Hi;

I am in the process of building an MC step up transformer. I am
somewhat confused about the wiring though. I have been reading that to
prevent ground loops, the input and output jacks(ground connections)
should be isolated from the metal chassis. That seems fair. But what
has me confused is that the chassis nearly always has a binding post
for grounding.

I have noticed that some transformers have a shield wire and
manufacturers recommend connecting it to the binding post(ground) but
this seems to defeat the chassis/box as a shielding enclosure.

But what about transformers without this available shield wire? Having
a ground connection which connects to a metal box that is not
connected to the internal components seems to not accomplish anything.
Am I missing something here?

Thanks

Crumb wrote:

Hi;

I am in the process of building an MC step up transformer. I am
somewhat confused about the wiring though. I have been reading that to
prevent ground loops, the input and output jacks(ground connections)
should be isolated from the metal chassis. That seems fair. But what
has me confused is that the chassis nearly always has a binding post
for grounding.

I have noticed that some transformers have a shield wire and
manufacturers recommend connecting it to the binding post(ground) but
this seems to defeat the chassis/box as a shielding enclosure.

But what about transformers without this available shield wire? Having
a ground connection which connects to a metal box that is not
connected to the internal components seems to not accomplish anything.
Am I missing something here?

Thanks

The idea of the step up tranny is to raise the 0.3 mV output of the MC to
say 3 mV,
and to isolate the cart circuit from the amp input completely, so that
there is no shared
earth wiring which all too often causes hum.
The chassis of the TT is sometimes connected to the external braid
shielding of the
wires going to the cart, if indeed that is what the TT has inside its arm.

My old Thorens had this set up. I removed the TT internal wire from the
chassis and arm
to be able to ground all that separately to the chassis of the preamp.
The shielded wire from each half of the cart and their internal live wire
are
soldered to larger sheilded wires and taken to the preamp RCA sockets.

In your case, the chassis and arm could still be taken via a separate wire
to the
preamp chassis.
The case of the MC step up tranny also can be taken to the preamp chassis

The cart wires can be a twisted pair down the arm, or a fine shielded
coax, not critical,
and then the two wires or shield and wire connected to a twisted pair
coaxially inside a shield
to the step up tranny. The sheild is connected to the case of the tranny.
The addition of a shield on the tranny is OK, ie, a layer of very thin
copper sheet,
but not allowed to be a shorted turn .
This also is connected to the tranny case.

Let's assume the amp is a single ended input type, ie, unbalanced.
The output wires to the amp would via a conventional shielded coax cable,
with one end of the sec
connected to the shield at 0V, and the live end via the internal wire.
This shield is kept separate from any direct connection to the preamp
chassis.
The preamp should have a 0V star point connection located near the phono
input
RCA sockets.

The preamp chassis should be connected to the star point via say a 5 watt
22 ohm
bypassed with 0.1 uF. The earth wire from the mains should be directly
connected to the chassis.

This way the earthing of the chassis provides safety, and the casing of
the
MC step up tranny and the chassis of the TT are all directly connected to
earth safely.
But there is no way earth currents containing induced hum can circulate in
sensitive circuits
causing noise.

I have my Denon with 0.3 mV output directly connected to the preamp.

There is considerable hum when the TT chassis is not grounded via
a separate cable to the preamp chassis.
But when grounded, and when the amp gain is turned up to max,
there is no discernable hum, even with an ear close to a speaker.

Patrick Turner.

Crumb wrote:

Hi;

I am in the process of building an MC step up transformer. I am
somewhat confused about the wiring though. I have been reading that to
prevent ground loops, the input and output jacks(ground connections)
should be isolated from the metal chassis. That seems fair. But what
has me confused is that the chassis nearly always has a binding post
for grounding.

I have noticed that some transformers have a shield wire and
manufacturers recommend connecting it to the binding post(ground) but
this seems to defeat the chassis/box as a shielding enclosure.

But what about transformers without this available shield wire? Having
a ground connection which connects to a metal box that is not
connected to the internal components seems to not accomplish anything.
Am I missing something here?

