Lampy cd player

[Richard]

Hi all,
Always fancied trying this.
I've only had a quick look around and see loads of posts here so I'll try not to go over old ground and ask stuff that's been covered before but sorry if I do.

Heater supply questions;
I've done a reg heater supply but don't have lot of practical xp with them. The draw will be 2 x 6n2 valves but maybe 2 x 6n1 valves later so 0.6A or maybe 1.2A. There's a single LM1084 reg. How big a heatsink will it need? I've done it on 4 sq inches of ally at the mo and can bolt some more to it if needed but want to avoid cooking it on the first outing . Will post pics soon.

Secondly, the TX has 2 x 9V 1A outputs. One winding would be fine for 0.6A but not 1.2A. Thoughts are to parallel the windings into the bridge rect now, so it will handle either valve later, but does phasing matter ie which way around the wire pairs are connected? I can see that series might change the voltage but can't quite get my head around parallel.

[pre65]

Transformer wiring has been known to make my brain hurt.

What colour are the four secondary wires ?

[Nick]

OK, first thing, heatsink.

9v supply will give 12v ish after rectifying. If its to feed 1.2a at 6.3v then the regulator is dropping 5.7v, so thats 7W to dissipate. From the datasheet that dissipation needs a heatsink of less than 15.9C/W (assuming 1C/W with a insulating pad).

Normally, I would just bolt it to the case with a thermal pad and that will be good enough.

As for the transformer, as you say, they need to be corrected in phase. The lead-out on the transformer will normaly be in phase order, so if it says (for example

SEC 2x9v @ 2.76A RED/YELLOW - BLUE/GREY

I would connect red and blue together for one feed and yellow and grey for the other

[simon]

Two separate regs, one per secondary? The reg chips are cheap as, well, chips, and they'd be doing less work so less issues with heatsinking?

[pre65]

My 9V toroids (50va) are

Black - Red........Orange - Yellow
0v------- 9v............ 0v-------9v

So Black/orange together and Red/yellow together for parallel.

[Aardvark]

Presumably if the two windings were connected together parallel and out of phase, they would cancel giving little or nothing of Vac potential difference. So twisting the wires together and whacking the meter across it will confirm it straightaway.

Or have I made a typical novice error ?

[Nick]

Yes. I always worry that something bad will happen, but they are out of phase so it should just do nothing.

[Dave the bass]

My 9V toroids (50va) are

Black - Red........Orange - Yellow
0v------- 9v............ 0v-------9v

So Black/orange together and Red/yellow together for parallel.

<Pedant mode engaged>

Surely thats 9V AC across the windings.... one side does doesn't know it's called '0V'....

Ha! </pedant mode>.

DTB

[pre65]

My 9V toroids (50va) are

Black - Red........Orange - Yellow
0v------- 9v............ 0v-------9v

So Black/orange together and Red/yellow together for parallel.

<Pedant mode engaged>

Surely thats 9V AC across the windings.... one side does doesn't know it's called '0V'....

Ha! </pedant mode>.

DTB

I know what you are called.

I was only copying what was on the transformer label.

[Dave the bass]

I know what you are called.

Heheheheheheheheheh!

DTB

[Richard]

Ah, but this is a special chinese transformer with both wires in the secondary pairs the same colour... a pair of grey and a pair of black... and the cdp has a plastic case

So, fitted the tx and wired the primary to the mains, ouch, Mr Lampizator says those 2 connections are after the switch and fuse, after the switch yes, but took the fuse out and the valve supply is still live, better watch that. Checked the circ and can see what he's done, kept the fuse for the cdp and switched but not fused the valve supply. Left it that way as the cdp will then be protected by the 160mA equipment fuse and the valves by the 5A plug fuse. Perhaps just his words aren't clear.

Seried the grey and black pairs with a volt meter on the ends; one way 22V the other way 0V, checked each secondary individually and yes 11V each winding unloaded so that's ok and I marked them for phase.

Then parallel; I didn't know what to expect for sure either, answer is 11V paired together in phase no problem but lots of flashes the other way clearly shorting the output and no need to put a meter on to see it would be 0V but I didn't keep it connected to find out what happens long term or try and guess where the energy goes. So these phasing connections are pretty much like batteries connection-wise.

Anyway it's good I'll pair tham in phase for 2A, got a 2A bridge and 5A reg so the supply should be good then for both valve types.

The heatsink is still an unknown, I'd bolt to the case normally, commercial heatsinks don't look massive so I'll run it and see how it goes for an hour or two I suppose, will let you know

[Richard]

OK, first thing, heatsink.

9v supply will give 12v ish after rectifying. If its to feed 1.2a at 6.3v then the regulator is dropping 5.7v, so thats 7W to dissipate. From the datasheet that dissipation needs a heatsink of less than 15.9C/W (assuming 1C/W with a insulating pad).

Normally, I would just bolt it to the case with a thermal pad and that will be good enough.

As for the transformer, as you say, they need to be corrected in phase. The lead-out on the transformer will normaly be in phase order, so if it says (for example

SEC 2x9v @ 2.76A RED/YELLOW - BLUE/GREY

I would connect red and blue together for one feed and yellow and grey for the other

Hi Nick, thanks for the appliance of science Checking those commercial sinks is a good way to learn. Sinks around that rating seem to be about half the area I've gone for so it should be ok, if not I'll bolt some more on the back.

[pre65]

Richard, I've become much more interested in this topic now as I'm thinking of doing something similar to my Shek DAC.

What circuit are you using on yours ? I presume not the cathode follower variation.

EDIT. I've found the anode (plate) follower circuit now on that link you gave earlier.

[Richard]

Hi Philip,
It's 1541 dac so I'm following what Lukas feels is the best he's found so far, 6n2p circ, http://www.lampizator.eu/LAMPIZATOR/REF ... G_5501.jpg
I'm making the psu universal and have now built the circuits on the valve holders so it will be easy to try the 6n1 or others such as Thorsten's ecc88 just by swapping valve holders.

So far, in this order, I've spent a week or so with the standard player with LM833 opamps, swapped the opamps to 2604, swapped out the dac and a few other caps, then went to NOS.

Now fitting the valve stage which will use passive I/V with a 82R to start and Lukas' 6n2p stage which is not really srpp (I don't think he refers to it as such) and uses the top section as a ccs with output from the anode of the bottom valve. I do have thoughts about the output impedance and will keep the i/c short but he's got vastly more exp than I ever will have and I can move on if there's something better. I do want to do a frequency check when that's in place though to check it's at least in the right area.

[Richard]

Guys, a little help again, I'm finishing this circ but the op impedance is still niggling me. I could calc it for a single valve but is this affected by the top triode and can you give me a pointer or even estimate it if you have prior xp. The proof of the pudding etc but that will be a day or two away, thanks,