Aleph P volume

febytam · 9th February 2007, 07:45 AM

Anyone tried to place the volume control at input rather than original design at output stage? Sound any difference and trade off?

hifimaker · 9th February 2007, 04:45 PM

This has been discuss quite a bit. Nelson has said the volume control can be either before or after his premaps, but after is better.

Do a search for attenuators or BOSOZ volume controls.

-David

GRollins · 10th February 2007, 04:00 AM

This is one of those things you can talk about endlessly, but trying it both ways will tell you what you want to know.
If you have a fixed, unchanging, front end, the impedance presented to the input device will be more-or-less known. The pot at the back will not only reduce the signal, but the noise as well. On the other hand, the circuit may be more sensitive to overload.
Putting a pot at the front allows you to trim a hot signal, but whatever noise the circuit generates will always be there, even if there's no signal.

Grey

EUVL · 10th February 2007, 06:08 AM

> The pot at the back will not only reduce the signal, but the noise as well. ......

All true, and I can confirm that from my own experience.
The disadvantage of a pot at the back is :

1) Your preamp has to swing a long more voltage than the other alternative. Not a problem for Aleph P, but certainly not true for all other preamp circuit.

2) If you have low impedance load (say 100-200 ohms) at the output, then you need thermally stable, high-power resistors in your attenuator of probably quite low values.

Otherwise I am all for pot at the back.

Patrick

9th February 2007, 07:45 AM	#1
febytam diyAudio Member Join Date: Jun 2005 Location: Hong Kong	Aleph P volume Anyone tried to place the volume control at input rather than original design at output stage? Sound any difference and trade off?

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
volume and aleph 1.7	Kongen	Pass Labs	2	9th April 2006 12:45 AM
Aleph P1.7 volume control	supernet	Pass Labs	3	23rd September 2004 06:30 PM
Aleph-X volume	Prune	Pass Labs	39	15th March 2004 06:05 AM
Aleph P1.7 Volume Control	jleaman	Pass Labs	7	18th September 2002 02:13 PM
Aleph L volume control	diy student	Pass Labs	2	31st August 2001 06:03 PM

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

9th February 2007, 04:45 PM	#2
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	This has been discuss quite a bit. Nelson has said the volume control can be either before or after his premaps, but after is better. Do a search for attenuators or BOSOZ volume controls. -David

10th February 2007, 04:00 AM	#3
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	This is one of those things you can talk about endlessly, but trying it both ways will tell you what you want to know. If you have a fixed, unchanging, front end, the impedance presented to the input device will be more-or-less known. The pot at the back will not only reduce the signal, but the noise as well. On the other hand, the circuit may be more sensitive to overload. Putting a pot at the front allows you to trim a hot signal, but whatever noise the circuit generates will always be there, even if there's no signal. Grey

10th February 2007, 06:08 AM	#4
EUVL diyAudio Member Join Date: Oct 2003	> The pot at the back will not only reduce the signal, but the noise as well. ...... All true, and I can confirm that from my own experience. The disadvantage of a pot at the back is : 1) Your preamp has to swing a long more voltage than the other alternative. Not a problem for Aleph P, but certainly not true for all other preamp circuit. 2) If you have low impedance load (say 100-200 ohms) at the output, then you need thermally stable, high-power resistors in your attenuator of probably quite low values. Otherwise I am all for pot at the back. Patrick