Aharon
Well-known member
Can I use this balanced receiver as input for a tube pre?.Other examples?.
Thanks
Aharon
http://sound.westhost.com/project87.htm
Thanks
Aharon
http://sound.westhost.com/project87.htm
Transformerless balanced input
- Thread starter Aharon
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Eric Best
Well-known member
That is a record minimalizt reply for PRR and one that I understood every word of!!!!
CJ
Well-known member
Don't worry, he will be back with the Full analysis!
PRR's post are like a fine wine. They take skill and a little aging to perfect!
:grin:
PRR's post are like a fine wine. They take skill and a little aging to perfect!
:grin:
> a little aging
What's to perfect? He asked "Can I...?". Yes. He can. It will even work. It won't even suck.
It won't have the very-very-lowest noise on the planet, but he didn't ask about noise, and I've sure used noisier contraptions and got paid for the gigs. Shaving for the last 0.1dB of noise is fun for designers, and essential if you sell to buyers who read Specs as if they were Truth, but often not very important to recording music well.
There's something about a tube. Not sure what that's about. Westhost #87 can make a fine mike preamp all by itself. Seems to me a tube just messes things up: now you probably need an output buffer because a single transformerless tube won't solidly drive modern pro-audio inputs. And in my opinion, you either go all-tube, no short-cuts; or you hang the tube on the effects loop in post-production, not wrestle with it while live musicians are making magic.
But no. There's no mistake in his assumption. He can use it, happily. What more needs to be said but "Yes"?
What's to perfect? He asked "Can I...?". Yes. He can. It will even work. It won't even suck.
It won't have the very-very-lowest noise on the planet, but he didn't ask about noise, and I've sure used noisier contraptions and got paid for the gigs. Shaving for the last 0.1dB of noise is fun for designers, and essential if you sell to buyers who read Specs as if they were Truth, but often not very important to recording music well.
There's something about a tube. Not sure what that's about. Westhost #87 can make a fine mike preamp all by itself. Seems to me a tube just messes things up: now you probably need an output buffer because a single transformerless tube won't solidly drive modern pro-audio inputs. And in my opinion, you either go all-tube, no short-cuts; or you hang the tube on the effects loop in post-production, not wrestle with it while live musicians are making magic.
But no. There's no mistake in his assumption. He can use it, happily. What more needs to be said but "Yes"?
Peter Simonsen
Well-known member
[quote author="Eric Best"]That is a record minimalizt reply for PRR and one that I understood every word of!!!![/quote]
Ditto... :grin:
Kind regards
Peter
Ditto... :grin:
Kind regards
Peter
Aharon
Well-known member
Thanks to all!!.
IIs there a less noisy schem of comparable simplicity I could use?,I just wanted to breadboard a pre but I have only output transformers and thought maybe I could get away with an acceptable substitution (with the knowledge that it's not the same of course).
Thanks again
Aharon
IIs there a less noisy schem of comparable simplicity I could use?,I just wanted to breadboard a pre but I have only output transformers and thought maybe I could get away with an acceptable substitution (with the knowledge that it's not the same of course).
Thanks again
Aharon
SonsOfThunder
Well-known member
I can't believe that PRR took CJ's bait! :thumb:
The only thing funnier would have been a reply with another single word, PRR.
I love tocome here to lurk and learn, but I love to watch the interactions more, I think! Not that i'm laughing AT anyone but more WITH you! This is when I find the funny little lines for my signatures. I hope no one takes it personally! Feel free to take a shot at me if you do!
Peace!
Charlie
The only thing funnier would have been a reply with another single word, PRR.
I love tocome here to lurk and learn, but I love to watch the interactions more, I think! Not that i'm laughing AT anyone but more WITH you! This is when I find the funny little lines for my signatures. I hope no one takes it personally! Feel free to take a shot at me if you do!
Peace!
Charlie
CJ
Well-known member
"What's ol Charlie Peace on about?"
Which movie? (hint:british musical)
Or was it "Bring ol Charlie Peace over here, will ya?"
:roll:
Save up for a UTC LS-series input. Life is short. Splurge!
Which movie? (hint:british musical)
Or was it "Bring ol Charlie Peace over here, will ya?"
:roll:
Save up for a UTC LS-series input. Life is short. Splurge!
SonsOfThunder
Well-known member
[quote author="cjenrick"]"What's ol Charlie Peace on about?"
