Time to return to tech-talk.

In a modest-sized room (by horn standards anyway) I want to rig up a
singleton of my modded semi-Fidelio bicor horns for Lowther PM6A. I
thought I'd do the monoing in a specially made 1 metre cable between
the CD player and the power amp.

The QUAD CD expects to see at least 10K impedance on its outputs.
Output of the CD player is 2Vrms and about 0.5Vrms of that is required
to drive the amp to enough power to handle the horns, so high value
resistors can be used in the monomaker if there is any advantage to be
gained.

However, the sound is NOT intended to be reprocessed as stereo
downstream (home installation, not studio); if I want stereo again,
i'll just plug in a stereo cable.

The pot on the integrated amp is probably (the board won't be here
until Tuesday and i can't read the spec on the piccie) 50K Alps but I
can replace it with a DACT of which I have a good selection of values.

So what value resistors would you use for monoing?

How many? Only two, or three?

With your choice of values, what can I expect to lose from the monoing
in bandwidth as distinct from gain?

Andre Jute
Visit Jute on Amps at
http://www.audio-talk.co.uk/fiultra/
"wonderfully well written and reasoned information for the tube audio
constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site containing vital gems of
wisdom"
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On 05/09/2010 21:43, Andre Jute wrote:
Time to return to tech-talk.

In a modest-sized room (by horn standards anyway) I want to rig up a
singleton of my modded semi-Fidelio bicor horns for Lowther PM6A. I
thought I'd do the monoing in a specially made 1 metre cable between
the CD player and the power amp.

The QUAD CD expects to see at least 10K impedance on its outputs.
Output of the CD player is 2Vrms and about 0.5Vrms of that is required
to drive the amp to enough power to handle the horns, so high value
resistors can be used in the monomaker if there is any advantage to be
gained.

However, the sound is NOT intended to be reprocessed as stereo
downstream (home installation, not studio); if I want stereo again,
i'll just plug in a stereo cable.

The pot on the integrated amp is probably (the board won't be here
until Tuesday and i can't read the spec on the piccie) 50K Alps but I
can replace it with a DACT of which I have a good selection of values.

So what value resistors would you use for monoing?

How many? Only two, or three?

Is this a trick question? Surely the real McCoy would know the answer.
Whatever resistors are to hand in the junk box, or a couple of 12k and a
2k2 resistor.
But I would throw in an extra resistor and a capacitor to give some bass
boost.
The values would depend on the in-room LF response of the speakers.

--
Eiron.

Andre Jute wrote:

The QUAD CD expects to see at least 10K impedance on its outputs.

I suspect you are misreading the spec. I expect that is the 'nominal'
load but I'd be VERY surprised if it can't drive a lower impedance.
Without schematics to hand I couldn't give a precise figure.

Graham

Eiron wrote:

Is this a trick question? Surely the real McCoy would know the answer.

That thought crossed my mind too ! :-)

Graham

On Sep 6, 5:08*am, Eeyore
m wrote:
Andre Jute wrote:

The QUAD CD expects to see at least 10K impedance on its outputs.

I suspect you are misreading the spec. I expect that is the 'nominal'
load but I'd be VERY surprised if it can't drive a lower impedance.
Without schematics to hand I couldn't give a precise figure.

Graham

I'm sure the designer left himself some leeway, but the 10K is such a
well-known number, I didn't even bother looking it up. -- Andre Jute

On Sep 6, 5:10*am, Eeyore
m wrote:
Eiron wrote:

Is this a trick question? Surely the real McCoy would know the answer.

That thought crossed my mind too ! *:-)

Graham

I come back after years away, and it is still the same unpleasant
mutual masturbation society with the same inadequates stroking each
other. Dunno why I bother. -- AJ

On 06/09/2010 05:16, Andre Jute wrote:
On Sep 6, 5:10 am, Eeyore
m wrote:
Eiron wrote:

Is this a trick question? Surely the real McCoy would know the answer.

That thought crossed my mind too ! :-)

Graham

I come back after years away, and it is still the same unpleasant
mutual masturbation society with the same inadequates stroking each
other. Dunno why I bother. -- AJ

You got an answer so I don't know what you're complaining about.
Why didn't you pose the dumb question as one of your puppets
as you used to do so you could join the thread later and pretend
you knew the answer all along?

I had a similar problem connecting a DVD player to a stereo amp,
trying to mix the centre channel into L and R as it doesn't have
an option to output plain stereo from a 5.1 source.
Two 10k and a couple of 20k resistors did the job.

--
Eiron.

"Eiron" wrote

I had a similar problem connecting a DVD player to a stereo amp,
trying to mix the centre channel into L and R as it doesn't have
an option to output plain stereo from a 5.1 source.
Two 10k and a couple of 20k resistors did the job.


That's odd. I've never met a DVD player that would not provide a 2-channel
mix-down from a 5.1 source if set up to do so. Indeed many low-cost DVD
players only have 2 audio output sockets, so 2-channel mixed-down audio is
the only option unless you connect the digital output to an external DD/DTS
decoder.

Or was it that you wanted discrete surround channels and it was only the
centre speaker that you didn't have?

David.

In article
,
Andre Jute wrote:

Time to return to tech-talk.

In a modest-sized room (by horn standards anyway) I want to rig up a
singleton of my modded semi-Fidelio bicor horns for Lowther PM6A. I
thought I'd do the monoing in a specially made 1 metre cable between
the CD player and the power amp.

The QUAD CD expects to see at least 10K impedance on its outputs.
Output of the CD player is 2Vrms and about 0.5Vrms of that is required
to drive the amp to enough power to handle the horns, so high value
resistors can be used in the monomaker if there is any advantage to be
gained.

However, the sound is NOT intended to be reprocessed as stereo
downstream (home installation, not studio); if I want stereo again,
i'll just plug in a stereo cable.

The pot on the integrated amp is probably (the board won't be here
until Tuesday and i can't read the spec on the piccie) 50K Alps but I
can replace it with a DACT of which I have a good selection of values.

So what value resistors would you use for monoing?

How many? Only two, or three?

With your choice of values, what can I expect to lose from the monoing
in bandwidth as distinct from gain?

Hi Andre,

I would use two 12k resistors, connecting one to each of the two outputs
of the CD player, with the other ends of the two resistors tied together
to feed mono amp. I would place the resistors at the output end of the
cable to minimize phase shifts at the higher frequencies due to the
effects of cable capacitance, that is use a stereo cable right up to the
input of the mono amp where the mixing network is. The loss with this
arrangement will be minimal, with a mono signal of 2Vrms from each
channel of the CD player, you will see 1.79Vrms across a 50k amplifier
input resistance.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

"Eeyore" m
wrote in message

Andre Jute wrote:

The QUAD CD expects to see at least 10K impedance on its
outputs.

I suspect you are misreading the spec. I expect that is
the 'nominal' load but I'd be VERY surprised if it can't
drive a lower impedance. Without schematics to hand I
couldn't give a precise figure.

For openers, the title "QUAD CD" does not describe a single piece of
equipment, or even a single family of related products. There are at two
families of Quad CD players, the 67 family and the 99 family. The Quad 99
series players further compound the situation by having two different sets
of outputs with very difference performance specs.

I suspect that Jute is basing his alleged specification on the standard IHFM
line level load which includes a 10K resistive component. If that's the case
then he's still in error because the proper way to address that load is with
a device that expects to see 10K or *less*.