[RustA]

To be more useful, here are several images of my amp:
 

 

 

 

 

 
Using DAC with 2.2vrms output and toslink (and no DSP like Replaygain), I get zero hum (electrical noise) with my Senns. On high impedance/gain mode, I hear low-level hiss on 75% and higher... That said, it's absolutely nothing to worry about since I never pass 20% of the overall volume. On low impedance/gain mode, there is no hum and no hiss at all.

 

[tomb]

Interesting that your new "hum shields" have no tops at all.  I suspected as much from early on.  It may simplify the potential improvement needed, if desired.  Again, it depends on the headphone.  I've reached nirvana with HF-1's and the pupDAC using my Torpedo with no mods at all.  It's funny, because my HF-2 seems a bit deficient in the highs by comparison.  I also have the SR-225's, but their highs seem exagerrated with somewhat deficient bass.  The HD600's with Cardas cables come close to the HF-1's, but are still a bit slow in the highs.  My only question is whether a pair of RS-1's are better than the HF-1's or more like the HF-2's.  I'm hoping the CanLanta meet will let me find out.

 
Just MHO, but I find the very old NOS 6J6's the best as opposed to the "Mysterians" Japanese tubes, but that's just a personal preference.  My Grados need some mellowing amongst all the detail and maybe that's what I'm attracted to.  I like the Sonotone 6J6W's, some of the JAN 6J6's and then the DuMont/RCA 5964's.  It's crazy that all these tubes are available in the tens of thousands for $2 and less.  Dsavitsk had a stroke of pure genius with creating an amp based on these tubes.

 
Anyway - also wanted to say that I like the black knob better, too.

  I think I'll make them all that way unless someone asks.  Nice photos!

 

[tintin220]

I'm about to put an order in and just get the long kit to save me the trouble of ordering parts from Mouser, etc. Does this kit contain the parts for the recommended mods (zener, etc.)?

 

[RustA]

Quote:

I'm about to put an order in and just get the long kit to save me the trouble of ordering parts from Mouser, etc. Does this kit contain the parts for the recommended mods (zener, etc.)?

 
Yes, order a full kit and you get EVERYTHING you need, including mods like zener or choke... That said, you have to tweak the amp yourself to get rid of hum that could possibly occur (see mine or heku's images for a basic guideline).

 

[tintin220]

Quote:

 
Yes, order a full kit and you get EVERYTHING you need, including mods like zener or choke... That said, you have to tweak the amp yourself to get rid of hum that could possibly occur (see mine or heku's images for a basic guideline).

 
Great, thanks for the info. I've always wanted to listen to a parafeed amp and see how it sings with my Grados, especially compared to the WA6. 

 

[heku]

I changed bias setting LEDs (D10, D11) to green ones (http://www.mouser.com/ds/2/239/_100_LTL2R3KGKNN-53107.pdf) and sound got better.
With standard red LEDs bias was 2.25V now it is 2.47V.

 

[tintin220]

Quote:

I changed bias setting LEDs (D10, D11) to green ones (http://www.mouser.com/ds/2/239/_100_LTL2R3KGKNN-53107.pdf) and sound got better.
With standard red LEDs bias was 2.25V now it is 2.47V.

 
Please define better. Does it measure differently? What are the differences as far as SQ in your opinion, as traits you may think are better might be worse to someone else's tastes? I'm still in the process of moving but once I get settled into my new apartment, I'll be ordering one of these kits to build. I sold my WA6, but I have one on loan from a friend that I can compare it to. Are there any other amps people want me to try for a comparison?

 

[dsavitsk]

The higher bias theoretically runs the tube in a more linear region. The problem with it is that it increases the plate voltage which limits headroom a bit. We used red since we thought it was a good tradeoff between sound quality and headroom. If you are not clipping with green and it sounds better, then by all means you should do it.

 

[heku]

I am not very good at describing sound, but I can hear new things from music and everything seems little bit clearer.
Plate voltage increased about 10V, it is now around 180 and 170V. I am using Russian 6N15P tubes and plate voltage with these tubes is higher than any other tube I have tried.

 

[RustA]

If anybody interested: http://www.head-fi.org/t/661655/fs-torpedo-parafeed-tubeamp-2013-edition-assembled-tweaks-matched-tubes-bargain-worldwide-shipping#post_9420373
 
As I said before in this thread, this amp is BEAUTIFUL in appearance and performance as well... That said, I had to find an amp suitable for powering both full-size headphones and IEMs/earbuds (got a killer deal on Concerto) and cannot afford having both at once.
 
I am able to switch to both 110v or 220v... More info in the listing.

 

[heku]

I wanted to try increasing CCS impedance, so I changed 2N5087 transistors to BC560C. I also changed bias transistors to BC560C.
And again sound got better.

 

[tomb]

Quote:

I wanted to try increasing CCS impedance, so I changed 2N5087 transistors to BC560C. I also changed bias transistors to BC560C.
And again sound got better.

Thank you for continuing to experiment, but I'm not sure I agree that changing 2N5087's to BC560C's are going to make any audible difference.  They should be fully equivalent in this instance.  Some more tube rolling would probably have a much greater effect than changing transistor type.  JMHO ...

 

[heku]

Diffence in sound was about same when I changed bias LEDs.
I measured transistors hFE using multimeter, for 2N5087's it was about 330 while BC560C's measured about 590.
For anyone doing this mod, BC560's have different pinout, so they go backwards on board compared to 2N5087's.
I used BC560C's just because I had those on hand, other transistor types might also work.

 

[tomb]

Quote:

Diffence in sound was about same when I changed bias LEDs.
I measured transistors hFE using multimeter, for 2N5087's it was about 330 while BC560C's measured about 590.
For anyone doing this mod, BC560's have different pinout, so they go backwards on board compared to 2N5087's.
I used BC560C's just because I had those on hand, other transistor types might also work.

No offense, but I've had 2N5087's measure as high as 600-700, but I don't think that matters a bit the way they're connected.  Of course - other transistors will work - because it makes little difference.  Just color me skeptical on this one. 

 

[Punnisher]

Just put an order in for the kit and am excited to start building. I decided to go the DIY route for the value. Plus this amp will work with varying impedances which can't be said for many tube amplifiers.