These two Chinese boards seem to be the right thing! They have amazingly low THD+N!!! I have ordered all components from reputable suppliers. Some transistors aren't originals but Inchange + CDIL replacements seem to be OK.
Otherwise, NHB-108 is a fine project. There is nothing wrong with the board. The whole trick is really good power supply and adequate wiring. Mine is now completely silent, like turned-of without signal at the input.
I use: two separate 30VAV 500 VA toroids, followed by capacitance multiplier followed by 4X20mF 63V capacitors before the amplifier. Sound is great.
I use this capacitance multiplier Designed by Prasi, Mark Johnson and Gtose. The thread is here.
Great stuff.
Hi Hattori,
Now, I have tested both L12-2 and NHB-108, side-by-side at similar conditions. Though, it may sound unfair to compare a copy of an amplifier that costs tens of thousands to a midget that costs just "two small ordinary breakfasts". Yet, I did it out of curiosity because you have put an interesting question:
Indeed, that little amplifier is fine and technically sound. It produces surprisingly good measurements, comparable to these of NHB-108. Also, it has much lower distortion compared to the notoriously expensive NHB-108. Just think about that. I believe that the end result may sound equally good or even better than NHB-108. In addition to that L12-2 is much easier to build and achieve excellent results even with a power supply from a single transformer.
I have compared them using the same good power supply utilizing capacitance multiplier with just few mV ripple. L12-2 has slightly, not significantly worse response to square waves and also has some insignificant cross-over problems. Though, crossover distortion problems occur only at low voltage rails (+-22VDC) whilst at 42 volts crossover distortion vanishes completely within the entire audible region.
I will keep this little midget and build a nice housing for it - it deserves it.
However, when NHB-108 is built properly, with good power supply and proper wiring, it shines.
-------------------------------------------
With all respect to notoriously famous designers, we should identify snake oil in their statements (see the quote below) and ignore them if misleading.
They say we should "listen to the Sound" just to distract us from shortcomings of their products. That is the way they make money and that is why they don't want us to look at and analyze measurements. Their fanboys are even worse in a crowded audiophile echo chamber.
I used NHB-Boards from 2017 with built in speaker relays but no servo. Dual Mono PSU.
I really like the sound, however, I can sometimes hear crackling sounds from one speaker... I hear it after disconnecting RCA inputs. So its the amplifier. However when I take it to my workshop room... its dead quiet.. I have no idea what it is... But its annoying, so I am building an A-60 clone from Douk...
I really like the sound, however, I can sometimes hear crackling sounds from one speaker... I hear it after disconnecting RCA inputs. So its the amplifier. However when I take it to my workshop room... its dead quiet.. I have no idea what it is... But its annoying, so I am building an A-60 clone from Douk...
I am also building A-60. I already have built a larger A60+ which sounds great but is a bit too large and too hot. I feel like a kid in a candy shop, I want them all. Now, MX50SE arrives after Easter, then L20.5.... This hobby is fun.
Indeed K-amps,Yes... A-60 runs quite hot !
I like its warm detailed sound though
All heat it generates pays-of with great sound. This amp is hot like Krells but has much more delicate sound. Awesome!
Erlend,
What you do is the right way to go. The cost of the amplifier board itself is just a fraction of investment into adequate power supply and heat sinks required to extract the maximum performance from this amplifier.
Now, it is the right time to revive that A60+ conversation. I'll re-direct this conversation there get back there later today with some quite interesting information.
Hello Berlusconi, this is very interesting info.Hi Hattori,
Now, I have tested both L12-2 and NHB-108, side-by-side at similar conditions"
"I will keep this little midget and build a nice housing for it - it deserves it.
However, when NHB-108 is built properly, with good power supply and proper wiring, it shines.
With all respect to notoriously famous designers, we should identify snake oil in their statements (see the quote below) and ignore them if misleading.
They say we should "listen to the Sound" just to distract us from shortcomings of their products. That is the way they make money and that is why they don't want us to look at and analyze measurements. Their fanboys are even worse in a crowded audiophile echo chamber.
