The design for the GB is now completed:
http://www.diyaudio.com/forums/grou...led-class-hpa-sub-ppm-thd-10.html#post5479429
http://www.diyaudio.com/forums/grou...led-class-hpa-sub-ppm-thd-10.html#post5479429
GB PCBs have been ordered. There are a few boards left if anyone is interested.
Simple High Performance DC Coupled Class A HPA with sub PPM THD
Simple High Performance DC Coupled Class A HPA with sub PPM THD
I am not familiar with the amps you mention above, other than the Dynalo by Kevin Gilmore - the same designer of the Dynahi SuSy. Someone brought his Dynalo (quite a complex amp for being the simpler designs by Gilmore) over to my lab for a controlled blind AB test with 3 experienced listener subjects (people with lots of amps and headphones) with my SE Pocket Class A amp. My little 2 transistor amp literally crushed the Dynalo in all aspects of sound stage, bass authority, imaging, and realism. I am sure Kevin Gilmore "Dyna-X" designs are nice amps, but they tend to be complex push pull Class A affairs, that achieve higher powers in Class B - you can tell this by the size of the heatsinks - they are way too small for the claimed powers of tens of watts. So not sure about the Dynahi or Super Symmetry (NP patent) version of it, but I think that in general, a SE Class A amp, with fewer actives, and less feedback, will sound better and more natural than a complex push-pull Class A.
This amp is pure SE Class A, and has a dynamic CCS that is similar to the Nelson Pass Aleph. So this amp and the Dynahi SuSy have Nelson Pass in common...
I have built over 2, maybe 3 dozen headphone amps of many different topologies. I keep coming back to SE Class A for the best most realistic sound.
This amp design by TimS achieves SE Class A and does it with an all DC signal path so that capacitor coloration does not get in the way. It is very transparent, natural, and powerful sounding. I think quite good - up there with the best of my amps.
Hope that helps.
Thanks a lot X for the comparison. I'm actually expecting a Dynalo Mini board from a group buy to arrive and build that. I mainly built the Dynahi as a be-all-end-all endgame amp since it is capable to drive anything all the way up to a HE6. However my gain is halved to cater my high sensitivity cans. Its kinda too clunky and big, requiring a separate but full sized chassis to house the PSU. Perhaps the Dynalo Mini or this simple class A could be what I'm looking for.
Now, what's the name for this amp?
Amp is now completed. Sounds fantastic! Very powerful and clean.
Simple High Performance DC Coupled Class A HPA with sub PPM THD
Simple High Performance DC Coupled Class A HPA with sub PPM THD
Beautiful work BDHM! You never even said you were making one until now. 
What are you using for the PSU?
I boxed mine up and it’s using the DC-DC dual rail supply with cap Mx and LDO regulators.
M
The bass is indeed very good, and so is everything else. It’s a fine neutral amp with some guts.
What are you using for the PSU?
I boxed mine up and it’s using the DC-DC dual rail supply with cap Mx and LDO regulators.
M
The bass is indeed very good, and so is everything else. It’s a fine neutral amp with some guts.
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Beautiful work BDHM! You never even said you were making one until now.
What are you using for the PSU?
To be honest, I'd pretty much forgotten about it. I don't even recall including it in my last PCB order!
I'm using a Rigol bench PSU at the moment. I'll give it a try with the UltraBiB once I've finished building it. I am thoroughly intrigued by your SMPS solution though - I love the idea of being free of the tyranny of transformers
.I'll run the amp through my Quantasylum later today.
Yours is looking amazing, X!
Here are the QA401 results. These were made with everything just sitting on my desk, exposed wires and all.
THD at 0.5Vrms 1kHz is 0.0013%. The others are 1.1Vrms 1kHz and frequency response. Interesting minor upsweep at high frequencies.
Note: this is for my basic through-hole version. I am certain the full-fat JPS version will be better.
THD at 0.5Vrms 1kHz is 0.0013%. The others are 1.1Vrms 1kHz and frequency response. Interesting minor upsweep at high frequencies.
Note: this is for my basic through-hole version. I am certain the full-fat JPS version will be better.
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Those look good BDHM. For reference, here is the JPS64 layout driving 1Vrms into 600ohms:
And here is 0.35Vrms into 47ohms:
What kind of measurement ADC are you using? Odd that the low frequencies drop below noise floor of -130dB (same on both our setups). I find that DC coupled amps have a rise in the low bass due to lack of a high pass input coupling filter that would otherwise block infrasonic rumble.
Your background noise floor shape might be noise from your PSU.
And here is 0.35Vrms into 47ohms:
What kind of measurement ADC are you using? Odd that the low frequencies drop below noise floor of -130dB (same on both our setups). I find that DC coupled amps have a rise in the low bass due to lack of a high pass input coupling filter that would otherwise block infrasonic rumble.
Your background noise floor shape might be noise from your PSU.
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Oops! I forgot to mention, the tests were done into a 32ohm load. I'll do the same tests with 600ohms later tonight.
To quote the QA401 product page: "The input stage to the AK5397 ADC consists of a relay attenuator, an OPA1612 buffer, and an OPA1632 diff amp"
Good point. I'll throw a capacitor in front of the amp and see what happens
Yep. Plus fluorescent lights and nearby SMPSes.
To quote the QA401 product page: "The input stage to the AK5397 ADC consists of a relay attenuator, an OPA1612 buffer, and an OPA1632 diff amp"
xrk971 said:
Good point. I'll throw a capacitor in front of the amp and see what happens
xrk971 said:
Yep. Plus fluorescent lights and nearby SMPSes.
