Salas hotrodded blue DCB1 build

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thanks! is it safe to keep them above 60c? Anyway I was planning to attach them to the chassis.


Its true those diodes have a high 175C internal junction break point, but electronics do last 4 times longer each time you halve their operating temperature. So don't be much afraid for them during testing but help them when finishing the build because it is likely they are going to live in high ambient in that hot rod box. For the electrolytics, especially the big ones,they will fair best if 105C rated.
 
..............0.71 1 W/(m.K).......for Mica and .............0.6 for Kapton......or even 0.12
note the units, W/mK
The 0.71 looks like the highest Watts. That makes it the best. But you must also take account of the thickness.
Mica generally comes in thicknesses varying from 1thou (1mil= 0.001") to 6thou (6mil = 0.006")
Kapton tape in thickness varying from 1.5thou to 6thou.
Coated Kapton in thickness varying from 3thou to 9thou.

The very thinnest mica outperforms all the coated Kaptons and is just about equal to a gooped Kapton of 1.5thou if you can find any uncoated Kapton tape that thin. Uncoated Kapton will need goop on both sides. Makes it just as messy as Mica.
 
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Put evrything in the case and attached the fets with metal bolts, closed the lid and let it warm up for about 40 mins. So here is what i got:

-1.87 & 1.97vdc across 3ohm R
-0.01 & 0.09 mA offset
-10.79 & 10.79 vdc output
-42c on the fets
-about 40c on the sinks (barely warm when I touch them)
-62c on the surface of poor little toroid placed out of the case

The whole case i kind of a heatsink. I didn't use any thermal paste yet. The are ventilation holes only on the top lid, so I assume need to add some to the bottom...

How more may I torture this little toroid, is it safe to put another 6R across, making it close to 1A per rail?! I do not have any spare transformers, only if I borrow 100VA 2x18vac from MyRev FE, but I'm not sure if that is a good idea and would give similar result as with a decent 2x15vac toroid.

Another question is how far could I go with these heatsinks and what toroid to buy in the end. As it should be less than 78mm in diameter according to my layout, this narrows the choise to <80va toroid or I should be looking for R-core (65w and it would suit the case) like this one. Alternatively some custom toroid, 50-55mm in height needs to be found.

Btw, sorry for probably stupid question :D but is it possible to connect 2 x 50va transformers in some way?! That woul solve the problem :)
 
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I finally wired everything together on the chassis. That thing ended up HEAVY!!!

First impressions with the Caddocks are very very very very very very positive :)
Although having everything securely screwed on that dense and heavy chunk of metal and wood might also played a part.

Imaging and separation are in a completely new level. Mids are amazingly sharp and precise. It sounds a bit shy on the mid-lows, but it is probably the fresh soldering/wiring. It will show in a few days.

With no lid on and after 2 hours the temperature on the fets is 48C which is very close to what I wanted. The heatsinks stay at about 35C. A properly vented lid should not create any additional issues. I am thinking glass or some more wenge.

What troubles me a bit is the wire spaghetti because of the pot on the front and the DPDT switch on the back for the source selection (That one is a switchcraft and is of very nice quality (a bit pricey though)). I bet that with shorter and better separated wires the results would be better... Even better with a dual mono build but... meh...

The only thing remaining for now is to properly drill the knob and install it.
Oh and do something about that damn white led which is too bright :)

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@dtses
You could attempt 1A it looks like with your now sinking and measured temps. The limiting factor is your little hot transfo obviously. 2x18V forget it, the spare voltage will convert to high heat on the CCS and sink. Ebay R-Cores are a gamble. When made right its the best solution, when not, a downright failure for heating and buzzing. Feeling lucky on the one you linked? China is slow shipping lately except HK have in mind. About the using two little ones question: You can in general stack or arrange side by side 2x15V 50VA toroids (or any other type) and wire them in parallel. There are restrictions when paralleling though. Thus they should be coming from the same manufacturer and be same model having very low tolerances between them, and they should be wired with same magnetic polarity. Toroid's central screw should not touch the top lid. If it will you are for witnessing a catastrophic magnetic short. But you already have 630mA on average which is decent hot rod in the compact. Another option would be a 100VA single toroid in another box, saving you the hum field also. You decide based on discussed info.

@dimkasta
Nice.
 
Offset you mean mV?
A photo of the case should help us see any possible solutions to your trafo real estate problem.

yep, it's mV of course :)
I'll make few pics on this week later.

I finally wired everything together on the chassis.

what was the previous pre paired in you system with Elektrocompaniet?

... Ebay R-Cores are a gamble. When made right its the best solution, when not, a downright failure for heating and buzzing. Feeling lucky on the one you linked?

thanks, Salas! in that case I wouldn't consider any r-core at all :)
Thus they should be coming from the same manufacturer and be same model having very low tolerances between them, and they should be wired with same magnetic polarity.

that wouldn't be a problem I think. Thanks for the article, I'll take a look later.

But you already have 630mA on average which is decent hot rod in the compact. Another option would be a 100VA single toroid in another box, saving you the hum field also.

nahhh, I'm eager for some really hot stuff, at least 1.2A :D So that the whole case would be hot (about 55c, more as you've mentioned is not a good idea).
I was thinking about separate PS box, but then decided not to have one as my heatsinks would be definitely to small for 2A current and 200VA toroid that I would have put there :D I'll add some copper or Mu-metal for shielding if noise happens to be a problem.
 
Wow, very good, Dimitri. The box is a LOT bigger than I thought it was. Looks very good.

I like your description of the sound. You may have said earlier, but which Caddocks are you using? Have you tried the Vishay Z-Foil? I wonder how they compare.

I'm building a DCB1 at some point and am looking to hotrod it as well. I wonder how some of the more euphonic resistors, like Rikens, Kiwames, etc., fare in the critical signal positions?

Thanks for sharing!
 
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KT, I believe he is using Caddock Power resistors in the Power resistor position.
I think you will find that the signal section resistors 220,220k will take on a different sound signature with various resistors. I found carbon films to modify the sound too much for my taste, but others really liked the Takman's if there system was already too hard sounding.
 
Thanks KT :)

As Mike said, I use Caddocks on the PSU Rset position. They are MP930.
The signal ones are the PRPs that Mike included in the kit.

For the moment it's still breaking in and it sounds a bit over-analytic and harsh. I would love to get some more strength on the mid-lows to make me feel all warm and fuzzy inside :)

I have the Z-Foils and a better pot scheduled for a bit later, but if it gets a bit warmer in a week or so I would really consider leaving it as it is now
 
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Thanks KT :)

For the moment it's still breaking in and it sounds a bit over-analytic and harsh. I would love to get some more strength on the mid-lows to make me feel all warm and fuzzy inside :)

This was my reaction exactly - I built three and the one that was the least objectionable in this regard used Nichicon Super-through power caps and Amtrans resistors in the signal path. I didn't use anything special for R101.
 
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Thanks KT :)

As Mike said, I use Caddocks on the PSU Rset position. They are MP930.
The signal ones are the PRPs that Mike included in the kit.

For the moment it's still breaking in and it sounds a bit over-analytic and harsh. I would love to get some more strength on the mid-lows to make me feel all warm and fuzzy inside :)

I have the Z-Foils and a better pot scheduled for a bit later, but if it gets a bit warmer in a week or so I would really consider leaving it as it is now

Use thin coax shielded wire. Open signal cabling loop catches stuff. And there are toroids about. That buffer passes 150-200kHz square wave. That translates to near or over a MHZ -3dB depending on pot source impedance. Also the red caps are very influential, maybe you like 47uF to 220uF good electrolytic or another film cap there. Its just a Wima now.