Aleph-X volume

Prune · 20th February 2004, 10:39 PM

I just got the hifizen Aleph-X PCBs and I have two questions. Does the Aleph-X have enough gain to be driven directly by a CD player or DAC, without a preamp? And, is it possible to use a passive volume control, say just put a 10K attenuator at input?

GRollins · 21st February 2004, 03:29 AM

Depends on your player, but very likely yes.
Yes, but it wouldn't hurt to go for a little higher resistance on the pot.

Grey

Peter Daniel · 21st February 2004, 03:44 AM

I was using my Aleph X driven directly from a DAC. I had 500ohm switching attenuator at DAC's output. With 92dB speakers, I never run out of gain, but I was using 200k feedback resistor (instead of usual 100k).

Prune · 21st February 2004, 04:32 AM

My DAC won't drive 500 ohms properly as I can't fit larger DC blocking caps in the enclosure.
GRollins says to use over 10K. You are using lower. I'm confused.

Fred Dieckmann · 21st February 2004, 04:46 AM

By one of them or both............

One would need to know if your driving your Aleph X single ended and what the feedback resistor values are. You need to know the output level for the CD player. I believe its usually a couple volts RMS. The efficency of your speakers is a big factor and an Aleph X with 15 or 20 volt rails is going to require a pretty efficient speaker.

A passive volume control is not the best idea since the Amps feedback will not be symetrical. The series resistance from the output of the pot is part of the feedback resistor for a 10K pot the maximum resistance will be 2.5K which which gives a 12.5K resistance for the input feedback resistor for one side of the amp 10K for the other side if the input resistor is grounded for running the amp single ended. Using a larger pot will make this imbalance even worse and I haven't a clue why Mr. Rollins would reccomend it. Ask him, maybe there is a reason I don't know about.

Knowing the gain for the amp you are using now would be useful since the Aleph X doesn't have a large amount of gain and maybe considerable less than many amps. With the feedback resistor values Mr. Rollins can tell you what the gain is running the amp with the input single ended. I believe he was disscussing this mode of operation with some one the other day and has more experience with this amp than I do.

Prune · 21st February 2004, 05:30 AM

I'll be driving it balanced. The balanced output of the DAC is 1.8V. I plan to build the Aleph-X for about 100W/channel, but I have not started building yet so no value is fixed. I was hoping for a balanced input impedance of not much less than 10K.

grataku · 21st February 2004, 05:52 AM

Look Prune, give it a shot with passive se drive use whatever pot you got 10k, 20k. At the most you won't achieve sonic bliss.

I don't remember exactly but the input sensitivity of the AX in its "regular" version (15V rails 5 amps bias one pair of 044 per side) was in the ball park of 2V RMS and the voltage gain is about 20 dB for 8 ohms so plenty of juice to run your speakers. The input imp. is no less than 10K

Fred Dieckmann · 21st February 2004, 06:00 AM

"driving it balanced"

Ganged pots......... or what? Give the poor guy some specific advice.

So much for super symmetry......... I guess it would be sorta sorry semi symmetry

You sound like you know who with this post.

Prune · 21st February 2004, 06:08 AM

I will drive it balanced. I don't understand why using a balanced volume control would destroy the symmetry.
To rephrase my question, I want to find out what value balanced pot/attenuator would be best (while trying not to have a too low value as I can't drive it).

Fred Dieckmann · 21st February 2004, 06:17 AM

Get a dual ganged linear 100K or 50K. The 10K input impedance will give you law faking sort off log pot when connected to the wiper of the pot for its output. Passive preamps reqiuire short low capacitance interconnects and really don't have the dynamics of a buffered pot.

"I don't understand why using a balanced volume control would destroy the symmetry."

It won't ......... my post was about driving it single ended which what Grataku was recommending and I thought you were doing originally. You have to give enough information to get a useful answer..........

Maybe Grey is the one to help you. He will probably look at your post tommorow. I think I am just confusing you. BTW I see you're Canadian.

20th February 2004, 10:39 PM	#1
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	Aleph-X volume I just got the hifizen Aleph-X PCBs and I have two questions. Does the Aleph-X have enough gain to be driven directly by a CD player or DAC, without a preamp? And, is it possible to use a passive volume control, say just put a 10K attenuator at input?

