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-   -   3/4-stage Aleph 2 (http://www.diyaudio.com/forums/pass-labs/94380-3-4-stage-aleph-2-a.html)

Sony 16th January 2007 02:13 PM

3/4-stage Aleph 2
 
Hello!

Instead of following the main plans on building an Aleph 2, I was wondering if I could make the necessary arrangements to make it a 3-stage or a 4-stage amplifier (instead of 2-stage), wouldn't this result in:

+ Lower distortion.
+ More precision.
+ More low-end control.
- A some how less "natural" sound.

Could I be right? Could this be an interesting way to go?

Thanks and regards

moe29 16th January 2007 02:26 PM

Check out the Aleph 0, may be what you're thinking of.

GRollins 16th January 2007 10:22 PM

This is one of those ideas that has me scratching my head. Yes, it can be done--just make sure that the signal reaching the output stage is roughly 3-4V above the negative rail and that the feedback mechanism is more or less intact so the output biases decently--but why? It kinda negates the whole point. It's like taking a Ferrari to a tractor pull. Can a Ferrari pull weight? Yes, but that's not what a Ferrari is for.
While increasing the NFB might arguably increase low end control, I'm not sure I'd go so far as to say that it increases precision, whatever that might mean. Yes, with enough feedback you can hit any reasonable distortion target, but at what price?
If you're dead set on trying to increase the gain, the easiest way would be to start at the front end, perhaps with larger load resistors (reduce bias current through differential to compensate), or perhaps to use an active load. You could use devices with more gain than the IRF9610. If you're willing to accept lower closed loop gain, you can just increase the NFB on the circuit as-is. That one would be easiest and fastest, assuming that your preamp can make up the difference.

Grey

Sony 17th January 2007 01:42 PM

Grey, thanks for all the great tips.

The Aleph 2 in its original form sounds really good when driving easy loads. On hard loads, it fails - lack of control on the bass spoils the all sonic picture.

I would like to build an amplifier that would make a difficult speaker (large 4-ways floorstanding, with low sensivity, low impedance curve peaks, very demanding woofers) sing exactly as the Aleph 2 when driving an easy load... :cool:

Probably, I should look at a difference topology... :xeye:

GRollins 17th January 2007 02:07 PM

Time to biamp. Use the Aleph for the mids and high frequencies.

Grey

Zen Mod 17th January 2007 02:57 PM

Quote:

Originally posted by Sony
Grey, thanks for all the great tips.

The Aleph 2 in its original form sounds really good when driving easy loads. On hard loads, it fails - lack of control on the bass spoils the all sonic picture.

I would like to build an amplifier that would make a difficult speaker (large 4-ways floorstanding, with low sensivity, low impedance curve peaks, very demanding woofers) sing exactly as the Aleph 2 when driving an easy load... :cool:

Probably, I should look at a difference topology... :xeye:


old mighty Treshold,some of Krells (100?) or Pass X........as Grey sez-for biamping

Sony 17th January 2007 05:08 PM

Indeed, I have one great case of success in bi-amp configuration! :)

Yet, I have used identical amplifiers.
When using different topology amplifiers for bi-amp (like Aleph and X or Aleph and Krell), appart from the need of equalizing the gain of the two amplifiers, won't there be problems on:

- Amplifiers out of phase?
- Amplifier circuits total lenght introduces an audible signal-delay? :confused:

Nelson Pass 17th January 2007 06:29 PM

Neither of those should be problems.

:cool:

GRollins 17th January 2007 09:01 PM

The only significant source of delay is the crossover itself...not the amplifier(s). Note that this is true regardless of whether the crossover is active or passive. Replacing a passive crossover with an active one will not be a problem.
The amount of phase shift will depend largely on the slope you choose, whether 6dB/oct, 12, 18...etc. So if phase shift is of concern to you, you might explore that route. There are also phase shifting circuits you could try if you really want to move things around.

Grey


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