Clipping noise of Topping PRE90 connected with EHA5

[elhendu]

Hello,
I'm using TOPPING’s dac E70, preamplifier PRE90 and electrostatic headphone amplifier EHA5 with my active speakers(Genelec 8030c). I'm having a problem of clipping in a certain situation while using these devices.
I am not good at English, but I will explain the situation where I suffer from clipping noise and the situations that I tested to foind out the cause.

Situation A)
When I connect the XLR output of E70 to EHA5 at the DAC's maximum volume, connect the XLR PASS-THROUGH output of EHA5 to PRE90, and connect the XLR output of PRE90 to my active speakers, clipping noise occurs.

Situation B)
When I connect the XLR output of E70 directly PRE90 at the DAC's maximum volume without going through the PASS-THROUGH of EHA5, the above clipping noise does NOT occur.

Situation C)
When I connect the RCA output of E70 directly to PRE90 at the DAC’s maximum volume and connect the XLR output of the PRE90 to my active speakers, clipping noise does NOT occur. However, when I connect E70's XLR output to EHA5 in this setting, active speakers generate clipping noise even though the PASS-THROUGH output of EHA5 is not connected to PRE90.

The headphone output of the EHA5 does not produce clipping noise in any of the above cases.

As far as I know, the analog output of DAC should be maximum volume to get the best sound quality, and the XLR output is better than the RCA output. So I want to use the XLR output of E70 at the maximum volume, and I want to use the XLR PASS-THROUGH feature of EHA5 to connect the XLR output of E70 to PRE90 and EHA5 simultaneously. However, in this situation, clipping noise occurs, so now I have no choice but to connect the XLR output of E70 directly to the PRE90, and EHA5 is being used in connection with the RCA output of E70.

Why do I get clipping noise when I use EHA5's PASS-THROUGH function or the XLR input of EHA5? Is there any way to prevent clipping noise while using EHA5's XLR input and PASS-THROUGH function with PRE90?

I have mailed to Topping Service on this problem, but I am wating for the reply.

Thank you very much for reading this post.

 

[staticV3]

Hi @elhendu! Welcome to ASR.

In Situation A, when you hear clipping noises, could you please try these things:
1) Use the E70's volume control to reduce volume by 10dB or so -> is the noise still there?
2) Reset the E70 to max and switch the EHA5's gain (leave the EHA5 off) -> does it clip in both Low and High gain?

 

[elhendu]

Hi @elhendu! Welcome to ASR.

In Situation A, when you hear clipping noises, could you please try these things:
1) Use the E70's volume control to reduce volume by 10dB or so -> is the noise still there?
2) Reset the E70 to max and switch the EHA5's gain (leave the EHA5 off) -> does it clip in both Low and High gain?

1) Yes, reducing the volume of the DAC definitely helps reduce clipping noise. By reducing volume by -15dB, I cannot notice the clipping noise. But by -10 dB, I can still notice the clipping. And I think it would be better to connect EHA5 to RCA out of E70 rather than lower the volume of DAC by -15dB.

2) My speakers connected to the PRE90 always produce clipping noise regardless of the gain setting of the powered-off EHA5, as long as the EHA5 is connected to the XLR OUT of the E70.

Thank you for your kind advice.

 

[elhendu]

Interest in this topic is expected to be extremely small. However, for those who may experience similar symptoms in the future, I'd like to explain about some additional tests I did.

With regard to situation C above, when I connect the E70's RCA out directly to PRE90 and connect E70's XLR out to EHA5, the speakers connected with PRE90 generate clipping noise. But when I switch output setting of E70 from "RCA+XLR" to "RCA only", the speakers do not generate clipping anymore.

Also, when I switch PRE90 with another headhpone amp, the headphone connected with the headphone amp produce clipping noise. Additionally, I have tried another DAC, but the result was not changed.

Based on the above tests, I concluded that there is a problem with the XLR input part of my EHA5. But I don't know if this is a design problem or just my unit's problem. I have inquired about this problem to the Topping service, so I think Topping will find out the the cause soon. I will update this post as soon as I receive a reply.

 

[elhendu]

Topping replied to my inquiry that they also found this problem through a test, and after a while, they provided me with a new version of firmware to solve this problem. The previously installed firmware version was 1.20, but the firmware provided this time was 1.40.

After reflashing the firmware, there is no more clipping noise in Situation A and C. Yeah, this means that even if the EHA5 is powered off, clipping will no longer occur through the amp directly or indirectly connected to the EHA5.

However, even after updating the firmware, I found that when the power cord is unplugged from the EHA5, the clipping noise is still generated in Situation A and C. This shouldn't be a particular problem, of course, because I'm going to plug in the EHA5 even if it's powered off. But I asked Topping again about why this is happening several days ago, but I haven't heard back yet.

Anyway, the problem I was having with EHA5 seems to have been solved. And I am quite happy with it so far.

 

[simmconn]

In the EHA5, the pass-thru output is connected through a relay to the amp's input circuit, which is protected from over voltage. It's a simple protection by clipping the input to the power rails. When you power off or yank the power cord, the internal power rails collapses, leaving very little headroom for the signal that is passed through. That's why you hear clipping. The "firmware fix" isolates the pass-thru output from the input circuit by operating the relay when you put the unit into standby. However the relay needs power to operate. When you yank the power cord, you are back to square one.