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Old 6th October 2014, 03:35 PM   #1
koja is offline koja  Canada
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Default Aleph P is back!! (limited time offer)

i.) this is a limited time offer for ordering pcb by year end (say X-mass time? ).
ii.) one channel per board. the cost is tbd based on number of boards (absolutely no interest for me other than lowering the price for my 4 pieces).
iii.) reg PS section may be added to this board with a break away option, or ordered as a separate piece (we can decide together and I can add this section later).
iv.) I usually order from pcbcart in china and the board will be green with white silkscreen (other colors cost more).
p.s. all components are through hole but you still need solid soldering skills (i.e. you cannot solder with a log for the soldering tip).
vi.) this board has not been tested and you share the risk with me.

about AlephP v1.7: just a few reminders about the preamp: well, it is Papa's design. It can handle both unbalanced and balanced inputs and outputs independently (so also an ideal converter from one to the other). it runs on higher voltage (60V reg), which makes getting lower noise figures easier but it also makes the pre not a good choice for an integrated amp and sharing a PS at say +-24V. the max output of 20V is just a tiny bit short of driving a bal F4 or similar output stage to max power (assuming 23-25V rails). Papa also made an unusual choice to drive a stepped relay attenuator at preamp output (good for pre noise suppression but requires a few attenuator steps at pre input to prevent saturation with hot sources). the biggest drawback: Papa voiced AlephP with the big and expensive Wima MKP caps . those are rare pieces for which the manufacturer actually provided data as tested over the full audio spectrum. I guess Papa values his time and only works with the best of the components, (and I sort of share the same philosophy when it comes to my time ).

about PCB: I considered briefly the board which sold many pieces on this forum. well: a huge rail-to-gnd loop for picking up noise, but more importantly, Wimas do not fit there and I will be using those; (I can provide an alternative footprint for you though); Moreover I wanted to use REED relays for the best contact quality possible on those input attenuators, and also for shorting neg signal to Gnd if used as unbalanced on either input or output. So I put together a two sided board, solid copper pour for ground (also EMC protection, kind of overkill for audio but that's DIY, right?). mind you: relays require a 5V PS (not provided). in my case the relay selections are made via a 4-pole DIP switch on the board, (or you can wire front mounted switches if that's what you want). the input attenuator relay is a common Hamlin HE700 series (DPST-NO); the other one is a relay i bought as surplus stock (Spartan 9000) and you may have to look up a replacement for the footprint. Of course, you can also give up either relay and just jump the contacts with a wire.

footnote: 5V PS and 1kOhm relay attenuator with remote control can be purchased from Mikkel (dantimax.dk). or any other source for that matter; you're on your own there.

here is the image of the board. please state your interest here. Thanks.
p.s. (I will also consider comments on the board, but you already know that every layout is about compromizes).
APv17_pcb_byKoja_v1.0.JPG

Last edited by koja; 6th October 2014 at 10:47 PM.
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Old 6th October 2014, 04:41 PM   #2
yoke is offline yoke  Croatia
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Hi Koja
I mide be interested for 6 channels, but have to see about heatsinks placement...
as I need six channels...I belive that heat mide be the problem in my case...
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Old 6th October 2014, 04:51 PM   #3
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I'm interested. Rough board pricing?

Do you have a source for the caps? Assuming 37.5 mm lead spacing Mouser US is showing enough on order to build a half dozen Aleph P1.7s, but half won't get caps until next September. Newark has 6.8 F in stock for a lot less than Mouser's 10 F. But again, not enough to build many. Perhaps enlarging the board to accept 2 input caps and 5 outputs will allow reaching the appropriate total value at lower cost/better availability.

