Calling all Pocket Amp owners - is there anyone in the Los Angeles, California area with a built and working amp? I received a request by PM from a member for a test-listen before ordering board and parts to build. I know this is unusual, as most DIY is about building and then listening. If you are in LA and willing to meet with another member please send me a PM.
Thanks,
X
Thanks,
X
Order here - one stop shopping. I would get the 2200uF 16v Nichicons though instead of the 1000uF rail caps.
Invalid Request
Oops, had it backwards.
In fact, I realized 33R is exactly what I used on my board too. I ended up with a nice 55mA bias. I should say, I was considering 47R based on this earlier post:Will it get a lot warmer with these resistor swaps?
67mA bias is noticeably warmer but not uncomfortable. For me, 50mA bias is barely warm, whereas 67mA feels like a hot-blooded Class A - no doubts about it. Battery life falls pretty fast though - but if I can get 3 hrs, I am good as my commute is sometimes 2hrs. With 67mA I get about 3.5hrs on EBL 600mAhr batteries.
Haha everything is already in my RS components cart - just have to check out on it. (aside from the switchcraft and some silmics / muses, which are coming from eBay)
Will 16V be okay for the rail caps? 9 + 9 = 18V? or am I missing something here? (I've got 25V 2200uF caps in my cart at the moment)
Are there any test points to measure the bias current? Or what is the suggested method to measure this?
Will 16V be okay for the rail caps? 9 + 9 = 18V? or am I missing something here? (I've got 25V 2200uF caps in my cart at the moment)
Are there any test points to measure the bias current? Or what is the suggested method to measure this?
The rechargeable Li-ions are 16.4v at full charge. Drops below 16v within 5min of use and finding a 25v 2200uF that fits there is tough. None of the major brands (Panasonic, Nichicon, Rubycon, Elna, etc) makes a 2200uF 25v that is 13mm Dia x 21mm long max dimension. I have found some Chinese ChongX brand on Aliexpress that's the right rating and size. I measured them and they actually are decent value and ESR. Link to them a few pages back. The 16v works fine unless you want to use 9v alkalines. But even 16v caps can be pushed a few volts over - they won't blow up.
Yes! You found it then.
http://www.mouser.com/Search/Produc...22virtualkey66720000virtualkey667-EEU-HD1E222
Thanks!
http://www.mouser.com/Search/Produc...22virtualkey66720000virtualkey667-EEU-HD1E222
Thanks!
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Sweet. Now I maybe I don't have to wait for weeks for the Alixpress caps!
Anybody have any experience with the Panasonic HD series? I have seen folks recommend the FR, FM, FC for power rails, but to use one of those, we'd have to settle for this FR at 1500uF. If low ESR is desired, maybe the trade-off would be worthwhile?
While we're on this topic, I have a wider question: is it even possible to hear sonic differences between different makes/models of identically rated power rail capacitors--which are not in the signal path? X, I know you've said you are not a capacitor snob, lol. But I've read some threads where folks obsess over PSU cap choices for their amps.
I even came across an old Audiocircle thread where a guy claimed that ceramic X7R caps sounded "harsh" as PSU bypasses, recanting his previous recommendation of X7R in an even older thread. (Coincidentally, AKSA was part of both discussions
). I'm not sure if substituting tiny film caps would possible or beneficial whatsoever, but I'd try it if so. Speaking of which...what are all these extra holes in the Pocket Class A PCB, over by the power rails, intended for?
Those are vias to connect the copper planes on both sides to serve as a heatsink radiator for the MOSFET.
You might heat effect of caps on power rails if it does not absorb diode switching transients properly. No reason why x7r can't do that. C0G/NP0 should be used if ceramics need to be in audio path.
Sweet. Now I maybe I don't have to wait for weeks for the Alixpress caps!
Anybody have any experience with the Panasonic HD series? I have seen folks recommend the FR, FM, FC for power rails, but to use one of those, we'd have to settle for this FR at 1500uF. If low ESR is desired, maybe the trade-off would be worthwhile?
While we're on this topic, I have a wider question: is it even possible to hear sonic differences between different makes/models of identically rated power rail capacitors--which are not in the signal path? X, I know you've said you are not a capacitor snob, lol. But I've read some threads where folks obsess over PSU cap choices for their amps.
I even came across an old Audiocircle thread where a guy claimed that ceramic X7R caps sounded "harsh" as PSU bypasses, recanting his previous recommendation of X7R in an even older thread. (Coincidentally, AKSA was part of both discussions
I looked at those old threads - interesting talk about encasing elco (shorthand for you know what as I am lazy) caps in beeswax to reduce mechanical resonance. There was a comment about "oil cans" sounding amazing - which I take to mean oil-filled film caps like industrial motor run caps. I have used them in crossovers and thought sound was very nice. Have not tried on amp coupling yet. They are huge though. Not expensive. Here are 50uF ones that I got. One takeaway rule of thumb is that film bypass should be about 1/100th value of elco. Don't know how true this is as it would mean 4.7uF needed for 470uF main elco. But didn't you say you tried large bypass here and it did not seem to matter?
Number 1 best seller on Amazon (I assume not for audio use):
https://www.amazon.com/TEMCo-Motor-Run-Capacitor-RC0015/dp/B00FBRWUP0
I should try someday.
Btw, my Etsy shop (XRKAudio) now has PCBs, SMT pre-soldered PCBs, matched FETs, parts kits for the BOM, and several varieties of fully built amps. In case anyone likes to order from that site. It's quite convenient shopping wise.
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was thinking along the lines of KAs with the bypass on the SMD side as you mentioned; either 2200uf 16v / 1000+470 / 1000 only.
1000 or 2200 probably easiest space wise rather than 1000+470; 2200 is probably overkill though, since i don't really have anything under 20 ohm.....
Largest output bypass I have tried is still 2.2uF. I heard a difference but I want to sample more options before I solder one in.
I have a Mouser cart full of caps that I am trying to pare down a lot before I buy (over $100 worth at the moment lol). It includes some Kemet SMR (PPS), Vishay MKT and even some sub-1uF MKP.. I definitely Am including the 4.7uF WIMA MKS as well.
I'll try everything by itself, but I am most interested in a "double bypass" as you have done. I would probably use two films...like a 2.2/3.3/4.7uF PET/PPS on SMT side and and then a .33/.47uF PP mounted in the original bypass spot.
I plan to even try a tiny bypass on the SMT side of the input cap. Like a .033uF MKP.
After reading Bateman's work I am really intrigued by PPS. One of my experiments will be using them for both input cap and output bypass. It is hard to find accounts of people who have used PPS in audio circuits, but on first glance they appear to offer near-PP linearity at near-PET compactness.
Oh, and I found some Kemet c0g to try for the power rail bypass in my second amp. I'll probably not hear a difference, but I'll have the satisfaction of knowing I went the extra mile, and they cost nothing, even less than the X7R, oddly.