setting volume on biamp system

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Hi there Ive got two intergrated amps in a biamp formation, amp 1 as the preamp and amp2 as the power amp. Ive set the volume knob on amp1 just below 9 o' clock which is my listening level, (any higher then neighbour problems). Now setting the volume knob on amp 2 is what im really worried about, the boffins at cambridge audio reccomend setting it about 12 o' clock but this doesn't sound right to me, it sounds flat with no bass or power. What sounds better is turning the volume knob right round to 3 o' clock at least or more, but this is where im really worried. Is this going to damage the amp as you wouldn't turn the volume knob right round to 3 o' clock when using a single amp. Can someone help, andrew, jimwall, anyone, many thanks.
 

Andrew Everard

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Well, provided you're going from the preamp output on one amp to a line-in on the other, I can't see what the problem can be, but I do remember suggesting to an earlier poster that this was a rather odd way of doing things, and that it would be better to biamp with an integrated designed for this, and having a matching power amp.

I suspect the problem you have is down to two sets of preamp circuitry and controls in the signal path, but I'm really not sure what to suggest next.

Some amps have a unity gain switch on one input, bypassing the volume control, so that they can be used in conjunction with an AV receiver, and this would be the best setting for this kind of set-up. But unfortunately the 640 doesn't have this.

EDIT: having just re-read your original post, where you talk about using one amp as the pre amp and the other as the power amp, I just have to check - you are using one amp connected to the treble sections of your speakers and the other to the bass, with the speaker terminal jumpers removed, aren't you?
 
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Anonymous

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Hello again andrew
Im useing the preout on amp1 to the cd input on amp2 via an interconnect. Yes amp 1 is connected to treble section of the speakers and amp 2 is connected to the bass part of the speakers with jumper bars removed. Amp2 is running as the power amp. Everything does sound ok as long as i set the volume on amp 2 to around 3 O'clock ,i was just wondering whether this setting was to much and might damage the amp. thank for your time.
 

Andrew Everard

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No it won't damage the amp, but it does seem very high. Might be worth trying the connection into one of the other line inputs on the second amp, for example tape in, as this may have higher sensitivity than the CD one, and may allow you to back off a bit on the level on the second amp.

Beyond that, I'm afraid I'm baffled.
 
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Anonymous

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What advantage does biamping on this amp give you, interested as i have the same amp
Also, what speakers have you partnered with this amp, i'm torn between B&W CM1's and B&W 685's......
 
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Anonymous

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Ok thanks andrew i will try connecting to the tape input on the second amp and see what happens.

Rock man, ive got the mordaunt short avant 902i speakers wich came free with the 640a and 640c combo, apparently biamping this system gives you more clarity, greater control and better dynamics, so it says in the 640a v1 manual.
 
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Anonymous

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[quote user="Dougie 2"]Ok thanks andrew i will try connecting to the tape input on the second amp and see what happens. Rock man, ive got the mordaunt short avant 902i speakers wich came free with the 640a and 640c combo, apparently biamping this system gives you more clarity, greater control and better dynamics, so it says in the 640a v1 manual.[/quote]

Did YOU notice much difference between listening to them biamped and without?
 
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Anonymous

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the b&w cm1's are far too good for your amp.i would not get them unless you are planning to upgrade to an amp costing about the same. Have you heard b&w 686's? they are about same size as cm1's but probably more appropriate for your amp. What about monitor audio RS1's?

As for biamping it makes the whole sound clearer, more detailed and more open.put simply you have two amps doing the normal work of one so they only work half as hard. Thats what i found with mine anyway. I have an arcam p75 power amp which actually matches up well with the cambridge, provided you use the arcam to drive the woofers.
 
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Anonymous

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[quote user="Dougie 2"]Hi there
Ive got two intergrated amps in a biamp formation, amp 1 as the preamp and amp2 as the power amp. Ive set the volume knob on amp1 just below 9 o' clock which is my listening level, (any higher then neighbour problems). Now setting the volume knob on amp 2 is what im really worried about, the boffins at cambridge audio reccomend setting it about 12 o' clock but this doesn't sound right to me, it sounds flat with no bass or power. What sounds better is turning the volume knob right round to 3 o' clock at least or more, but this is where im really worried. Is this going to damage the amp as you wouldn't turn the volume knob right round to 3 o' clock when using a single amp. Can someone help, andrew, jimwall, anyone, many thanks.[/quote]

Two integrated amps in a bi-amped configuration. Well that's unusual.

