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MaxPlumage

Preamp Crossovers

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Just a general question - why do almost all 2ch preamps never have crossover settings on them? 

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Because they're usually designed with 2 channel full range power amps out? What kind of crossovers did you have in mind?

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8 minutes ago, MaxPlumage said:

Just a general question - why do almost all 2ch preamps never have crossover settings on them? 

Likely, because only a very small percentage of customers are seen as having frequency divided separate high pass and low pass power amps. Rather the conventional passive crossover in speakers tends to dominate the marketplace.   

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Posted (edited)

Okay let me explain - I am trying to approach it from the point of subwoofer integration for both HT and 2ch. If I have HT bypass set up for my preamp, then when I switch from the AVR to preamp, I lose my subs connected to the AVR. To offset this, I can have the AVR connected to the LFE and one set of analog outputs from the preamp  to the line level connection of the sub (one for left sub, one for right sub). The preamp would also directly be connected via XLR to my power amp. This way, when I am in 2ch mode, the AVR does not come on. It's a pure 2ch chain. When in HT mode, it works as usual.

 

The problem is the xover. In 2ch mode I have to adjust the dial in the sub. But will need to reset it for HT mode.

 

This manual process of adjusting the xover would be eliminated if my preamp had a xover setting dial, similar to my avr.

 

It would have been great if the subwoofer's xover dial settings only applied to line in (but unfortunately it also applies to LFE in.

 

Some stereo integrated amps do have it, but most 2ch preamps do not. 

 

AV preamps do, but not 2ch preamps.

 

 

 

Edited by MaxPlumage

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Posted (edited)
1 hour ago, MaxPlumage said:

Okay let me explain - I am trying to approach it from the point of subwoofer integration for both HT and 2ch. If I have HT bypass set up for my preamp, then when I switch from the AVR to preamp, I lose my subs connected to the AVR. To offset this, I can have the AVR connected to the LFE and one set of analog outputs from the preamp  to the line level connection of the sub (one for left sub, one for right sub). The preamp would also directly be connected via XLR to my power amp. This way, when I am in 2ch mode, the AVR does not come on. It's a pure 2ch chain. When in HT mode, it works as usual.

 

The problem is the xover. In 2ch mode I have to adjust the dial in the sub. But will need to reset it for HT mode.

 

This manual process of adjusting the xover would be eliminated if my preamp had a xover setting dial, similar to my avr.

 

It would have been great if the subwoofer's xover dial settings only applied to line in (but unfortunately it also applies to LFE in.

 

Some stereo integrated amps do have it, but most 2ch preamps do not. 

 

AV preamps do, but not 2ch preamps.

 

 

 

Suggest you download the schematic ( HiFi engine being a excellent location for schematics and owner manuals )  for your preamp and set about modifying it to your requirements. It suggests the simple addition of a relay could overcome the needs you have to switch the subs in. 

 

At a basic level you would locate the input switch ,and observe just exactly what it was switching. Relays have what is termed Normally Off contacts and Normally ON contacts, you would provide from a DC supply approx 12v via a diode and add a diode reversed biased across the relay coil. When the voltage/ current is supplied to the coil the relay contacts then close, and you would arrange  your subs to be switched in from the relay contacts observing if they are L and R and using suitable number of contacts to switch to the output.  Noting too that the Normally Off contacts can provide sometimes the needed answer, if a suitable coil voltage and current is present when the input you require is at that moment switched out.  

 

Alternatively you may find there could be  spare contacts and poles on the existing switch, but a relay suggests as being a better answer. generally it is difficult to invent a contact position, that was not there in the first place.  So studying the schematic or indeed posing the same question to its manufacturer, might yield the needed plan of approach.  

Edited by stereo coffee

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Posted (edited)
38 minutes ago, stereo coffee said:

Suggest you download the schematic ( HiFi engine being a excellent location for schematics and owner manuals )  for your preamp and set about modifying it to your requirements. It suggests the simple addition of a relay could overcome the needs you have to switch the subs in. 

 

At a basic level you would locate the input switch ,and observe just exactly what it was switching. Relays have what is termed Normally Off contacts and Normally ON contacts, you would provide from a DC supply approx 12v via a diode and add a diode reversed biased across the relay coil. When the voltage/ current is supplied to the coil the relay contacts then close, and you would arrange  your subs to be switched in from the relay contacts observing if they are L and R and using suitable number of contacts to switch to the output.  Noting too that the Normally Off contacts can provide sometimes the needed answer, if a suitable coil voltage and current is present when the input you require is at that moment switched out.  

 

Alternatively you may find there could be  spare contacts and poles on the existing switch, but a relay suggests as being a better answer. generally it is difficult to invent a contact position, that was not there in the first place.  So studying the schematic or indeed posing the same question to its manufacturer, might yield the needed plan of approach.  

Thanks for the input. I however do not understand how relay modification for switching the subs would help with independent xover settings which is what my problem is. With the connection set up as in my previous post there is no need to switch the sub.

 

I am also not a big fan of modding gear I just bought on many levels, warranty issues being one of them.

 

Apologies if I don't fully understand your post.

Edited by MaxPlumage

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4 hours ago, MaxPlumage said:

Just a general question - why do almost all 2ch preamps never have crossover settings on them? 

Because almost nobody is hooking up to a system which needs a crossover.

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4 hours ago, MaxPlumage said:

It would have been great if the subwoofer's xover dial settings only applied to line in (but unfortunately it also applies to LFE in.

There are some subwoofers which work like this.

 

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