| h_a |
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 |
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| Steve Eddy |
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 |
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| phn |
| I'm as big a transformer fan as they get. But I would never use transformers is this case. Whatever pros there may be, I can't see them outweight the cons. |
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| Steve Eddy |
| quote: | Originally posted by phn
I'm as big a transformer fan as they get. |
Oh yeah? I bet I'm a bigger transformer fan than you are! So there! :smash:
| quote: | | But I would never use transformers is this case. Whatever pros there may be, I can't see them outweight the cons. |
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 |
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| h_a |
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 |
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| pooge |
| The phono cartridge is not necessarily balanced. While it may start off that way, one side of the coil may be connected to ground in the headshell. |
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| phn |
Lets say you add 50k:50k input transformers on the phono stage and add XLRs.
Still there would be little to gain.
And if you go this distance you can just as well get a step-up transformer insted of the 50k:50k one and a MC cart. |
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| h_a |
@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 |
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| AndrewT |
Hi,
some cartridges have a removable shorting link from one pin to the case/arm. |
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| h_a |
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 |
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| phn |
50k:50k was in reference to MM.
Yes, the Decca carts are great. But fact remains--lower impedance is better. |
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| h_a |
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 |
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| AndrewT |
| are any of the four signal pins connected to the case? |
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| h_a |
As said earlier, yes 1 pin connected to the case.
Cheers, Hannes |
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| Steve Eddy |
| quote: | Originally posted by h_a
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. |
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?
| quote: | | 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!! |
You're welcome.
| quote: | | I just need to add the capacitors (MM needs them) on the primary side, from + to ground and also from - to ground, right? |
I'd put them on the secondary.
| quote: | | Since this would be a 1:1 trafo, the 47k on the secondary side will also appear on the primary - right? |
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 |
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| AndrewT |
Hi,
try disconnecting the cart from the arm, but re-attach the pins to your four cart wires.
Now go to your amp and turn on.
Now listen for snap crackle and pop. (isn't that an advert?) |
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| Steve Eddy |
| quote: | Originally posted by AndrewT
Now listen for snap crackle and pop. (isn't that an advert?) |
Only if you work for Kellogg's. :D
se |
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| sreten |
Hmmm......
Its a lot easier to use fully screened 4-core with an overall screen.
And better ............
:)/sreten. |
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| h_a |
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 |
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| AndrewT |
| two twisted pairs would be better |
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| sreten |
| quote: | Originally posted by h_a
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 thisconnection - 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 |
Hi,
Yes. 4 cores connected to the 4 cartridge pins. Personally I'd use
a single quality 5-pin DIN pug / socket rather than two XLR's.
The overall shielding is used as the earth for the turntable / arm / cartridge case.
The case of the DIN would connect to what for 2 phono sockets
would be the additional earthing post.
4-core with individual full screening.
http://www.maplin.co.uk/module.aspx...eNo=136&doy=5m1
I always use this for a stereo tone arm lead terminating in a DIN plug.
:)/sreten. |
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| AndrewT |
Hi,
the nice attribute to DIN and XLR is the ground making first on insertion and breaking last on extraction.
The very thing that is bad with RCA. |
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| h_a |
Well about the same I want to use, single cable with 4 cores, 2 cores are separately shielded - and I want to use a single 5 pin XLR plug!
@sreten: sorry I don't fully understand...cable shielding is connected to tonearm mass, but NOT to amp, right? Better no double mass connections to avoid ground loops, right?
But the DIN plug case is connected to what then? Just to amp case? Same as the 2 minus signals from the cartridge?
The earthing post usually connects tonearm to amp enclosure, so I somehow don't understand that.
Please let me understand that!
Thanks a lot to all for your help!! Cheers, Hannes
@AndrewT: Neutrik makes some nice RCA plugs, where the mass connects first... |
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| sreten |
Hi,
Seems a five pin XLR will do the job also.
A normal amplifier has an earth post and 2 x phono inputs.
The phono earths should be used for the cartridge current only.
Any other earthing of the turntable should be via the earth post.
I don't understanding the sheilding of the cable described.
:)/sreten. |
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| Steve Eddy |
Why the individual screening? What does that do beside jack up the capacitance?
se |
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| Steve Eddy |
| quote: | Originally posted by h_a
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. |
If you're going to go that route, try an unshielded cable first, using a simple quad braid. A quad braid is essentially two interwoven twisted pairs, with one pair on one plane, and one pair on another plane at 90 degrees to the first. Use each of the two twisted pairs per channel.
Use small gauge wire, 28 or 30 gauge, and something that doesn't have real thick insulation. Stranded would work, but I like solid core. Wirewrap wire or magnet wire is readily available.
For the ground, just use a somewhat heavy gauge wire, 16 or 18 gauge, separate from the braid, and run it straight from the ground on your turntable to the ground post on the phono amp.
You can use a 4 pin XLR if you want, but I think XLRs are much better suited for hooking up 1,000 watt power amps to inefficient speakers than hooking up phono cartridges to phono amps.
