Power
If you can nominate a very cheap and safe pair of suitable fixed or adjustable AC SMPS supplies, people will try it but I would think newbs and someone with safety or EMI issues should think carefully about it. When you think about it, it ought to be no different to fitting conventional transformers but there can be nasty accidents in mishandling them and the AC connections in typical DIY fashion.
I understand that in the US, there are heaps of cheap E-I tranformers of 26-0-26V at reasonable current. Plenty of DIYs seem keen to use these and I even saw AKSA's 50W version of Fetzilla attempted with one. That gives yoU rails of about 37V DC which will be fine and that transformer looks well constructed to me.
If you can nominate a very cheap and safe pair of suitable fixed or adjustable AC SMPS supplies, people will try it but I would think newbs and someone with safety or EMI issues should think carefully about it. When you think about it, it ought to be no different to fitting conventional transformers but there can be nasty accidents in mishandling them and the AC connections in typical DIY fashion.
I understand that in the US, there are heaps of cheap E-I tranformers of 26-0-26V at reasonable current. Plenty of DIYs seem keen to use these and I even saw AKSA's 50W version of Fetzilla attempted with one. That gives yoU rails of about 37V DC which will be fine and that transformer looks well constructed to me.
Definitely - at least as far back as the NAP80 which is the oldest I worked on. They were not average transistors, which were slugs in the 1970s, with Ft below 1 MHz. These were Semelab 7MHz types, blinding fast for the day but Sankens, which came next, were much faster. Now they are back with Semelab and house-branded parts AFIK. NAP140 used both BDY58 and 2SC3858 in later versions.
Switching transistors have certainly been tried in other brands, probably because the low cost and characteristics suited the designs such as Cyrus.
Ordinarily, we look for best gain linearity now (2SC/MJL3281 etc.), regardless of speed - something switching transistors just aren't designed for.
Nigel,
I was very curious to find out who designed the Naim amp and now, thanks to you, I know his name. Thank you very much for mentioning Mr. West! I have huge respect for his work on this circuit, much much bigger than I have for JV. This is one of the very few circuits that are not over-cooked and in the same time are so well designed that most improvements would lead to a very complex new circuit or just various problems, but not better sound (in most cases).
By the way there is one thing that I can not understand in the Naim amp and that is the 22k resistor in the collector of one of the LTPs
I still have no idea what the designer compensated with this resistor. Why not 1k, for example? Was it the Early effects or hfe gain change because of the different Vce compared to the other transistor, or anything else? I'll appreciate your input. Nice to have you on this thread.
Thanks for the info....to be honest much of whats been said is over my head....i have built a few Gainclones with regulated power supplies using the 317 with good results, though the same might apply here. I am more of a tube guy but every now and then I get theitch to put together oneof these cheap kits and then try to tweak it for fun. i wish I had the time to devote to reading some of Doug Self's stuff but just dont....i realize I amout of my league very quickly when trying to follow much of the thread here.
So if a LM317 is not sufficeint for a good regulated supply for this kit,is there a straighforward schematic someone might have for a better regulated supply? Or am I getting out of my league again?
I hava a couple nice 300va toroids that will net me about 50v after rectification and was thinking of some how using these with a regulated supply...lmaybe I should just stick with unregulated around 35-37v....i also have a pair of toroids that will net this.
I am good with following schematics and direction but wouldnt know how to build from scratch one of the zener/transistor based regulators mentioned above...probably ought to stick with what I know and what is simple....
So if a LM317 is not sufficeint for a good regulated supply for this kit,is there a straighforward schematic someone might have for a better regulated supply? Or am I getting out of my league again?
I hava a couple nice 300va toroids that will net me about 50v after rectification and was thinking of some how using these with a regulated supply...lmaybe I should just stick with unregulated around 35-37v....i also have a pair of toroids that will net this.
I am good with following schematics and direction but wouldnt know how to build from scratch one of the zener/transistor based regulators mentioned above...probably ought to stick with what I know and what is simple....
Hi J M . Went out with my Pro Audio chums last night and we talked about early film sound tracks ( we also talked output tripple's as in Amcron ) . Woke up this morning and had a brain wave . I designed an amplifier whilst on holiday in Texas in 2000 , it was a fantasy of going back in time and making the NAP 160 in 1964 using parts of the time ( and not letting that spoil it in anyway ) . This story will become relevant and I think will actually produce something better than NAP 250 for peanuts .
