NYD 2-channel two-bottle preamp finished. Have a look.

[Kingston]

It's been a long time coming, as this was my first bigger project. I had my share of beginners errors, and a few good mistakes here and there. It works like a charm now and is fully utilised in the studio already. I had to move the (now bulky) PSU out of the unit as it was causing far too much hum. There's phantom, -20dB pad, gain, DI input and 5-step output attenuator on both channels:

Hi-res version: http://www.michaelkingston.fi/files/NYD-two-bottle.jpg

Hi-res version: http://www.michaelkingston.fi/files/NYD-two-bottle-inside-highr.jpg

Noise at mingain, 200-ohm load. Balanced output to RME HDSP soundcard.

Noise at maxgain (+50-60dB or so, didn't measure it yet), 200-ohm load. Balanced output to RME HDSP soundcard.

Frequency response is damn near flat throughout the gain range, with 0.5dB deviations here and there from 30hz to 20khz. (tested with sine sweeps, pictures to come)

I'll post sound examples later, recorded with ribbons and such that this preamp seems to like quite a bit. Needless to say with jensen JT-110K-HPC (I scored them used for cheap) and OEP output trafos the sound is absolutely top notch. The +48V is from Gyraf G9 schematics (thanks Jacob).

This has been a tremendous learning experience. Thanks to everyone who helped me here in misc threads. If there's something to improve, it would be the layout. Right now the sound and noise performance are good enough for me - much better than I ever expected, but next time I know to start the whole layout design from "ground up".

What a great feeling that the best preamp I've heard was built by me. All the credit goes to the designer, of course, and this is where I tip my hat to Newyorkdave. What a great sound. :green:

 

[Kid Squid]

Looks the Buisiness,

Nice work fella :green:

Regards
Steve :thumb:

 

[mich]

looks good!
i did the one bottle version ,and this little thingy sounds great.
what oep did u use on the output?
and did u have a chance to compare it to unbalanced out?
thumbs up :thumb:

 

[Kingston]

[quote author="mich"]what oep did u use on the output?
and did u have a chance to compare it to unbalanced out?
thumbs up :thumb:[/quote]

It's the A262A2E flipped around at 4:1 ratio.

Yeah, I compared to unbalanced out side by side. Unbalanced was cleaner of course, with several dB more gain. The most obvious difference was in the high frequencies, where the OEP attenuated slightly, and there was a touch of what was possibly intermodulation distortion.

But the OEP simply *sounded* better, as the "color" it imparted was good. The difference was very subtle in the end, but the OEP works better than unbalanced. For 12e + 6e mu shield it's a steal. I will use OEPs for the inputs as well for the next project. They're great transformers.

Oh and I removed the R10 220k termination resistor, since the OEP sounded much better without it.

One oddity that I bumped into was that the sound seemed to change ever so slightly when using DC for the heaters. AC seemed to sound "more accurate". I don't quite know how to quantify/measure this, and wether it was my imagination. Anyone know what the reality of the situation might be?

 

[Freddy G]

Hey Kingston,
That's great!
Glad to see you've got it going. I'm in the middle of my NYDave 2 bottle build as well.
Did you find that dc for heaters produced less hum? I was planning on AC for the heaters, but I suppose that it has a lot to do with layout.
Great build!
Sound clips?
Freddy :sam:

 

[Kingston]

[quote author="Freddy G"]Did you find that dc for heaters produced less hum? I was planning on AC for the heaters, but I suppose that it has a lot to do with layout.
Great build!
Sound clips?
Freddy :sam:[/quote]

There is a 2-3dB less hum on my very mediocre star grounding layout using DC on the heaters. There's another trick you might want to try before resorting to the wasteful DC conversion. Have a look at newyorkdave's and paul stamlers discussion on drawing board, where the AC virtual center tap was biased to 30VDC (The MILA and noise specification threads). It seemed to produce similar results. I've yet to try it on this, but I might eventually test it.

sound clips to come sometime this week.