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Old 7th December 2012, 04:36 AM   #361
Roushon is offline Roushon  India
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Some of the items in the web shop I suggested in my last posting are imported from Parts Express, US as I found out after seeing high price.

Roushon.
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Old 7th December 2012, 09:31 AM   #362
Roushon is offline Roushon  India
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One more information regarding the web shop diyaudiocart If there is any doubt (like excessive) about a price then ask them. They are new in business. I did the same and they corrected prices of few
items.

Roushon
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Old 7th December 2012, 06:45 PM   #363
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Quote:
Originally Posted by gmphadte View Post
Headphone amp based on a DRV134 driver ic would sound much better than this.

Gajanan Phadte
DRV134 has 50 Ohms o/p impedance & is suitable only for balanced line drivers application with typ. 600Ohms load. H/p impedance (16-600 Ohms) work best with "near zero o/p impedance" h/p amps i.e. no series o/p resistor or capacitor for optimal damping. This rules out single supply, capacitively coupled, power opamps with series o/p resistors ,tubes, BUF634, TPA6120 , PMP, onboard sound cards to the totally hopeless virtual or active ground based h/p amps. John Siau's newsletter The "0-Ohm" Headphone Amplifier: The Sonic Advantages of Low-Impedance Headphone Amplifiers | Benchmark Interaction is a must read.

I've tested some popular opamps for h/p amp application(ability to drive 16 Ohms) & they literally "hard clip" with the exception of JRC4556 & a distant second NE5532. BTW most opamps specs list load resistance above 600 Ohms or even 2K Ohms.

No offence & apologies in advance if this may offend you, but NwAvGuy has an offer of "500$ charity donation" blind test challenge between O2 & any other h/p amp. Needless to say nobody has accepted it till date!

Last edited by availlyrics; 7th December 2012 at 07:11 PM.
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Old 8th December 2012, 05:08 AM   #364
sangram is online now sangram  India
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^^NE5532 exhibits severe loading distortion below 1k output, read the Walter Jung paper. By 16 ohms, the distortion can be as high as 15%, or unusable.

Reducing an op-amp's output impedance to 0 ohms is a trivial matter of adding a suitably biased output stage driven by the opamp.

I've stopped bothering to look for good parts in India as the trader community here is just that. I import almost every single component now, and there are intelligent ways of doing ti without incurring too much by way of shipping/customs.

Here are a few links:

JRC4556AD Manu JRC Encapsulation DIP 8 NJM4558 Dual Operational Amplifier | eBay ($5 each including shipping)

OR

2pcs JRC 4556AD Grado RA1 Operational Amplif 1614 | eBay ($4 shippied to your door).

I would suggest pay for shipping and get them sent by registered post. Will be quicker and cheaper than 6 trips to the local market and the cost of electricity and bandwidth this conversation is taking.
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Old 8th December 2012, 10:12 AM   #365
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A very valid point made Sangram, unwarranted comments (incl. mine) leads to unneccessary escalations. I've chk your given links.
BTW Have you ever purchased anything from utsource.com or faced any issues when importing thru reg. post/parcel w.r.t. customs, P.O., e.t.c. for electronic spare parts? (Especially, we poor DIYers who import parts costing nothing more than a couple of $$. )

Last edited by availlyrics; 8th December 2012 at 10:15 AM.
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Old 8th December 2012, 05:12 PM   #366
sangram is online now sangram  India
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No problems with parts in small quantities. As long as it's in a paper envelope, coming by registered post, it gets in without customs delay (though this is locale-dependent).

It's when it becomes a box larger than one hand can hold, is when it gets checked and valued.

IME Fedex and UPS et al have longer customs delay and processing time than ordinary post parcel. I tend to prefer USPS and China/HK/Sing post.

