On a completely different matter to the unstable amp, I think we need to consider safety with the unshielded SMPS sitting loose apparently, there in the above pic.
It may be an acceptable risk for Atupi to work with exposed high voltages on a loose board and I'm not criticizing his efforts alone but others should not assume that it will be safe for them. Increasing numbers of newbies or everyday DIY folk also find SMPS cheaper and easier to fit than linear power supplies. It is inevitable though, that there will be increasing numbers of shocks and deaths associated with unrestricted use of these open, unshielded types.
With high current 230VAC and 380VDC contact, shock isn't just a tingle, jolt or lost moment in time. We can wind up unconscious and injured on the floor, maybe requiring urgent CPR or just plain dead 😱
Please, don't take this as trivial just because many people now work like this with unenclosed, possibly unsafe supplies. Whether installed correctly in the case or used experimentally, supplies should be fixed securely and have fully isolated mains and rectified mains voltages that are completely enclosed and protected from objects like tools, solder, wires, fingers, elbows, foodstuffs etc contacting them.
Sure, your safety is not the responsibility of DIYaudio or members like me posting here but be warned that using unsecured, uncovered SMPS boards is flirting with death.
It may be an acceptable risk for Atupi to work with exposed high voltages on a loose board and I'm not criticizing his efforts alone but others should not assume that it will be safe for them. Increasing numbers of newbies or everyday DIY folk also find SMPS cheaper and easier to fit than linear power supplies. It is inevitable though, that there will be increasing numbers of shocks and deaths associated with unrestricted use of these open, unshielded types.
With high current 230VAC and 380VDC contact, shock isn't just a tingle, jolt or lost moment in time. We can wind up unconscious and injured on the floor, maybe requiring urgent CPR or just plain dead 😱
Please, don't take this as trivial just because many people now work like this with unenclosed, possibly unsafe supplies. Whether installed correctly in the case or used experimentally, supplies should be fixed securely and have fully isolated mains and rectified mains voltages that are completely enclosed and protected from objects like tools, solder, wires, fingers, elbows, foodstuffs etc contacting them.
Sure, your safety is not the responsibility of DIYaudio or members like me posting here but be warned that using unsecured, uncovered SMPS boards is flirting with death.
Bob Stewart told Mr Vereker to study and improve a Sinclair Z30. A&R also was Bobs help. The A&R is one of the more complicated British amps. If you strip off the protection and current sources it is much like the Z30. The way I rememeber the A60 working is the current source was near the heat sink. Thus the bias resistor ( R50 220 R and R11 Z30 ) does change the bias. If I remember it was at least as good as the majority of Vbe multiplier circuits as the Naim has. Thought the story needed this extra piece. I listened to a A60 I repaired years ago yesterday. What a beautiful amp. The repair done about 1995, yesterday was it's first use!
The kiit amp having oscillation problems is bad news. The Naim circuit is not really one that should. VAS cap might be wrong. Try 100 pf to see if it helps.
Ian. The SMPS issue is stangely true of the Hypex also ! Hypex say use 6 mm clearance as the only warning. I was mostly unimpressed by the Hypex SMPS which must be as good as is easy to buy. I managed to make a linear PSU for less money that was free of all the RF problems. The 600 watts of the Hypex SMPS and doubtless very low impedance was impressive. I had a fight to beat that aspect. As the Hypex amplifier has output filtering the RF from the PSU may not be a big problem, the Naim will not be so happy. The Hypex SMPS has extra outputs for preamps. These were too dirty in my opinion to be useful. The TL431 + Darlington I show is not quite as good as a LM317. Both are about 4 to 6 dB above the noise of the test rig.
I listened yesterday for few good hours on my amp and i must say i like it so far and i undesrtand i can expect more as i use some caps not so good for audio like the 470pf ceramic.
@Ruwe: i dont have any tantalum caps, those are Vishay Bc128 aluminium
@Ian: thanks for pointing on personal security when using SMPS. I like to say that i know what i'm doing, maybe sometimes my questions sounds like from a beginner but i'm soldering since 30 years already and i have an electronics degree.
After i decide on a final choice on parts and design i intend to redesign the pcb.
Of course i will test a classic power source when i can get a 30v+30v transformer.
So far i like the dinamics of this amp and the way how bring the voices in your attention.
@Ruwe: i dont have any tantalum caps, those are Vishay Bc128 aluminium
@Ian: thanks for pointing on personal security when using SMPS. I like to say that i know what i'm doing, maybe sometimes my questions sounds like from a beginner but i'm soldering since 30 years already and i have an electronics degree.
After i decide on a final choice on parts and design i intend to redesign the pcb.
Of course i will test a classic power source when i can get a 30v+30v transformer.
So far i like the dinamics of this amp and the way how bring the voices in your attention.
