Hi,
I have just purchased this kit. I believe it's pretty fast and somewhat resembles older Sansui PA with differential diamond input.
Is there anyone who has built it?
It might be beneficial to share experiences and discuss potential modifications. The kit is is not expensive - $100 for two boards and all parts including on board speaker protection.
Output devices are njw3281/1302.
PA's diagram is attached. W2 and R28 are deleted, R16=220ohm now.
All comments invited.
cheers,
I have just purchased this kit. I believe it's pretty fast and somewhat resembles older Sansui PA with differential diamond input.
Is there anyone who has built it?
It might be beneficial to share experiences and discuss potential modifications. The kit is is not expensive - $100 for two boards and all parts including on board speaker protection.
Output devices are njw3281/1302.
PA's diagram is attached. W2 and R28 are deleted, R16=220ohm now.
All comments invited.
cheers,
Attachments
Maybe this is the kit?
Diamond differential power amp kit spk protection pair! - eBay (item 220630577557 end time Mar-28-11 02:36:27 PDT)
Looks nice and has speaker protection.
Diamond differential power amp kit spk protection pair! - eBay (item 220630577557 end time Mar-28-11 02:36:27 PDT)
Looks nice and has speaker protection.
That's the same kit but I got it from tubeshunter as his kit has otput transistors included
link:
2 X DIAMOND DIFFERENTIAL INPUT POWER AMPLIFIER KIT! - eBay (item 380247429645 end time Mar-27-11 19:02:03 PDT)
cheers,
link:
2 X DIAMOND DIFFERENTIAL INPUT POWER AMPLIFIER KIT! - eBay (item 380247429645 end time Mar-27-11 19:02:03 PDT)
cheers,
I don't understand.
I see it now, the two schematics are different.
The first shows and extra connection from R22, 23 to -IN that is not shown in the second schematic.
Last edited:
Not very similar to Diamond Sansui's circuit, below, which has not a complementary input stage but nevertheless gives a push-pull VAS.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
dinamic1,
My kit came with no notes whatsoever so I wrote to tubeshunter. Below in PS is his response. I have downloaded both circuit diagrams from these addresses.
I haven't built the kit yet. I've asked a friend of mine to run simulation of this amp and this morning I got his reply. It's not a stunning amp like Stochino but pretty good. It's sensitive to the quality of PS. Consequently, I will use regulated PS +/-58V for the voltage stage and double bridge +/-55V for the output.
At 1W THD is 0.000362
h2 = -126dB, h3 =-113dB
R21 must be 220ohm while the simulation showed that zero offset was achieved with R16=195 ohm. It may be better then to leave R28 and W2 in the circuit and preset R16, R28 and W2 to give 195 ohm. When hot one may need to adjust that setting a touch.
cheers,
PS
Dear pradzyndaria,
Hi! 45V-0V-45V power transformer is OK unless you upgrade the voltage rating of some capacitors to 80VDC.
Circuit diagram (Power amp):
http://www.pix8.net/pro/pic.php?u=14821Z2xl&i=11562079
Circuit diagram (speaker protection):
http://www.pix8.net/pro/pic.php?u=14821Z2xl&i=11562080
Note:
1. W2 - omitted
2. "***" = 220 ohm
Adjustment:
1. Apply power but do not install power outputtransistors in this moment, adjust W1 to make 1K (FET drain resistor) to 2.3---2.6VDC
2. Adjust W3 to set the voltage difference between pin 1 & 3 of power output transistor to 0.45V or less. Do not install power output transistor in this moment too!
3. Test the DC offset. Install the power output transistors in case of the output DC offset is 25mV or less. Otherwise check! Adjust W3 and check the voltage drop of 0.22 ohm / 5W resistor. 10mV to 40mV (depends on effiency of the heatsinks) is ideal volatge drop.
- tubeshunter
My kit came with no notes whatsoever so I wrote to tubeshunter. Below in PS is his response. I have downloaded both circuit diagrams from these addresses.
I haven't built the kit yet. I've asked a friend of mine to run simulation of this amp and this morning I got his reply. It's not a stunning amp like Stochino but pretty good. It's sensitive to the quality of PS. Consequently, I will use regulated PS +/-58V for the voltage stage and double bridge +/-55V for the output.
At 1W THD is 0.000362
h2 = -126dB, h3 =-113dB
R21 must be 220ohm while the simulation showed that zero offset was achieved with R16=195 ohm. It may be better then to leave R28 and W2 in the circuit and preset R16, R28 and W2 to give 195 ohm. When hot one may need to adjust that setting a touch.
cheers,
PS
Dear pradzyndaria,
Hi! 45V-0V-45V power transformer is OK unless you upgrade the voltage rating of some capacitors to 80VDC.
Circuit diagram (Power amp):
http://www.pix8.net/pro/pic.php?u=14821Z2xl&i=11562079
Circuit diagram (speaker protection):
http://www.pix8.net/pro/pic.php?u=14821Z2xl&i=11562080
Note:
1. W2 - omitted
2. "***" = 220 ohm
Adjustment:
1. Apply power but do not install power outputtransistors in this moment, adjust W1 to make 1K (FET drain resistor) to 2.3---2.6VDC
2. Adjust W3 to set the voltage difference between pin 1 & 3 of power output transistor to 0.45V or less. Do not install power output transistor in this moment too!
3. Test the DC offset. Install the power output transistors in case of the output DC offset is 25mV or less. Otherwise check! Adjust W3 and check the voltage drop of 0.22 ohm / 5W resistor. 10mV to 40mV (depends on effiency of the heatsinks) is ideal volatge drop.
- tubeshunter
Hi Janusz,
Thanks for showing a more recent Diamond Sansui circuit than mine.
However I think it was fatal to Sansui, because in search of having a very high slew rate and low distorsion, Sansui compromised the feedback stability and its high power amps using this circuits were not reliable.
A pity that Sansui does not exist anymore, because I very much like its products.
Thanks for showing a more recent Diamond Sansui circuit than mine.
However I think it was fatal to Sansui, because in search of having a very high slew rate and low distorsion, Sansui compromised the feedback stability and its high power amps using this circuits were not reliable.
A pity that Sansui does not exist anymore, because I very much like its products.
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