Input Needed For DIY Class A Amp!

megasat16
megasat16 Posts: 3,521
edited July 2009 in DIY, Mods & Tweaks
I have a little time off so I am thinking to build a DIY Class A amp. :D It could be NP design or more likely a modified vintage design from Luxman or Accuphase.

It'll be completely dual mono design with 14 output trannies. I am thinking the final design to have Sankens for the output trannies but I already have a few Toshiba so I am going to start off with these.

Prototype Design has 600W toroid and 4x68000uF 63V filter caps with 35A bridge rectifier for Each Channel. The toroid will eventually be 2.2KW plitron in the final design.

Heatsinks are modified from older computer CPU. I like the idea of Green Tech regardless of Class A.

I have no idea about the Chassis or PCB etching at this time. Currently, I am testing a few designs on the Prototype board and several small boards with point to point wiring.

I would like to get an input on the what Design you like me to build and why?

Do you like to see Negative Feedback (Global or Local) in the design and why? :p

Or Do you favor No Feedback at all such as in some of the Nelson Designs? ;)

Or Do You favor NO decoupling caps in the design and NO protection circuitry in the output stages? :eek:

or Do you favor Pure A more than Push Pull Class A? :confused:

or Do you favor NO inline Fuse Protection in the design at all? :eek:
Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • ViperZ
    ViperZ Posts: 2,046
    edited May 2009
    Very interesting thread. I'll subscribe to it :cool:.

    I am currently thinking about building Dynaco ST-70. Not sure if I'll buy a kit or just buy parts and build one (all manuals, schematics, etc. is available for free).
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  • Systems
    Systems Posts: 14,873
    edited May 2009
    megasat16 wrote: »

    I would like to get an input on the what Design you like me to build and why?
    If it were me I would build one of NP's MOSFET design's because they are proven performers and relatively foolproof to build.

    btw.If you want to do a BJT Class A design I do have an older Elector article detailing a unit using Sanken trannies.I can scan it if your interested.

    Do you like to see Negative Feedback (Global or Local) in the design and why? :p
    It's the overall circuit design thats important,I have heard excellent low feedback as well as higher feedback designs.
    Or Do you favor No Feedback at all such as in some of the Nelson Designs? ;)
    Some feedback is usually necessary for stabilization,NP does use local feedback.
    Do You favor NO decoupling caps in the design and NO protection circuitry in the output stages? :eek:
    Direct coupling is prefered but if quality film type caps are used then they should be reasonably transparent and would certainly add less distortion than the active circuitry.
    r Do you favor Pure A more than Push Pull Class A? :confused:
    A Push Pull Class A design will have less distortion then will a single ended Class A design.
    or Do you favor NO inline Fuse Protection in the design at all? :eek:
    Do you mean meaning fusing the DC power rails or speaker outputs.?
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  • megasat16
    megasat16 Posts: 3,521
    edited May 2009
    GV#27 wrote: »
    If it were me I would build one of NP's MOSFET design's because they are proven performers and relatively foolproof to build.

    btw.If you want to do a BJT Class A design I do have an older Elector article detailing a unit using Sanken trannies.I can scan it if your interested.

    Thanks GV! If it's not too trouble for you, I would like to read the Elector article of the BJT Class A. Currently, I am playing with the BJT designs since I have a quite few Toshiba BJTs and even a couple of Sanken to play with. However, I would love to build one of Nelson's Designed MOSFET at a later time. Since I have the PS section ready, I think trying out MOSFET and other designs would be a matter of time. At the moment, I have a very messy work desk and MOSFET are less forgiving for mishandling and prone to ESD discharge. When I have a more suitable working area with proper anti-static mat sheets, I would try one of NP MOSFET amp. But the problem is I can't get the PCB easily and they are all sold out long time ago.
    GV#27 wrote: »

    It's the overall circuit design thats important,I have heard excellent low feedback as well as higher feedback designs.

    Some feedback is usually necessary for stabilization,NP does use local feedback.

    Feedback has been an excellent tool to control distortion but I read a few NP wide bandwidth design without using feedbacks that sounds great. From what I gathered, some people are against the idea and some embracing it like it's a new TUBE born from SS amps.

    I remember reading a design which said there is no local or global feedback. I think it's from one of NP design but am not sure which one (may be not NP design).
    GV#27 wrote: »
    Direct coupling is prefered but if quality film type caps are used then they should be reasonably transparent and would certainly add less distortion than the active circuitry.