You have come to the same conclusion on the L12-2 as this New Zeeland man did:
The Best Amplifier of 4. Showing QI Adjust and modification. - YouTube
He also added a pot to adjust the QI starting at 5.28.
I did not order it because my transformers are 42 0 42 VAC, a little too high for the L12-2.
On the other hand I should get a couple of IRS2092 300W Class D amplifiers I bought from a seller on Ali soon, they have arrived at customs. Yes, I know the IRS2092 is very old, but I got a super deal, the amps are suitable for my transformer voltages and they come with speaker protection on the boards. I have never, knowingly, listened to Class D amplifiers so I see it as a fun/educational thing. And I should get my first Oscilloscope, a cool 2 channel thing with a 7" touchscreen, next week:
1013D USB Digital Oscilloscope TFT LCD Touching Screen Digital Tablet Oscilloscope Dual Channel 100M Bandwidth 1GS Sampling Rate|Oscilloscopes| - AliExpress
I also ordered a simple Function Generator
..and a Marantz 7 tube amp kit, an MBL6010 kit and, tube buffer amps, a small High Quality? RIIA chip amp with a Secret IC chip "better than 5532"
, 5532 buffer amps, DC DC buck converters that will create +18 -18V from 5VDC to 12VDC and many more fun things I totally agree with you Snakeoil comment, there seems to be gallons of it in the Super High End market.
I WILL build a class AB amp after I have tested the Class D amps. And all the other stuff. I just need to get 300/400W dummy loads for the amps, I totally forgot.
Last edited:
Hi Hattori,
It is indeed great to hear from you. Your decisions are just fine in my view, especially the purchase of oscilloscope which will certainly pay-of: you will be able to investigate your design decisions and to get deeper insight into electronics. Just listening is almost nothing; our ears are deceptive, we hear what we want, we see what we want but once you have a graphical presentation of what really happens with your circuit in time (sometimes in microseconds) and frequency response you will be able to understand phenomena beyond our human perception. I am a chemist and I understand importance of measuring "invisible", almost abstract quantities. Chemical quantities are invisible, but detectable and can be quantified with the use of appropriate instruments. Similarly, electrical currents are hidden from our perception but, fortunately, measurable. Instruments are the only tools we can use to understand electricity which is mostly hidden from our natural perception - especially from our ears.
Enjoy this fine hobby.
It is indeed great to hear from you. Your decisions are just fine in my view, especially the purchase of oscilloscope which will certainly pay-of: you will be able to investigate your design decisions and to get deeper insight into electronics. Just listening is almost nothing; our ears are deceptive, we hear what we want, we see what we want but once you have a graphical presentation of what really happens with your circuit in time (sometimes in microseconds) and frequency response you will be able to understand phenomena beyond our human perception. I am a chemist and I understand importance of measuring "invisible", almost abstract quantities. Chemical quantities are invisible, but detectable and can be quantified with the use of appropriate instruments. Similarly, electrical currents are hidden from our perception but, fortunately, measurable. Instruments are the only tools we can use to understand electricity which is mostly hidden from our natural perception - especially from our ears.
Enjoy this fine hobby.
Hello everyone, I will try to revive the branch. I installed a new board on one channel on the original parts (I kind of threw off a photo here), warmed up for 4 days for 6 hours at idle, the constant at the output after adjustment floats through zero +5 -5 mV. After warming up, connected to acoustics, listening and comparison with Chinese board. Listening was carried out both from a laptop through an external DAC, then from a CD player, with and without a preamplifier. Unfortunately (or fortunately) no miracle happened. Both played so that it was impossible to distinguish. After 4 hours of music, something began to appear on the new board. Mids became as if clearer, the instruments that were in the background came a little closer. It was decided to put the second one and not suffer. It's clear (not advertising) Chinese with their details did not give up without a fight.