One day the company I work for says that it has a contract to import a Chinese amplifier however the sound quality was not great .The tragedy was that 90% of the amplifier was outstanding especailly the power supplies . My boss said these guys will steel your design so don't give away anything too precious . I gave them the 1964 amp . It sounded wonderful . Alas my company got cold feet and didn't go ahead .
Now to the bit for you . The Chinese amp used regulated DC to the power amp up to the output Dalingtons . The Darlingtons were fed raw DC . Effectively the Darlingtons became both outputs and regulators in one ( I will explain that if someone asks ) . No big heat output as mostly only the idling current is important . This produces a big advantage the NAP 250 never had . This amp will soft clip . It will sound louder than a 250 whilst being safe . You will get 70 W into 8 ohms , safe unregulated about 50 . Even when at 10% distortion close to clipping it will sound nice . The output transistors usually go up to about 250V these days so ideal . Thinking about it only the big outputs need the raw DC in theory ( mark those words ) . That only means two chunky wires soldered directly to the collector of the upper transistor ( +ve ) and emitter of the lower ( - Ve ).
The regulators to the other parts of the power amp can be very simple . My D44/ 45 would be fine and probably needs no heat sink ( the 60 V versions might do at a pinch ) . You could use LM 317 ( and 337 for the other power rail ) . However that's a little more complicated . The speed isn't an issue as these stages are pure class A and have near constant current use .The capacitor on the output side will handle fast rising signals . ( maximum 33 uf if so , if not it will oscillate . if other capacitors on that rail add a series resistor ) . If you want to use a simple RC dropper and filter that will be fine also . You could use 2N3055 and 2955 if you like . Ironically a slow transistor might sound better in this rare example . Usually we use fast transistors because we can . Once in a blue moon we should question that .
I see that you guys are talking about decoupling the smaller signal stages already so somebody might like to take over and tell you how to do it . I would use one transistor and one zener , one resistor and one capacitor per power rail . $4 will cover it . One big advantage of this is that you can take chunky cable out to the current dumpers as we call them ( output Darlingtons , forgive that I call both sides Darlingtons ) Use 220 uF local decoupling to the dumpers . Don't give up on this as you will have a truly great amp . If any 1000 VA transformers of quality come up you will have a 250 destroyer .
If any on this has been discussed already apologies . However I highly endorse it if so .
One day the company I work for says that it has a contract to import a Chinese amplifier however the sound quality was not great .The tragedy was that 90% of the amplifier was outstanding especailly the power supplies . My boss said these guys will steel your design so don't give away anything too precious . I gave them the 1964 amp . It sounded wonderful . Alas my company got cold feet and didn't go ahead .
Now to the bit for you . The Chinese amp used regulated DC to the power amp up to the output Dalingtons . The Darlingtons were fed raw DC . Effectively the Darlingtons became both outputs and regulators in one ( I will explain that if someone asks ) . No big heat output as mostly only the idling current is important . This produces a big advantage the NAP 250 never had . This amp will soft clip . It will sound louder than a 250 whilst being safe . You will get 70 W into 8 ohms , safe unregulated about 50 . Even when at 10% distortion close to clipping it will sound nice . The output transistors usually go up to about 250V these days so ideal . Thinking about it only the big outputs need the raw DC in theory ( mark those words ) . That only means two chunky wires soldered directly to the collector of the upper transistor ( +ve ) and emitter of the lower ( - Ve ).
The regulators to the other parts of the power amp can be very simple . My D44/ 45 would be fine and probably needs no heat sink ( the 60 V versions might do at a pinch ) . You could use LM 317 ( and 337 for the other power rail ) . However that's a little more complicated . The speed isn't an issue as these stages are pure class A and have near constant current use .The capacitor on the output side will handle fast rising signals . ( maximum 33 uf if so , if not it will oscillate . if other capacitors on that rail add a series resistor ) . If you want to use a simple RC dropper and filter that will be fine also . You could use 2N3055 and 2955 if you like . Ironically a slow transistor might sound better in this rare example . Usually we use fast transistors because we can . Once in a blue moon we should question that .
I see that you guys are talking about decoupling the smaller signal stages already so somebody might like to take over and tell you how to do it . I would use one transistor and one zener , one resistor and one capacitor per power rail . $4 will cover it . One big advantage of this is that you can take chunky cable out to the current dumpers as we call them ( output Darlingtons , forgive that I call both sides Darlingtons ) Use 220 uF local decoupling to the dumpers . Don't give up on this as you will have a truly great amp . If any 1000 VA transformers of quality come up you will have a 250 destroyer .
