Note: 2 amp means 2 amp boards; i.e. enough for one stereo amplifier.
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg SHIPPED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
gary s: 2 amp, 2 inverted_reg SHIPPED
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg SHIPPED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
gary s: 2 amp, 2 inverted_reg SHIPPED
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
Note: 2 amp means 2 amp boards; i.e. enough for one stereo amplifier.
--- subscription list ---
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg SHIPPED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
gary s: 2 amp, 2 inverted_reg SHIPPED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
--- subscription list ---
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg SHIPPED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
gary s: 2 amp, 2 inverted_reg SHIPPED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
Notes on parts substitutions:
The VAS transistors (ZTX653 & 753) should not be substituted. They're likely responsible for a lot of the Naim sound, and the feedback compensation is based on their properties.
Substitution of the LTP transistors (BC239) is OK. BC546 comes to mind.
Substitution of the LTP CCS transistor and regulator TO92s (MPSA06 & 56) is OK, but then they're easy to get so why bother.
Substitution of the Vbe spreader (ZTX108) is probably OK. The e-line package has a lower thermal resistance, so using a TO92 might give you slower temp compensation.
Substitution of the drivers (MJE243 & 253) should only be done if you know how to adjust feedback compensation. Even then, you may be messing up JV's phase compensation. Proceed with caution.
Substitution of the outputs (BDY58) is OK. Lots of opinions here. JV liked fast. I'm going to try BDY58 (10Mhz), NA001 (presumably 10Mhz) and BUV20 (8Mhz). Others swear by the MJ15003 (but it's notably slower at 2MHz).
Styroflex (styrene) caps. I'm not much of a subjectivist when it comes to caps. I personally think substituting silver mica or C0G ceramics would be fine. Others will disagree.
Tantalum caps. These have a lot of distortion, which means they're contributing to the sound. If you want to substitute, you're on your own. You can experiment with a single vs double feedback caps (the 47uF tants right next to each other in the middle of the board). Early NAPs had single; later had double.
Electrolytic caps. The ESR of the electrolytics at the regulator outputs is critical. You can substitute, but make sure that the ESR is 1.7 ohms or larger. Otherwise it will oscillate.
Resistors. Use metal film everywhere except for the 3W & 5W'ers, which can be wirewound. I'm using 0.6W for all the metal film. 1/4W or even 1/8W would probably be fine in most places, but if you're going to do this run the sims to make sure. I've seen NAP boards with a lot of discolouration under some of the resistors....
Diodes. You can substitute here, but I'd make sure that the clamp diodes (1N5621) can handle at least a couple of A pulsed current. Naim used smaller, but I've also seen boards where they've failed.
These recommendations are from my research. I'm a DIYer, not an expert. If your research or experience has yielded different answers then carry on.
Either way, have fun!
Cheers,
Jeff.
The VAS transistors (ZTX653 & 753) should not be substituted. They're likely responsible for a lot of the Naim sound, and the feedback compensation is based on their properties.
Substitution of the LTP transistors (BC239) is OK. BC546 comes to mind.
Substitution of the LTP CCS transistor and regulator TO92s (MPSA06 & 56) is OK, but then they're easy to get so why bother.
Substitution of the Vbe spreader (ZTX108) is probably OK. The e-line package has a lower thermal resistance, so using a TO92 might give you slower temp compensation.
Substitution of the drivers (MJE243 & 253) should only be done if you know how to adjust feedback compensation. Even then, you may be messing up JV's phase compensation. Proceed with caution.
Substitution of the outputs (BDY58) is OK. Lots of opinions here. JV liked fast. I'm going to try BDY58 (10Mhz), NA001 (presumably 10Mhz) and BUV20 (8Mhz). Others swear by the MJ15003 (but it's notably slower at 2MHz).
Styroflex (styrene) caps. I'm not much of a subjectivist when it comes to caps. I personally think substituting silver mica or C0G ceramics would be fine. Others will disagree.
