phono vs line inputs on stereo

  • Thread starter Steve-o Stonebraker
  • Start date
S

Steve-o Stonebraker

Guest
My apologies if this isn't the proper sci.electronics group for this
question --

I have an old one-piece stereo, the kind that's designed to look like a
rack system but isn't. It has just one set of RCA inputs, which are
intended for a phonograph. It's my understanding that the phono inputs
expect a much lower-amplitude signal than a regular set of inputs would.
I'd like to use this stereo, though, for my VCR, DVD, Nintendo, etc..
I've done a little searching, and seen a suggestion to go inside and short
out the phono pre-amp, as well as a couple simple circuit designs[1] to
un-amp the line to get it ready for the phono's pre-amp.

Now, I'm a physicist, so I should probably be able to do either of those,
but my only electronics class was way back in 1996, and I didn't enjoy it
very much. If there's a cheap little device I can buy that will fix this
up for me, I'd prefer that. I see that there are separate phono pre-amps
available to allow a phono to go into a line input, but I don't know if
the reverse is possible. Or even if I can just hook up a device like that
backwards and have it work. A non-powered device would be highly
preferred, naturally.

Anybody have a suggestion?

[1]http://www.hut.fi/Misc/Electronics/circuits/phono.html

--Steve-o
--
Steve Stonebraker | http://www.physics.ohio-state.edu/~sstoneb/
sstoneb@yahoo.com | Transformers, astrophysics, comics, games, cartoons.
 
"Steve-o Stonebraker" <sstoneb@campbell.mps.ohio-state.edu> wrote in message
news:slrncck0fk.96u.sstoneb@campbell.mps.ohio-state.edu...
My apologies if this isn't the proper sci.electronics group for this
question --

I have an old one-piece stereo, the kind that's designed to look like a
rack system but isn't. It has just one set of RCA inputs, which are
intended for a phonograph. It's my understanding that the phono inputs
expect a much lower-amplitude signal than a regular set of inputs would.
I'd like to use this stereo, though, for my VCR, DVD, Nintendo, etc..
I've done a little searching, and seen a suggestion to go inside and short
out the phono pre-amp, as well as a couple simple circuit designs[1] to
un-amp the line to get it ready for the phono's pre-amp.

Now, I'm a physicist, so I should probably be able to do either of those,
but my only electronics class was way back in 1996, and I didn't enjoy it
very much. If there's a cheap little device I can buy that will fix this
up for me, I'd prefer that. I see that there are separate phono pre-amps
available to allow a phono to go into a line input, but I don't know if
the reverse is possible. Or even if I can just hook up a device like that
backwards and have it work. A non-powered device would be highly
preferred, naturally.

Anybody have a suggestion?

[1]http://www.hut.fi/Misc/Electronics/circuits/phono.html

--Steve-o
--
Steve Stonebraker | http://www.physics.ohio-state.edu/~sstoneb/
sstoneb@yahoo.com | Transformers, astrophysics, comics, games, cartoons.
Click to expand...
Sounds like two resistors should take care of it (called a voltage divider
or a pad).
 
Charles Schuler wrote:
Sounds like two resistors should take care of it (called a voltage divider
or a pad).
Click to expand...
Because phono inputs are RIAA-equalized, they also need to be bypassed, so
in addition to resistors (and probably coupling/DC blocking capacitors) we
need to bridge around the RIAA EQ.

--
John Miller
Email address: domain, n4vu.com; username, jsm

When the going gets tough, the tough go grab a beer.
 
On 11 Jun 2004 19:03:17 GMT, Steve-o Stonebraker
<sstoneb@campbell.mps.ohio-state.edu> wrote:

My apologies if this isn't the proper sci.electronics group for this
question --

I have an old one-piece stereo, the kind that's designed to look like a
rack system but isn't. It has just one set of RCA inputs, which are
intended for a phonograph. It's my understanding that the phono inputs
expect a much lower-amplitude signal than a regular set of inputs would.
I'd like to use this stereo, though, for my VCR, DVD, Nintendo, etc..
I've done a little searching, and seen a suggestion to go inside and short
out the phono pre-amp, as well as a couple simple circuit designs[1] to
un-amp the line to get it ready for the phono's pre-amp.