EDIT: Good point Yoke, there should be some heat sinking with 60V rails unless we keep the current very low.
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Old 6th October 2014, 05:38 PM   #4
koja is offline koja  Canada
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four irf610s are back-to-back at 1/8" inch to share a 3mm thick heatsink (I usually just bend a copper strip in an "S" kind of shape over the low components around. I can post an example pic later today). the two 9610s are also to share a 2-2.5mm thick heatsink back to back. I do not expect much need with current sources at 20 and 30 mA.

about caps: i will be using the big Wimas (MKP4/250V P:37.5; body: 19x42x32H). I bought a bunch from Conrad when on business in Germany (well, I ran out of time at the airport and never got the european VAT back, so it did not end up a great deal after all, but that's a different story). i can provide one (or maybe two) alternative footprint(s) if a bunch agrees on a common cap. one should probably be the cheapo option of electrolityc SilmicII with a 100nf film bypass cap (kind of waisting board space there); and the other could be an other-than-Wima PP (with just a different pitch)?

p.s. btw I will make one stereo AlephP for sure, and the other I may be selling as a full kit (not quite sure yet).

p.s2. as for stacking the boards on top of each other: i make no special accomodation there. too many big components to play with mirror images and such, so they'll just have to add up fully in height.
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Old 6th October 2014, 05:56 PM   #5
koja is offline koja  Canada
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Default on pcb layout

btw the only thing I am not happy with is a little waisted space in the middle between large caps, so I may end up putting a smiley face logo there ?.

Maybe (and that's a ??) I could make it a bit more compact by putting all caps together and moving the middle section to the end of the board and sqeezing it together with the remaining four resistors and two screwholes; the relay footprint is cumbersome to work with, and the traces across the board will become long. after all, no layout will ever be perfect so there is always a question of effort versus returns. this admittedly would be better if a regulator section followed at the end of board and only for those who would not separate it, (mind you keeping PS there would make for one long board though).

btw the pcb screw holes are for number4 or M3 screws.

p.s. no idea of price before the final count: if of any consolation to you I paid $132 for two prototype boards for a digital fan control/soft start/spk protection a friend of mine helped me develop. but the price drops quickly when ordering more. $15-20/piece should be a reasonable target? whatever it will be, I will share the cost off the vendor's site with the group and just divide by piece count.

Last edited by koja; 6th October 2014 at 05:58 PM.
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Old 6th October 2014, 09:43 PM   #6
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Hi Koja,
I just wanted to say thank you for doing this first of all, and I would be interested in 4 boards. Thank you.
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Old 6th October 2014, 11:29 PM   #7
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Hello,

I`m also interested in probably 6-8 pcb`s, dependent on price..

Also if possible:

Caps: if room, please add trace for larger "boutique" caps
Jensen is 46x70mm long
Mundorf is 45x70mm long
Obligato is 30x75mm long etc

Relay:
Please post model no of relays, so we can be shure it is awailable, and not "end of life", or obsolite like Reed 9081C-12-10. Reed 9007-12-40 is "non stocked" at Mouser..and they come up when searching for Spartan 9000.... If you are doing the work, I am hoping your design can be buildt in the near future also..

It will be easier to sell boards if the parts are available from many sources.

I am also fan of gold or silver over lead/copper contacts in realay`s..

Thank you for doing the work with the pcb!
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Old 7th October 2014, 03:13 AM   #8
koja is offline koja  Canada
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Ok, it is already clear that it will not be possible to please everybody.

those boutique caps are huge and I cannot blow the whole pcb to that size. Sorry. (If more people are into those I may eventually consider doing something for you only, as a forum favor, but not right now). Wima is the base cap; if that one is not for you aim at something that can fit within those outlines, only pitch may be different.

I realize already that the Spartan relay may have to change for a more available one, (not good for me because I packed everything so tight on the pcb there ). otherwise, any Reed relay, (gold or not but with vacuum preventing oxidation) will garantee superb contact quality over a long time.

anyways, I promised Yoke to show the example of how I go about cooling the fets. here I show the pic of my aleph30 board where three 9610s share a copper strip. on AlephP board something along those lines will be possible as well. (maybe a "T" shape aluminum channel with some holes on top?) your imagination is the limit. be warned: if I like yours better I may copy you .
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File Type: jpg Aleph30_pic6_Koja.jpg (600.7 KB, 999 views)
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Old 7th October 2014, 04:37 AM   #9
Mr. dB is offline Mr. dB  United States
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Please sign me up for a pair.
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Old 7th October 2014, 11:40 AM   #10
Ginum is offline Ginum  Lithuania
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I'm interested in a stereo set.

Thanks.
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