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Old 5th November 2012, 03:40 AM   #1261
EUVL is offline EUVL  Europe
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Try to use separate heat sinks for each channel.
Or connect the heat sink with a thick wire to your DAC Gnd.

(I am sure you know none of your wires should touch the sink).


Patrick
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Old 5th November 2012, 08:56 AM   #1262
heb1001 is offline heb1001  China
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Quote:
Originally Posted by optimationman View Post
If one channel is connected, it operates fine(the other channel with a 1K on it). When I connect both, the working channel get's "jittery" and the new channel has high speed modulated signal wave and half the amplitude of the working one.
I have also done some P2P Sens.

I had similar symptoms with one channel working when the other was not connected and both not working when both were connected when I made a mess of epoxying the jfets to the heatsink getting unset hardener bridging the jfet legs and heatsink.

I've also seen oscillation when I connected the L+R Sen grounds together with a common lead to the DAC ground.

I have the Sen instances (with bias servos for the pcm1794) and DAC chip in different enclosures and getting the grounding right for my set-up was a nightmare.

This is probably not appropriate for your set-up which is hopefully easier but for the record...

With balanced inputs, my servos need to connect back to the DAC ground for the DC bias.

I got the best results from connecting the L Sen ground to the L shield of the balanced output to the L amp monoblock and similarly for the R Sen instance. These shields are connected to chassis ground where the signals enter the chassis. This follows the rule for balanced circuits of one connection from circuit ground to chassis ground. L+R Sen grounds are not connected together except through the chassis.

The L+R servo grounds which are separate in the Sen enclosure go back to the DAC enclosure (which is a PC with a noisy SMPS) in a third wire in each of the L+R shielded cables from the DAC chip and connect to the sound card ground. The ground of the bias servo power supply in the Sen enclosure is connected to one of these grounds in the Sen enclosure and therefore to the other one via the sound card. The shields on these cables are telescoped from the PC chassis and not connected to the DAC enclosure.

I have tried a lot of other combinations including leaving the Sen instances floating and this way is one of a few good solutions.

So, 3 lessons learned: it's a mistake to put the bias circuit in a different enclosure from the DAC chip (having the Sen circuit in a different enclosure may be a mistake but can be made to work well enough though); it's important to keep the L+R circuits separate to avoid oscillation; for smooth sound it's important to avoid ground loops.
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Old 5th November 2012, 02:27 PM   #1263
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Default Thanks for the suggestions

I am single ended, and have keep the channels completely separate, sans the heat sink. There is no path between the heat sink and the lead of the Jfets. I was hoping to just connect the sen to the DAC chip analog out/grd directly without installing it inside the player to evaluate the sound before removing the class A opamp system in use. I did remove the feed to it however(obvious). I was mostly happy with it, but you know how we modding audio types are, something better???? The signal connection and battery leads are twisted for outside rejection and about 8 inches long. No cables within 12 inches of these. Will try the grounding strap to the sink today.
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Old 19th November 2012, 11:42 PM   #1264
heb1001 is offline heb1001  China
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I went back to try out #998 again with the grounds connected as described in #1262 and this time it sounds good. #998 shows 2+1 pairs of JFETs but I used 3+1 and RM1=0R in this test. Worth a try, IMO. Measures well too.
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Old 23rd November 2012, 09:52 AM   #1265
EUVL is offline EUVL  Europe
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We have been asked about how to connect the SEN IV for AKD12P for 2 channel single ended (ES9012 DAC).
I cannot find any manual of the AKD12P in the public domain, and I do not want to guess.
So I think the best thing to do is to post the question here and let those who has the same gives the answer.

My speculation is that it has 2 channel differential out and DC offset as in the ES9018 in stereo mode.
So you would need to use SEN-V18 with 16 2SK369Vs in total.

You will then have 2 channel balanced output.
These you can convert to single ended using a number of solutions, such as ICs, transformers, or the XCEN converter.

There are people who suggested using only one phase of the output.
I cannot find any information in the ES9012 datasheet regarding unconnected current outputs, or single phase performance figures.
All specs are quoted in differential mode, which are of course better than single ended due to common mode rejection and even harmonics cancellation.
So if I were to do it myself I would use a converter.
But you can also read Paul's experience with his SE solutions in this thread.

Do feel free to experiment and post your results for all to share.


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Old 23rd November 2012, 11:16 AM   #1266
qusp is offline qusp  Australia
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connecting just one phase is bound for fail... the entire internal routing and analogue performance is based on using a very symmetrical signal outputs, you will lose more than 3dB thats for sure. a bal-se conversion stage is a much better solution. i'm interested in your XEN actually for a friend, are you nearing enough interest for production? nvm i'll ask in the thread.

yes you are basically correct, just treat the AKD12 analogue output specifications as es9018 in stereo balanced mode but with all the dacs paralleled internally instead of externally.

the AVCC/2 voltage is taken from the AVCC flea type regs and divided, for best performance they should be increased to 3.6v with an increased input voltage for the regs of >+/-10vdc (I use 12). it doesnt make for a very neat connection with SEN, because the outputs are in the center very close to the dac, rather than the edges and the pinout +/- and G are all very tightly coupled together for best performance.

I think for best connection to Ackodac a DIY PCB or perfboard construction arranged to allow stacking more directly is best. otherwise I fear the performance of both devices will suffer more than needed.

the current PCB can be made to fit, but would require some custom made rigging to allow close enough current connections and avoid having to keep the power supply (batteries) so far away

Last edited by qusp; 23rd November 2012 at 11:24 AM.
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Old 23rd November 2012, 12:45 PM   #1267
EUVL is offline EUVL  Europe
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We have enough discussion about stacking. You can refer to those a while back.

I remain totally convinced that the current PCB close to a shield and away from the DAC is my preferred solution,
especially that the connection between DAC and IV is in current mode.
So I see no need to change anything.

But do what pleases you, which is what DIY is all about.


Best regards,
Patrick
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Old 25th November 2012, 02:30 PM   #1268
orelli is offline orelli  Italy
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Hi all, what's the Vout RMS of the SEN V 18 + Buffalo II?
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Old 25th November 2012, 05:38 PM   #1269
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Whatever you want, within reason, by choosing the correct value of R_iv.


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Old 25th November 2012, 07:27 PM   #1270
orelli is offline orelli  Italy
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R_iv is 680R
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