Now, I'm a physicist, so I should probably be able to do either of those,
but my only electronics class was way back in 1996, and I didn't enjoy it
very much. If there's a cheap little device I can buy that will fix this
up for me, I'd prefer that. I see that there are separate phono pre-amps
available to allow a phono to go into a line input, but I don't know if
the reverse is possible. Or even if I can just hook up a device like that
backwards and have it work. A non-powered device would be highly
preferred, naturally.

Anybody have a suggestion?

[1]http://www.hut.fi/Misc/Electronics/circuits/phono.html

--Steve-o
Click to expand...
I am not certain about this, but I think that phono inputs generally
have a tailored frequency response, not a flat one as a standard input
would, so your sound might be a little weird even with level
correction...

RIAA equalization rings a bell, try searching Google for more info.

I have found a reverser for RIAA, try this - it seems to be what you
need:

http://sound.westhost.com/project80.htm

Cheers,
Rick.
 
On Fri, 11 Jun 2004 21:30:04 GMT, John Miller <me@privacy.net> wrote:

Charles Schuler wrote:
Sounds like two resistors should take care of it (called a voltage divider
or a pad).

Because phono inputs are RIAA-equalized, they also need to be bypassed, so
in addition to resistors (and probably coupling/DC blocking capacitors) we
need to bridge around the RIAA EQ.
Click to expand...
Is it matched for magnetic or ceramic cartridges? How old is it?

Tom
 
On Fri, 11 Jun 2004 22:35:34 +0100, Captain Rick wrote:
RIAA equalization rings a bell, try searching Google for more info.

http://sound.westhost.com/project80.htm
Click to expand...
Yeah, that bears some similarity to the design I found. I can try to
build something myself, I guess. Maybe I can bug the guys in the
department electronics shop to make a nice little boxed device for me. :)

Thanks for the suggestions, everyone.

--Steve-o
--
Steve Stonebraker | http://www.physics.ohio-state.edu/~sstoneb/
sstoneb@yahoo.com | Transformers, astrophysics, comics, games, cartoons.
 
I am not certain about this, but I think that phono inputs generally
have a tailored frequency response
Click to expand...
Not "gerally": always.

I have found a reverser for RIAA, try this - it seems to be what you
need:
Click to expand...
It will sound _dreadful_, I'm sure.

You're onto a loser with this one. It's really not worth it, IMO.

Noise will be pretty bad, I'm sure.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk
 
Charles Schuler wrote:
"Steve-o Stonebraker" <sstoneb@campbell.mps.ohio-state.edu> wrote in message
news:slrncck0fk.96u.sstoneb@campbell.mps.ohio-state.edu...

My apologies if this isn't the proper sci.electronics group for this
question --

I have an old one-piece stereo, the kind that's designed to look like a
rack system but isn't. It has just one set of RCA inputs, which are
intended for a phonograph. It's my understanding that the phono inputs
expect a much lower-amplitude signal than a regular set of inputs would.
I'd like to use this stereo, though, for my VCR, DVD, Nintendo, etc..
I've done a little searching, and seen a suggestion to go inside and short
out the phono pre-amp, as well as a couple simple circuit designs[1] to
un-amp the line to get it ready for the phono's pre-amp.

Now, I'm a physicist, so I should probably be able to do either of those,
but my only electronics class was way back in 1996, and I didn't enjoy it
very much. If there's a cheap little device I can buy that will fix this
up for me, I'd prefer that. I see that there are separate phono pre-amps
available to allow a phono to go into a line input, but I don't know if
the reverse is possible. Or even if I can just hook up a device like that
backwards and have it work. A non-powered device would be highly
preferred, naturally.

Anybody have a suggestion?

[1]http://www.hut.fi/Misc/Electronics/circuits/phono.html
--Steve-o
Click to expand...


Sounds like two resistors should take care of it (called a voltage divider
or a pad).
Click to expand...
If you look at the URL he gave above, you will see that there needs to
be equalization. If you use just "two resistors", then you will get
terrible sounding audio.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top