[xrk971]

It's alive!

But no sound. I'm using a male male audio from phone to input, and my headphones in the output. IL dig in deeper tomorrow.

Hmm... you are the first to get no sound at all. First thing to check (wearing an ESD wrist strap) is to use a DVM and probe between ground and pin 3 of the MOSFET and ground and PIN 1 of the MOSFET.
Pin 1 should be around 9 to 11v and pin 3 around 5 to 7v depending on battery level. Those dc voltages tell you that the JFET and MOSFET are operating correctly and not damaged. If pin 3 is circa 0v to 2v it's probably got a blown gate from a ESD zap. If pin 1 is unusually low, the JFET may have a blown gate from an ESD zap. I hope you took precautions for static discharge during all handling and assembly. The FETs are very sensitive.

If the amp is working, the MOSFET and R7 array will feel warm to the touch. Again, only touch if you are strapped in with ESD grounding strap.

Good luck!

 

[xrk971]

The Ronson lighter fluid works well as it leaves no residue of its own. I sometimes do a second wipe with denatured ethyl alcohol. I always wipe with ethyl alcohol before beginning SMT reflow soldering with solder paste.

 

[mds2004]

Hmm... you are the first to get no sound at all. First thing to check (wearing an ESD wrist strap) is to use a DVM and probe between ground and pin 3 of the MOSFET and ground and PIN 1 of the MOSFET.
Pin 1 should be around 9 to 11v and pin 3 around 5 to 7v depending on battery level. Those dc voltages tell you that the JFET and MOSFET are operating correctly and not damaged. If pin 3 is circa 0v to 2v it's probably got a blown gate from a ESD zap. If pin 1 is unusually low, the JFET may have a blown gate from an ESD zap. I hope you took precautions for static discharge during all handling and assembly. The FETs are very sensitive.

If the amp is working, the MOSFET and R7 array will feel warm to the touch. Again, only touch if you are strapped in with ESD grounding strap.

Good luck!

 
I should have worn the strap from the beginning and that is most likely the cause. I thought I was careful but obviously was not. Would I be able to just replace the FETs, or do I have to resolder a new board with new parts?
 
Mosfet M1A
      Pin 1: 2.42V
      Pin 3: .66V
 
Mosfet M1B
    Pin 1: 2.42V
    Pin 3: .02V

 

[xrk971]

Sorry to hear that. It's not clear if the JFET is the culprit or the MOSFET.  Remove the MOSFETs first then measure pin 1 of the MOSFET again (voltage from JFET drain resistor).  If it is 11v your JFET is ok.

 

[xrk971]

Hi Mds2004,
Any luck fixing the amp?
X

 

[mds2004]

Not yet. Unfortunately I won't have time until this weekend.

 

[mds2004]

Ok so I went ahead and finished the second one and it works great! Unfortunately I forgot my ifi micro black label at work so I cannot compare until after the weekend. But initial impressions on my Sennheiser HD650s are good. I will also compare using my Monoprice Monolith 1060s and FLC 8s.

 

[bogde]

Ok so I went ahead and finished the second one and it works great! Unfortunately I forgot my ifi micro black label at work so I cannot compare until after the weekend. But initial impressions on my Sennheiser HD650s are good. I will also compare using my Monoprice Monolith 1060s and FLC 8s.

 

nice build, congrats!

 

[xrk971]

Great news!
Congratulations.

 

[stellarelephant]

Ok so I went ahead and finished the second one and it works great! Unfortunately I forgot my ifi micro black label at work so I cannot compare until after the weekend. But initial impressions on my Sennheiser HD650s are good. I will also compare using my Monoprice Monolith 1060s and FLC 8s.

Glad you've got sound! HD 600/650 have a reputation (not sure if its deserved or not) for being hard to drive. Or at least hard to drive well. How well does the Pocket Class A perform with them? And at what "clock setting" are you cranking the volume pot to? For my HD 598 I turn up to around 11:00 (with the board oriented cap-side-up, as you have yours.) I have dreams of upgrading to HD600 some day...hence my curiosity.

 

[xrk971]

I have had reports from a professional music producer who used this amp with HD600's and they rock. He had an O2 before this and he says the difference is amazing with this little amp. The music just sounds better.

 

[mds2004]

What do you guys use to test between different amps? It is difficult for my untrained ears to discern the differences change changing cables. 

 

[xrk971]

I made a small AB test box using two DPDT 12v actuated signal relays, a momentary on switch connected to a 9v battery and DC-DC step up to get 12v to drive relay,and qnty 6 x 3.5mm stereo jacks.  It lets me switch instantaneously between two amps using one source and one headphone.
 
Once level matched, it is very hard to tell the difference when switching. Many of these effects are more audible over longer term listening - especially effect of 2nd harmonmic profile on sound quality. That gives a subjective feeling of warmth and enhanced tonality, spaciousness. Some test tracks let you hear it right away.  Piano is particularly good as well as drum solos and very dry (like as in an anechoic chamber) acoustic guitar.
 
Here is an example of my AB test switch box:
 

 

[mds2004]

Very cool. I will look into some diy plans because I'm not seeing anything using the same source and headphones.

I thought about making something like this, and using 3.5mm splitter from the source to each amp, which would go into a/b.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.amazon.com/Sescom-SES-IPOD-AB-Stereo-MP3-Player/dp/B005TE7GP4&ved=0ahUKEwjStqixxvfSAhWr6oMKHa-RBVgQFgg7MAA&usg=AFQjCNHCPlZyoVp_cI5Zq-GuxPwLbpTJ0A&sig2=9FWeyVhSYyKQNNjHRxhitA

 

[HiGHFLYiN9]

  The amp in the photos above is X's current prototype, built with his hand-drawn circuit board and all SMT components.  DIYA member BabyDontHertzMe currently has two DIY PCB designs under development and soon to be available for printing.  One will use SMT components like the original, while the other will use all through-hole components...

When will the second one be available? I'm not enthusiastic about plucking at SMD resistors