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News: Come see us February 11, 8-5 at the Head-Fi meet at the Burlingame Double Tree Hotel, Burlingame, CA. We'll be bringing lots of headphones and amps, and our prototype tube DAC used with our music server and the latest version of Amarra.

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Author Topic: Quickie for Tape or Phono  (Read 601 times)
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xcortes
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« on: June 01, 2010, 08:33:57 AM »

I'm thinking of experimenting with a pair of Quickies and make a couple of mono tape preamps.

My idea is to insert the eq circuit between the two sections of each amp. I will basically build the tape eq section of the Seduction for which I would (from memory as I don't have the schematics in front of me):

Replace the pot in the first section with a 250k trimpot.
Replace the pot in the second section with a 1M resistor.
Between the two stages I will install a a passive equalization network composed of a series resistor R1 of 66Kohms and a series-shunt network composed of a 1.5Kohms for NAB (1.07k for IEC) resistor and .033uF cap.
Use a 0.1 uF coupling capacitor.

The main problem I see is gain since the 6DJ8 has an amplification factor of 33 vs about 5 for the 3S4.

Any comments?
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Xavier Cortes
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« Reply #1 on: June 01, 2010, 09:42:46 AM »

The gain will be too low. PJ has suggested in the past that he might look at the feasibility of a battery powered tube phono preamp, but it is not a high priority at the moment.
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Dan "Doc B." Schmalle
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