I am disappointed that you could not see any problem with my build. As you say, it is so simple it is hard to understand why it is not working properly.
As far as the input voltage is concerned, I would expect it to be able to take at or near 2v (normal CDP output.) If it can only take .775v, it is not going to be any use to me, because at that input level, there is not nearly enough output.
I currently have an opamp gainstage running in exactly the same situation that this design was in. It has about the same gain (x11) and it is operating perfectly. (Only the sound is not quite perfect).
If you think of anything else, please let me know.
Thanks,
William.
As far as the input voltage is concerned, I would expect it to be able to take at or near 2v (normal CDP output.) If it can only take .775v, it is not going to be any use to me, because at that input level, there is not nearly enough output.
I currently have an opamp gainstage running in exactly the same situation that this design was in. It has about the same gain (x11) and it is operating perfectly. (Only the sound is not quite perfect).
If you think of anything else, please let me know.
Thanks,
William.
hihopes said:
William,
I could not see from your sketch the joints and wires.
the circuit should look similar to attached by me (sight from top).
if your circuit is built good and you still got clipping (I cannot find the reason?) you shoud use +30V voltage supply and regulate +16V at the drain of the fet.
Attachments
The circuit is built on stripboard, with the strips running across from left to right as you view the drawing. Straight vertical lines are jumpers.
I will examine your layout closely and see if there is anything different. I already upped the voltage from 16.8 to 21v without any change in behaviour.
I am thinking that the clipping is coming from my active crossover (which runs from a single rail 14v supply). Perhaps because this design was producing more bass than the opamp, clipping was setting in at a lower setting of the attenuator. I have been experimenting with a bunch of different gain settings today and it does also clip with the opamp - just at a higher input level. I have different chips I can try in the crossover - perhaps that will improve things a bit. Ultimately, I think I will have to build a decent active crossover, and that will probably solve my problem as well as improve the sound.
Thanks a lot for your help.
William.
I will examine your layout closely and see if there is anything different. I already upped the voltage from 16.8 to 21v without any change in behaviour.
I am thinking that the clipping is coming from my active crossover (which runs from a single rail 14v supply). Perhaps because this design was producing more bass than the opamp, clipping was setting in at a lower setting of the attenuator. I have been experimenting with a bunch of different gain settings today and it does also clip with the opamp - just at a higher input level. I have different chips I can try in the crossover - perhaps that will improve things a bit. Ultimately, I think I will have to build a decent active crossover, and that will probably solve my problem as well as improve the sound.
Thanks a lot for your help.
William.
Dear William
I can see that your hopes were high during building this preamp
😉
I like this circuit because the sound was similar to sweet tubes, even more detailed.
if you rised supply voltage please remember about regulatin it at above half on the drain.
I can see that your hopes were high during building this preamp
😉
I like this circuit because the sound was similar to sweet tubes, even more detailed.
if you rised supply voltage please remember about regulatin it at above half on the drain.
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