DHT Heater using VCCS - PCB or Kit (Possible Group buy)

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Andrew
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DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew » Thu Feb 21, 2013 8:41 pm

Same deal as the last one chaps, this will be a heater PCB/Kit that specifically designed for DHT, it will use a voltage reference to set the final voltage and provide a constant current that equals the voltage required by the valve being heated. No tweaky pots on this design ;)

There is no need to adjust when changing valves, only for differnt types. It will be suited to DHT up to and including 2.5A (unless I hear lots and lots of shouting for more), most reasonable voltages shouldn't be a problem.

300B, 45, 2A3, 76 etc are all OK.

The circuit is based upon Voltage Controlled Current Source aka VCCS (http://en.wikipedia.org/wiki/Current_source), voltage is set by two resistors. As its a current source it won't interfere with the precious signal, slow start is also incorporated. Board is standalone, just add TX and required resistors.

The test unit is on my bench, listening tests are planned for this weekend, if that works out, all being well, I'll be looking to build the first PCB prototypes over the coming weeks. I'll keep you up to date as works progress.

Final price will be in the £10-15 range for the kit, least that's what I'm planning, again I will keep everyone up dated as I progress, a great deal depends upon numbers, the more the cheaper, as well as how many prototype PCB revisions I have to make (aka cock ups).

Please register initial interest and propsoed valve type so I can get a feel for numbers, voltage ranges, and hence cost.

thanks,

Andrew
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IDM
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Post by IDM » Thu Feb 21, 2013 9:06 pm

Hi Andrew,

I would certainly be interested in at least a couple.

what are your listening tests going to compare against? My recent 2A3 preamp trials led me to read lots about different DHT modules. Consensus seemed to be that the Rod Coleman was the best, followed by Tent Labs, with DIY hifi supply least favoured.

Cheers
Ian

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Paul Barker
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Post by Paul Barker » Thu Feb 21, 2013 9:11 pm

10v 3.25 amps would just get it into 211 camp.

But in any case it will manage the 801a which would be enough. Don't worry if it can't do 211. But if it isn't too much of an alteration it would be nice.

I'll have 4 at least.
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Post by Andrew » Thu Feb 21, 2013 9:16 pm

I don't have any of those to compare against, sorry in essense that's the driver for doing this project. I am simpy looking for others so I can get price breaks on the PCB and parts, as well as get feedback.

I do have a pair of high quality bench PSU that I am currently using, and I am very happy with the PSU's sound but they are only good for a breadboard. The PSU I am using can be set to run in constant current mode, so these are my reference. I plan to go ahead if I can't tell the differnce between the PCB and the bench PSU.

Andrew
Last edited by Andrew on Thu Feb 21, 2013 9:57 pm, edited 2 times in total.
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Post by IDM » Thu Feb 21, 2013 9:19 pm

I have the Tent Labs in my 300B set amps and the Rod Coleman boards in my 2a3 pre (assuming I solve its issues!!!). So might be able to give some feedback.

Cheers
Ian

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Post by Andrew » Thu Feb 21, 2013 9:21 pm

Paul Barker wrote:10v 3.25 amps would just get it into 211 camp.

But in any case it will manage the 801a which would be enough. Don't worry if it can't do 211. But if it isn't too much of an alteration it would be nice.

I'll have 4 at least.
I plan put a 4A diode bridge on these ones, just for you Paul, but I have yet to test that part of the circuit. I remain optimistic of a good spec but until I test it, I can promise nothing. This is just to gauge interest. The proto I have is happy driving 4R load at 5V and barely gets warm, but its a bitsa, next rev will be using planned final parts and layout, I do, however, plan to see how far I can push it.

Andrew
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Post by IslandPink » Thu Feb 21, 2013 9:31 pm

If you can do something that doesn't burn too much power ; something similar in overall spec to Guido's units, then I'm in for at least six .

Will these just be quiet enough for output valves, or can you spec them for driver/pre-amp use ?
I have need for some for 45/2A3 and some for 4P1L as a driver.

Most impressed anyway - beers at the next Owston for you , fine fellow :D
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Post by Andrew » Thu Feb 21, 2013 9:45 pm

I'll put up some measurements tommorow, or over the weekend. Should be fine for all use I guess, on my initial attempt the noise is about 80db down (but that's to be confirmed).

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specs

Post by IslandPink » Thu Feb 21, 2013 9:58 pm

For info -
http://www.tentlabs.com/Components/Tube ... index.html
See 'specifications' and 'available versions' .
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Post by Andrew » Thu Feb 21, 2013 10:08 pm

Well my calculations say I am 10x better, -80db on a 200mV scale, .200/10000 2 x 10^-5 whereas Tent Labs is 200uV =200/1,000,000 = 2 x 10^-4 is so I am going to do them again, cos I didn't expect it to be better. So my first thought is its too late at night and I'm wrong, let me confirm.

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Post by Andrew » Fri Feb 22, 2013 8:48 am

Andrew wrote:Well my calculations say I am 10x better, -80db on a 200mV scale, .200/10000 2 x 10^-5 whereas Tent Labs is 200uV =200/1,000,000 = 2 x 10^-4 is so I am going to do them again, cos I didn't expect it to be better. So my first thought is its too late at night and I'm wrong, let me confirm.

Andrew
OK, this was a bit unfair as I'm ppowering the prototype from a bench PSU, so, in effect a pre-reg, I'll rig up a cap and 4 amp rectifier tonight and measure again.

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Post by IslandPink » Fri Feb 22, 2013 9:45 am

It'll be interesting to have a breakdown of (i) hum ~100Hz and (ii) 'Other' .
Some applications like horn/tweeter amps are not bothered by the hum .

Please try to get the whole package including rectifier on one board - I imagine that would be your goal .
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Post by Dave the bass » Fri Feb 22, 2013 10:12 am

Yes please MrL, I'd have a couple at least.

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Post by andrew Ivimey » Fri Feb 22, 2013 10:28 am

four for me too please , Andrew; no, really!
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Post by Bizzie » Fri Feb 22, 2013 12:21 pm

Two for me please Andrew.

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