Valve Itch phono

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#101
Hi again Tani

Just another thought.

Don't like multi output LV transformers myself.

Personaly I always go for dual winding toroids or R-cores if you can get them.
R-cores would be 'super cool' IMO for the 'Itch'.
ie. 120-0 + 120-0v / 9-0 + 9-0v

You then have the option of seperate heater windings. Series or parallel connection.

I now habitualy wire stuff for dual UK/USA voltage as well, As I might emigrate to NYC one day !

Cheers

Simon
 
#102
Hi Simon and Tani,

the ratio of 1.41 (sine to rectified) is true for unloaded outputs. Using a 100VA transformer for a 40mA load shouldnt cause a lot of loss, though. If you were to use a 10VA transformer you would see that voltage drop considerably.

Small trick, when connecting transformers back to back you may want to put a foil cap of some microfarads in parallel with the middle connection, this will be quite effective in removing noise coming in from the grid.... less work for the regulator...
 
#103
Excellent lessons everyone, many thanks.

I am not shooting for optimal components right now as I have my fingers in many DIY pies. I'm aiming to get something that works well without too much sacrifice on quality, so that I may assess the virtues of each bit of kit and figure out which I like best and focus on those. I think I'll try back-to-back Tx's to get it up and running, then go from there.

I looked at R-cores and found some that were suitable, as were other torroids, though with the cost of postage to Australia, this would be the type of thing I'd install on a final build. I've saved spending on oil caps and the like for the same reason... I feel like I can put faith in a circuit that sounds good with decent yet modest components... then add to it later for the icing on the cake.

With all of your input I feel like I have enough knowledge to proceed... thanks again.
Tani.
 
#106
Yes, I have a few - but not phono. Few EL84 amps, and refurbished a KT66. Made a few aikido preamps as well.

I have a pearl with lundahl step-ups and I just think that a valve phono with some step ups could be a very nice compliment to the system. I'm using a benz L2 and a zyx R50.....

Plan on doing the SSHV supply (need 2 actually, one for this and one for a 6SN7 aikido). Have the parts for that, just need some time at the bench!

Fran
 
#109
Theoretically no. If stringing the heaters of the same elevation valves won't introduce any noise to the sensitive input signal ones will show in practice. Those Russian input tubes have proved very well constructed and quiet non the less.
 

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#110
Thanks,

I've seen some say that 6SN7s are not suited to wiring in series (although my aikido has them in series and its quiet). Just thought I'd check had you come across this - may be important in as sensitive a case as this.

I'm working through the list of parts, hope to have an xls file over the next few days with mouser numbers.

Fran
 
#111
Since I haven't seen it working with stringed heaters, I can't speak from experience. Gibson had used them in parallel for one. I would prefer you don't mix stages heaters if possible for this kind of gain app.
 

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#119
For Riaa such caps lack in tolerance. For output I prefer 2u2 and to pre-shape the LF roll off with the interstage so it can mate many line inputs, still holding a determined rate fall. 47n to 100n interstage OK. 2u2 difficult in CCCP caps. Maybe K75-10 500B 1u//1u // FT3 0.1u. Green monstrosity with a silver accent.😀
 
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