Hi
This is my recently made 6C45PE direct coupled 6C41C Single ended amp.
when I plug it on the speaker, it got hum and fizz. of course I have to near the speaker to hear it. Is this circiut OK?
please advise....
Thanks!
Coffin
This is my recently made 6C45PE direct coupled 6C41C Single ended amp.
when I plug it on the speaker, it got hum and fizz. of course I have to near the speaker to hear it. Is this circiut OK?
please advise....
Thanks!
Coffin
Last edited:
Wow finally another design with the 6C41! Nice...How do you like the sound?
The hum is most likely a grounding problem.
Looking at the size of the caps/chokes etc, you have used there should be very little psu ripple?
The fizz is probably because of the 6C45pi...You could try larger grids stoppers and/or...ferrite beads and ceramic caps on the heaters etc...to quiten it down...
PS..beautiful amp!
Regards,
Bas
The hum is most likely a grounding problem.
Looking at the size of the caps/chokes etc, you have used there should be very little psu ripple?
The fizz is probably because of the 6C45pi...You could try larger grids stoppers and/or...ferrite beads and ceramic caps on the heaters etc...to quiten it down...
PS..beautiful amp!
Regards,
Bas
Hi,
My thoughts as well.
If it is build exactly as shown on the drawing then the entire amp is floating with respect to ground.
From the picture it's hard to tell whether or not the WBT RCA input grounds are connected to the topplate of the chassis (or other ground for that matter).
Is it necessary to tie the heater of the 6C41 to its cathode?
According to the Russian datasheet and allowing for the fact that my reading of anything cyrillic is basic at best, I think heater to cathode insulation is +/- 300V which should be more than ample giving the B+ used.
The woodwork reminds me of the LINN LP12 turntable.
Well done.
Cheers,😉
My thoughts as well.
If it is build exactly as shown on the drawing then the entire amp is floating with respect to ground.
From the picture it's hard to tell whether or not the WBT RCA input grounds are connected to the topplate of the chassis (or other ground for that matter).
Is it necessary to tie the heater of the 6C41 to its cathode?
According to the Russian datasheet and allowing for the fact that my reading of anything cyrillic is basic at best, I think heater to cathode insulation is +/- 300V which should be more than ample giving the B+ used.
The woodwork reminds me of the LINN LP12 turntable.
Well done.
Cheers,😉
Hi
Thanks for replying.
The ground is attached to topplate from 120uF. The RCA ground is attached to 120uF by a 2mm diameter wire.
But which is the best way to ground?
And yes, it is not necessary to bias filament of 6C41.....I'll detach it.
I'll report the new mods if I got time to do it.
cheers
Coffin
Thanks for replying.
The ground is attached to topplate from 120uF. The RCA ground is attached to 120uF by a 2mm diameter wire.
But which is the best way to ground?
And yes, it is not necessary to bias filament of 6C41.....I'll detach it.
I'll report the new mods if I got time to do it.
cheers
Coffin
An externally hosted image should be here but it was not working when we last tested it.
coffin said:
Is your filament just "floating"? If so, try grounding it out through a 10uF electrolytic of appropriate voltage. Just one side is OK. That cured one of my hiss/buzz/hum problems that biasing the filament did not 😉
Hi,
Unless you have a specific reason for having the input impedance at 10K, I'd suggest upping it to about 100K instead.
Cheers,😉
Unless you have a specific reason for having the input impedance at 10K, I'd suggest upping it to about 100K instead.
Cheers,😉
fdegrove said:
Hi
Thanks!
I did this because I read about the Cag of 6C45 is 11pF. If the input resistor is too large, Miller effect will affect the high frequency response.
Is 100K OK for this situation? Or the 11pF was wrong?
cheers
Coffin
Hi,
Cag for the 6C45-P is 1.1 pF not 11.
Naturally it's not just Cag and Rin that determine the frequency response but stray capacitance, stage gain and Cgk as well.
With an input resistance a little on the high side you'll also be able to control the 6C45-P's tendency towards oscillation (high Gm) much better and it will make driving the amp a much easier task especially for a tube preamp.
Cheers, 😉
Cag for the 6C45-P is 1.1 pF not 11.
Naturally it's not just Cag and Rin that determine the frequency response but stray capacitance, stage gain and Cgk as well.
With an input resistance a little on the high side you'll also be able to control the 6C45-P's tendency towards oscillation (high Gm) much better and it will make driving the amp a much easier task especially for a tube preamp.
Cheers, 😉
....1.1pF......Thanks!
Hi
Today I modified the amp. First change input resistor to 100K 😉 ; then link floating 6C41's filaments to ground with 22uF 😀 ; and adjust the grounding.
But the major mod was change PSU of 6C41 from LCRC to CLCRCRCRC.....
