Ben's One4 (WONFOR) SECA build (ready-populated boards)



  • Righto!
    I think I've gone through everything.
    It's working! B-)

    Slight problem tho. There is a significant hiss on both channels.
    So I must have done something wrong.

    The hiss disappears completely if there is no input (ie it is present only if something is feeding the RCAs).
    Any thoughts?
  • Ben,

    What is your source? I take it that there is no hiss with the TOCA. If there was an earth loop then I would expect hum rather than hiss. Do you have some photos of the amp and connections? Is there music when the inputs are connected or just hiss?
  • Thanks.
    Yes, it's definitely hiss and not hum.
    I've tried 2 sources. My media PC and my iPhone (via the headphone socket). (I don't use a preamp.)
    Neither cause hiss through the TOCA.
    The iPhone is interesting because about 10 seconds after the music is paused / stopped the output from the headphone socket must cut out. This isn't something that I had known about before today, but it is evident with the current hiss problem as the hiss disappears 10 seconds after I press "pause" on the phone.
    The hiss is loud enough to be heard behind the music as it plays.

    Thanks for casting your sagely eye over my rats nest. It is entirely possible that I have made several errors. The trannies are humming quite a lot, but that's not unusual in my system. I appreciate your time throughout today. If any more detailed / close-ups would be useful please let me know...

  • Yes, the transformers will buzz a bit with the bias cranked up.

    Do you get any hiss with no source connected (inputs shorted)
  • Hi Paul! How's the cold...?

    No. There's no hiss with no source connected.
  • Sondale,
    I forget to let you know. Maplins didn't have any of the clip / hooks for the multimeter, so I recruited that 2nd pair of hands you mentioned...

  • Almost had a disaster.
    Had explained to the family not to go near the exposed wires in the new amp, forgetting that the cat can't speak English and likes warm, enclosed spaces.
    Thankfully I managed to turn the thing off before the house filled with the smell of burning fur...

  • I feel like poo Ben !

    If amp is quiet with no source, then its working ok, so thats good but doesn't explain the hiss.....
  • I'll plug the TOCA back in and see what happens...
  • Ben,

    Is the earth on the phono input shorted to the case?

    If you run only one channel does the hiss go away? You could disconnect one of the transformers from the chocolate block connector, either one would do (just to be safe disconnect from the mains first).

    Hopefully Colin will be back tomorrow, probably late on.

  • Gotta love Gingers !

    Mine perches himself right on to of my amp sometimes :)

  • TOCA back in situ, and...
    No hiss...

  • Sorry to hear you're yet to recover Paul...
  • edited September 2015
    No idea what's going on with the hum. It's less noticeable with the JPWs I'll be using it with.
    So I've sealed up the case and will stick it in its new room tomorrow.
    Final piccies...





    Most important thing to say are big thank yous to Colin, Paul, Sondale and Sov and everyone who's encouraged me. Shoulders of giants and all that... Obviously I could not have started, continued with, or completed this build without you!
  • Nice one Ben, when you get a chance tell us how it sounds.
  • And how does it sound vs the TOCA? I see the new amp isn't planned for the big rig.
  • I'd rather save any comparisons for when I've got the problems sorted Dave...

    Reconnected everthing today and the hiss remains with the new amp. It's weird. My brain can't explain it. The amp doesn't hiss on its own, but only when an active source is connected. But, when the TOCA is stuck in exactly the same setup (same source, position, cables, speakers) there is no hiss to be heard.

    Also, I've noticed that on the channel of the new amp there is a distortion (mainly from the tweeter) during bass notes, but on the left channel only. (Again not present on the TOCA.)

    Clearly I've effed up somewhere on the line...
    Ah well, gave it my best shot.
  • Yup. Understood Ben.

