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DIY amp and pre recommendations (probably DiyAudio/Pass)

Discussion in 'd.i.y.' started by booja30, Feb 17, 2020.

  1. booja30

    booja30 pfm Member

    I'm thinking about taking the plunge and building one of the DiyAudio amps. I'm looking for recommendations among those options. There are several 25w class A options, a 50w class A, a 100w class AB, and probably others. I like that they (DiyAudio) have come up with a kind of modular system where one chassis and PSU can be (re)used to house/power several of their kits (modular pre-drilled hole patterns, etc.).

    I'm looking into a DIY build because I love projects like this and learning new things. I have done some recapping/refurbishing of older gear and have some (limited) understanding of analog circuits. I'd like to try something like this and build from (kit) scratch.

    My other motivation is that I've sold on my old speakers (Epos ES11) that I never really loved, and am about to receive some new (to me) B&W 683 floorstanding speakers. The B&Ws are actually fairly efficient (89-90dB) and may be ok with my 30w Sony TA-F3000ES or 50w Rega Brio-R, but I'm still tempted to try class A for the first time.

    What do folks recommend? I've been looking closest at the F5, F6 and Aleph J, but would consider other recommendations. I'd consider more obscure options but having a community of people available is certainly a plus.
  2. CarrotMan

    CarrotMan pfm Member

    IMHO an F5 is about as universal as it gets with 25W class A, so that to me would be a good place to start if you want to dip your toes in. As you mention if you use the diyaudio system you can exchange the amplifiers for something else later on and still keep the chassis and PSU which drives most of the cost.
    booja30 likes this.
  3. Marra

    Marra pfm Member

    Another to add to your list is the M2 my favourite at the moment from Nelson Pass designs I've built. Pre-amp if you want to stay with NP designs would be the B1 Korg Nutube such an open sound with a big sound stage. Another excellent power amp is the Hifi Sonix kx class A/AAB 28 watter.

    booja30 and eastone like this.
  4. eastone

    eastone pfm Member

    M2 with valve pre here, very happy with it. F6 is much more driven sounding, but still sweet, also using transformers. F5 is very low distortion - no transformers and no capacitors in the signal path.
    booja30 likes this.
  5. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I'd not touch Korg Nutubes with a barge pole here!!
  6. deebster

    deebster Half Man Half Biscuit

    Me neither. Sounds dangerous.
  7. killie99

    killie99 pfm Member

    The Salas DCG3 from DIYAudio is a stunning pre amp, not the cheapest to build but will give ANY pre a run for it's money, here's a couple of pics of mine:


  8. Marra

    Marra pfm Member

    You don't have to touch it Jezz just loose yourself in the sound.
  9. davidjt

    davidjt pfm Member

    Presumably you've already read these? http://www.firstwatt.com/reviews.html

    It's more likely there'll be someone using 683s on the diyAudio/Pass forum. (Ignore Zen Mod - he'll advise building every Pass design there is. ;))

    The diyAudio store M2 set does include the different input boards to 'tune' the sound, which may be a plus for you. And, in case you haven't come across this already, where there's no complete kit available from the store there's often a saved BOM at Mouser which you can access, save as your own and then modify if necessary. May be slightly more expensive than shopping around but saves a lot of time and avoids mistakes.

    (One of the above lengthy reviews has got me thinking about a pair of F4s......)
    booja30 likes this.
  10. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Korg Nutubes are total crap. Completely unsuitable for any sort of hi fi amplifier. Any other valve picked at random, of the worst quality, and 80% worn out will still thrash a Nutube. Look at the spec sheet. They barely even work!
  11. booja30

    booja30 pfm Member

    That's a good tip about the saved BOMs -- I wasn't aware of that. I'll go poke around for them and hope that they can be transferred to mouser.es.
  12. Marra

    Marra pfm Member

    This little pre has been built by a good number of folk worldwide the majority liking what they hear. We can't all be wrong.
  13. 337alant

