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DIY Purifi Amp builds

maxxevv

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In this forum and many other threads.

.
Citations needed.

Nobody recommends IC Opamps because "they opamp roll off".

The common consensus here for IC opamps is because they generally work better in their correctly applied circuits than boutique discrete circuit ones. And the competent circuit designers typically implement the IC opamps already optimized for the application. Changing for aftermarket ones seldom if not almost never improve things when it comes to performance measurements.
 

sloth_kwj

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Citations needed.

Nobody recommends IC Opamps because "they opamp roll off".

The common consensus here for IC opamps is because they generally work better in their correctly applied circuits than boutique discrete circuit ones. And the competent circuit designers typically implement the IC opamps already optimized for the application. Changing for aftermarket ones seldom if not almost never improve things when it comes to performance measurements.
Exactly what I’m talking about. Sorry for my bad English...
 

ZestClub

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So between Sonic Imagery 990 Pro OP Amp and Weiss OP2-BA Op amp does anyone have a preference?
 

Count Arthur

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So between Sonic Imagery 990 Pro OP Amp and Weiss OP2-BA Op amp does anyone have a preference?

I think the general consensus is that these "boutique", descrete component op-amps offer no measurable, or sonic benefits, or may even be inferior to off-the-shelf, integrated circuit op-amps that cost a fraction of the price.

IC op-amps like the LME 47910/47920 and the OPA1612, and others, have excellent measurements and are probably hard to beat. Even if you did beat them technically or measureably, it's debatable whether it would make an audible difference to the end product.

Between the three descrete op-amps you listed, the chances are that the sonic differences between them are vanishingly small once part of the whole amplifier and as such, you may as well opt for the cheapest.
 

Feanor

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Which of the input Buffers/ Voltage Regulator combinations do you guys recommend as being the best sounding most analytical?

Sparkos Labs SS2590
Sonic Imagery 990 Pro OP Amp.
Weiss OP2-BA Opamp
At this juncture I'm not recommending. However today I will receive VTV buffers to replace the "standard", i.e. evaluation Hypex buffers.

FWIW, I find with the Hypex that during louder passages I get a lot of "glare" from brass and string instruments in particular, (though transparency and dynamics are amazing).

I ordered Sparkos SS3602, (DIP8), op amps. The VTV buffers use the "Sparkos SS78xx and SS79XX discrete voltage regulators" according to VTV. See ... https://vtvamplifier.com/product/vtv-amplifier-custom-input-buffer-hypex-nc500-nc1200-nc2k-purifi/

Personally I have found that op amps, even high spec ones, don't all sound exactly the same though differences are generally slight -- of course these are subjective judgements. :oops:

The VTV buffers are flexible in that they permit the use of DIP8 and also API op amps, (such as the Sparkos SS2590). I am prepared to do a little op amp rolling. I have ordered dualed OPA1612's and I have several other op amps lying around such as the LME49720 and good old OPA627.
 

sloth_kwj

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At this juncture I'm not recommending. However today I will receive VTV buffers to replace the "standard", i.e. evaluation Hypex buffers.

FWIW, I find with the Hypex that during louder passages I get a lot of "glare" from brass and string instruments in particular, (though transparency and dynamics are amazing).

I ordered Sparkos SS3602, (DIP8), op amps. The VTV buffers use the "Sparkos SS78xx and SS79XX discrete voltage regulators" according to VTV. See ... https://vtvamplifier.com/product/vtv-amplifier-custom-input-buffer-hypex-nc500-nc1200-nc2k-purifi/

Personally I have found that op amps, even high spec ones, don't all sound exactly the same though differences are generally slight -- of course these are subjective judgements. :oops:

The VTV buffers are flexible in that they permit the use of DIP8 and also API op amps, (such as the Sparkos SS2590). I am prepared to do a little op amp rolling. I have ordered dualed OPA1612's and I have several other op amps lying around such as the LME49720 and good old OPA627.
Is it able to apply IC opamp on VTV input buffer?
 
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JimB

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At this juncture I'm not recommending. However today I will receive VTV buffers to replace the "standard", i.e. evaluation Hypex buffers.

FWIW, I find with the Hypex that during louder passages I get a lot of "glare" from brass and string instruments in particular, (though transparency and dynamics are amazing).

