I'm getting 110db s/n from my 6922 preamp
Hum is below the hiss.
Cap multiplier works as good as batteries 125v B+ AC heater 20 volt heater lift
Hum is below the hiss.
Cap multiplier works as good as batteries 125v B+ AC heater 20 volt heater lift
Do you have a schematic of what you are talking about, stocktrader200? I don’t know what my signal to noise ratio is, but when I plugged this into my sound board the hum problem that I had with a conventional power supply was eliminated. I hope that doesn’t mean the preamp will lose some of the sound benefits without the hum. I’m still studying it.
stocktradeer200,
Great s/n!
Is that the tota integrated noise across the 20Hz to 20kHz frequency range?
What is the test equipment you are using?
Thanks!
Note: The noise power that is measured in an FFT's 100Hz Resolution filter, is about 23dB less than the integrated noise power in 20,000Hz bandwidth.
Great s/n!
Is that the tota integrated noise across the 20Hz to 20kHz frequency range?
What is the test equipment you are using?
Thanks!
Note: The noise power that is measured in an FFT's 100Hz Resolution filter, is about 23dB less than the integrated noise power in 20,000Hz bandwidth.
Hi, I tried this using a 20 VDC supply to power this, and the lm317 is getting way too hot. I tried a 20w dropping resistor, and it was getting too hot, too.
I have an electronics manual that shows a circuit which uses a 2n2219a with a 6.8 zener diode. Do you have any advice?
Linear power supplies will always burn power according to the quantity V x I,
where V is the DC voltage drop across the regulator, and I is the DC current through it.
There's no way around that. Your 2219 series pass regulator circuit will just move the heat to the 2219 instead.
Of course, heat sinks can be used to move some of the heat from the device to the sink.
where V is the DC voltage drop across the regulator, and I is the DC current through it.
There's no way around that. Your 2219 series pass regulator circuit will just move the heat to the 2219 instead.
Of course, heat sinks can be used to move some of the heat from the device to the sink.
Even "simple" circuits such as this can have problems with regard to physical layout and wiring...can you post some pics?
Mike
Mike
Three stage cap multiplier with Ksc3503 eliminates the line noise.
Three low gain stages deliver the high s/n ratio.
The first triode puts 10v p-p to the volume pot.
2nd triode drives tone stack, 20db power amp gain.
Dead silent 3 inches from speakers 92 db/w/m
Can detect faint hiss ear pressed to tweeter.
I have to amplify the output 10x for noise to become visible on scope
Three low gain stages deliver the high s/n ratio.
The first triode puts 10v p-p to the volume pot.
2nd triode drives tone stack, 20db power amp gain.
Dead silent 3 inches from speakers 92 db/w/m
Can detect faint hiss ear pressed to tweeter.
I have to amplify the output 10x for noise to become visible on scope
I’m not interested in trying to use a conventional power supply anymore. This works to get the hum out. I need to find a way to power the filaments without so much heat being generated. I used a big heat sink, and it felt hot enough to start a fire. I’m trying to power two 12ax7s.
If this circuit has worked with the normal type of linear supply, why do you insist that it needs changing? I'd still take a good hard look at the physical layout...are the transformers to close to sensitive components or orientated in the wrong direction? Do you have relatively high current wiring, like for the heaters, wired correctly and not routed near signal wires? Things like "star grounding" are not a panacea and won't always work well in every type of circuit...perhaps there's an internal ground loop, or a ground loop caused by the connections to other gear. Again, a picture or three is worth more than most of what's been written here.
Mike
Mike
Switching supplies can add noise and affect radio reception. I chose to keep the 5v linear regulator in SX3700 for digital display.
There is something wrong with powering a tube with a dc to dc converter and eliminating the need for a transformer. Certainly, after I get it working with a 20 v battery I’ll try a 20 v wall wart. I’ve been studying this circuit for more than 20 years.
I didn't mention a DC to DC converter. Have you been having this same problem for more than 20 years?
Mike
Mike
It doesn’t matter what parts you use. A linear regulator or a simple resistor does the same thing, turn the excess voltage into heat. Either use a switching regulator or less supply voltage.
Hum has been a problem for 20 years. I just now figured how to use a dc to dc converter.