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I think it actually feasible if you want to mod the A07 by replacing the 20K feedback resistor on the A07 input op-amp to 10K. See my explanation above.

The gain of these amplifiers are defined by combing the gain from the input op-amp gain and the TPA3255 chip gain. In both amplifiers the TPA3255 gain will be the same. The difference in the gain between them will be the resistors ratio on the input op-amp. for the A07 the ratio is 20K/10K that...

I meant ratio not in dB. So in dB it will be 26dB for the Fosi V3 and 32dB for the A07. Amir measured around 26dB for the Fosi V3 and 29dB for the A07.I have few A07, and they all measured gain are 32dB. Still there are few dB gain difference between them that can explain the few dB THD+N...

To all comparing the Fosi V3 to the Aiyima A07 , please pay attention to the max gain difference between them. The Fosi V3 max gain is 20 and the A07 max gain is 40. This fact can explain the few dB advantage that the Fosi V3 has on the A07 with the THD+N results. No other magic.

You can use this free software: http://www.tolvan.com/index.php?page=/tone/tone.php

The way I am doing it is finding the T2P resonance frequency by fitting the IEM in my ears the way I will use them to listen to music, and then using frequency sweep generator to find it. After that I am inserting the IEM into the IEC711 coupler with depth that will generate the same resonance...

Why are you not trying to equalize T2P peak? this peak is only existed when using IEM.

As I suggested I have IEC711 coupler that I am using for my IEMs eq. Also I will mention that there are few IEMs with very small variations between them like the Etymotic ER4XR That can be a good platform to eq to Harman target with information you find online.

Who suggested exactly the same? I said that they don’t have similar tone in the regions I mentioned.Good for you that you find them similar as for me they are not , and it will be interesting to get more feedback from other that tried it.

Did you actually listened to IEM eq to Harman IE target? did you actually listened to over the ear headphones eq to Harman OE target? if yes did they sound similar ? For my ears they don’t sound similar.For me both targets results are different. i will be happy to get feedback from people that...

I have IEC711 coupler and eq a lot of IEMs to the Harman IE target. Again you can also see the in Harman papers as I mention before that the preferred sound IEMs had less energy in the bass region and in the1 to 5 KHz range.

Personally I don’t like the Harman IE target as it don’t sound like over the ears headphones adjust to OE Harman target. Also we can see from the research papers the 50 to 70 preference group IEMs that all of them as an average have less energy in the 1to 5 KHz and less bass energy between 20...

For simplicity lets call the 1-5Khz region the presence region. My point is that very respectable IEM companies like Sennheiser, Westone , Shure and Ultimate ear have different IEM tuning target than the Harman IE in mind, and I think their target is closer in sound to over the head...

Both of your statements are incorrect. The graph is in the IEMs presentation section (slide number 107) starting in slide number 77 and ending in slide 116 on the Harman presentation PDF. The pinna gain region in IEM (1-3Khz) is trying to compensate for the non existence of pinna and the gain...

Reading Harman information slide "Relationship between headphones reference and amplitude response" There are three groups of preference ratings: 1.6 to 9 - This group with the lowest preference', all the IEMs tested have big bass boost and most of them around 10dB Pinna gain. 30 to 49 - This...

I will add that the EQ of the IEMs is done on IEC711 rig, and I don't believe the issue is some headphones variation in production. The differences is too significant to my ears especially in the 1-3Khz region. It also looks like that companies like Sennheiser, Westone , Shure , Ultimate ears...

I equalizing few IEMs that I have to Harman IE target , and they always sound total different from the Harman target poster boy headphone the AKG K371, or any other over the ears headphones I have that was equalized to Harman OE target. With Sean Olive information that I was looking, I didn't...

I will appreciate any insight why at least to my ears over the ear headphones equalized to Harman OE target sound total different from IEM equalized to Harman IE target.

I will add: I am only talking about sound quality. I am not talking about build quality , materials and so. I understand that people are satisfied with what they have , but because most of them are not trying to improve by EQ. I have good amount of headphones and IEMs and each one of them I was...

After spending a lot of time and money with this hobby I think that I can define my IEM/Headphones axioms. 1. There is no correlation between price and sound quality. 2. There is no a perfect sound headphones/IEM. Each have some frequency response flaw. 3. Every IEM/headphones will benefit from...