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The art of Sen

df_genius said:
The only thing that puts me off with the Cen/Sen was the floating power supply (i.e. batteries). You then either have to fit a charging circuit in the case, fit an exernal battery pack or take the lid off and change the batteries every so-many hours. I bought four 9V PP3 rechargeables to use, and am planning to fit a switch to the rear panel to switch the supplies on and off.
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I have a fundamental question about floating supplies.
Isn´t every power supply without any reference to a common ground a "floating supply"? Meaning, if you had, for example, 4 separate windings on your transformer and use 4 regulators of your choice for each SEN-circuit - without connecting the supplies to each other - isn´t this a floating supply, too?

Apparently people had best experiences with battery-supplies at the SEN, but technically, conventional regulators can be made floating as well. Or do I understand something wrong here?
 
cubeasic said:
I have a fundamental question about floating supplies.
Isn´t every power supply without any reference to a common ground a "floating supply"? Meaning, if you had, for example, 4 separate windings on your transformer and use 4 regulators of your choice for each SEN-circuit - without connecting the supplies to each other - isn´t this a floating supply, too?

Apparently people had best experiences with battery-supplies at the SEN, but technically, conventional regulators can be made floating as well. Or do I understand something wrong here?
Click to expand...

I believe you are right, but can't be sure. A dedicated transformer with rectification and 18v regs seem to make sense to me for this circuit, but over in DIYA batteries seem to be the way people use them.
 
Hi Cubebasic

Isn´t every power supply without any reference to a common ground a "floating supply"? Meaning, if you had, for example, 4 separate windings on your transformer and use 4 regulators of your choice for each SEN-circuit - without connecting the supplies to each other - isn´t this a floating supply, too?
Click to expand...

Yes

Apparently people had best experiences with battery-supplies at the SEN
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no- rather people have had terrible results with mains powered supplies! See the DIYAudio thread for reasons. Basically, it seems impossible to remove enough common mode interfence from mains powered supplies to get good results.

Just use batteries! :) Patrick has given all necessary info to include charging arrangements on board cheaply, simply and effectively. Once installed they're no trouble at all. Every night I unplug the power to the (mains powered) Buffalo board, and every second night or so I plug in the charger supply overnight. The multiple AAA batteries I used are good for over 20h continuous use, and, fitted in the sealed battey holders (4 x 4 high stacks, 16 cells per supply) they're neat and self-contained

Paul
 
Yes the floating supply can be any supply so long as there is no connection to the supply other than the load. No earth, no other load. It just finds its own symmetry, I thought it was neat. All neat tricks seems to have a downside, downside here is we need four supplies.
So yes
4 x separate transformer secondary winding
4 x regulators of your choice

Suddenly batteries seem a cheap simple attraction :)

I would certainly look to using some 9 volt batteries for my starter rig and once all the wrinkles are sorted ... who knows.



Regarding the matching, I understand ideally we would match / select also for highest IDSS, certainly with our high current Buffalos.

Stefan, why the sudden change of heart?
I thought in the initial stage to just bodge the Legato and use its BAL/SE stage, TPA also sell BAL/SE stages on there own, there ore others on the market I would think.
Ultimately I would like to have my own BAL/SE converter on the same board.
A BAL/SE can be one op-amp and a few resistors and capacitors.
 
High Paul, do you have links to the battery kit you use, its all new to me.

My last post was occupied with a cup of tea, took a while and hence overlapped somewhat.
 
Thanks for the information, Paul.
Mentally, I am in the process of making friends with a battery supply.
But maybe I will try some teddyregs, too - just because I have them :)

Price might be an issue here, yes. but you can get a custom 100 VA transformer quite cheaply for about 35 euros with 4 secondarys. Of course the regulators are another story...

For Bal/SE conversion, I am sure there are also transformers, which can be mounted inside the DAC to give a SE output. For active SE conversion you would need another PS and regulator, etc.
 
Dear all,
I have a last spare set of SEN V18 PCBs, heat-sinks and FETs and I would like to share this with you if the (very lucky!) recipient has the time and will to post the process of implementing it with the Buffalo.

I see that you chaps are having all the same doubts, questions and interest that I had when I started. My goal is therefore really only two-fold: 1) to disseminate the sonic experience that I am having with this circuit and 2) to take all the voodoo out of how to implement it.

Anybody want to take the offer up?

I will of course stick around with practical help if needed.

The only issue that I cannot solve for you is how to use the circuit with single ended pre/power amps. Paul has reported that a good signals transformer works just great, but I have no personal experience with this.

Cheers,

Nic
 
Mighty fine offer Nic and I would be pleased to accept.
Pretty cose to pushing the button on a set anyway.
What do you want for them?

I need SE myself and would as a starter probably look to hacking into the BAL/SE that exists within the Legato.
Also think Sulfolk Tony may have some stand alone TPA Balse that he may want to off load :)

Tony

Edit
Should a more proficient member wish to take the boards I would step down of course.
 
I've got two Redundant TP Ballsie Lites hanging about. Better hang on to one but the other's going spare.

Like Tony I'm only interested in SE & the conversion will need to be done in the DAC - no way will I mess with my preamp! Still, looks like this project's moving along at a cracking pace & I'm optimistic someone'll work out a good SE solution. I wish I could contribute more to the thread rather than just watch with great interest.
 