Never used utsource (but I use five to six ebay sellers from China and UK and rarely have had any problems - you must understand that when I place fifty orders a year maybe one or two are destined for bad luck). WRT duty, depending on sizes Digikey orders do get valued and levied at appropriate rates, specially during my bulk order times (I buy a lot of FC and FM caps for my projects and they're not available here). Small packets, never paid customs, sometimes the unregistered ones are left in my letter box.
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Old 10th December 2012, 04:02 AM   #367
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Quote:
Originally Posted by availlyrics View Post
DRV134 has 50 Ohms o/p impedance & is suitable only for balanced line drivers application with typ. 600Ohms load. H/p impedance (16-600 Ohms) work best with "near zero o/p impedance" h/p amps i.e. no series o/p resistor or capacitor for optimal damping. This rules out single supply, capacitively coupled, power opamps with series o/p resistors ,tubes, BUF634, TPA6120 , PMP, onboard sound cards to the totally hopeless virtual or active ground based h/p amps. John Siau's newsletter The "0-Ohm" Headphone Amplifier: The Sonic Advantages of Low-Impedance Headphone Amplifiers | Benchmark Interaction is a must read.

I've tested some popular opamps for h/p amp application(ability to drive 16 Ohms) & they literally "hard clip" with the exception of JRC4556 & a distant second NE5532. BTW most opamps specs list load resistance above 600 Ohms or even 2K Ohms.

No offence & apologies in advance if this may offend you, but NwAvGuy has an offer of "500$ charity donation" blind test challenge between O2 & any other h/p amp. Needless to say nobody has accepted it till date!
No ill feelings at all...
I don't want to discourage u in any way.
And forget all these business gimmicks and reviews. U design your own and float such a challenge and u will be surprised that nobody accepts the challenge. Not worth it. Just now I read another post on this headphone amp and ...

There is a schematic on the net with BD139/BD140 output stage and a DRV134. Construct it and construct a shunt regulator psu. Nothing will beat it.

Not for challenges please.

Gajanan Phadte
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Old 10th December 2012, 05:35 AM   #368
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Quote:
Originally Posted by gmphadte View Post

There is a schematic on the net with BD139/BD140 output stage and a DRV134. Construct it and construct a shunt regulator psu. Nothing will beat it.
The prob. with Lamington Rd resellers is they first ask for qty. & then quote some ridiculous price e.g. M5216 OPAMP Rs150 (UTSOURCE 1$), UPC1237 Rs70(got for Rs30),OPA2134 Rs550(RS components home delivered Rs140 each). To top it all I got JRC4556AD DIP 8 from Delhi for Rs 90 /pc & all of them were fakes(reprinted). Thus its very difficult to design /chk. any new ckt. One just dosent knows if the prob. is with fake/ sub standard components or bad design or human error. After a failed project I remain sulk for weeks I think its better to import (Sangram's way) & hope for the best,
Cheers.
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Old 10th December 2012, 08:30 AM   #369
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As Roushon mentioned, u cannot buy these components locally. Many years(nearly 2decades) back, I purchased TIP130/135 from Mumbai. They r supposed to be complements of each other. When I assembled the amp believing the numbers, it wouldn't work. Then I found that both were NPNs. A lesson learnt from fakers and from then onwards, I check each and every component before soldering.

Gajanan Phadte
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Old 11th December 2012, 02:22 AM   #370
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Quote:
Originally Posted by availlyrics View Post
I've been following nwavguy's blog for quite some time(He has stopped updating from last May 2012 though). The objective analysis & measurements plus comments are very exhaustive & in depth but at the same time very "enlightening". A must read for all DIYers.

For detailed explanations-
NwAvGuy: O2 Details

Dispelling opamp myths-
NwAvGuy: Op Amps: Myths & Facts

Objective measurements of different opamps-
NwAvGuy: Op Amp Measurements

nwavguy a.k.a. RocketScientist thread-
The Objective2 (O2) Headphone Amp DIY Project

I've got PCBs for the same from jtkam at diyaudio.(a kind DIYer from Canada who has given away more than 100 PCBs free all over the world with the only condition that 5$ per PCB be donated to diyaudio.com & a postcard to him. Well that might explain my "single star" status)

If any body in Mumbai wants to hear this headphone amp(I'm going to build with smd JRC4556 for the time being), they can PM me.

Thanks,
availlyrics
Thanks, availlyrics.

I think you should stick to what you are doing and Prefer no change. If finding part is a problem, then sure in some part of world its available.

good or bad opamp, audio op amp or general opamp, is a very subjective and much depends on how it is configured or used. Lot parameters need to be considered. there is one good thread started by Mooly. He did exactly what I had been asking for , he has used O'scope to show how the best called opamp prove worst if not handled properly. bt despite of all you will find lot of threads discussing "better equivalent for xxx opamp".
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