    337alant Negatively Biased

    For Class A/B there is also the excellent Avondale Audio NCC-200, 220, 300 power amplifiers you can buy built up circuit boards for the amplifiers and the Cap6 boards for the rectification and filtering so you just need to add a Transformer and case
    If you want to build the amps from circuit boards you will have to speak with LesW for just PCB only
    Les also does the Grad 1 and 821 Pre Amp boards and TPR4 dual voltage Regulation boards for building a Pre Amp, again call LesW by phone to discuss is the best way

    Tom Bonjour likes this.
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Oh you can! The point is that as a valve the Nutube is poor beyond belief. Look at the data sheet. Pretty much every parameter is worse than a standard valve by at least a factor of ten and way more than this for some specs. This doesn't mean it is not possible to make a preamp that many will consider OK using it.... as a novelty. It does mean that any other valve would do the job much better though, including a knackered one. Even a valve so worn out as to only just work has MUCH better specs than a Nutube... like 10X better. I could build a line pre with early '60's germanium transistors and although they are awful beyond belief in most areas compared to a modern transistor, a line pre is so undemanding a use that most would say it sounded fine. It would not be a good idea though.
    This is a case of "Hey lets have a world first by using this new weird valve in a hi fi pre amp! yeah it's awful beyond belief but it's only a line pre and we should just about be able to wring enough out of it for most people to say it sounds good". Not really the best basis for choosing a valve for the job!
  15. booja30

    booja30 pfm Member

    One (hopefully) quick question before I dive even deeper...

    I read in at least 2 places where folks had warned about certain amp (and preamp) designs not having capacitor coupling on the output. The problem being that under certain conditions the amp could output DC to the speakers and fry the large drivers. Is this something to take in to consideration for DIY build options? Are output coupling capacitors normally present on off the shelf class A amps? If so is there a reason they are omitted from some of these designs?

    Now that I think about it I believe it was the build thread for the B1 Mezmerize preamp that mentioned the output was DC coupled (no caps) so it could case an amp without caps on the input to output DC.

    Sorry for any misuse of/bad terminology.

    And thanks for all the feedback/suggestions so far.
  16. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    The vast majority of SS power amps have no output cap and could fry a woofer under fault conditions. it has nothing to do with class A operation. Only suitable speaker protection circuitry and/or fuses blowing fast enough can prevent it. The ubiquitous Velleman speaker protection module should give peace of mind.
  17. booja30

    booja30 pfm Member

    Ok, I am learning a lot but also my eyes are getting red from soaking in all this info. A few hopefully simple questions that are probably buried in a FAQ for idiots somewhere but I can't seem to find answers so far:

    * Some builds (including the DiyAudio "Universal PSU") show bare wire links installed between boards. These boards tend to be ones that were perforated so they can be split apart and so the tracks aren't continuous. What is the link wire used? It looks like solid copper...

    * Do MOSFETs for example come with mica insulators and/or plastic shouldered washers or is that something you buy separately?

    * How do you not go crazy putting together a shopping cart from a big BOM spreadsheet?

    If there is a noob FAQ somewhere (maybe even on PFM!) that covers these kinds of dumb questions, please let me know! :)

    I can see this getting expensive (but worth it)! Variac, maybe a soldering station instead of my cheap Amazon iron, maybe a USB scope... Hmmm.
  18. booja30

    booja30 pfm Member

    Thanks for that. I found the Velleman kits after you mentioned them and then noticed similar kits (soft start / speaker protection) on DiyAudioStore...
  19. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    You need to buy the insulators etc separately.
  20. nobeone

    nobeone pfm Member

    If it looks like copper wire then it probably is, without a photo or a link it is hard to say! More usually you would use tinned copper wire as it doesn't oxidise and is easy to solder to, bare copper will oxidise, it could be enameled copper wire (looks like copper as the enamel is transparent) but this can be harder to work with as the enamel is insulating and not as easy to solder with as tinned copper.

    It is perfectly normal to go mad putting BOMs together and ordering them. Not least as inevitably something will no longer be available or has gone obsolete and replacement can be anything from trivial to impossible.

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