6V6 line preamp

[merlin el mago]

Salas & George every day that passes sounds better, it's addictive!!!

 

[Lingwendil]

Beautiful, glad it's working my man!

 

[merlin el mago]

Thanks Lingwendil.

 

[merlin el mago]

Salas for your knowing noDac outputs before the 4th LPF with 1kHz at 0dBfs 0.2750Vrms and after the LPF 0.2275Vrms

 

[merlin el mago]

1st pic left DSD128 & 2nd pic right DSD64 both 1kHz 0dBfs before the LPF.

I don't understad why both don't measures 1kHz also why different gain? I didn't set well the Brymen?

TIA

 

[Salas]

Does it up level with density maybe? Try different test files. Can it also replay PCM test files?

 

[merlin el mago]

Sorry noDac noPlay PCM files.

 

[merlin el mago]

The behaviour is really strange because when you listen DSD64 sounds louder vs listen DSD128.

I look for other way to generate 1kHz DSD files, do you know any?

 

[vgeorge]

6v6 is my best tube preamp Felipe and if you remember I also built a #26.

 

[Salas]

The behaviour is really strange because when you listen DSD64 sounds louder vs listen DSD128.

I look for other way to generate 1kHz DSD files, do you know any?

I don't know much about NoDAC or DSD generation but also see on oscilloscope instead of DMM only

 

[merlin el mago]

But can trust the gain not?

 

[Salas]

Not sure because the frequency readings change as well and that's weird. Oscilloscope will confirm or not. Sinewave peak to peak divided by 2.828 will be RMS.

 

[Lingwendil]

For a simple test I would use a cellphone or laptop audio output, and simply look up a 1khz test tone file or youtube video, then measure the voltage at the input and output. This will avoid the DAC and ensure the circuit is the thing being tested without extra troubleshooting.

I have an old 2014 era iPad I use with a test tone app specifically for this just in case theres an issue. That way if it fails I don't lose anything important due to circuit errors or high DC on inputs, etc.

 

[merlin el mago]

OK will take the scope measurements tomorrow, thanks Salas.

 

[Salas]

He has done that simple test with a function generator in the previous page. The 6V6 circuit's correct gain has been confirmed. Its the NoDAC output with test tone DSD files that he is researching.

 

[merlin el mago]

Yes Salas, the 6V6 is going on perfect & sound is top notch. I'm looking for the gain really necessary for the noDac.

 

[merlin el mago]

6v6 is my best tube preamp Felipe and if you remember I also built a #26.

What version do you use also NFB?

 

[merlin el mago]

Does it up level with density maybe? Try different test files. Can it also replay PCM test files?

Sorry, yes. Can be upsampled by software or by pcm2dsd (simple DSD modulator for DSC2). https://www.diyaudio.com/community/threads/simple-dsd-modulator-for-dsc2.370177/

 

[Lingwendil]

He has done that simple test with a function generator in the previous page. The 6V6 circuit's correct gain has been confirmed. Its the NoDAC output with test tone DSD files that he is researching.

Ah, ok.

I'm not familiar enough with the NoDac to comment further

 

[vgeorge]

What version do you use also NFB?

First built one without NFB, but gain was too much for my system. Then the cathode follower version, first choke loaded, then resistor loaded and kept the last one. I plan to modify it with the latest version with little NFB.