The best sounding audio integrated opamps - Page 188

panson_hk · 25th August 2010, 10:39 AM

I recently build a pre-amp using OPA134 (single channel version of OPA2134). The opamp is non-inverting unit-gain stage followed by a volume pot. It is indeed a very good sounding opamp.

Joachim Gerhard · 25th August 2010, 10:51 AM

What is your source impedance ?

panson_hk · 25th August 2010, 11:27 AM

my source is a CD player. In the previous post, I mentioned the order reversely. The pot is followed by the opamp.

AndrewT · 25th August 2010, 12:31 PM

Quote:

Originally Posted by panson_hk

The pot is followed by the opamp.

I was trying to understand why you decided to put a buffer in front of the pot.
Buffering the output of the pot makes sense.

Joachim Gerhard · 25th August 2010, 12:36 PM

When you have configured the Opamp as a voltage folower you get less distortion in the treble when you use a resistor with the same value as the source impedance instead of the short between Pin2 and Pin6. I am also astouned that you use a pot BEHIND the buffer. That destroyes the nice low output impedance and a buffer does not make much noise so you win little in SN with the pot at the output.

AndrewT · 25th August 2010, 12:42 PM

Quote:

Originally Posted by Joachim Gerhard

use a resistor with the same value as the source impedance instead of the short between Pin2 and Pin6.

YES!!!!
Some opamps behave so badly when output is fed back to -IN that the datasheet shows this extra resistor.

I have concluded that using this extra resistor cannot be any harm when any opamp is used in unity gain follower mode.

Joachim Gerhard · 25th August 2010, 12:47 PM

i usually use something around 1kOhm.

panson_hk · 25th August 2010, 12:59 PM

Quote:

Originally Posted by AndrewT

I was trying to understand why you decided to put a buffer in front of the pot.
Buffering the output of the pot makes sense.

Quote:

Originally Posted by Joachim Gerhard

I am also astouned that you use a pot BEHIND the buffer. That destroyes the nice low output impedance and a buffer does not make much noise so you win little in SN with the pot at the output.

I already made a correction in #1873. The pot is before of the opamp in the signal path. You don't see that? Or there is delay due to the server?

panson_hk · 26th August 2010, 10:59 PM

Quote:

Originally Posted by Joachim Gerhard

When you have configured the Opamp as a voltage folower you get less distortion in the treble when you use a resistor with the same value as the source impedance instead of the short between Pin2 and Pin6.

Is the the common-mode distortion in series-feedback configuration?

Joachim Gerhard · 27th August 2010, 02:53 AM

Yes.

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
-: Best audio OpAmps :-	audioPT	Parts	57	13th October 2011 01:47 AM
The Best Sounding DUAL opamps	mudihan	Chip Amps	214	1st May 2011 05:09 PM
best sounding Tx for sub 10watt class A audio amp?	mondogenerator	Solid State	2	2nd October 2009 05:21 AM
Help the Idiot: Simple, Great-Sounding Integrated Amp Designs	SRMcGee	Tubes / Valves	7	15th September 2005 06:43 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

25th August 2010, 10:39 AM	#1871
panson_hk :) diyAudio Member Join Date: Aug 2005 Blog Entries: 10	I recently build a pre-amp using OPA134 (single channel version of OPA2134). The opamp is non-inverting unit-gain stage followed by a volume pot. It is indeed a very good sounding opamp.

25th August 2010, 10:51 AM	#1872
Joachim Gerhard diyAudio Member Join Date: Mar 2009	What is your source impedance ?

25th August 2010, 11:27 AM	#1873
panson_hk :) diyAudio Member Join Date: Aug 2005 Blog Entries: 10	my source is a CD player. In the previous post, I mentioned the order reversely. The pot is followed by the opamp.

25th August 2010, 12:36 PM	#1875
Joachim Gerhard diyAudio Member Join Date: Mar 2009	When you have configured the Opamp as a voltage folower you get less distortion in the treble when you use a resistor with the same value as the source impedance instead of the short between Pin2 and Pin6. I am also astouned that you use a pot BEHIND the buffer. That destroyes the nice low output impedance and a buffer does not make much noise so you win little in SN with the pot at the output.

25th August 2010, 12:47 PM	#1877
Joachim Gerhard diyAudio Member Join Date: Mar 2009	i usually use something around 1kOhm.

27th August 2010, 02:53 AM	#1880
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Yes.

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