SX-Amp and NX-Amp

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#82
From Bonsai:
"1. The value of R31 and R30 are low at 15 Ohms (by design) to facilitate good voltage swing on the TIS at high current. If the value of these two resistors was set higher, the TIS current spread would be lower - many fully balanced designs show values of 47 Ohms up to 68 Ohms and I have seen higher.
2. The models used are never perfect, so when compbined with the point directly above, I expect to see some spread in TIS current."

This matches with my findings too when adjusting Hiraga amp VAS current. The VAS current is partially depending on transistors parameters (mainly vbe of vas bjt probably). To keep the low value resistor for the VAS (and keep the perceived dynamic of the amp) one may have to adjust for the previous stage resistors R32 and R33 value for each board implementation....

Fab
 
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#83
fab said:
...The VAS current is partially depending on transistors parameters (mainly vbe of vas bjt probably). To keep the low value resistor for the VAS (and keep the perceived dynamic of the amp) one may have to adjust for the previous stage resistors R32 and R33 value for each board implementation....
Click to expand...
Might be a good idea to put this out there for other people in some detail, including some discussion of what the VAS current should be, or how it should be adjusted to stay in the linear region of the transistor, etc.

I doubt the average person who builds these boards will think of it himself.
 
#84
nx-Amp boards, fresh from the board house:
 

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#86
PMI said:
Might be a good idea to put this out there for other people in some detail, including some discussion of what the VAS current should be, or how it should be adjusted to stay in the linear region of the transistor, etc.

I doubt the average person who builds these boards will think of it himself.
Click to expand...

Yes - good idea, I will add this to the write up when I update it.
 
#87
Bonsai said:
... gold plated I see!

😎
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No, sorry, that is just the light. No gold for free this time, although the initial through-hole VSSA batch did come gold plated at no extra charge. That was sweet.

Other than that, the quality is pretty nice, I think we are benefiting from a discount that really was not intended for diy projects.... 😉
 
#89
pinnocchio said:
When can we send you payment? I guess we should wait for the PSU PCB as well for a single shipment?
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I can try to send it as regular mail in a padded envelope. To Canada, that should be $2.45 for two nx-Amp boards, and maybe another dollar for 4 boards including the power supply.

If they make me send it package rate, you might as well wait for the power supply. Send me a pm w. your address, and I will check into it tomorrow.

As for payment, give me a day to sort out the shipping/mailing options. I am assuming Paypal, $10/board, $20/stereo set, plus shipping.

How does the parts cost look? (I only checked a few key parts, not the whole BOM).
 
#90
I have only created the BoM for the amp board but a few parts are missing like the fuse clip and some smd resistors and caps... Very few parts but so far for two amp modules we're at 65$ CDN. Maybe add in another 10$ for the missing parts.

You can ship both Fab's and my order to the same address so we save on shipping. He will confirm to you.

I will PM my shipping address

Thanks
Do
 
#96
fab said:
I think he has built even more amps than that....😛
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Ok, so more than a collection... so that is like what? ...a hoard of amplifiers? Are other friends invited to listen to them?? We ARE friends now aren't we??? :clown:

(excuse me for a moment, I have to check Yahoo maps for driving distance now...)

So, now that is out of the way, that will be 4 nx-amp boards to pinnocchio's address.
 
#97
PMI said:
Ok, so more than a collection... so that is like what? ...a hoard of amplifiers? Are other friends invited to listen to them?? We ARE friends now aren't we??? :clown:

(excuse me for a moment, I have to check Yahoo maps for driving distance now...)

So, now that is out of the way, that will be 4 nx-amp boards to pinnocchio's address.
Click to expand...

Yep! all 4 nx-amp boards sent to my shipping address and same for the PSU boards.

BTW, Fab does not advertise his creations on his signature but he's got quite a collection too. 😀

Ciao!
Do
 
#99
Updated List

nx-Amp PCB list, now shipping:
---------------------------------------
$10/board, $20/stereo set, + shipping cost + paypal fee (if applicable)

PMI (2 nx-Amp) received
pinnocchio (2nx-Amp) shipped
fab (2 nx-Amp) shipped

ivanlukic (2)
evette (2)
potepuh (2)
JethroTull (2)
Cambe (2)


nx-Amp PSU+Protection PCB, expected week of 22 July:
---------------------------------------------------------------------
(cost will the same $10/board, or very close)

PMI (1)
ivanlukic (1)
pinnocchio (2)
fab (2)
evette (0)
potepuh (1)
JethroTull (2)
Cambe (2)

Please note that the PSU is designed to power BOTH channels, not just one, so there may not be enough PSU boards this round, but more can be ordered.

If there are more inquiries than the handful of people signed up to get boards so far, we can order more.
 
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