jtfoo

The AD8620 can work close to it's spec max of 13 V. I've tried +-13.xx V with an overcharged SLA battery before.. Maybe it's oscillating? You can add some fast bypass caps to gnd near the V+ & V- pins of your opamps.

there was this great debate on if DC blocking caps were called coupling or decoupling caps. technically, coupling caps are deemed as caps which connect or couple 2 stages, in a tube amp, possibily a driver stage to the ouputstage or a preamp to the power amp, in this case, the amp to the cans.

 

the consenses that the chappies came to was it should be called coupling caps as the importance of the cap was coupling of stages and its main duty was to couple the AC signal between stages. i guess it can be called DC de coupling caps although many of us all it coupling caps...

Sorry, didn't know there was a great debate at all. I just follow what text books, my company's technical journals and amp datasheets described them.

I really wish I could own the RS-1. Since I already prefer the grado's lower range SR-125 over the DT880. The Grado with the right amp, really shiok for rock music..

another thing i think was mistaken, the DC blocking caps are known as coupling caps. de coupling caps are used in the power supply to lower noise floor and hash.

hacky boy,

Just do a search on DC decoupling on google. Or take a look at some national chip amp datasheet,e.g TDA7294.. DC Decoupling cap aka DC blocking cap aka ac coupling.

You should also know why the decoupling cap on the power supply are also known as bypass cap. It just the word, your choice to decribe which portion as it function, to decouple something or bypass another thing.

Most basic use for audio is in usually two places.

1. Power supply reservior. Usually eletrolytic, use to store charges. It smoothen the the DC line by reducing ripples too.

2. DC decoupling aka DC blocking cap. usually placed at input or output of the signal line to block DC. Your headphone or speaker don't like DC as it can kill them.

There're other uses for caps in audio, like bypassing power cap(item.1), filtering, crossover in speaker. But simple diyers like me, bypassing is as far as I go.

Some tolerance that I can think off.

K = 10%

J = 5%

H= 3%

G=2%

Not too sure of the rest of the alphabet.

Me also a user of Grado SR125. When I first gotten it I really didn't like it at all. Though it was fast paced which should suits me, but the bass detail are totally lost. I also had the Byer DT880 then and so the difference was obvios. Believe or not, I even prefer my Sony Eggos over the SR125. I was using the meta42 then.

Things began to change when I had my PPA. Especially with the bass boost circuit on it. The SR-125 much better. Depending on my mood, I would alternate between the DT880 and the SR125.

Another change took place when I finally built my Zen headphone amp. Now I only listen to the Zen amp with my Grado SR-125, it's my favorite rock music combo. Very fast and exciting.. I haven't touched my DT880 for some time now.

Thanks digi for providing the info, however they are too small for my project.. I'll have to give this one a miss.

I want to know the dimension first.... Looking for two case to fit my preamp. Digi hope you won't mind giving the dimension and the price, I'm on budget here. Hopefully cheaper than the Hammond case from farnell.

I like to silver aluminiun one...

Wonder where can we found such case in S'pore??

The only reason why there's an input cap(DC blocking cap) is to decouple the DC. Basically it prevents the DC from passing thru. The RC filter causing the low freq rolloff, which is unfortunately formed by the DC blocking cap and input impedance, is an unwanted side effect of this DC-blocking cap. Another undesirable side effect of the input cap is phase distortion in the bass. So having a large value cap to push the rolloff lower, and the bass distortion also shifted lower too. Having fast polyproplene caps will help too.

And I'm with Bprilda here, no cap is the best. No low freq rolloff and no phase distortion. But you just gotta make sure that there's no oracceptable dc offset coming before you decides on a no cap path.

And take note for students, they get 10% off upon showing their student card over at the farnell counter in Tai Seng road.

So got any student diyers here, who can help the uncle diyers for the discount?

Hmm, looks like Cat5 and power cables are quite popular choice for wires. But jtfoo, Cat5 too stiff to connect to input, vol pot and output sockets right? Or do you use it also for these points.

Thanks.