Tantalum caps. These have a lot of distortion, which means they're contributing to the sound. If you want to substitute, you're on your own. You can experiment with a single vs double feedback caps (the 47uF tants right next to each other in the middle of the board). Early NAPs had single; later had double.
Electrolytic caps. The ESR of the electrolytics at the regulator outputs is critical. You can substitute, but make sure that the ESR is 1.7 ohms or larger. Otherwise it will oscillate.
Resistors. Use metal film everywhere except for the 3W & 5W'ers, which can be wirewound. I'm using 0.6W for all the metal film. 1/4W or even 1/8W would probably be fine in most places, but if you're going to do this run the sims to make sure. I've seen NAP boards with a lot of discolouration under some of the resistors....
Diodes. You can substitute here, but I'd make sure that the clamp diodes (1N5621) can handle at least a couple of A pulsed current. Naim used smaller, but I've also seen boards where they've failed.
These recommendations are from my research. I'm a DIYer, not an expert. If your research or experience has yielded different answers then carry on.
Either way, have fun!
Cheers,
Jeff.
IMPORTANT NOTE on diodes:
You might notice the discrepancy between some of the spec'ed diodes and their footprints.
For instance,
1N4148 is a DO-35, but has a DO-41 footprint on the board
1N4004 is a DO-41, but has an A-405 footprint on the board
1N5621 is a DO-15 with a DO-15 footprint
I normally put the smaller diodes on larger footprints to allow the silkscreen to be more readable. (Of course there's no silkscreen here, but hey, old habits die hard.)
Anyway, the holes are not oversized, so if you substitute the 1N4148 you need to stay in a DO-35 package (or be prepared to possibly have to drill the holes out a bit for a DO-41).
All Zeners should be DO-35 (although again their footprints are DO-41).
Clear as mud?
You might notice the discrepancy between some of the spec'ed diodes and their footprints.
For instance,
1N4148 is a DO-35, but has a DO-41 footprint on the board
1N4004 is a DO-41, but has an A-405 footprint on the board
1N5621 is a DO-15 with a DO-15 footprint
I normally put the smaller diodes on larger footprints to allow the silkscreen to be more readable. (Of course there's no silkscreen here, but hey, old habits die hard.)
Anyway, the holes are not oversized, so if you substitute the 1N4148 you need to stay in a DO-35 package (or be prepared to possibly have to drill the holes out a bit for a DO-41).
All Zeners should be DO-35 (although again their footprints are DO-41).
Clear as mud?
All clear to me Jeff, as long as the specified Diode is used in the correct location, then that is all one needs to worry about - oh and yes install it with the correct orientation, especially as there is no silkscreen to follow - so double check everything when it comes to stuffing all 4 pcb's would be my advice here for all components..
I haven't heard from a couple of the subscribers. On Dec 16 I'm going to move anyone who hasn't paid yet to the waiting list and open it up to first-come first-served.
Cheers,
Jeff.
Note: 2 amp means 2 amp boards; i.e. enough for one stereo amplifier.
--- subscription list ---
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg RECEIVED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
gary s: 2 amp, 2 inverted_reg SHIPPED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
Cheers,
Jeff.
Note: 2 amp means 2 amp boards; i.e. enough for one stereo amplifier.
--- subscription list ---
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg RECEIVED
john.luckins: 2 amp, 2 inverted_reg SHIPPED
avtech23: 2 amp, 2 inverted_reg SHIPPED
gary s: 2 amp, 2 inverted_reg SHIPPED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
I do not know if makes a big difference, but with the NAIM amplifiers the Baxandall Diode as far as I know never was a 1N4004, but merely a 1N4148.
The Elektor Hybrid Amplifier cleverly uses a 2SC1815BL as a diode here - for better linearity, I guess (base and collector connected together of course).
The Elektor Hybrid Amplifier cleverly uses a 2SC1815BL as a diode here - for better linearity, I guess (base and collector connected together of course).
