stereo to mono

[Tim R]

I have an older Fisher stereo amp/receiver that would be convenient to drive one Pioneer tower speaker to give louder sound for a tv in the basement rec room.

There are other ways I can do it, it's just that these two pieces are currently unused for anything else and don't require any rearrangement. Eventually this tv will get a home theater setup but not right now.

The amp has no mono switch so I can't just feed off the left channel.

Can I connect the wires from two speaker terminals to one speaker using something like the circuit shown here:

http://www.rane.com/note109.html

It's not clear to me if that circuit shows before the amplifier or after.

If not, is there a better way to do this? Or better just not to do it at all?

thanks,

 

[Jeroni Paul]

Stereo to mono conversion is a dangerous process. There is a caveat: broadcasters often apply stereo wide expansion effects done by inverting one channel which do not add to mono very well. My all purpose safe solution is to take only the left channel and look in the device configuration for options to switch to mono.

I've lived that first hand. One user connected a cheap wireless headphone to a TV set. The headphones had a switch to set Normal (Stereo) mode or TV (Mono) mode, TV mode had to be used to stop a high pitch noise. The user complained that it worked fine most of the time but her favourite program would sound very faint and turning the volume up would result in very distorted sound. I found that switching the headphones to stereo would cure the problem but it resulted in the high pitched noise back. So that was it, that program was broadcast in wide stereo made by inverting one audio channel and the headphones summing of both channels resulted in almost no sound.
As a curiosity, enabling the TV builtin stereo enhacer did invert the situation: the affected program sounded good and any other had a very faint audio.

My solution: I disassembled the base station, unsoldered the right channel and connected the left channel to both inputs. Not a high tech solution but she was very happy with it.

 

The simplest way to do this is to use an RCA Y adapter and connect the single input to both the left and right channels. This is a common practice and will not harm the unit. Any attempt to combine the separate outputs could result in damage to the amp. It was not designed to have that occur.

Pick up a y-cable. Should be less than $5.00

Dan

 

[Rheilly Phoull]

On 02/02/15 9:52 PM, Tim R wrote:

I have an older Fisher stereo amp/receiver that would be convenient to drive one Pioneer tower speaker to give louder sound for a tv in the basement rec room.

There are other ways I can do it, it's just that these two pieces are currently unused for anything else and don't require any rearrangement. Eventually this tv will get a home theater setup but not right now.

The amp has no mono switch so I can't just feed off the left channel.

Can I connect the wires from two speaker terminals to one speaker using something like the circuit shown here:

http://www.rane.com/note109.html

It's not clear to me if that circuit shows before the amplifier or after.

If not, is there a better way to do this? Or better just not to do it at all?

thanks,

The ccts shown are for inputs to the amp, you should be able to just use
one channel if you desire. Depending on the amp it may be possible to
bridge the outputs.

 

[Rheilly Phoull]

On 02/02/15 9:52 PM, Tim R wrote:

I have an older Fisher stereo amp/receiver that would be convenient to drive one Pioneer tower speaker to give louder sound for a tv in the basement rec room.

There are other ways I can do it, it's just that these two pieces are currently unused for anything else and don't require any rearrangement. Eventually this tv will get a home theater setup but not right now.

The amp has no mono switch so I can't just feed off the left channel.

Can I connect the wires from two speaker terminals to one speaker using something like the circuit shown here:

http://www.rane.com/note109.html

It's not clear to me if that circuit shows before the amplifier or after.

If not, is there a better way to do this? Or better just not to do it at all?

thanks,

Very likely that if you feed the speaker from both + outputs (ie. do not
connect the - terminals just each + terminal) you will have the effect
you want.

 

[Tim R]

On Monday, February 2, 2015 at 7:32:54 PM UTC-5, dansabr...@yahoo.com wrote:

The simplest way to do this is to use an RCA Y adapter and connect the single input to both the left and right channels. This is a common practice and will not harm the unit. Any attempt to combine the separate outputs could result in damage to the amp. It was not designed to have that occur.

Pick up a y-cable. Should be less than $5.00

Dan

That's backwards. I don't have a single input, I have two channels output from an amplifier, an amplifier that has no mono switch and will output only stereo, and also it's an amplifier not otherwise in use anywhere else.

