Hi all!
I'm thinking of using balanced connections from my cartridge (a MM) to the phonostage and converting the signal there to unbalanced (since that is what is used internally).
Is it correct that I gain with balanced wiring +6dB voltage from the cartridge?
That would mean double voltage?!
But how's that possible?
That would mean that the - signal is also used (instead of being connected to ground), ok then I should have +6dB. On the other hand the secondary of the transformer is again grounded and I do get the full voltage - so this should be true also for the cartridge which would mean that there is no double voltage then.
Please help me out of this!
Thanks a lot!!
With kind regards, Hannes
I'm thinking of using balanced connections from my cartridge (a MM) to the phonostage and converting the signal there to unbalanced (since that is what is used internally).
Is it correct that I gain with balanced wiring +6dB voltage from the cartridge?
That would mean double voltage?!
But how's that possible?
That would mean that the - signal is also used (instead of being connected to ground), ok then I should have +6dB. On the other hand the secondary of the transformer is again grounded and I do get the full voltage - so this should be true also for the cartridge which would mean that there is no double voltage then.
Please help me out of this!
Thanks a lot!!
With kind regards, Hannes
There would be no voltage gain, assuming you're using a 1:1 transformer.
The reason people have this notion of balanced somehow inherently meaning a 6dB voltage gain is because often what's done to create a balanced output is to send a single-ended signal to two amplifiers, one non-inverting and one inverting. That will give you 6dB of voltage gain over the single-ended output.
When using a 1:1 transformer to do balanced to unbalanced or unbalanced to balanced conversion, the voltage out is equal to the voltage in. Ideally anyway. There will be some amount of insertion loss with any realworld 1:1 transformer, but that's beside the point.
se
The reason people have this notion of balanced somehow inherently meaning a 6dB voltage gain is because often what's done to create a balanced output is to send a single-ended signal to two amplifiers, one non-inverting and one inverting. That will give you 6dB of voltage gain over the single-ended output.
When using a 1:1 transformer to do balanced to unbalanced or unbalanced to balanced conversion, the voltage out is equal to the voltage in. Ideally anyway. There will be some amount of insertion loss with any realworld 1:1 transformer, but that's beside the point.
se
phn said:
Oh yeah? I bet I'm a bigger transformer fan than you are! So there!
Yeah. The cartridge's output is already balanced so there's no need to use a transformer to balance it, especially if it's just going to feed an unbalanced input at the phono stage.
An input transformer at the phono stage would be helpful for providing a good deal of common-mode noise rejection, but it would make cartridge loading a bit problematic.
se
Guys you got me wrong.
I want to use the balanced output from the cartridge to the phonoamp and convert it then to unbalanced!
That's the point the trafo comes in.
However I do understand now that there's no voltage gain, in contrast to what I was repeatedly told by some manufacturer. Indeed Steve Eddy - thanks!! - explained what the manufacturer seems not to be able to!!
What about cartridge loading?
I just need to add the capacitors (MM needs them) on the primary side, from + to ground and also from - to ground, right?
Since this would be a 1:1 trafo, the 47k on the secondary side will also appear on the primary - right?
Thanks for all your help!!
With kind regards, Hannes
I want to use the balanced output from the cartridge to the phonoamp and convert it then to unbalanced!
That's the point the trafo comes in.
However I do understand now that there's no voltage gain, in contrast to what I was repeatedly told by some manufacturer. Indeed Steve Eddy - thanks!! - explained what the manufacturer seems not to be able to!!
What about cartridge loading?
I just need to add the capacitors (MM needs them) on the primary side, from + to ground and also from - to ground, right?
Since this would be a 1:1 trafo, the 47k on the secondary side will also appear on the primary - right?
Thanks for all your help!!
With kind regards, Hannes
@phn: MC is not generally better, although highend-people believe so.
What do you mean with 50k:50k? Trafo-impedance? I usually see values like 600Ohm for MCs or mics and 10k for line input?
@pooge: yes you're perfectly right! In most cartridges at least 1 channel is balanced, the other - regardless wether it's MM, MC or something else - is usually connected to the cartridge's case.