But if that's the case, my reasoning says, the amp acting as power amp, needs to be set at 0 dB.
 
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Anonymous

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Dougie, sorry I haven't replied - I don't actually have anything to add beyond what the other posters have suggested. I'm surprised too. At the end of the day I guess it just depends what the gain on the pre-amp out of the amp is compared to the the gain on an input. What happens if you split the source and put the same input into each amp and use the volume controls on each - a little inconvenient but you do get a tone control - given the frequency it operates at it's pretty much useless of course.
 
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Anonymous

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[quote user="ranjeetrain"][quote user="Dougie 2"]Hi there
Ive got two intergrated amps in a biamp formation, amp 1 as the preamp and amp2 as the power amp. Ive set the volume knob on amp1 just below 9 o' clock which is my listening level, (any higher then neighbour problems). Now setting the volume knob on amp 2 is what im really worried about, the boffins at cambridge audio reccomend setting it about 12 o' clock but this doesn't sound right to me, it sounds flat with no bass or power. What sounds better is turning the volume knob right round to 3 o' clock at least or more, but this is where im really worried. Is this going to damage the amp as you wouldn't turn the volume knob right round to 3 o' clock when using a single amp. Can someone help, andrew, jimwall, anyone, many thanks.[/quote]

Two integrated amps in a bi-amped configuration. Well that's unusual.

But if that's the case, my reasoning says, the amp acting as power amp, needs to be set at 0 dB.[/quote]

I agree with ranjeetrain - if the other amp is the pre-amp, it'll adjust the pre-amp output volume according to the volume '*** on that amp and so it follows you wouldn't want to attenuate it further with the power amp.

Not sure how you'd find 0dB though - logic would suggest it'd be wound up to max, but you never know. Aah - how about connect amp1 to one speaker and amp2 to the other and match the volume of the power amp speaker to the pre-amp speaker?
 
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Anonymous

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Problem is ... what do you mean by 0dB?

What you want is the point on the dial at which the "sum" of the gains is the same for each amplifier output. The second amplifier has an extra input stage that it's going through and there's no saying the that pre-amp out really the same as to the back of the amp as to the input on the (first amplifiers) power amp stage. You would maybe assume unity buffer stages for both output and input amps, but would you bet the farm on it? Don't know. Put it where it sounds good!
 
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Anonymous

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Quite agree Jimbo - thats why I suggested connecting a speaker to each amp and matching volume of power amp with preamp. Might be a rubbish idea - in which case someone say so before it's too late..!
 
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Anonymous

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Woah now, if your power amplifiers output is affected by the volume knob then you are pre-amplifying it twice I expect. Does your cambridge not have a power amp in connection too?
 

Andrew Everard

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[quote user="Mr_Poletski"]Does your cambridge not have a power amp in connection too?[/quote]

That was my first thought when this whole subject was first mooted some time back. But no, this amp doesn't have a power amp input connection. If it did, it would have made life a lot easier, and its absence was one of the reasons I argued against this set-up quite a while ago.
 
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Anonymous

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[quote user="bloney"]Quite agree Jimbo - thats why I suggested connecting a speaker to each amp and matching volume of power amp with preamp. Might be a rubbish idea - in which case someone say so before it's too late..![/quote]

That's a fantastic idea, as long as the amps are mono bridgeable. Otherwise you lose half the power defeating the whole purpose.
 

Andrew Everard

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[quote user="ranjeetrain"]That's a fantastic idea, as long as the amps are mono bridgeable. Otherwise you lose half the power defeating the whole purpose.[/quote]

The amps don't have to be bridgeable - all you need is a couple of Y-connectors at the CD player end, and then feed one left output to each amp's left input, and one right to each right, using two sets of interconnects. Connect the bass leg of each speaker to the outputs on one amp, and the treble to the outputs on the other, and you're in business. You can even use the two volume controls to give a slight alteration of bass and treble levels - well, or a huge alteration if you so wish!

