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In Reply to: RE: DC coupled 6av5/6L6 posted by hennfarm on May 21, 2016 at 12:49:45
JH,That 35 HY at 185 Ohms choke is just fine !!! After the rectifier, is it choke or cap input ??
LOL. That 185 Ohm choke is placed there by you so one fine day you can spend $20.00 and put in two Triad C-40Xs, with 30 and 50 uF after each, and thus YOU get to HEAR the difference. ( Or hear Hammond's newly-designed 159ZAs, only 6 Ohms at a slightly heavy 2.5 pounds ).
Mikey Samara recently ( this year ) had a GREAT listening ( and measuring ) experience, adding a 10 Ohm C-40X on his recent Mac 30 mod.
What do you think it will sound like, when you go from 185 Ohms of Series resistances to the finals, to only 20 Ohms of series DCR ?? Mikey went from 100 Ohms to 10 Ohms, .... and he was very impressed. Isn't that so, Mr. Samara ??
Its something one NEVER forgets.... after properly experienced !!! All audio chokes to the finals need to be 20 Ohms or less in DCR.
( Instead of ten Ohm Ls, I am " mulling " over having wound for me custom 4 Ohm Ls, maybe 300 mHY, under two pounds total weight, ( low in storage ) just to HEAR that. )
Layout - I'd a placed those two RCA input jacks within 2 inches ( or less ) of the grid of the driver tube, on TOP of the chassis. Might have spaced the Output transformers behind the Finals tubes, and mainly - away from the input tube....fields radiate 'ya know !!
Voltages - Did you get 150 to 195 VDC on the plate of the 6AV5, so its in its best sounding plate VDC operating range??
Howz it sounding to you on yer 4-Pi speakers, versus other DIY builds you have done??
Very LIVELY, at even low listening levels ?? Have fun, I am !!
Put in my phono as a source on my VOTTs Friday PM, after six months exclusively of decent digital. OMG !!!! No comparison, ole' analogue rules !! Thats good, because I have about 9 to 10,000 lovely LPs at home. Bring them on . Maybe time to do a Lenco mod on my L-75 spare table.
Jeff Medwin
Edits: 05/21/16 05/21/16Follow Ups:
Yea that's a chicken under the table. :-)
Now I know why you have that moniker, LOL!
The chassis was a good find.
.
Jeff, 6av5 is the power tube, Screen tied to plate. Driving it is a 6dj8 with ~145v plate vdc. The amp has four octal sockets, two with Eia base 6ck (6av5ga) and two sockets 7ac base pinout (6L6/kt88) It can run either type as finals. I have a 20k ohm shunting pot to juggle driver tube plate voltage and vary finals bias. I need to add some form of thd analysis to measutement tools. Still doing some A/B listening tests...JH
Nice work. Please post a schematic if possible.
Regards,
David
OK,
There was a "6 something " designated tube, that is equal to half a 12AX7. I didn't check the designation, and THOUGHT ( by mistake ) that the 6AV5 was the driver, a high mu tube, low current, and a 6L6G was the finals.
The amp chassis looks pretty outside in your back yard / daylight photos.
Jeff
Close.
8^)
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