 14:27 |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Unfortunately, I don`t have any 6H30Pi, ECC99 and similar "candidates".
I tried BP Raytheon 5687WA and E182CC (Philips and Amperex) I have.
Just looking in a few sheets of papers, full of measured numbers. I tried three cascode variations, with many little tweaks. Full "report" soon.
"Slightly romantic" SE 300B sound can be ("wickedly") described also as warm/distorted, limited on both frequencies extremes, slow, soft, compressed...
Every change is "interactive", and IME - it isn`t easy to find the "right" sounding driver circuit.
And without FFT/THD and frequency plots I can only suspect that "strident" E182CC sound have something to do with odd upper harmonics, or "warm", "dark" and "mushy" 5687 sound with some other (lower) harmonics/IMD... And yes, good soundcard is expensive. Expecting some NOS sockets, and more E182CC, 5687 and 6C45Pi tubes these days.
And yes, CCS can sound a little "dry"... this afternoon I tried CCS loaded 6J5GT driver, sound not bad, but (of course), A only 21.
P.S. I used AZ50 rectifier tube, my choice between all 5R4GYB, 5V4G/GZ32 and GZ34 tubes I tried... "Besides, we WOULD drive ourselves crazy with FFT plots and THD values...LOL!"
Don`t tell anybody, but I don`t need that papers with numbers...nor I used schematics...it`s everything in my head...and not much of anything else...
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| 0,47µ/4µ7 [message #9555 is a reply to message #9554] |
Thu, 16 February 2006 06:43 |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Today I tried A/B test with 4,7µ Mundorf Supreme coupling cap and 0,47µ Auricap "in front of" the grid choke. Larger cap (Mundorf) has "silky" highs, and somewhat "soft" sound, but detailed. 0,47µ Auricap has more "punch" and "harder", more "dominating", but little "rougher" sound.
With little help of test CD I measured bass response of both combinations (anode out of CCS-ed 6J5GT), and 0,47µ / grid choke combination has little bass boost on 20Hz, about 0,84 dB. This resonance started at about 160Hz, and has it`s peak probably somewhere around 4-5Hz, but I don`t have
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