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    Default 2a3PSE

    Another project on the go...

    I won an unused chassis for a WAD 2A3PSE on eBay the other day. I have a pair of output trannies for it already, so I thought it was worth a go. 8.5W and the valves are a fair bit cheaper than 300Bs.

    I think I've managed to secure a mains tranny and a choke for it. So a fair amount of parts to source, but it shouldn't be too much effort. Watch, as they say, this space...
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    :P
    www.audioorigami.co.uk

    And visit my face book page--- check out Audio Origami

    http://www.facebook.com/AudioOrigamiTonearms

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    :P indeed...

    For me the laborious bit is the sourcing of all the mounting hardware; M3 and M4 screws and bolts, standoffs etc.

    talking of which, the chassis is cut for the most unusual speaker binding posts I've ever come across. the mounting holes are 10.5mm square. so far I've not managed to find anything with that pattern. anyone able to shed any light on which speaker posts might fit a square hole?
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    Last edited by TIU; 27th October 2013 at 23:26.

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    close but not quite; the mounting hole for that one is round, unfortunately.

    I suspect I'm going to have to fit blanking plates to the holes and re-drill for something more appropriate.
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    progress so far:

    I bit the bullet and collated a list of non electronic fittings. lots of M3, M4 and M5 screws, nuts, bolts, threaded rod etc ordered. and the remaining valve bases. and a 5U4GB rectifier.

    Should have plenty spare screws after this...
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    Well it's under way of sorts; screws and nuts arrived so I could fit all the signal path valve sockets. waiting on another Octal for the rectifier to arrive..
    IMG-20131029-00352.jpg

    IMG-20131029-00354.jpg
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    How's the build coming on Kenny? Are you building this to the original WAD circuit?

    I had a look at those square holes for the speaker binding posts and most of the fancy WTB copy binding posts need a 10mm round hole so no probs. The insulating washers are plenty big enough. Dirt cheap on the Bay.
    Si.

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    I'm just about to take delivery of the remaining Iron; mains Tranny and choke. I've also been donated an original set of speaker binding posts, plus a few rectifiers, and capacitors for the 2A3.
    I need to drill the mounting holes in the chassis for the OPTX; there's only two holes drilled to mount each transformer; halfway along the length. but one transformer has six holes (two as per the chassis and one at each corner), the other has the four corner holes and only one hole along the length. so I need to drill the four corner holes in the chassis. I don't really fancy drilling through all the laminations of the tranny... But I need to check that it's ok for me to bung it on a pillar drill at work in my own time; as I'm only in the door two weeks I don't want to be taking liberties...

    I've got a 5U4GB rectifier tube ready to go, but need to save up for some 2A3s and the 6SN7s Once I start getting paid in my new job, I might be able to afford them!
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    starting to move again. I now have all the transformers, and I'm starting to populate the chassis. I've managed to drill out the output transformer mounting holes, and cut the threaded rod to length for the nice domed nuts instead of the ugly flat screws that came with the mains tranny.
    Although I'm annoyed that I've managed to scratch the powder coating on the top. not sure if I should leave it as is or try to spray over the damage; might make it look worse.

    in terms of components, I've got the humbuckers, mains iec socket fuse and switch, all the phonos and speaker connections. I'm waiting for the ALPS blue 100k volume pot and 6 way rotary source selector switch to arrive. as for the actual electronics, Ive now got the 5v regulator, the rectification for the 4 2A3 heaters and the tag boards. I've ordered the heatsink for the regulator as well as some of the higher power resistors. after that it's mainly 1/2w and 1w resistors and some capacitors to get. and of course, the valves!

    I'm not sure what to do about the control knobs yet. part of me wants to turn a couple from some purpleheart or bubinga on a wood-lathe, but I'm not having much success in finding any kind of threaded insert I could use to fit a grub-screw for locking onto the volume control and selector shafts. Any suggestions welcome!
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    I use This Company Kenny. They have some dinkly little brass inserts that you could screw into yer nob ,lol.

