There will be a new BOM available (though not very different from the original one) and the link will be posted. Also everyone who will order the PCB will be provided with a link to valid documentation with schematics and project manual. This will happen after I have the new boards produced, which is supposed in the beginning of the next week.
I have also requested the mods to re-open my old thread in "Vendors bazar" dealing with PCB's sale. I can be also contacted through email through my web page.
Thanks to the mods, the thread dealing with Dispre 2 - JFET boards sales in the Vendors bazar section was re-opened.
Please use it for further communication regarding the project boards, or send me direct email. Thank you all.
Edited May 12, 2025
I would like to inform those who are interested in Dispre 2 - JFET PCBs, that they are again in production and available.
For technical information on the design please visit
https://pmacura.cz/dispre2-jfet_en.htm
and the project thread
https://www.diyaudio.com/community/threads/preamplifier-dispre-2-jfet.167033/latest
I would like to inform those who are interested in Dispre 2 - JFET PCBs, that they are again in production and available.
For technical information on the design please visit
https://pmacura.cz/dispre2-jfet_en.htm
and the project thread
https://www.diyaudio.com/community/threads/preamplifier-dispre-2-jfet.167033/latest
Please use it for further communication regarding the project boards, or send me direct email. Thank you all.
DisPre Key components offer.
As many of you have noticed, I’m currently selling matched octets of original Toshiba 2SJ74BL / 2SK170BL. Which is exactly what this preamp needs.
I’m offering an octet Jfets, four Fischer SK95 heat sinks and matching number output transistors for €100, shipping within EU included.
Please stipulate which IDSS you want.
I had originally planned to offer this via a normal ad, but after contacting PMA he graciously allowed me to post in his own thread. Hats off to that gentleman.
So guys, dig in and order these parts to be ready when the board arrives.
PMs preferred.
Regards
RM
As many of you have noticed, I’m currently selling matched octets of original Toshiba 2SJ74BL / 2SK170BL. Which is exactly what this preamp needs.
I’m offering an octet Jfets, four Fischer SK95 heat sinks and matching number output transistors for €100, shipping within EU included.
Please stipulate which IDSS you want.
I had originally planned to offer this via a normal ad, but after contacting PMA he graciously allowed me to post in his own thread. Hats off to that gentleman.
So guys, dig in and order these parts to be ready when the board arrives.
PMs preferred.
Regards
RM
Attachments
4 - 9mA is fine, as it can be trimmed by R8/R9 choice of parallel resistors. Original prototype (still in operation) was built around 8.5mA Idss parts.
@HRDSTL - thank you, but please take into account that the images are from the PCB manufacturer's preview only and the silkscreen on the top side is not visible.
Ok, I will choose Idss myself and pass on that information. Several customers have already lined up.
Your preamp is highly admired Pavel.
R
Your preamp is highly admired Pavel.
R
Last edited:
Pavel,
See below :
www.diyaudio.com/community/threads/replacement-for-toshiba-2sk170-2sj74.317563/post-7278090
One can easily get Toshiba's from the DIY store.
No reason not to use them.
Cheers,
Patrick
Below please find a link to a preliminary BOM:
https://pmacura.cz/dispre-jfet_bom_2025_preliminary.pdf
I would suggest to wait with components orders until the boards are produced (next week) and confirmed for delivery. By now, the existing board requests should be fulfilled.
Please note the part suppliers can be changed according to your domicile and availability. The BOM is just a kind of suggestion only and rather gives you an idea of parts dimensions etc. Critical suggested parts are the JFETs, ALPS pot and the capacitor types like COG/NPO etc.
https://pmacura.cz/dispre-jfet_bom_2025_preliminary.pdf
I would suggest to wait with components orders until the boards are produced (next week) and confirmed for delivery. By now, the existing board requests should be fulfilled.
Please note the part suppliers can be changed according to your domicile and availability. The BOM is just a kind of suggestion only and rather gives you an idea of parts dimensions etc. Critical suggested parts are the JFETs, ALPS pot and the capacitor types like COG/NPO etc.
BC550/560 from Onsemi, etc. are obsolete.