    What a bugger with the hiss. But I'm sure we have more than enough knowledge and experience here to put it right.
  • Loving the collective pronoun there Dave.
    I have every faith in the membership of this forum to find a solution.
    And, in my ability to let them. :)
  • Sounds like a FET issue
  • Sounds like your amplifier has a cross dressing issue,
  • I reckon the cat got a tad hot :((
  • edited September 2015
    Thanks Mark, I'll put it on the list.
    Paul's givien me some thoughts to.
    I'm sure Colin will pitch in soon as well. I think he's in Scotland at the moment.

    I'm liberal-minded. A cross-dressing amplifier, I can live with.
  • Sorry I have terrible predictive typing problems,
  • edited September 2015
    I think Col's back on Wednesday.

    Actually, I'm wrong. It's today, Tuesday.
  • Hello Honey I am Home.
  • Ben Hiss mmm disconnect all cable and the mains.
    With the meter to ohm check no connection of any input is connected to the case, and the other wires on the PCB.

  • Ben, I'm loving your work mate! What a lovely amplifier this will be!

    I'm sure your teething issues will be easily dealt with, don't worry. Making one of these is to Col as making a cup of coffee is to us. And that Paul Quick looks like he knows which end of a soldering iron gets hot also.

    I'll build one like you some time, I look forward to the support on Chews at that time!
  • Have you seen the cat since you put the lid on? That might explain the hiss 8-X
  • Thanks Colin.

    Placing one contact against the earthing point on the case, produced no reading from either of the RCAs or any of the speaker terminals.

    I'm getting some sort reading when I measure across the RCAs and the wire on the PCB board that Quickie has identified as the "thermistor wires". This is true for both boards.
  • Alan, hi. Thanks.
    Agreed. The sound it makes sounds extremely promising. Once the hiccups are sorted I'm confident it'll give the TOCA a run for it's money.
    Btw it was partly your amp build that encouraged / pressurized me into this!
  • Brum, yes! The cat is alive and kicking.
    To be honest he's such a lethargic lazy sod, I'd imagine 230V up his arse might be of benefit to him.
  • Sorry Ben, but I honestly don't know.

    One for Colin i'm afraid.
  • Indeed. He's kindly offered his services when I can get the amp and him together.
    I'll wrap the old girl up for now.

  • I think the cat's broken her.
  • It alive and going home today, lovely sound and very well made for a first timer, well done Ben, and thanks for the Curry nice, and COFFEE mmmmmm lovely.
  • Fantastic. Let us know your thoughts Ben ,
  • edited October 2015
    Now I discovered on Ben,s Kit, that the FET,s were made in Hong Kong and in the Other in Ireland, this should not cause a problem, but for some bizarre reason the constant current FET mounted in a Chassis and Earthed went in to Parasitic Oscillation and this was the cause of the HISS.
    The simple and best solution was to fit a 100nF 50V Farnell page.

    Across the Gate to the Source.

    The two outer pins NOT THE MIDDLE ONE this can be done whilst it is in the PCB BUT NOT POWERED UP.

  • edited October 2015
    Well I've only just got home actually after a lovely trip around the south of our country:

    Thurs-Fri: chez-Wonfor
    Fri-Sun: South London and Twickenham for the Oz v Wales game :((
    Sun-Mon: Cardiff for the Ireland v France game...

    So have only just managed to plug the amp in to the Gloucester mains after its return from being sorted by its maker.

    Firstly, big thanks to Colin for his hospitality, expertise, generosity of time and good humour. One thing that brings me pleasure in life is seeing people doing something that they are really good at. Watching Colin perform his diagnostic and reparative magic was a better spectator sport than watching the Welsh rugby attempt to score against 13 Australians.
    The end result (no hiss) is also better than Saturday's score board after the final whistle.

