Feeding separate Stereo and AV preamps into ATC AmpPacks.

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Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Thu Nov 03, 2016 9:37 pm

I would like to find an alternative way of enabling BOTH of the separate systems in my lounge....a stereo SPL preamp, and the 'front' outputs of a Naim AV preamp. to BOTH feed into the same ATC active speakers, without a switching system.
I have found an item called a Combiner, intended for studio use, for example to feed two line level signals into a single mixing desk input, which seems to allow this to happen. It can also be used on stage when a backup amp can be connected in parallel to the main amp in case the first fails, and connected to the same speakers, will allow the proceedings to continue without issue.
However, the combiner is intended to take 2 XLR balanced preamp outputs and combine them to a SINGLE XLR output. Obviously you would have one system turned OFF when the other is ON, BUT this way is apparently SAFE for the preamps, as it isolates each of the 2 XLR inputs from each other.
So I have 2 concerns.
1. Is the sound likely to deteriorate when a Combiner is in use?
2. The Naim output is SINGLE ENDED so I can make up suitable cables but with a 'pseudo balanced' cable two of the pins in the XLR plug are joined together.

Is this all gonna work, or is it a non-starter?

Specs of combiner:

1 galvanically isolated, balanced XLR input (600Ω) with ground lift switch for each channel
1 balanced XLR direct input for each channel
1 balanced XLR output (600Ω) for each channel
Frequency range: 20-20,000Hz
Robust metal housing with very good shielding qualities, suitable for stage applications
Dimensions: 160x55x85mm
Weight: 780g
SOUNDCHECK 07/2007 on the FGA-102, FGA-202, LC-31, MC-31 and LSP-102: "Every musician or sound engineer should have these little helpers in their toolbox. They impress by their inconspiciousness. Both the robust metal housing and the functionality of these transformers allow to solve many problems on stage or in the studio at a reasonable price."


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They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby MattSPL » Thu Nov 03, 2016 11:23 pm

Hi David

I can't answer your question entirely, but I used to use a single ended arcam integrated as a pre amp into a Krell FPB200. I used cardas xlr to rca converters. They worked perfectly and solved a ground loop issue I had previously.

Cheers
Matt
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > DIY Dayton Audio UM18-22 Sub

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby linger63 » Fri Nov 04, 2016 2:56 am

Hi Studioman,

I am in a fairly similar position to you.

I run an Oppo 105 as a transport into a Benchmark DAC2 (DAC/Pre) for stereo............ and use an Integra 80.3 Pre/Pro for M/C.

I simply run separate XLR I/C's to my SCM 70ASL's for BOTH............ and just swap one set of I/C's in/out at the speaker end as required.

Both sets always remain connected at their output ends.

In my case it's CARDAS Clears for Stereo and CARDAS Clear Lights for M/C.

VERY easy and NEVER had any issues......

Considering you can only hear one Source at a time and one is off when listening to the other............there NEVER will be either!!!

Heck.........even if it was ON it wouldn't matter!!


Cheers

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Fri Nov 04, 2016 2:34 pm

Thanks for your reply, Linger63, you clearly have the same situation, and you have decided to solve your problem by changing cables manually.

I want both preamps to connect seamlessly to my SCM150 Active ATCs. The AV preamp will then of course also supply a 3-channel power amp which will feed the 2 rear surround speakers and the centre speaker.

Currently the separate setups I have are:
1. My current Panasonic AV Receiver has integrated power amps feeding a 5.1 speaker setup (4 old but wonderful Philips bookshelf speakers with ribbon tweeters for front and surround, plus a Linn centre speaker, plus a subwoofer.
2. My current stereo setup involves an SPL pre (with balanced outputs) which currently goes to some speakers which I am soon to get rid of. Chinese towers, but not bad actually....

What I am moving towards:
I am going to keep the SPL preamp for stereo duties, and the AV setup I am moving over to is a Naim AV2 and Naim NAP175 3 channel power amp. I am hoping to use a COMBINER to feed both preamp outputs into my ATC SCM150s.

Clearly I will turn OFF whichever setup I am not using, but this should work without me needing to 'switch the ATC input manually' with a switch box or by changing cables.

But I am also looking at some other possibilities. I put the same suggestion on the DIYAudio forum and am getting some alternative replies there, BUT...you guys know ATC, and I would be more confident with an answer on ATCForums!
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby tw99 » Fri Nov 04, 2016 7:13 pm

Can you run a "tape out" from the AV pre-amp into the Stereo pre-amp and just switch inputs on there ? OK, so the AV is going through two pre-amps , but the AV stuff is presumably a bit less critical on quality, even if it were detectable.
NACD3.5 | SBT / DSpeaker anti-mode 2.0 / SIA2-150 / SCM40 + C1

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Fri Nov 04, 2016 8:26 pm

tw99 wrote:Can you run a "tape out" from the AV pre-amp into the Stereo pre-amp and just switch inputs on there ? OK, so the AV is going through two pre-amps , but the AV stuff is presumably a bit less critical on quality, even if it were detectable.


