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Old 10th March 2011, 02:14 AM   #1
janusz is offline janusz  Australia
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Default DIAMOND DIFFERENTIAL INPUT POWER AMPLIFIER EBay kit

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,
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Old 10th March 2011, 02:32 AM   #2
AJT is offline AJT  Philippines
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can you post the links?
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Old 10th March 2011, 02:39 AM   #3
ptempel is offline ptempel  United States
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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.
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Old 10th March 2011, 02:54 AM   #4
janusz is offline janusz  Australia
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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,
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Old 10th March 2011, 09:29 AM   #5
alexcp is offline alexcp  United States
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On the schematic, should R22 and R23 be connected to "OUT" rather than to "IN-"?
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Old 10th March 2011, 09:31 AM   #6
AndrewT is offline AndrewT  Scotland
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I can't find a diamond arrangement.
I can see a cascoded VAS.
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Old 10th March 2011, 09:36 AM   #7
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by alexcp View Post
On the schematic, should R22 and R23 be connected to "OUT" rather than to "IN-"?
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.
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Last edited by AndrewT; 10th March 2011 at 09:38 AM.
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Old 14th March 2011, 09:06 AM   #8
janusz is offline janusz  Australia
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What about lifting R22 and R23 from the nfb line? Acciphase and Sansui have these floating. Most modern amps have these floated. I do not know if there is any advantage having these connected to the nfb line. What do you think?
Has anyone got this amp?

cheers,
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Old 14th March 2011, 09:51 AM   #9
forr is offline forr  France
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Not very similar to Diamond Sansui's circuit, below, which has not a complementary input stage but nevertheless gives a push-pull VAS.

Click the image to open in full size.

Last edited by forr; 14th March 2011 at 09:54 AM.
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Old 15th March 2011, 12:10 AM   #10
janusz is offline janusz  Australia
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Forr,
I was talking about a somewhat different Sansui amp. This one:

cheers,
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