Thanks

The idea of the step up tranny is to raise the 0.3 mV output of the MC to
say 3 mV,
and to isolate the cart circuit from the amp input completely, so that
there is no shared
earth wiring which all too often causes hum.
The chassis of the TT is sometimes connected to the external braid
shielding of the
wires going to the cart, if indeed that is what the TT has inside its arm.

My old Thorens had this set up. I removed the TT internal wire from the
chassis and arm
to be able to ground all that separately to the chassis of the preamp.
The shielded wire from each half of the cart and their internal live wire
are
soldered to larger sheilded wires and taken to the preamp RCA sockets.

In your case, the chassis and arm could still be taken via a separate wire
to the
preamp chassis.
The case of the MC step up tranny also can be taken to the preamp chassis

The cart wires can be a twisted pair down the arm, or a fine shielded
coax, not critical,
and then the two wires or shield and wire connected to a twisted pair
coaxially inside a shield
to the step up tranny. The sheild is connected to the case of the tranny.
The addition of a shield on the tranny is OK, ie, a layer of very thin
copper sheet,
but not allowed to be a shorted turn .
This also is connected to the tranny case.

Let's assume the amp is a single ended input type, ie, unbalanced.
The output wires to the amp would via a conventional shielded coax cable,
with one end of the sec
connected to the shield at 0V, and the live end via the internal wire.
This shield is kept separate from any direct connection to the preamp
chassis.
The preamp should have a 0V star point connection located near the phono
input
RCA sockets.

The preamp chassis should be connected to the star point via say a 5 watt
22 ohm
bypassed with 0.1 uF. The earth wire from the mains should be directly
connected to the chassis.

This way the earthing of the chassis provides safety, and the casing of
the
MC step up tranny and the chassis of the TT are all directly connected to
earth safely.
But there is no way earth currents containing induced hum can circulate in
sensitive circuits
causing noise.

I have my Denon with 0.3 mV output directly connected to the preamp.

There is considerable hum when the TT chassis is not grounded via
a separate cable to the preamp chassis.
But when grounded, and when the amp gain is turned up to max,
there is no discernable hum, even with an ear close to a speaker.

Patrick Turner.

In article writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Mike Rivers wrote:
In article
writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?

Moving Coil (phono cartridge) step up transformer to match MC cartridges to
standard magnetic phono cartridge inputs.

Mike Rivers wrote:
In article
writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?

Moving Coil (phono cartridge) step up transformer to match MC cartridges to
standard magnetic phono cartridge inputs.

"Arny Krueger" wrote in
:

Mike Rivers wrote:
In article
writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?

Moving Coil (phono cartridge) step up transformer to match MC
cartridges to standard magnetic phono cartridge inputs.

Or the process of changing an ordinary human being into a noisy, obnoxious
game show host.

"Arny Krueger" wrote in
:

Mike Rivers wrote:
In article
writes:

I am in the process of building an MC step up transformer.

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?

Moving Coil (phono cartridge) step up transformer to match MC
cartridges to standard magnetic phono cartridge inputs.

Or the process of changing an ordinary human being into a noisy, obnoxious
game show host.

In article znr1086137958k@trad (That's me!) writes:

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?


Oh - Moving Coil. Turntable. Cartridge. I get it now.

Buy the real thing and hook it up according to the instructions.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article znr1086137958k@trad (That's me!) writes:

I guess I'm showing my ignorance for real this time, or my lack of
cleverness. What's an MC step up transformer?


Oh - Moving Coil. Turntable. Cartridge. I get it now.

Buy the real thing and hook it up according to the instructions.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

On 1 Jun 2004 16:04:14 -0700, (Crumb) wrote:

questions clipped for bandwidth

The rule is to have one and only one ground connection between
any two points.

Your 800 pound gorilla will be magnetic shielding though.

Good fortune,

Chris Hornbeck

On 1 Jun 2004 16:04:14 -0700, (Crumb) wrote:

questions clipped for bandwidth

The rule is to have one and only one ground connection between
any two points.

Your 800 pound gorilla will be magnetic shielding though.

Good fortune,

Chris Hornbeck