Cat 5 individual strand not stiff at all, at least to me. Last time I use coaxial cable for input signal, damn siong. When I switched to cat5, so much easier, and if you twisted them, noise level can be low.

For output I use individual strand for the Kimber 4TC speaker cable. The 4TC makes up of 8 strand of wire. Those 4TC are left over from my diy jumper for speakers.

For me, I use Belden cat-5 cable for low level signal. Cheap cheap at 80ct a meter, and you get 8 strands so effectively 80cts for 8m. Easy to work and bend into shape. And it's teflon insulated, like heady mentioned, resistant to heat.

For power supply , I stripped those powercord for computer. Again also cheap cheap or in my case free. Take from my company.

Drumma,

I think you should start afresh with this thread. Forget what's input impedance, what's high pass filter, what insulated wire ..etc at the moment. concentrate what you need to built the amp first.

Physically all those red blue line can use be the same wire. Don't get into cable selection until you have progress further. Resistors/ caps can get from Sim lim tower. Forget about audio grade one first.

Drumma,

okies, for the HDP, i think i know how the circuit is being connected but i still dun understand a few things.. maybe u can explain to me? the L-out and and R-out means go where? and what is the 1m?

 

thanks

logically L-out, R-out, goes to headphoe jack.

 

1m?? If it's the 1M, then it's the input impedance. 1 megaohms

Which one are you refering to?

i think i posted too many pics, quite confusing.. but a pic can tell a thousand words..

 

The 1st two pictures that says 'Pocket Cmoy HDP'

I copy that from headwize.com..

Someone from headwize must have like to turn anti-clockwise to up the volume. Anyway the sijosae's connection is the correct for normal people, IN to the right most pin, GND to the left most pin, with the shaft orientation on top.

huangyong,

I think the volume pot wired wrongly... Input should be on the right most pin, gnd on the left most pin. Unless you're the unconvetional type who like to up the volume with anti-clockwise turn.

Now I know Jason is aka Mr Cash...

For inspiration, try this korean guy

http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae

Though can't read korean, looking at the pics will do.

That's why we shouldn't broadcast the sample program too frequently.. Too many people knows about it, it'll get abuse more often and one day good things will end.

Brings me to mind an incident at echoloft where some young chap abuses the RS component free delivery for some cheap resistor. Now we have to either more than $100 for free delivery, anything less have to pay $7.

Hey, jtfoo. You bought items from them before...  

 

BTW, the TDA7294 kit set is very attractive priced. I'd bought 5 kitset from them to built multi channel amp. Used up 3 kitset, with 2 spare lying around.

 

Can organize a group buy??

Haha.. I can't read chinese very well to navigate thru all those menu. That time I tompang from Jason (admin of echoloft) to order. Anyway the more the merrier, becoz the shipping is fixed irregardless of amount of item Can't remember the shipping cost, but once divided among us, it's very cheap. The TDA7294 cost me about $35 each, including shipping.

yap...the CD Rom controller and the DAC looks interesting...

I did read somewhere that diyzone no longer accepts order for

the CDPro kit....is it true ?

If you have watched the recent video of the redubbed 'infernal affair' about CDPRO2, it pretty much says that there's no more CDPRO for the rest of us from Da Wu (guy from diyzone)

:

For that price and that material ( lots of dale resisotrs ) i think slight pop sound should be ok.. since a few hundreds vs $35 , not fair to compare them like that..

hehe.. just my .2 cent

Just for info. Thought you guys might want to know whats' the trade off for a cheap stepped attenuator. Becoz when you first read what's on the site, the impression I get it's as good as the expensives ones, but for very much less the price..

 

Anyway for the price its still good if you don't mind the occasional pop, since most likely you won't change volume too often. Here's some guide on how to contruct the stepped attenutator if you bought from diyzone.

http://www.penguinlovers.net/audio/Attenuator.html

http://www.diyparadise.com/stepped_atten.html

 

 

BTW, the TDA7294 kit set is very attractive priced. I'd bought 5 kitset from them to built multi channel amp. Used up 3 kitset, with 2 spare lying around.