I have the Acoustat 1+1 speakers, which the "original" 108 clone simply refuses to drive. I can understand, they have a too low impedance for the 108. Every amp I connect with them, overheats. But this one also sounds bad at any volume, worse than the Quad405 clone, far worse than the LJM L20 V9.2, that sounds very well, it only needs a big heath sink to drive my speakers (I'm working on it). I agree with you if you like its sound with your speakers. But I wouldn't like staying after a project that needs you to guess which speaker it can or cannot drive. And the blame is on the two diodes put in the base of the final pair, that you cannot remove, and on the driving current to the final pairs, which has a peak of 118mA, actually not that low if your speakers have an "easy" impedance.
The pro of this amp is that it is the only one that has no output-loop-feedback that I could find having a PCB.
It can be used as a driver for another emitter follower stage with multiple couples like I did (WHA-217). The sound, in this case, is awesome: refined and powerful, the current limit is really very high.
By the way, I like better the sound without the suggested Baxandall super pair mod, I'm going to remove the mod as soon as I have another amp ready to non leave me in silence.
The pro of this amp is that it is the only one that has no output-loop-feedback that I could find having a PCB.
It can be used as a driver for another emitter follower stage with multiple couples like I did (WHA-217). The sound, in this case, is awesome: refined and powerful, the current limit is really very high.
By the way, I like better the sound without the suggested Baxandall super pair mod, I'm going to remove the mod as soon as I have another amp ready to non leave me in silence.
The correct schematics should directly connect the drivers to the final pair, having resolved the idle bias elsewhere.
In the 108, the designer simplified the concept a lot and I really like the absence of source resistors; he decided to set the idle bias by the two 27Ohm resistors; the bigger the resistance, the lower the bias.
But the 27Ohm resistors don't allow the final pair to be driven at full power, they need to be shorted with something, depending on the trend of the driving signal: a double relay is not suitable, so here is the couple of diodes. The bad is that they generate distortion close to the transition voltage value (about 0.6V). The lower the impedance of the speakers, the less smooth the transition.
If you remove the diodes, the driving current must cross the two resistors, dropping, in this way, about 5V corresponding to a heath dissipation of about 1W, and the driving capability is totally lost.
If some want to improve, it is possible to put a resistor in series to every diode to have a smoother transition as a result. A starting value could be 1Ohm. The maximum power will be affected but the distortion is expected to decrease.
Moreover, some Schottky diodes show a Vf of 0.2V @ low current, if I were curious, I would give them a try with and without a resistor in series.
Do not touch the 27Ohm value if your bias is ok.
If you are happy with your speakers, do not change anything.
In the 108, the designer simplified the concept a lot and I really like the absence of source resistors; he decided to set the idle bias by the two 27Ohm resistors; the bigger the resistance, the lower the bias.
But the 27Ohm resistors don't allow the final pair to be driven at full power, they need to be shorted with something, depending on the trend of the driving signal: a double relay is not suitable, so here is the couple of diodes. The bad is that they generate distortion close to the transition voltage value (about 0.6V). The lower the impedance of the speakers, the less smooth the transition.
If you remove the diodes, the driving current must cross the two resistors, dropping, in this way, about 5V corresponding to a heath dissipation of about 1W, and the driving capability is totally lost.
If some want to improve, it is possible to put a resistor in series to every diode to have a smoother transition as a result. A starting value could be 1Ohm. The maximum power will be affected but the distortion is expected to decrease.
Moreover, some Schottky diodes show a Vf of 0.2V @ low current, if I were curious, I would give them a try with and without a resistor in series.
Do not touch the 27Ohm value if your bias is ok.
If you are happy with your speakers, do not change anything.
Hello all,
I'll try to summarise what I've read:
In the low power range the NHB-108 can convince, and according to the calculation on the behaviour of the diodes, they are there to complement the uneven distortion of expensive speakers at higher levels. Without diodes, the power amplifier would be constructed almost as described by Mr. C. Lachinjan (you can read about it in the Russian magazine "Radio" from 2001 no. 4 page 13 - 15). Therefore, it may make sense to leave out the diodes. The acoustic effect has not yet been described here in the forum - at least I have not read it.
