The art of Sen

[Bemused]

This thread is in no way endorsed by Patrick and Xen-audio.
I need to point out that we are just a bunch of amateurs lucky enough to be able to have a stab at the Sen in a very DIY and amateur manner.
Readers should in no way associate our amateur efforts with the professional products of Patrick and Xen-audio.

That is not to say there are not some professional members amongst our group, no offence intended.


OK guys, looks like there is some interest in SEN implementation for our buffalos as an upgrade for the Legato 3.1
This is going to be quite a subject on its own so I thought to start a new and bring it out of Suffolk Tony’s huge Buffalo thread.

If you’re in agreement then I will trawl the big Buffalo thread and an start by posting the relevant links to DIYA and Xen etc.

Not sure of my direction yet but I am leaning towards DIY boards either strip or in my case etched.

I think in a group buy on boards is out of the question for obvious reasons but a GB for Jfets seems entirely logical.
Thanks to Needsp and NicMac for generating the interest.

Edit
Below is a kind pm from Patrick of Xen-audio regarding the situation with our playing around with his products.

Tony,

Thank you for your PM.

The SEN Circuit and PCB layout is published, and in doing so I made it available to the public.
There have also been other people who scratch built the SEN circuit, so you are also welcome to do the same.
I also welcome you to publish photos of you build, just like the others.

There is already a working schematics.
Of course you have total freedom to publish an alternative in a public forum like this.
But I think you will also understand that I shall not comment, or wish to be linked in any way, unless I see something fatal.
If I were to make any comments, people will immediately have the wrong impression that I am involved, or at least endorsing that design.
And we make it a rule not to do so, above all since we have no time to check every other layout experimentally to make sure there are no problems.
Sometimes silly things like buzz that Paul has (which we suspect is a Grounding problem of the TPA PCB).

If you just want to test, then I think you are better off with P2P wiring.
If you want proper build, then you should use a decent PCB.
In any case, I advise you to thermally couple the JFETs for minimum DC offset.

So please go ahead and enjoy the circuit.
But please try not to link our name to any work that you might want to undertake.
We shall make encouraging statements when you publish photos, etc.
But we shall not say anything about your PCB design, or build, or else.
We did the same to Paul and the Nic, BTW. So we treat everyone the same.

As I also mentioned in the thread, we shall investigate into a complete XEN Audio 9018 solution.


Best regards,
Patrick

Tony

[orangeart]

Great Tony,

As I said in the other thread, if someone designs a layout we can all etch from (or get some boards made up) I'll happily run the GB for the parts we all need. I really like Florians idea of the board being the same footprint as the legato with the same connection method, makes life a bit easier when swapping stuff around.

How does this thermal compensation work? We could include that in the GB.

Stefan

[orangeart]

As you mentioned in the other thread we should definitely ask permission before proceeding with our own board design. Sounds like a goer though

Stefan

[Bemused]

Stefan, be great if you did a GB for the Jfets, most kind offer.
I have no problem with doing a layout for others to etch subject to Patricks approval and it would of course fit the Buffalo-III
I understand the thermal compensation is just a matter of locking all the Jfets together as one thermal mass, in the Xen case I think they use some hot wire cut EDMP rubber but my thoughts would be to create a small cylindrical mould out of some household item and pour in some slow setting goop once the Jfets are on the board.
No idea of the actual goop yet, maybe polyester resin? (fiberglass) car filler?

Tony

Edit

Xen-audio do not use rubber heatsinks see post 15

[Bemused]

Some links.

The originator and the guy we need to thank for Sen are Patrick
His site is here

The linearaudio bookzine article is here

His DIYA thread is here

The integration and Vref drawings are in DIYA post 606
The charger is in post 612

[Suffolk Tony]

Great stuff! a good idea to split this from the old Buffalo thread, it's getting very unwieldy.

I'm of course very interested, please count me in! Hopefully I'll get my head round it as the thread develops; at the moment I'm wondering about dual-mono. going from single Buffalo was a very significant improvement, so if you could implement SEN with dual-mono won't that sound better than the single Buff too?

I guess what applies to the MkIII Buffalo will also be the same for the Mk II?

[Bemused]

Originally Posted by Suffolk Tony

Great stuff! a good idea to split this from the old Buffalo thread, it's getting very unwieldy.
I'm of course very interested, please count me in! Hopefully I'll get my head round it as the thread develops; at the moment I'm wondering about dual-mono. going from single Buffalo was a very significant improvement, so if you could implement SEN with dual-mono won't that sound better than the single Buff too?

I guess what applies to the MkIII Buffalo will also be the same for the Mk II?

Yes I think we are all having a hard time.
I think for starters we with dual mono will have to loose half our converters, but we still get to keep our dual mono architecture. We can play at adding in more converters once we are up and running with something a little more basic.
I think Buffalo-II and Buffalo-III will work in together, although I don’t have a Buffalo-II.

[Bemused]

Thanks Jo

[Bemused]

I sent a pm to Patrick asking for his approval

You are welcome.

Please note that :

a) There is now an offer for just the SEN V18 only, and not CEN/SEN V18 combined.
b) The CEN/SEN V18 is of course still available.
c) The JFET set is optimised for the SEN V18 circuit and hence may not be perfect quads in that sense.

I would encourage those who have the CEN V18 to try it out.
It is not a single ended but push-pull circuit, so will have less even harmonics, especially if you are not using both balanced outputs of the DAC.


Patrick
__________

[MarkW]

Tony

Be good if this comes off. Whilst my Legato 3.n is delivering very satisfying results, I'd be interested in trying the SEN approach.

Don't have much time to get involved at present, but will keep an eye on developments and try to find some time to skim over the original threads on DIYA.

Mark

[Bemused]

Pleased to have you over seeing Mark

[Bemused]

Could not help myself and had a little sketch.
Its small about 3"x2"
Its just one half of one channel (I think!)
Capacitor is dimensioned for the Xen BOM (Nichicon ES)
Jfets not quite right as I did not have the eagle part for 2SK369V but they are TO92 and I checked the pinout.
Resistors probably over size but I don't know what we are using yet.
All terminals are on terminal headers 5.08mm pitch. Its just a starter idea.

We need
The header dimensions for the Buffalo
Routing optimisation.
Ground plane.
The other half...

[orangeart]

The legato boars layout on the TP site should help with the header positions. Quick work!

Just listening to Bob Marley via legato, hard to imagine it could sound any better really!

Stefan

[cutting42]

OK Tony, I am curious now!

[Bemused]

Unfortunatly I made some cockups already and they could infringe on the good name of Patrick and Xen

I said

in the ZEN case I think they use some hot wire cut EDMP rubber

Actualy they are made out of solid aluminium by CNC wire cut.
They are then matt black anodised for maximum radiiation efficiency.
The JFETs are then glued to the sink using a siver loaded epoxy, like Arctic Silver adhesive.

You can find the origin of those sinks here :

http://www.diyaudio.com/forums/solid...89-2sj109.html
http://www.diyaudio.com/forums/group...-heatsink.html

Tony