    A Push Pull Class A design will have less distortion then will a single ended Class A design.

    Do you mean meaning fusing the DC power rails or speaker outputs.?

    I wonder why you said Push Pull Class A will have less distortion than SE Class A? I agree the Balanced Input in the Class A has less distortion than the SE input Class A but isn't usually the signal summation point included before the output stages? But in the Class A biasing, wouldn't pure Class A would be less distortion than the Push-Pull design?

    As for the inline fusing, I meant the fuse for the power section for over current draw. But I also found some older amp designs have fuses in the output stage too for speaker protection.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited May 2009
    megasat16 wrote: »
    Thanks GV! If it's not too trouble for you, I would like to read the Elector article of the BJT Class A.
    It could take a bit to find it but when I do I will scan it for you.


    I wonder why you said Push Pull Class A will have less distortion than SE Class A?
    The distortion in SE Class A is mostly of the low even order harmonic variety,these even harmonics would cancel in a push pull output stage.NP does a little biasing trick to his PP output stages ,he adds a small amout of single ended bias.
    As for the inline fusing, I meant the fuse for the power section for over current draw.[
    You absolutely must fuse the AC input.

    DC rail fusing is not necessary and could be problematic.
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  • cnh
    cnh Posts: 13,284
    edited May 2009
    This is a bit beyond me...I've heard Pass designs, Luxman and some tubes. But I'd really like to see heiney9s response to this question as I have a lot to listen to yet--and a couple more years before I can make fine grade distinctions of this order....

    cnh
    Currently orbiting Bowie's Blackstar.!

    Polk Lsi-7s, Def Tech 8" sub, HK 3490, HK HD 990 (CDP/DAC), AKG Q701s
    [sig. changed on a monthly basis as I rotate in and out of my stash]
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  • zingo
    zingo Posts: 11,258
    edited June 2009
    stupid.gif
    Jake
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  • megasat16
    megasat16 Posts: 3,521
    edited June 2009
    zingo wrote: »
    stupid.gif

    HELL NO! :)
    cnh wrote: »
    This is a bit beyond me...I've heard Pass designs, Luxman and some tubes. But I'd really like to see heiney9s response to this question as I have a lot to listen to yet--and a couple more years before I can make fine grade distinctions of this order....

    cnh

    I am just learning all over again....I enjoyed this hobby and I love Electronics.
    GV#27 wrote: »
    It could take a bit to find it but when I do I will scan it for you.



    The distortion in SE Class A is mostly of the low even order harmonic variety,these even harmonics would cancel in a push pull output stage.NP does a little biasing trick to his PP output stages ,he adds a small amout of single ended bias.
    You absolutely must fuse the AC input.

    DC rail fusing is not necessary and could be problematic.

    Thanks for sending the scans, GV! I am reading the first part and guess I need to order a few caps and resistors for this prototype. I'll keep you all posted. I will definitely fuse the AC input. I just wanted to find out what others think. :)
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • heiney9
    heiney9 Posts: 25,401
    edited June 2009
    KISS.....keep it simple stupid :) have as little in the path as possible and the fewer the gain stages the better. While negative feedback does have a few benefits I'd use it sparingly and then only locally. Push/Pull designs tend to have odd order types of distortion and even with a good amount of neg feedback trying to control it, can sound harsh and a lot less "liquid". I prefer a pure Single Ended class A design because it's simple to build, has the more desirable even order harmonics......and has no cross-over distortion.

    My vote.....mostly because I know these types of things a little more because that's where my interest lies would be for a NP design. A nice simple amp w/easy to source parts and support; a Mini-Aleph would be great. But before you decide you need to look at what your room size is and what type of speakers you will use.

    Ultimately the 2 above factors might push you in one direction or another. NP designs are not the be all end all but they are solidly engineered and they usually sound fantastic with many different rigs. If the ultimate goal is musicallity, the NP designs are well proven and there is a wealth of information and variation out there for you to try.

    Good luck

    H9

    P.s. if you build a really nice amp you'll have to pair it with a really nice pre-amp to get the full benefit of a successful amp building project. :)
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
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  • megasat16
    megasat16 Posts: 3,521
    edited June 2009
    Thanks for chiming in, Brock! I agree KISS and I think Simple has Elegance in it's own. My aim is to build several different amp modules and experience them while keeping the Universal kind of Power Supply section...So, I could try comparing several different designs and use the same power section. Pure Class A is always been on a top priority since I had Luxman M-05 in the past but given up for something else I thought it was better.

