Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

[NicMac]

Originally Posted by John Luckins

Well it is a significant step up from my Legato I/V stage which I had been very happy with. I can't identify any downsides. Bass lines are both more even and easy to follow, vocals are a great deal clearer and complex passages remain open and clear. More real instruments and a less synthetic delivery all round. After a day with it I can't identify any shortcomings compared to the Legato.

John

I think this is as close as it can be to what I found. I don't know why it is better, but my assumption is simply simplicity.

With the SEN connected to the F5X I only have three FETs and no caps between DAC and speakers. Can't be (much) more simple than this and the difference is audible - again

[orelli]

Thanks John for the useful informations.

Patrick, have you compared batteries vs mains ps? Can you tell us your impressions?

[RollE2k]

Thanks for your input John.
As said, i wonder if you would have any noise without the choke. And also, have are you using Schottky rectifier diodes, since they should be the ones with minimum switching noise?

[John Luckins]

Originally Posted by RollE2k

Thanks for your input John.
As said, i wonder if you would have any noise without the choke. And also, have are you using Schottky rectifier diodes, since they should be the ones with minimum switching noise?

I'm using Qspeed LQA03TC600 silicon diodes (which are very low storage and quiet switchers) and two 220nf caps across the chokes with the centre connection of these going straight to earth. This dissipates the switching spikes from the diodes across the internal impedance of the choke and controls their frequency as well (keeps it low).

I'm wondering, are you suggesting that the choke increases the noise or do you want to know if the result is noise free without it? I suspect the latter.I could remove the four of them and see although it is a lot of trouble as the rectified voltage will exceed the voltage rating of the first set of caps and changing the caps will damage the boards. BTW they are 72-0-72 volt transformers! They were what I had handy.

John

[RollE2k]

Originally Posted by John Luckins

I'm using Qspeed LQA03TC600 silicon diodes (which are very low storage and quiet switchers)

I'll probably try Schottkys, since they should give minimum noise.

Originally Posted by John Luckins

I'm wondering, are you suggesting that the choke increases the noise or do you want to know if the result is noise free without it? I suspect the latter.

As you guess, it was because i wanted to see if it was noise-free without the chokes. Still, i was thinking about either use one 2x100mH CM-choke before each regulator, or maybe even two. With a small cap in between them.
Anyway, now i at least have something to go after. So thanks alot!

[EUVL]

Nic has already reported in detail his experiences with mains supply and batteries.
I don't have much to add.

If you use a tranformer with regulator, or simply an L-C, you should use the same on the battery.
Then the difference is significant, especially in such floating supply circuits.

4x R-Core is probably as close as you can get to the complete isolation of the 4 IV circuits as you can to batteries.
The difference is in imaging.


Patrick

[Bemused]

Hello Patrick, just catching up on the latest gossip and got to thinking my batteries are in two touching stacks per channel. Would you recommend physical distance between the stacks on the same channel.

I am using SEN V18

Regards
Tony

[EUVL]

I assuming you are using balanced.
In that case the two packs are out of phase by 180°.
If you also shield them, the distance is not important.
I have them about 1cm apart, but easy enough to experiment for yourself.


Patrick

[samoloko]

Originally Posted by John Luckins

I've just got my SEN up and running with Buffalo II and have a virtually hum free background without recourse to batteries/chargers. I didn't have to resort to common mode chokes either. I used 4 separate R cores for each 18 volt rail. These centre tapped transformers were full wave rectified using just the two diodes and choke regulated using 1.5H 200mA Hammond chokes. This was followed by two 100ohm/6800uF R-C filters and then a Salas regulator for each rail. I had used this same supply setup very successfuly with the I/V stage of my Legato so it was just a matter of disconnecting the earths from the supplies and upping the voltage to 18 volts. Here are some picies:



The Salas regs for the SEN are the four to the bottom right of the picture. The transformers, chokes, rectifiers and filtering are off board at the moment but will be housed in a separate case:



I see no good reason to regress to battery supplies which will be noisier, off higher impedance and of varying voltage and therefore create varyiations in output voltage offset and ultimately more expensive in the long term. The little very low level hum I am getting is because of the choke regulated supply for the digital stages of th Buffalo which is just over an inch below the SEN boards. Increasing this distance removes this minor hum altogether.

John

would you please tell us what are red caps you are using with Salas BIB
why you are using only two from four wires from BIB

[John Luckins]

Originally Posted by samoloko

would you please tell us what are red caps you are using with Salas BIB
why you are using only two from four wires from BIB

Hi,

The Red caps are Shizuki 4.7uf 100v polpropelene film. They were NOS from Cricklewood electronics in the UK but I'm afraid I got their last remaining stock. The closest equivalent to these that can be made to fit and is available are the Wima MKP range, but the Shizukis sound a little better when driving analogue circuits.

I plan to use the four wires eventually but bear in mind that the SEN is a constant current draw (set by the Idss conbination) and so low impedance is of no great advantage. There is less to go wrong with a two wire circuit. It is also worth bearing in mind that the SEN presents a load of two series 220uF Electrolytic capacitors. Some series resistance needs to be introduced between the Salas reg and this effective 110uF approx 0.3 ohm ESR load in order to at least critically damp the resulting resonant circuit. I've since added a series 1 ohm resistor and could hear the improvement it made. It took a slight glassy sheen off the sound and improved the bass definition.

john