If any on this has been discussed already apologies . However I highly endorse it if so .
RUWA . The 22K I will have to guess is to get a bit of second harmonic distortion into the spectrum . These guys were not as daft as some would tell you . Early effect is probably only a problem of saturation . In a regulator it is relevant and is nice to have voltage to drop . I would love to teach about LTP if anyone wants to . More nonsense is talked about it than you can imagine . Most of it by simple experiment nonsense . And people repeat this nonsense . However not all of it is nonsense .
The biggest piece of nonsense talked is amps without LTP are more stable . No they are not . The old transistors had high capacitance . There was no need for a VAS capacitor . The better choice is a very low capacitance and make the VAS cap high enough to work . The internal capacitance is non linear and needs to be swamped out . There is a theory that marginally too low a value of VAS cap is adventurous . It is right and it is wrong . There is a better way .
The Naim design is nearly bullet proof so experiments can be done even without oscilloscopes if you are sensible .
The designer of the Naim was without a doubt Mr H C Lin . Mr Gogny of France is hinting at it in 1964 .
Mr Mornington West is about as close as we will get . I personally would say JV as he said what it should do . This is a bit like the rumour that Shakespeare did not write his plays . I can not beleive anyone would be daft enough to say that unless they can do time travel .. What I say is that Shakespeare was an interesting fellow to know . Like myself he would have had very clever friends who would talk to him .He would have collected their thoughts . JV a Shakespeare ? Absolutely .
The biggest piece of nonsense talked is amps without LTP are more stable . No they are not . The old transistors had high capacitance . There was no need for a VAS capacitor . The better choice is a very low capacitance and make the VAS cap high enough to work . The internal capacitance is non linear and needs to be swamped out . There is a theory that marginally too low a value of VAS cap is adventurous . It is right and it is wrong . There is a better way .
The Naim design is nearly bullet proof so experiments can be done even without oscilloscopes if you are sensible .
The designer of the Naim was without a doubt Mr H C Lin . Mr Gogny of France is hinting at it in 1964 .
Mr Mornington West is about as close as we will get . I personally would say JV as he said what it should do . This is a bit like the rumour that Shakespeare did not write his plays . I can not beleive anyone would be daft enough to say that unless they can do time travel .. What I say is that Shakespeare was an interesting fellow to know . Like myself he would have had very clever friends who would talk to him .He would have collected their thoughts . JV a Shakespeare ? Absolutely .
BTW guys . JV has had a bad reputation or that of a guru . In my opinion although possibly by default a prophet . I only met him a few times and was more than a little intimidated by him . I never missed the opportunity to pump him for information . One day at a hi fi show he seemed to be a bit ill at ease . He walked over to me and said . I don't know these people however I know you . He then said do you think my pre amps hiss when playing music and I said no . He smiled and said that's what he thought and walked away . I developed a noise gate to put on a pre amp . I wanted some reviewer to say I had developed a preamp outside of the laws of physics ( when measured it would look great ) . Wish I had marketed it . JV made me think of it . I was once quoted as saying Nige says the best use for CD's is to hum to when vacuum cleaning . It's brilliant , I didn't say it . One thing to understand is that JV was a mechanical engineer . It is easy for engineers to swap disciplines . In the Oxford library electronics is next to Military diesels engines . I do read that sometimes and it's all the same stuff as electronics's in the maths . JV brought a mechanical engineering slant into power supply design I suppose . Doubtless like me he got others to do the work . My freind Kurt is a highly regarded designer , he and I ended up in a restaurant helping a guy with chaotic failure in locomotive engines . The solution is to squirt lubricant in sequence with the injectors under the piston crown . I said to Kurt I never knew you liked diesel engines to which he said , you never asked .
There are application notes to Google for the LM317/337T or much dearer K version. They show schematics of practical designs which add a power transistor to supply sufficient current for the amplifier. This is straightforward and will work without needing to understand how it works or how to design linear supplies, as long as you have the extra heatsinking necessary. To split the rails, you are getting into modifications to the PCB and unknown territory. As Nigel suggests, it sure can be done but is out of the scope of a simple Chinese clone assembly and into a new area probably suited to new boards, new thread and quite a bit of study to get conversant with solid-state terms and design/test principles.
