robin

el spuddo amp-come on you diy experts- HELP PLEASE

58 posts in this topic

haveing got these from smegol, they sound really,really good with my kora mandalas 94db 4 ohm, but whay their out put is im not sure- how they is the the single valve to each mono block that is very small and i have never heard of it,its a 6c45- upside down u- e ,also has 1181 on it the valve in the power supply is a rectifier i think ez 81- pics and futher questions follow- any advice or observations very welcome[ATTACH]3718[/ATTACH]

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this post can be turned left or right could it be a bias control or even a feedback control[ATTACH]3719[/ATTACH]

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i have got a joiner makeing some mdf boxes to slide these into but would like to add a on/off switch on the power supply and a led on all 3 to show when their [ATTACH]3724[/ATTACH]o[ATTACH]3723[/ATTACH]n[ATTACH]3722[/ATTACH]

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ta mib,

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DEALER

The circuit, or something like it at least, is here http://www.hornet.hr/SM/Brian.htm

The "post" will be the bias pot (potentiometer) I imagine. Assuming it's set right at the moment don't twiddle it unless you've got a meter to check the cathode current and an idea of what current you actually want.

The MDF boxes sound like a very good idea, if only to keep body parts away from the exposed high voltages (let's not mention the Electrical Equipment (Safety) Regulations 1994 shall we - oh dammit, I've mentioned them :doh:). But don't forget that although these valves are small and the heaters don't amount to much, the amps are running in Class A and there is a tendency to run them hot. So leave a bit of room inside for the air to circulate and don't forget some holes to let cool air in and hot air out.

One last thing - make sure the earthing and fusing arrangements are OK. Loads of things can go wrong with homebrew kit, but as long as it's boxed up and properly earthed and fused you'll be protected from the worst consequences of most of them.

I have to say I envy you. I was sorely tempted by these and had I not just splashed out on the Dynaco and on a load of iron to make some Mullard 5-20s then I'd have fallen for them :).

Valvebloke

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cheers valve bloke,

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just had another suprise, the one input into these is xlr i moved it into my lounge and put the moon equinox on, but this is phono only, with the bag of wires that came with this was a pair of weedy looking xlr to phono leads, it sounded crap, underpowered bloody awfull, so got the lygdorf with missing link xlrs, and as on sunday with smegol sounds superb, so dont know if its the i/cs or the cdp but total night and day, if i had heard it with the moon i would never have bought it !!!!1

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im also a bit worried by uninsulated wires like this touching to earth ect[ATTACH]3733[/ATTACH]

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It looks like the builder never got this out of the design phase. It may sound good but it looks bloody dangerous as is. if it were me i would case and cage.... which is a lot of work.

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im getting that sorted watch this space :love::love:

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Hi Robin

The power lead fitting is a Powercon fitting but the outputs to the monobloc's from the power supply are speakercon not designed for high voltage use or so I was told by a supplier,he said they should be changed along with the sockets on the amps to comply with safety regs.You may want to check this out,he was saying something about having a duty of care.

Vinnie.

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DEALER
just had another suprise, the one input into these is xlr i moved it into my lounge and put the moon equinox on, but this is phono only, with the bag of wires that came with this was a pair of weedy looking xlr to phono leads, it sounded crap, underpowered bloody awfull, so got the lygdorf with missing link xlrs, and as on sunday with smegol sounds superb, so dont know if its the i/cs or the cdp but total night and day, if i had heard it with the moon i would never have bought it !!!!1

If it sounds really bad with the weedy leads then it could be that there's a problem with the 0V connection inside them. This is sometimes cut to avoid ground-loop noise, and you can get away with it if there is another good-quality 0V link between the power amp(s) and the source (or pre, if there is one). If there isn't a good 0V link though, then the signal path can end up being made just through stray capacitance, which can make the sound truly dreadful. Given that you've got transformers on the inputs it's quite possible that these amps do need a solid 0V connection in the interconnects.

One other thing. I notice that in the pictures in post #1 the power valves have screening cans on them. I'm surprised at that. They shouldn't be particularly sensitive to noise, which is what the cans are usually there to reduce. But they will need proper ventilation to stop them overheating, and cans really do ruin the ventilation. I'd take them off and if the amp runs quietly enough without them then I'd leave them off.

VB

Edit - I've just realised the XLRs on the amps might be wired for balanced input, in which case you can get the same sort of effects as above if the RCA-to-XLR leads don't follow the same wiring convention as the amp connectors do. Again it's an interconnect issue.

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cheers vb:^

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Hi Robin

The power lead fitting is a Powercon fitting but the outputs to the monobloc's from the power supply are speakercon not designed for high voltage use or so I was told by a supplier,he said they should be changed along with the sockets on the amps to comply with safety regs.You may want to check this out,he was saying something about having a duty of care.

Vinnie.

cheers vinne, i take your the first wam owner of these, do you have any idea of the output power, is it supplied from the single valve or are they a hi-bred design

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