ok, this is a subject which i think is pretty interesting. i must say that there is an interest on this forum about balenced inputs and outputs.
now so far the best gainclone only balenced implementaion was just 2 amplifers giving a differential in - differential out.
the only single gainclone implementation i've seen was a AC-coupled difference amplifer. the problem is that this circut isn't balenced unless there is no signal or noise. otherwise the noise rejection will depend upon the voltage to the noninverting terminal, so more noise = less rejection of noise!
i made a simple volume control that is balenced, but it is obviously conditionally balenced -- it works on the principle that the source and destination is balenced.
now i was looking over the specs of the lm4780, mind you not the choice of many, but still the CMRR of the chip falls severly, so any noise rejection will be limited more to lower frequencies. fine this works for hum if hum is the problem.
so i wanted to start a hopefully meaningful discussion on how best to implement a balenced input amplifer
now so far the best gainclone only balenced implementaion was just 2 amplifers giving a differential in - differential out.
the only single gainclone implementation i've seen was a AC-coupled difference amplifer. the problem is that this circut isn't balenced unless there is no signal or noise. otherwise the noise rejection will depend upon the voltage to the noninverting terminal, so more noise = less rejection of noise!
i made a simple volume control that is balenced, but it is obviously conditionally balenced -- it works on the principle that the source and destination is balenced.
now i was looking over the specs of the lm4780, mind you not the choice of many, but still the CMRR of the chip falls severly, so any noise rejection will be limited more to lower frequencies. fine this works for hum if hum is the problem.
so i wanted to start a hopefully meaningful discussion on how best to implement a balenced input amplifer
theChris said:so i wanted to start a hopefully meaningful discussion on how best to implement a balenced input amplifer
Here's my two cents worth.
se
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GregGC said:What do you say about that?
the input impedce for input 1 is dependent on the input voltage for input 2, thus the circut isn't really balenced, just a difference amplifer.
as for the transformer, well, no arguments there
do a search on the google for superbal
you can find an example circuit here
http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm
you can find an example circuit here
http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm
How about a tube balanced to unbalanced converter, as the buffer of an IGC?
http://www.tubecad.com/june99/page12.html
http://www.tubecad.com/june99/page12.html
mskeete said:do a search on the google for superbal
you can find an example circuit here
http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm
This is one of the pages I read when making my bal. gainclone
I can't understand what all the fuzz is about. min. 45dB CMRR, and 0,00078dB signal imbalance (10 ohm SE output Z from source). Who needs higher performance than this for audio?
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Re: Re: Discussions on Balenced Amplifers
A much better idea than most of the others presented.
Steve Eddy said:
Here's my two cents worth.
se
A much better idea than most of the others presented.
Re: Re: Re: Discussions on Balenced Amplifers
Thanks. It's worked for me for quite a few years. Though it can be considerably more expensive than some of the others presented.
se
Brett said:A much better idea than most of the others presented.
Thanks. It's worked for me for quite a few years. Though it can be considerably more expensive than some of the others presented.
se
Ssm2142 / Ina134
Transformers are best, but....
The best non-transformer, non valve solution:
http://www.analog.com/Analog_Root/productPage/productHome/0,2121,SSM2143,00.html
Transformers are best, but....
The best non-transformer, non valve solution:
http://www.analog.com/Analog_Root/productPage/productHome/0,2121,SSM2143,00.html
Mad_K said:
This is one of the pages I read when making my bal. gainclone
I can't understand what all the fuzz is about. min. 45dB CMRR, and 0,00078dB signal imbalance (10 ohm SE output Z from source). Who needs higher performance than this for audio?
well, the circuit isn't balenced. while it is capable of canceling equal noise on both inputs, it is not capable of picking up the same noise on both inputs. if it were balenced, i would not be able to pick up all that hum on my crossover (which uses the circiut with less gain as an input buffer). i can pick up hum by moving the cables near a transformer.
Re: Ssm2142 / Ina134
You're welcome. The initial cost is an issue, but there's all the advantages the Tx's have, and providing you don't toast them, will hold their value well for later resale.
Well John, the 2142's had better have improves a lot since I last used them, because they sounded dire.
Steve Eddy said:
Thanks. It's worked for me for quite a few years. Though it can be considerably more expensive than some of the others presented.
se
You're welcome. The initial cost is an issue, but there's all the advantages the Tx's have, and providing you don't toast them, will hold their value well for later resale.
dhaen said:Transformers are best, but....
The best non-transformer, non valve solution:
http://www.analog.com/Analog_Root/productPage/productHome/0,2121,SSM2143,00.html
Well John, the 2142's had better have improves a lot since I last used them, because they sounded dire.
Re: Re: Ssm2142 / Ina134
Perhaps in the pro audio market. With the exception of transformer-based attenuators and MC step-ups, transformers are almost unheard of in high-end home audio.
se
Brett said:You're welcome. The initial cost is an issue, but there's all the advantages the Tx's have, and providing you don't toast them, will hold their value well for later resale.
Perhaps in the pro audio market. With the exception of transformer-based attenuators and MC step-ups, transformers are almost unheard of in high-end home audio.
se
Steve Eddy said:
Perhaps in the pro audio market.
Absolutely, but if you bought some of the Jensens and decided to sell them later, they would sell readily on ebay.
With the exception of transformer-based attenuators and MC step-ups, transformers are almost unheard of in high-end home audio.
That's their misfortune then isn't it?
Brett said:Absolutely, but if you bought some of the Jensens and decided to sell them later, they would sell readily on ebay.
Let's watch:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2571299619&category=4665
That's their misfortune then isn't it?
Hehehe. Naaaaaaah. Hey, if they're happy, I'm no one to argue.
se
The only input transformers that are mentioned in these forums seem to be ones specially designed for music (pro-fi, or hi-fi) use, and are thus fairly expensive.
Has anyone thought of using cheaper alternatives like those made by Tamura or Hammond? The following transformers from Tamura look interesting, but what do you guys think of them? Can anyone suggest a good circuit using one of these transformers for making a bridged amplifier?
On page 3:
http://dkc3.digikey.com/pdf/C041/1160-1165.pdf
Has anyone thought of using cheaper alternatives like those made by Tamura or Hammond? The following transformers from Tamura look interesting, but what do you guys think of them? Can anyone suggest a good circuit using one of these transformers for making a bridged amplifier?
On page 3:
http://dkc3.digikey.com/pdf/C041/1160-1165.pdf
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Mad_K said:yep, a basic difference amp... very informative datasheet also
edit: was supposed to quote dhaen...
just out of curiosity, how is that IC balenced. i agree that it is a difference amplifer, but i don't agree that it has equal input impedances. as i understand it, the idea is to have equal impeances to pick up equal noise then use a difference amplifer to cancel it out.
no one has been able to show me that this circuit is balenced with any input signal. it is balenced without a signal though, so i guess during silence - when noise could be heard - the noise rejection increases.
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