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Old 5th February 2010, 10:58 AM   #511
adamus is offline adamus  United Kingdom
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re 1) have you tried this before, i know a lot of people dont recomment it stating various issues.

also is 10va enough for the salas shunts? there are pretty inefficient. salas recommends 30va if i remember correctly.
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Old 5th February 2010, 11:03 AM   #512
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Apelizzo,
are you sure to have found a cheaper solution using all these separated transformers ?

In any case use a 220:9+9 100w for the filaments and to drive a 9+9:220 50w to get also the 220V ac of anodic voltage is ok
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Old 5th February 2010, 11:05 AM   #513
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Quote:
Originally Posted by adamus View Post
re 1) have you tried this before, i know a lot of people dont recomment it stating various issues.

also is 10va enough for the salas shunts? there are pretty inefficient. salas recommends 30va if i remember correctly.
As long as you respect the transformer voltages it is ok. There is a loss though by pumping back to the second transformer. If you use lower voltages on the second is bad, the transformer saturates, gets hot etc. But in this case I use identical transformer.

I'll let you know; tomorrow I try to load the transformers.
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Old 5th February 2010, 11:10 AM   #514
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Quote:
Originally Posted by audiodesign View Post
Apelizzo,
are you sure to have found a cheaper solution using all these separated transformers ?

In any case use a 220:9+9 100w for the filaments and to drive a 9+9:220 50w to get also the 220V ac of anodic voltage is ok

I thought about like you said. I see if I can find another transformer, but $50 more o less... this project is good. All separate shunts why not a few $ more for transformers. I love mono design.
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Old 5th February 2010, 11:14 AM   #515
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Cheap Transformer connections
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Old 5th February 2010, 12:17 PM   #516
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Default Preliminary DAC layout

Something like this
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Old 5th February 2010, 01:04 PM   #517
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Default Make your own transformer

ALTERNATIVE: do your own transformer. It's FUN. Low voltage just few turns!!

You can use two toroids:

Step 1: buy the first one 220-240 primary 24V secondary at least 150VA
Step 2: rip the 24V winding off around 10 turns at the time don't cut the wire.
Step 3: Peel the enamel insulation and measure the voltage with multimeter
Step 4: Repeat Step 2 and 3 until you reach around 10V.
Step 5: Write down the total number of turns you took off the core and divide 14V (24V-10V) voltage drop by the number of turns you ripped off then multiply by 10. That's is close to the number of turns you need to do for the new 4 windings on top of the existing.
Step 6: buy the second toroidal transformer 240Pri 9+9V sec 50VA
Step 7: measure the voltage of the secondary with no load. Should be over 9V (better measure with load as both transformer have different regulation)
Step 8: adjust the secondary of first transformer to match the secondary of the second transformer. Adjust with turns.
Step 9: buy four lengths of insulated copper wire for transformer same thickness and length of the one you ripped off.
Step 10: wind the four lengths of wire to the core together one by one as is more convenient for you. How? put first the wire on a round wood stick that can all go in and out the centre of the core and start sewing, then do the second , third and fourth. Be careful do not damage the enamel protection around the copper wire. Do not use metal tools for winding or do sharp bends to the wire.
Step 11: mark all the wires and test the voltage and adjust till you match the secondary of the second transformer. Cut the wires short as required after you obtained the wanted voltages
Step 12: connect the first 9V secondary to the secondary of the second transformer as per the picture published by Audiodesign so you step up the voltage for the tube anodes.
Step 13: connect the remaining four independently to Heater, Salas +5D, +5A, -5A

Example below of one I made for 280V, over 1400 turns!! For this little ding ding dong dong baby Single Ended 3W ampli, Lovely detailed sound
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File Type: jpg ampli11.jpg (117.9 KB, 404 views)

Last edited by apelizzo; 5th February 2010 at 01:30 PM.
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Old 5th February 2010, 01:11 PM   #518
vzs is offline vzs  Europe
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Default Low voltage tubes?

Can't low voltage tubes like ECC82, ECC86 or 6SL7GT be used in the place of the high voltage ones? Of course with changing the values of some resistors and the PSU of course.

Excuse my question if it's stupid as I don't have any experience with tubes...

Last edited by vzs; 5th February 2010 at 01:32 PM.
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Old 5th February 2010, 01:24 PM   #519
adamus is offline adamus  United Kingdom
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yes it can, but it would need a redesign of the PSU (i would forget using the PS pcb, unless you want to keep the filament supply section) and then as you say, changing values.

if you are worried about the voltage.... read read read, then bite the bullet and do a high voltage project.,
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Old 5th February 2010, 01:36 PM   #520
tassosk is offline tassosk  Greece
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Can I use 180uF/20V Oscons instead 220uf? BOM says 100-220uf
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