B1 with Korg Triode

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#2,822
Zen Mod said:
both NuTube and PSMLS Buffer are having high Rin , so you can use standard selector - attenuator (LDR) arrangement , then feeding both Nu and PSMLS Buffer (practically inputs in parallel ) , then taking each output separately , using whichever you want whenever you want
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Thanks Zen, so my arrangement should work? I want to have one line with buffer before and after LDR available for some cases, and now I can do that Eg. Elma pz 2 Lorlin pz b
 
#2,824
bullitt5094 said:
Didn't realize there was another Pass DIY store. Thanks! I was hoping for less than $200 for the board and FETs though. Adding the PS and other components will push this up into the range of some decent finished Phono-Pre components. But no challenge/fun there, right?
Click to expand...

Keep in mind that the Pearl from Pass DIY is the second generation - Pearl 2.
Mine is the first, the original non-inverting pre.
Of course if buying from Pass DIy you'll also get the Fets which are hard to find.

My phono is built on a stripboard with SK369 instead of SK170 (half the number of Fets), and also an output buffer ala B1.

You don't really need a PCB, stripboard works just fine and will fit in a chassis with B1Korg, but do you have the Fets is the main question?

Cheers
 
#2,826
6L6 said:
The first batch is being shipped before they close. Which means the second batch will be available after they return and make them.

If you want one and they are available in the store, don’t delay, since there’s going to be a wait, and the first batch isn’t that big.
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Is this the chassis?

chassisfront.jpg
 
#2,831
Just finished up the cap replacement in my B1 Korg. I used the film caps that Claude suggested (thank you). While I was at it, I added in the rubber vibration isolation mounts that I picked up on ebay (these are linked in one of my posts above). The rubber mounts reduced the magnitude of Nutube ringing by 15-20dB when I adjust the stepped attenuator. Not gone, but clearly better.

It took a little while to figure out how to arrange the caps so I'd still have access to the trim pots and the Nutube. I used hot glue to hold them in place on the board - it seems to have worked well. Just put it all back together, so I haven't had time to sit and listen yet.

With the new cap values (0.22uF, 1.0uF, and 3.3uF instead of 10uF all around) the -3dB points are about 10Hz and about 65kHz. At 20Hz, response is down just a small fraction of a dB. Since my main speakers (FHLXs) don't really "do" the 20Hz thing, this is a difference I'll never notice.

Looking forward to some time to listen in the coming days!
 

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#2,832
While I was playing around, I also adjusted each channel for a combination of highest H2 with lowest H3. I was surprised by the difference in T7/T8 voltage settings to make this happen. I ended up with 9.8v on the right channel (pretty close to the recommended 9.5v), but it took 10.2v on the left channel to come closest to matching it. With a 1kHz signal and an overall output level of about -10dB (trying not to overwhelm the sound card) I was able to directly match H2 magnitude (at -47dB), but the H3 levels were still rather different. H3 measured -78dB in the left channel and about -97dB in the right channel. I was unable to get the left channel H3 any lower. Guess the individual tubes have a bit of variation to them...
 
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#2,834
It's taken me forever to get this far now I have to ask a dumb question. The FETS that Nelson graciously sent out with the Christmas batch (where does the time go!) came in a bag all together, but I have read that Q1 & Q2 are not interchangeable.



How do I know which FET to put where?
 
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