Because the choke fuzzed in choke-in style.....
After mods, although the choke is still vibrating, but the fuzz was gone.
The result is not bad. Hum and fizz from speaker are hardly hear.
I'll take this amp to friend, ask him to test the specs for me.
The sound is really good......
Modified schema
Some pics
BTW, why is the choke in LC style fuzz? How to eliminate it?
cheers
Coffin
Today I modified the amp. First change input resistor to 100K 😉 ; then link floating 6C41's filaments to ground with 22uF 😀 ; and adjust the grounding.
But the major mod was change PSU of 6C41 from LCRC to CLCRCRCRC.....
Because the choke fuzzed in choke-in style.....
After mods, although the choke is still vibrating, but the fuzz was gone.
The result is not bad. Hum and fizz from speaker are hardly hear.
I'll take this amp to friend, ask him to test the specs for me.
The sound is really good......
Modified schema
An externally hosted image should be here but it was not working when we last tested it.
Some pics
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
BTW, why is the choke in LC style fuzz? How to eliminate it?
cheers
Coffin
Hi Coffin,
If by "fuzzing" you mean the mechanical buzzing of the choke, there is a way to eliminate or, at least, reduce it.
For a CLC filter, you can use the, what is called, "tuned choke" circuit. That means that you put a capacitor in parallel with the choke. This LC circuit forms a resonator, and you try to tune the resonator at the ripple frequency, adjusting the cap accordingly. This circuit also reduces ripple of PS significantly. For a more detailed description, have a look here:
Tuned choke
Now, for a choke input LC filter, you must use a snubber circuit, which is described by Morgan Jones in his book. This consists of two caps, one in front and one after the choke to ground. Morgan Jones suggests these caps beeing 220 nF. I have used this in a preamps' LC PSU which was buzzing like crazy and now is totally quiet.
Note that for the CLC filter the caps can be low voltage, since they are across the voltage drop of the choke, but, for the LC filter, they should be high voltage.
You can also try a grid stopper (try 1K) on the grid of output tube.
Regards,
Evangelos
If by "fuzzing" you mean the mechanical buzzing of the choke, there is a way to eliminate or, at least, reduce it.
For a CLC filter, you can use the, what is called, "tuned choke" circuit. That means that you put a capacitor in parallel with the choke. This LC circuit forms a resonator, and you try to tune the resonator at the ripple frequency, adjusting the cap accordingly. This circuit also reduces ripple of PS significantly. For a more detailed description, have a look here:
Tuned choke
Now, for a choke input LC filter, you must use a snubber circuit, which is described by Morgan Jones in his book. This consists of two caps, one in front and one after the choke to ground. Morgan Jones suggests these caps beeing 220 nF. I have used this in a preamps' LC PSU which was buzzing like crazy and now is totally quiet.
Note that for the CLC filter the caps can be low voltage, since they are across the voltage drop of the choke, but, for the LC filter, they should be high voltage.
You can also try a grid stopper (try 1K) on the grid of output tube.
Regards,
Evangelos
Hi
Thanks your thoughtful advice.
I'll read them.
A pic in return:
coffin
Thanks your thoughtful advice.
I'll read them.
A pic in return:
An externally hosted image should be here but it was not working when we last tested it.
coffin
Hi
Here's the big one....
Coffin
Here's the big one....
An externally hosted image should be here but it was not working when we last tested it.
Coffin
Thank you! 😀
May we have permission to share wallpaper based on this image with our tube friends on Usenet? Crediting you of course for the image 🙂
May we have permission to share wallpaper based on this image with our tube friends on Usenet? Crediting you of course for the image 🙂
Hi
A friend of mine had tested it.
Max output : 6W
Frequency Response at 1W output:
20hz¡G2.75v / -0.31db
50hz¡G2.82v
100hz¡G2.83
500hz¡G2.85v
1khz¡G2.85v
5khz¡G2.85v
10khz¡G2.84v
15khz¡G2.81v
20khz¡G2.78v / -0.22db
I think it is pretty good.
But there's another phenomenon at 20KHz:
It seems there's a modulation at the top of the square wave. like 40KHz around.
Can someone give an idea?
Thanks!
Coffin
A friend of mine had tested it.
Max output : 6W
Frequency Response at 1W output:
20hz¡G2.75v / -0.31db
50hz¡G2.82v
100hz¡G2.83
500hz¡G2.85v
1khz¡G2.85v
5khz¡G2.85v
10khz¡G2.84v
15khz¡G2.81v
20khz¡G2.78v / -0.22db
I think it is pretty good.
But there's another phenomenon at 20KHz:
An externally hosted image should be here but it was not working when we last tested it.
It seems there's a modulation at the top of the square wave. like 40KHz around.
Can someone give an idea?
Thanks!
Coffin
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