I want to put it into a single speaker, because I happen to have a Pioneer tower speaker about 4 foot high for which I have no other use. I don't have a pair of them, I bought something at a yard sale as it was closing for $5, and the guy wouldn't sell it unless I took the speaker too.

The amplifier has output speaker terminals to which I can connect wires. For two channels, four wires.

The speaker has terminals to which I can connect wires. One speaker, two wires.

I had hoped there was some kind of simple resistive network I could put together that would take four wires in and have two wires out.

I found that circuit in the wye article but it really looked like signal level, as someone here confirmed.

There may be no good way to do this and that's okay, it's not like I'm out any money.

Anybody want half of a Pioneer speaker pair?

 

That's backwards. I don't have a single input, I have two channels output from an amplifier, an amplifier that has no mono switch and will output only stereo, and also it's an amplifier not otherwise in use anywhere else.

Sorry, I read that backwards. As it stands, without an external circuit to allow for the use of both channels in "bridge" mode, what you seek is not possible. The amp sections were not designed ot be used in bridge mode (which is what you are asking).

Dan

 

[whit3rd]

On Monday, February 2, 2015 at 2:01:11 PM UTC-8, Rheilly Phoull wrote:

On 02/02/15 9:52 PM, Tim R wrote:
I have an older Fisher stereo amp/receiver that would be convenient to drive one...speaker

Very likely that if you feed the speaker from both + outputs (ie. do not
connect the - terminals just each + terminal) you will have the effect
you want.

It's also very likely that (when/if a monaural source is connected) this will produce
zero output sound.

 

[Tim R]

On Tuesday, February 3, 2015 at 12:22:12 PM UTC-5, Pat wrote:

As others have pointed out, trying to bridge the amplifier at its
output is risky. Fortuneately, you don't need to do that. Just use
one channel of the amplifier driving your single speaker. If you do
that, the only problem you have left is making sure that single
channel (mono) contains both the left and right from the TV. You can
easily bridge the low level signals that go into the amp. Now, what
does the output from the TV look like? If it is RCA connectors
(typically red and white), you can just use a "Y" cable as others have
suggested and your are done.

Ah, you are suggesting bridging the signal level inputs instead of the outputs.

That makes sense to me, but............isn't that what those circuits I linked do? Are you sure a Y-cable will work?

 

> That makes sense to me, but............isn't that what those circuits I linked do? Are you sure a Y-cable will work?

Do it all the time. Works great.

Dan

 

[Pat]

On Tue, 3 Feb 2015 08:56:41 -0800 (PST), Tim R <timothy42b@aol.com>
wrote:

On Monday, February 2, 2015 at 7:32:54 PM UTC-5, dansabr...@yahoo.com wrote:
The simplest way to do this is to use an RCA Y adapter and connect the single input to both the left and right channels. This is a common practice and will not harm the unit. Any attempt to combine the separate outputs could result in damage to the amp. It was not designed to have that occur.

Pick up a y-cable. Should be less than $5.00

Dan

That's backwards. I don't have a single input, I have two channels output from an amplifier, an amplifier that has no mono switch and will output only stereo, and also it's an amplifier not otherwise in use anywhere else.

I want to put it into a single speaker, because I happen to have a Pioneer tower speaker about 4 foot high for which I have no other use. I don't have a pair of them, I bought something at a yard sale as it was closing for $5, and the guy wouldn't sell it unless I took the speaker too.

The amplifier has output speaker terminals to which I can connect wires. For two channels, four wires.

The speaker has terminals to which I can connect wires. One speaker, two wires.

I had hoped there was some kind of simple resistive network I could put together that would take four wires in and have two wires out.

I found that circuit in the wye article but it really looked like signal level, as someone here confirmed.

There may be no good way to do this and that's okay, it's not like I'm out any money.

Anybody want half of a Pioneer speaker pair?

As others have pointed out, trying to bridge the amplifier at its
output is risky. Fortuneately, you don't need to do that. Just use
one channel of the amplifier driving your single speaker. If you do
that, the only problem you have left is making sure that single
channel (mono) contains both the left and right from the TV. You can
easily bridge the low level signals that go into the amp. Now, what
does the output from the TV look like? If it is RCA connectors
(typically red and white), you can just use a "Y" cable as others have
suggested and your are done. If, however, you are trying to tap into
the speaker wires coming from the TV, you will want something like
some of those circuits you mentioned in your first post. You need to
combine the two outputs without shorting the TV amplifier's two
outputs together.

