of course it would no longer be a 140, but a better and more performing amp.
we have done something similar and in fact the 140 remains very little
some capacitors are eliminated for the signal in series, the final power section is enhanced and the important input stage is activated
I think the 140 is not even a final amp that can offer outstanding performances, in my opinion, of course
we have done something similar and in fact the 140 remains very little
some capacitors are eliminated for the signal in series, the final power section is enhanced and the important input stage is activated
I think the 140 is not even a final amp that can offer outstanding performances, in my opinion, of course
Last edited:
Here's my LTSpice sim of the NAP250; I'm pretty sure the amp circuit is the same as the 140, with the possible exception of the feedback cap.
Avondale Audio do a true complementary version (with MJ15003/MJ15004). Schematic here: https://pinkfishmedia.net/forum/pro...iag.gif&hash=9fa57d2bfbd644d3b46a8f0e040a3d9d
Avondale Audio do a true complementary version (with MJ15003/MJ15004). Schematic here: https://pinkfishmedia.net/forum/pro...iag.gif&hash=9fa57d2bfbd644d3b46a8f0e040a3d9d
Because rail voltages are lower at +/-34V, there are also minor changes to current source resistors and the small signal transistor types used in the NAP140. Over 30 years in production, there were forced changes to several of the semis. There were obviously different cosmetics and PCBs too. I have seen only a sketch (a reverse-engineered schematic) of the real 110/140 model designs. The usual design we see called the NAP140 that is plastered all over the net and modified by Avondale, is actually the 250 model - sans regulated power supply. This is the same as NAP135 and I believe it's also close to the NAP180, a model for safe max. power from an unregulated +/- 40V supply.
Given the high Cob of 30pF for the VAS transistor, this needs to be factored into the value of the Miller compensation cap. It isn't just what it appears to be at all - in fact it varies with the signal as does the output capacitance of the transistor. That's all a part of the distinctive sound quality that you hear. If you were looking for a perfect textbook design with ultra low distortion though, I'm afraid Naim designs aren't for you and simulations might give some strange results that don't agree with expectations.
Can't download your PFM link, Jeff. Could you just link a forum post?
Given the high Cob of 30pF for the VAS transistor, this needs to be factored into the value of the Miller compensation cap. It isn't just what it appears to be at all - in fact it varies with the signal as does the output capacitance of the transistor. That's all a part of the distinctive sound quality that you hear. If you were looking for a perfect textbook design with ultra low distortion though, I'm afraid Naim designs aren't for you and simulations might give some strange results that don't agree with expectations.
Can't download your PFM link, Jeff. Could you just link a forum post?
@Ian, does this work: QUDOS - the brilliant new amplifier boards from Avondale | Page 19 | pink fish media ?
(Thanks for the extra info. I didn't realise the actual 140 was that different from the 250.)
(Thanks for the extra info. I didn't realise the actual 140 was that different from the 250.)
Member
Joined 2009
Paid Member
Thanks Jeff, that's fine. Now I know what a complementary output NAPalike looks like.
Without the additional harmonic content, it probably follows in the footsteps of more recent Naim models toward a diluted sound quality.
Gareth, I'm not saying you're wrong nor that it matters greatly, but I have original values like 62R V 68R VAS emitter resistors in my almost original 140 model. Strangely, this also showed up in some NAP140 Ebay clone kit documentation some years back. They have a relatively high VAS bias current and I think the purpose of closer spec parts was to ensure consistent performance from model to model, which would have been of concern to the designer.
I have also referred to your pic previously here. Note that your pic of a NAP110 and the best image of a 140 at Acoustica.org.uk, show completely refurbed PCBs from Europe, I guess, from the sites where they originated. Your attached pic of the 110 model shows a part rebuilt amplifier with Hungarian(??) NOS output semis, odd wirewound resistors and plastic mounting pads for the small transistors. In fact, almost all components appear to have been replaced, even the small heatsinks. This isn't necessarily bad but it casts doubt on what the the refurbisher intended. i.e. whether they set out to upgrade the design, followed an available schematic instead, used common E6 replacement values or fitted direct replacement values etc.
