See the parts advice and mod. suggestions here: Modifying Naim Audio power amplifiers It's dated but useful for getting the general idea of what's important. Don't substitute ZTX653/753 transistors or any others you can avoid because most of them do matter if you're serious about the particular sound quality. Not everything comes in the mail from Ebay, Mouser or Digikey - in the US, you'll also find these ZTX types at Newark/Element14: https://www.newark.com/c/semiconductors-discretes/more-semiconductors-discretes .Unfortunately, the choice of TO3 output transistors restricts your options severely as the remaining available types are mostly limited to slower switching speeds.
Last edited:
Sigh. I wish I had noticed that.
The issue with 2 input grounds is a red herring -- some of the versions of original NAP-140 boards also show that.
For transistor substitutions I am considering:
For BC239C, replace with BC550C
For ZTX108, replace with BC546
For TO-3 output transistors: MJ21194 or MJ15003
I'll try to stick with the ZTX753/ZTX763 pair even if it means ordering 1 transistor from a different supplier.
My advice to you if you want to understand how to design an audiophile performance amplifier is to throw your Doug Self book on your gas grill the next time you are having a BBQ. Then, purged of propaganda, examine what Naim have done and enjoy trying to understand why they did it. Otherwise you might make the mistake of thinking Naim made all sorts of basic errors.
Member
Joined 2009
Paid Member
Some dated and/or copied but not understood details:
1. Quasi-comp was a great idea when PNP power transistors were expensive and uncommon But there are compromises that go away when you use complimentary transistors. ie no reason to do this today. The most important is cross coupling, which is a big advantage, very important.
2. There are 3 or 4 unnecessary bias drops that subtract from the output voltage potential, add to the output saturation voltage, reduce the efficiency and max power output. There are reasons for these but there are better ways to accomplish the same thing.
3. The NPN driver is connected to the wrong side of the 27R in the collector of the VBE multiplier.
4. It really needs current limit.
Oh? Suddenly this is an old thread and I see others have already said the same things. I guess I have to check the date.
1. Quasi-comp was a great idea when PNP power transistors were expensive and uncommon But there are compromises that go away when you use complimentary transistors. ie no reason to do this today. The most important is cross coupling, which is a big advantage, very important.
2. There are 3 or 4 unnecessary bias drops that subtract from the output voltage potential, add to the output saturation voltage, reduce the efficiency and max power output. There are reasons for these but there are better ways to accomplish the same thing.
3. The NPN driver is connected to the wrong side of the 27R in the collector of the VBE multiplier.
4. It really needs current limit.
Oh? Suddenly this is an old thread and I see others have already said the same things. I guess I have to check the date.
Last edited:
Yes, a lot of dismissive comments and proofs that we can't seriously be enjoying what we prefer to hear, have passed through and around these pages. The central issue is the same whenever heads clash over the merits of subjective assessment v scientific and instrumental proofs. This just amounts to saying that what we will hear through brand X is closer to the original. ergo: must sound better.
'Fact is, the essential Naim electronics and system of connected boxes was not all decided by engineers. Somehow, the demand for the product continues though, decades later and still with prices that remain particularly high. Yes, there are a lot of nits that engineers are wont to pick from Naim products but let them - almost nothing bad has happened as a result in near 50 years, still with many of the same design flaws - more than can be said for the mountain of long forgotten, technically better products.
Regarding the protection system, most designers still resort to mechanical relays, sometimes backed up by muting circuits. Typically, these bring their own failures because of their slow action and breakdown, both mechanical and of the small electrolytics in the control circuits. Even so, the service requirements for Naim products shouldn't be ignored IMV, whether you leave it to authorised agents or DIY.
I've read claims that the VI limiters ruin Naim sound. Considering that we have liked the sound regardless for decades and most claims are just parroted across forums, I think this is exaggerated or applies to amplifiers needing some attention but newer models use a dual slope limiting design that has much less chance of intrusion on signal peaks. If you are using your system within suggested limits, you don't hear any effects but if your speakers are small or otherwise very inefficient, you may well have a problem but attempting to fix it simply by removing the only protection beyond the mains fuse is plainly unwise.
'Fact is, the essential Naim electronics and system of connected boxes was not all decided by engineers. Somehow, the demand for the product continues though, decades later and still with prices that remain particularly high. Yes, there are a lot of nits that engineers are wont to pick from Naim products but let them - almost nothing bad has happened as a result in near 50 years, still with many of the same design flaws - more than can be said for the mountain of long forgotten, technically better products.
Regarding the protection system, most designers still resort to mechanical relays, sometimes backed up by muting circuits. Typically, these bring their own failures because of their slow action and breakdown, both mechanical and of the small electrolytics in the control circuits. Even so, the service requirements for Naim products shouldn't be ignored IMV, whether you leave it to authorised agents or DIY.