Forgot to answer to @Ruwe: my zobel resistor is lower than 3 W i suppose, i suspect 1W but i will change them.
Many here praise SMPS of various brands, including the much cheaper Chinese products. Most are at least shrouded with sheet and/or perforated metal. The open board types are cheaper and more attractive again but they are really only an industrial sub-assembly for inclusion in products where shielding and insulation measures will be applied to meet EMC and safety standards. IMV, to simply use the board as it comes is plain unsafe anywhere and certainly dangerous in general DIY application.
I'm just raising a serious concern for the safety of our unwary DIY guys.
I'm just raising a serious concern for the safety of our unwary DIY guys.
A 600mW Zobel resistor will survive 10kHz sinewave testing to full power.
But may not survive 20kHz square wave testing and if it blows you may end up with an amp that oscillates into destruction.
It is only High Frequency testing that requires big Zobel ratings.
I'm sorry. You mentioned BC128 before, but I presumed tantalum based on looks. Very nice capacitors, by the way, with low impedance up to very high frequencies. I doubt other electrolyte caps would do better. Oscons are also very good in similar applications.
The orientation of the feedback capacitor in the circuit can be changed later, when the DC offset is known. So, even the slightest reverse polarization can be avoided. Only in case of polarised cap use, of course.
What is your final conclusion on the oscillation?
The orientation of the feedback capacitor in the circuit can be changed later, when the DC offset is known. So, even the slightest reverse polarization can be avoided. Only in case of polarised cap use, of course.
What is your final conclusion on the oscillation?
Well, i don't have a scope and i'm not 100% sure but i had some very pleasant listening sesions yesterday and today.
The single situation when my zobel resistor went hot and smoked a little was when touched the input cap. Also i see there is a 3W recommendation for zobel resistor.
Also bias seems stable and DC out is around 10-15 mV
When music is paused almost no noise.
I really like the dinamics of this amp but i need to work a little on transparency (maybe using better passives) and also a delayed speaker module as i have a loud "plop" sound when power up.
The single situation when my zobel resistor went hot and smoked a little was when touched the input cap. Also i see there is a 3W recommendation for zobel resistor.
Also bias seems stable and DC out is around 10-15 mV
When music is paused almost no noise.
I really like the dinamics of this amp but i need to work a little on transparency (maybe using better passives) and also a delayed speaker module as i have a loud "plop" sound when power up.
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You can play a little bit with the ground wiring. The amplifier should be dead quiet when idle, no hum whatsoever.
As for the transparency I'm not sure that it can be improved too much. That's exactly my observation - nice stereo and dynamics, but a little bit flat as stage and a little bit dark sounding. "Flat Earth" indeed 😉
Try to test different type of capacitors, hock up wire can make some difference
I use the same transistor set and I'm very pleased with the sound..
If the kit is anything like the real Naim amps the Quad ESL 57 speaker completely changes the mildly dry/sterile sound and gives vast depth. I can only conclude the fine tuning of the amp is to favour the ESL. If this is true it supports Martin Colloms suggestion that the outside world gets into amplifiers more than we imagine. If so 16 turns of 1 mm enamelled copper on a 8 mm drill might help as an output inductor. I doubt it could change the amp for the worse if not owning typical Naim favoured speakers. Worth a thought.
Don't change the VAS ceramic cap. These are usually NPO or GOG. These have the best sound of any capacitor if wanting to say it that way. Use them as devices of first choice up to 10 nF. They must be COG or NPO. They are also much safer devices. Never use polystyrene as they will give up in time. The Philips ones were made of lead foil to help prevent this.
Don't change the VAS ceramic cap. These are usually NPO or GOG. These have the best sound of any capacitor if wanting to say it that way. Use them as devices of first choice up to 10 nF. They must be COG or NPO. They are also much safer devices. Never use polystyrene as they will give up in time. The Philips ones were made of lead foil to help prevent this.
For sure i keep de 47pf silver-mica cap in VAS. I used ceramics also for 220pf and 470pf and i don't think is a good idea but this was available in my parts box for the moment.
My 002CCN amp does not sound at all dry and sterile, I would describe it as a touch dark and fruity.
Swapping the output L//10R for Naim style 0.22R made it sound boomy in the bass. I am rather surprised by this, especially as my main speakers (driven my this amp) are rolled off by electronic crossover below 120Hz. I was also surprised by the magnitude of the audible effect of the 0.22R output resistor.
I think that is a mordern version that I have never heard. It's a bit like saying the the new VW Beetle handles better than the old one which is because it's mostly a Golf in the shape of the old Bettle. Does anyone have the 002CCN circuit ?
The dry and sterile sound is most likely the tantalum caps.
