Sgheadphones DIY A47 pocket amp kit

[tropicalrips 0]

That's cool Tropical! Your amp built like a tank

 

But I think the transformer orientation better be turned 90 degrees to reduce hum My2Cents.

yes it is shape like a tank

if i turn the transformer 90 degrees, the side panels can't cover the amp, its too tight...

 

so far i don't hear any hum, the side panels actually hav wood patterns, i was thinking of making my own panels with real wood always wanted a wooden amp...

[Q00 0]

Erm back on track? Hows the kit comin along?

[tropicalrips 0]

i think jason is making some final changes/adjustments to a final version of the board this should be ver 3.0 with inputs from many people here, hopefully this will be the last change

 

the price of the completed amp may not be as low as we had hope for...but that is still subjective to individual builder and parts used, for example, the desktop case that i used for the ver 2.0 board is already $15, together with a transformer + regulated PSU, thats about $30++ more if using better transformer.

[knuxed 0]

anyway to ship the kit to malaysia if i pay for the shipping?

 

[huangyong 0]

anyway to ship the kit to malaysia if i pay for the shipping?

i think you should buy the boards, opamps, caps, and resistor; get other stuff from malaysia, it's cheaper there.

[skyskraper 0]

quick question, what is being offered in the kit? i would be interested in just the pot, pcb, and 1uF caps. but pot and pcb together would be doable too

[skyskraper 0]

also have any of you a-b'd it with a mint?

[bpribadi 0]

I a-b'd it with my amp which used the Jung's Multiloop circuit like the Pimeta, my amp sounds a tad smoother. But considering the components differences (pots, etc.) and the cost, I would say Jason amp (my modded version) is really good for the buck

[skyskraper 0]

cool. im just interested to hear what people think compared existing popular designs. if i get a chance to stop over in sing in jan (not sure yet) i will bring my pimeta 1.1 and cans for people to listen with

[jasonhanjk 0]

Ok, I am sold to bram's idea. Final revision will based on changing the dual opamp for ground to a single opamp.

 

Please please please don't give me any more idea on changing the amp design...

[tropicalrips 0]

Ok, I am sold to bram's idea. Final revision will based on changing the dual opamp for ground to a single opamp.

 

Please please please don't give me any more idea on changing the amp design...

so it will follow the second version layout but with single channel opamp for ground rite?

[jasonhanjk 0]

ya

[Q00 0]

Great news to hear guys.. any final ETA?

[aaa 0]

I will suggest using socketed pins for the gain control op-amp feed-back resistor so that the user can change the gain by simply swapping two resistors (for two channels)

 

The cost of one row of 32 pin socket is $1 in SLT (might be wrong since my memory is not very good), each resistor take 4pins (if you really want to save money you can cut it down to 2pins), that's about $0.25 cost for the socket pins per amp.

 

The cost of extra set of 2 resistors is only like $0.20.

 

It is best to use a gain as low as needed for the particular headphone, source lineout and user preferance, this reduce noise and also reduce the chance of of accidental turning the vol to a unbearable loud level which may cause damage to headphone/ear.

 

I believe the extra cost can be well justified.

 

If you are worrying that the socket in the gain feedback cause distortion, my experiance shows it's not the case. Any way all those bass boost circuit involve switches in gain feedback which is worse than socket.

 

The only potential problem I can see is that if the resistor drop out the op-amp will be of open circuit (which may be fatal to the headphone/ear). But is the resistor is firmly socketed today I don't see why it will fall out tomorrow.

 

If you really want to be safe you can parrallel one higher value resistor to the resistor socket.

In the case of one-for-all headamp with fixed gain, the gain is always set a pretty high level anyway since it's better to be too loud at max (you can always turn down the vol) than being not loud enough at max vol.

So the parralleled resistor can be choosen at a value that by itself set the gain to the level of the above case (one-for-all headamp), then the socketed resistor leave poeple with a choice to lower the gain, since a gain that is enough for everyone will be too much for most-ones.

Then when the socketed resistor drop out it will only be as bad as the volume accidentally turned to max in the above case (one-for-all headamp), which will be much more likely.

Edited December 25, 2004 by aaa

[jasonhanjk 0]

Sorry for the late reply. I just manage to find a PCB manufacturer in Malaysia and the cost is reasonable. Still waiting for quote. I gave up on China 'cos they got one very big problem. Copyright law.

While maybe will try the land of the dragon next time.

 

You can directly insert the resistor into the hole. There is metal contact. It is possible to insert a DIP8 socket for resistor but I did not try. I am currently using a gain of 2 for my Senn HD600.

 

 

 

 

 

The copper trace of this PCB will be covered by immersion silver. Yes silver.

Some question like to ask you guys. What color of silkscreen does you guys prefer?

White?

Red?

or Yellow?