• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Help Needed: Lower Gain on a Tube Amp?

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Hi everyone, Can someone with some Smarts please help me figure out how, if possible to lower the gain on a very simple tube headphone amplifier circuit. I have very limited(basically zero) knowledge when it comes to eletronics and circuits on how they work etc. All I am good at is following instructions with great soldering skills.
The amplifier is a old Antique Sound Lab MG-HEAD OTL Headphone amp that I woke up from the dead. It was collecting dust for many years and now I want to try use it again. Back in the day, I did mod the crap out of if. It still works great except it would be real nice if I can lower the gain somehow because as of right now, when I turn volume very slight it gets too loud to quick. It always had this issue. The only way I knew years ago to change gain was to install a lower gain tube which works but is limited. I am sure (hope) that it is as simple as changing a ground resistor value, but which one? Please help.
Here is schematics. This is a DT version and mine is OLT version . Exact same circuit but not shown is the added OTL output added which should not matter to change gain.

mg head otl - Google Search
To change input tube, it's need more skill how the tube works.
Simple is to put R divider on the input: Connect serial two resistor /for ex./ 220 kohm each. One end connect to middle point of potentiometer, second end - to ground and middle point of 220 & 220 kohm - to grid of input tube.
Install 100 KOhm 1% tolerance resistors in the lines between the I/P jacks and the "tops" of the volume controls. The additional resistance attenuates the I/P signal by 6 dB. No more "hair trigger" volume control! :D

While the unit is on the bench, consider replacing D1 through D5 with UF4007s. The OEM parts generate a good deal of switching noise. UFnnnn parts are drop in replacements for the corresponding 1Nnnnn parts that generate much less switching noise.
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