I'd use a 4 pin Redel, but mini-DIN would be less expesive and more readily available.
se |
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| EC8010 |
| quote: | Originally posted by Steve Eddy
Use small gauge wire, 28 or 30 gauge, and something that doesn't have real thick insulation. Stranded would work, but I like solid core. Wirewrap wire or magnet wire is readily available.
For the ground, just use a somewhat heavy gauge wire, 16 or 18 gauge, separate from the braid, and run it straight from the ground on your turntable to the ground post on the phono amp. |
Yes, wirewrap wire should work well. The advantage of making the cable yourself is that you can put a tighter twist on each pair. I use twisted pair in a braid screen for each channel, then another braid screen over the top (to hold the two pairs together). I use the braid as my ground wire - it has a nice fat cross-section and low resistance (which is what you want). Another advantage to using wirewrap wire is that the insulation will withstand the heat required to soak the ends of the braid with solder to get a good connection and stop fraying. (I solder another bit of wire to the end of the braid rather than attempting to solder the braid directly to the pin of the DIN plug.)
Very few moving coil cartridges connect one side of the signal to their body. Shures connect to the body, but it's not difficult to cut the thin foil connection, some Ortofons connect but the plastic mount insulate it from the arm. |
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| moamps |
| quote: | Originally posted by AndrewT
... the nice attribute to DIN and XLR is the ground making first on insertion and breaking last on extraction. |
As far as I know, only 3-pin XLR is designed so that the ground pin (i.e. pin1 according to the standard) is connected first.
All, it may not be such a bad idea to consider using a 9-pin D connector (pins1&6 for the first channel and pins 5&9 for the second). D-connectors are not expensive and, IMO, make an excellent choice for a quality, durable connection.
Regards,
Milan |
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| AndrewT |
Hi,
I have just pulled my stock of 5pin female XLR and they consistently have pin1 longer than the rest.
In any case the shell will contact first.
The Dplug/sockets have lots of spare terminals for multiple returns/grounds if they must be kept separate until they reach a central audio ground. |
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| moamps |
| quote: | Originally posted by AndrewT
I have just pulled my stock of 5pin female XLR and they consistently have pin1 longer than the rest. |
You've got me intrigued now.;) I'll have to check this out myself on Monday when I'm back in the lab.
| quote: | | In any case the shell will contact first. |
The shell is not necessarily connected to the audio ground. Sometimes, it is not even made of electrically conductive material (e.g. plastics). Those interested to learn more about XLR interconnections may find the following comments helpful:
http://www.aes.org/standards/b_comm...-aes48-xxxx.cfm
Regards,
Milan |
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| AndrewT |
Hi,
the non conducting shell type of XLR usually have a conducting spring connected to the main shell casing(at the securing screw).
However this spring will probably not connect the ground before the pins make contact due to the spring being shorter than the shell.
Moamps,
can you post the AES draft doc showing the plug/socket standard? |
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| moamps |
| quote: | Originally posted by AndrewT
Moamps,
can you post the AES draft doc showing the plug/socket standard? |
I'm afraid I cannot post any AES standards, due to copyright restrictions. They can be purchased online, though, at: www.aes.org/publications/standards .
However, there is an IEC Standard defining the wiring of XLR connectors: IEC 60 268-12. The EBU recommendation based on that Standard is available here:
http://www.ebu.ch/CMSimages/en/tec_...8_tcm6-4749.pdf
Hope this helps,
Milan |
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| Steve Eddy |
| quote: | Originally posted by EC8010
Yes, wirewrap wire should work well. The advantage of making the cable yourself is that you can put a tighter twist on each pair. I use twisted pair in a braid screen for each channel, then another braid screen over the top (to hold the two pairs together). |
Do you really think that shielding is really necessary? I've had my cables, which are unshielded, used in few analogue systems, both from turntable to phono amp and from MC step-up to phono amp and no one has had any noise problems with them.
Since the main culprit is magnetic field coupling at power line frequencies, and since the permeability of copper is about the same as that for air, I don't see that a braided shield would be of much use for that unless it was made from some high permeability material.
I've found that the best way to protect against magnetic field coupling short of high permeability shielding materials is twisting/braiding and keeping the loop area as small as possible.
Have you tried going unshielded and just using the braid separate from the cable to make the ground connection?
se |
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| Steve Eddy |
| quote: | Originally posted by AndrewT
I have just pulled my stock of 5pin female XLR and they consistently have pin1 longer than the rest. |
I have some 3 pin Deltrons here and the pins are all the same length. However on the female, the sockets for pins 2 and 3 are inset further back from the pin 1 socket.