The ones now available is from CDIL.
Just for info,
Patrick
The ones now available is from CDIL.
Just for info,
Patrick
Thank you Patrick. It is of course possible to use a different manufacturer of BC550/560. As said, it is not a critical part. However, I cannot recommend the TTA/TTB instead of BD per your recommendation. This cannot be done without thorough testing and results on more than 10 pcs preamps built. Even then we may get surprised with something unexpected. I am more engineer than a hobbyist and to me a new, different part means a new product that is to be tested and approved.
Oh, as an engineer of 45 years, I totally agree that any public project should only be released after thorough testing.
As I always do.
I am always curious to try out new, modern-day components.
And I only trust reputable manufacturers, who only have the resources to perfect their manufacturing processes.
Just my personal preferences.
Cheers,
Patrick
As I always do.
I am always curious to try out new, modern-day components.
And I only trust reputable manufacturers, who only have the resources to perfect their manufacturing processes.
Just my personal preferences.
Cheers,
Patrick
I have just ordered 5 + 5 pcs of LSK170C/LSJ74C from DigiKey. I want to check them with Dispre 2 - JFET.
And today, finished PCB's have been sent to me and I expect their arrival on Friday or next Monday. After they are at my place, I will contact those who have been interested in the boards. Expected price is $20 or €18 per pc, plus shipment costs (depending on country of destination). For lowest cost overseas, registered mail is planned to be used. Within EU, everything is much easier.
Everyone who pays to me (PayPal) will receive a link to complete documentation (assembly manual and parameters, schematics with part numbers and values, board layout with components placement, BOM). The documentation is not made available in public, however, this thread contains a lot of technical information and hints for the skilled hobbyists.
And today, finished PCB's have been sent to me and I expect their arrival on Friday or next Monday. After they are at my place, I will contact those who have been interested in the boards. Expected price is $20 or €18 per pc, plus shipment costs (depending on country of destination). For lowest cost overseas, registered mail is planned to be used. Within EU, everything is much easier.
Everyone who pays to me (PayPal) will receive a link to complete documentation (assembly manual and parameters, schematics with part numbers and values, board layout with components placement, BOM). The documentation is not made available in public, however, this thread contains a lot of technical information and hints for the skilled hobbyists.
Just curious, do you expect any change or improvement in parameters after replacing BD139/140 by TTA/TTB 004? I do not, after checking the datasheet. I agree it is interesting to check SOTA components, but in case of unobtainium JFET based, discrete line preamp we are in another river. It is a hobby and the way to try something that was good but is lost because of everlasting pressure to reduced costs and high production efficiency. Just the opposite of DIY. We try new op-amps, DAC chips etc. But it is not the case here.
However, we are OT with such consideration and I would prefer not to extend it, please.
Hi Pavel,
In the end, all things considered, the Dispre 2 will be my main preamplifier and the DCG3 only as a headphone amplifier. In the end I will leave the bias at the original value but go for the dual mono concept with one toroidal transformer (4x 15V AC). I want to put UltraBiB dual mono power supplies from Salas with CCS 120mA on each power branch. Since I want to use to Dispre 2 signal sources (DAC, Phono) Phono preamplifier will be from Salas Simplistic NJFET RIAA and obviously I will have to set the gain 4 to 5x, the ideal will be about 4,5x. So one more question for you Pavel, can the Dispre work with 5x gain while maintaining stability? The compensations in the feedback don't need to be changed?
In the end, all things considered, the Dispre 2 will be my main preamplifier and the DCG3 only as a headphone amplifier. In the end I will leave the bias at the original value but go for the dual mono concept with one toroidal transformer (4x 15V AC). I want to put UltraBiB dual mono power supplies from Salas with CCS 120mA on each power branch. Since I want to use to Dispre 2 signal sources (DAC, Phono) Phono preamplifier will be from Salas Simplistic NJFET RIAA and obviously I will have to set the gain 4 to 5x, the ideal will be about 4,5x. So one more question for you Pavel, can the Dispre work with 5x gain while maintaining stability? The compensations in the feedback don't need to be changed?