It seems an awkward and expensive way to get a supply when adequate transformers are not hard to get anyway. Here, a 300VA standard range toroid from China costs $80 retail. From a local manufacturer, it will cost $100. If I ask for 1 only 28V+28V type which suits this clone, the price is the same (it's a popular size here with DIYs). For interest, AU$ is roughly US$ at the moment. I think the 26-0-26V transformer will be much cheaper still.
ZENER REGULATOR
Note 39 V is a convenient zener value . The bottom regulator is like the top with zener reversed and different PNP transistor . I calculate 20 mA as zener current . If your PSU is higher or lower recalculate R to pass 20 mA .
Notice the power transistor and drivers are 50 V and the other 38 V . Check drivers and outputs to be about 100 V minimum .
Some power transistors have built in protection diodes , A good choice and in the data sheets . I haven't calculated the exact current and said 50 mA as more than enough . I see no need for a heat sink . Use D 44 / 45 as a reference transistor ( TO 220 ) .
Note 39 V is a convenient zener value . The bottom regulator is like the top with zener reversed and different PNP transistor . I calculate 20 mA as zener current . If your PSU is higher or lower recalculate R to pass 20 mA .
Notice the power transistor and drivers are 50 V and the other 38 V . Check drivers and outputs to be about 100 V minimum .
Some power transistors have built in protection diodes , A good choice and in the data sheets . I haven't calculated the exact current and said 50 mA as more than enough . I see no need for a heat sink . Use D 44 / 45 as a reference transistor ( TO 220 ) .
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See t/f if in UK
http://cpc.farnell.com/multicomp/mc.../dp/FF01589?in_merch=Products From This Range
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Here is a curly question about NAIM preamps -early ones which had no clear model number, but were quite shallow in the case and sported largish plain knobs. Now, who was the clown who specified a DIL reed relay as the mute switch?
When the preamp was placed on hard surfaces such as a table, glass shelf etc. the audio would change from wonderful to old 78 record player in a flash, due to acoustic feedback so I do mean clown, for lack of testing. It was amusing, when some years later, the manufacturer and the UK hi-fi toy industry generally, began to promote Aerolam table tops, coned feet and special isolating shelving for every bit of kit. 'Not funny really, at the prices asked.
That's very interesting Ian . I had a NAC 12 which by then didn't have that .
If you ever get smooth box NAC 12 and NAP 160 together they have a magical sound . I don't find them as good used with other Naim bits . For example swap to NAC 42 . The other Naim products are not affected by this including later NAP 160 .
My noise gate used a comparator and a simple relay also ( shunt ) . It was very reliable and apart from the click it was difficult to detect .
The guy in Australia I seem to remember was Warren Stolmark or something doing Naim . My freind Martin Renwick wanted to do it . He would have been great .
I have a Linn pre amp somewhere , it was made by Naim .
If you ever want to talk 78's I'm very interested ( or ancient stuff ) . Not on this forum .
If you ever get smooth box NAC 12 and NAP 160 together they have a magical sound . I don't find them as good used with other Naim bits . For example swap to NAC 42 . The other Naim products are not affected by this including later NAP 160 .
My noise gate used a comparator and a simple relay also ( shunt ) . It was very reliable and apart from the click it was difficult to detect .
The guy in Australia I seem to remember was Warren Stolmark or something doing Naim . My freind Martin Renwick wanted to do it . He would have been great .
I have a Linn pre amp somewhere , it was made by Naim .
If you ever want to talk 78's I'm very interested ( or ancient stuff ) . Not on this forum .
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Thanks for that experience. I do wonder because of the secretive Naim policy about even its early IP, or any avenue for criticism. It's easy to read a NAC 42 from the cloner's Ebay sites but I imagine the preamp circuits change a lot with time and market needs. The schematic and PCB only describe the main line-level amplifier which may have sat before the volume control so it is difficult guessing what you really have and how much you don't when you pay for these.clones.
Any comments on topology changes would be priceless.
Ian . I will be honest with you and say I am not the worlds greatest fan of the pre-amps . Although they are super competent designs . The Martin Renwick I refer to introduced me to DNM pre amps of the 1985 vintage which I preferred used with NAP 250 . I think he was importer for Australia of DNM .
I did draw the pre amps years ago and have lost them . Do you guys insist on using tantalum caps like Naim did ( do ? ) .
