Home » Audio » Thermionic Emissions » Retubing the Cayin
Retubing the Cayin [message #9619] Thu, 06 April 2006 13:43 Go to next message
colinhester is currently offline  colinhester
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Well, after swapping out the stock Chinese EL34s for the Svetlana Wing-Cs (thanks to BOI) I got the bug to put new tubes in the amp's front section and CDP. The amp is getting Mazda chrome plates (platinum grade) in the 12AX7 and 12AU7 sockets. The ShengYa CDP is getting a NOS Ediswan CV2492/6922. I don't know if the new tubes will "tickle my balls," as one reviewer recently told me about his mods, but there's always hope......Colin

Re: What did the Wings do for your Gonads? nt [message #9624 is a reply to message #9619] Fri, 07 April 2006 15:54 Go to previous messageGo to next message
Bill Epstein is currently offline  Bill Epstein
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The 'nads are fine...... [message #9625 is a reply to message #9624] Sat, 08 April 2006 01:51 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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The new tubes seems to breaking in nicely. Let me get a few more hours on them, but, so far, a very involving, three dimensional sound........Colin

Re: What did the Wings do for your Gonads? nt [message #9626 is a reply to message #9624] Mon, 10 April 2006 21:26 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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The Svetlana Wing-Cs are breaking in nicely. Installed the Mazda chrome plates (12ax7) and the Ediswan 6922 today. Still waiting for a set of Mazda 12au7s. So far: my love life is much better; I think my hair is growing back; and the kids are doing better is school.

I really need others' opinions about what to do next; so, I feel a wrongsideofthetracks coming on shortly. Do you have a list of your reference music (CD) somewhere?.......Colin

Re: You're gonna hate me for this! [message #9627 is a reply to message #9626] Tue, 11 April 2006 03:42 Go to previous messageGo to next message
Bill Epstein is currently offline  Bill Epstein
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I'm wrapping up the listening to the KR Audio VA 340 amplfier and finally switched the 300BXLS tubes for the 842VHD.
Both types output 20 watts. But where the 300BXLS is a very good but more powerful 300B, the 842 is a brand new listening experience.
Forget about every other tube or designer: 45, 845, 811, Yamamoto, Brenneman, Welborne....
I'm listening to Eva Cassidy Songbird and Joni Mitchell's Hits over and over for the pure joy of it.
Got$6800 U.S.? You need one of these!

842VHD [message #9628 is a reply to message #9627] Tue, 11 April 2006 04:04 Go to previous messageGo to next message
Damir is currently offline  Damir
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Interesting tube - although not cheap, quick calculation showed that with resonable OP (300B-like), 450V/100mA/-95V and Ra=4k, we can expect about 17W of SE power in a new designed (DIY) amp...twice as "normal" 300B.

Update/correction (specs) [message #9629 is a reply to message #9628] Tue, 11 April 2006 06:45 Go to previous messageGo to next message
Damir is currently offline  Damir
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On the second look, the specs on the link you provided doesn`t seem quite right - in OP 450V/-95V/100mA we`d have rp=700 Ohms, µ=4,8 and S=4,8 mA/V (?!). Barkhausen said rp=µ/S, and I found another (probably right) specs on "kraudio.cz" site:

Ua=450V, Ia=100mA, Ugk=-94V, µ=3,7, S=5,7mA/V

From that, rp = µ / S = 3,7 / 5,7 ~ 650 Ohms

Than we can use the primary load Ra=(Ugk*µ/Ia) - rp = (94*3,7/0,1)-650 = 2828 Ohms, we`d use the "standard" 3k primary.
Voltage "swing" on the anode load is:

Ua = Ugk*µ / (1+rp/Ra) = 94*3,7/(1+650/3000) = 285,9 Vp = 202 Vrms

And max. power in class A1 is Pa=Ua^2/Ra = 202^2/3000 = 13,6W.
If we assume 10% losses, then we can expect about 12W of power, still respectable, but not 17W
Verification - tube is "biased" with 100mA, it means AC 100mAp, or 100/1,4142 = 70,7mArms max. And it "allows" Pa=Ia^2*Ra=0,07^2*3000 = 15W of AC anode power, but limited voltage "swing" gave us "just" the 13,6W anode, or ~12W output power.


Re: You're gonna hate me for this! [message #9630 is a reply to message #9627] Tue, 11 April 2006 09:37 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Just think what it would sound like if you wern't using a second rate CD player

Re: You're gonna hate me for this! [message #9631 is a reply to message #9627] Tue, 11 April 2006 12:56 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Sounds like a beaut!

How 'bout bringing it to GPAF?


Re: Yeah, Barkhausen was a hell of a player, wasn't he? [message #9632 is a reply to message #9629] Tue, 11 April 2006 17:14 Go to previous messageGo to previous message
Bill Epstein is currently offline  Bill Epstein
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Saw him beat the Heat once, single-handed.
I'll take your word for the math. Feels like the amp is about 40% more powerful than the "normal" Audio Note 300B.

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