Without the additional harmonic content, it probably follows in the footsteps of more recent Naim models toward a diluted sound quality.
Gareth, I'm not saying you're wrong nor that it matters greatly, but I have original values like 62R V 68R VAS emitter resistors in my almost original 140 model. Strangely, this also showed up in some NAP140 Ebay clone kit documentation some years back. They have a relatively high VAS bias current and I think the purpose of closer spec parts was to ensure consistent performance from model to model, which would have been of concern to the designer.
I have also referred to your pic previously here. Note that your pic of a NAP110 and the best image of a 140 at Acoustica.org.uk, show completely refurbed PCBs from Europe, I guess, from the sites where they originated. Your attached pic of the 110 model shows a part rebuilt amplifier with Hungarian(??) NOS output semis, odd wirewound resistors and plastic mounting pads for the small transistors. In fact, almost all components appear to have been replaced, even the small heatsinks. This isn't necessarily bad but it casts doubt on what the the refurbisher intended. i.e. whether they set out to upgrade the design, followed an available schematic instead, used common E6 replacement values or fitted direct replacement values etc.
Last edited:
Member
Joined 2009
Paid Member
Yes.
I think I have a few more photos on my computer. One does have to be careful to cross check different sources in case you get something that's been modified. When I get interested in an amplifier I scour the internet for photos. Sometimes they turn up in strange places such as foreign on-line sales websites but they don't stay available for ever. I have collected enough information to reverse engineer a couple of Shindo units and a Leben which I may clone one day as I like the look of them ! The Shindo amps are particularly interesting because he often changed the designs of a model over the years and you can see how they evolved.
Member
Joined 2009
Paid Member
Hi domenico,
Naim maintained a quasi-complementary design for all their NAP and earlier Nait models because of its sound quality, not for reasons of technical improvement or a need to follow every other manufacturer down the path toward making similar generic products. At their prices, they didn't need to turn to Asian manufacture to remain competitive either.
I don't see any point in departing from the NAP formula and likely reverting to a generic design from the 1970s-80s, like so many others. If I wanted a complementary output stage, I think I'd start later in the evolution of audio design and perhaps go MOSFET rather than BJT. Todays' Naim designs have actually moved toward complementary output stages but IMO, the few recent models I have listened to, have also lost much of the distinctive Naim "PRT" sound quality that I grew to like. Note also that Naim never used the sluggish Motorola/On-semi type power transistors as shown in schematics earlier in this thread.
As a matter interest, quasi designs and mixed FET/BJT output stages in general, are often liked for their prodigious even harmonic distortion levels. There are quite a few commercial examples, even among large producers like NAD, if you look carefully.
Naim maintained a quasi-complementary design for all their NAP and earlier Nait models because of its sound quality, not for reasons of technical improvement or a need to follow every other manufacturer down the path toward making similar generic products. At their prices, they didn't need to turn to Asian manufacture to remain competitive either.
I don't see any point in departing from the NAP formula and likely reverting to a generic design from the 1970s-80s, like so many others. If I wanted a complementary output stage, I think I'd start later in the evolution of audio design and perhaps go MOSFET rather than BJT. Todays' Naim designs have actually moved toward complementary output stages but IMO, the few recent models I have listened to, have also lost much of the distinctive Naim "PRT" sound quality that I grew to like. Note also that Naim never used the sluggish Motorola/On-semi type power transistors as shown in schematics earlier in this thread.
As a matter interest, quasi designs and mixed FET/BJT output stages in general, are often liked for their prodigious even harmonic distortion levels. There are quite a few commercial examples, even among large producers like NAD, if you look carefully.
true how much you write.
I think of Naim rather, at least looking at patterns and products, not the high costs to the public, that everything was done in the name of maximum savings and ZERO technical research.
Naim use only one final power transistor for everything.
Here, I see the only positive aspect of the selection almost nothing
But result is always quite limited
however, the circuit is simple and cheap from components to heatsinks
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.