I have been flirting with the idea of transformer balancing the output of my Technics SL-1650. I figure I could use a 1:2 or maybe a 1:4. This would step up the output signal a bit, get rid of the separate ground connection, and keep the noise as low as possible on the way to the preamp. I didn't know if it was as easy as simply connecting a input transformer to the output or if it would require some additional circuitry. Any ideas on this? Is it a good idea?
1) What cartridge have you got: cartridges are inherently balanced sources, though some manufacturers choose to ground (connect to body) one pin, which slightly messes up using them in this way. You an often get around it though.
2) Does your preamplifier have balanced inputs? If NOT, then the entire operation will serve little purpose.
3) just adding a transformer will affect the load seen by the cartridge - unless its carefully chosen & compensated.
2) Does your preamplifier have balanced inputs? If NOT, then the entire operation will serve little purpose.
3) just adding a transformer will affect the load seen by the cartridge - unless its carefully chosen & compensated.
If your cart is MM the transformer will likely add too much capacitance. It only makes sense with MC carts and many of the step-up transformers are capable of balanced outputs (are center-tapped).
analog_sa said:
No, no, this is a common misconception. "Balanced" means balanced impedances to earth - a centre tap is entirely unnecessary and actually a bad idea. What is required is a transformer with balanced stray capacitances and leakage inductances to connect to the cartridge, which is, as pointed out earlier, inherently balanced. Sometimes, a transformer with such balancing is referred to as having a balanced geometry. Anything that upsets the balance of the impedances degrades common-mode rejection.
A transformer only makes sense with moving coil cartridges - the stray capacitances in a transformer would react unfavourably with a moving magnet cartridge. "Electronic" (op-amp techniques) balancing would work with MM but the inevitable 3dB noise degradation makes it questionable.
>>>a centre tap is entirely unnecessary and actually a bad idea.
And THREE CHEERS TO YOU!
You have no idea (or maybe you do!) how many people I have tried to explain that concept to... and they will NOT have it.
And THREE CHEERS TO YOU!
You have no idea (or maybe you do!) how many people I have tried to explain that concept to... and they will NOT have it.
I run a Grado balanced into a true differential amp (FET) configuration. You can probably avoid the 3dB noise degradation with any MM or MI by having the thermal noise of the cartridge dominate. The Grado is 400 Ohms resistive (2.5nV) and a 1nV diff amp is doable. It should be even easier with a MM (stick with FETs to avoid the bipolar current noise). There is a National app note from 1977 on MM noise that shows this. Unfortunately at the time there were no low noise FET amps.
Well to clarify further, the preamp that I'm currently using is a John Broskie Aikido design (his phono pre board) which is going to have a switchable RIAA option and balanced I/O for microphones and I figured hey, why not balance my turntable. I haven't seen it before but i was hoping there wasn't a well known reason for it (to hide my ignorance haha.) I know impedence is different than resistance, but i measured the cartridge out with a VOM in ohms mode and it was a perfect 1k! I know this wouldn't be hard to find on a transformer primary.
The cartridge I have now is the Shure SC35C and it works for most things but is by no means a "reference" product. I do have an interest in purchasing a MC cartridge though. Should I wait until I have the MC cartridge to make this mod? I have a couple of Beyerdynamic TR/BV 351 015 006 1:15 transformers. Would these do well for an MC cartridge?
Also what is a decent lower cost (less than $200) MC cartridge. I know there aren't many but would a MM cartridge in the $200 price range be better than a MC in the same range?
The cartridge I have now is the Shure SC35C and it works for most things but is by no means a "reference" product. I do have an interest in purchasing a MC cartridge though. Should I wait until I have the MC cartridge to make this mod? I have a couple of Beyerdynamic TR/BV 351 015 006 1:15 transformers. Would these do well for an MC cartridge?
Also what is a decent lower cost (less than $200) MC cartridge. I know there aren't many but would a MM cartridge in the $200 price range be better than a MC in the same range?
You need to decide WHY you want it balanced.
The only point of balanced lines is to reject noise picked up BY THE CABLE.
If that is not a problem at present, you will get no advantage - and possibly crate some problems - converting to balanced.
The only point of balanced lines is to reject noise picked up BY THE CABLE.
If that is not a problem at present, you will get no advantage - and possibly crate some problems - converting to balanced.
Steerpike said:
Interestingly, my AN Japan step-up has a center-tapped primary. Maybe no one has explained this futility to Kondo San.
The centre tap is a convenient point to connect the cable screen, but generally it ought not to be connected at both ends.
Its a complex subject, and there are many variations on a theme; different topologies can be applied to different situations, and HAVING a centre tap doesn't mean it ha to be used in all circumstances.
Its a complex subject, and there are many variations on a theme; different topologies can be applied to different situations, and HAVING a centre tap doesn't mean it ha to be used in all circumstances.
