Review and Measurements of Purifi 1ET400A Amplifier

[Erikgunnar]

Interesting, thanks! So does this setup make their pin 1 grounding not a problem?

I am not qualified the answer that but many on this forum are for sure. I like to know myself.

 

[Sieniek]

Guys, are there any benefits if I would buy audiophonics Purifi mono blocks instead of €150 cheaper audiophonics Purifi stereo ?

Please let me know what do you think as I am very close to buy the amp, just deciding which one to buy. Thanks

 

[Matias]

Guys, are there any benefits if I would buy audiophonics Purifi mono blocks instead of €150 cheaper audiophonics Purifi stereo ?

Please let me know what do you think as I am very close to buy the amp, just deciding which one to buy. Thanks

Pros:
- Absolute channel separation, although crosstalk between channels is usually very low anyway (like -100dB as per the NC252MP measurements on Buckeye amp).
- Moving each mono amp closer to the speaker allows shorter speaker cables, a little better damping factor.

Cons:
- More expensive.
- Takes up more space.
- Needs a 2nd power cable and outlet.

 

[tmtomh]

Guys, are there any benefits if I would buy audiophonics Purifi mono blocks instead of €150 cheaper audiophonics Purifi stereo ?

Please let me know what do you think as I am very close to buy the amp, just deciding which one to buy. Thanks

Matius lays out the pros and cons well. My view is that the bottom line is that the stereo amp is the way to go and the dual mono blocks are not necessary.

 

[somebodyelse]

To be clear. There is chassis gound on pin 1 but the chassis ground does not come from grounding at the connector but from chassis grounding through the buffer board.

To be more clear, you're aware of the the various XLR models that have an internal connection between pin 1 and the chassis, and you know this isn't using one of them?
EDIT: for those that aren't aware, some connectors have something like a metal spike next to the mounting screw that's intended to pierce the paint or anodizing to make a good connection to the chassis during normal assembly, but this is invisible when installed. The connection between pin 1 and this spike may be difficult or impossible to see too, depending on connector model.

 

[Erikgunnar]

To be more clear, you're aware of the the various XLR models that have an internal connection between pin 1 and the chassis, and you know this isn't using one of them?
EDIT: for those that aren't aware, some connectors have something like a metal spike next to the mounting screw that's intended to pierce the paint or anodizing to make a good connection to the chassis during normal assembly, but this is invisible when installed. The connection between pin 1 and this spike may be difficult or impossible to see too, depending on connector model.

Well noted. For the Audiophonic amp if I dissconect the input cable to the buffer board that comes from the XLR/RCA input board the pin 1 chassis ground dissapear. If I messure on the ground pin on the buffer board it connects to chassis. So no ground chassis connection of the XLR/RCA input board.

 

[Erikgunnar]

Matius lays out the pros and cons well. My view is that the bottom line is that the stereo amp is the way to go and the dual mono blocks are not necessary.

The only thing that MIGHT make any difference Stereo vs Mono is that Mono uses a power supply per channel (Hypex 600) while the stereo amp share one larger power supply for both left and right channel (Hypex 1200). If that will matter I do not dare to tell with my experience

 

[Julf]

Well noted. For the Audiophonic amp if I dissconect the input cable to the buffer board that comes from the XLR/RCA input board the pin 1 chassis ground dissapear. If I messure on the ground pin on the buffer board it connects to chassis. So no ground chassis connection of the XLR/RCA input board.

Just as a reminder, this is the configuration Bruno recommends:

 

[tmtomh]

Just as a reminder, this is the configuration Bruno recommends:

View attachment 105423

Right. So - and I apologize for being dense here - the Audiophonics appears not to use that configuration, but based on the connectivity tests/measurements @Erikgunnar has reported above, does it seem like Audiophonics has avoided the Pin 1 issue by other means, or do their units have the Pin 1 problem?

 

[q3cpma]

Pros:
- Absolute channel separation, although crosstalk between channels is usually very low anyway (like -100dB as per the NC252MP measurements on Buckeye amp).
- Moving each mono amp closer to the speaker allows shorter speaker cables, a little better damping factor.

Cons:
- More expensive.
- Takes up more space.
- Needs a 2nd power cable and outlet.

Also: if only one channel breaks, no need to buy the whole stereo amp anew.

 

[Erikgunnar]

Right. So - and I apologize for being dense here - the Audiophonics appears not to use that configuration, but based on the connectivity tests/measurements @Erikgunnar has reported above, does it seem like Audiophonics has avoided the Pin 1 issue by other means, or do their units have the Pin 1 problem?

