Hi guys,
Is it possible to change this buffer to have about 12db gain without sacrificing sonics.
One channel shown.
Is it possible to change this buffer to have about 12db gain without sacrificing sonics.
One channel shown.
This is not a buffer. It's a common cathode stage into a cathode follower. It already has gain of around 11x. This seems way more than enough for a line stage. What are you trying to drive?
Yep you could make R5 say 100K and increase R8 to get about the same plate voltage on C1A/C1B. If that not enough change C1A/C1B for a 12AT7 and again adjust R8 for the correct voltage.
Are you sure it has about 11x gain.
I connected it directly to the 2v rms output of my DAC and it is at most 6db louder than going from the DAC straight into the amp.
Try to put a 100 uF 25Vdc across R8 , 1kohm
You will get around 2 dB more gain and it is a simple and fast solution
Gain should be around x11. The output impedance is around 2k.
What is the input resistance of the amplifier? It may be loaded down.
What is the input resistance of the amplifier? It may be loaded down.
Tubes used in the 1st & 2nd stage are in the wrong position to drive the load properly.!
AU7 should be used to drive the load, AX7 as a simple gain stage. 🙂
AU7 should be used to drive the load, AX7 as a simple gain stage. 🙂
Input connected directly to a DAC should have a coupling cap when there is DC. Also input filtering and attenuation of input signal could be necessary.
It helps to mention what the purpose is and what amplifier/load is used as normally standard input sensitivity amplifiers can be connected to sources without inserted gain stages with worse drive capability than the sources have. With a possible 22V rms output level a great many amplifiers (even pretty insensitive ones) can be overdriven extremely and noise & hiss possibly will be way louder than normally accepted.
A wire from J2 pin 1 to J7 pin 1 will not sacrifice sonics as much.
It helps to mention what the purpose is and what amplifier/load is used as normally standard input sensitivity amplifiers can be connected to sources without inserted gain stages with worse drive capability than the sources have. With a possible 22V rms output level a great many amplifiers (even pretty insensitive ones) can be overdriven extremely and noise & hiss possibly will be way louder than normally accepted.
A wire from J2 pin 1 to J7 pin 1 will not sacrifice sonics as much.
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I Measured a few times. CS43198 seems to have no DC on it's output. My tube pre has input caps so it's a non issue anyway.
Can it be that you have a rather strong misconception about tube gear?
If I put the tube pre on the output of any of my DACs skipping the opamps the Instruments are clearly more defined and the stage gets more depth. All this without any loss of detail. I want to be able to use the tube pre with a certain amount of gain that's why I'm asking for help.
I slowly get the feeling that things like stage depths and precise imaging are something you have not yet experienced at your place.
But I'm just assuming.
I certainly haven't had clearly located sound sources even on good recordings for many years of my audio journey.
Clarity yes
Center image of singers yes
But all other instruments where just there between the speakers without occupying any specific place.
Can it be that you have a rather strong misconception about tube gear?
If I put the tube pre on the output of any of my DACs skipping the opamps the Instruments are clearly more defined and the stage gets more depth. All this without any loss of detail. I want to be able to use the tube pre with a certain amount of gain that's why I'm asking for help.
I slowly get the feeling that things like stage depths and precise imaging are something you have not yet experienced at your place.
But I'm just assuming.
I certainly haven't had clearly located sound sources even on good recordings for many years of my audio journey.
Clarity yes
Center image of singers yes
But all other instruments where just there between the speakers without occupying any specific place.
The input caps are not in the schematic or do you mean it is followed by yet another preamp with again gain? BTW it would not be a non issue if the pictured gainstage would have DC at its inputs regardless of what the following stuff may think of that.
Indeed assumptions. More often the misconceptions are on the account of the person who implements superfluous gain stages and/or effect generators. Usually they then appear as threads here with one or more issues.
There used to be an excellent sticky on gain structure by Pano but I can not find it right now.
Indeed assumptions. More often the misconceptions are on the account of the person who implements superfluous gain stages and/or effect generators. Usually they then appear as threads here with one or more issues.
There used to be an excellent sticky on gain structure by Pano but I can not find it right now.
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Found it. A good read:
It would be a good idea to speak about the preamp (it is not a buffer) and correct implementation/correct gain structure of various blocks in the complete chain. Not about a person or his/her abilities to hear or not hear last weeks fashion in audio. Play the ball, not the man.
It would be a good idea to speak about the preamp (it is not a buffer) and correct implementation/correct gain structure of various blocks in the complete chain. Not about a person or his/her abilities to hear or not hear last weeks fashion in audio. Play the ball, not the man.
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17.5 dB is more than the required 12 dB so something is not right. Signal level should already be what normal power amplifiers usually can deliver. I am afraid necessary information of the other gain blocks to determine what is not OK is lacking. Usually not keeping to standards plays a part in such issues.
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Whether the circuit given has a gain of x11 (21dB) or x7.5 (17.5dB), both are much more than the requested 12dB.
No problem here, other than the identification of a gain stage as a unity gain buffer.
No problem here, other than the identification of a gain stage as a unity gain buffer.
The problem here is mentioned in post #5 to be insufficient gain. Quite odd as the 7.5/11x preamp is connected to a 2Vrms DAC directly so without volume control. With a volume controlled power buffer instead of a power amplifier behind it it should already be too loud.
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