 

[Tim R]

On Wednesday, February 4, 2015 at 6:14:18 AM UTC-5, Pat wrote:

Yes. But, what outputs from the TV are you using to drive those
signal level inputs? If they are regular line level outputs, just
bridge them. Line level outputs are very forgiving. If, however, you
are using external speaker outputs, you will need one of "those
circuits" to avoid problems with the amplifier inside the TV.

Okay, I'm way above my head with this stuff. (Long ago I knew a little more, I had an Extra class amateur radio license.) But this isn't making sense to me.

When we were talking about the amplifier, the consensus was that the bridging circuits shown on the "why not wye" page were only for line level inputs and should not be used on the speaker outputs.

Now that we're talking about the tv, you're saying that the line level outputs don't need bridging but the speaker outputs do.

I'm far more wary about damaging the tv than I am this amp, which cost me only $5 and isn't used often. The tv still works though it is an older tube type, like the 3 spares in the garage I can't get rid of.

 

If the TV has audio output connectors, you are all set using a Y adapter to "connect" both left and right into one channel on the amp. If all you have on the TV is speaker outputs, than you cannot use a Y adapter. The problem will be the same as attempting to connect the amp's speakers together... don't do it.


Dan

 

[Pat]

On Tue, 3 Feb 2015 11:50:29 -0800 (PST), Tim R <timothy42b@aol.com>
wrote:

On Tuesday, February 3, 2015 at 12:22:12 PM UTC-5, Pat wrote:
As others have pointed out, trying to bridge the amplifier at its
output is risky. Fortuneately, you don't need to do that. Just use
one channel of the amplifier driving your single speaker. If you do
that, the only problem you have left is making sure that single
channel (mono) contains both the left and right from the TV. You can
easily bridge the low level signals that go into the amp. Now, what
does the output from the TV look like? If it is RCA connectors
(typically red and white), you can just use a "Y" cable as others have
suggested and your are done.


Ah, you are suggesting bridging the signal level inputs instead of the outputs.

That makes sense to me, but............isn't that what those circuits I linked do? Are you sure a Y-cable will work?

Yes. But, what outputs from the TV are you using to drive those
signal level inputs? If they are regular line level outputs, just
bridge them. Line level outputs are very forgiving. If, however, you
are using external speaker outputs, you will need one of "those
circuits" to avoid problems with the amplifier inside the TV.

 

[Pat]

On Wed, 4 Feb 2015 05:06:40 -0800 (PST), Tim R <timothy42b@aol.com>
wrote:

On Wednesday, February 4, 2015 at 6:14:18 AM UTC-5, Pat wrote:
Yes. But, what outputs from the TV are you using to drive those
signal level inputs? If they are regular line level outputs, just
bridge them. Line level outputs are very forgiving. If, however, you
are using external speaker outputs, you will need one of "those
circuits" to avoid problems with the amplifier inside the TV.

Okay, I'm way above my head with this stuff. (Long ago I knew a little more, I had an Extra class amateur radio license.) But this isn't making sense to me.

When we were talking about the amplifier, the consensus was that the bridging circuits shown on the "why not wye" page were only for line level inputs and should not be used on the speaker outputs.

Now that we're talking about the tv, you're saying that the line level outputs don't need bridging but the speaker outputs do.

I'm far more wary about damaging the tv than I am this amp, which cost me only $5 and isn't used often. The tv still works though it is an older tube type, like the 3 spares in the garage I can't get rid of.

One of the reasons this is confusing is that line level (or signal
level as you called it) is about 1.5 volts max. The voltage going to
small speakers is often a similar voltage. The difference is that
line level drives high impedance inputs so the current is very low and
not much power is transferred. However, with speakers, they often
have a much lower impedance (eg, 8 ohms) and therefore draw more
current and therefore more power. Outputs designed to drive speakers
can therefore be more easily damaged if shorted to ground or each
other. Since the voltages in question are similar, both can be used
to drive the input of your amplifier. We can't be sure how to answer
your question without knowing about the output of the TV. One very
simple circuit you can use if the TV only has speaker outputs is to
simply place some resistors in series with the signal. Almost any
value 1K, 10K, even 100K will do. The result is complete protection
for the amp in the TV because it is designed to drive speakers (8 ohm
or 4 ohm or similarly low values) and now you have thousands of ohms
in series with it. The signal after the resister can no longer drive
speakers but it can still drive the high impedence inputs of your
external amp.

