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Thread: 2 Pre Amps To 1 Power Amp

  1. #1
    Join Date: Jul 2012

    Location: Wimborne

    Posts: 701
    I'm Alex.

    Default 2 Pre Amps To 1 Power Amp

    I'd like to connect a home cinema processor to my stereo system with the one and same power amp used for my main speakers.

    Croft 25R
    Audiolab 8200 AP

    I'm thinking I can use the main L/R pre outs from the Audiolab to one of the line inputs on the Croft and have the volume pots at full (making sure I remember to turn back down before using the Croft for stereo duties!!). The only other option I can think of is to introduce a Switch Box in to the system.

    Any other/better suggestions?

  2. #2
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 1,522
    I'm Gary.

    Default

    If I understand you correctly, then what you propose will work, BUT, you do not need your Croft at full volume.

    Interconnects from Audiolab to an input on Croft, front speakers connected to Croft. Turn volume to zero on Croft

    Switch on.

    Audiolab is now master volume, so you now have all speakers except fronts. Turn Audiolab volume to reasonable listening volume. Turn Croft volume to match and leave there.

    The Audiolab is now in control of all speakers.

    This is my setup, all other devices, cd etc direct to Croft.

    Hope this makes sense


    Quote Originally Posted by alcarmichael View Post
    I'd like to connect a home cinema processor to my stereo system with the one and same power amp used for my main speakers.

    Croft 25R
    Audiolab 8200 AP

    I'm thinking I can use the main L/R pre outs from the Audiolab to one of the line inputs on the Croft and have the volume pots at full (making sure I remember to turn back down before using the Croft for stereo duties!!). The only other option I can think of is to introduce a Switch Box in to the system.

    Any other/better suggestions?

  3. #3
    Join Date: Jul 2012

    Location: Wimborne

    Posts: 701
    I'm Alex.

    Default

    Interesting (and a bonus) that I don't require the Croft to be switched on.

    I thought it might be better to have the Croft volume pots at the same position each time the Audiolab is in use, I suppose it doesn't have to be full volume but at this position it guarantees the volume pots will be exactly the same position every time. The Audiolab will then adjust the volume output to suit.

  4. #4
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 1,522
    I'm Gary.

    Default

    Quote Originally Posted by alcarmichael View Post
    Interesting (and a bonus) that I don't require the Croft to be switched on.

    I thought it might be better to have the Croft volume pots at the same position each time the Audiolab is in use, I suppose it doesn't have to be full volume but at this position it guarantees the volume pots will be exactly the same position every time. The Audiolab will then adjust the volume output to suit.

    The Croft will need to be on otherwise there is no power to the front speakers.

  5. #5
    Join Date: Jul 2012

    Location: Wimborne

    Posts: 701
    I'm Alex.

    Default

    Sorry, I thought the Croft Pre would have to be on, I think I must have misinterpreted your unedited post!

  6. #6
    Join Date: Jul 2012

    Location: Wimborne

    Posts: 701
    I'm Alex.

    Default

    With the volume set as you have it, won't I need to adjust the volume on the Croft whenever I turn the volume up or down on the Audiolab?

  7. #7
    Join Date: Aug 2011

    Location: Coventry, England UK

    Posts: 534
    I'm Simon.

    Default

    Yep, which is why ideally you need to set the Croft at unity gain (full volume I presume like most pre-amps). For me, I use a passive pre but still require volume to be on full for no attenuation. Then just set the trim levels for all speakers in the processor or player (depending on which if you're using for settings). That way whenever you're using the multichannel setup just turn volume to full on the stereo pre and levels will be set and only the processor will alter the volume, along with all other speaker connected. Best way to do it unless your pre has HT bypass.

  8. #8
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 1,522
    I'm Gary.

    Default

    Quote Originally Posted by alcarmichael View Post
    With the volume set as you have it, won't I need to adjust the volume on the Croft whenever I turn the volume up or down on the Audiolab?
    No, the master volume on the Audiolab will control the overall output from all the speakers, it's just another source.

  9. #9
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 1,522
    I'm Gary.

    Default

    This is just not correct, and has the associated issue of forgetting your at full volume as in the OP, when you change sources.

    Not going to argue, try it my way.

    I reiterate connect IC's from Audiolab to Croft line input of choice, speaker cable from Croft to speakers turn on Audiolab and set a reasonable volume, turn Croft on set volume on Croft to zero, increase volume on Croft to match other speakers using the tone output from the Audiolab (or your ears). Now when you increase or decrease volume on Audiolab the Croft volume will follow.....period.

    Assumptions.....you are using a pre-out for front speakers from Audiolab.
    Any line input you choose on Croft


    Quote Originally Posted by Simon_LDT View Post
    Yep, which is why ideally you need to set the Croft at unity gain (full volume I presume like most pre-amps). For me, I use a passive pre but still require volume to be on full for no attenuation. Then just set the trim levels for all speakers in the processor or player (depending on which if you're using for settings). That way whenever you're using the multichannel setup just turn volume to full on the stereo pre and levels will be set and only the processor will alter the volume, along with all other speaker connected. Best way to do it unless your pre has HT bypass.











    Quote Originally Posted by Simon_LDT View Post
    Yep, which is why ideally you need to set the Croft at unity gain (full volume I presume like most pre-amps). For me, I use a passive pre but still require volume to be on full for no attenuation. Then just set the trim levels for all speakers in the processor or player (depending on which if you're using for settings). That way whenever you're using the multichannel setup just turn volume to full on the stereo pre and levels will be set and only the processor will alter the volume, along with all other speaker connected. Best way to do it unless your pre has HT bypass.

  10. #10
    Join Date: Aug 2011

    Location: Coventry, England UK

    Posts: 534
    I'm Simon.

    Default

    Well, technically both ways are correct, it just depends on what the user prefers. For me, I don't want to be faffing with volume matching and prefer to go unity gain and in my turn off procedure I always turn the volume on the pre down to zero and haven't had any problem ever. The best way to do it if not using unity gain is to set the Croft at a set volume (say 12 o clock) and then set all other speakers to that. That way each time you want to use the Croft pre for cinema you set to 12 o clock and it'll click into place.

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