Aleph 30 gain question

Sud · 26th September 2001, 08:28 AM

Hi All,

I've been constructing the first of a pair of DIY Aleph 30 monoblocks, and today got to the point where I could test the amplifier. I hooked the Aleph's input directly to the left channel line-level signal from a CD player.

Now, I figured that given the direct connection between the CD player and the Aleph, the Aleph would be driven at close to full power. So, I selected a CD which starts off very quietly and slowly gets louder.

Contrary to my expectations, the sound is not very loud for the sensitivity of the test speaker I used (6 ohm impedence, 86dB SPL sensitivity). I know that the Aleph 30 is not the beefiest of the Alephs by a long margin, but I would expect that 30W would generate 90-100dB with the test speaker I used. Instead, I measured around 80-83dB with my SPL meter, which confirms sound output corresponding to about 1-2W of output power from the Aleph.

Any ideas? What range of input signal swing is the Aleph series designed to operate with? The CD player generates an unbalanced signal with the normal line-level voltage(2.83V I think). Is this enough to properly drive the Aleph?

Aside from this, the amplifier is working very nicely.

Any comments greatly appreciated.

Sud
BTW: I'll post pics when I've finsihed the case.

GRollins · 26th September 2001, 04:54 PM

Sud,
The first thing that occurs to me is to ask what load the CD player is designed to drive. If it is specified working into, say, a 1M load, it will not deliver as much voltage into the Aleph, which has a fairly low input impedance, and for that matter, fairly low gain--20 dB, I believe, in unbalanced mode.
Another factor is what has to come off of the CD in order to get the output to that level. You may have noticed that CDs play at different volumes. Perhaps the one you chose isn't giving enough signal to drive the CD player to the nominal 2.83V level.
Chances are that you're going to need a preamp...

Grey

Koy · 26th September 2001, 10:33 PM

The same for me...
I am not sure about some mistake in the schematics for Aleph 30. The resistor network /Q2) consist of 100k and 68.1k to the ground (gain =1.4). Originally Aleph 3 uses 10k and 1k (gain =10). I hope I am right. This could explain low gain of the amp. Adding 10k to the 68k increases the gain to the about 12x, like Volksamp states.
I think CD player ( with 2V) should be enough to drive the amp.

Geoff · 26th September 2001, 10:52 PM

Sud/Koy

There is no error in the Aleph 30 schematic. When used with a unbalanced source, the negative input should be earthed. This will put R3 (10k) in parallel with R6 (68k1) and will give a gain of just over 12. Nelson covers this in one of his articles, though I cannot remember which one at the moment.

Geoff

Koy · 27th September 2001, 05:45 AM

Thanks. That is it.

leroy · 31st October 2001, 10:02 PM

Thanks a lot!

This forum is a major help to me. I've just finished my Aleph30 prototype and suffered the same problem mentioned above.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Gain Aleph 3 and Aleph L?? Nelson?	Metric	Pass Labs	1	10th April 2006 07:13 PM
Aleph 5 with no (few) gain	ElectroNick	Pass Labs	4	13th March 2005 01:08 PM
Question: Gain and Aleph	Jay	Pass Labs	1	16th September 2003 03:10 PM
Aleph gain	Koy	Pass Labs	1	30th January 2002 10:55 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

26th September 2001, 08:28 AM	#1
Sud diyAudio Member Join Date: Sep 2001 Location: Perth, Australia	Hi All, I've been constructing the first of a pair of DIY Aleph 30 monoblocks, and today got to the point where I could test the amplifier. I hooked the Aleph's input directly to the left channel line-level signal from a CD player. Now, I figured that given the direct connection between the CD player and the Aleph, the Aleph would be driven at close to full power. So, I selected a CD which starts off very quietly and slowly gets louder. Contrary to my expectations, the sound is not very loud for the sensitivity of the test speaker I used (6 ohm impedence, 86dB SPL sensitivity). I know that the Aleph 30 is not the beefiest of the Alephs by a long margin, but I would expect that 30W would generate 90-100dB with the test speaker I used. Instead, I measured around 80-83dB with my SPL meter, which confirms sound output corresponding to about 1-2W of output power from the Aleph. Any ideas? What range of input signal swing is the Aleph series designed to operate with? The CD player generates an unbalanced signal with the normal line-level voltage(2.83V I think). Is this enough to properly drive the Aleph? Aside from this, the amplifier is working very nicely. Any comments greatly appreciated. Sud BTW: I'll post pics when I've finsihed the case.

26th September 2001, 04:54 PM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Sud, The first thing that occurs to me is to ask what load the CD player is designed to drive. If it is specified working into, say, a 1M load, it will not deliver as much voltage into the Aleph, which has a fairly low input impedance, and for that matter, fairly low gain--20 dB, I believe, in unbalanced mode. Another factor is what has to come off of the CD in order to get the output to that level. You may have noticed that CDs play at different volumes. Perhaps the one you chose isn't giving enough signal to drive the CD player to the nominal 2.83V level. Chances are that you're going to need a preamp... Grey

26th September 2001, 10:33 PM	#3
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	The same for me... I am not sure about some mistake in the schematics for Aleph 30. The resistor network /Q2) consist of 100k and 68.1k to the ground (gain =1.4). Originally Aleph 3 uses 10k and 1k (gain =10). I hope I am right. This could explain low gain of the amp. Adding 10k to the 68k increases the gain to the about 12x, like Volksamp states. I think CD player ( with 2V) should be enough to drive the amp.

26th September 2001, 10:52 PM	#4
Geoff diyAudio Member Join Date: Apr 2001 Location: UK	Sud/Koy There is no error in the Aleph 30 schematic. When used with a unbalanced source, the negative input should be earthed. This will put R3 (10k) in parallel with R6 (68k1) and will give a gain of just over 12. Nelson covers this in one of his articles, though I cannot remember which one at the moment. Geoff

27th September 2001, 05:45 AM	#5
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	Thanks. That is it.

31st October 2001, 10:02 PM	#6
leroy diyAudio Member Join Date: Oct 2001	Thanks a lot! This forum is a major help to me. I've just finished my Aleph30 prototype and suffered the same problem mentioned above.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)