However even then the balanced solution should work, since the trafo sees double height + & GND instead of + & -??
Or I can isolate the cartridge from the tonearm, so there would be no connection to ground then. Of course the case is then electrically active and no longer grounded...do you think this would cause problems?
Thanks for your replies!! With kind regards, Hannes
What do you mean with 50k:50k? Trafo-impedance? I usually see values like 600Ohm for MCs or mics and 10k for line input?
@pooge: yes you're perfectly right! In most cartridges at least 1 channel is balanced, the other - regardless wether it's MM, MC or something else - is usually connected to the cartridge's case.
However even then the balanced solution should work, since the trafo sees double height + & GND instead of + & -??
Or I can isolate the cartridge from the tonearm, so there would be no connection to ground then. Of course the case is then electrically active and no longer grounded...do you think this would cause problems?
Thanks for your replies!! With kind regards, Hannes
Which ones? Could you name some brands?
I want to use a Shure and a Nagaoka cartridge. At least the Shure has a visible link from one pin to its case but it doesn't look removable. The Nagaoka hints about internal grounding in its operating manual.
Do you think I would run into problems isolating the cartridge from the arm? It would become electronically active and would be no longer grounded.
What do you think?
Cheers, Hannes
I want to use a Shure and a Nagaoka cartridge. At least the Shure has a visible link from one pin to its case but it doesn't look removable. The Nagaoka hints about internal grounding in its operating manual.
Do you think I would run into problems isolating the cartridge from the arm? It would become electronically active and would be no longer grounded.
What do you think?
Cheers, Hannes
Well the Shure V15VxMR has an impedance of 600Ohms and an output of 3.5mV. The well respected Dynavector 17D3 MC has an impedance of 38Ohm and an output of 0.3mV. Further the Shure tracks at 0.75-1.0g, the Dynavector at 1.8-2.0g.
So if you manage to amplify the signal without audible disadvantage by an additional factor of 10, there's still higher record wear.
The reason for the higher tracking force is that the MC needs to be much stronger damped mechanically, so there's information lost right at the stylus.
I would say that they're technically about equal.
However I hope that somebody helps me further with my inital question:
Do you think I would run into problems isolating the cartridge from the tonearm? It would become electronically active and would be no longer grounded, but I would regain a balanced connection.
Cheers, Hannes
So if you manage to amplify the signal without audible disadvantage by an additional factor of 10, there's still higher record wear.
The reason for the higher tracking force is that the MC needs to be much stronger damped mechanically, so there's information lost right at the stylus.
I would say that they're technically about equal.
However I hope that somebody helps me further with my inital question:
Do you think I would run into problems isolating the cartridge from the tonearm? It would become electronically active and would be no longer grounded, but I would regain a balanced connection.
Cheers, Hannes
h_a said:
Ok, but if the input of your phono amp is unbalanced, then the phono amp is already converting it to unblanaced and you don't need a transformer to do that.
So I'm wondering just what your goal is here. Maybe what you really want to do is give your phono amp a balanced input?
You're welcome.
I'd put them on the secondary.
Techincally, yes. What can make cartridge loading problematic is that most good quality input transformers don't want to see such a high impedance on their secondary which can cause some resonance at high frequencies. When such high impedance loads are a necessity, an RC damping network can be used to prevent resonance.
But then, given that the resonance is usually occurring up around 100kHz, then the damping network may not have any appreciable effect on cartridge loading.
se
yes...after lots of worrying I gave up the idea of using such a strange input.
I think I'll add an unbalanced XLR socket to the amp - I like this connection - and use one 4 core cable with full shielding. Has the advantage of just one cable lying around.
That's what you meant, sreten, right? 4 cores with full shield.
With kind regards, Hannes
I think I'll add an unbalanced XLR socket to the amp - I like this connection - and use one 4 core cable with full shielding. Has the advantage of just one cable lying around.
That's what you meant, sreten, right? 4 cores with full shield.
With kind regards, Hannes
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