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One polar connector for battery/adaptor Another non-polar connector for on/off switch. I like the flexibility.

case opened.

finally finished the amp

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.

Heady you are my life saver!!! which popular branch did you see it? $1.3 is cheap for any type of puncher. In fact I have tried using my normal puncher, it does work very well, but with the shape of tin it's just impossible to reach the place I want to punch. a puncher of plier shape, it's easy to imagine how it works.

Thanks for all your compliments. Am I a surgeon? I'm just a slack ORDing NSF, with all the free time. There's some thing I need the help of you all, How can I drill a good hole on the tin without buying a power hand drill? When I get my pot from Heady, I will start to finish the final details. at the mean time I will start to kick off my PPA clone, which will about 15X the volume and 25X the weight of this Pimeta clone. The experience I had from the PIMETA Clone will definitely help.

all caps are from koba. the blue one is 2.2uF 50v polyester the purple electrolytic is 20v 180uF OS-CON SP series. the rest you should be able to read from the picture. now waiting for Bram to sent me the CRDs. Still cannot decide whether to buy the alps RK9 pot from farnell. it cost like $10!!!

the design is basically a Pimeta clone, a pimeta in a MINT! it is not fully completed yet since the volume control pot is by-passed, the CRD for biasing op-amp into class-A is not installed, and most importently the thing is not put in a mint casing yet. total RETAIL cost for all the parts exc tools/batterys is very close to S$100. the surprising thing is that it runs on the first try! (although I have tested and corrected multiple error b4 acutally running it, including a spoiled OS-con). This amp is actually my warm up for the coming PPA clone. I was thinking of trying something easier first b4 actually solder the PPA, my PPA layout is already standing by... As I progress I believe this amp can actually be more difficult to solder due to the density and the number of cross junctions. updates: Just received the CRD from Bram. Installed, still evaluating. Thanks Bram! 1st evaluation of audio quality. with AD8620 and AD8610, gain set to 1 (jumper wire), line-out from creative nomad jukebox3, single 9v zinc-carbon battery, senn HD-650 compared to the headphone out of jukebox3 (which has output cap modded), the bass is much stronger and deeper. Speed seems to be faster. many minute details which are never heard of b4 can now be noticed. overall the differents compared to headphone out is very noticable will add more comment reg later

What volume pot is that and where did you found it? The pot I bought is too big for tin.

Everyone building an amp will need many parts. Most of the parts in anyshop are irrelavent to the need of an headamp. Why not keep a list so that the junior don't have to waste time on items the pioneers have already found. This list will be particular for PPA, but parts for most amps are more or less the same, it should be useful to ppl building other amps as well. Let me start the list C1 Nichicon Finegold 25v/33uF @ Koba, People's park centre 2nd floor The right size DxH 12.5x20 for offical PPA PCB in harmond casing C2, C4 Blue 2.2uF/50v polyester unknown brand @ Koba cheap cap that will fit in offical PCB C3 Wima MPS-? 68nF/63V @ Koba The right size WxD 2.5x7.5 for offical PCB R10, R11-14 1.43K�6¾8 1/4w, deep blue,unknow brand, good looking, need 4 hole width @Koba Although the offical value is 1K, but 1.43K is just as fine. 0.1% mean good quality. Q1, Q2, Q3 2N5484 and 2N5486 are available at Farnell. Federal component in SLT 2nd floor handle them @ $1 each TLE2426 available at Farnell. Federal component handle them @ $3.50 each Buf1 Intersil HA3-5002 available at Farnell. Federal component handle them @ $7+ each for q>10 Volume pot Koba currently (Oct 2005) have some stock of ALPS 27K series 50K stereo Log type potentialmeter. $15 each. please add on to the list by copy the list and then edit it.

can share where you get the Klotz and Neutrik Pro-fi RCA connectors and for how much. I believe I'm not the only one interested in DIYing a mini to RCA cable like yours. Thanks!

What is this light blue material? from the lable on PCB they should be resistors, may be from another series.

Bram If the parts that you help me brought is ready by then, how about meeting together on Sat 13? But I'll have nothing to contribute for this time round.

Never thought of reusing the socket... your method has near zero cost!!!

what's high power CMoy? A CMoy with buffer stage?

Very useful info. But the last photo is not the right one.

Hi Bram, sure or not? your PPA will only be done by next year? I thought I'm the only person who is so draggy...

digi01, where did you found these 1/8 watt DALE resistor?

I thought he was talking about 1/8" jack, my mistake. anyway I was charge $14 for the same thing at the same place, next time must do more homework before buying.

Isn't it a 1/8" jacks casing mounted

I can assure you that Bram's PPA will be far more portable than mine. I'm planning to use a case of 105x285x60mm without any empty space inside left. with 20AA NiMH (on a 2nd layer battery board) inside it isn't going be light either. I'll only be use it in a portable setup when I'm traing for a backpacking trip... If I have the chance to design it again I will make it smaller. anyway these will only be a problem after I get my PPA done and working...

If fact I will prefer cells with lower energy density, even if price is the same. (Where to buy industral NiMH cells???) That's becasue cells with higher energy density tense to have higher self-discharge rate, less cycling life, and these are what I care more about. I'm planning to use HD650, with 300ohm imp power=I^2*R lets say I will be listening at 100mW/channel power (that's rather loud) 0.1w=I^2*300 I=18.26mA (dynamic current, exclude the static current drawn by op-amp & buf) since PPA has 3 channels, that's about 55mA dynamic current drawn lets say each AA NiMH cell has a internal resistance of 0.025ohm (from Sanyo date sheet for AA NiMH 2100 @1Khz after discharge to E.V.=1.0v) 0.025x20=0.5ohm Since V=IR the load-modulated ripple voltage= 0.5ohm x 0.055A = 27mV that is very low in my view I plan to have a build-in triggle charger, So I leave it charging while not in use. You AC power will be plugged while in use, this is not that much of a difference in my view.

I'm planning to use 20 Sanyo 2100mAH NiMH AA cells in series to power my future PPA. Sanyo 2100mAH is bcos it is $3 a piece, I can't find cheaper NiMH AAs. NiMH is for the low internal resistance and not so sig memory effect. the number 20 is a compromise between feeding enough voltage to the OPA627/637 and not buring the AD8610 (absolute max rail to rail 27V) there in a protection diode that will take up 0.75v and the Q3 will eat up some more voltage. Thinking of a build-in Trickle charger. Where to find cheap 5v to 30v (or +-15 should do as well) DC-to-DC adaptor? (charge by USB cable) or should I just add a AC to DC adaptor inside(for charging).

The PCB and casing size does not allow me to do that. I think I will be having both the RCA input and Pot in front (same side) in that way the wiring will be just as short as what you suggested.