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NAP250 amp boards & regulator boards

JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg PAID
lohk: 2 amp, 2 inverted_reg
john.luckins: 2 amp, 2 inverted_reg
avtech23: 2 amp, 2 inverted_reg
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
gary s: 2 amp, 2 inverted_reg PAID
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
Skunark: 4 amp, 2 original_reg, 2 inverted_reg PAID
 
Sorry about the small board imperfections Jeff. It is brilliant to have the opportunity to build an authentic NAP250 at all and you should be proud of all you have done so far. Thank you!

I've ordered and received the transistors for mine from Cricklewood Electronics and already have BDY58's and BUV60's to try. One or two dilemmas remains in my mind- may be red herrings though? Do we have to use the BC239C's to retain authenticity with the original or can we avoid the voltage breakdown risk altogether and use BC546B's for example. I have a stack of these and note that they were used in the Hackernap design. Also the ones in the Hackernap were selected to give an Hfe offset in the input pair and I could readily achieve that from the stash I have. Do you think there was a selected Hfe offset of the input pair in the original? I'll do a bit of searching through the Hackernap threads to see if I can find the basis of this.

John
 
Hi John,

I don't think the input diff pair has a big impact on the sound. I think BC546Bs would be fine. On the other hand, I tested some 30 BC239Cs, and not a single one avalanched before 50V (and some went over 80V before I stopped).

I think I have it on pretty good authority that Naim did not offset the LTP. I don't know where that whole idea (urban legend?) started, but do let me know if you find the source of it. I'm certainly curious.

As I understand it Naim used a test amplifier with one of the LTP transistors socketed and put the test devices into that socket. Any two that gave the same DC offset at the output were deemed "matched".

Cheers,
Jeff.
 
Boards ordered again.

Cost per board is the same €13.40 (€53.60 per stereo amplifier). I'm eating the cost of the first run.

Shipping is €5.70 untracked, or €12.70 tracked.

PayPal to jeff (at) rokeby (dot) ie.

Please indicate which postage you want. Please also include your shipping address.

Cheers,
Jeff.
 
Boards are back in.

PayPal to jeff (at) rokeby (dot) ie.

Please indicate which postage you want. Please also include your shipping address.


JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg PAID
lohk: 2 amp, 2 inverted_reg
john.luckins: 2 amp, 2 inverted_reg
avtech23: 2 amp, 2 inverted_reg
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
gary s: 2 amp, 2 inverted_reg PAID
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
Skunark: 4 amp, 2 original_reg, 2 inverted_reg PAID
 
Yep, you're all set Gary.

I want to do a bit more checking, but at least the transistors fit this time:

attachment.php


Cheers,
Jeff.
 

Attachments

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Hi Jeff,

Taking the build to the n'th degree I see - even BSW or BA screws (not the new Metric stuff for you it seems).

Any idea as to when you will get these in the mail, more than likely will run into the Christmas season overseas air mail peak season rush now. That does not matter as this is a project into 2020 for me anyway.

Hope you find all OK with the boards with your checking there.

Cheers,

Gary..
 
First batch to ship tomorrow.

JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg PAID
lohk: 2 amp, 2 inverted_reg PAID
john.luckins: 2 amp, 2 inverted_reg PAID
avtech23: 2 amp, 2 inverted_reg
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
gary s: 2 amp, 2 inverted_reg PAID
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
Skunark: 4 amp, 2 original_reg, 2 inverted_reg PAID
 
Jeff, did you see that Nain does not use full bridge but full wave rectification. So there are only two diodes of the bridge in use, and the transformer has two centre tapped windings, therefore the six wires to the bridges. At one bridge the unused pin is used for the front lights.