Which movie? (hint:british musical) Or was it "Bring ol Charlie Peace over here, will ya?"[/quote] you got me on this CJ, but during my search, I found 2 things...#1--Charlie Peace was the name of a bad dude in the UK in the early 1900s...#2 Charles Manson wrote a song called "Don't Do Anything Illegal"...that's irony if ever I've heard it...
HTH!
Charlie
Which movie? (hint:british musical) Or was it "Bring ol Charlie Peace over here, will ya?"[/quote] you got me on this CJ, but during my search, I found 2 things...#1--Charlie Peace was the name of a bad dude in the UK in the early 1900s...#2 Charles Manson wrote a song called "Don't Do Anything Illegal"...that's irony if ever I've heard it...
Yeah, I have to 2nd this!
HTH!
Charlie
Aharon
Well-known member
[quote author="cjenrick"]"What's ol Charlie Peace on about?"
Which movie? (hint:british musical)
Or was it "Bring ol Charlie Peace over here, will ya?"
:roll:
Save up for a UTC LS-series input. Life is short. Splurge![/quote]
Thanks for the advice cjenrick,funny you say that,the two transformers I have are UTCs........if I could get two more for the same price(free!! LOL).I think I'll end up buying 2 Lundahls.
Take care
Aharon
Which movie? (hint:british musical)
Or was it "Bring ol Charlie Peace over here, will ya?"
:roll:
Save up for a UTC LS-series input. Life is short. Splurge![/quote]
Thanks for the advice cjenrick,funny you say that,the two transformers I have are UTCs........if I could get two more for the same price(free!! LOL).I think I'll end up buying 2 Lundahls.
Take care
Aharon
CJ
Well-known member
the movie was A Hard Days Night.
Charlie Peace was Paul's Grandfather, at the police station., a rather "clean" man me thinks!
Oh yeah, voted best musical sound track of all time.
Mac is playing the Neil Young Bridge School concert next month!
Tony Bennet also, which will be a trip. I wonder if they will jam!
cj
"and if they get you on the ground, watch your brisket!"
"there fists like matured hams.."
"he's got sadism stamped all over his bloody English kisser..."
Charlie Peace was Paul's Grandfather, at the police station., a rather "clean" man me thinks!
Oh yeah, voted best musical sound track of all time.
Mac is playing the Neil Young Bridge School concert next month!
Tony Bennet also, which will be a trip. I wonder if they will jam!
cj
"and if they get you on the ground, watch your brisket!"
"there fists like matured hams.."
"he's got sadism stamped all over his bloody English kisser..."
SonsOfThunder
Well-known member
Cool, CJ. I have never been a huge fan of the Beatles, nor the Rutles, more like an admirer. So I have seen parts of that movie, but never all of it, Cool trivia though!
Charlie
Charlie
CJ
Well-known member
Yeah, it's a cool movie.
Patty Harrison is in it I believe.
On the train, and also as the receptionist at that "grotty" fashion bussiness.
I still don't know who played Pauly's grandad, but he stole the show~!
:guinness:
Patty Harrison is in it I believe.
On the train, and also as the receptionist at that "grotty" fashion bussiness.
I still don't know who played Pauly's grandad, but he stole the show~!
:guinness:
A related topic I found in my PM. I think it should be discussed in the open.
>Looking at this section
This balanced Line input plan was widely used in 1970s DBX and several other brands.
This is not good for a Mike input, as Aharon was asking. It has a lot of "dead resistance" between the source and the amplifier. Working with 200Ω mikes, the resistance noise will be much higher than mike noise. But it is a good plan for general line inputs, because the resistance noise is not a problem at line level, and all that resistance tends to make it immune to abuse.
> Could it be replaced with an input transformer?
Possibly. But there is a BIG difference between a transformer and an amplifier. An amplifier can output more power than it inputs. The transformer only passes the power it gets, or takes the power it needs to drive its load.
> how do I determine what the impedence ratio the TX would need to be
The differential input impedance of this plan is 44KΩ. We know the output impedance of the op-amp is super-low, and that it can drive a couple-KΩ load. The differential gain of this plan is 1:1. (However, the single-ended gain, one hot to ground, is also 1:1, so this is not a Floating input or a Center-Tapped input.)
IF the next stage load is 44KΩ or higher, we can just use a 1:1 44KΩ:44KΩ transformer. Or if we know that the source can drive a lower impedance, we could use a lower-Z 1:1 transformer. 10KΩ:10KΩ is a popular bridging input transformer.
