A DIY Pre-Amp Kit

edited February 2016 in DIY
Here are the basic at the moment idea we have.
MM,MC, MP3(special filter), CD, Pre Out and SECA Headphones, very similar to the one Alan Brown heard at TQ.
It is filled with SMD and the photos are the one Alan E. has used. and is using now.

image

PSU Board

image

Pre-Amp PCB
image

As will see it has two pre-outs and two HP (SECA) outputs these can be set for up to 5W/ch so be warned.
The PSU can be run in Standby and have a small press to make switch to operate it.
Ribbon cable was used to connect the power to the pre.

Circuits and BOM to follow.

Also note the space behind the volume pot this will accommodate a IR Remote RX later, for the arm chair DIYers. (a contradiction of terms). 

The MP3 uses a twin filter to emphasize the high frequency and the reduce them with correct phases and produce a much better sound the BW is held tight and flat 20Hz - 20KHz thus reducing clock crap and other unwanted signals.

Comments

  • Nice work Colin

    A couple of questions.

    on the HP amp

    5W into what load?

    on the Pre

    is the pre section a unity gain buffer arrangement?
  • BTW

    Have you heard the Muses volume control?


    it's really rather good and one that I've used in my DCB1 to good effect.

    MR Pass also likes them. 

  • 8 Ohm a nasty load but it will run Stax and 300 Ohm easy, it is dependant on you on what Q.I. you set and the cooling you can provide for the output stage and the PSU.

    Wait the info is coming.
  • Hi Colin

    looks like you read my mind on the 8Ohm thing. I ran my Lancasters from a HA once and it sounded pretty good I also have 62Ohm AKG701 which can be a little tricky but when driven well sound superb IMHO.

    I'll wait for the info

      
  • edited February 2016
    I have to agree on the K701 example given. They can go from toppy and lightweight to fantastically articulate and satisfying depending on how well they are driven.

    That's an interesting idea on the "mp3 in" circuit but I'm thinking, how many people would actually use mp3, in anger, on a decent system? Genuine question BTW, please give views there anyone.
    Love the two pre-outs but personally would have no use of the headphone section, which leads me to the next thought.

    Why not make the sections fully modular (as far as layout benefits/concerns allow), builders could then select only what they need. This could lead to more actual builders taking the leap, with the possibility of adding other sections later if needs change?

    Just throwing out thoughts here, like a stone in the proverbial pond, let's see what the ripples bring ;)

    I'm off to read up on the MUSES Volume Control now...Shaun, how good compared to the likes of DACT (I currently use a Khozmo 50Hz stepped shunt attenuator in my existing DIY pre).

  • +1 for Fully Modular.
  • One thing that sit in my mind is every module would have to have it's own art work and thus it's own tooling cost, this would make it very costly a) to set up and b) to buy. So would the DIYers be able to afford it NO me thinks.
  • Col, I'm delighted!!

    I'll go with the flow, honestly. I know it will be awesome. Put me down for one.

    I will practice my 'flat toe' exercises for the SMD soldering, as you recommended a long while ago...

    Be seeing you in a few weeks, I got a bundle of scrap from Dave for you to take a look at.
    :-\"
  • Modular makes sense.

     

    Yes more expensive but spread over time collecting the different modules the cost becomes instalments so easier in some ways to afford. IMHO It allows for a staggered realise approach which can help

     

    BTW

     

    I've never built to save cash and only for the pleasure it brings (like most DIYers). For example my Paradise phono stage/Calvin Buffer probably cost me around £500 to build (not cheap) but it sounds superb and as far as I know is not available commercially at any price. Joachim Gerhard (Audio Physics) designed it from scratch in what seemed to be a 2000 post brain storm over on DIYA.

     

    It’s expensive but good (read very good) and IMHO cash well spent.

     

    I also have another 3 Phono Stages in rotation.

     

    ‘’A change is as good as a rest’’

     

    A pre without HA/PHONO is more of a catch all as it can also be used by the Digital brigade (I have DAC'S and phono stages) but it's going to be hard to persuade someone with Digital only to invest the time and cash building the phono stage no matter how good. (And no matter what we may think of digital replay it’s not going away any time soon)

     

    That's my general feeling but I'm still interested enough to build one but I’d rather pay a little more and have the modules.

     

    But some specs are coming so let's see.

     

    Just a few thoughts.


    Heads Up

    BTW anyone looking for a 180g Blue Note John Coltrane - Blue train? Don’t Laugh but I picked one up in Sainsbury’s. Di Agostini presents Classic Jazz with free mag. I nearly fainted as my copy is getting a little over played so a replacement at that price was welcome and more to follow.

     

    Yup £9.99 woooo

  • I'm happy to do SMD soldering for anyone if it helps..........
  • For super tiny parts I find solder paste is very effective
  • quickie said:
    I'm happy to do SMD soldering for anyone if it helps..........

    Thanks Paul
  • ''I'm off to read up on the MUSES Volume Control now...Shaun, how good compared to the likes of DACT (I currently use a Khozmo 50Hz stepped shunt attenuator in my existing DIY pre).''

    Sorry Chris but I missed the question.

    Not tried the Khozmo but both of my steppers are ladder types as GP and DACT have moved away from shunts. They state that the quality of their resistors and the low self noise they produce make shunts noisier. maybe in theory but who knows.

    I swapped out a Goldpoint for the Muses in my DCB1 and never had any thoughts of swapping back since.

    The Muses

    Well it's very good. it's pretty much a discrete resistor ladder controlled by relays but on one chip the signal lines are much shorter than could be achieved by and stepper.

    I just bought a ready made unit with all of the control stuff pre done (just as well as i'm much less than average with such things). if you do like wise then the Austrian one may work out less expensive than the customs charge riddled US version that I have.