At the BBC (when analogue music lines of several miles or more were still being used), we used to tie both ends of the cable's screen to planet Earth. Naturally, that caused a hum loop round the screen, but it was too much to expect the Post Office to comply with any BBC earthing strategy (they had other customers after all). As a consequence, we knew that if we let planet Earth (or a cable screen) touch the centre tap of our balanced circuit, we would be injecting a noise source. In theory, if our cable and transformer system was perfectly balanced, we would be able to reject that noise, but the noise would probably be larger than the signal, so we would need > 100dB of rejection - which implies incredible balance. It was easier simply not to connect the noise source in the first place...
I wired my turntable balanced, so I have twisted pair (plus screen) from the cartridge to the MC transformer. There is no hum.
Steerpike: Oh yes, I do, I weep the same tears of frustration that you do. Do you get similarly annoyed when people start claiming that 600 Ohms is current practice?
I wired my turntable balanced, so I have twisted pair (plus screen) from the cartridge to the MC transformer. There is no hum.
Steerpike: Oh yes, I do, I weep the same tears of frustration that you do. Do you get similarly annoyed when people start claiming that 600 Ohms is current practice?
Steerpike, I understand what you mean about them being naturally balanced. (if naturally is the right word or not, not sure but i hope you know what i mean) What is "messed up" by using the ground going to pin 1 and the output of the cartridge going to pins 2 and 3 and how is this solved?
That is the correct wiring convention.
With a cartridge there is no worry about the centre tap, because the cartridge winding has no accessible centre tap.
The problem with SOME cartridges, is the manufacturer assumes unbalanced operation, and ties the (-) end of one channel winding to the cartridge body. That messes up balanced line drive capability, since any noise picked up by the body is injected only into the (-) line of one channel. If you can cut that link to the cartridge body, it solves the problem.
Also, since you have stereo operation, you'll have TWO "twincore+screen" cables. The ground should be connected on only ONE cable's screen at both ends. The other channel cable, connect the screen at only one end (usuall the amp end). Otherwise you may create a ground loop - where two cable screens are effectively connected in parallel, and can act like a single turn transformer.
Not sure it that fully answers what you were asking?
I need assistance in setting up parameters for my cart/arm/tt. I am new to this hobby and would appreciate your input. Here's what I have:
Denon 103r MC
Tritium Air Bearing Linear Tracking Tonearm
Modified Rega P3 Design
Denon AU-300LC Step Up Transformer
Monolithic Sound PS1 Phono Stage
If the 103r specs says:
Load Impedance 100 ohm min. (40 ohms when using a transformer)
And the step up transformer specs say:
Output Impedance 40ohm: 4k ohm, boosting 10:1
Question is: How should I set my Monolithic Phono Stage?
Variables are the following:
Subsonic Filter: on vs. off
Load Impedance: 47k vs. 10k vs. 1k vs. 100 ohms
Capacitance: 100pf vs. 270pf vs. 370pf
What would you do? And why?
Denon 103r MC
Tritium Air Bearing Linear Tracking Tonearm
Modified Rega P3 Design
Denon AU-300LC Step Up Transformer
Monolithic Sound PS1 Phono Stage
If the 103r specs says:
Load Impedance 100 ohm min. (40 ohms when using a transformer)
And the step up transformer specs say:
Output Impedance 40ohm: 4k ohm, boosting 10:1
Question is: How should I set my Monolithic Phono Stage?
Variables are the following:
Subsonic Filter: on vs. off
Load Impedance: 47k vs. 10k vs. 1k vs. 100 ohms
Capacitance: 100pf vs. 270pf vs. 370pf
What would you do? And why?
ramoneo14 said:
Something here is very wrong. Are you saying you have a $900 Rega turntable, a $400 Denon Cartridge, a $185 step-up transformer, a $400 phono preamp and a $18,000 linear tracking tonearm? It doesn't make sense.
Let's try to keep this thread centered around the root topic shall we? ramoneo14 if you need assistance with your setup, you should search this site or create a new thread if you cannot find what you are looking for.
Steerpike, that is what I was looking for. Basically I was looking at using this turntable with a balanced preamp. Turned out to be easier than I thought! Thanks for your help.
Steerpike, that is what I was looking for. Basically I was looking at using this turntable with a balanced preamp. Turned out to be easier than I thought! Thanks for your help.
Yes indeed. The Rega has been modified though as a multi-layer maple plinth (very heavy) with upgraded Premotec motor and ruby bearing. The only thing that stayed is pretty much the glass platter and the size of the belt.
The Phono Pre is going to a VTL Ultimate Dual Mono Preamp (not enough gain) which is going to VTL 225 Monoblocks. THese now power custom hybrid Quad ESL 63s + 10" Peerless Woofer in a U-frame design (John K. at Musicanddesign.com).
Overall I have a great system and am an active part of an analog club here in Minneapolis. THe club members all think my system is very, very nice.
Please help me with my phono stage settings.
The Phono Pre is going to a VTL Ultimate Dual Mono Preamp (not enough gain) which is going to VTL 225 Monoblocks. THese now power custom hybrid Quad ESL 63s + 10" Peerless Woofer in a U-frame design (John K. at Musicanddesign.com).
Overall I have a great system and am an active part of an analog club here in Minneapolis. THe club members all think my system is very, very nice.
Please help me with my phono stage settings.
ramoneo14 said:
As was suggested, start another thread with your question. Please do not hijack this one.
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