In this case, I happen to know the next stage's input impedance is switched 30KΩ or 3KΩ. So we would have to use a 3KΩ:3KΩ transformer, and present a 3KΩ load to the input jack. That's fairly low "bridging input" impedance.
That next stage could be redesigned, or not, depending what it is (and whether you really need the switched gain).
If the real problem is: you need a transformer for extreme ground-rejection or for "color", simple. Put a 10KΩ:10KΩ bridging transformer in front of this amp, at the screw terminals.
> how would I go about measuring the ratio of an unknown transformer?
That's easy. Put a small audio voltage on one winding and measure the other winding.
Determining the impedance is harder, and strictly impossible. Transformers don't really have an exact impedance. You can use them over a range of impedances, with a range of frequency response and loss curves. The short-cut is to assume that the designed impedance is about 20 times the DC resistance. Then mock it up with the actual impedances you hope to use, and check response, loss, and distortion.
>Looking at this section
This balanced Line input plan was widely used in 1970s DBX and several other brands.
This is not good for a Mike input, as Aharon was asking. It has a lot of "dead resistance" between the source and the amplifier. Working with 200Ω mikes, the resistance noise will be much higher than mike noise. But it is a good plan for general line inputs, because the resistance noise is not a problem at line level, and all that resistance tends to make it immune to abuse.
> Could it be replaced with an input transformer?
Possibly. But there is a BIG difference between a transformer and an amplifier. An amplifier can output more power than it inputs. The transformer only passes the power it gets, or takes the power it needs to drive its load.
> how do I determine what the impedence ratio the TX would need to be
The differential input impedance of this plan is 44KΩ. We know the output impedance of the op-amp is super-low, and that it can drive a couple-KΩ load. The differential gain of this plan is 1:1. (However, the single-ended gain, one hot to ground, is also 1:1, so this is not a Floating input or a Center-Tapped input.)
IF the next stage load is 44KΩ or higher, we can just use a 1:1 44KΩ:44KΩ transformer. Or if we know that the source can drive a lower impedance, we could use a lower-Z 1:1 transformer. 10KΩ:10KΩ is a popular bridging input transformer.
In this case, I happen to know the next stage's input impedance is switched 30KΩ or 3KΩ. So we would have to use a 3KΩ:3KΩ transformer, and present a 3KΩ load to the input jack. That's fairly low "bridging input" impedance.
That next stage could be redesigned, or not, depending what it is (and whether you really need the switched gain).
If the real problem is: you need a transformer for extreme ground-rejection or for "color", simple. Put a 10KΩ:10KΩ bridging transformer in front of this amp, at the screw terminals.
> how would I go about measuring the ratio of an unknown transformer?
That's easy. Put a small audio voltage on one winding and measure the other winding.
Determining the impedance is harder, and strictly impossible. Transformers don't really have an exact impedance. You can use them over a range of impedances, with a range of frequency response and loss curves. The short-cut is to assume that the designed impedance is about 20 times the DC resistance. Then mock it up with the actual impedances you hope to use, and check response, loss, and distortion.
Thanks PRR.
Sorry to clutter up your PM box, it's just that sometimes asking on the board tends to result in 10 different responses that dance around the questions without a good clear answer, which confooooses my feeble mind.
Excellent as always!
-E
Sorry to clutter up your PM box, it's just that sometimes asking on the board tends to result in 10 different responses that dance around the questions without a good clear answer, which confooooses my feeble mind.
Excellent as always!
-E
SonsOfThunder
Well-known member
Thanks PRR for sharing in the open. I'd hate to think all that knowledge was being hoarded up somewhere. There were some good basics there, but some advanced knowledge too!
Read that post again if you haven't already!
Peace!
Charlie
Read that post again if you haven't already!
Peace!
Charlie
idylldon
Well-known member
[quote author="cjenrick"]
I still don't know who played Pauly's grandad, but he stole the show~!
:guinness:[/quote]
Wilfrid Brambell.
You know, there aren't many questions I can answer on this forum (still on the steep end of the electronics learning curve), but when it comes to this kind of trivia I can hang.
Cheers,
--
Don
I still don't know who played Pauly's grandad, but he stole the show~!
:guinness:[/quote]
Wilfrid Brambell.
You know, there aren't many questions I can answer on this forum (still on the steep end of the electronics learning curve), but when it comes to this kind of trivia I can hang.
Cheers,
--
Don
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