Just to clarify, you're not delivering more power to the speakers in either of the configurations we're talking about here - the speakers still 'see' the same amount of power, just it comes from two amplifiers.

And bridging is a very different matter from just having a mono switch - where it's available (on some power amps) it involves reconfiguring two channels so that one sucks and the other blows, in very crude terms. You then connect your speakers to the positive outputs of the two channels, which now form one mono channel, typically delivering three times the power of one of the original stereo channels.

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Anonymous

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I reckon I didn't read bloney very well. I see that what I said is slightly different from what bloney suggested. Thanks for the immediate correction.
But like you said, this configuration delivers 'more' and identical' power to the speakers. Personally for me a more satisfying arrangement.
 
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Anonymous

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[quote user="Andrew Everard"]
[quote user="Mr_Poletski"]Does your cambridge not have a power amp in connection too?[/quote]

That was my first thought when this whole subject was first mooted some time back. But no, this amp doesn't have a power amp input connection. If it did, it would have made life a lot easier, and its absence was one of the reasons I argued against this set-up quite a while ago.
[/quote]

Ah... kudos on resisting the 'I told you so' then;)

What I would do, if there is no way to remove the volume knob from the equation, is pre-out to second amp and choose its volume position by bunging a sine wave through it (with no speaers attached) and using an AC multimeter (fiver from maplin) bung the volume up full and adjust the second until you produce the exact same AC voltage. I wouldn't trust your ears because you'll never decide exactly, always fiddling with it which would drive me nuts. I would not use the second amp for the treble either, because giving an extra pre-amp stage you are asking for more interference and such wchi will be crossovered out for the bass

The other option is to take a soldering iron to it and changing the pre-out to a power in, probably just a matter of moving a wire or resistor...

but hang on, that depeds on the circuit and it might just be that the pre-out is connected in parallel to the power amp... Might be worth trying to connect the two preouts together and see what happens;) I know that wouldn't work on my 8000A deu to internal resistors and that may be the case here, you might get things completely gain-unmatched.
 
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Anonymous

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im still none the wiser about what do do,maybe as jimwall said just turn the knob until it sounds best, but this does play on my mind as i dont know if its in the exact right place, does it really matter anyway. this is the way ive been doing it for a while. I do like the thought of what bloney said about one amp for one speaker and then setting the two volume controls the same, i might try this although mr poletski puts me of about the interfierence bit though. Or even andrews way with the y adaptors which i think is similar to what ive done, preout to line in with one interconnect. Maybe turn the volume knob to full,i dont know, there doesn't seem to be a definate answer. One thing i defenately wont be doing though is getting the soldering iron out, id proberbly solder the two amps to the rack.

Thanks to all you fellow enthusiasts who replied.
 
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Anonymous

Guest
I don't know if this is exactly what bloney meant or not but - if you split the signal (you need to do this to get any gain to be honest and using the pre-out of one amp is just one way of achieving it) and put treble left into amp 1 left speaker and bass left into amp 1 right speaker, and bi-amp the left speaker using amp 1, and much the same for the other amp, then you get balance control rather than tone control by using the two volume controls together. Might be a lot easier to settle on the correct settings and much less problematic if you're a bit out.
 
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Anonymous

Guest
[quote user="Andrew Everard"]And bridging is a very different matter from just having a mono switch - where it's available (on some power amps) it involves reconfiguring two channels so that one sucks and the other blows, in very crude terms. You then connect your speakers to the positive outputs of the two channels, which now form one mono channel, typically delivering three times the power of one of the original stereo channels.[/i][/quote]

"sucks and blows" - :)

Okay so I wouldn't have been able to explain it anything like that, I'd have been talking about potential differences and maybe using an analogy of the American domestic power supply system and why that's a good idea compared to ours. Crude terms or not, a fine explanation of the essence.
 

nads

Well-known member
well coming back to this topic and all i can really say again is WHY? Go and put on on E-bay and get a matching power amp as i am sure you would feel happier. each to their own though.
 

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