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Class D Switching Power Amplifiers and Power D/A conversion

Brainstorming Purifi 1et400a amps
Brainstorming Purifi 1et400a amps
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Old 11th November 2020, 09:11 AM   #761
mocenigo is offline mocenigo  Germany
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Quote:
Originally Posted by SKR View Post
I think Neurochrome input buffer is using OPAmp 4562 if I read correctly on the image on their web site.
VTV has asked me to try 4652 also and see how it compares with 1612.
I am seeing most of the Purifi amplifier manufacturers are offering their Amps with options of Sonic Imagery and Sparkos. My experience about Sparkos has been very disappointing and there is no comparison with 1612 which is much cheaper and much better.
I am not sure this is specific to my system or amplifier, but I am wondering have these manufacturers really tested all their offerings and how they perform sonically. No body is offering 1612 except probably Appolon.
Because in my case there is not a subtle but a huge improvement using 1612 over Sparkos which are much more expensive also.
The use of Sparkos and Sonic Imagery is mostly driven by the market. Discrete circuits are preferred by the audiophiles because they are boutique products and therefore they must sound better, right? The fact that they can deliver more current and voltage is secondary - even though that may have ultimately an influence in some cases. The Sonic Imagery ones do actually sound very neutral, details, dynamic, and just great, subjectively, even though they do not measure like a LM4562 (LME49720) or a OPA1612 and similar ones. Mind you, these have been developed to offer better performance and sound than a NE5532, but that one is old stuff now.

RE: the 4562 – I do not think you will hear a difference. Their measured differences are very very small. They behave differently, however and the 4562 is better in the context of a more complex circuit like the Neurochrome, which uses two dual opamp chips (i.e. two opamps per channel) instead of one.

The 1612 is just great in those simple designs, and Apollon offers it in an amp with sweet, sweet, sweet casework and an absolutely killer price for the quality of assembly and care in attention to detail they put in. If I had not decided much earlier to DIY my own amp, I would have probably bought the Apollon - as a former owner of Apollon NC500-based amps (where I had Sparkos, NewClassD ultimate, and Sonic Imagery small socket opamps) I know I could rely on them.

Last edited by mocenigo; 11th November 2020 at 09:15 AM.
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Old 13th November 2020, 10:23 AM   #762
SKR is offline SKR  Thailand
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Thanks for your opinion. At the moment I am going to stick with 1612 as I am getting great results. May be in future I can try Sonic Imagery 990 or May be Weiss which is rather expensive but considered best by some.
Do you think Apollon Purifi integrate with 1612 will sound differently or better than my VTV . The only difference will be the Input buffer which in case of Apollon is a dedicated buffer for 1612 and One SMPS1200 instead of two in mono amplifiers having dedicated power supply.
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Old 15th November 2020, 04:16 PM   #763
Zonneschimmel is offline Zonneschimmel  Belgium
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Noob question here :-).


So I got 3x purifi eval, hypex smps1200 and Ghent audio case. I put everything together hook it up and I have white noise coming from the left channel in 2 of the amps. Source connected or not.

So I open everything up again to see what's up and notice that in the 1 amp that didn't have the noise problem I had forgotten to ground the mains to the chassis. So before closing everything up again I thought I'd ask here if that's to be expected and I shouldn't attach the mains ground to the chassis. I'm not using a balanced source to drive the amps should that matter.
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Old 15th November 2020, 05:37 PM   #764
mocenigo is offline mocenigo  Germany
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Quote:
Originally Posted by Zonneschimmel View Post
Noob question here :-).


So I got 3x purifi eval, hypex smps1200 and Ghent audio case. I put everything together hook it up and I have white noise coming from the left channel in 2 of the amps. Source connected or not.

So I open everything up again to see what's up and notice that in the 1 amp that didn't have the noise problem I had forgotten to ground the mains to the chassis. So before closing everything up again I thought I'd ask here if that's to be expected and I shouldn't attach the mains ground to the chassis. I'm not using a balanced source to drive the amps should that matter.
Please check that the AUX voltage to the FE02 boards is sufficient. If it is too low then the modulators will get a low voltage and the result is white noise. I have been there.
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Old 15th November 2020, 05:45 PM   #765
ionutzxpo is offline ionutzxpo  Romania
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mocenigo is right......aux voltage to low modulator not working in specified parameters=bad oscilation=white noise=sometimes in other class d amps... BUM!
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Old 15th November 2020, 09:26 PM   #766
emailtim is offline emailtim  United States
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Quote:
Originally Posted by mocenigo View Post
Please check that the AUX voltage to the FE02 boards is sufficient. If it is too low then the modulators will get a low voltage and the result is white noise. I have been there.
Could this be the regulated/unregulated jumper setting issue ?

Quote:
Originally Posted by barrows View Post
The SMPS 1200 offers unregulated ~ -/+ 18 VDC rails (or regulated at -/+ 12 VDC). Most of the optional input buffer board designs feature onboard regulators, meant to be used with the unregulated supply from the SMPS 1200.
In my Purifi build, I use a separate, linear, regulated, power supply at -/+ 18 VDC to feed the input board(s).
There are a lot of options and different ways to power the input board(s) if one is crafty about it.
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Old 15th November 2020, 11:00 PM   #767
mocenigo is offline mocenigo  Germany
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Originally Posted by emailtim View Post
Could this be the regulated/unregulated jumper setting issue ?
Could be. Double check that.
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Old 16th November 2020, 08:46 PM   #768
emailtim is offline emailtim  United States
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Quote:
Originally Posted by Zonneschimmel View Post
Noob question here :-).

So I got 3x purifi eval, hypex smps1200 and Ghent audio case. I put everything together hook it up and I have white noise coming from the left channel in 2 of the amps. Source connected or not.

So I open everything up again to see what's up and notice that in the 1 amp that didn't have the noise problem I had forgotten to ground the mains to the chassis. So before closing everything up again I thought I'd ask here if that's to be expected and I shouldn't attach the mains ground to the chassis. I'm not using a balanced source to drive the amps should that matter.
@Zonneschimmel,

Do you have any updates ?

Did you check the Regulated/Unregulated settings on the Hypex SMPS1200 (see previous posts about proper unregulated settings) ???

TIA
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Old 16th November 2020, 08:52 PM   #769
Zonneschimmel is offline Zonneschimmel  Belgium
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Yup, changing jumper J6 and J7 fixed the issue. Thanks guys :-)
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Old 17th November 2020, 12:21 AM   #770
emailtim is offline emailtim  United States
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Originally Posted by Zonneschimmel View Post
Yup, changing jumper J6 and J7 fixed the issue. Thanks guys :-)
Excellent !!! Let us know what you think once you have some run time on them.
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