That isn't how the circuit works. A different tube will screw up the frequency response.
If you need more gain, then you need an input step-up transformer (or other gain device).
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=124746&start=48
If you need more gain, then you need an input step-up transformer (or other gain device).
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=124746&start=48
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My understand of this circuit design suggests that the first tube controls the gain. The second tube is part of the EQ circuit, and the final tube is a buffer.
Also, I am looking to reduce the gain of the unit.
Also, I am looking to reduce the gain of the unit.
Yeah, V1 is outside the RIAA feedback loop, and looks like a pure gain stage. Maybe try a 12AT7 for less gain.
Is this a real 824p or a clone?
jeff
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.
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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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.
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.
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.
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 🙂
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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An L-pad is never used at the input of a phono preamp. It would increase the noise level
directly in proportion to the amount of attenuation.
Also the high frequency response would be reduced due to the input capacitance
of the first stage loading the L-pad.
Really the only logical place to put a pot would be on the output. I came across a clone board that even had provision for a volume pot. The builder just used an Alps 100k.
jeff
Actually, it has over twice the output of the active B1 buffer in my dac. Many have complained about it.
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.
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