What's the situation with your females? Er... :D
se |
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| Peter Daniel |
| quote: | Originally posted by moamps
You've got me intrigued now.;) |
I've just checked Cannon 5 pin female XLR and indeed pin 1 is longer. |
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| moamps |
OK, may we agree then that only 3pin and 5pin female XLR connectors have pin1 a bit longer, unlike other DIN and XLR female connectors? :)
Regards,
Milan |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
I've just checked Cannon 5 pin female XLR and indeed pin 1 is longer. |
A female with a pin? What, you got a hermaphrodite there, Peter? :D
se |
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| EC8010 |
| quote: | Originally posted by Steve Eddy
Do you really think that shielding is really necessary?
Have you tried going unshielded and just using the braid separate from the cable to make the ground connection? |
I hadn't really thought deeply about what the braid did (if anything). I figure that there are just so many ways that RF and hum can creep into a system that if it's possible for me to do something that might slow them down, then I'll do it (it's so much harder to fix things after the event). With MC cartridge impedances, we're mostly concerned with EM induction, so a copper braid doesn't do much (don't forget eddy currents, though). With a MM cartridge impedances, ES induction becomes more significant, and although the transformer will reject much of it, why rely on balance when losses through screening can be easily added?
I count rewiring a pick-up arm as one of the most horrible jobs, so when I decided to make up a new cable, it was for keeps. As I recall, it took about two days of effort because of the machining necessary to make a new housing for the base of the arm to grip the cable and allow the arm wires to be connected to it. |
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| Steve Eddy |
| quote: | Originally posted by EC8010
I hadn't really thought deeply about what the braid did (if anything). I figure that there are just so many ways that RF and hum can creep into a system that if it's possible for me to do something that might slow them down, then I'll do it (it's so much harder to fix things after the event). With MC cartridge impedances, we're mostly concerned with EM induction, so a copper braid doesn't do much (don't forget eddy currents, though). |
Yeah, there would be some eddy current losses, but it's dependent on frequency and material thickness and I wouldn't think you'd get much benefit down at power line frequencies.
| quote: | | With a MM cartridge impedances, ES induction becomes more significant, and although the transformer will reject much of it, why rely on balance when losses through screening can be easily added? |
Fair 'nuff.
My ultimate goal is to locate my listening room inside a Faraday cage with the only AC being the music signal. Someday maybe. :D
| quote: | | I count rewiring a pick-up arm as one of the most horrible jobs, so when I decided to make up a new cable, it was for keeps. As I recall, it took about two days of effort because of the machining necessary to make a new housing for the base of the arm to grip the cable and allow the arm wires to be connected to it. |
Ouch! I haven't owned a turntable for about 20 years now. I've been eyeballing them for a while now, but maybe I'll forget about them for a while yet. :D
se |
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| EC8010 |
| quote: | Originally posted by Steve Eddy
Yeah, there would be some eddy current losses, but it's dependent on frequency and material thickness and I wouldn't think you'd get much benefit down at power line frequencies. |
As you say, but the most popular valves for RIAA front-ends are VHF/UHF tuner front-end valves like 5842 etc. And to get low noise, they operate with minimal grid-stopper resistors, so we really don't want a sniff of anything creeping in that might be (badly) demodulated and turn up in the audio band. |
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| Steve Eddy |
| quote: | Originally posted by EC8010
As you say, but the most popular valves for RIAA front-ends are VHF/UHF tuner front-end valves like 5842 etc. And to get low noise, they operate with minimal grid-stopper resistors, so we really don't want a sniff of anything creeping in that might be (badly) demodulated and turn up in the audio band. |
Well that's a simple fix. Don't use the damned things. :smash: :D
se |
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| EC8010 |
| They're the ones with healthy mutual conductance... |
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| Steve Eddy |
| quote: | Originally posted by EC8010
They're the ones with healthy mutual conductance... |
You can use that kind of language here? :D
se |
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| SY |
| Around the children, we euphemize it to "gm." |
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| sreten |
| quote: | Originally posted by Steve Eddy
Why the individual screening? What does that do beside jack up the capacitance?
se |
Hi,
You could also use a quad or 2 twisted pair arrangement with overall screen.
But I presume the individual screens will minimise crosstalk.
:)/sreten. |
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| h_a |
I try to understand what the best cabling would be;
1.) connect cartridge pins to phono sockets, but don't connect phono grounds to case. Instead the grounds of the output connect to the case (alternatively one could use a star ground). I think that's recommended for the pearl.
2.) Tonearm/turntable ground is connected to the cable shielding and connected to the amp via earthing post which is connected to the case (or better to star ground?).
Probably this is an purely academical discussion, but I'm trying to get a completely humm-free phonoamp, so any input to ground-connections and such are highly appreciated!!
Thanks for your help!
Cheers, Hannes
PS: maybe somebody knows that as well: on the pearl pcb it says to connect input ground with onboard power filtering ground by the use of a small cable. However there's nothing written in the pdf about this...is this the prefered solution, or is it more clever to connect input ground and power filtering ground to star ground separately? |
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| EC8010 |
| Use your option (2) with a five pin connector such as a DIN, XLR, or "D" type. |
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| h_a |
Oh sorry I think I wasn't precise enough!
I think of doing both!
Cheers, Hannes |
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