Preamp with 200 VDC and 6,3 VDC

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pepit23

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Hi everybody!
I have a 200VDC and 6,3 VDC power supply and I am looking for a DIY PCB preamp that could use this supply.
Any suggestions?
Thank U.
Flavien
 

Winston OBoogie

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Ha!
Not seen that one before. Looks good. Very similar scheme for gain adjusting as the NWDR V41 and V76 amplifiers. Switchable output mode too.
Nice one Jonte if you see this.

Thanks Solkatten.
 

solkatten

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Ha!
Not seen that one before. Looks good. Very similar scheme for gain adjusting as the NWDR V41 and V76 amplifiers. Switchable output mode too.
Nice one Jonte if you see this.

Thanks Solkatten.
Yep I haven´t build the hole amp, just the output stage combined with another front end and eq. It sounds great! theres a build tread here on groupdiy...
 
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MaxDM

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That's more current than usual for a first stage, isn't it? Might sound a little harsh?
 

solkatten

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That's more current than usual for a first stage, isn't it? Might sound a little harsh?
There are at least 2 treads in this forum in Jonte Knifs preamp. He is also the designer of some of the best mastering eq compressor and preamps money can but. Check out knifaudio.com
 

MaxDM

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There was a period when I used to use very high voltages and the highest possible current in preamp and line amps, and there is some advantage to that. Transients are very quick, the sound is hard, not puffy, and in-your-face. There is a bit of a downside, when it comes to the first stages, though, and I am not sure if it was due to added distortion, or simply a question of aesthetics.

I'm sure it's a great preamp. My question was just to get some subjective opinons. I can see the designer knows what he is doing.
 

Winston OBoogie

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That's more current than usual for a first stage, isn't it? Might sound a little harsh?
It's all relative really. I'm only eyeballing the ECC88 curves on a laptop here, but it looks to be about 2.3mA in that first stage. That's certainly higher than the sub 1mA in the EF804S' anode in a V76. But not particularly high at all for an ECC88.

Where might you have placed it so it sounded less harsh Max?

😉
 
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solkatten

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There was a period when I used to use very high voltages and the highest possible current in preamp and line amps, and there is some advantage to that. Transients are very quick, the sound is hard, not puffy, and in-your-face. There is a bit of a downside, when it comes to the first stages, though, and I am not sure if it was due to added distortion, or simply a question of aesthetics.

I'm sure it's a great preamp. My question was just to get some subjective opinons. I can see the designer knows what he is doing.
Hi I didnt build the front just the E81L output so I cant really comment on the subjective side of things👍

I think the design idea was a clean front end and that all the colouration happened in the line stage so you are probably on target
 
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MaxDM

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It's all relative really. I'm only eyeballing the ECC88 curves on a laptop here, but it looks to be about 2.3mA in that first stage. That's certainly higher than the sub 1mA in the EF804S' anode in a V76. But not particularly high at all for an ECC88.

Where might you have placed it so it sounded less harsh Max?

😉

The second stage caught my eye more than the first. The 50K pot, I'm sure works fine, but what are the advantages?

I've just found that sometimes, tubes can clean up a little bit, with more conservative currents in the voltage amplification stages, even though they become a bit slower-sounding and softer on transients, if you go too far.

But not having heard this particular circuit I was curious to hear people's opinions.

In the end it's a balancing act, and subject to taste
 

solkatten

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I think he liked to keep the impedance low due to noise. The line stage has varying input impedance due to switchable local feedback and that starts to interact with the high pass filter, if not buffered. I built mine with a 100k pot and a 100k buffer resistor in the grid circiut of the line stage. It worked fine, that put the max grid leak value in the 200 K range.
 
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MaxDM

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I think he liked to keep the impedance low due to noise. The line stage has varying input impedance due to switchable local feedback and that starts to interact with the high pass filter, if not buffered. I built mine with a 100k pot and a 100k buffer resistor in the grid circiut of the line stage. It worked fine, that put the max grid leak value in the 200 K range.

what kind of noise? hum?
 

solkatten

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what kind of noise? hum?
High enough not cause a rise in distortion and low enough not to exceed grid leak value and excess noise... I guess... The noise issue isnt a big one....
 
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