grip_racer

I will be building a pair of dual-mono class A non-NFB 15w amplifiers - one for full ranges and one for the tweeters.

I was considering an active crossover before the amplifiers, but they are pretty much all driven by op-amps, which I want to avoid. Does anyone have any information on using passive crossovers before bi-amps? I would imagine that without the speaker back-emf/crossover interaction, things would be a lot more predictable. Or does it cause more problems than it's worth?

If it's a bad idea, I'll try and find an active crossover with simple/discrete circuits.

EDIT: Solution found! See post #4

__________________
Audio System:
Cigar Box CS4397 DAC (direct-out) ->
1. Dual-Mono Gainclone Amplifier -> Celestion F15 / Pinnacle AC400 / Advent AS2 / Bose 301 Series II (depending on the day )
2. 100w RMS Plate Amp, C/O @ 80hz -> Elemental Designs 9Kv.2 (vented, 23hz tuning)

BugBash

Im thinking they would rob too much of the signal, or would they create funny loads between the pre and power amps?

Just curious too,
Is there a particular reason for avoiding op-amps?

Some time ago I got myself a diyaudio(.com) Active filter 2(Bob Ellis and Jens design I think)to build, I have a couple Naim power amps to feed!

Not that long afterwards I moved into a Flat which makes running that setup a bit of a no-no as they sound really good at lower volumes but REALLY SING when you crank the volume!

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grip_racer

Yeah, I'm not sure that the impedences would match, that could be bad. It would probably require extra resistors and possibly a transformer to work. Too much, it seems. I'll look for a good active.

As for my arguments against op-amps
1. Op-amps are compromises to keep size and cost down.
2. Discrete circuits allow higher voltage or current with a smaller component count.
3. Most importantly, almost all op-amps use negative feedback to operate. Yes, it boosts power and efficiency, but introduces several types of distortion.

I'll try and find a design that just uses FETs.

__________________
Audio System:
Cigar Box CS4397 DAC (direct-out) ->
1. Dual-Mono Gainclone Amplifier -> Celestion F15 / Pinnacle AC400 / Advent AS2 / Bose 301 Series II (depending on the day )
2. 100w RMS Plate Amp, C/O @ 80hz -> Elemental Designs 9Kv.2 (vented, 23hz tuning)

grip_racer

AH! Nevermind! I just found a diagram on PassDIY!

It works just as I thought, much better than putting the crossovers inbetween the amp and speakers. All that needs to happen is you need to add a resistor. Amplifiers work muuuuch better driving pure resistive loads.

Excellent!

__________________
Audio System:
Cigar Box CS4397 DAC (direct-out) ->
1. Dual-Mono Gainclone Amplifier -> Celestion F15 / Pinnacle AC400 / Advent AS2 / Bose 301 Series II (depending on the day )
2. 100w RMS Plate Amp, C/O @ 80hz -> Elemental Designs 9Kv.2 (vented, 23hz tuning)

jacobthellamer

what is the roll off on those filters going to be like?

grip_racer

You can use any slope/circuit you wish, actually. It doesn't have to be exactly like the one in Nelson Pass' diagram.

__________________
Audio System:
Cigar Box CS4397 DAC (direct-out) ->
1. Dual-Mono Gainclone Amplifier -> Celestion F15 / Pinnacle AC400 / Advent AS2 / Bose 301 Series II (depending on the day )
2. 100w RMS Plate Amp, C/O @ 80hz -> Elemental Designs 9Kv.2 (vented, 23hz tuning)