Jazper
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- Dec 2, 2004
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Well I started with the idea of building a cmoy for my girlfriend about 3-4 weeks ago, then went on to decide that she should get something a bit better, and that I should use the opportunity to upgrade what I have.
So, I decided (after a week of tossing together options, and pondering over making her an A47 and such) that I'd build an M3.
The M3 has become something of an obsession, the amount of work I've put into it is rediculous at this point and people have begun to ask me what I'm doing/how I'm doing it/what components I use etc etc etc.. so that's what this thread is going to be about. I don't promise that it'll be interesting, but it'll be factual.
The power supply:
I started out trying to make a basic m3, was going to buy a STEPS with it to begin with, then after long winded conversations on msn with Dakiller we came upon this design:
http://www.diyaudio.com/forums/showt...threadid=56106
I bought a 20VA toroidal from the local electronics store and the necessary parts
I made some substitutions on the parts (LM317, 5500uF Low ESR caps, LED/Resistor -10k on the output, 5w bleeder - wire wound resistor rather than 2w metal film) and used 1w ceramic resistors. I also only used half of the design. When building it I just built it on plain perfboard (just copper circles around small holes)
Lesson 1 : always check your resistor values - when I first powered up I got 33.5v which was way too high, I was aiming for 28.15-28.6v (yes, it needs to be that precise - I'll tell you why later), needless to say much resoldering and calculations later I managed to get about what I wanted, after I put some load on the end of it.
When this worked ok I left it and began speccing out parts for the M3.
All up this cost about $25AUD (without the transformer)
This was about the time I decided ok I want something that is somewhat unique.
The m3, part 1:
First step I made was to decide on the elec capacitors on the m3, I looked at cerafines, nichicon muse, black gates, panasonic fc, and even just plain old nichicon Low ESR. After much pondering and thought I decided that the best value for money overall is the SILMIC IIs in terms of having something that is both boutique and something that most people don't use. You always hear about people using cerafines or black gates, but never SILMICs..
The crucial part here was money, or lack of it, I'm a student who works on and off, so every cent counts, or counted at this point, so I asked amb about using 35v caps throughout the M3, after getting the ok, I ordered them all from http://www.audio-cube.nl/elna.htm
From there I just got the excel file from amb's website and started going through all the EXTRA parts I needed (listing them in the excel file.)
I should mention that I'm quite happy with the choices made in the excel file regarding parts from mouser - all are high quality and the only modifications I've made so far are the alu caps and I'm thinking about possibly changing the polyester caps for polypropylene however I'm not keen on having things off board and doubt having them will make much difference.
At the onset I'd decided I wanted to use as much power as I could get into the amp, I plan to run 28v with relatively high quinescent current on the mosfets (well as per the settings on amb's page). The reason for this is so I can drive most anything from the amp without issue. 28.5 is the key voltage because I wasn't sure whether or not I wanted to roll opamps, I know that I like the opa series chips (637/627) but I might like to roll some AD8610s sometime. In the big M3 construction thread amb states that the voltage drop across the m3 is 2v, so 28.5v puts this at 26.5v just under the max rating(27v) for the AD8610s
This is about the time I started looking at cases
Cases/enclosures:
I was looking for something that was about 200mm x 300mm for about say 5 days straight, but have still come up short. Hammond have something but it cost a fortune to get shipped over here and looked a bit foul, everyone keeps saying put it in a 1u rackmount... anyhow I haven't settled on a case yet, getting anything from par-metal detracts from the exclusivity of this particular M3 so I'll probably look at something more unique, perhaps part wooden, perhaps not, I know I'll have to shield the case if I use wood. Then again if I could find something half decent that wasn't huge I'd be happy.
The only requirement is that it somewhat fit on the top of my computer case, for convenience reasons.
The power supply, take 2
After much deliberation and talking with family members I came to the conclusion that I should look at doing something different, nay special with this M3, so that I might sell it for a higher price later (if I ever wanted to sell it... )
So I started looking into different things I could do to improve the m3's design, I toyed with removing the rail splitter and having a dual rail power supply, using uber boutique resistors (with 0.001% ratings) and other ideas before I came upon (again on heavy consultation with Dakiller) that the best way to improve the design, and see a net gain in quality would be to move away from the whole lm317 power supply design and go with something better, the modified jung super regulator.
At this point I was sick of messing with protoboard, I wanted something that worked and was laid out on a nice pcb, I found one particular type that was on the diy audio forums that was a possible but they were out of stock so I decided to look at what our resident expert in SMD here (Peranders) had in stock.