I ordered Sparkos SS3602, (DIP8), op amps. The VTV buffers use the "Sparkos SS78xx and SS79XX discrete voltage regulators" according to VTV. See ... https://vtvamplifier.com/product/vtv-amplifier-custom-input-buffer-hypex-nc500-nc1200-nc2k-purifi/

Personally I have found that op amps, even high spec ones, don't all sound exactly the same though differences are generally slight -- of course these are subjective judgements. :oops:

The VTV buffers are flexible in that they permit the use of DIP8 and also API op amps, (such as the Sparkos SS2590). I am prepared to do a little op amp rolling. I have ordered dualed OPA1612's and I have several other op amps lying around such as the LME49720 and good old OPA627.
The standard Hypex evaluation buffer has been criticized for end user application as incomplete. The details of this criticism do not apply to the Purifi evaluation buffer. There have been some nice studies of performance of op-amps. Unsurprisingly, they vary considerably depending what you expect from them (what aspects of performance were optimized) and how they are implemented in use. It is not appropriate to just drop-in different op-amps (integrated or discrete) to a specific board and expect them to all perform at their best. Some otherwise good ones can perform horribly when not optimized. Even trace layout matters with high bandwidth devices. All this said, it turns out some boutique discrete op-amps really perform quite badly, regardless of implementation - easily the equivalent of headless panthers. Despite this, some might genuinely prefer whatever noise and distortions they produce. Personally, I can't go there. If it measures badly, I have no interest. But, among those that are not 'bad', there could be various reasons for preferences. I'll not attempt to define the limits of 'bad', other than that, for me, if it is 'transparent' as used in ASR, it is significantly better than 'bad'.
 
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phoenixdogfan

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The standard Hypex evaluation buffer has been criticized for end user application as incomplete. The details of this criticism do not apply to the Purifi evaluation buffer. There have been some nice studies of performance of op-amps. Unsurprisingly, they vary considerably depending what you expect from them (what aspects of performance were optimized) and how they are implemented in use. It is not appropriate to just drop-in different op-amps (integrated or discrete) to a specific board and expect them to all perform at their best. Some otherwise good ones can perform horribly when not optimized. Even trace layout matters with high bandwidth devices. All this said, it turns out many boutique discrete op-amps really perform quite badly, regardless of implementation - easily the equivalent of headless panthers. Despite this, some might genuinely prefer whatever noise and distortions they produce. Personally, I can't go there. If it measures badly, I have no interest. But, among those that are not 'bad', there could be various reasons for preferences.
It continues to mystify me why people want to roll op amps especially when the Eval 1 is so good right out of the box. Just get the SMPS, get the Eval, get a good case, wire it up properly, add a 12 v trigger and a front panel on/off if you want, and just enjoy.
 
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JimB

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I've heard some are disappointed that the S1 Standby switch does not work with the Ghent case kit cables. That is because the /AMPON line is being controlled by the SMPS (which I prefer). IF YOU HAVE THE S1 SWITCH FULLY INTACT, AND you really want to reach around the back to put the amp in Standby, rather than fully off, then you can simply cut the /AMPON wire between EVAL1 J3p1 and SMPS J4p6.
https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-14#post-304137

I'll suggest cutting at least a couple inches from one end. That way, if you change your mind later, you can readily splice the cut ends back together. Protect the cut ends to ensure they cannot come in contact with anything, electrically. I don't have Ghent cables, and they might not have fully standardized wire colors, but, in their website photo, /AMPON is the 'dark green' wire - the one at the end by itself. CHECK THE POSITIONS! DON'T CUT THE WRONG WIRE!
Screenshot 2020-11-14 120234.jpg
Screenshot 2020-11-14 120258.jpg


EDIT: Or this: https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-88#post-569604
 
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wineds

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I've heard some are disappointed that the S1 Standby switch does not work with the Ghent case kit cables. That is because the /AMPON line is being controlled by the SMPS (which I prefer). IF YOU HAVE THE S1 SWITCH FULLY INTACT, AND you really want to reach around the back to put the amp in Standby, rather than fully off, then you can simply cut the /AMPON wire between EVAL1 J3p1 and SMPS J4p6.
https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-14#post-304137

I'll suggest cutting at least a couple inches from one end. That way, if you change your mind later, you can readily splice the cut ends back together. Protect the cut ends to ensure they cannot come in contact with anything, electrically. I don't have Ghent cables, and they might not have fully standardized wire colors, but, in their website photo, /AMPON is the 'dark green' wire - the one at the end by itself. CHECK THE POSITIONS! DON'T CUT THE WRONG WIRE!
View attachment 93559 View attachment 93560

Would it also be possible with a small jewellers screwdriver to remove the dark green wire and socket pin from the black J4 header housing?
 

