Review and Measurements of Purifi 1ET400A Amplifier

[SIY]

Edit: his response is that pin 1 is not tied to the chassis.

Boom.

 

[March Audio]

Mission accomplished.

I contacted the owner of VTV and his response is this:

“Yes there is no pin one problem. The chassis is ground led to earth and the modules audio signal is not. That is what Hypex directs.”

(I mistakenly did not specify Purifi in my email contact, but he ensured me in a follow up that it works the same)

I also purchased a Purifi amplifier from him with stock Hypex board, I haven’t received it yet.

Then that confirms he doesnt have adequate electronics understanding. This is a very well known issue.

The chassis doesnt appear to be connected to mains safety earth as there is no wire on the connector dedicated for that purpose. I dont see bolts holding the IEC receptical to the chassis, so I dont see a connection there, but this could be the case. Looks like a push in job.

 

[JustJones]

I went to hypex and read their paper on pin 1 and they said it should ground to chassis.

https://www.hypex.nl/p/application-notes-white-papers/

 

[March Audio]

I sent another email his way. He responds very quickly, I’ll give him that. It’s fairly late so I may not get a response tonight.

After seeing the internals, I’m a little bummed. If it is ground correctly, is the lack of twisted wiring and proximity of the boards to PSU enough to worry the amplifier will not function as intended?

Edit: his response is that pin 1 is not tied to the chassis.

It will function but may be susceptible to noise pick up. This is particularly the case with the design using the Hypex eval board.

Bit in bold =

 

[Labjr]

Pin #1 has no function in the audio signal. So don't connect it to the audio circuitry.

 

[March Audio]

I went to hypex and read their paper on pin 1 and they said it should ground to chassis.

https://www.hypex.nl/p/application-notes-white-papers/

Yep

https://www.hypex.nl/img/upload/doc/an_wp/AN_Legacy_pin_1_problems.pdf

 

[March Audio]

Here is a picture of the VTV. With stock buffer it cost $900. Anyone care to comment on the build? It looks like scant attention has been given to cable dressing, but does that matter much in this case? Looks a little rough to me, but the price is compelling.

View attachment 59624

Just curious, how is power turned on/off?

 

[JustJones]

There is an on/off switch on the back. I emailed for a RMA I'm sending it back, no reason I should fix this stuff. If I could do that I would build my own.

 

[Cujobob]

There is an on/off switch on the back. I emailed for a RMA I'm sending it back, no reason I should fix this stuff. If I could do that I would build my own.

I’m curious what he will say. His response times are amazing, I have to give him that.

I hope it’s not in bad taste to post his responses, I don’t feel like they necessarily need to be private. I also linked to him our discussion in case he wanted to chime in himself.

Here’s what I was last told:

“
Yes the pin one problem is way bigger than that forum. I found this to be the lowest noise and risk of ground loop taking cable shield ground from the source.

By the way, earth ground to chassis is established through the IEC filter inlet’s outside case being in contact with the filed surface (anodize removed) of the chassis itself.”

I’m not claiming to be an expert in amplifier construction or electronics, so I’m trying not to jump to any conclusions either way. From what I’ve read, the proximity of the modules and PSU shouldn’t pose an issue (it’s not atypical, though that means little). If it’s correctly grounded, the only issue (potentially) appears to be what happened with pin 1?

 

[JustJones]

I’m curious what he will say. His response times are amazing, I have to give him that.

I hope it’s not in bad taste to post his responses, I don’t feel like they necessarily need to be private. I also linked to him our discussion in case he wanted to chime in himself.

Here’s what I was last told:

“
Yes the pin one problem is way bigger than that forum. I found this to be the lowest noise and risk of ground loop taking cable shield ground from the source.

By the way, earth ground to chassis is established through the IEC filter inlet’s outside case being in contact with the filed surface (anodize removed) of the chassis itself.”

