Congratulations! You are fast!
It's normal for the parts to be warm. It's the radiation and conduction. What is your bias current through the four 470R resistors? 17.9v is a bit higher than 16.4v nominal of two rechargeable batteries so will be running hot. If bias is more than 55mA you can adjust R4 to a slightly lower value. But test with batteries to set bias as this is what you will be using it at.
Do you have any higher impedance phones to listen with - how is the sound?
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^^ I had only very short time to test, but I tried it with my Audeze LCD-2 (fazor) that are 70 ohm. Massive Attack's Angel sounded quite convincing. I'll try to find time to listen to it properly and with music I normally listen. This was just a test track for me. I'm just not very good at describing sound differences.
Interested to see that this little amp can power orthodynamic headphones. I'll have to test out Hifiman HE6.
pcgab - 2 boards - SHIPMENT RECEIVED
zman01 - 1 board
stellarelephant - 2 boards - SHIPMENT RECEIVED
samoloko - 1 pcb
Morde - 2 board - SHIPMENT RECEIVED
cyteen - 2 boards
funch - 2 boards - SHIPMENT RECEIVED
syyma - 2 boards - SHIPMENT RECEIVED
av-trouvaille - 2 boards - SHIPMENT RECEIVED
Mituisho - 2 boards
bogde - 2 boards - SHIPMENT RECEIVED
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards - SHIPMENT RECEIVED
dwpeterson - 2 boards - SHIPMENT RECEIVED
agdr - 1 board
walangalam - 2 boards SHIPMENT RECEIVED
gwrskien - 2 boards - SHIPMENT RECEIVED
redarc12- 2 boards
dw1narso - 2 boards
zimmer64 - 2 boards
shambala - 2 boards - SHIPMENT RECEIVED
HaroldHill - 2 boards - SHIPMENT RECEIVED
gig - 2 boards
hui13 - 2 boards - SHIPMENT RECEIVED
pranavkr -1 board - SHIPMENT RECEIVED
JimS- 1 board
Kumori - 1 board
tubediy - 1 board
AKSA - 1 board
zman01 - 1 board
stellarelephant - 2 boards - SHIPMENT RECEIVED
samoloko - 1 pcb
Morde - 2 board - SHIPMENT RECEIVED
cyteen - 2 boards
funch - 2 boards - SHIPMENT RECEIVED
syyma - 2 boards - SHIPMENT RECEIVED
av-trouvaille - 2 boards - SHIPMENT RECEIVED
Mituisho - 2 boards
bogde - 2 boards - SHIPMENT RECEIVED
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards - SHIPMENT RECEIVED
dwpeterson - 2 boards - SHIPMENT RECEIVED
agdr - 1 board
walangalam - 2 boards SHIPMENT RECEIVED
gwrskien - 2 boards - SHIPMENT RECEIVED
redarc12- 2 boards
dw1narso - 2 boards
zimmer64 - 2 boards
shambala - 2 boards - SHIPMENT RECEIVED
HaroldHill - 2 boards - SHIPMENT RECEIVED
gig - 2 boards
hui13 - 2 boards - SHIPMENT RECEIVED
pranavkr -1 board - SHIPMENT RECEIVED
JimS- 1 board
Kumori - 1 board
tubediy - 1 board
AKSA - 1 board
Those are some impressive headphones - claimed to be the best without regard to price by the manufacturer. However, they are only 83.5dB sensitive and are 50ohms impedance. That says they need 10v to drive them adequately and I don't think this pocket Class A amp is designed for that. With a 50mA bias current, while the HiFiman HE-6 needs upwards of 200mA for the full dynamic impact. I will guess that you will be disappointed - because this is not what they were designed for. So I am just warning you that this is not a good match.
Do you have more transitional cans like HD600 or DT880's or Grados and AKG's that have mid 90dB sensitivity, and 60ohm to 300ohm impedances? Those will be much more well-matched for this amp.
Hi, I belive everyone is waiting for the verdicts from GB1 builders
Regards
You are right about that. I am pretty confident that GB1 builders will love the sound. I have over a dozen amps to compare and even though small and pocket sized, it impresses me when compared with the big boys when I used my DT880's (250ohm). I will prefer to listen to this pocket amp over some much more serious equipment that I have.
So let's standby while builder reviews come in...
Great news
I am so glad I test built it before sending them out. There is no question that this amp works well the first time.
Please be careful with ESD though. Until it is inside a metal case - always wear a wriststrap or work in an area that has a grounded table and you touch grounded objects all the time.
I just remeasured this amp with the rig moved to a (electrically) quieter room. The THD (for 1kHz and 700mV into 270ohms) is 0.028% and the noise floor is -126dB, dynamic range is coming in at 94.5dB and IMD is 0.026%. Frequency response is utterly flat.
FFT:
Freq response and THD:
FFT:
Freq response and THD:
Attachments
My bias currents are 48,5 mA and 53,2 mA @ 16,3 V power supply feed, so a little imbalance but I don't know how much it really matters. Music is playing very nicely and when comparing to Salas DCG3 the differences are surprisingly small with LCD-2 cans that are relatively sensitive (101dB/mW). I know it's an unfair comparison, but the bass is more solid and overal effortness is there with DCG3. Anyway very well done mr xrk971 considering how small and affordable this Class A Pocket amp is! Thank you very much for releasing it.
Good old Megadeth is making my head go back and forth and hands air guitaring as I'm trying to write this...
Good old Megadeth is making my head go back and forth and hands air guitaring as I'm trying to write this...
Good old Megadeth is making my head go back and forth and hands air guitaring as I'm trying to write this...
Sounds like you're having fun! Which album?
My bias currents are 48,5 mA and 53,2 mA @ 16,3 V power supply feed, so a little imbalance but I don't know how much it really matters. Music is playing very nicely and when comparing to Salas DCG3 the differences are surprisingly small with LCD-2 cans that are relatively sensitive (101dB/mW). I know it's an unfair comparison, but the bass is more solid and overal effortness is there with DCG3. Anyway very well done mr xrk971 considering how small and affordable this Class A Pocket amp is! Thank you very much for releasing it.
Good old Megadeth is making my head go back and forth and hands air guitaring as I'm trying to write this...
Thank you for the candid review. I do not expect to beat the DCG3, a marvel of audio engineering by a Jedi-Master of electronics
However, having you say that the differences are surprisingly small, makes me feel better. Your bias currents are about right. If you match your FETs and MOSFETs, they will be within 1mA. You can get a little more slam out of the amp by increasing R4 from 33R to 47R. It will run a bit hotter, less battery life, but might be worth it to you. Easy to try
Nicely done and quickly done!