Darren 212 / 833 SE amp
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Paul Barker
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#77
Although it has to be said that Greg's amp and speakers demo'd at a previous eggfest in a rush before had to go also handled organ music beautifully.
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Paul Barker
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- Posts: 8985
- Joined: Mon May 21, 2007 9:42 pm
#79
Let's start again.Nick wrote:And if I remember, you said they were powered by a PP el84 amp...
Yes cathode follower output stage.
The cathedral organ style bass was from a subwoofer about the size of an organ.
#80 833 Heaters...
Paul, Nick
I'm looking to set up some heaters for the 833s for a "proper" build and get away from those enormous Farnel supplies.
Requirements are 10V @10A
So considering some toroids I need to determine the voltage I may require.
We can all do the math, but there's nothing like real life experience.
My question is "how would you do it" and mainly what voltage transformers would you be looking for?
They are not likely to be cheap, so I'd like to get this right.
Best wishes
Darren
I'm looking to set up some heaters for the 833s for a "proper" build and get away from those enormous Farnel supplies.
Requirements are 10V @10A
So considering some toroids I need to determine the voltage I may require.
We can all do the math, but there's nothing like real life experience.
My question is "how would you do it" and mainly what voltage transformers would you be looking for?
They are not likely to be cheap, so I'd like to get this right.
Best wishes
Darren
#81
20v 3A is the limit I have managed to regulate well. I would start with the regulator circuit you intend to use and go from there. I sort of think the transformer will be the simple bit.
That does assume you intend DC heating. Maybe at 10v AC would be usable.
That does assume you intend DC heating. Maybe at 10v AC would be usable.
#82
Hi Nick,
I have read others have tried AC but the fillament bounces around like a good un and thus massive hums.
I did rig up a LM317 once controlling a a much larger device, forget the number now. I'll have a look for it later.
Was wondering if I could get away with say 12V simple rectified and smoothed with caps. Just for the sake of simplicity?
10A is a lot to cope with and no doubt is the bigger of the problems.
I have read others have tried AC but the fillament bounces around like a good un and thus massive hums.
I did rig up a LM317 once controlling a a much larger device, forget the number now. I'll have a look for it later.
Was wondering if I could get away with say 12V simple rectified and smoothed with caps. Just for the sake of simplicity?
10A is a lot to cope with and no doubt is the bigger of the problems.
#84
Yep, they are DHT's. And A CCS would be better, but that makes it possibly harder. I managed to drive a gm70 at 3A that way, and even that needed a chain of zeners across the regulator to top it either blowing up on turn on or sulking and not starting.
I wonder if you can parallel current regs, if they each have their own sense resistor I would think it was possible. Have 6 set for a fixed 1.5A, then a seventh adjustable to trim the voltage across the valve.
I wonder if you can parallel current regs, if they each have their own sense resistor I would think it was possible. Have 6 set for a fixed 1.5A, then a seventh adjustable to trim the voltage across the valve.
#85
How about adapting something like this? Could alter the voltage output and it would be cost effective.
http://cgi.ebay.co.uk/DC-Netzgeraet-Tra ... dZViewItem
I use a 5A one on my phono and it's as quiet as a car battery.
http://cgi.ebay.co.uk/DC-Netzgeraet-Tra ... dZViewItem
I use a 5A one on my phono and it's as quiet as a car battery.
#86
This could also work?
http://cgi.ebay.co.uk/250W-12V-20A-Swit ... dZViewItem
Anybody tried switching supplies? Come to think of it didn't some of us try lighting transformers in the past. Still have a box of them somewhere but I seem to remember we needed to modify them and they weren't reliable. Didn't switch on sometimes.
http://cgi.ebay.co.uk/250W-12V-20A-Swit ... dZViewItem
Anybody tried switching supplies? Come to think of it didn't some of us try lighting transformers in the past. Still have a box of them somewhere but I seem to remember we needed to modify them and they weren't reliable. Didn't switch on sometimes.
#87
Yep, Paul worked out the mods to get them to work, and I did some more work, and got them to start every time. Actually they would always start, as long as the load was enough, and they have been powered down from a previous under load (the input cap needed to discharge).
They were a very efficient way of heating GM70's. and I used them initially on the 211, but to my ears they broke the treble. I only got them running at 50kHz, maybe a higher frequency would have been better.
They were a very efficient way of heating GM70's. and I used them initially on the 211, but to my ears they broke the treble. I only got them running at 50kHz, maybe a higher frequency would have been better.
