INVERTED REGULATOR CORRECTION INFO
In post #136 I discovered that the LTP CCS emitter degeneration resistors were missing on the inverted regulators.
In post #139 I put up corrected schematics.
In post #149 you can see how drmaftoon's neatly added through-hole resistors between the transistor leg and its hole.
I thought I'd try using SMD resistors:
While it looks quite neat, I can't really recommend it. I have pretty good soldering skills and this still turned out to be beyond fussy.
If you do want to try it, it might be easier with a very fine tip on your soldering iron. But I'd recommend drmaftoon's method instead.
In post #136 I discovered that the LTP CCS emitter degeneration resistors were missing on the inverted regulators.
In post #139 I put up corrected schematics.
In post #149 you can see how drmaftoon's neatly added through-hole resistors between the transistor leg and its hole.
I thought I'd try using SMD resistors:
While it looks quite neat, I can't really recommend it. I have pretty good soldering skills and this still turned out to be beyond fussy.
If you do want to try it, it might be easier with a very fine tip on your soldering iron. But I'd recommend drmaftoon's method instead.
Attachments
Nice! Thanks for making those available Jeff.
FWIW I got a couple quotes for the non-current transistors from NJ Semi.
US$7.50 per unit on BYD58. That's for a quantity of 10 figuring 8 required and handy to have some spares. They seem to have plenty in stock.
They also have BC239C on hand US$1 each. "$10 line min. / $50 PO min."
If anyone knows them to be not a legit source, let me know. I'm inclined to place an order soon. (Looking back through the thread, seems like Jeff got his BYD58 there to build this very amp, so I'm convinced.)
I think all of the other transistors were in stock at Mouser, except MJE243 which is stocked but backordered.
FWIW I got a couple quotes for the non-current transistors from NJ Semi.
US$7.50 per unit on BYD58. That's for a quantity of 10 figuring 8 required and handy to have some spares. They seem to have plenty in stock.
They also have BC239C on hand US$1 each. "$10 line min. / $50 PO min."
If anyone knows them to be not a legit source, let me know. I'm inclined to place an order soon. (Looking back through the thread, seems like Jeff got his BYD58 there to build this very amp, so I'm convinced.)
I think all of the other transistors were in stock at Mouser, except MJE243 which is stocked but backordered.
I've never used soft start but my transformers are 350VA each it your using 500VA then you may need them.Always used output protection boards (Vallman kits) saved my speaker's more than once.They use replays in the speaker lines but can't hear a problem.Am moving to a solid state design, there is a group buy on this forum for them.Naim used the on-board current limiter on the NAP boards which can be heard working so a lot of people removed the parts.
Fuses in the lines that feed the power supplies or in the lines between the power supplies and the amp-boards.
I have not seen Naim using these, but for me it feels better to have them in.
Even the output transistors in case the speaker terminals are shorted? (I agree that the chance to that happening is small) The BUV20 you are using are pretty powerfull.
You might be right though that we can do without it, but I think that in the test phase it can save me a lot of trouble.
Hi Jeff, I just joined the group. First of all, sorry for my elementary English
I am very interested in the construction of the nap250. It is still possible to buy both the amp and alimentarore cards. Thank you and congratulations
First a disclaimer: we're well out of my knowledge bubble here. But:
The input low pass capacitor (C2) is going to give a fairly steep roll-off, so I don't think changing it will give you what you want.
The input DC-decoupling capacitor (C1) doesn't do any filtering, but it's also a tant and may affect the sound. You could try bipolar electrolytic or polypropylene there. But we're in to capacitor "sound" here, which I know nothing about.
I think @dre is referring to a schematic with different part numbering. C7 on my schematics is a bypass for the bias splitter, which I can't imagine having any effect. I *think* the corresponding number on my schematic would be C3/C4, which are known to affect the sound (although most people comment on the bass with respect to them).
It could also be room acoustics. What source are you using? If it's something like Roon or Audirvana you could do a low-pass filter digitally (I have to do that for my room, but it's in the opposite direction).
Cheers,
Jeff.
The input low pass capacitor (C2) is going to give a fairly steep roll-off, so I don't think changing it will give you what you want.
The input DC-decoupling capacitor (C1) doesn't do any filtering, but it's also a tant and may affect the sound. You could try bipolar electrolytic or polypropylene there. But we're in to capacitor "sound" here, which I know nothing about.
I think @dre is referring to a schematic with different part numbering. C7 on my schematics is a bypass for the bias splitter, which I can't imagine having any effect. I *think* the corresponding number on my schematic would be C3/C4, which are known to affect the sound (although most people comment on the bass with respect to them).
It could also be room acoustics. What source are you using? If it's something like Roon or Audirvana you could do a low-pass filter digitally (I have to do that for my room, but it's in the opposite direction).
Cheers,
Jeff.