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-   -   2A3 PSE 'Arcadia' by SJS, or sorta (http://www.diyaudio.com/forums/tubes-valves/37510-2a3-pse-arcadia-sjs-sorta.html)

Kris0603 9th July 2004 07:34 PM

2A3 PSE 'Arcadia' by SJS, or sorta
 
Hello DIYers

First off, i am a beginner to tube diy, but not to electronics or HV power supplies. I have done some research on what project to build, and the choice fell on the above stated amp. For a link to the schematic, please see:
http://www.users.globalnet.co.uk/~va...es/ARCADIA.GIF

My incarnation will be a highly integrated amp, with input selection and possibly tone/RIAA.
However, as i have a limited budget, i will redesign the power supply. I have a copy of Duncan's PSU Designer, in which i have played around a little. I have sourced most of the tubes already, they are:

2x 6072A GE JAN from angela
2x 5687 Phliips ECG from angela
2x 5U4GB GE from angela
2x 5Y3 nos from tubeman.com
4x 2A3 Valve Art from tubeman.com

So, nothing fancy tube-wise. The 5U4's i intend to supply the 2A3's, one per channel. Choke input, two 159P (10H 125mA 155R) and a Rifa 470uF/400V cap.

Signal coupling caps i have bought a pair of 0.33uF Al, Paper in oil types from angela. I also bought two SCR tinfoil types from angela, to experiment/de-coupling.

My idea on the power supply is to slightly raise the voltage, from 260 to about 265-275, or maybe lowering plate dissipation slightly (such as 10-12W ea.), this to give the chokes a little easier time, and maybe improve regulation, i dont know.

I will use shared(L-R) supplies for the input stage/driver and the bias, using the 5Y3's. I have not simulated this, nor gotten any of the other filter chokes.

For power transformer i feel like a custom toroid from askJan will do nicely, and theyre not all that expensive, at least not for the VA.

OPT's. Basically i am pondering two choices here, either buy 1627SE Lundahls direct from Per, at about 130 euro a piece. Or buy imported iron from dhtsound.com in korea, two incl. shipping for 130 euro. The Lundahls would be nice, but would mean i would have to wait an extra month before i could complete the amp. I might buy the korean OPTs now, and upgrade later to Lundahls, and using the dhtsound iron in another project.

I have thought about the pre-amp stage a lot, i feel Simon's design is very versatile. These are my ideas:

I have the main components for a DIY DAC board, using AD1865. My wish is to incorporate this directly into the amp. Also tone controls and/or RIAA would be nice. My idea now is this:

I think Simon uses the triodes of each 5687's in parallel, but i also think he only uses one half on the 6072A per channel. Why not create another gain stage using this other half of the 6072A and use it to amplify the output from the DAC? Could we then also insert passive RIAA eq bypassable between the two stages, and possibly also a bypassable tone-control network?

The idea is to have everything configurable by the user, so he or she can choose what stages should be active at what time.

I would greatly appreciate comments and input on my thoughts presented here, and also input on Simon's design, the PSU considerations, anything you feel like sharing.

Warm Regards
Kristian Kjeldsen

Bas Horneman 10th July 2004 12:29 AM

Quote:

I would greatly appreciate comments and input on my thoughts presented here, and also input on Simon's design
First of all...I think you should stick to his design...You will get so many suggestions...! And you obviously have looked at many a schematic...and this is the one you liked.

I reckon the dac won't need an additioanal gain stage... and I would suggest that you rather build a seperate RIAA amp in an seperate enclosure...

What Lundahl did you want? The 1627SE is Hammond I think...You would need something with a lower primary impedance...something like the 1,8k indicated in the schematic.

My 2pf worth.

Cheers,
Bas

fdegrove 10th July 2004 01:16 AM

Hi,

What escapes me is the reason to go for PSE....

If you need more power why not pick a higher power tube or simply go for PP?

Quote:

The idea is to have everything configurable by the user, so he or she can choose what stages should be active at what time.
Hmmm....all too often you end up with so many compromises on sound quality that IMHO it's not worth the bother.

Cheers,;)


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