Yes does it really matter? If pin 1 has chassis ground does it matter of the interconection is at the jack or at the board.

 

[Julf]

Right. So - and I apologize for being dense here - the Audiophonics appears not to use that configuration, but based on the connectivity tests/measurements @Erikgunnar has reported above, does it seem like Audiophonics has avoided the Pin 1 issue by other means, or do their units have the Pin 1 problem?

The "pin 1 problem" is caused by connecting pin 1 to signal ground instead of the chassis. As long as pin 1 is not connected to signal ground, you are OK.

 

[tmtomh]

The "pin 1 problem" is caused by connecting pin 1 to signal ground instead of the chassis. As long as pin 1 is not connected to signal ground, you are OK.

That’s what I thought. Thank you for the confirmation!

 

[somebodyelse]

Yes does it really matter? If pin 1 has chassis ground does it matter of the interconection is at the jack or at the board.

If you want a practical test to see if it's a problem see AN007 from Jensen Transformers. The whole thing is worth reading, but section 3.3 introduces 'The Hummer' to check whether your device has a pin 1 problem.

 

[Sieniek]

Hello Guys,

I am happy to say that with your help I am a happy owner of two Purifi Audiophonics mono blocks. Just received them yesterday and they are excellent. They are doing their job perfectly.

I have some questions, do you know how I can bypass the gain stage and if it is worth it ? Do I need to screw out some screws and change it inside the case ?

I have minidsp shd and this is from where I play my music using rca connections between this and amps. Will it be enough Voltage to drive these amps ? Is there any difference if I would buy XLR cables and connect them instead of RCA cables ? Higher output Voltage ?

I have full range speakers which are very easy to drive.

And one more question as I cannot understand one thing. Before the Purifi amps I’ve had a Devialet 220 expert pro and the full range speakers has been connected to Devialet but my subwoofers has been connected exactly in the same way all the time to minidsp shd 3 and 4 analog outputs. When I have changed the Devialet amp for Purifi amps my subwoofers are playing quieter so I needed to volume up them by quite a lot...

How is that possible and why that has happened if the only component I have changed were the amps which are driving the full range speakers only anyway ?

Is that because the Purifi have more power so there is a bigger difference in the loudness between the Purifi amps and the subwoofer active amps ? This is what I have thought at first.

I hope you understand my questions and can help with the answers.

If anyone would like to ask me about anything regarding the Purifi mono blocks please let me know I will try to get back as soon as I can.

 

[VintageFlanker]

I have some questions, do you know how I can bypass the gain stage and if it is worth it ? Do I need to screw out some screws and change it inside the case ?

Yes, it is explained there.

Is it worth it? Not really: add very few dB (inaudible) THD+N but you will have to deal with much lower sensitivity (12.8dB gain) and some preamp able to output up to 10Vrms or so.

Stock jumper position (20dB) is OK if you use XLR (4V) out of your MiniDSP. For 2V RCA, I would try instead the 25.3dB gain (max power at 2.25Vrms)

 

[Armand]

Bypassing the buffer can lead to increased distortion because the preamplifer must drive a heavy load through the signal cables. Just reducing it to +7.2 is a safer option, byt you can try.

Yes, the problem with the subwoofer is because the different gain from Devaliet.

Our Vera P150 amplifier (Purifi) have gain setting in 3dB steps adjustable on the back. Our buffer is can go all the way down to zero gain in the buffer (for a total gain of just 12dB in the purifi modules) Much easier

 

[Erikgunnar]

I also have the Purifi Audiophonics mono blocks. I have high Vrms from my DAC so I have set up the mono blocks to bypass of the Audiophonics gain stage.

My thinking was since I have high Vrms to the amp why would i then add an additional gain stage = pre-amplification of not needed?

Can distortion increase running high Vrms though XLR cables and bypass extra the additional gain stage?

My gut feel just makes me feel that it is strange but I am no guru.

 

[Julf]

Can distortion increase running high Vrms though XLR cables and bypass extra the additional gain stage?

The cables of course don't make a difference, but the absence of the buffer stage might, depending on how load-sensitive your DAC is. The role of the buffer is not just gain/amplification, but also impedance matching.

 

[Erikgunnar]

The cables of course don't make a difference, but the absence of the buffer stage might, depending on how load-sensitive your DAC is. The role of the buffer is not just gain/amplification, but also impedance matching.

Well noted. Thanks!

My DAC has 300Ω XLR output. The Purifi Audiophonics mono blocks have 4.4kΩ input buffer bypassed (94kΩ with buffer).

300ohm out and 4.4kΩ in sounds ok?