Hi all
Maybe it's about 2 years left since my 6c33 SET diy complited🙂
It's sounds so good with zero negative feedback and 12bh7 as driver and 12ax7 as pre/first stage
No noise and exactly no 60Hz hum !
Sth like a pop-sound that can be heard from speaker, is annoying me when i turn the amp off
I don't know how to solve it
I've checked whole net but topics wasn't related or useful with tube amps
Can anyone please help me in this way to solve it?
Thank u
Maybe it's about 2 years left since my 6c33 SET diy complited🙂
It's sounds so good with zero negative feedback and 12bh7 as driver and 12ax7 as pre/first stage
No noise and exactly no 60Hz hum !
Sth like a pop-sound that can be heard from speaker, is annoying me when i turn the amp off
I don't know how to solve it
I've checked whole net but topics wasn't related or useful with tube amps
Can anyone please help me in this way to solve it?
Thank u
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At a time i used a 47 uf cap in series with a 50 ohm resistor
And then paralleled it ro the switch,nothing changes
In both switch on/of the transformer was workin due to electricity path of ac voltage that crosses from cap...
And then paralleled it ro the switch,nothing changes
In both switch on/of the transformer was workin due to electricity path of ac voltage that crosses from cap...
47uF and 50 ohm?
Assuming this is the power switch try something on the order of 0.01uF - 0.047uF in series with 10 - 100 ohm across the power switch. The capacitor should be an x cap. You can also purchase RC snubbers from DigiKey or Mouser and solder across the switch.
You might also look at where power wiring is routed relative to audio input wiring and circuitry.
Photographs showing construction details, schematics, etc are always helpful.
Is this built in a metal chassis box or a wood box with metal top plate?
I am going to assume you do not have a scope and have not looked at what is happening when you turn the power off.
I would hope there is no 50Hz hum since U.S. power is 60Hz. 😀
Assuming this is the power switch try something on the order of 0.01uF - 0.047uF in series with 10 - 100 ohm across the power switch. The capacitor should be an x cap. You can also purchase RC snubbers from DigiKey or Mouser and solder across the switch.
You might also look at where power wiring is routed relative to audio input wiring and circuitry.
Photographs showing construction details, schematics, etc are always helpful.
Is this built in a metal chassis box or a wood box with metal top plate?
I am going to assume you do not have a scope and have not looked at what is happening when you turn the power off.
I would hope there is no 50Hz hum since U.S. power is 60Hz. 😀
Thank u sir,i recorrected it cause that it was typed wrongly
Seems that i used too high value for capacitor in series with a resistor
It assembled on a aluminium plate that fixed on wood chassis,the lower plate with aluminium to.
I'm dropped into trouble
You know
Everythings good,and sounds in a best way that i expect
But this issue is gonna a big question and seems that it's hard to solve...
Turn off transients are pretty common in designs with solid state supplies, photographs of how you built it might allow others to provide suggestions on how to improve it.
I direct drive my mid and HF horns without protective capacitors and designed and constructed 300B dht power amps to do this about 3 years ago, they generate very minimal turn off transients. The GM70 bass amps generate a significant turn off transient, but not one that is a cause for concern.
You may need to shield power and signal level wiring depending on how you built it, hard to know without schematics and pictures.
I direct drive my mid and HF horns without protective capacitors and designed and constructed 300B dht power amps to do this about 3 years ago, they generate very minimal turn off transients. The GM70 bass amps generate a significant turn off transient, but not one that is a cause for concern.
You may need to shield power and signal level wiring depending on how you built it, hard to know without schematics and pictures.
It might be not the sparc from the power switch but the surge when the single ended output transformer loses it's current.
This is a problem with SE amps.
A relay that shorts the speaker outputs when power drops might be a solution.
Try this troubleshooting idea, isolate the different parts of the system . . .
Perhaps the power amplifier's mains turn-off transient is getting "upstream" into the signal source:
A turntable/cartridge
A phono preamp
A line level preamp
etc.
Disconnect all signal sources from the power amplifier's inputs.
Select one input (if there is a selector switch), and plug in a shorting RCA / XLR plug at that input.
Turn on the power amp, let it warm up fully.
Then turn off the power amp, is there still a Pop! this time?
If not, the problem is another (upstream) device is picking up the power mains turn off transient.
Perhaps the power amplifier's mains turn-off transient is getting "upstream" into the signal source:
A turntable/cartridge
A phono preamp
A line level preamp
etc.
Disconnect all signal sources from the power amplifier's inputs.
Select one input (if there is a selector switch), and plug in a shorting RCA / XLR plug at that input.
