Attached is what I got from their online portal, assuming a PCB dimension of 60mm x 30mm.
Be aware that shipping cost is linked to the size (weight) of the PCB, cost would be USD15 for ten 100mm x 100mm PCBs.
Attachments
The current that passes through the jFET depends on the Vgs applied.
If you have different devices, then each will pass a different current.
With the very high spread of parameters of jFETs (all FETs) you could end up with a few of the ten passing most of the current.
Without any degeneration resistance you can't check how much current is passing.
The only clue would be to measure individual jFET case temperatures, after you have built and biased.
Far better to select similar Idss and then select from those for similar Vgs at the chosen operating current.
And it would help a lot to adopt some degeneration resistance for each jFET.
Wow that is cheap. I figured that a group buy would be an even better deal, and I like the idea of somebody more knowledgeable than myself passing along the circuit design to the printer, since I know zilch about the process or the specs involved with ordering. Is it pretty foolproof?
I also like the idea of the group buy because it seems likely that some of us would end up building our amps more or less simultaneously, hopefully sharing tips and listening impressions, etc.
Hopefully this will get some attention!
New DIY Altoids Tin Amp - The Class A "Wintergreen Handwarmer" by xrk971
New DIY Altoids Tin Amp - The Class A "Wintergreen Handwarmer" by xrk971
StellarElephant:
I have been listening to the Pocket Class A for an extended period now and have compared it to some world class head amps designed on this forum. I am happy to report that my listening impressions have not changed regarding how good it sounds. Being battery powered, it is utterly quiet and able to resolve some amazing low level detail when listening from a good DAC. My latest measuremts show an absolute flat noise floor devoid of 60Hz hum at -125dB and a dynamic range of 92dB - well matched to CD quality sound. I am using 47uF output caps at present so at 20Hz there is about a -2dB falloff but I plan on upgrading to a 390uF oscon output cap in the future. This should take the -3dB point to about 5Hz and give this amp the bass extension to meet any audio need. The one area where my "big amps" such as the Salas DCG3 and BF862 preamp with DAO buffer amp have an advantage is bass "slam" due to the fact that they have huge 18v to 20v dual rail multi-ampere power supplies. But for the rest of the music - this little amp surprises me all the time with how great it sounds. Natural, musical, easy on the ears, lively, not sterile, resolving, quiet when needed, expressive, accurate (due to flat response), most of all - enjoyable for hours on end. It beats all my other amps on noise. It is the quietest amp of all with only two transistors in a tight layout that doesn't pick up noise, and ultra quiet batteries to provide juice.
I have double checked the SMT version made by BDHM and it looks good. We can proceed to a GB now for the SMT version. Perhaps BDHM can give us a status on the through hole version?
I have been listening to the Pocket Class A for an extended period now and have compared it to some world class head amps designed on this forum. I am happy to report that my listening impressions have not changed regarding how good it sounds. Being battery powered, it is utterly quiet and able to resolve some amazing low level detail when listening from a good DAC. My latest measuremts show an absolute flat noise floor devoid of 60Hz hum at -125dB and a dynamic range of 92dB - well matched to CD quality sound. I am using 47uF output caps at present so at 20Hz there is about a -2dB falloff but I plan on upgrading to a 390uF oscon output cap in the future. This should take the -3dB point to about 5Hz and give this amp the bass extension to meet any audio need. The one area where my "big amps" such as the Salas DCG3 and BF862 preamp with DAO buffer amp have an advantage is bass "slam" due to the fact that they have huge 18v to 20v dual rail multi-ampere power supplies. But for the rest of the music - this little amp surprises me all the time with how great it sounds. Natural, musical, easy on the ears, lively, not sterile, resolving, quiet when needed, expressive, accurate (due to flat response), most of all - enjoyable for hours on end. It beats all my other amps on noise. It is the quietest amp of all with only two transistors in a tight layout that doesn't pick up noise, and ultra quiet batteries to provide juice.
I have double checked the SMT version made by BDHM and it looks good. We can proceed to a GB now for the SMT version. Perhaps BDHM can give us a status on the through hole version?
Pocket Class A Headamp GB
Ok folks, for the Pocket Class A Headamp GB, if you are interested, please quote this post and add your name. When I get at least 5 people with 2 units ea or 10 people with 1 unit ea, etc. (minimum 10 boards), I will place the order for the boards.
My pricing is the usual to cover shipping and nominal costs of fab and hassle of conducting a GB. Put it this way, I am not getting rich off of it
$17 for 1 board outside of continental US (CONUS). $12 for one board within CONUS.
If you want two boards, add $5 so $23 or $17 for two boards outside CONUS, and inside CONUS, respectively.
In case you are wondering what the BOM will cost, between $20 and $30 depending on your choice of components. Not including batteries or Altoids tin.
Would anyone be interested in a fully-built and tested unit, with same SE Class A topology and fits in an Altoids tin, but has added feature of turn-on delay protection relay, and uses top of the line components (WIMA, Panasonic OSCON, Alps, etc.)? Pricing is TBD based on interest.
Board will look like this:
It's SMT on one side and through hole on the other side. The SMT's are 0805 - easy to hand solder - don't worry about it.
Many thanks to BDHM fot the layout and Agdr for the baseline Altoids tin footprint and pot/jacks/LED Eagle files. Could not have gotten this far without you guys.
----
Pocket Class A GB Order List:
xrk971 - 2 boards
(add your name and number of boards here. Please use quote feature to grow list.)
Ok folks, for the Pocket Class A Headamp GB, if you are interested, please quote this post and add your name. When I get at least 5 people with 2 units ea or 10 people with 1 unit ea, etc. (minimum 10 boards), I will place the order for the boards.
My pricing is the usual to cover shipping and nominal costs of fab and hassle of conducting a GB. Put it this way, I am not getting rich off of it
$17 for 1 board outside of continental US (CONUS). $12 for one board within CONUS.
If you want two boards, add $5 so $23 or $17 for two boards outside CONUS, and inside CONUS, respectively.
In case you are wondering what the BOM will cost, between $20 and $30 depending on your choice of components. Not including batteries or Altoids tin.
Would anyone be interested in a fully-built and tested unit, with same SE Class A topology and fits in an Altoids tin, but has added feature of turn-on delay protection relay, and uses top of the line components (WIMA, Panasonic OSCON, Alps, etc.)? Pricing is TBD based on interest.
Board will look like this:
It's SMT on one side and through hole on the other side. The SMT's are 0805 - easy to hand solder - don't worry about it.
Many thanks to BDHM fot the layout and Agdr for the baseline Altoids tin footprint and pot/jacks/LED Eagle files. Could not have gotten this far without you guys.
----
Pocket Class A GB Order List:
xrk971 - 2 boards
(add your name and number of boards here. Please use quote feature to grow list.)
Attachments
Last edited:
Pretty much ready to go
Oooooh
The SMT caps are 1206, so even easier.The SMT's are 0805 - easy to hand solder - don't worry about it.
An absolute pleasure! And likewise, big thanks to Agdr.