Dakiller warned me that it'd cost a lot to get a board from him, but I persisted, I like P-A's designs. I settled on his JSR03 design( http://home.swipnet.se/~w-50719/hifi/jsr03/index.html ), inquired, bought and then started talking to him about parts. (More info here: http://www.sjostromaudio.com/phpBB2/viewtopic.php?t=14 - note I use the nick Keljian over there)
A few of the parts were obsolete and needed replacements, and some weren't able to be sourced easily, also I wanted to run higher voltage than the JSR03 components can handle (stock) so a few modifications were necessary (notibly alu capacitor voltage ratings - see bom)
After using his forums I've substituted quite a few parts for parts available at mouser, but the notible ones are the RN60D vishay dale resistors, the vishay/Roederstein polypropylene capacitors, and the transistors (as some were unavailable). The polyprop cap leads may need to be bent a bit to fit but being axial leaded they are easier to fit than the square brick wima caps which would have to be off board.
(note R8, r9 and r7 are 2k15, 681R and 511R respectively to get just over 28v)
The voltage reference given in P-A's stock part list is LM431, he says the LM329 is better, so based on that, that's what I'm going to use.
Now P-A's design is beautiful, but it doesn't include a bridge rectifier or smoothing caps, My default choice for caps is nichicon UPW, but it turns out that panasonic FM are cheaper and I'll be ordering from digikey anyhow so they'll be what I use. I'll put these together with the rectifiers on protoboard. 6x1000uF 50v
I've chosen panasonic FM for a few reasons, the main one is that the price is right(less than nichicon), but also the impendance is lower than the Nichicon UPW. I'm hoping that C4 and C12 on P-A's design can be 150uF (as panasonic FMs don't come in 100uF from digikey, and yeah I could use FC instead but I'd rather not as the impendance is much lower on the FM)
As for rectifier diodes, diyaudio people seem to like the MUR820, which is overkill but cheap enough to use, so I plan to use a reasonable clone of it.
I've also added good hookup wire and silver solder to the list of things to buy because I figure why not go the extra mile when I'm going that far with everything else?
As of today (14-6-05) I haven't made the final order from mouser or digikey, but I've bought everything I need from amb, audio-cube, and peranders. Barring final changes, I may make the huge order tomorrow or the day after.
Anyhow, I'll leave it there for now and keep this thread updated.
The bom I'm working from is attached to this message, it is a bit messy (will tidy it up later), but yeah it's all there, hours and hours and hours and hours of work worth of it. The equations on the second page are for the resistor calculations.
Any questions, I'll do my best to answer.
PS. Thankyou everyone who's helped so far especially P-A and my girlfriend for their patience and Dakiller for all of his valuable advice, much appreciated.
Jaz
So, I decided (after a week of tossing together options, and pondering over making her an A47 and such) that I'd build an M3.
The M3 has become something of an obsession, the amount of work I've put into it is rediculous at this point and people have begun to ask me what I'm doing/how I'm doing it/what components I use etc etc etc.. so that's what this thread is going to be about. I don't promise that it'll be interesting, but it'll be factual.
The power supply:
I started out trying to make a basic m3, was going to buy a STEPS with it to begin with, then after long winded conversations on msn with Dakiller we came upon this design:
http://www.diyaudio.com/forums/showt...threadid=56106
I bought a 20VA toroidal from the local electronics store and the necessary parts
I made some substitutions on the parts (LM317, 5500uF Low ESR caps, LED/Resistor -10k on the output, 5w bleeder - wire wound resistor rather than 2w metal film) and used 1w ceramic resistors. I also only used half of the design. When building it I just built it on plain perfboard (just copper circles around small holes)
Lesson 1 : always check your resistor values - when I first powered up I got 33.5v which was way too high, I was aiming for 28.15-28.6v (yes, it needs to be that precise - I'll tell you why later), needless to say much resoldering and calculations later I managed to get about what I wanted, after I put some load on the end of it.
When this worked ok I left it and began speccing out parts for the M3.
All up this cost about $25AUD (without the transformer)
This was about the time I decided ok I want something that is somewhat unique.
The m3, part 1:
First step I made was to decide on the elec capacitors on the m3, I looked at cerafines, nichicon muse, black gates, panasonic fc, and even just plain old nichicon Low ESR. After much pondering and thought I decided that the best value for money overall is the SILMIC IIs in terms of having something that is both boutique and something that most people don't use. You always hear about people using cerafines or black gates, but never SILMICs..
The crucial part here was money, or lack of it, I'm a student who works on and off, so every cent counts, or counted at this point, so I asked amb about using 35v caps throughout the M3, after getting the ok, I ordered them all from http://www.audio-cube.nl/elna.htm
From there I just got the excel file from amb's website and started going through all the EXTRA parts I needed (listing them in the excel file.)
I should mention that I'm quite happy with the choices made in the excel file regarding parts from mouser - all are high quality and the only modifications I've made so far are the alu caps and I'm thinking about possibly changing the polyester caps for polypropylene however I'm not keen on having things off board and doubt having them will make much difference.
