• 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.

Lowering Gain on EAR 834p

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Joined 2011
If you want less gain, just use the following volume control.

The first tube (V1) stage is actually part of the RIAA feedback loop.
It is NOT outside the RIAA feedback loop. In fact, this stage creates
an active source impedance that is a critical feedback element which
sets the closed loop gain.

All the 834 circuit parameters are tuned for best performance of that topology,
and cannot be changed without substantial degradation. This includes the tubes.
 
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Joined 2011
As mentioned in post #6, changing the tubes or parts values will ruin the circuit tuning,
and strongly degrade the performance. All you can properly do to lower the phono stage output
is to add a two resistor L-pad after the 834, which is equivalent to adjusting the volume control.
The 834 design load impedance appears to be 100k. This would allow you to have a similar volume
control position for phono and other sources, but would not otherwise change the operation of the 834.
 
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Joined 2011
A two resistor L-pad, when loaded with your line stage, should present a 100k load to the EAR 834.
Lower values of loading than 100k will increase distortion and reduce the lower bass range.

However, due to interconnect cable losses, it is best in install the L-pad in the line stage,
rather than in the 834, if they are in separate enclosures.
 
2 things. 1. L-pads cost more than simple volume pots, so I want to stick to the latter. 2. I don't have a preamp currently, but plan to build one. Do to the huge difference in output between my dac and phonostage, I want to add a separate trimpot at one of the inputs of the preamp to host this unit.
 
No , you should use values for tube circuits , like 500K , 1M
And must be put in the next preamp box , so the low output impedance of this circuit would be able to drive the cables without losses

But I don't expect for this circuit to have a very high output level , maybe aroud 150mV rms . So your DAC output could be too low :)
 
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You can insert a series resistor R2 after the cap/resistor R1 combo to reduce the AC gain as long as the R1 and R2 resistor values equal to 2M total, however combination that suits your desired gain, as long as the DC voltage at green dot is the same as as before. You can of course use 1M for R1 and a 1M pot, with wiper at the coupling cap, for R2 to adjust to your desire gain and then replace them with fixed value resistors.


EAR-834-P-less-gain-schema-1280x720.png


EAR-834-P-mod-reduce-gain-pot-schem-1280x720.png
 
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