    The unheaded brass screw in inserts should suit just dandy.
    Elitist scum vinyl owner

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    yeah, I managed to find them just after I posted. glad to get a recommendation, as it were. wasn't sure of the practicalities of attempting to insert an M2 insert into hardwood, so I had a look at an alternative solution;

    a collar with a 1/4" int diameter such as this sort of thing:

    http://www.mtmc.co.uk/Collar-Packs/T...810-39092.aspx

    I should be able to epoxy it into place

    might try both to see what works best
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    Ah I get ya there re the collar. Top tip if you go the insert route. Drill a pilot hole a smidge bigger than the insert diameter before you drill the pilot hole for the thread insert. This makes life easy for getting the insert in square to the pilot hole otherwise you will be going straight in at a tangential point which can be a bastard. Personaly I would go the insert route but have a play with pilot hole dias as I've often found recommended pilot hole size to be too tight.
    Elitist scum vinyl owner

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    That collar's the best idea.
    Si.

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    Cheers Si, that's what I thought. Once I get a bit of a chance to play with the woodworking lathes I'll have a go at turning some knobs. Quite fancy some Bubinga, but I think I've got some Purpleheart and some Maple left over from the bowl blanks I bought for doing guitar headstock veneers.
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    Looking good there! if you want a better sounding pot you could try one of those miniature DACT (stepped attenuators) on ebay. They well beat a carbon pot to my ears.

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    To be honest, I'll probably go the pseudo shunt route; probably a lot cheaper. I'll need to order up a pair of nice 91k resistors to go with the 100k pot....
    "It's ok your comments are noted, so if you want a war you've got one. Watch your back, ya !!!!...." in an email from Marco 3/4/09

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    Not a lover of purple heart, don't like the colour but maple is nice is you don't have any bubinga. I've seen a few bits made from bubinga and I like the warm colour.

    Best sounding pot I've tried to date is the Tocos from hificollective http://www.hificollective.co.uk/cata...keywords=tocos I'm on my third one, the first replaced an unbranded stepped attenuator though it was all Dale resistors, the second replaced a pair of mono Dact attenuators and the third is sitting in my B4 preamp. I've tried TKD and Noble which are both excellent pots and I reckon the Tocos is easily on a par. The improvement over the Dacts was substantial and all for twenty two quid
    Si.

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    Quote Originally Posted by cartridgemangler View Post
    To be honest, I'll probably go the pseudo shunt route; probably a lot cheaper. I'll need to order up a pair of nice 91k resistors to go with the 100k pot....
    You won't get full output with a shunt. No problem if you've plenty of watts to spare.
    Last edited by Chops54; 28th November 2013 at 17:18. Reason: spelling
    Si.

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    I'm not keen on shunted pots but if I had to, I'd use a cermet linear pot and metal film resistors to shunt it (fake log).

    Better would be a straight 20k log pot. I have 10 and 20k Tokos pot's and although I prefer them to Alps Blue, I find the miniature DACT pots better than all I have tried so far. There is still a bit of a veil with the Tocos pot's and channel balance is not as close as the DACT gets.

    FWIW I paid not much more for my DACT pots than I did for the cheapest carbon one and I prefer the sound of the DACT but it's a personal taste issue as usual. Some folks like a pot to bring a bit of warmth/colouration to the sound, others see that as the enemy.

    Pots - cheapest I could get and no fakes.

    http://www.ebay.co.uk/itm/1908494312...84.m1439.l2649
    http://www.ebay.co.uk/itm/140437348649

    This guy is good for valve amp parts, I got some nice Teflon insulated wire from him recently which would be good for hook-up in your amp.

    http://www.ebay.co.uk/itm/3806618114...84.m1438.l2649
    Last edited by davym; 28th November 2013 at 20:52.

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