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Old 3rd May 2012, 08:51 PM   #161
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"Here is the schemeatic. Have at it."

It looks like the tubes are just there for marketing reasons.....
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Old 3rd May 2012, 08:52 PM   #162
jim1961 is offline jim1961  United States
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Originally Posted by Palustris View Post
"Here is the schemeatic. Have at it."

It looks like the tubes are just there for marketing reasons.....
Explain?
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Old 3rd May 2012, 09:09 PM   #163
SY is offline SY  United States
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Nearly everything in that unit is done by opamps. Lots of opamps. The tubes are just tacked on and have very little function (a flat gain stage).
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Old 3rd May 2012, 09:11 PM   #164
jim1961 is offline jim1961  United States
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Nearly everything in that unit is done by opamps. Lots of opamps. The tubes are just tacked on and have very little function (a flat gain stage).
OK. But it does appear 12at7's are the right tube, yes?

btw...its an EQ. Doesnt need gain. Or is that what you mean?
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Old 3rd May 2012, 09:38 PM   #165
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Equalizers generally need gain in each of the EQ blocks to get the frequency response tailoring via negative feedback. Most EQs also have one or more flat gain stages, though these aren't completely necessary, they're there to accommodate the great variety of equipment that the box COULD be connected to.

The schematic shows 12AT7. You might want to confirm (e.g., from rev number or a call to the factory with your serial number in hand) that your unit has the circuitry indicated in the schematic.
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Old 3rd May 2012, 09:44 PM   #166
jim1961 is offline jim1961  United States
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Quote:
Originally Posted by SY View Post
Equalizers generally need gain in each of the EQ blocks to get the frequency response tailoring via negative feedback. Most EQs also have one or more flat gain stages, though these aren't completely necessary, they're there to accommodate the great variety of equipment that the box COULD be connected to.

The schematic shows 12AT7. You might want to confirm (e.g., from rev number or a call to the factory with your serial number in hand) that your unit has the circuitry indicated in the schematic.
Thanks for taking a look.
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Old 3rd May 2012, 10:07 PM   #167
DF96 is offline DF96  England
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Not really a flat gain stage. DC supply is only 45V and the valve is run at a rather low current. The cathode follower appears to have a load of 1M, plus a Darlington EF. Then the EF output seems to be fed back to the first triode grid. This looks like FX to me: "tube sound"? Or possibly only cosmetic, but with the signal fed through it to guarantee deniability. You certainly would not design it like that if you wanted a serious gain stage or a genuine buffer.
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