The unbalanced performance of the amplifier is largely due to the input circuit, which is obviously based on an amplifier layout by Mr. Studer. Against this, it helps to use other low-power transistors, which have the same current amplification as PNP as well as NPN. For this I suggest the types: ZTX458 and ZTX558. I have just received and measured these. Relative to the 2N5401 and 2N5551 I have compared from 5 different manufacturers, the Diotec transistors are a dream. The behaviour is very linear and the amplification factor of both types is hFE 200.
Then, for amplifier stage two, there is the recommendation to adjust the resistors a bit, with the aim that this stage produces less distortion. I also want to take this into account in my planned set-up.
In my opinion, the ON MJE1503x transistors are unsuitable, and so far I have not been able to use them in amplifiers because the discrepancy between NPN and PNP is very large. It is also clear that kit transistors are not always the first choice. The ones I got from China are completely unsuitable for amplifier circuits because of their characteristic curves. I can still use the old Toshiba 2SA... but since they have been discontinued, I have ordered TTA006 and TTC011. The TTC011 have ideal linear behaviour with hFE of 165 on average, the TTA006 do not show such linear measurement results, but also no strongly increasing behaviour. The average gain is hFE 195.
The servo circuit offered with the NHB-108 is, in my opinion, a fake, as it regulates the DC offset but has no capabilities whatsoever, as Valery describes with the ODNF circuit. I see potential here to build a correction into the signal through an adapted version of an ODNF. Probably the amplifier will then start to produce high distortion in the range beyond 100 kHz, but this is not interesting for the audio range. On the other hand, it is also likely to further increase the fine detail without losing the transparency of the circuit, but this remains to be tested.
Finally, regarding the input capacitor: the two Wima MKS, which are found on the Chinese models, contradict the claim of highest fine detail and neutrality in the sound.
I'll try to summarise what I've read:
In the low power range the NHB-108 can convince, and according to the calculation on the behaviour of the diodes, they are there to complement the uneven distortion of expensive speakers at higher levels. Without diodes, the power amplifier would be constructed almost as described by Mr. C. Lachinjan (you can read about it in the Russian magazine "Radio" from 2001 no. 4 page 13 - 15). Therefore, it may make sense to leave out the diodes. The acoustic effect has not yet been described here in the forum - at least I have not read it.
The unbalanced performance of the amplifier is largely due to the input circuit, which is obviously based on an amplifier layout by Mr. Studer. Against this, it helps to use other low-power transistors, which have the same current amplification as PNP as well as NPN. For this I suggest the types: ZTX458 and ZTX558. I have just received and measured these. Relative to the 2N5401 and 2N5551 I have compared from 5 different manufacturers, the Diotec transistors are a dream. The behaviour is very linear and the amplification factor of both types is hFE 200.
Then, for amplifier stage two, there is the recommendation to adjust the resistors a bit, with the aim that this stage produces less distortion. I also want to take this into account in my planned set-up.
In my opinion, the ON MJE1503x transistors are unsuitable, and so far I have not been able to use them in amplifiers because the discrepancy between NPN and PNP is very large. It is also clear that kit transistors are not always the first choice. The ones I got from China are completely unsuitable for amplifier circuits because of their characteristic curves. I can still use the old Toshiba 2SA... but since they have been discontinued, I have ordered TTA006 and TTC011. The TTC011 have ideal linear behaviour with hFE of 165 on average, the TTA006 do not show such linear measurement results, but also no strongly increasing behaviour. The average gain is hFE 195.
The servo circuit offered with the NHB-108 is, in my opinion, a fake, as it regulates the DC offset but has no capabilities whatsoever, as Valery describes with the ODNF circuit. I see potential here to build a correction into the signal through an adapted version of an ODNF. Probably the amplifier will then start to produce high distortion in the range beyond 100 kHz, but this is not interesting for the audio range. On the other hand, it is also likely to further increase the fine detail without losing the transparency of the circuit, but this remains to be tested.
Finally, regarding the input capacitor: the two Wima MKS, which are found on the Chinese models, contradict the claim of highest fine detail and neutrality in the sound.