FBU

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Hello,

I am following this helpful thread with much interest, as I have just ordered Eval1 and Ghent case and harness.

Could I also just wire an additional standby switch on the front of the case and connect it in parallel between J3p1 and J3p6?

There is one other thing that I noticed from the pictures of the Purifi Eval1 samples sent to reviewers: Purifi is not connecting the AUX connectors between the powersupply and the Eval1 (instead using the I2C connector to implement the front standby button). Why would Purifi implement it in this way and are there any obvious benefits related to this?

Thanks.
 
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JimB

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Would it also be possible with a small jewellers screwdriver to remove the dark green wire and socket pin from the black J4 header housing?
I don't have one so I can't say. There should be some means of pin extraction possible. On the EVAL1 J3 end, you should be able to pry up the little locking tab and slide the crimp out.
 
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JimB

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Hello,

I am following this helpful thread with much interest, as I have just ordered Eval1 and Ghent case and harness.

Could I also just wire an additional standby switch on the front of the case and connect it in parallel between J3p1 and J3p6?

There is one other thing that I noticed from the pictures of the Purifi Eval1 samples sent to reviewers: Purifi is not connecting the AUX connectors between the powersupply and the Eval1 (instead using the I2C connector to implement the front standby button). Why would Purifi implement it in this way and are there any obvious benefits related to this?

Thanks.
Yes, you could certainly wire a standby switch to short J3p1&p6 to enable the amp, provided you remove that p1 wire connection from the Ghent cable, and leave your S1 switch in the "off" position. That is the equivalent of moving S1 from the rear panel to the front. Note that the power supply will not be in standby, only the amp modules. I'm unclear on the real value of this, other than to mute the amp.

Regarding them not using the AUX connectors, if you inspect, closely, they do use J3 for VUNREG (+, -, and GND) from the SMPS J4. They also use J2 to power a front panel LED and to switch /AMPON, but those signals are not on that connector!
1605477624876.png

They cabled from ground and UNUSED pins, which must mean they hand wired the signals they wanted to that connector, under the board, for their convenience. Purifi did what they wanted for their demo units. And, as noted, they do not populate that header on the boards they sell in their on-line store for the likes of you and me. You could solder in your own pins.
 
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sloth_kwj

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Yes, you could certainly wire a standby switch to short J3p1&p6 to enable the amp, provided you remove that p1 wire connection from the Ghent cable, and leave your S1 switch in the "off" position. That is the equivalent of moving S1 from the rear panel to the front. Note that the power supply will not be in standby, only the amp modules. I'm unclear on the real value of this, other than to mute the amp.

Regarding them not using the AUX connectors, if you inspect, closely, they do use J3 for VUNREG (+, -, and GND) from the SMPS J4. They also use J2 to power a front panel LED and to switch /AMPON, but those signals are not on that connector!
View attachment 93768
They cabled from ground and UNUSED pins, which must mean they hand wired the signals they wanted to that connector, under the board, for their convenience. Purifi did what they wanted for their demo units. And, as noted, they do not populate that header on the boards they sell in their on-line store for the likes of you and me. You could solder in your own pins.
Is it able to make push-button on front with Ghent case? I could CNC for making holes.
 
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JimB

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You could read some of the earlier posts from others who have done more of their own methods for that.
 
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zappa

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That is because the /AMPON line is being controlled by the SMPS (which I prefer).
...

Hi,
How the SMPS control the /AMPON (I mean what exactly it is doing) ?
Thanks in advance ?
 
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JimB

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Hi,
How the SMPS control the /AMPON (I mean what exactly it is doing) ?
Thanks in advance ?
/AMPON means NOT amp on. Leaving that input open means the amp is not active - it is in standby. When the SMPS1200 is on and it's outputs are good, it pulls that line low (near ground) which tells the amp it should be active (not in standby). When you turn the SMPS off, it immediately releases that line, telling the amp to go to standby while power drops. This should manage the amp safely, telling it when to be active or not, as power comes on and goes off.
 
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