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Old 21st May 2013, 06:05 AM   #1371
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If it is a non center tapped HV winding then yes.
If it is a centre tapped winding then no.
You need a tube diode element in each [winding to rectifier to storage capacitor] circuit so that you can not get SS diode switching noise from reverse conduction as the SS diode switches off.
As the voltage on a SS diode reverses, you get a "splat" of current in the reverse direction which is basically sweeping out the charge of the SS diode junction capacitance. Once that charge is swept out then diode is then properly OFF and no current flows. It is that "splat" of reverse current which IS the SS diode switching noise. It couples horribly back through the transformer to any other windings. The tube rectifier does not allow that reverse current "splat" to happen.

ASIDE: The difference between standard SS diodes and the Ultrafast / Soft Recovery types is that that junction capacitance charge is 5 to 10 times smaller (so the reverse current "splat" is 5 to 10 times smaller too). Schottky diodes junction charge is 5 times smaller again.

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Old 24th July 2013, 09:24 PM   #1372
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Default Ouput and power transformer advice

I think this is going to be a great project to get a friend into tubes .

The project Wiki is excellent, but I have some questions. I've read 30 pages or so of this thread, and now my brain is about to pack up and leave . I tried the search function but got scattered results. Accordingly, I apologise if my questions have already been answered.

Getting ahold of transformers here can be difficult. One supplier does bring in a limited range of Hammond stuff though. Is the Hammond 1608 good enough for the OPTs? I can also get the 1620 and 1650H.

As for the power transformer, I'll probably have to get toroidals wound locally. Should I consider getting 3 separate transformers, or one with 3 voltages? What are the individual VA requirements for 5V, 6.3V and 330(?)V

Thank you everyone!
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Old 25th July 2013, 06:10 AM   #1373
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Hammond 1608 are the Output trannies I'm using on the Baby huey on my HiFi Syatem.

Here is something I posted earlier:

"In my on-going efforts to "convert" the youth of the world to Hollow State my apprentice at work has just finished building a fixed bias version of the Baby Huey for his home HiFi.

He wanted to use a single power supply for both channels and use readily available Hammond Trannies.

Here is what we came up with for his amp:

Power Supply (for 2 channels).
Power Transformer - Hammond 370HX (275-0-275 V @ 200mA).
Solid State Rectifier Diodes (Ultrafast Soft Recovery)
"C-L-C" arrangement power supply.
10uF/900V Polypropylene first capacitor.
Hammond 158S (1.5H 250mA 60 Ohms DCR) choke
470uF/450V final electrolytic with 5uF/900V polypropylene in parallel for the 2nd capacitor.
This gives a rock solid 330V rail - just right.

Hammond 1608 Output Trannies.

Notes:
The 900V polypropylene for the first capacitor is an overkill. You don't need a fantastic quality cap in this position.
The Ripple Current for this capacitor (according to PSUD2) is 320mA RMS
A Panasonic ED 10uF/450V has a 350mA RMS ripple current rating and could be used instead.
BUT
I would instead RECOMMEND using 2 off Panasonic ED 22uF/200V in series, with 220K voltage share resistors (1 or 2 watt) across each capacitor. These caps have 600mA ripple current rating which means a far longer lifetime.

For the cap in parallel with the 470uF/450V second capacitor, any 630V rated film cap of 2.2uF or 4.7uF would do. Polypropylene for preference but even polyester will be better than no parallel cap.

This supply would suit either the original (CCS biased) or the fixed bias versions of the Baby Huey."

Hope this helps

Cheers,
Ian
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Old 27th July 2013, 02:00 AM   #1374
fmena is offline fmena  Canada
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Default My first scatch build ... so far

Click the image to open in full size.

Using plywood as a bread-board of sorts for now. Still learning as to the best placement as to where things go. Will move to a metal enlcosure. Plan is to have a separate PS and feed separate mono-blocks via umbilical as my shelf space is very limited as to where I can place things.

Learning lots as I go as this is my first scratch build & it is really slow going but lots of fun.
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Old 1st August 2013, 06:36 PM   #1375
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Thank you gingertube, that helps a lot
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Old 21st August 2013, 08:42 AM   #1376
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Quick question (and deal-breaker in my case) - can this easily be triode strapped or otherwise? My transformers cannot be used for ultra-linear, and I'm not experienced enough in this field (yet) to make modifications of my own.
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Old 21st August 2013, 09:49 AM   #1377
Yvesm is offline Yvesm  France
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Just use plain penthode mode, original schemo was done for that !
Triode strapped kills the efficiency of local feedback and reduce available power a lot.

Yves.
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Old 22nd August 2013, 07:52 PM   #1378
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Quote:
Originally Posted by Welcome View Post
Quick question (and deal-breaker in my case) - can this easily be triode strapped or otherwise? My transformers cannot be used for ultra-linear, and I'm not experienced enough in this field (yet) to make modifications of my own.
The design already has local NFB included, and Ultralinear looks like overkill here. I'd take Yvesm's suggestion to do without and run straight pentode mode. If you're feeling adventurous, and have an OPT with a multi-tapped secondary, you could consider cathode feedback instead.

Neither is strictly necessary, as you can always adjust the gNFB to compensate for the missing Ultralinear NFB, if that's even necessary.
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Old 22nd August 2013, 08:20 PM   #1379
Yvesm is offline Yvesm  France
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Remember where all that comes from !

Push Pull ECL86/6GW8

Yves.
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Old 23rd August 2013, 08:43 AM   #1380
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Thanks for the info guys. That settles it then. I'm building this.

By the way: How do you feel about using this valve in place of the ECC803s?

ECC83S / 12AX7 JJ :: JJ Standard :: JJ Tesla :: Tubes :: Banzai Music GmbH
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