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The JC2-HPA Headphone Amplifier
The JC2-HPA Headphone Amplifier
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Old 25th May 2020, 07:10 AM   #141
Zung is offline Zung  Switzerland
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Good find!
These days, China is a bit of a gamble: I ordered these on Mar 8, and still get "In transit" after nearly 3 months. I do receive all the stuff I don't need though.
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Old 25th May 2020, 07:22 PM   #142
metaphile is offline metaphile  United States
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Default List of cap substitutions from Mouser

Thanks Zung and Patrick for your responses.

Quote:
Regarding the sound of passive vs active PSU, I did an experiment about 40 years ago[...]
This is really interesting stuff, I appreciate you sharing your experience. I might experiment with modifying the PSU down the line. This will be my first headphone amp so I will have nothing to compare it to initially.

Per Zung's advice, I'm going to replace all the capacitors that came with the kit. I'm operating under one self-imposed constraint: I want to stick to in-stock parts available from Mouser (I know: Digikey has some stuff that Mouser doesn't, I'm just loyal to Mouser) so as to not wait an eternity for shipping from China.

So, I've come up with a detailed substitution list w/ Mouser links that I've shared as a Google doc here. Hopefully some others who want to get all their caps in one place might find it useful.

As for the low-value caps, here's what I've settled on:
  • 22pF ceramics - replace with 22pF silver mica minis from CDE
  • 100pF ceramics - replace with 100pF silver mica minis from CDE (a cheaper alternative that would still *barely* fit the board: WIMA FKP2 Polypropylene)
  • .1uF blue box-type bypass caps (pic attached, probably polyester given the form factor) - there's not much space on the board for these, so I plan to replace the supplied ones with with .1uF PPS caps from Kemet (from what I'm reading, Polyphenylene Sulfide seems a better alternative to Polyester without the massive size of Polypropylene)

Let me know if you have any feedback on the above. Hopefully the list will be helpful to others building the same board under similar constraints (capacitor footprints, budget, shipping lead time).

Thanks again!
Attached Images
File Type: jpg Blue-box-caps-markings.jpg (776.5 KB, 125 views)
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Old 25th May 2020, 07:36 PM   #143
EUVL is offline EUVL  Europe
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Better than mica, IMHO :
https://www.surplussales.com/capacit...ly-Unelco.html

And for PPS, I use :
ECH-U1H104GX9 Panasonic | Mouser Europe


Patrick
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Old 25th May 2020, 07:58 PM   #144
metaphile is offline metaphile  United States
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Thanks for the suggestion -- that's a cool supplier. Now I'm paralyzed with indecision, when I should probably stop obsessing over what amounts to 6 caps in a project I'm doing for fun.

I'm reading that though polystyrene has advantages over silver mica, and those caps you linked are certainly much cheaper than the micas, they can sometimes melt in high-temperature applications. Something to be concerned with when soldering these types of caps? (I've never built with either type before, only polyester film and electrolytics).
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Old 25th May 2020, 09:58 PM   #145
Zung is offline Zung  Switzerland
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Mica is basically a rock: it withstands 900C/1,650F and doesn't fear anything.

Polystyrene (PS) is at the opposite end of the spectrum and melts at 100C. I did my share of killing of the older types like those linked by EUVL, not by soldering, but by accidentally touching the body with the soldering iron. I like the Philips PS for phono EQ and filtering; they are 1% and housed in a metal tube, and I've never managed to kill any of those so far. They are discontinued but still available off eBay at reasonable price. They have iron leads (evil), and of course they're overkill for compensation.

I wouldn't worry too much about soldering in general, the through hole types are actually very kind to the components. You should see the SMD soldering for a scare; lots of these on Youtube.
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Old 25th May 2020, 10:46 PM   #146
carlmart is offline carlmart  Brazil
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What about COG ceramics?

I have received recommendations about them from audio serious people. Probably not as good as polystyrenes (never had any problem soldering them, that must be done quick), but apparently comparable to polyprops.

They come in wire ended versions, are cheap, and probably worth a try from Mouse.

And certainly do keep away from iron leads: they are bad for audio.
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Old 26th May 2020, 12:49 AM   #147
metaphile is offline metaphile  United States
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Quote:
They come in wire ended versions, are cheap, and probably worth a try from Mouse.
Boa noite, carlmart. Appreciate the suggestion.

Vishay C0G's are dramatically cheaper than the small CDE Silver Micas I found on Mouser. $1.14 for the 6 C0G ceramics (example) versus nearly $19 for the 6 Silver Mica's (more than I paid for the kit if you don't include shipping!)

I found a few threads in which folks suggest them as a good choice for compensation, though opinions vary.

No disrespect to Zung and Patrick's input here, but the lower price and convenience of not needing to put in a separate order w/ shipping is winning me over to the C0G/NP0 camp.
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Old 26th May 2020, 02:35 AM   #148
metaphile is offline metaphile  United States
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I apologize for turning this into a capacitor conversation. I promise to update the thread with more useful information and photos as I proceed with the build itself.

I just discovered this post from John Curl over in the JC-2 clone thread where Zung originally started posting about this HPA.

Quote:
You should replace C2 and any other parts like it with mica or polystyrene. This is important.
So, I shall pay the piper (USPS in this case) and go with the polystyrenes.

Meanwhile, I was looking through my Aliexpress receipts and noticed I did purchase a dual pre-regulator board at the same time as the kit, transformer, and enclosure. So I may indeed follow the recommended PSU mods whenever it arrives. I believe it's still in China, or stuck in customs, or somewhere over the ocean -- as is the enclosure itself.
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Old 26th May 2020, 04:50 AM   #149
EUVL is offline EUVL  Europe
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If you would be so kind, I would also like some caps from that place.
If you would purchase for me, and then post to our store in Hong Kong, I offer to pay for USPS, including yours.

Shoot me a PM.


Patrick
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Old 26th May 2020, 10:06 AM   #150
carlmart is offline carlmart  Brazil
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Metaphile,

As all things in audio, better to listen check things first. Particularly on capacitors, and particularly when they are placed in critical places.

In my case I have little doubts: if available I would always go with polystyrenes. It's a pity they were never made higher than 100n, but I did use them in parallel to get to 500n for input cap. Best input cap I ever had. Completely invisible, no colour of any kind, as a cap should be.

Don't hold silver micas as high as many people do. But I must confess I never gave them a fair chance, as trying them was expensive.

Recently I was making a BOM for some projects I'm working on (a Luxman power amp clone and discrete RIAA clone), which went into stand by with the pandemic thing, and I think I will buy both polystyrenes and COGs. COGs have more available values, particularly in 2pF to 10pF for compensation parallels.

Now, another area you mention is the regulator for this HPA, and I wonder if you could read about the Denoisator option, that can be added to regulators you may already have, particularly 3X7 ones. Heard about them?

D-Noizator: a magic active noise canceller to retrofit & upgrade any 317-based V.Reg.

No need to read all 73 pages, I think reading the last 10 might be enough, if memory helps.

I did many LTSpice simulations with power supplies, some were uploaded to that topic, some I can provide if interested.

If your regulators are based on 3X7, LT1085 or fixed ones, like 78XX and 79XX, you should definitely give them a try. You can add small piggybacks with the mod parts, and people that tried them were very satisfied.

Sim results, particularly on Diego's mod of the mod, are spectacular in PSRR, impedance and noise, comparable or better to Jung/Didden superregulators. And with no expensive hard to find legit parts for, like FETs in Salas regulators.
 

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