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Old 7th April 2012, 05:55 AM   #731
regal is offline regal  United States
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Patrick I am finally going to have time to put the SEN 4x 2sk369 kit together with
my AD1862 DAC. For this version is 2x9V batteries a still a good starting point ( I don't have a model of the 2sk369) ?
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Old 7th April 2012, 06:00 AM   #732
heb1001 is offline heb1001  China
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Quote:
Originally Posted by EUVL View Post
AP1 was at its time industrial reference. It is still one of the best you can get with reasonable money.

The red curve (SEN IV 18V) in your measurement above indicates 2nd & 3rd harmonics in the order of -95~-100dB.
This is about the same order as what we published.

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

I am fully aware that you can find opamp circuits that can give better figures.
Just as you can find opamp based amplifier circuits with exceeding low THD figures.
If that is the most important criterion for you then maybe you should stay with your original IV design.
I am sure there are also many nice sounding opamp designs if done right.


Best regards,
Patrick
Music sounds great with SEN - see #696

My power amp is a pair of KT88 mono-blocks with no global feedback - somehow I don't think I'll be kicking everything off with a pair of op-amps for much longer.

Let's see where I get to with tuning your lovely SEN circuit. The results above are just baseline numbers. I haven't even started yet.
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Old 7th April 2012, 06:04 AM   #733
EUVL is offline EUVL  Europe
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> Music sounds great with SEN - see #696

I am glad we agree this is more important than chasing THD numbers.

Why don't you spend a few dollars and just try it with 2x9V batteries and a simple LC, just for comparison ?
Maybe like Nic, you will not want anything else afterwards.


Patrick
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Old 7th April 2012, 06:06 AM   #734
EUVL is offline EUVL  Europe
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> For this version is 2x9V batteries a still a good starting point ?

Yes.

> I don't have a model of the 2sk369 ?

MODEL 2SK369_V NJF (VTO=-574.395M BETA=95.173M LAMBDA=1M IS=10F RS=3.11187
+ CGD=36.6561P CGS=60.0451P PB=1.99682 KF=0.001F AF=500M )

.MODEL 2SK369BL NJF (VTO=-398.254M BETA=85.9633M LAMBDA=1M IS=10F CGD=36.6561P
+ CGS=60.0451P PB=1.99682 KF=0.001F AF=500M )

.MODEL 2SK369GR NJF (VTO=-337.112M BETA=80.3593M LAMBDA=1M IS=10F CGD=36.6561P
+ CGS=60.0451P PB=1.99682 KF=0.001F AF=500M )

Just build it. It is quicker than any sim, and you have real results.


Patrick
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Old 7th April 2012, 06:09 AM   #735
heb1001 is offline heb1001  China
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Quote:
Originally Posted by EUVL View Post
Why don't you spend a few dollars and just try it with 2x9V batteries and a simple LC, just for comparison ?
Maybe like Nic, you will not want anything else afterwards.


Patrick
I was thinking the same thing. That would be another interesting baseline but I really don't want an unattended battery charging circuit. Particularly not with li-pos and absolutely not one designed by any amateur (myself included).
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Old 7th April 2012, 06:50 AM   #736
EUVL is offline EUVL  Europe
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No need to use LiPo's. NiMH is just fine.
I have been leaving my charger on for my preamp since 2007, non-stop.

You can use the one I published here. It is simple, and quite safe.

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


Patrick
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Last edited by EUVL; 7th April 2012 at 06:52 AM.
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Old 7th April 2012, 06:51 AM   #737
regal is offline regal  United States
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Quote:
Originally Posted by heb1001 View Post
I was thinking the same thing. That would be another interesting baseline but I really don't want an unattended battery charging circuit. Particularly not with li-pos and absolutely not one designed by any amateur (myself included).
I am the same way. My theory was use 18650 battery holders in the circuit and just pop them out and put on a proper charger.

However with one project I inserted one of the batteries the wrong way when I put it back in the holder after charging, big stupid mistake

I like the idea of 9V rechargeables 'casue you can't put them in wrong

I think there are lithium rechargeable 9V's now.

Last edited by regal; 7th April 2012 at 07:16 AM. Reason: need a new keyboard
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Old 9th April 2012, 12:48 PM   #738
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Patrick

switching off / on your charger Is done manually ? when ?
BTW what are you using to power relays and what voltage relays are you using
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Old 9th April 2012, 01:13 PM   #739
EUVL is offline EUVL  Europe
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You switch the ZEN IV on and the charger off at the same time.
So when you are not playing, the charger is always on (at my home 24 hrs for days on).

Relays is low current. I use Omron G6S. 12V or 24V depending on your control circuit.


Patrick
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Old 9th April 2012, 02:48 PM   #740
heb1001 is offline heb1001  China
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Default PCM1794/SEN on batteries with servo op-amps removed

I was a bit suspicious of all the high order distortion in my previous measurements - normally it's the result of lots of negative feedback somewhere - so I pulled out the servo op-amps during the measurements and took the spectrum from just afterwards before the circuit had drifted.

The difference is particularly clear in this second set of measurements which I have taken whilst running the floating supply on batteries (one channel is batteries, the current drain and other channel are still regulated 12V supplies).

I don't believe the 2nd harmonic distortion result in these measurements - the only way they can all be the same is if it's from the ADC. A lot of the other even harmonics are also less than the odd ones. The rest of the harmonics are more interesting.

So my hacked together servo is introducing some high order distortion - not that surprising given that it is amplifying the signal way past the point of clipping and then applying that to the input (even if through a low-pass filter).

I need to design a better servo.

I also measured the balance of the floating supplies at rest and they are out of balance by about 5% because I didn't match my jfets well enough (I should probably have waited for them to warm up; there were 100 though). Spice indicates this is enough to cause some distortion as well.

I have a design for a second servo to fix the mismatch which works in spice (3rd harmonic down to -140dB with mismatched jfets and Riv reduced to 250R) but I also need to work on that one to make sure it doesn't introduce high order distortion.

So it looks like there is plenty of scope for SEN to beat my OP-AMP IV on measurements as well as the listening test
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