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Old 2nd February 2012, 04:17 PM   #651
sangram is offline sangram  India
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^^Here's a pic...
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Old 6th February 2012, 09:59 AM   #652
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That is disaster with 100 ohms across the output.
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Old 6th February 2012, 03:06 PM   #653
sangram is offline sangram  India
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Please explain your logic?

A preamplifier will be fine looking into a 100 ohm load. With the possible exception of some tube amplifiers.

Obviously you have not read the text, which on the previous page reads thusly:
Quote:
The pole of the relay switches the input between the signal input of the amp (T1) and ground (T2). The grounding of the input ensures that crosstalk between inputs is eliminated totally. You can use a low value resistor (100 ohm) on the ground leg to help the output device of the preceding stage short-circuiting (though in practical terms this is not a problem). All input throws and all ground throws can be connected to each other.
The operative word being 'can'. One is free to float the NC input but deal with the potential of crosstalk given the very small space within a relay and potentially high voltages (some preamps will do about 4V output).

I have however noticed that if you leave the input floating there is a lot of crosstalk between inputs and it degrades system performance.

Finally, I have implemented exactly this a practical preamp that is gushed over by its owner and everyone else who has heard it, classifying at the most transparent preamp they have ever heard. It partners a $2500 speaker, $2500 CD Player and a $3000 amplifier, and none of his equipment have any problems feeding the load for the few seconds/minutes that they are kept close to ground. Some preamp and output stages (see the Ivy that accompanies the Buffalo DAC) actually keeps the LM4562 output shorted to ground with nothing more than its output resistor (22ohm, IIRC) between the output pin and ground.

Faulty preceding stages will have lots of issues, but then the problem is not in this circuit.

I would like your explanantion of the word 'disaster', after you crunch some numbers to figure out why a preamplifier of output impedance of 50 ohms or less will have problems feeding a 100 ohm load. Once you do the math, it works out fine.
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Old 12th March 2012, 01:29 PM   #654
shaan is offline shaan  India
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Can anybody kindly tell me where I can find a PCB maker in Kolkata? Thanks.
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Old 12th March 2012, 05:50 PM   #655
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Quote:
Originally Posted by shaan View Post
Can anybody kindly tell me where I can find a PCB maker in Kolkata? Thanks.
You are asking for a PCB maker?!!!

Seriously, though - on hifivision web site, diy group buy boards from PCBPower have been excellent.

E-mail i.d. - sales@pcbpower.com / service@pcbpower.com / powersupport@pcbpower.com
Contact No. - +91 9662059093 / 9558800479 / 9724316136

Last edited by quadtech; 12th March 2012 at 05:55 PM.
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Old 13th March 2012, 05:43 AM   #656
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Quote:
Originally Posted by quadtech View Post
You are asking for a PCB maker?!!!

Seriously, though - on hifivision web site, diy group buy boards from PCBPower have been excellent.

E-mail i.d. - sales@pcbpower.com / service@pcbpower.com / powersupport@pcbpower.com
Contact No. - +91 9662059093 / 9558800479 / 9724316136
did you ever procure pcbs from PCBPower? can you pls tell us about its costing.
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Old 13th March 2012, 01:00 PM   #657
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Quote:
Originally Posted by Aucosticraft View Post
did you ever procure pcbs from PCBPower? can you pls tell us about its costing.
The recent group buys on hifivision have all been from PCBpower.
Their web site allows you to upload a gerber and get an instant online quote. It will
depend on how many you order etc.

I was not the organizer of the the group buy, so can't comment on costing, but
the group buy boards were of very good quality and the end cost was very
reasonable.
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Old 13th March 2012, 01:40 PM   #658
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Qtech thanks a lot. I got registered there. I also received a call from them. the work quality is definitely good. but cost is good for bulk buy.
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Old 19th March 2012, 10:59 AM   #659
rajesh is offline rajesh  India
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Don't think they cost a lot more than your local guys but their quality is very good. I've ordered sample quantities of even 4 layer PCBs from them for my project and have been a happy customer.
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Old 27th March 2012, 02:25 PM   #660
shaan is offline shaan  India
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Is there a shop in Kolkata where I can buy Toroidal transformers? I have searched in chandni market but couldn't find any. Thanks.
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