One tip with NAC 32.5 and similar . Leave the screws slightly loose into the feet . That was discovered by accident and makes the pre amp less microphonic .
Sorry to hog the thread every one . .
It must be 1.40 in Aus , hope I'm not keeping you up ?
Just had another look . Nice simple distortion cancelling design , some of this I remember now . I tried to find the Stan Curtice stuff on this ( he designed Rotel RA 820 ) . Perhaps with better components it could come alive . The power supply doesn't look right although doubtless good .
I did draw the pre amps years ago and have lost them . Do you guys insist on using tantalum caps like Naim did ( do ? ) .
One tip with NAC 32.5 and similar . Leave the screws slightly loose into the feet . That was discovered by accident and makes the pre amp less microphonic .
Sorry to hog the thread every one . .
It must be 1.40 in Aus , hope I'm not keeping you up ?
Just had another look . Nice simple distortion cancelling design , some of this I remember now . I tried to find the Stan Curtice stuff on this ( he designed Rotel RA 820 ) . Perhaps with better components it could come alive . The power supply doesn't look right although doubtless good .
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Not at all (only 11.40 ) - Warren Stolmack, I recall as a name only, Martin, no but we have >800km between the
largest cities and it's possible the agent operated from Melbourne as now - since it's the bastion of stereo hi-fi here.
Thanks for the comment -'would like to explore that and the DNM matter at some other time.
P.S. Member ljm-ljm produced that schematic and board so we can't say where in the PSU Naim started or finished.
Perhaps he will post.
) - Warren Stolmack, I recall as a name only, Martin, no but we have >800km between thelargest cities and it's possible the agent operated from Melbourne as now - since it's the bastion of stereo hi-fi here.
Thanks for the comment -'would like to explore that and the DNM matter at some other time.
P.S. Member ljm-ljm produced that schematic and board so we can't say where in the PSU Naim started or finished.
Perhaps he will post.
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Diode noise
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Ian , I am very mindful of keeping things cheap . One of the debates raging in audio is what type of power supply rectifier diodes to use . Naim would have used simple big versions of what I show here in a 35 amp bridge rectifier .
Regulations came in some years ago to suppress the diode noise . The simple 10 nF I show across each of the 4 diodes is what the testing house recommended .
Many say this ruins the sound ( me ) . The 470R and 3n9 ceramic is an attempt to please everyone . In theory it should be better . Carbon composition resistors are best and solder close to the diodes ( difficult ) .
The last example with 10nF 110R and 68 nF is supposed to be the best .
Unfortunately this solution was for a particular transformer . However it must be better than nothing .
I am research this at the moment so would love any feedback . The little neon bulb idea is just a bit of fun . The dotted resistor for
valves .
People pay money for mains conditioning equipment only to have a nasty little radio transmitter inside the amplifier , the rectifier diodes .
Some use fast / soft recovery diodes without suppression .
Ian , I am very mindful of keeping things cheap . One of the debates raging in audio is what type of power supply rectifier diodes to use . Naim would have used simple big versions of what I show here in a 35 amp bridge rectifier .
Regulations came in some years ago to suppress the diode noise . The simple 10 nF I show across each of the 4 diodes is what the testing house recommended .
Many say this ruins the sound ( me ) . The 470R and 3n9 ceramic is an attempt to please everyone . In theory it should be better . Carbon composition resistors are best and solder close to the diodes ( difficult ) .
The last example with 10nF 110R and 68 nF is supposed to be the best .
Unfortunately this solution was for a particular transformer . However it must be better than nothing .
I am research this at the moment so would love any feedback . The little neon bulb idea is just a bit of fun . The dotted resistor for
valves .
People pay money for mains conditioning equipment only to have a nasty little radio transmitter inside the amplifier , the rectifier diodes .
Some use fast / soft recovery diodes without suppression .
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Hi Salas . That's the question I had hoped for ! I suspect 470 R and 470 pF is about right for an ultra fast diode . I think the diode is BYV 28 200 I am playing with . What I suspect is that we can come up with a generic value which reasonably ignores transformer leakage inductance and capacitance . I want to keep away from a mathematical discussion as I feel this can be arrived at empirically and would be fun for the penniless to pursue . Note I stress carbon composition resistors and ceramic capacitors ( NPO / GOG ) . That's about 720 kHz and a sensible rise time . What should be noticed is better HF clarity . BYV 28 200 is a bit small for a power amp I should point out ( probably just about OK , cheap and very good ) .