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Amp Camp Pre+Headphone Amp - ACP+
Amp Camp Pre+Headphone Amp - ACP+
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Old 22nd June 2020, 02:53 AM   #361
6L6 is offline 6L6  United States
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Amp Camp Pre+Headphone Amp - ACP+
Try connecting it with the headphone jack to bypass the 33r on the output of the RCAs...

It's worth a shot.
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Old 22nd June 2020, 12:18 PM   #362
nicoch58 is offline nicoch58  Europe
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Quote:
Originally Posted by autox View Post
Hi,

The DC resistance I measure on the two coils is 63R and 490R,
never misure the coil you can magnetize the core
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Old 22nd June 2020, 07:55 PM   #363
autox is offline autox  United States
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Well whady'a know - bypassing the output resistor did the trick! And by using the center tap on the input coil, I can still show ~30R to the ACP. Now I just need to figure out how to do this inside the chassis so I don't have to live with a headphone cord out the front. Thank you, 6L6!

nicoch58 - thanks for pointing this out, it never occurred to me. It seems the solution is to have some idea how long you kept the ohmmeter on it, and then reverse the leads for the same duration to neutralize any field that might have stuck around. Or just drop in on a hard floor
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Old 22nd June 2020, 09:54 PM   #364
Ben Mah is offline Ben Mah  Canada
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Amp Camp Pre+Headphone Amp - ACP+
If you want to take the 33R out of the preamp out circuit, just lift one leg from the circuit board (R16 and R17).
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Old 22nd June 2020, 10:01 PM   #365
autox is offline autox  United States
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Right - it's parallel to the load. Thanks.
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Old 23rd June 2020, 03:36 AM   #366
jmgilmore3 is offline jmgilmore3  United States
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Default Thinking Out Loud

I have been thinking about the input circuits in the F6 and M2X amplifiers. I have a fine preamp with a surface mount op amp headphone output circuit.
I was thinking I could use the 1/4" headphone jack with two conductors surrounded by a foil shield. Especially easy would be to use an amplifier fed from the headphone jack across just the windings of the phase inversion transformers. If done right I suspect you could winding from the driver transformer for a pseudo balanced connection. I have my preamp on one side of a room and the power amp could be located in another place between the speakers and the power amp cables could be really short.
I know it is not a true balanced connection but I bet it might work.

Just an idea.

Last edited by jmgilmore3; 23rd June 2020 at 03:47 AM. Reason: correct spelling and grammer errors
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Old 23rd June 2020, 03:44 AM   #367
jmgilmore3 is offline jmgilmore3  United States
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Default ACP+ used as a current mode RIAA preamp

I have been intrigued by a couple of new current-mode phono preamps. They multiply current through a differential amp and they no longer have to deal
with loading resistors and caps. So I am thinking what if you ran the phono cartridge leads through shielded cable for each half of the cartridge and use a modified ACP+ as the differential amplifier and add an RIAA Equalization network and maybe a buffer for the output.

I just wanted to share what I was thinking about.
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