aleph 3 ps
This may be a no brainer to some, but I had a small amount of audible hum in 90dB speakers in my Aleph 3. I was concerned it was the grounding situation as I used two transformers and thus completely separate ps's in the same chassis. Anyways.... using a grounding scheme as prescribed in the Zen pt. 4 article cleaned up almost all of the remaining hum.
My only other concern is that there is about 70mV of DC incoming from the wall. Is this enough to warrant a DC filter. I know its been beat to death on the fact that it only takes a little DC to screw with a toroid, but I wasn't sure what magnitudes are worrisome.
Thanks,
Brent
This may be a no brainer to some, but I had a small amount of audible hum in 90dB speakers in my Aleph 3. I was concerned it was the grounding situation as I used two transformers and thus completely separate ps's in the same chassis. Anyways.... using a grounding scheme as prescribed in the Zen pt. 4 article cleaned up almost all of the remaining hum.
My only other concern is that there is about 70mV of DC incoming from the wall. Is this enough to warrant a DC filter. I know its been beat to death on the fact that it only takes a little DC to screw with a toroid, but I wasn't sure what magnitudes are worrisome.
Thanks,
Brent
I have a question regarding the bias and AC current setting:
I am planning to build power amps for our living room Stereo equipment. Since I don’t have listening rooms etc. and my wife would not like several amps in the same equipment, I am forced to hear everything through this power amp: TV, Radio, my childrens fairy-tales from compact cassete, and, sometimes, good music from LP or CD 😎 .
As you might imagine, the Amp would be running quite for a long time each day. Looking at Aleph and Aleph-X, for better sound, the bias should be cranked up, thats what I learned.
Now my idea- Why not having two operating modes: LowFi, with low bias and high AC Current gain (btw I have 4 Ohm Speakers) and High Fi with high bias and low (<65%) current gain. So i will save some energy. This could be done with a switch.......What do you think about?
Regards
Tino
I am planning to build power amps for our living room Stereo equipment. Since I don’t have listening rooms etc. and my wife would not like several amps in the same equipment, I am forced to hear everything through this power amp: TV, Radio, my childrens fairy-tales from compact cassete, and, sometimes, good music from LP or CD 😎 .
As you might imagine, the Amp would be running quite for a long time each day. Looking at Aleph and Aleph-X, for better sound, the bias should be cranked up, thats what I learned.
Now my idea- Why not having two operating modes: LowFi, with low bias and high AC Current gain (btw I have 4 Ohm Speakers) and High Fi with high bias and low (<65%) current gain. So i will save some energy. This could be done with a switch.......What do you think about?
Regards
Tino
Look at this thread for a good discussion:
http://www.diyaudio.com/forums/showthread.php?s=&postid=225133&highlight=#post225133
Hi Tino,
yes that can be done. You´ll need two switches per channel for an Aleph and 4 per channel for an X (of course you can use one switch an 2 or 4 relais).
Just set the low fi bias with R19/21 remember the values and then set the normal bias. You can now use two pairs of R19/21 for alternative settings.
I´m not shure if you can alter the setting when the amp is playing, if not you´ll have to turn it of before changing the settings.
William
yes that can be done. You´ll need two switches per channel for an Aleph and 4 per channel for an X (of course you can use one switch an 2 or 4 relais).
Just set the low fi bias with R19/21 remember the values and then set the normal bias. You can now use two pairs of R19/21 for alternative settings.
I´m not shure if you can alter the setting when the amp is playing, if not you´ll have to turn it of before changing the settings.
William
I think the CRCRC power filter is an extremely good idea in the Aleph-X, but I don't know if I would use it in an Aleph 5. In the X the current changes are equal and opposite on the two bridged sides of the amp; the filter sees no AC current at all. But in the Aleph the filter does supply AC current. I fear the CRCRC filter may have too high an impedance to perform well in an Aleph, although I haven't personally tried it. I would go for a regulated supply like in the Zen.
