Here's an idea...
Assuming, (I didn't notice any problems), the Aleph Active CCS messes with the way high frequencies sound, couldn't we simply add a low pass filter to the thing so it goes to sleep at some appropriate frequency? Minimally an inductor in series, but someone is bound to be able to add components to make the cutoff steeper etc.
It adds a whole new dimension to the tuning of an Aleph, you can choose the gain and frequency of the CCS.
Stuart
Assuming, (I didn't notice any problems), the Aleph Active CCS messes with the way high frequencies sound, couldn't we simply add a low pass filter to the thing so it goes to sleep at some appropriate frequency? Minimally an inductor in series, but someone is bound to be able to add components to make the cutoff steeper etc.
It adds a whole new dimension to the tuning of an Aleph, you can choose the gain and frequency of the CCS.
Stuart
If I'm understanding your proposal correctly this will make matters worse, not better. The Aleph current source needs to be able to "dance" with its partner's every move, not just the larger steps.
If you feel that the Aleph current source is not up to snuff, you should be looking to increase its speed, not decrease it. For what it's worth, I've never felt the need to redesign the thing, other than stick in a pot so as to be able to fiddle with the current more conveniently.
Grey
If you feel that the Aleph current source is not up to snuff, you should be looking to increase its speed, not decrease it. For what it's worth, I've never felt the need to redesign the thing, other than stick in a pot so as to be able to fiddle with the current more conveniently.
Grey
Well...
...I can't say I've noticed the aleph current source in any negative sense, and 50% gain seems to work very well for me.
I am not planning to fix something that, for me, isn't broken, but others have claimed the results are more to their taste if the AC gain of the current source is lowered or removed altogether.
If by simple filtering one can achieve the benefits of the active CCS in the bass, while retaining the sonic cleanliness of the 'standard' CCS for the upper octaves, it might be useful to some DIYer who hears the difference.
just my 2c
Stuart
...I can't say I've noticed the aleph current source in any negative sense, and 50% gain seems to work very well for me.
I am not planning to fix something that, for me, isn't broken, but others have claimed the results are more to their taste if the AC gain of the current source is lowered or removed altogether.
If by simple filtering one can achieve the benefits of the active CCS in the bass, while retaining the sonic cleanliness of the 'standard' CCS for the upper octaves, it might be useful to some DIYer who hears the difference.
just my 2c
Stuart
Grey- perhaps this is easier said than done? I started thinking my way through the aleph schematic to look for a way to do this. My basic premise was that if voltage fluctuations across the active devices in the current source could be minimized, it would increase the speed and perhaps reduce the problem. But, following the schematic through, the voltages across the current source devices already seem to be minimized--of course, I may have made some mistakes or false assumptions when I was 'thinking it through'. This is where I would normally start probing around with the 'scope to verify what is happening in the circuit, but I don't have anything on the bench that I can use for testing.
I am also not fully convinced that my perceived problem (I want better high frequency detail) is caused by the current source. There are many reasons to believe that the current source is not the problem -- ie, the distortion is lowered with the active current source.
I once read that the Alephs could be described as a back end design, wheras the X amps were a front end design. Perhaps all I need to do is to cascode the differential input to achieve what I am after. So for now, that is where I will start, unless I become enlightened regarding speeding up the current source.
JJ
Okey dokey Chokey!
Sorry, I couldn't resist
I guess that will be it for now. I am working on a crude board for a cascoded LTP. I am not sure what part makes up a 'current mirror' or what it will get me (more gain?). Perhaps it is detailed over there in your schematic on the Aleph-J thread? Either way could you point me to the compenents or maybe post a rough sketch about the current mirror part?
Thanks,
JWJ
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