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Old 30th April 2010, 08:20 AM   #1
PMA is offline PMA  Europe
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Default Dispre II PCBs available

I would like to inform those who are interested in Dispre II PCBs, that they are still in production and available.

For more information please visit

Pavel Macura audiopage
Dispre II complementary-symmetrical preamplifier
Dispre II pricelist
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Old 4th May 2010, 08:20 PM   #2
PMA is offline PMA  Europe
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Hello Guys,

I am considering a possibility to design a new version of the Dispre 2 and PCB. Original thread is here:
New DISPRE preamp, successor to previous popular version

The new modification would have 2SK170/2SJ74 JFETs at the input. I would design a new PCB. In case you are interested in such modification, please write here or send me an e-mail.

Thanks,
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Old 5th May 2010, 11:54 PM   #3
Gordy is offline Gordy  United Kingdom
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PMA it is always nice to see your designs. I occasionally visit your site to see if you have new developments.

I think a Jfet input would be a rational and good development. (And perhaps you could consider a gain selection of x2.5 and x5, as I think this would cover the requirements of many people).

Also, I think there may be market interest if you developed a version with an output buffer to provide (Class A) 100 mW into 30 R (as a high quality headphone stage).

Regards,
G.
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Old 6th May 2010, 07:37 AM   #4
Baka is offline Baka  Montenegro
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Well, I am interested to try that new version of the Dispre 2.

Not that I am not satisfied with the current iteration (V4). Au contraire!

I am really curious to know, having in mind the low cost of pcb and necessary parts that makes it a great bargain.

I would only suggest that this version provides more space that is necessary for larger value and better quality elcos (1000/35V or so as per current schematics).

Regards,

Baka

Last edited by Baka; 6th May 2010 at 07:40 AM.
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Old 6th May 2010, 05:53 PM   #5
PMA is offline PMA  Europe
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Gordy and Baka,

thank you for your inputs. I will carefully consider your recommendations. The PCB is under development and modifications are possible.

I expect to release one PCB design with same dimensions and geometry as the older BJT version had. I am asked by my customers to fulfill this requirement. Anyway, it would be possible to place the larger caps.

I am attaching the current status of the design (still under development).

Thanks,
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File Type: pdf dispre-jfet_2.pdf (173.6 KB, 527 views)
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Old 6th May 2010, 07:58 PM   #6
PMA is offline PMA  Europe
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Regarding gain selection - it is implemented in this version. Please note R1, R2, R101 and R102 resistors.
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Old 6th May 2010, 08:27 PM   #7
dodo is offline dodo  Poland
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what will be the difference between you JFET DISPRE II a the jfet pre showed bellow
(take the note - only one output pairs sk/sj with idss 15-16mA

Please consider more space to use motorised pots

what will by the input capacitance of your jfet-dispre with input jfets pairs
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Old 6th May 2010, 08:38 PM   #8
PMA is offline PMA  Europe
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I was asked to modify this preamp
Dispre II complementary-symmetrical preamplifier
for JFET input. So, the resulting preamp would look like the original Dispre 2, with input stage replaced by self-bias JFET complementary-differential. And, the output diamond buffer would have resistors added to control and set idle current, to higher value than in the Dispre 2. Also, there would be a gain selector in the input.

The motorised pot would not be implemented now, but I can consider it as an optional next PCB.

Regards,
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Old 6th May 2010, 10:06 PM   #9
PMA is offline PMA  Europe
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Current design status of the PCB for the JFET version:
Attached Images
File Type: png pcb.PNG (52.2 KB, 1377 views)
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Old 7th May 2010, 07:51 AM   #10
Baka is offline Baka  Montenegro
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Is it possible to move the power supply section (input terminals and power supply caps) to the left side of pcb?

This way this section would be closer to power supply unit and power supply wires would not mess with input/output signal wires and volume pot (rod) on the right side.

Regards,

Baka
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