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24.34.17.88
In Reply to: Personal favorite posted by grhughes on March 1, 2007 at 10:28:34:
The Steve Bench RIAA5 is pretty high on my list.What improvements did you see with the 6AN4 over the 6DJ8? What did you use for a power supply? Also, any idea of the purpose of the large input coupling cap?
Follow Ups:
and I didn't want to use a 6dj8 as the second stage.. The 6an4 seems more linear to me and the grid can even be driven positive (not that I want to try that). I built me a tube regulator using a 6080, 12bz7, and a diode tube.
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
I have got plenty of 6DJ8s so I would probably go that route first.
and he seemed to fear the prospect of loading the cartridge with DC offsets on turn on. It's probably necessary unless you use an input transformer and maybe necessary even if you use one if you don't want DC in the secondary winding. I use a Grado MM and use it direct in with no transformer. There is also a variant used by Studer in their C and J 37 tape preamps in which they used the 6DJ8 on the bottom and a weird Euro 12ax7 type up top as the grounded grid. They didn't use a input coupling capacitor. But I think it's safe to use one. Ray
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
http://www.diyaudio.com/forums/showthread.php?postid=1083419#post1083419
Post #49 the gif at the bottom. Ray
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
Ray,Thanks for the link. Some interesting ideas in that thread. I would probably start with the basic circuit on Steve's website first and modify from there. Also, thanks for the info on the input capacitor. I think a few of the builders have left it out with no ill effects.
"no ill effects"
If removing the input cap,
could DC at the input demage the transformer (Lundahl 9206), or MC cartridge (expensive !!), or are there only a risk for sound degration caused by saturated transformer core ?
Regards
Pix
or a protection should a tube expire if you are using the preamp direct in from a phono cartridge. Moving coil cartridges mostly are low impedance devices. My Ortofon MC30 can drive a 2 ufd capacitor with no signs of instability. If you're using an input transformer, I don't think it would damage the input transformer. It might magnetize a winding depending on high a voltage got into the secondary winding. Audio transformers normally don't like DC.
"I take you as you are
And make of you what I will,
Skunk-bear, carcajou, bloodthirsty
Non-survivor.
Lord, let me die but not die out." THE LAST WOLVERINE by James Dickey
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