    I like to try one of NP designs but getting PCB is not nearly possible if it's not impossible. It's going to take time but I'll be there slowly. :)

    Pictures will be uploaded as I had made progress. As for the a nice Preamp, I have a few SS pre-amps and a couple of Tube Pre I could try with it.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited June 2009
    heiney9 wrote: »
    KISS.....keep it simple stupid :) have as little in the path as possible and the fewer the gain stages the better.
    Agreed.
    Push/Pull designs tend to have odd order types of distortion
    If the PP is heavily biased into Class A the nasty higher order harmonics will be reduced substantially even without the help of feedback.
    I prefer pure Single Ended class A designs because it's simple to build, has the more desirable even order harmonics......and has no cross-over distortion.
    An appropriately biased PP output stage will not exhibit any crossover distortion either.

    I'd like to try one of NP designs but getting PCB is not nearly possible if it's not impossible.
    There are periodically organised group buy's for PCB's of certain Pass designs over at DiyAudio.

    IMO the low powered units like the F1,original Zen and the Mini Aleph are impractical for most speakers unless your running horns.If your doing a Pass design I would try something bigger like the F5, Zen 9 Aleph 3/5 etc.
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  • megasat16
    megasat16 Posts: 3,521
    edited June 2009
    GV#27 wrote: »
    IMO the low powered units like the F1,original Zen and the Mini Aleph are impractical for most speakers unless your running horns.If your doing a Pass design I would try something bigger like the F5, Zen 9 Aleph 3/5 etc.

    Yep! I am thinking at least 60W-100W@8ohms of Class A power for each amp. Low power amps are impractical for me since I don't have higher sensitivity speakers to try. The aim is to drive low impedance speakers load.

    Since it's DIY, I don't have to worry about size or shape as long as it sounds good. :)
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Have you made any progress Mega?If interested in doing an Aleph 3 or F5 I have found an inexpensive source for PC boards. These are lower powered than what you are desiring but if interested I can send you the links.Either one will need a hi current 25+25 VDC supply.Parts count on both is low so should be an economical project with excellent sonics.
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    GV#27 wrote: »
    Have you made any progress Mega?If interested in doing an Aleph 3 or F5 I have found an inexpensive source for PC boards. These are lower powered than what you are desiring but if interested I can send you the links.Either one will need a hi current 25+25 VDC supply.Parts count on both is low so should be an economical project with excellent sonics.

    Thanks Fred! I've been very busy lately making the necessary repair to my house. So, I haven't had a chance to play with more amps design yet.

    But I am extremely interested and PM sent for both Aleph 3 and F5 parts.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Here you'll want this if you get the boards. http://www.kk-pcb.com/aleph-3.html
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  • Face
    Face Posts: 14,340
    edited July 2009
    GV#27 wrote: »
    Here you'll want this if you get the boards. http://www.kk-pcb.com/aleph-3.html
    Maybe I'll pick some up to rebuild mine. :o
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • heiney9
    heiney9 Posts: 25,401
    edited July 2009
    Correct me if I'm wrong but these are boards for an Aleph also. Scroll down to the very last entry (other items) and if you click the link it opens a spread sheet with all the parts needed and Digikey part numbers.

    http://www.chipamp.com/orders.shtml

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Face wrote: »
    Maybe I'll pick some up to rebuild mine. :o
    I thought you had an F5 not an A3?is it down and out?
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  • Face
    Face Posts: 14,340
    edited July 2009
    Ah, I mixed up F5 and A5. Yes, mine appears to be toast. The boards "appear" to be ok, but if I were to rebuild it, I would start fresh.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    GV, I pulled the trigger on two A3 boards on eBay. The PCB quality seems to be of good quality compared to the price. I'll update here when they arrive.

    I think I'll get Zen-XA boards from the KK-PCB. They looks quite nice and what I needed for my Class A project. They are expensive though. I am also thinking to get a few Accuphase A50 base boards from HongKong. More things to do in less time. :D
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    heiney9 wrote: »
    Correct me if I'm wrong but these are boards for an Aleph also. Scroll down to the very last entry (other items) and if you click the link it opens a spread sheet with all the parts needed and Digikey part numbers.

    http://www.chipamp.com/orders.shtml

    H9

    I think the one on Chipamp is for the Aleph Mini project.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • heiney9
    heiney9 Posts: 25,401
    edited July 2009
    megasat16 wrote: »
    I think the one on Chipamp is for the Aleph Mini project.

