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Old 20th March 2008, 09:30 PM   #21
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Default Re: Passive Bi-amping

Quote:
Originally posted by AndrewT
Alternatively,
design 4 monoblocks to drive each of the drivers and their respective half of the crossover independently. =Passive bi-amping.

So if I have two dual mono kits, how do I link each dual mono amp to one another? What size transformer would you recommend, and how many should I install?

Thanks Trip
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Old 20th March 2008, 10:41 PM   #22
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You can build them up as stand alone mono blocks or you can build them up as a stereo pair and share the power transformer. Something like an 8 amp transformer should be plenty for a two amps in one box. Build up a stereo pair and horizontaly bi amp. Just make sure your pre amp can drive the load of two amps in parallel.
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Old 20th March 2008, 11:20 PM   #23
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Quote:
Originally posted by Andy Bartha
You can build them up as stand alone mono blocks or you can build them up as a stereo pair and share the power transformer. Something like an 8 amp transformer should be plenty for a two amps in one box. Build up a stereo pair and horizontaly bi amp. Just make sure your pre amp can drive the load of two amps in parallel.

Thanks.

I don't have a preamp and had intended to control the volume via a Alps RK27 50K POT.

Can you recommend a simple preamp from this site, if required?

Trip
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Old 20th March 2008, 11:32 PM   #24
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What size VA/Secondaries would you recommend if I were to build a stereo pair?

Please bear with me as I am new to electronics but will pick up the basics quite quickly...
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Old 21st March 2008, 12:10 AM   #25
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anything from 20-24v will work fine for A/C secondaries. If you are not going to use a pre amp then you will need to make sure your digital source is up to driving the input impedence load of two chip amps in parallel. Remember most signal source devices are designed to drive a pre amp input load. They are not up to the driving an amp input directly. Amp input needs more drive than most digital sources can provide especially with speakers that aren't the most efficient. With very efficient speakers, something around 95 dB plus, you can cheat abit and trade off efficiency for drive.
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Old 21st March 2008, 12:30 AM   #26
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Tripmaster



Thanks.

I don't have a preamp and had intended to control the volume via a Alps RK27 50K POT.

Can you recommend a simple preamp from this site, if required?

Trip
Oops,
50k pot has an output impedance that varies from zero to 12k5.
This may ruin the performance of any amp that follows a passive attenuator.
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regards Andrew T.
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Old 21st March 2008, 12:34 AM   #27
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Quote:
Originally posted by Andy Bartha
anything from 20-24v will work fine for A/C secondaries. If you are not going to use a pre amp then you will need to make sure your digital source is up to driving the input impedence load of two chip amps in parallel. Remember most signal source devices are designed to drive a pre amp input load. They are not up to the driving an amp input directly. Amp input needs more drive than most digital sources can provide especially with speakers that aren't the most efficient. With very efficient speakers, something around 95 dB plus, you can cheat abit and trade off efficiency for drive.
My CD player is just a Arcam Alpha 7. Can you recommend a simple preamp kit, or should I purchase something second hand from ebay? If I were to purchase something second hand what would you recommend? I know this depends on how much I am willing to spend.
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Old 21st March 2008, 12:36 AM   #28
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Quote:
Originally posted by AndrewT
Oops,
50k pot has an output impedance that varies from zero to 12k5.
This may ruin the performance of any amp that follows a passive attenuator.

What would you recommend?
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Old 21st March 2008, 12:39 AM   #29
AndrewT is offline AndrewT  Scotland
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a pre-amp
or
an active volume control
or
a buffer after the pot
and
maybe a buffer before the pot.
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Old 21st March 2008, 12:55 AM   #30
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Default Preamp not required

50K alps pot is the best choice. KISS = Keep It Simple Stupid. Connections especially grounds must be tight.
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