    In short

    I have DACT,Goldpoint steppers and prefer the Muses.

    it's a good unit with remote (which I never use honestly guv) and a flywheel control for volume and balance.

    Take care Chris
     
  • Well here is the circuit more to come like BOM.

    image

    image

    image

    image

    This is a basic and simply design and layout, but do not be put of by that it sounds lovely.

  •  Great stuff Colin :)


  • PSU for Pre-Amp.

    image

    image
  • Brilliant Colin, thanks for your efforts on this! Can't wait to get stuck in.
  • Hi Alan, this is the one you herd at my last workshop in Somerset.

    image
  • Very aesthetically pleasing to me, that image. Is there a version without the 3 turquoise rectangles?
  • The top one has to stay so your Mum can iron on your school gear name tag.
  • Hi Colin

    Looks very nice indeed.

    Any chance of a walk through the most significant parts of the circuits? for the less enlightened like myself.
  • AntiCrap said:
    Hi Alan, this is the one you herd at my last workshop in Somerset.

    image
    Looks frighteningly complex! Sounded superb though, utterly sensational.
  • Docfoster said:

    Very aesthetically pleasing to me, that image.
    Is there a version without the 3 turquoise rectangles?

    :-)
  • I could do special just for you.

  • Hey there, Big Nose Bar Xenopus,

    I was finking... how far beyond a numpty like me is it to build the above? I appreciate that the SMD stuff is small and a challenge, and probably help would be needed with an order list of components. But, the tooling is already made for this board, no? As is a prepared BOM?

    Could DIYers put this one together?

    Or pay for a populated board sans chassis & transformer?

    Like I said, just thinking aloud mate, happy to be corrected/shot down in flames as required. ;)
  • Big Nose Xenopus one is leaded easy job, yes tooling is done I just have to order more.


    NOW BURN BABY BURN
  • Alan, if you want to make it yourself, I have done lots of tiny micro SMD work with solder paste, it makes the job A LOT easier and neater.  Colin doesn't like it though.
  • Could we not do a 'group buy' so that Colin doesn't have to foot the start-up cost.

    How many of us want one?

    Are there any questions any of us need answering before we can commit our cash to the project?
  • BOM for leaded phono/hp kit.

    image
  • OK there is 4 SMD 100nF 0805 caps only.

  • uglymusic said:
    Could we not do a 'group buy' so that Colin doesn't have to foot the start-up cost.

    How many of us want one?

    Are there any questions any of us need answering before we can commit our cash to the project?

    Hi Colin

    Looks very nice indeed.

    Any chance of a walk through the most significant parts of the circuits? for the less enlightened like myself.

    Also would there be any chance of adding line level IP?

  • I'm interested, but in the one in the first post, with the MM/MC, CD/MP3 inputs, not so much the one further down.  Which one is being produced?
  • AntiCrap said:
    Here are the basic at the moment idea we have.
    MM,MC, MP3(special filter), CD, Pre Out and SECA Headphones, very similar to the one Alan Brown heard at TQ.
    It is filled with SMD and the photos are the one Alan E. has used. and is using now.

    image

    PSU Board

    image

    Pre-Amp PCB
    image

    As will see it has two pre-outs and two HP (SECA) outputs these can be set for up to 5W/ch so be warned.
    The PSU can be run in Standby and have a small press to make switch to operate it.
    Ribbon cable was used to connect the power to the pre.

    Circuits and BOM to follow.

    Also note the space behind the volume pot this will accommodate a IR Remote RX later, for the arm chair DIYers. (a contradiction of terms). 

    The MP3 uses a twin filter to emphasize the high frequency and the reduce them with correct phases and produce a much better sound the BW is held tight and flat 20Hz - 20KHz thus reducing clock crap and other unwanted signals.

    Hi Guys we have decided to only produce 5 of these pre-amps for DIY. Two are already spoken for please PM me for PCB costs.

    More info BOM etc later.
  • I sent a PM to shoom earlier, I hope he gets in there fast!
  • Hopefully just pmed you Colin
  • Got PM see answers thanks chaps.
  • Just signed my self in and being the happy builder/user of one of Cols superb SECA amps would very much like to build one of these pre's.
  • Hi Keith

    Nice to have you here.

    I'd also like to have a go at building a pre.

    the power sounds superb.
  • But let's try to spread our builds around the forums a little.

    DIYA is my aim for a pre amp build thread.

    it may even turn a few more onto the super sound of the SECA PA.
  • image

    Great to see these being taken up. :-)
    Really looking forward to seeing how you guys get on with things.
  • Hi Shaun thanks for the welcome. Likewise regarding the the SECA sound; no other word for it but superb
    B-)

    I did actually post a few pics in the Solid state section over on diyaudio but didn't get much of a response.

    Maybe a build thread would have been better; they don't no what they are missing.
  •  
     Colin started a thread some time ago over on DIY Audio, but not much interest.

     
     http://www.diyaudio.com/forums/solid-state/275291-seca-kit-colin-wonfor.html
     
  • edited February 2016
    quickie said:
     
     ''Colin started a thread some time ago over on DIY Audio, but not much interest.''

     
     http://www.diyaudio.com/forums/solid-state/275291-seca-kit-colin-wonfor.html
     

    Yes I found the thread over there but people actually building may be a different story IMHO. There is quite a bit of interest in class A over there but mostly PASS which is good stuff but a few people actually building may do the trick.

    just a thought.
  • When I had my TQ Iridium I also has several PASS lab amps on loan along with some crazy (I forget the name, Italian huge class A amps and I kept coming back to Colin's design. I haven't had the chance to compare my DIY 40amp Wonfor build to anything really, I always find comparisons interesting, shame I couldn't make it to the Chews day at Pauls place.
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