DIY Headphone Amp #3 - Starving Student Hybrid

[PJPro]

£94

 

[PJPro]

Phenomenal value!

 

[PJPro]

I've been having one or two problesm with this amp.

One of the LEDs became a bit flickery and went on and off as I moved the tube. Turns out the positive wire had snapped where it was soldered to the PCB. Worst still, I had real difficulty clearing the hole. I tried Trevor's red hot needle trick....it didn't work. I almost lost it a one point. I ended up damaging the PCB and am now unable to solder the LED wire to it. Damn! Anyway, I managed to solder the positive wire directly to the LED resistor so it does still work although it's a bit of a bodge.

The other issue's a little more of a problem. The balance between the headphones isn't right. Things sound louder in one phone than the other. I've taken a number of readings around the circuit as suggested by the designer and it would appear to point to the volume pot not applying the same resistance to each channel. It is especially evident at low listening levels. The solution is to add some additional resistance to the louder channel or buy another pot.

Hmmmm. Where'd I put that Novo?

 

[Tony_R]

Do you have a desolder pump? (also known in some circles as a solder sucker)

You could also try solder wick, but I find that less effective for clearing holes.

For through hole plated boards, a desolder pump is very effective. I find the best way to do it, is to run some fresh solder over the hole, then apply the pump. It's also better to remove any remnants of wire in the hole first.

Hope you find this useful.

Tony.

P.S. Your kit endeavours have made for interesting reading.

 

[PJPro]

No, I don't have a pump but do have the copper braid. I'm not overly keen on the braid....seems to take an enormous ammount of heat for it do to anything.

I have seen the pump you've linked to but never really felt the need. Perhaps I should invest.

Thanks for the advice.

 

[PJPro]

Tony_R:
P.S. Your kit endeavours have made for interesting reading.

Did you enjoy the debate over rectifiying AC to DC?

 

[Tony_R]

PJPro:Tony_R:
P.S. Your kit endeavours have made for interesting reading.

Did you enjoy the debate over rectifiying AC to DC?

I'm guessing you're referring to this post

And yes I did!

As a rule of thumb, to calculate DC voltage I would multiply the AC output of the transformer by 1.414.

But of course as pointed out in your posts, there are other things to consider such as losses / transformer regulation etc.

Back in the 80's when I used to repair television sets, we made a lot of use of the lightbulb trick as well.

We did have variacs in some workshops but not all, hence the need for the lightbulb.

Keep up the good work - I like your resourcefulness to - you have provided a couple of good links for my bookmarks!

Tony.

 

[PJPro]

Thanks very much Tony_R.

I do need to do some more on the Dual Mono Power amps. That project has stalled....although I could write up the next thrilling installment on disconnecting networks.

 

[PJPro]

Tony_R:
As a rule of thumb, to calculate DC voltage I would multiply the AC output of the transformer by 1.414.

You could have chipped in!

 

[Tony_R]

PJPro:Tony_R:
As a rule of thumb, to calculate DC voltage I would multiply the AC output of the transformer by 1.414.

You could have chipped in!

Sorry - I was playing catch up and only read that thread yesterday (Sunday).

 

[Tony_R]

PJPro:Thanks very much Tony_R.

I do need to do some more on the Dual Mono Power amps. That project has stalled....although I could write up the next thrilling installment on disconnecting networks.

You're having network problems?

Sounds like fun..

 

[PJPro]

Tony_R:
....You're having network problems?

Not exactly. I'll try and write something up (but in the other thread) shortly.