Last edited:
Hi Klaus,
My research also led to the FR103 for clamp diodes, although they're obsolete and I couldn't find a source for them. I did come across several pictures of toasted FR103s, so the 1N5621 seemed like a reasonable substitute.
I'm less clear on the Baxandall. Naim did appear to use the 1N4148. While my sims show it having to dissipate 200mW running full whack into a 3ohm load (cf: Linn Isobariks), I've never seen one toasted, so I don't think that would have been enough to cause me to deviate from the original spec. So why did I?
Oh to still have the memory of a younger man....
Cheers,
Jeff.
My research also led to the FR103 for clamp diodes, although they're obsolete and I couldn't find a source for them. I did come across several pictures of toasted FR103s, so the 1N5621 seemed like a reasonable substitute.
I'm less clear on the Baxandall. Naim did appear to use the 1N4148. While my sims show it having to dissipate 200mW running full whack into a 3ohm load (cf: Linn Isobariks), I've never seen one toasted, so I don't think that would have been enough to cause me to deviate from the original spec. So why did I?
Oh to still have the memory of a younger man....
Cheers,
Jeff.
I did some more research on the Baxandall. While I didn't find much, I did find a recommendation from @Elvee that speed matters.
So originality favours the 1N4148.
But if you'd like the possibility of a bit more performance and a bit more survivability, the MUR120 looks to be a good candidate.
Cheers,
Jeff.
So originality favours the 1N4148.
But if you'd like the possibility of a bit more performance and a bit more survivability, the MUR120 looks to be a good candidate.
Cheers,
Jeff.
One more funny detail about the NAP250 - it may have been discussed before, but probably a long time ago:
The input socket of the Classic 250 is a single normal three pin XLR socket, wired L, R, Ground. The cable is, or at least was when I opened one more than 30 years ago, a bog standard mains cable, 1.5mm2, blue, black and yellow/green, unscreened.
Conclusio: Consequently low impedances make expensive cables unnecessary.
I still believe that, although with many components it does not seem to be that easy.
The input socket of the Classic 250 is a single normal three pin XLR socket, wired L, R, Ground. The cable is, or at least was when I opened one more than 30 years ago, a bog standard mains cable, 1.5mm2, blue, black and yellow/green, unscreened.
Conclusio: Consequently low impedances make expensive cables unnecessary.
I still believe that, although with many components it does not seem to be that easy.
The NAP200 - still quasi complimentary, also due to the clearly visible bax diode - uses a 12 Ohm resistor for the Zobel part (probably with the usual 100nF). Also the bias tracking transistor sits underneath the board (maybe touching the case).
An externally hosted image should be here but it was not working when we last tested it.
And it is the same for the NAP300
An externally hosted image should be here but it was not working when we last tested it.
Note: 2 amp means 2 amp boards; i.e. enough for one stereo amplifier.
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg RECEIVED
john.luckins: 2 amp, 2 inverted_reg RECEIVED
gary s: 2 amp, 2 inverted_reg RECEIVED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg RECEIVED
avtech23: 2 amp, 2 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff
JeffYoung: 6 amp, 2 original_reg, 4 inverted_reg RECEIVED
lohk: 2 amp, 2 inverted_reg RECEIVED
john.luckins: 2 amp, 2 inverted_reg RECEIVED
gary s: 2 amp, 2 inverted_reg RECEIVED
Skunark: 8 amp, 4 original_reg, 4 inverted_reg RECEIVED
avtech23: 2 amp, 2 inverted_reg SHIPPED
ultima legion: 2 amp (original_reg, inverted_reg, or both?)
jean michael: 4 amp, 4 inverted_reg
Quantensprung: 4 amp, 2 original_reg, 2 inverted_reg
--- waiting list ---
pem1: 2 amp, 2 original_reg, 2 inverted_reg
Cheers,
Jeff