I’m not claiming to be an expert in amplifier construction or electronics, so I’m trying not to jump to any conclusions either way. From what I’ve read, the proximity of the modules and PSU shouldn’t pose an issue (it’s not atypical, though that means little). If it’s correctly grounded, the only issue (potentially) appears to be what happened with pin 1?

I see no need to post emails they were short and to the point. He said that's fine if I returned the amp and asked what other components I used for reference. I didn't get into build quality as I didn't see a need to get confrontational.

 

[TimoJ]

By the way, earth ground to chassis is established through the IEC filter inlet’s outside case being in contact with the filed surface (anodize removed) of the chassis itself.”

Should these amps use an IEC filter? I recall reading something about it.

 

[Julf]

Should these amps use an IEC filter? I recall reading something about it.

Bruno had a strong (negative) opinion (based on a pretty good factual rationale) abut IEC filters that had a capacitor bypass to ground/earth.

 

[Labjr]

I don't know who VTV is but I wouldn't buy that. I'd rather assemble it myself.

 

[March Audio]

There is an on/off switch on the back. I emailed for a RMA I'm sending it back, no reason I should fix this stuff. If I could do that I would build my own.

Thought so from looking at the picture. So you need easy access to the back to turn it on and off...... Mmmmm......

I would ask for all shipping costs too as the unit is unsafe.

 

[March Audio]

I’m curious what he will say. His response times are amazing, I have to give him that.

I hope it’s not in bad taste to post his responses, I don’t feel like they necessarily need to be private. I also linked to him our discussion in case he wanted to chime in himself.

Here’s what I was last told:

“
Yes the pin one problem is way bigger than that forum. I found this to be the lowest noise and risk of ground loop taking cable shield ground from the source.

By the way, earth ground to chassis is established through the IEC filter inlet’s outside case being in contact with the filed surface (anodize removed) of the chassis itself.”

I’m not claiming to be an expert in amplifier construction or electronics, so I’m trying not to jump to any conclusions either way. From what I’ve read, the proximity of the modules and PSU shouldn’t pose an issue (it’s not atypical, though that means little). If it’s correctly grounded, the only issue (potentially) appears to be what happened with pin 1?

He is completely wrong about pin1.

If the IEC filter case is not bolted to the chassis then just "touching it" is not adequate.

Grounding doesn't help regarding the PSU proximity. It's about the EM radiation switching from the circuit, the inductors etc. It's something you would have to measure on the amp output to see what's really going on.

 

[March Audio]

Should these amps use an IEC filter? I recall reading something about it.

No, Julf covered it.

 

[spacebar]

Since audiophonics have a different design, the pin 1 problem is not a an issue?

 

[March Audio]

Sorry to return to the subject of the Pin 1 Problem, but I could use a bit more clarification. I noticed that, in Archimago's infamous post, he doesn't seem to account for the Pin 1 Problem. If I read the above correctly, Pin 1 should be wired to the chassis and the cable shield can be soldered to "Pin 4," which is the silver prod on the top left corner. Is this correct? If so, would a short wire from Pin 1 to one of the nuts by it work?


View attachment 59946

http://archimago.blogspot.com/2020/01/an-inexpensive-hi-fi-class-d-stereo-amp.html

March Audio: every day I see that your amps are worth the price!!

Yep that is most definitely wired wrong . Pin 1 should go to chassis.

I'm not sure about those specific connectors but if pin 4 is connected to pin 1 then that's not right either. If it connects just to chassis then that's what I would use to connect pin1 to.

The xlr connectors on my amps have sharp pins that impale into the chassis when you bolt it down connecting pin1 to the chassis.

 

[Ludodo57]

bonjour, j'ai klipsch rf7 mk3, pensez-vous que cet ampli purifié audiophonique 1et400a serait un bon duo avec un dac topping d90?

 

[Ludodo57]

hello, i have klipsch rf7 mk3, do you think this purified amp 1et400a audiophonics would be a good duo with a dac topping d90?