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Audio Research vt100mkll question

I wonder if someone has experince of this ??

Two questions really.

I've just bought a vt100 mkll and am running it with single ended input from the source , with-out the pins in the balanced input. It seems to work ok just wondered if there was any down side to this ?? Should it work at all ??

Also My amp has been re-valved with 6h30's instead of the original 6922s. Is this a good thing as the 6922's are a lot less current hungry than the 6h30's ?? Will it work properly ??

Over-all the amp is proving harsher than I expected on leading edge vocals and sounding a touch bright. (could the valve be causing this ??) I'm driving proac 3.8s . Bass is good and some things sound very, very good.

Any opinions would be appreciated.

Thanks for your time.
borg7x9
gmorris
351 posts
 
Borg:

If the input tubes are not properly balanced and adjusted you will not be able to adjust the output tubes to the specified 130 mV.

I would first re-checek the input tubes before shipping off the VT100 for repairs.
borg7x9 OP
91 posts
 
Gmorris,
Thanks for the info. The guy who gave me the jj tubes has a test bed that I can use. He has offered to go through the adjustment processes with me. I'll do that this weekend. He also has a large collection of tubes that he's offered to lend me to try, which might be interesting.

Myron.
gmorris
351 posts
 
You should also check the 1 Ohm resistors R37/R38 AND R43/R44 (in series with the anodes of the output tubes. (Sometimes they look ok from general inspection, but can be defective.)

Also check the 100 Ohm resistors R39/R40 AND R45/R46 (same comment as above)

I keep a bunch of these resistors (can order from ARC). These are the first to go if there is an arching problem.
sirspeedy70680e509
1,064 posts
 
Borg,I have a pal with your amp,driving NOLA(ALON)Circe's.Fabulous sounding amp.I have heard it,also,drive Verity Parsifal's to a stunning degree!!

BTW-loved your "classic" matches with MacEnroe,and Connors!!Did you really have icewater in your veins??
borg7x9 OP
91 posts
 
Update.............. More Help please.

A technician friend and I have dialed in the 6922's almost perfectly. Plus we tested individual tubes to look at plate current etc. All looks good apart from one 6550c running a bit hotter than the rest. (see I even know the terminology now).And one 6922 being quite suseptable to microphony.

However the problem I have is this.... on the .5 Ohm resister which is the testing point for the bias adjustment on the power tubes I can only get max .098Mv on one channel and .122mv max adjustment on the other channel.

Has anyone had simialr problems ??

By the way Sirspeedy, Thanks for your comments Its a shame my clothing empire wasn't as successfull. Maybe I'll try hair/grooming products next.


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