NPO/COG by reputation equal silver mica. Silver mica is the old world prefered choice for tuned circuits. NPO/COG 470 pF will be supurb. Read below.
MCRR25471COGJ0100 - UNBRANDED - Multilayer Ceramic Capacitor, 470 pF, C0G / NP0, 100 VDC | CPC UK
Pro Audio Design Forum • View topic - Cyril Bateman Capacitor Sound Archive
The dry and sterile sound is most likely the tantalum caps.
NPO/COG by reputation equal silver mica. Silver mica is the old world prefered choice for tuned circuits. NPO/COG 470 pF will be supurb. Read below.
MCRR25471COGJ0100 - UNBRANDED - Multilayer Ceramic Capacitor, 470 pF, C0G / NP0, 100 VDC | CPC UK
Pro Audio Design Forum • View topic - Cyril Bateman Capacitor Sound Archive
I think i have some 39pf ceramics good quality at home but don't know what dielectric they are.
I will put some pictures later.
For 470pf position received some recommendation for Wima Polycarbonate: http://www.ebay.de/itm/271276734136
I will put some pictures later.
For 470pf position received some recommendation for Wima Polycarbonate: http://www.ebay.de/itm/271276734136
NP0/C0G should have a thin black stripe at the top of the package.
No stripe should mean it is HiK and these are very different animals.
Do Wima still make MKC (polycarbonate) capacitors?
What are the two letters at the lead out end?
No stripe should mean it is HiK and these are very different animals.
Do Wima still make MKC (polycarbonate) capacitors?
What are the two letters at the lead out end?
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Hi
I would love to se the 002CCN circuit to if someone has it ...
The dry and sterile sound is most likely the tantalum caps.
I agree with these possibility, I tested several type of tantalum including vet type and dry ERO plastic case
Silver mica is pricy but worth the investment to be tested in these case for 47pF... To me that is the best there
Ooops sorry for the confusion chaps...
In post #1494 I mentioned my "upside down" NCC200 which I jokingly (yes, feeble I know
) called an 005CCN:
"FWIW I have built an "005CCN" which is the same topology except the "other way up" i.e. the IPS uses PNPs and the VAS is an NPN (MJE340). The OPS is a standard complementary double. The layout is completely different to the NCC200. I have included some of the Naim tweaks though, because I want to try to figure out which tweaks provide which sonic flavour. Its interesting to note how differently this biases up, I think the ZTXs (not used in this amp) have some rather unusual characteristics"
I then misquoted myself and turned it into an 002CCN 😱
The odd thing is that this is a lash up of similar to the front end of an NCC200 amp (the other way up) and the back end of a DX amp, and I have not felt any compulsion to switch back to the NCC during listening.
In post #1494 I mentioned my "upside down" NCC200 which I jokingly (yes, feeble I know
) called an 005CCN:"FWIW I have built an "005CCN" which is the same topology except the "other way up" i.e. the IPS uses PNPs and the VAS is an NPN (MJE340). The OPS is a standard complementary double. The layout is completely different to the NCC200. I have included some of the Naim tweaks though, because I want to try to figure out which tweaks provide which sonic flavour. Its interesting to note how differently this biases up, I think the ZTXs (not used in this amp) have some rather unusual characteristics"
I then misquoted myself and turned it into an 002CCN 😱
The odd thing is that this is a lash up of similar to the front end of an NCC200 amp (the other way up) and the back end of a DX amp, and I have not felt any compulsion to switch back to the NCC during listening.
1. Found today that 68uf elcap has a very important influence in sound signature:
a.Panasonic SEPC polimer i think: very boomy bass and a bit shouting trebles
b.Panasonic FC 68uf: oposite to SEPC very thin voice, flat sound
c. Nichicon Muse 100uf i like it for the moment more pleasant bass, mids, treble distribution, voices has body again.
What is the role of this cap?
2. I remember user @Rensli said some long time ago not to use high hfe transistor in TR3 position (CCS) if using MJE243/253 predrivers (post#1402).
Any clue why is that ?
I'm planing to test some MJE243/253 instead of 15034/15034 that are installed now.
This is a crazy amp (in a good way), so simple and so different sound regarding different parts choice.
a.Panasonic SEPC polimer i think: very boomy bass and a bit shouting trebles
b.Panasonic FC 68uf: oposite to SEPC very thin voice, flat sound
c. Nichicon Muse 100uf i like it for the moment more pleasant bass, mids, treble distribution, voices has body again.
What is the role of this cap?
2. I remember user @Rensli said some long time ago not to use high hfe transistor in TR3 position (CCS) if using MJE243/253 predrivers (post#1402).
Any clue why is that ?
I'm planing to test some MJE243/253 instead of 15034/15034 that are installed now.
This is a crazy amp (in a good way), so simple and so different sound regarding different parts choice.