At the onset I'd decided I wanted to use as much power as I could get into the amp, I plan to run 28v with relatively high quinescent current on the mosfets (well as per the settings on amb's page). The reason for this is so I can drive most anything from the amp without issue. 28.5 is the key voltage because I wasn't sure whether or not I wanted to roll opamps, I know that I like the opa series chips (637/627) but I might like to roll some AD8610s sometime. In the big M3 construction thread amb states that the voltage drop across the m3 is 2v, so 28.5v puts this at 26.5v just under the max rating(27v) for the AD8610s
This is about the time I started looking at cases
Cases/enclosures:
I was looking for something that was about 200mm x 300mm for about say 5 days straight, but have still come up short. Hammond have something but it cost a fortune to get shipped over here and looked a bit foul, everyone keeps saying put it in a 1u rackmount... anyhow I haven't settled on a case yet, getting anything from par-metal detracts from the exclusivity of this particular M3 so I'll probably look at something more unique, perhaps part wooden, perhaps not, I know I'll have to shield the case if I use wood. Then again if I could find something half decent that wasn't huge I'd be happy.
The only requirement is that it somewhat fit on the top of my computer case, for convenience reasons.
The power supply, take 2
After much deliberation and talking with family members I came to the conclusion that I should look at doing something different, nay special with this M3, so that I might sell it for a higher price later (if I ever wanted to sell it... )
So I started looking into different things I could do to improve the m3's design, I toyed with removing the rail splitter and having a dual rail power supply, using uber boutique resistors (with 0.001% ratings) and other ideas before I came upon (again on heavy consultation with Dakiller) that the best way to improve the design, and see a net gain in quality would be to move away from the whole lm317 power supply design and go with something better, the modified jung super regulator.
At this point I was sick of messing with protoboard, I wanted something that worked and was laid out on a nice pcb, I found one particular type that was on the diy audio forums that was a possible but they were out of stock so I decided to look at what our resident expert in SMD here (Peranders) had in stock.
Dakiller warned me that it'd cost a lot to get a board from him, but I persisted, I like P-A's designs. I settled on his JSR03 design( http://home.swipnet.se/~w-50719/hifi/jsr03/index.html ), inquired, bought and then started talking to him about parts. (More info here: http://www.sjostromaudio.com/phpBB2/viewtopic.php?t=14 - note I use the nick Keljian over there)
A few of the parts were obsolete and needed replacements, and some weren't able to be sourced easily, also I wanted to run higher voltage than the JSR03 components can handle (stock) so a few modifications were necessary (notibly alu capacitor voltage ratings - see bom)
After using his forums I've substituted quite a few parts for parts available at mouser, but the notible ones are the RN60D vishay dale resistors, the vishay/Roederstein polypropylene capacitors, and the transistors (as some were unavailable). The polyprop cap leads may need to be bent a bit to fit but being axial leaded they are easier to fit than the square brick wima caps which would have to be off board.
(note R8, r9 and r7 are 2k15, 681R and 511R respectively to get just over 28v)
The voltage reference given in P-A's stock part list is LM431, he says the LM329 is better, so based on that, that's what I'm going to use.
Now P-A's design is beautiful, but it doesn't include a bridge rectifier or smoothing caps, My default choice for caps is nichicon UPW, but it turns out that panasonic FM are cheaper and I'll be ordering from digikey anyhow so they'll be what I use. I'll put these together with the rectifiers on protoboard. 6x1000uF 50v
I've chosen panasonic FM for a few reasons, the main one is that the price is right(less than nichicon), but also the impendance is lower than the Nichicon UPW. I'm hoping that C4 and C12 on P-A's design can be 150uF (as panasonic FMs don't come in 100uF from digikey, and yeah I could use FC instead but I'd rather not as the impendance is much lower on the FM)
As for rectifier diodes, diyaudio people seem to like the MUR820, which is overkill but cheap enough to use, so I plan to use a reasonable clone of it.
I've also added good hookup wire and silver solder to the list of things to buy because I figure why not go the extra mile when I'm going that far with everything else?
As of today (14-6-05) I haven't made the final order from mouser or digikey, but I've bought everything I need from amb, audio-cube, and peranders. Barring final changes, I may make the huge order tomorrow or the day after.
Anyhow, I'll leave it there for now and keep this thread updated.
The bom I'm working from is attached to this message, it is a bit messy (will tidy it up later), but yeah it's all there, hours and hours and hours and hours of work worth of it. The equations on the second page are for the resistor calculations.
Any questions, I'll do my best to answer.
PS. Thankyou everyone who's helped so far especially P-A and my girlfriend for their patience and Dakiller for all of his valuable advice, much appreciated.
Jaz