Yes, you are right, I could do that, feeding the FRONT outputs of the Naim into the SPL stereo preamp, but then I would HAVE to have both systems switched on to watch TV / Bluray etc.

I could also do it the other way round, feeding the stereo signal from the SPL preamp through the Naim AV2's 'pass through', but that would limit me to 'unbalanced' operation, as the Naim is all single ended connections.

So this is why I had decided to keep the 2 preamps separate and NOT feed one through the other, but somehow to join the signals or switch them just before the ATC speaker's Amp Pack input point.

The main reason to keep them separate is to retain the simplicity of operation of the AV side for my family to be able to use.

It would of course mean instant death to anyone touching my HiFi. :D
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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby Alexk » Sun Nov 06, 2016 11:42 am

I would strongly steer you away from that IMG box. It's transformer based, and good quality, clean transformers aren't cheap.

Look for a passive switching unit instead, you might be interested in the Kramer VS-4X.

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Sun Nov 06, 2016 3:04 pm

Alexk wrote:I would strongly steer you away from that IMG box. It's transformer based, and good quality, clean transformers aren't cheap.

Look for a passive switching unit instead, you might be interested in the Kramer VS-4X.



Hi Alex.
Thanks for the advice....
I did realise it includes a transformer, BUT there is one DIRECT input, which I thought could be used for the stereo side, and use the transformer input for the AV side. If necessary I could replace the basic transformers with Lundahl ones....
The reason I was keeping clear of the Kramer box is because it is a physical switch....although I STILL might go for it.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby Alexk » Sun Nov 06, 2016 8:27 pm

Remember that the secondary winding will still be in the 'direct' audio path though, and this will have a former made of XY metal which will in turn have issues with magnetic self-inductance.

It's effectively like having a 'static' speaker voice coil in the audio path, even if there's nothing connected to the primary winding (input) of the transformer.

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Mon Nov 07, 2016 9:25 am

Thanks, Alexk, I'll bear that in mind....
And I'll write up the solution (if any) that I find which works!

Cheers, David
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby paul_riordan » Mon Nov 07, 2016 9:56 am

I guess the easiest way with your setup would be to contact SPL and find out the unity position on the volume control and use the pre-out for left and right from the Naim into the SPL pre-amp. I think the only alternative to "do it properly" would be to obtain a pre-amp with an AV by-pass / unity gain input or setting. This is how I have my system setup. I have a Mark Levinson pre-amp which you can set any of the inputs with unity gain. The main reason I bought the ML pre-amp was that it had two sets of balanced inputs and I could set one to unity gain.

Not sure if my contribution helps or not.

Good luck.

Paul
Source: Auralic Aries Mini + Mytek DAC 192
Video source: Oppo BDP-93 blu-ray/SACD/DVD-A
Pre-amp: Mark Levinson ML380s
Cinema Processor: Anthem D2v
Speakers: ATC SCM50ASL (Front and Centre), ATC C4 (Sub), ATC SCM20A-2 (Rear)
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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby MattSPL » Mon Nov 07, 2016 10:56 am

Hi David,

Would something Like this work? https://www.ebay.ie/itm/331496509862
Providing only 1 pre is on at a time, this should work I think.
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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Mon Nov 07, 2016 8:29 pm

Possibly,Matt, but doesn't the plug on the end of the Y see the impedance of both preamps at the same time, even if one is off, AND will it matter that each preamp output will also see the impedance of the other preamp? I really don't know how this would play out...What do you think?
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby studioman » Mon Nov 07, 2016 8:34 pm

paul_riordan wrote:I guess the easiest way with your setup would be to contact SPL and find out the unity position on the volume control and use the pre-out for left and right from the Naim into the SPL pre-amp. I think the only alternative to "do it properly" would be to obtain a pre-amp with an AV by-pass / unity gain input or setting. This is how I have my system setup. I have a Mark Levinson pre-amp which you can set any of the inputs with unity gain. The main reason I bought the ML pre-amp was that it had two sets of balanced inputs and I could set one to unity gain.

Not sure if my contribution helps or not.

Good luck.

Paul



Hi Paul. Any suggestion is helpful because it all adds to the info available. I would need to put the stereo signal from my SPL preamp through the unity gain bypass of my AV preamp.
The problem with using a Unity gain input on my AV preamp is that my Naim AV2 unit is single ended, whereas the SPL output is XLR balanced. They can't (as far as I know) work together.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

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Re: Feeding separate Stereo and AV preamps into ATC AmpPacks.

Postby MattSPL » Mon Nov 07, 2016 8:37 pm

I'm not sure to be honest. I guess that if there is a relay or switch in the path at the pre amp that is off, then the signal will only go this far, meaning the pre that is in use will only see the extra impedance of the cable and possibly a little of the other pre.

I did once run 2 sets of xlr's off my Dac/pre(wired into one xlr at the Dac end) so I could feed the ATC's and a sub with the same balanced signal. This worked just fine.
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > DIY Dayton Audio UM18-22 Sub

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