Re: 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
AndrewT said:
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
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.
Andy Bartha said:
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
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...
Please bear with me as I am new to electronics but will pick up the basics quite quickly...
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.
Oops,Tripmaster said:
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.
Andy Bartha said:
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.
a pre-amp
or
an active volume control
or
a buffer after the pot
and
maybe a buffer before the pot.
or
an active volume control
or
a buffer after the pot
and
maybe a buffer before the pot.
Preamp not required
50K alps pot is the best choice. KISS = Keep It Simple Stupid. Connections especially grounds must be tight.
50K alps pot is the best choice. KISS = Keep It Simple Stupid. Connections especially grounds must be tight.
Tranny Voltage too low.
Little Higher than 24V. Go for 50V or more, no higher than 84V. That's your problem. Check the datasheet. You almost have it. Get a Tranny from a dead old amp if you can. Keep the power supply seperate from the amp itself, then you can replace it later if you need to. Use the best 1000 uF caps in the amp itself so you don't have to replace them. The power supply can be very simple. Don't listen to these "snubberised" perfectionists. All you need is a Bridge rectifier for the power supply. Sorry if this is a little short.
Little Higher than 24V. Go for 50V or more, no higher than 84V. That's your problem. Check the datasheet. You almost have it. Get a Tranny from a dead old amp if you can. Keep the power supply seperate from the amp itself, then you can replace it later if you need to. Use the best 1000 uF caps in the amp itself so you don't have to replace them. The power supply can be very simple. Don't listen to these "snubberised" perfectionists. All you need is a Bridge rectifier for the power supply. Sorry if this is a little short.
I thought it was 25 k when the pot is in the middle.Hi Peranders,
when pot is just above middle of the resistance range, i.e. -6db, the resistance seen by the receiver is the lower leg of ~25k05 in parallel with the upper leg of ~24k95 in series with the source resistance of ~100r. The actual
The two routes to ground are effectively 25k05//25k05 giving a source impedance of 12k525 for Rs=100r. Any other position of the volume pot will present a lower impedance to the receiver.
Output impedance=[Rpot+Rs]/4
when pot is just above middle of the resistance range, i.e. -6db, the resistance seen by the receiver is the lower leg of ~25k05 in parallel with the upper leg of ~24k95 in series with the source resistance of ~100r. The actual
The two routes to ground are effectively 25k05//25k05 giving a source impedance of 12k525 for Rs=100r. Any other position of the volume pot will present a lower impedance to the receiver.
Output impedance=[Rpot+Rs]/4
of course, you are right.- Status
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