21st February 2004, 04:46 AM	#5
Fred Dieckmann diyAudio Retiree Join Date: Oct 2002 Location: Spain or the pueblo of Los Angeles	Need more information............... By one of them or both............ One would need to know if your driving your Aleph X single ended and what the feedback resistor values are. You need to know the output level for the CD player. I believe its usually a couple volts RMS. The efficency of your speakers is a big factor and an Aleph X with 15 or 20 volt rails is going to require a pretty efficient speaker. A passive volume control is not the best idea since the Amps feedback will not be symetrical. The series resistance from the output of the pot is part of the feedback resistor for a 10K pot the maximum resistance will be 2.5K which which gives a 12.5K resistance for the input feedback resistor for one side of the amp 10K for the other side if the input resistor is grounded for running the amp single ended. Using a larger pot will make this imbalance even worse and I haven't a clue why Mr. Rollins would reccomend it. Ask him, maybe there is a reason I don't know about. Knowing the gain for the amp you are using now would be useful since the Aleph X doesn't have a large amount of gain and maybe considerable less than many amps. With the feedback resistor values Mr. Rollins can tell you what the gain is running the amp with the input single ended. I believe he was disscussing this mode of operation with some one the other day and has more experience with this amp than I do.

21st February 2004, 06:00 AM	#8
Fred Dieckmann diyAudio Retiree Join Date: Oct 2002 Location: Spain or the pueblo of Los Angeles	Where does the pot go? "driving it balanced" Ganged pots......... or what? Give the poor guy some specific advice. So much for super symmetry......... I guess it would be sorta sorry semi symmetry You sound like you know who with this post.

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21st February 2004, 03:29 AM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Depends on your player, but very likely yes. Yes, but it wouldn't hurt to go for a little higher resistance on the pot. Grey

21st February 2004, 03:44 AM	#3
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	I was using my Aleph X driven directly from a DAC. I had 500ohm switching attenuator at DAC's output. With 92dB speakers, I never run out of gain, but I was using 200k feedback resistor (instead of usual 100k).

21st February 2004, 04:32 AM	#4
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	My DAC won't drive 500 ohms properly as I can't fit larger DC blocking caps in the enclosure. GRollins says to use over 10K. You are using lower. I'm confused.

21st February 2004, 05:30 AM	#6
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	I'll be driving it balanced. The balanced output of the DAC is 1.8V. I plan to build the Aleph-X for about 100W/channel, but I have not started building yet so no value is fixed. I was hoping for a balanced input impedance of not much less than 10K.

21st February 2004, 05:52 AM	#7
grataku diyAudio Member Join Date: Dec 2000 Location: -	Look Prune, give it a shot with passive se drive use whatever pot you got 10k, 20k. At the most you won't achieve sonic bliss. I don't remember exactly but the input sensitivity of the AX in its "regular" version (15V rails 5 amps bias one pair of 044 per side) was in the ball park of 2V RMS and the voltage gain is about 20 dB for 8 ohms so plenty of juice to run your speakers. The input imp. is no less than 10K

21st February 2004, 06:08 AM	#9
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	I will drive it balanced. I don't understand why using a balanced volume control would destroy the symmetry. To rephrase my question, I want to find out what value balanced pot/attenuator would be best (while trying not to have a too low value as I can't drive it).

21st February 2004, 06:17 AM	#10
Fred Dieckmann diyAudio Retiree Join Date: Oct 2002 Location: Spain or the pueblo of Los Angeles	Get a dual ganged linear 100K or 50K. The 10K input impedance will give you law faking sort off log pot when connected to the wiper of the pot for its output. Passive preamps reqiuire short low capacitance interconnects and really don't have the dynamics of a buffered pot. "I don't understand why using a balanced volume control would destroy the symmetry." It won't ......... my post was about driving it single ended which what Grataku was recommending and I thought you were doing originally. You have to give enough information to get a useful answer.......... Maybe Grey is the one to help you. He will probably look at your post tommorow. I think I am just confusing you. BTW I see you're Canadian.

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