I've read claims that the VI limiters ruin Naim sound. Considering that we have liked the sound regardless for decades and most claims are just parroted across forums, I think this is exaggerated or applies to amplifiers needing some attention but newer models use a dual slope limiting design that has much less chance of intrusion on signal peaks. If you are using your system within suggested limits, you don't hear any effects but if your speakers are small or otherwise very inefficient, you may well have a problem but attempting to fix it simply by removing the only protection beyond the mains fuse is plainly unwise.
I just noticed this. But it isn't a mistake. Basically we can spread dummy resistors all over the circuit (at every bases, LTP emitters, along supply lines, in series with Miller cap, etc.). The more the resistors the easier or the more options we have in achieving the design objectives (some Rs will in the end need to be zeros of course).
I’ll check it out. The premise seems impractical with almost evetything widely dispersed indelibly on hard drives these days. I must confess I am guilty of permanently deleting numerous PDF files and Word documents.
Admittedly, my grill suggestion has the drawback of tainting the flavour of your food. You wouldn’t want that. Perhaps a steel bucket and a blowtorch might be better?
Naim still uses quasi complementary in all its products except the Statement.
What benefit would changing this bring?
Differences between various vbe multipliers
Connecting to the wrong side of the resistor shows that the designer did not understand it's purpose. But today with penny transistors, the two transistor circuit is a better choice.
Member
Joined 2009
Paid Member
It's easy to jump to that conclusion, but the designer isn't here to answer to the question so let's assume it was one of many real or accidental design decisions that came about as part of the creating process. Afterall, if we engineer all the 'faults' out of this amp, it'll no longer be a NAP 140 will it.
Having said that, I re-engineered the thermal feedback loop in my design to ensure stability under a wider range of conditions as I believe it provides an improvement without robbing the end result of it's authenticity.
Having said that, I re-engineered the thermal feedback loop in my design to ensure stability under a wider range of conditions as I believe it provides an improvement without robbing the end result of it's authenticity.
Yes, that's exactly the point of cloning designs from the past. Anything that is modified or improved to bring it to SOTA standards of design excellence, will eventually default to the same high standard of linearity or even the same topology, reworked for the nth time and presented here by one of our competent analog design and simulation wizards.
Good for them but not so good for those looking to hear the particular sound quality that put the original product on the map, so to speak. That desire is actually the impetus that keeps most of us here and at hundreds of other audio forums globally. We've seen what happens when experts have only themselves to discuss SOTA design and I suggest it's pretty boring, even for them, to just be commenting on technical journals, articles, professional reviews etc. and mulling over matters little different to those in the workplace
Something a little more interesting, is to see how today's Naim engineers tackle the problem of preserving Naim sound quality in the modern world of electronics development and evolving entertainment products. That has to be difficult in the high-end audio power market.
What is State Of The Art (SOTA) in audio?
Should we judge based on sonic performance?
I don't think that much has changed in audio power amplifiers since the 1970s. Technology has changed: more reliable transistors, faster and more powerful. Smaller electrolytic capacitors. Faster opamps. More sensitive and wider bandwidth measurement equipment. But none of these is driven by the audio industry; the SOTA is driven by big industries like computing and telecommunications.
If you judge SOTA in audio amplifiers according to sonic performance then the NAP design that hasn't changed much since the 1970s is surely still it. Judging by reviews it is hard to find much that is better at music without looking at valve devices. And I'm sure it would be unpopular to talk about valves being SOTA.
The high-end audio industry is a very small niche driven by individual enthusiasts. If you look at their credentials they are usually modest: Julian Vereker was a car racing driver. They are practical people who craft existing technology. The audio industry needs a major breakthrough and this won't come from craftsmen. I don't think class D is it; like MP3 it is a way to save resources rather than achieve a performance breakthrough. The sort of investment needed in brains and money is unlikely to be found in the niche audiophile industry.
The big technology changes in audio are driven by big companies. CD for example from Philips and Sony was never intended to be an audiophile format, it was intended to replace vinyl and be cheaper to make and more reliable. The format is on the very edge of being good enough and the DAC technology took a long time to get anywhere near good enough for audiophiles.
So what is meant by SOTA in audio amplifiers? The SOTA in power transistors are FET and IGBTs (intended for switching applications) but Naim continue to use bipolars in all their products including The Statement, as do some other audiophile brands. Some argue that valves continue to be the best devices (compromised by output transformers) implying valves are SOTA. Resistors haven't changed much aside from better tolerances and reliability; some are getting worse with thick film technology. Large capacitor technology is largely driven by switch mode psus and smaller caps for computer motherboards and mobile phones, both seeking compactness and lower cost. High power linear psus are virtually extinct. So we now see cottage industries making specialist audiophile components themselves or begging the corporate manufacturers to make special runs (like Audionote trying to get Rubycon to make more Black Gate).
