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Nov 18, 2008 18:36:29 GMT
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Been messing today, trying to get this project finished. Its just lashed together, 'breadboarding' its called, now it works ill build it properly. Its a valve phono stage for my TT, lots of exposed 380v goodness in there, enough stored in the caps to kill even 5 mins after switch off. It will be a relief to get it built into a case ;D  Thought i'd share incase anyones interested. |
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Nov 18, 2008 19:55:16 GMT
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ive no idea what any of it is, but it looks good and dangerous. i approve.
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"quote hairnet"
I'm not paying nine pound for a pi$$!
[/quote]
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Nov 18, 2008 20:39:06 GMT
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I love anything like this - I've built an amp for a mate just the other day out of "bits" lying about - It's only about 30wpc but he had a pair of capacitors the size of 500ml beer cans, so I used those for the PSU smoothing after the rectifier. It just needs a decent toroidal to finish, the amp chip (Class D, sounds surprisingly good for £4, if a bit bright) will only take 45v or so, and my only scavanged transformer is 80v.
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Last Edit: Nov 18, 2008 20:39:40 GMT by cobblers
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Nov 18, 2008 21:04:14 GMT
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I like the bare 380V goodness...
A bleeder resistor across the supply caps would be a good idea. Although looking at the PSU is looks as though you may have on already.
Does it sound ok, then?
2 transformers, filament and HT, CLC filter on the HT with regulated heater supplies, no?
I'd guess that the input to the amp would be on the left, away from the power input, except for what looks like a shielded valve on that end - EF86?
I've a small collection of valves and a few transformers (2 output, 2 power) to build an amp - it's not happened yet, but will over my christmas break.
James
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Nov 18, 2008 21:40:43 GMT
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Thats about the size of it, no shielded valves though, the larg (ish) black things are all capacitors.
Sounds OK, but not as good as it should, but then its just lashed up on a board.
Built it to see if i could, now i know i can ill rebuild it properly
Mostly built out of scrap and a few donations from other forum members.
Its a very well regarded phono stage, available in kit form for £450 ish but i don't have that kind of money.
I think this cost me about £40.
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Nov 18, 2008 23:35:54 GMT
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where do you find the info on doing this sort of thing? I have some old valve equipment I'd like to ressurect, but would love to know where to start
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Remade In Australia
thereimaginarium.com.au
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Just search the net and joint Valve audio forums, well, the DIY ones anyway. DIY audio is a good start, mainly US members though www.diyaudio.com/I'm just starting with this kind of thing. |
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Nov 25, 2008 13:47:24 GMT
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, lots of exposed 380v goodness in there, enough stored in the caps to kill even 5 mins after switch off. It will be a relief to get it built into a case ;D Thought i'd share incase anyones interested. its amps that kill not volts. volts hurt like hell , amps finish the job. average mega tester runs at 500v , had a few belters off them ( and gave a few to my work mates too). |
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Nov 25, 2008 15:17:13 GMT
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Or as they say at work "Should I mega him?" "Yeah mega the git he got me last week!"
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Nov 25, 2008 18:11:18 GMT
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Megger, not Mega, IIRC.
That PSU can probably sustain 10 to 20ma at over 300V, and provide much, much more in a burst from the capacitors if necessary.
Suffice to say that it's very dangerous. It's less dangerous than it would be if it had no HT transformer.
Some old valve radios just rectified the mains, with no transformer. The metal chassis would be connected to the -ve of the output, rather than safety ground. If the mains plug was not polarised, or was polarised but inverted, then the chassis would be live (at a couple of hundred volts) with respect to safety ground - if you touched it then it could very easily kill you.
This is dangerous if you use both hands to adjust or measure something on the circuit while it's live. Keep one hand behind your back, and insulate yourself from ground as best as possible (in a complete reversal of ESD procedures) then at worst you'll get a nasty shock.
James
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Dangerous Hi FiDeleted
@Deleted
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Dec 25, 2008 12:25:08 GMT
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Yup, my valve amp psu pumps out over 400V DC and will supply 150mA. It will kill you.
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Last Edit: Dec 25, 2008 12:25:27 GMT by Deleted
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