• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

March P452 eta

Amplifier dude

Active Member
Joined
Nov 25, 2021
Messages
170
Likes
68
If we have a look at the spikes to the left of the 1khz signal, what do we call them, distortion or noise?

2F0588F7-F038-4D79-91CA-E9E1D0514A5A.jpeg
 
Last edited:

Amplifier dude

Active Member
Joined
Nov 25, 2021
Messages
170
Likes
68
We can continue this discussion here. Off topic for this thread. @boXem | audio , come with your knowledge and analyzer if you wish.

 

tmtomh

Major Contributor
Forum Donor
Joined
Aug 14, 2018
Messages
2,636
Likes
7,493
If we have a look at the spikes to the left of the 1khz signal, what do we call them, distortion or noise?

View attachment 168410

That's a good question. I'm not sure we can answer it definitively, but wouldn't the most likely answer be that it's noise? It can't be harmonic distortion because it's below the fundamental 1kHz frequency of the test signal. And while it could be IM distortion, that too would be unlikely if the signal generator is producing a pure 1kHz tone - there would be no other frequency tone for the 1kHz tone to intermodulate with, yes? I suppose the amp could produce harmonic distortion and then there could be IM distortion from the original 1kHz tone intermodulating with those harmonics. But even then, the lowest difference frequency would be the 2nd harmonic minus the fundamental, aka 2kHz minus 1kHz, which would just equal 1kHz. So I'm having trouble seeing how any spikes below 1kHz could be distortion - seems like it would all have to be noise (which I presume is why @amirm seems to always label it as such).
 

tmtomh

Major Contributor
Forum Donor
Joined
Aug 14, 2018
Messages
2,636
Likes
7,493
I’m not sure. I’m just a dummy who tunes my amps by ear.

No sale. I didn't accuse you of anything or dismiss anything you said. I responded in good faith to a question you raised, which I assumed was a good-faith question. So respond in good faith or else don't pose the question in the first place.
 

Amplifier dude

Active Member
Joined
Nov 25, 2021
Messages
170
Likes
68
No sale. I didn't accuse you of anything or dismiss anything you said. I responded in good faith to a question you raised, which I assumed was a good-faith question. So respond in good faith or else don't pose the question in the first place.
I think you’re misunderstanding me. I in no way was accusing you of anything other than a good faith response. I was just slightly over exaggerating my lack of knowledge in the field. Sometimes sarcasm comes across the wrong way over the internet.
 

tmtomh

Major Contributor
Forum Donor
Joined
Aug 14, 2018
Messages
2,636
Likes
7,493
I think you’re misunderstanding me. I in no way was accusing you of anything other than a good faith response. I was just slightly over exaggerating my lack of knowledge in the field.

Understood, and appreciate your reply. And I get the frustration of feeling like one's experience is being automatically dismissed without any real consideration.

That said, I would be curious to know your thoughts on the question you posed. Thanks!
 

Amplifier dude

Active Member
Joined
Nov 25, 2021
Messages
170
Likes
68
Understood, and appreciate your reply. And I get the frustration of feeling like one's experience is being automatically dismissed without any real consideration.

That said, I would be curious to know your thoughts on the question you posed. Thanks!
No problem, please continue on to the new thread I made. I shared the link a few posts back. Hopefully it will be a great learning thread for all.
 
D

Deleted member 23424

Guest
Hehe. Won't be cheaper than boXem.

I didn't realize that March had gone to the bottom end of the market. Not that long ago, our prices were quite close.

I consider the 4215/E2 to be the best option for your setup. If the pricing is not fitting your budget, I also perfectly understand that you may want to look elsewhere
:)
OK. Let's put my budget issues aside, and, as nice as the superfluous things like audio sense and input level adjustments are, just focus on sound.

Your opamp choice: I may be wrong (usually am) but are you the only brand using OPA1656? Why have you chosen that and what does it offer? I keep reading on here that the Eval version of everything is the way to go, doesn't that use the 1612?

Also, orange is rubbish. Your amps should all be Claret & Blue with images of Declan Rice etched onto the case. You'd sell loads*

*one
 

boXem

Major Contributor
Audio Company
Joined
Jun 19, 2019
Messages
2,014
Likes
4,852
Location
Europe
OK. Let's put my budget issues aside, and, as nice as the superfluous things like audio sense and input level adjustments are, just focus on sound.
<LECTURING MODE ON>Input level adjustment is also related to sound since it allows to adjust system SNR and clipping. <LECTURING MODE OFF>
Your opamp choice: I may be wrong (usually am) but are you the only brand using OPA1656? Why have you chosen that and what does it offer? I keep reading on here that the Eval version of everything is the way to go, doesn't that use the 1612?
OPA1612 has a quite high bias current that creates a DC offset when circulating in the input impedance. If input impedance is too high, it causes pops at startup/shutdown and a bit of distortion in the speaker. Solution is to lower the input impedance, but then the amplifier becomes harder to drive for the upfront electronics, with a risk to add distortion in the system. The Opa1656 trades a bit of noise against a much lower bias current allowing to keep high input impedance. The opamp extra noise is compensated by another design trick and at the end, both boXem buffer and EVAL1 have equivalent noise levels.
Also, orange is rubbish. Your amps should all be Claret & Blue with images of Declan Rice etched onto the case. You'd sell loads*

*one
Sounds interesting. Will have to do the business case...
 
D

Deleted member 23424

Guest
<LECTURING MODE ON>Input level adjustment is also related to sound since it allows to adjust system SNR and clipping. <LECTURING MODE OFF>

OPA1612 has a quite high bias current that creates a DC offset when circulating in the input impedance. If input impedance is too high, it causes pops at startup/shutdown and a bit of distortion in the speaker. Solution is to lower the input impedance, but then the amplifier becomes harder to drive for the upfront electronics, with a risk to add distortion in the system. The Opa1656 trades a bit of noise against a much lower bias current allowing to keep high input impedance. The opamp extra noise is compensated by another design trick and at the end, both boXem buffer and EVAL1 have equivalent noise levels.

Sounds interesting. Will have to do the business case...
Congratulations. You've made the shortlist.
Assuming the refund from Mr March materialises I'll place an order this week. What are your lead times like just now?
<LECTURING MODE ON> BETTER BUY SOME CLARET AND BLUE PAINT <LECTURING MODE OFF>
 
Top Bottom