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Best way to reduce gain in this circuit?
Best way to reduce gain in this circuit?
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Old 29th October 2019, 03:46 PM   #21
kodabmx is offline kodabmx  Canada
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Best way to reduce gain in this circuit?
The buffers drive the volume control. The impedance varies with the position.

Starting to think replacing the 1M grid leak with two 510k and tying the midpoint to grid is the best idea.
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Old 29th October 2019, 04:13 PM   #22
Lampie519 is offline Lampie519  Netherlands
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This will add noise, try a current source on the first tube's cathode instead of a resistor.
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Old 29th October 2019, 04:27 PM   #23
TheGimp is offline TheGimp  United States
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Won't that increase gain?
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Old 29th October 2019, 05:33 PM   #24
rayma is offline rayma  United States
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Quote:
Originally Posted by Lampie519 View Post
This will add noise, try a current source on the first tube's cathode instead of a resistor.
This would upset the operation of the circuit. Top and bottom parts must match.
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Old 29th October 2019, 05:34 PM   #25
rayma is offline rayma  United States
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Quote:
Originally Posted by kodabmx View Post
Starting to think replacing the 1M grid leak with two 510k and tying the midpoint to grid is the best idea.
I would keep those parts as low in value as possible to preserve bandwidth.
Hopefully the source can drive 100k.
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Old 29th October 2019, 05:35 PM   #26
rayma is offline rayma  United States
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Quote:
Originally Posted by Lampie519 View Post
Put the volume control between the gain stage and the buffer (Floating DC).
It does not reduce the gain but it does not ruin your buffer stage.
That would upset the operation of the circuit. The input stage must be unloaded.
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Old 29th October 2019, 05:40 PM   #27
Lampie519 is offline Lampie519  Netherlands
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A current source is a very high value resistor and as long as the current matches (bias voltage same) there should be no problem. As the anode load is a cc, this can be done on the cathode side as well, looks similar to a phase splitter, without gain. As there is a buffer as well there is no issue with the load of this circuit.
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Old 2nd November 2019, 04:00 AM   #28
kodabmx is offline kodabmx  Canada
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Best way to reduce gain in this circuit?
For those who are interested. My final solution was to replace the 1M on the input with a voltage divider make from two 33k resistors. Works perfectly...
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Old 2nd November 2019, 04:08 AM   #29
stocktrader200 is offline stocktrader200  Canada
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place a resistor 40% the value of your volume pot between the pot and the 10uf output capacitor.
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Old 2nd November 2019, 04:10 AM   #30
rayma is offline rayma  United States
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Quote:
Originally Posted by kodabmx View Post
For those who are interested. My final solution was to replace the 1M on the input
with a voltage divider make from two 33k resistors. Works perfectly...
Yup.
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