Walnut F1

Discussion in 'Portable Headphone Amps' started by Ivan TT, Aug 21, 2017.
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  1. Ivan TT
    The ones I've got are 1/2W metal film (the latter IS critical).
  2. silverfishla
    Was the buzz introduced during all th capacitor changes or was it always there? Does it have anything to do with the op-amps that are being used or is it inherent in the F1 from the get go?
  3. Ivan TT
    Was always there, but its not a buzz, but white noise.
    The reason is that F1's amp has gain of 11 (as far as I understand) as in "classic" CMOY design, and it wrecks havoc with gain staging when using with Z2's LO, bringing noise floor way too up and reducing the range of the volume pot.
    So reducing opamp's gain by adding resistors in parallel brings noise floor down, improves volume range and while there is still a bit of distortion at the top of volume pot travel when using "Power out", there's no noise or distortion when utilising buffered out and volume control range is more effective (and safe).
    After this mod my F1 has totally "black" background.
  4. Ivan TT
    Burson or muses predicament is easily solved by F1: why not have both? :L3000:

  5. activatorfly
    Cool thanks....mine are 0.6W metal film.
  6. silverfishla
    @Ivan TT Hey, I was wondering...where do you hear the "white noise"? Can you hear it with the volume pot turned all the way down on the F1? I just got the Walnut amp this afternoon, and I can't really hear it. I'm using a Zishan Z2 (with Muses02 in it, if that matters to you). It sounds pretty clean, even with the F1 volume turned all the way up (you know, sending all the power to the caps and all). I have a volume "thingy" in between the line out of the Zishan and the Walnut so that I can toggle the LO and turn up the F1. Here's a pic, so that I can prove I'm not BS'ing! hahaha! It's a volume thingy that actually came with a pair of Shure 500 series earphones. I thought it would work here, and it does without changing the SQ (as far as I can tell by AB'ing with and without it). F1.jpg
    dmz555 likes this.
  7. Ivan TT
    Yup, I used a similar one that came with UE TF10, 100Om attenuator.
    Great minds think the same :wink:
    To be honest I don't remember the configuration where that white noise was present, but I remember it disappearing after I reduced gain by soldering in those 12k resistors over opamp's terminals, and I think it was present when plugging into F1 power out (the middle one), but not line in (or was it other way around?). Try plugging your Z2 PO into F1's power out?
    I have muses02 in my F1, by the way :wink:
    Last edited: Sep 6, 2017
  8. silverfishla
    Interesting connection theories there! Hahaha! I think it's neat that you can plug in 3 headphones at the same time and have them all running at the same time from all the open jacks.
  9. DBaldock9
    I was really hoping the F1 would last longer than a week.

    Now, it makes a bit of a distorted sound - and goes quiet after a few seconds.

    Noticed that the Charging LED was going On & Off, with any movement of the USB cable...

    *** Intermission - While I check the Solder ***

    Found several of the through-hole solder joints that weren't done well including the ones for the USB connector. Also touched-up quite a few of the surface mount solder joints.

    The F1 Amp is working again now... :ksc75smile:
  10. TheoS53
    Just received my F1 (ordered from Penon). I was particularly interested in getting a bit more involved in the DIY side, so the F1 seemed like a decent place to start.

    However, when I opened the F1 up, I noticed that it does NOT have the large ELNA capacitors as advertised. Also, oddly enough it seems to have a 2000mah battery instead of a 1500. Anyone know why mine would be different? 20170917_130603.jpg 20170917_130607.jpg
  11. Ivan TT
    Better battery is nice and F1 would definitely benefit from it. What is the code on it, cannot quite see on the photo?
    As for the caps, it's not uncommon for those DIY devices to use substitutes due to (I assume) their supply chain. Aren't you replacing them anyway though? :wink:
  12. TheoS53
    Yeah, I do want to replace and play around. But part of the reason I got the F1 was because I said it had the Elna caps. I've seen them get good ratings for tube amps, so I was curious to try them out.

    I had a look on mouser but couldn't find the same ones that were originally used (220uf 10V)
    Last edited: Sep 17, 2017
  13. Robert Turnbull
    Quick question, does the mod on post #9 reduce the gain only on the 3.5 mm SE, or for both the 2.5 mm and the 3.5 mm?

    I quite like how powerful the 2.5mm is already... But i would like to cut the gain of the 3.5mm....
  14. activatorfly
    I agree....the balanced output is fine - doesn't need clipping....
  15. Ivan TT
    Yes, it reduces input gain of signals feeding thru Line In.
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