Hi Guys

Good news for you SE users!

In the past I've tried the ESS9018/Buffalo II board with three other IV stages than SEN and, in all cases, found that taking just one phase of the balanced ouput for SE use resulted in a very noisy and distorted output signal.

I assumed SEN would be the same. But I just tried taking a SE output from SEN, one channel only. It seems absolutely fine- certainly the gross distortion I found with the other IV stages is gone! I checked both channels, and both + and - phases. Final confirmation will have to wait until I can listen critically in stereo, but I think the "problem" is solved!

Now some balanced circuitry zealots have a fit of the vapours over doing this (obviously not Patrick, as he suggested it!), and it's true some benefits of balanced operation are lost. But I suspect it will sound very fine- and I'm in a position to check!

More later

Paul
 
I think were all after SE here but its no big deal.
All of us with Legato have the BAL/SE on the board.
Here is the BAL/SE segment of the Legato.
Untitled-2.jpg


Looks like we need to just cut two tracks and feed the Sen in.

The TP Ballsie Lites are perhaps also good starter options, I understand they are very small and probably the same circuit as the Legato BAL/SE.

This circuit is an easy DIY etch or even strip board, the are many others on the internet.

Thanks for the TP Ballsie Lite offer Tony I may buy that of you when the time Approaches.

A neat BAL/SE just appeared on TPA post 1021, looks like Patrick is geting involved in a BAL/SE also
 
Paul, I also would like to keep the balanced converter output from the Sabre, using just one end (SE) does not make sence to me. This would be the Cen option?
The Buffalo balanced output is floating at 1/2 AVCC, maybe this is why it does not implement well and why this particular part needs to stay balanced.

I like your dirty fiddle to the Sen output though. :)
 
Hi Tony

No, I think you're still confusing "push pull" with "balanced"- completely different things! Probably because SEN uses single ended circuity, but stillforms part of a circuit giving a balanced output. CEN does exactly the same, except it uses a push pull topology.

The revised SEN- and CEN- circuits for the ESS9018 DAC provide the DAC with the 1/2 AVCC reference voltage it needs (on the IV stage's inputs) for the arrangement to work with low distortion

Consider one channel. The revised SEN uses two "blocks" (your description) of four fets, one block for each phase. So the circuit block is single ended, but the overall circuit still has a two phase output, referenced to ground- it's balanced. In CEN, the blocks are push pull in operation, but the whole is still balanced

BAL to SE conversion can be done in many ways- you've listed some of the obvious ones I considered. Details of the actual implementation apart, it's best practice to preserve the balanced signal for as long as possible, so I decided to put the converter in preamp. And the best way of doing this, IMO, for a line level signal is a well designed transformer. Certainly better than an op amp- IMO. Though a discrete JFET circuit as Patrick is considering might well do the trick

I've no idea if taking one phase and ground from SEN as a SE output requires the unused phase to be identically loaded- i.e. by a powered unused SEN "half"! Or whether the - phase can be unloaded, or dummy loaded. TBH I don't want to try this- I don't know why it might damage the DAC, but don't want to find out !

Paul
 
Started to sketch in the other balanced side of the I/V stage.
Please its rough and I am a novice but it will get a little tidyier

And realised there are a few things I need to think about / check on.

In blue is the Vref of the two sides of channel one, not sure if we use just one Vref from the AVCC regulator.
Upper blue line is showing the wrong place but I a sure it’s a photobucket cache problem and will sort itself out.

In red I think the -tve Vout should be the same terminal.

Any gross cockup spotted?

Untitled-3.jpg


Edit
There is only one Vref, getting confused as I have a whole Buffalo with two Vref supplies for one channel, the stereo guys are not the quite the same with only half a Buffalo.

Also started to think how this might fit to the Buffalo, at first thought a pair of mirror boards for left and right channel would do the job for stereo, TPA phase mono and in-phase mono. I don't think there are any more configurations.
 
needsp said:
Consider one channel. The revised SEN uses two "blocks" (your description) of four fets, one block for each phase. So the circuit block is single ended, but the overall circuit still has a two phase output, referenced to ground- it's balanced. In CEN, the blocks are push pull in operation, but the whole is still balanced
Paul
Click to expand...

Good description.
Yes, I had not considered the Sen uses the Sabres Balanced output in a SE manor, quite obvious now.

Too much talk of BAL / SE / CEN / SEN.

I am now only considering connecting the Buffalo to the Sen and getting single ended output from after the Sen by some means yet to be decided. :)
 
I just got a quote for 500 pieces of 2SK369V from "Space Coast IC. Inc" for about 525 USD, so about 1 USD per piece.

I guess, that also at other distributers, especially for lower quantities, the price would not fall much below 1 USD per piece.

Does anybody know of other sources for the 2SK369V?
 
Would we get stung on import duty / VAT, still makes them a nice price.
If the GB was opened outside this thread it may attract a few more punters but I think we could handle 500 ourselves.
 
I just progressed in the diyaudio thread, where Patrick explains the matching odds. Apparently they match Idss to 0,2mA, which gave them a rate of 50% non fitting FETs.

Taking this approximation as a basis, on matched set would require about 32 Fets, so about 32 USD + shipping and import fees. And we would get 15 sets out of 500, maybe a little bit more...
 
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