I'm putting this out here just in case some are curious about the amp setup Zeos was showing while using the Tungsten.... so I watched many of the reviews on youtube for the Fosi ZA3 amps and they were all positive... at least for a speaker amp... the folks at Fosi got a request for them to add in the optional function of a mono amp switch... so two amps running mono ... one amp for left and one amp for right... sounds simple and for the price a very cool solution for a speaker setup...
So I was looking for youtube reviews on the Tungsten and there was Zeos with his desk setup and a couple different Tungstens, one pre production and one post production and I got curious what he was using for an amp... with a couple different youtube vids he tells you about the amps and another vid on how to build a XLR to banana cable to interface the ZA3 amps to the Tungsten... so I decide to try the setup myself and if I liked the headphone solution then great and if not then I'd just use the amps for my speakers... it was a win for me either way.... then Amir over at Audio Science Review posted his review of a Fosi Amp that is using the same Texas Instruments Chip -TI TPA3255 class D amplifier IC which on the specification page at Texas Instruments it is expecting to have a SPEAKER at the output of the Fosi Amp... if you look at the graphs Amir comments "Frequency response shows load dependency which all class D amplifiers in this price range show " and this is shown in the FR graph via a 4 ohm load and a 8 ohm load.... the graph shows that the Frequency and associated amplitude is elevated when the 8 ohm load is in place... and the 4 ohm load FR is perfect.. a Amir quote " In English, this means that depending on which speaker you use, the sound may be a bit bright or a bit dull if your hearing extends to 20 kHz. You can counter with EQ (which you better have for good sound in your room). " And with a Speaker of 4 ohm rating the FR is perfect for human hearing...
And this was all confirmed on the Texas Instruments Spec page.. you can read all about it here..
https://www.ti.com/product/TPA3255 ...
So right off the bat its obvious that the Amp Chip is expecting a Speaker and not a higher resistance headphone...Class D issue, part of the circuit is a speaker at the outputs.
I put together a list of parts that I think I needed to build up the exact system that Zeos was showing and to test it out. and awaited the parts to show.. then it was mentioned the setup could possibly be dangerous to your ears/headphones due to the elevated FR.... and so I dug into the specs a bit more and looked at the graph that Amir had posted... I came up with a couple of solutions to the potential issue by just adding the proper Resistive Load at the output of the Amps... the graph shows a perfect FR at 4ohm and so I bought power resistors (50watt) of 5 ohms and those were installed as shuts on the Amp outputs and on the other side of the shut R loads I placed the Zeos XLR interface cable... This solution works quite well but depending on your headphones sensitivity this doesn't help with the amount of power coming towards the headphone at the XLR connector.... So I wrote the Hifiman guys and they sent me a Hifiman HE adapter..
https://store.hifiman.com/index.php/he-adapter.html .... this small box has banana inputs and a single balanced XLR 4 pin output... but also has its own shunt resistor and level resistors to cut the power to the headphones.... so the setup ends up with a shunt resistor on the outputs of the amp to tame the FR elevation to normal FR and between the resistance of the headphone and the two level resistors the power is tamed... tamed but with plenty of headroom for any headphone... The source inputs to the amps is balanced 4.4mm to 3 pin XLR ... I got the cable from ifi audio
https://ifi-audio.com/products/4-4mm-to-xlr-cable/ and that cable was connected to a Fiio BTR7 for wireless/PC USB connection and a direct balanced connection from the Fiio M15s via 4.4mm output (variable) and with the wireless BTR7 and Iphone and M15s were used for testing input sources....
both amps utilizing the 48 volt Power Supply.. I turned the volume down to zero on the source inputs, low gain, and the volume knobs on the amps to zero and powered the amps on... plugged in a Hifiman HE6sev2 into the HE adapter... adjusted the amp volume control to 50% and began to increase the volume of the source until I heard a faint sound... rechecked everything again... and adjusted the volume knobs on the amps to full on power and listened to the headphones to make sure I wasn't over powering them.... and once I felt it safe I started to adjust the output of the source until I reached a good listening level and played many many different kinds of songs... it sounded great... amazingly great... after playing with it for a couple more days I wanted to hear exactly what was being added/subtracted by the mono amp configuration so I pulled one of the amps out and configured the setup with just one amp driving the left/right outputs.... there was ample power from just a single amp and the sound signature was the same... it just didn't have the same amount of power, but plenty of power for headphones.... so the testing was going great and I decided to put different headphones on to test those with the setup... Hifiman HE1000v2 (great)... Hifiman HE6sev2 (great)... LCD-X (great)... LCD-XC (great)...
LCD-4 (great)...
so thats my story... and I'm sticking with it... do I think it will drive the Tungsten... an absolutely yes, with authority
How is the sound signature... I can honestly say it is at the Burson Conductor3XGT as a compare....
any questions... feel free to ask away...