Once again, though, if your TV has line level audio out (usually white
and red RCA connectors), you can just bridge them together and not
worry about any of this.

Good Luck,
Pat

 

[Jeroni Paul]

While the hints and arguments provided in these posts are correct I wonder if anyone did read my previous post which I think is relevant to all this. Mixing the two channels with a Y cord may produce a faint or no sound if wide stereo techniques are applied in the broadcast. I find that using only the left channel is safer.

 

[Phil Allison]

Jeroni Paul wrote:

While the hints and arguments provided in these posts are correct I wonder if anyone did read my previous post which I think is relevant to all this.. Mixing the two channels with a Y cord may produce a faint or no sound if wide stereo techniques are applied in the broadcast.

** FM broadcasters are required to produce a mono compatible signal - or at least they were in the past. Studios use a "stereo modulation monitor" that shows when the signal lacks compatibility by metering the difference signal (L-R) and this must not be greater than either L or R.

True story:

A customer had made a commercial (on 1/4 inch tape) for use on FM radio and it was rejected on the grounds that it was "out of phase". I was asked to check it and found the tape seemed OK.

It took some effort to get through to the "engineer" who had made the judgement and he explained how he used such a meter reach his conclusion.

The recording had a bass guitar, piano and drum kit plus vocal, none of which were out of phase. However, the bass guitar had been panned to the left side, almost completely, which made the difference meter reading unusually high. Hence the mad conclusion the whole tape was "out of phase".

I told the customer to do a re-mix and pan the bass to the centre - problem solved.

The correct way is to pan a bass guitar to the left is to split the signal into low and high frequency bands, at say 150Hz, then pan the highs to the left and the lows to the centre.

This suits most broadcasters and would be essential if cutting an LP to avoid excessive vertical modulation.



.... Phil

 

"Very likely that if you feed the speaker from both + outputs (ie. do not
connect the - terminals just each + terminal) you will have the effect
"you want.

More likely smoke if you connect the +s togther. You can only do that to amps that asre designed for it. Some commercial amps are but I know of no consumer amps that are.

The problem is the amps won't share current well and one will be feeding the other. That is very bad because the outputs are passing current but the voltage across them is not dropping.

You can sum the channels with resistors, like 4 ohm at least. But don't cennoct them directly together.

Think also if it is a DC coupled amp and the offset is off say 250 mV and the DC damping factor is 10 @ 8 ohms load, that thing is likely to idle hot. That is on top of all the L-R material working into the emitter resistors which are probably 0.47 ohm.

Amps that you can parallel have special feedback, actually more accurate, so there is alot less imbalnce, both AC and DC. They also do not allow you to connect to or control the channels separately in that mode. Also, they aere built a hell of alot better than most consumer equipment.

I think most Crowns would be OK doing that, but look at what they cost.

 

>"Pick up a y-cable. Should be less than $5.00 "

Yes, and at that point just use one of the outputs. You could turn the balanc all the way to that side if you feel like it.

Better would be a Y cable witrh built in resistors. I have seen them for sale for this purpose but finding one now ?

The reason for that is summoing them directly can cause distortion when there is a high L-R content. It probsably won't destroy the output amps like an output stage, but alot of equipment is made to have a relatively low output impedance. This keeps the noise down from the cables and who knows what is near them. So if you get the actual adapter, use it at the amp end.

Personally, I can't stansd alot of TV audio. It is overdone, some things even if you turn it up you can't hear what they're saying because the sound Man seems to have a fetish for the sound of falling rain or some shit. Drowns everythng out, anf then a car explodes and it wakes the neighbors up.

Aggravating. Frikken TV which should be compressed has too much dynamic rang while music on FM is compressed to within a dB of its life.

 

>"Anybody want half of a Pioneer speaker pair? "

If it's an HPM-40 I think I had its mate.