The Nemesis 813 PP Amplifier
- izzy wizzy
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#91 Re: The Nemesis 813 PP Amplifier
Sorry chaps. This might have been less confusing if I'd posted a circuit. This is what I'm on about.
And combined this idea from MJ with this thread on Diyaudio https://www.diyaudio.com/forums/tubes-v ... -amps.html due to my history of oscilation with this amp. Just trying to get some ideas together in the pursuit of problems to come and maybe some that have arrived already.
Cheers,
Stephen
And combined this idea from MJ with this thread on Diyaudio https://www.diyaudio.com/forums/tubes-v ... -amps.html due to my history of oscilation with this amp. Just trying to get some ideas together in the pursuit of problems to come and maybe some that have arrived already.
Cheers,
Stephen
- pre65
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#92 Re: The Nemesis 813 PP Amplifier
I seem to remember our Nick had details of how to stop the mains transformer ringing. Might that help as well ?
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- Mike H
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#93 Re: The Nemesis 813 PP Amplifier
Oh right, OK.Nick wrote: ↑Mon Nov 19, 2018 2:15 pm Not sure its the type of snubber thats being discussed here Mike (or it wasn't). MJ started talking about a RC network across the choke as you describe, though with a C value that would put the resonance much higher than 100Hz. But he pointed out that the RC provides a path to HF past the choke so suggested a different network, a cap from the input of the choke to 0v and from the output of the choke to 0v, thus not providing a path for HF to bipass the choke.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
#94 Re: The Nemesis 813 PP Amplifier
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#95 Re: The Nemesis 813 PP Amplifier
I now have two channels going ... sort of. Two output stages going with a minor bit of buzz/hum. Can't make too much noise coz young people in bed.
Now to decide how to pursue this hum/buzz.
What would the panel suggest be a first step?
Here's what's built so far. Power supply as previous.
Cheers,
Stephen
Now to decide how to pursue this hum/buzz.
What would the panel suggest be a first step?
Here's what's built so far. Power supply as previous.
Cheers,
Stephen
#96 Re: The Nemesis 813 PP Amplifier
I assume the hum/buzz wasn't there for one channel?
Again, what does it look like?
It could be grounding, or it could be that the double current has caused more B+ ripple which is what you are hearing. Is it a choke or cap input supply?
Again, what does it look like?
It could be grounding, or it could be that the double current has caused more B+ ripple which is what you are hearing. Is it a choke or cap input supply?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- izzy wizzy
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#97 Re: The Nemesis 813 PP Amplifier
Both channels are the same-ish for buzz/hum
See page 1 of this thread for psu, pcb it's made on and rough idea of chassis stack. I can take more photos if needed.
Double current?? Choke input - see page 1
Thanks.
Cheers,
Stephen
#98 Re: The Nemesis 813 PP Amplifier
I think he means double the current will be pulled from the psu as it is now running 2 output stages instead of one and the higher current being pulled is causing a higher amount of ripple in the psu
- izzy wizzy
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#99 Re: The Nemesis 813 PP Amplifier
They're monoblocks.
I once built it as a stereo amp, the first one. It was about 1m square and so heavy, it was built in situ. It was monoblocks after that.
Cheers,
Stephen
#100 Re: The Nemesis 813 PP Amplifier
Must use 866's again some time, still got a heater transformer for four of them.
So if they are monoblock, the obvious thing to try is does the hum/buzz only happen when you turn the second on. If so, how far apart can they be and cause that to happen.
So if they are monoblock, the obvious thing to try is does the hum/buzz only happen when you turn the second on. If so, how far apart can they be and cause that to happen.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#101 Re: The Nemesis 813 PP Amplifier
Flippin' 'eckizzy wizzy wrote: ↑Tue Nov 20, 2018 10:58 am I once built it as a stereo amp, the first one. It was about 1m square and so heavy, it was built in situ.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- izzy wizzy
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#102 Re: The Nemesis 813 PP Amplifier
Those MVs above are GU20. Way bigger than 866 but because of that, the glow isn't as big. Don't know what I was thinking. 866s look nicer IMO but their heater transformers will be powering the 46s to begin with here. If it's successful, then I'll get dedicated transformers for the 46s and try and get the 866s fired up.
For one of the first times ever that I remember building these things, having two go at the same time results in the same amount of buzz/hum. In other words, no more than when one on. They are about 6ft apart. Previously it didn't matter how far apart they were for them to turn into a Theremin. Hopefully I'm on to something this time.
Keep the suggestions coming please.
Cheers,
Stephen
- izzy wizzy
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#103 Re: The Nemesis 813 PP Amplifier
Well exactly. They were made for the Acoustats and it made me think, if I need an amp like that to make them sing, then I got the wrong speakers so the amp was pulled apart, the speakers stored and I went on to Tannoys and haven't looked back. But if you've got the parts lying around ..... kinda like an itch that won't go away.Mike H wrote: ↑Tue Nov 20, 2018 1:01 pmFlippin' 'eckizzy wizzy wrote: ↑Tue Nov 20, 2018 10:58 am I once built it as a stereo amp, the first one. It was about 1m square and so heavy, it was built in situ.
Cheers,
Stephen
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#104 Re: The Nemesis 813 PP Amplifier
Yep.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
#105 Re: The Nemesis 813 PP Amplifier
Other buzzes seem to have pretty much gone. The hum now is very low 4.2mV true RMS so the scope says.
I now have two channels going ... sort of. Two output stages going with a minor bit of buzz/hum. Can't make too much noise coz young people in bed.
Now to decide how to pursue this hum/buzz.
Hopefully you can see our confusion.having two go at the same time results in the same amount of buzz/hum. In other words, no more than when one on.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.