Aleph 30 gain question - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

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
Thread Tools Search this Thread
Old 26th September 2001, 08:28 AM   #1
Sud is offline 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.

BTW: I'll post pics when I've finsihed the case.
  Reply With Quote
Old 26th September 2001, 04:54 PM   #2
diyAudio Member
Join Date: Feb 2001
Location: Columbia, SC
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...

  Reply With Quote
Old 26th September 2001, 10:33 PM   #3
Koy is offline Koy  Czech Republic
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.
  Reply With Quote
Old 26th September 2001, 10:52 PM   #4
Geoff is offline Geoff  United Kingdom
diyAudio Member
Join Date: Apr 2001
Location: UK

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.

  Reply With Quote
Old 27th September 2001, 05:45 AM   #5
Koy is offline Koy  Czech Republic
diyAudio Member
Join Date: Jan 2001
Location: Zlin
Thanks. That is it.
  Reply With Quote
Old 31st October 2001, 10:02 PM   #6
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.
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

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?

All times are GMT. The time now is 06:46 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2