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Audio Research tube problem with Aragon 4004 MKII

Retubed my SP 8 and the tube company had no 12bh7s, but showed an Ecc99 as a direct substitute. Put the new tubes in, got a low volume buzz through both channels, and even though the volume was down, my Aragon 4004 MkII sparked and died. Tube company says they have had to problem with that substitution, but has sent a different 12bh7. (Replaced my original in a makeshift system, and it worked fine with the old tube). Anyone had any experience? Have heard Aragons had some sensitivity to DC offset, and my 4004 has had the relay chatter numerous times in the past making me wonder whether it's protection stage was adequate.
chidancer
johnss
577 posts
 
I had a similar problem as Kenscollick did.

If you are set on using a tube pre with the 4004, you'll need to add a DC blocking cap for both channels. I know' direct is supposed to be better, but in this case, your options are limited. Add a film cap to the 4004 inputs and enjoy your tube pre.
chadnliz
3,736 posts
 
I use a Sonic Frontiers Tube Pre, and used others in past with my Aragon 4004MKII and never have had a problem so I am suspect of Johns claim you have to add DC blocking cap.
blazim
2 posts
 
I have used an SP-6b with an Aragon 2004 MK11 without problems for more than three years... NO HUM. I also have an SP-9 MK 3 (with GNS ref mods) also with NO PROBLEMS now for two years. I have coupled these with Precision Fidelity M-8 amps also with out a problem.
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