Turn on the power amp, let it warm up fully.
Then turn off the power amp, is there still a Pop! this time?
If not, the problem is another (upstream) device is picking up the power mains turn off transient.
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Yes, 47uF was far too much. And I hope it was not an electrolytic cap.
Did the 47uF and 50 Ohm resistor get hot?
At 60Hz, 47uF is 56 Ohms of capacitive reactance.
The total of 47uF and 50 Ohms in series across an open on-off switch is about 70 Ohms.
120V / 70 Ohms = 1.71 Amps of current.
The only limit to that current is the impedance of the amplifier's transformer primary when the amplifier is off/cold.
For example, if the primary impedance is 100 Ohms when the amp is cold, then the (off) current would be
120V / (70 + 100 Ohms) = 0.7 Amps!
Did the 47uF and 50 Ohm resistor get hot?
At 60Hz, 47uF is 56 Ohms of capacitive reactance.
The total of 47uF and 50 Ohms in series across an open on-off switch is about 70 Ohms.
120V / 70 Ohms = 1.71 Amps of current.
The only limit to that current is the impedance of the amplifier's transformer primary when the amplifier is off/cold.
For example, if the primary impedance is 100 Ohms when the amp is cold, then the (off) current would be
120V / (70 + 100 Ohms) = 0.7 Amps!
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Sure
Attachments
Yes
Actually they got hot
When there were no load on main power transformer,the output voltages reach about 60% of their main value
Actually i made this circuit
But it's not fast enough
To diconnect the output speaker from amp,while the main power switch want to turn off !!
Attachments
Is that a motorized volume control pot near the output connections? If so I would move that closer to the driver stage and as far away from the outputs as possible. It may not fix the problem but it is a step in the right direction.
I also see what appears to be some power supply circuitry mounted directly on top of a red capacitor which presumably is part of the driver circuit. I'd move that too.
I did not see any power wiring or it's relationship to input wiring or circuitry. (Can you post a few more pictures?)
It's a tidy job though.
I also see what appears to be some power supply circuitry mounted directly on top of a red capacitor which presumably is part of the driver circuit. I'd move that too.
I did not see any power wiring or it's relationship to input wiring or circuitry. (Can you post a few more pictures?)
It's a tidy job though.
With your additional circuits, you could add a "bypass" switch (as in a tube amplifier for power supply of filaments). I mean, a switch that drives the relays. So:
ON :
- Main Switch to switch the AC mains into your amp
- then the second switch to enable the relays that are going to connect output of amplifier to speakers.
OFF:
- Switch to disable the relays and disconnect the output of amp from speakers.
- Main Switch to power OFF the Amp.
Don't know if it could work but it's an idea. Maybe a 100k to, 1M resistor in // of speaker should be adding ???
I have had some mishaps shorting output transformers with burned up relay or switch contacts, what I have found that works is a 75 - 100 ohm resistor across the secondary (8 ohms) then if the output goes open whether deliberately or by accident you don't get a really big flyback voltage across the primary.
I prefer the snubber across the transformer in place of across the switch, by two reasons: the set continuously drains current from the mains, and also this leak maintains some potential across the transformer and then, some DC unknown potential in the rectifiers. Putting it across the transformer's primary it doesn't happens.
Please use a scope in single sweep triggered mode to measure the turn off pulse.
How many volts is it?
+ Volts peak?
- Volts peak?
How fast is the rise time?
How fast is the fall time?
Suppose that it is not dangerous to your speakers.
They seem to have survived for 2 years, and your ears have too.
It might be better to learn to live with it, versus modifying the amplifier.
There is nothing that can not be improved by adding to the complexity and cost of an amplifier.
The solution may also bring increased failure rates, and decreased performance, just to get silent operation.
Did you prove that the turn off transient is not system related, and is only caused by the amplifier by itself?
System ground loops are wonderful (not wonderful) creators of transient receivers.
Please see my Post # 11.
How many volts is it?
+ Volts peak?
- Volts peak?
How fast is the rise time?
How fast is the fall time?
Suppose that it is not dangerous to your speakers.
They seem to have survived for 2 years, and your ears have too.
It might be better to learn to live with it, versus modifying the amplifier.
There is nothing that can not be improved by adding to the complexity and cost of an amplifier.
The solution may also bring increased failure rates, and decreased performance, just to get silent operation.
Did you prove that the turn off transient is not system related, and is only caused by the amplifier by itself?
System ground loops are wonderful (not wonderful) creators of transient receivers.
Please see my Post # 11.
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