    I'm having a good listen right now with the amp at home, and comparing it to the TOCA.
    Important to point out that on comparison these are clearly from the same Wonfor A-Class stable. There are differences in sound, but arguably only in degree.
    Also important to point out that the kit amp cost me about £500 to build. That represents the most ludicrously good value for money for a new piece of kit that I have ever encountered. A no-brainer. Also it didn't take very long to construct with the pre-assembled boards version (no more than a couple of days for me, a complete novice). (As Colin points out, the probelm with the hiss was caused by a dodgy batch of FETs. Not my assembly skills. :D )

    Listening now, the main difference between the TOCA and the One4 kit amp is that the bass through my big Goodmans on the One4 audio kit amp is (even) more thunderous than that from the TOCA. By "thunderous" I mean (even) deeper, (even) louder, (even) more textured, (even) more impactful and (even) more controlled. In short (even) better than the TOCA.

    That word "impactful" probably sums up the change across the board really. Every sound is more visceral. Noises are more accurately honed, discrete and neatly pressed into my ears. I noticed this when listening in Colin's little shed through his small monitors at a listening distance of about 1m. I wondered whether the confined space was creating all of the impact, but no, the amp was doing at least some of the work. Especially in the bass. Colin and I tried some really deep bass stuff in his shed - some Speedy J electro and then some Keith Hudson dub stuff. Colin remarked "These speakers don't go low enough". He was right. With the amp now feeding the much larger Goodmans cabs and their (at least) 10 inch drivers the bass on those same tracks goes way down to my knees, almost touching what the 18 inch Goodmans sub behind the sofa can do in terms of depth, but with much greater finesse.

    Perhaps some increased headroom contributes to this development in impact across the frequency range, but it sounds more than that to me. Maybe its the way FETs behave, as opposed to the Darlingtons in the TOCA. Colin certainly sounded enthusiastic when explaining to me why he likes to use FETs these days. In any event, by comparison the TOCA I think sounds more laid back; possibly a smoother experience. Time will tell which slight variation on a theme I like more.

    Also the "midrange" seems a bit richer with the One4 kit: A little more substance to vocals. Again, too early to tell whether this small difference is one that I prefer. I am annoyingly fussy in my striving to achieve the particular vocal tone and presentation that I want - in fact it is one determining factor in how far away from the back wall are my speakers. I've become very enamored with the way the TOCA does the midrange. I want to see how my ears' relationship with the One4 kit amp develops over the coming days. Perhaps swap the TOCA back in at the end of the week and see what that change of experience is like.

    To return to my original point, these are two cracking amps, amongst the best that I have heard, and certainly the best that I have owned. I'm very happy with both and will be selling neither. That other Wonfor class A that I own - the Inca Designs ID25 hiding in my cupboard has been relegated to 3rd spot now, poor thing!


    One4 kit amp is the one on the shelf, the TOCA is the one taking a rest.
    "But what's that shiny little TOCA badge on the front of the kit amp?" I hear you muse... Well, whilst rummaging around in his workshop for some tiny component last Thursday, Colin came across what he says is the last remaining TOCA badge. He kindly gave it to me and told me to superglue it to the fascia of the Won4 amp. It's not really a TOCA, I know, but it looks really nice.
  • There is much drooling and envy afoot here in LA.
  • Well done Ben, it does look nice better than my Thunderbird 5 look alike.

  • edited October 2015
    Colin, I thought it was more 1930s Flash Gordon... Very retro-cool. B-)

    (BTW, do you mean Thunderbird 2? :-B )

    Dave, get you with the "here in LA" clang! <:-P
    Make the most of your break. Nice. :)
  • Ben: LA is local spiel for Little'ampton.
  • Little Hampton? ;)
  • No Mark "Large Hamburger" with relish mmmm nice.  :)
  • I'd rather chicken madass with all trims
  • Me I love cheese and apple and COFFEE thanks Ben nice coffee. Nice Indian meal also, come back soon to make pre he he  :D
  • @Mark Speak for yourself :-)
  • Ben. I understand that's the 10 wpc kit that you're comparing with the 20 wpc TOCA. Is that right?
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