As for other improvements, replace the diff pair current source with a cascode and bias it with LEDs, and bias them with a J5xx current diode to the negative rail. As seen in various Aleph-X schematics.
Do some more advanced matching of your MOSFETs. Mount them on a temperature-controlled heater at 60C or whatever your design temperature is. Load them with a current source instead of a resistor, and set the current to be whatever idle current they will be handling in the amplifier. Buy 100 and match them really well 🙂
Put the front-end of the amp in a metal box. This will shield it from stray breezes that upset the DC balance. If you ground it, it might shield from EM, also.
As for other improvements, replace the diff pair current source with a cascode and bias it with LEDs, and bias them with a J5xx current diode to the negative rail. As seen in various Aleph-X schematics.
Do some more advanced matching of your MOSFETs. Mount them on a temperature-controlled heater at 60C or whatever your design temperature is. Load them with a current source instead of a resistor, and set the current to be whatever idle current they will be handling in the amplifier. Buy 100 and match them really well 🙂
Put the front-end of the amp in a metal box. This will shield it from stray breezes that upset the DC balance. If you ground it, it might shield from EM, also.
Standby mode for Zinsula
Hi everybody,
Tino,
this question appears often, I have made an answer to it with scheme when I have presented my Aleph3, the thread was called "I present you my Aleph3" if I remember, you can do a search for it or under mine name "Yonnat".
Hope this can help you, if you have any question I will be glad to help you.
In the standby mode you can listen to music, in my case I divided the bias at its half.
Best regards.
Yonnat.
Hi everybody,
Tino,
this question appears often, I have made an answer to it with scheme when I have presented my Aleph3, the thread was called "I present you my Aleph3" if I remember, you can do a search for it or under mine name "Yonnat".
Hope this can help you, if you have any question I will be glad to help you.
In the standby mode you can listen to music, in my case I divided the bias at its half.
Best regards.
Yonnat.
Thanks to William and Yonnat!
This will make life much more easier, having an Aleph with two faces
Cheers, Tino
This will make life much more easier, having an Aleph with two faces
Cheers, Tino
Bias on stock Aleph 2s
I am about to acquire a pair of Aleph 2s and I am interested in modifying them to maximise their potential, hence NP's list is of great interest to me:
I am about to acquire a pair of Aleph 2s and I am interested in modifying them to maximise their potential, hence NP's list is of great interest to me:
Nelson Pass said:
Get a fan. Use a DC fan and lower the voltage on it
to make it run slower and quieter. If you start it with
a higher voltage to get it going, you can turn the voltage
down some more after it starts.
to make it run slower and quieter. If you start it with
a higher voltage to get it going, you can turn the voltage
down some more after it starts.
but plug into a different circuit..........mine could be heard through the speakers (the PWM MIC502 that is)
William
William
Microchip makes PWM controllers with thermistor inputs for temperature sense. Try the TC642. You control the fan speed curve by choosing the right thermistor and a few resistors. I just implemented the circuit they give in the datasheet.
Fan
I remember a circuit that first charges a capacitor to railvoltage to start the fan, and then switches to a lower voltage for normal operation. Can't find it now, but will look later. I used it once for my computer fans (always too noisy). Perhaps someone else enjoys to redesign such a circuit? 😉
It's less noisy compared to PWM I think.
I remember a circuit that first charges a capacitor to railvoltage to start the fan, and then switches to a lower voltage for normal operation. Can't find it now, but will look later. I used it once for my computer fans (always too noisy). Perhaps someone else enjoys to redesign such a circuit? 😉
It's less noisy compared to PWM I think.
Nelson Pass said:
Hey Nelson, would you use Riken or Holco resistors for that circuit?
BTW, which is the gate on that device?
🙂 🙂 🙂
i dont think resistors make a difference in this particular application. Standard carbon film or 1% metal film would work as well and cost less than Dale or Holco.
The gate is the leg of the FET which isnt labelled D or S and is connected to the resistor.
Hope this helps. Regards
The gate is the leg of the FET which isnt labelled D or S and is connected to the resistor.
Hope this helps. Regards
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