I have built this zen circuit as a headphone amp, all works
well except for its noise floor i use sensitive headphones and
these make the problem worse
in the power supply i have used a total of 10000uf capacitance
to tame the ripple but noise floor is still too high
whats the problem?
can you help
john
well except for its noise floor i use sensitive headphones and
these make the problem worse
in the power supply i have used a total of 10000uf capacitance
to tame the ripple but noise floor is still too high
whats the problem?
can you help
john
Attachments
AndrewT said:Hi,
just guessing, but, have you snubbered the PSU rectifier?
How about RCRC type smoothing after the recifier?
Headphones are very critical of noise and demand a very good PSRR of the amp and/or very low noise from the PSU.
"snubbered the PSU rectifier" yes
rcrc no i dont want voltage drop at the filter
i have use 10000uf should i go higher?
john
MikeB said:You might try a resistor to the gate. Eventually the mosfet oscillates.
Shouldn't the mosfet have a small resistor at the source ?
Mike
it is not oscillation, small resistor at the source? why?
john
The philosophy of this circuits is the employ of the minimal count of the components that they are in series with the audio signal.
A voltage stabilizer integrated circuit it is not adapted to this philosophy.
This amp have a very low PSRR and the supply noise
(above all without any circuit of ripple rejection) it must to be tolerate....
A voltage stabilizer integrated circuit it is not adapted to this philosophy.
This amp have a very low PSRR and the supply noise
(above all without any circuit of ripple rejection) it must to be tolerate....
richie00boy: " ... If it's hum then it may simply be a grounding issue and nothing is wrong with your circuit or PSU. I know headphones can be sensitive but 10000uF should be more than enough by a long way. ..."
AndrewT: " ... You might try a resistor to the gate. Eventually the mosfet oscillates. ... " " ... poor PSRR, simple C PSU (snubbered), and headphones are a conflicting set of requirements. ..." " ... How about RCRC type smoothing after the recifier? ..."
My suggestions:
In addition to trying a (metal film) resistor (1k ?) in the FET input gate ... AND a poly snubbing cap (about 0.5 uF) across the main PS filter cap ....
... is to add a ferrite bead to the input gate as well, as close to the gate as possible. There may be some HF noise entering the audio input stream, driving the input FET too hard.
AndrewT: " ... You might try a resistor to the gate. Eventually the mosfet oscillates. ... " " ... poor PSRR, simple C PSU (snubbered), and headphones are a conflicting set of requirements. ..." " ... How about RCRC type smoothing after the recifier? ..."
My suggestions:
In addition to trying a (metal film) resistor (1k ?) in the FET input gate ... AND a poly snubbing cap (about 0.5 uF) across the main PS filter cap ....
... is to add a ferrite bead to the input gate as well, as close to the gate as possible. There may be some HF noise entering the audio input stream, driving the input FET too hard.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Solid State
- noise floor problem