There just isn't the money in high end audio. It relies on cobbling together parts designed for other markets. Big, rich companies like Apple annoy me because they neglect audio more and more in their products; iPhone XS may be a SOTA mobile but for earphones you have to add their DAC dongle to it or wireless earbuds, both of which are nothing short of sonic crime, IMO.
Should we judge based on sonic performance?
I don't think that much has changed in audio power amplifiers since the 1970s. Technology has changed: more reliable transistors, faster and more powerful. Smaller electrolytic capacitors. Faster opamps. More sensitive and wider bandwidth measurement equipment. But none of these is driven by the audio industry; the SOTA is driven by big industries like computing and telecommunications.
If you judge SOTA in audio amplifiers according to sonic performance then the NAP design that hasn't changed much since the 1970s is surely still it. Judging by reviews it is hard to find much that is better at music without looking at valve devices. And I'm sure it would be unpopular to talk about valves being SOTA.
The high-end audio industry is a very small niche driven by individual enthusiasts. If you look at their credentials they are usually modest: Julian Vereker was a car racing driver. They are practical people who craft existing technology. The audio industry needs a major breakthrough and this won't come from craftsmen. I don't think class D is it; like MP3 it is a way to save resources rather than achieve a performance breakthrough. The sort of investment needed in brains and money is unlikely to be found in the niche audiophile industry.
The big technology changes in audio are driven by big companies. CD for example from Philips and Sony was never intended to be an audiophile format, it was intended to replace vinyl and be cheaper to make and more reliable. The format is on the very edge of being good enough and the DAC technology took a long time to get anywhere near good enough for audiophiles.
So what is meant by SOTA in audio amplifiers? The SOTA in power transistors are FET and IGBTs (intended for switching applications) but Naim continue to use bipolars in all their products including The Statement, as do some other audiophile brands. Some argue that valves continue to be the best devices (compromised by output transformers) implying valves are SOTA. Resistors haven't changed much aside from better tolerances and reliability; some are getting worse with thick film technology. Large capacitor technology is largely driven by switch mode psus and smaller caps for computer motherboards and mobile phones, both seeking compactness and lower cost. High power linear psus are virtually extinct. So we now see cottage industries making specialist audiophile components themselves or begging the corporate manufacturers to make special runs (like Audionote trying to get Rubycon to make more Black Gate).
There just isn't the money in high end audio. It relies on cobbling together parts designed for other markets. Big, rich companies like Apple annoy me because they neglect audio more and more in their products; iPhone XS may be a SOTA mobile but for earphones you have to add their DAC dongle to it or wireless earbuds, both of which are nothing short of sonic crime, IMO.
Last edited:
Hello All.,
I try to make this Amplifier with this circuit...
I use power rail 35-0-35 Vdc
But it's have DC Voltage in speaker out put point about 75% (25-26Vdc) of Voltage rail...
This circuit is correct or not
But Vbe of all transistor it's ok about 0.55- 0.58 Vdc
If it's incorrect Schem Circuit., Could you advice me please!
Best Regards..Chaos
Naim Clone - IMG.LIVE
An externally hosted image should be here but it was not working when we last tested it.
I try to make this Amplifier with this circuit...
I use power rail 35-0-35 Vdc
But it's have DC Voltage in speaker out put point about 75% (25-26Vdc) of Voltage rail...
This circuit is correct or not
But Vbe of all transistor it's ok about 0.55- 0.58 Vdc
If it's incorrect Schem Circuit., Could you advice me please!
Best Regards..Chaos
Naim Clone - IMG.LIVE
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Member
Joined 2009
Paid Member
I suspect that Naim's modern products are not about continuation of the old Naim sound. Those days are gone but they served a key role - to establish and grow the brand. Now they can produce SOTA amplifiers that are, I expect, more neutral, better suited to modern speakers, music and tastes. I often view some of my projects as 'industrial archaeology'.
Last edited:
Member
Joined 2009
Paid Member
I could see no purpose for it. The key to the Vbe multiplier that I used is the emitter degeneration, which allows the Vbe gain to be adjusted for proper thermal tracking when there is close physical connection between the Vbe device and output power device. This is different from the original approach where the native Vbe gain is too high for a quasi-comp output stage so for proper functioning the Vbe device has to be separated from the output device and left hanging in the air or put into contact with specific points on the chassis in order to accomplish the same task. This makes it dependent on the mechanical details of the amplifier and it's enclosure and air flow etc. which I did't want. So I engineered a more robust solution for DIY purposes.
Last edited:
Understandable. Well if you have time you might audition your TGM10 using a similar value, maybe higher like 33 ohms.