Humming 336 Darkvoice
Got my self one of these humming dark voices this thread was originally about.
Here is one picture of one of these, that they tried to stop the humming using an electrolytic cap across the cathode resistor.
Those two black straight wires are the AC heater supply.
The left one is dumped unceremoniously direct to rectified ground.
The right one goes to the power on diode at the front.
And note the possible induction path - right heater supply -> soldering point nearly in touch with the cathode resistor, resistor -> ground -> left heater supply.
The red wire goes to the power on diode.
And this guy has tried to get rid of the hum with some electrolytic´s across the resistors.
Well, a proven way, but needs some foil caps over the resistors, too.
But still the sound quality may take a hit because of that - straight resistors are usually better.
And I think it is a bit unusual to have the front diode circuit between heaters and connected to ground.
This thing is reasonably built, otherwise - big unmarked orange foil caps keep B+ away from your phones and your ears.
[url=https://imgur.com/jpdbvVh[/url]
And my 336 is a bit differently built, but still hums and modulates the signal.
[url=https://imgur.com/ZhF92mD[/url]
Will report back if I have any success with un-humming this.
Got my self one of these humming dark voices this thread was originally about.
Here is one picture of one of these, that they tried to stop the humming using an electrolytic cap across the cathode resistor.
Those two black straight wires are the AC heater supply.
The left one is dumped unceremoniously direct to rectified ground.
The right one goes to the power on diode at the front.
And note the possible induction path - right heater supply -> soldering point nearly in touch with the cathode resistor, resistor -> ground -> left heater supply.
The red wire goes to the power on diode.
And this guy has tried to get rid of the hum with some electrolytic´s across the resistors.
Well, a proven way, but needs some foil caps over the resistors, too.
But still the sound quality may take a hit because of that - straight resistors are usually better.
And I think it is a bit unusual to have the front diode circuit between heaters and connected to ground.
This thing is reasonably built, otherwise - big unmarked orange foil caps keep B+ away from your phones and your ears.
[url=https://imgur.com/jpdbvVh[/url]
And my 336 is a bit differently built, but still hums and modulates the signal.
[url=https://imgur.com/ZhF92mD[/url]
Will report back if I have any success with un-humming this.
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Thanks very much for taking the time to reply but this is an old thread and the problem was solved some time ago, if you would like
to stop any humming on the darkvoice I would suggest that you look up fitz mod, it is simply putting in two new capacitors but
I can't remember exactly where they went or what size, if you can't find the info then message me again and I will open my darkvoice
and take some photos for you.
Thanks and best wishes Ian
to stop any humming on the darkvoice I would suggest that you look up fitz mod, it is simply putting in two new capacitors but
I can't remember exactly where they went or what size, if you can't find the info then message me again and I will open my darkvoice
and take some photos for you.
Thanks and best wishes Ian
Indeed - and I am very well aware of the fitz mod, but as the original poster said, not optimal 🙂
So trying to find a better solution, maybe if I to open another thread?
This thing maybe better fits in the Tube section?
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I found that it work perfectly without any degradation of sound quality, is it just the hum from certain tubes that you are having a problem with.
Thank you!
Just me that find the construction a bit strange, then.
OK, case closed - have a nice evening!
OK, there's 3 years by now....did someone find a good solution for humming in the DarkVoice? I think the B+ should be regulated...there's the only solution I didn't try yet...
I supposed it could be a heater to cathode isolation issue, not entirely sure it still isn't, but it's a regulator tube for high voltages, I think that's also the reason for the high ammount of current needed for the heater...cathode far from heater.
If there's anyone who has solved this by rectifiying the heater, I will also do it. But I'm afraid all these complicate too much a minimalist intended amplifier...kind of Zen...
I'm not a tube expert, but I feel like there's some feedback solution (even a positive feedback?) or something like that....please correct me if I'm wrong.
I supposed it could be a heater to cathode isolation issue, not entirely sure it still isn't, but it's a regulator tube for high voltages, I think that's also the reason for the high ammount of current needed for the heater...cathode far from heater.
If there's anyone who has solved this by rectifiying the heater, I will also do it. But I'm afraid all these complicate too much a minimalist intended amplifier...kind of Zen...
I'm not a tube expert, but I feel like there's some feedback solution (even a positive feedback?) or something like that....please correct me if I'm wrong.
Happy New Year, 2023!
Still no answer yet....has everyone found the perfect schematic and mod for this amplifier? I put it on standby, but I intend to get this schematic to work these days...I think I will rebuild the amp using rectified heater supply and stabilized anode supply this time....and other tubes. I will use octal 6N8S this time...but still thinking of using some loctal tubes for driving....I recently discovered and added to my inventory:
14A4. They are single triode tubes, but the amp looks more "stereo" this way...
Still no answer yet....has everyone found the perfect schematic and mod for this amplifier? I put it on standby, but I intend to get this schematic to work these days...I think I will rebuild the amp using rectified heater supply and stabilized anode supply this time....and other tubes. I will use octal 6N8S this time...but still thinking of using some loctal tubes for driving....I recently discovered and added to my inventory:
14A4. They are single triode tubes, but the amp looks more "stereo" this way...