    Yeah, after further reading I realized that. I may just do that because it's really all I need to power my 5B's in the office rig.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    megasat16 wrote: »
    GV, I pulled the trigger on two A3 boards on eBay. The PCB quality seems to be of good quality compared to the price.
    I'm thinking I need a set of those aswell.
    I think I'll get Zen-XA boards from the KK-PCB.
    He has a nice assortment of boards on his site.
    megasat16 wrote: »
    I think the one on Chipamp is for the Aleph Mini project.
    Yep.
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    Face wrote: »
    Ah, I mixed up F5 and A5. Yes, mine appears to be toast. The boards "appear" to be ok, but if I were to rebuild it, I would start fresh.
    GV#27 wrote: »
    I'm thinking I need a set of those aswell.

    Face and GV,

    This guy also sells F5 boards.

    http://cgi.ebay.com/Mosfet-pure-class-A-amplifier-PCB-F5_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a1Q7c39Q3a1Q7c72Q3a1205Q7c293Q3a1Q7c294Q3a25QQ_trksidZp3911Q2ec0Q2em14QQhashZitem3353757c56QQitemZ220443540566QQptZLHQ5fDefaultDomainQ5f0QQsalenotsupported
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    megasat16 wrote: »
    Face and GV,

    This guy also sells F5 boards.

    http://cgi.ebay.com/Mosfet-pure-class-A-amplifier-PCB-F5_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a1Q7c39Q3a1Q7c72Q3a1205Q7c293Q3a1Q7c294Q3a25QQ_trksidZp3911Q2ec0Q2em14QQhashZitem3353757c56QQitemZ220443540566QQptZLHQ5fDefaultDomainQ5f0QQsalenotsupported
    Indeed he does and I also see he has B1 boards aswell.
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Now this is tempting.D http://cgi.ebay.com/Mosfet-pure-class-A-amplifier-Kit-F5-stereo_W0QQitemZ320390699757QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item4a98c61aed&_trksid=p4634.c0.m14.l1262&_trkparms=%7C293%3A4%7C294%3A30 Though I'm not comfortable with the Pass logo having been silk screened on to the boards.
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    Thanks GV! It sounds like a deal with all the components come with it. I am now looking for the toroids for the A3 and F5.

    I really want to try Zen-XA kit from KK-PCB. 120WPC is more likely what I need.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    I went a little crazy and bought a bunch of stuff from Jim Audio's eBay store from HongKong. The wife didn't know I just spent the money on the PCBs instead of the lottery ticket she asked me to get. :D

    The stuff I bought

    2 x Aleph 3 boards
    1 x F5 Kits including two mono boards and parts
    2 x A3 and F5 Power Supply Boards
    2 x Soft start circuitry PCB (must be basic version but it'll work for now)
    2 x 48V DC regulators PCBs

    I am also looking at the speaker protection circuitry and this one seems decent.

    http://cgi.ebay.com/Top-quality-Speaker-Protection-module-for-Audio-DIY_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a2Q7c39Q3a1Q7c72Q3a1205Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3911Q2ec0Q2em14QQhashZitem3ef6514400QQitemZ270420493312QQptZLHQ5fDefaultDomainQ5f0QQsalenotsupported
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Wow you are going to be a very busy fella.:)


    So many choices have me in a quandry as to what to build.I have narrowed it down to a 4 ch LM3886 GC or an F5.I recieved an email today indicating that Peter Daniels F5 boards are now instock at $15 a pair. The versatility of the 4 ch GC is attractive for active speaker experiments or bridging etc,but it would be nice having a Class A unit (again)to add to my collection.
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  • megasat16
    megasat16 Posts: 3,521
    edited July 2009
    Yep! It's going to take a while to get all of these built and tested.

    $15 for F5 PCBs are a very sweet price. I've just got an invoice from the seller for the total of $149.41USD which is still not too bad. I think I'll get the protection circuits pre-built since it seems cheaper too. Didn't you built the speaker protection circuits for the GC amps?
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • Systems
    Systems Posts: 14,873
    edited July 2009
    Your going to need some serious heatsinking, these look usable.http://shop.ebay.com/merchant/barrredboss_W0QQ_nkwZQQ_armrsZ1QQ_fromZQQ_ipgZ
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