Frequency response vs. output power

MikeW · 28th January 2007, 10:12 PM

How much does the frequency response change for one watt output to full rated output power on a Pass labs amp? All the reviews I read are for small signal frequency response. Is there a difference. Does anyone have some data?

GRollins · 28th January 2007, 10:58 PM

Mike,
Bode is the keyword you're searching for. As in Bode plot. Yes, the bandwidth shrinks as the power (interpret this as gain) increases.
Chip opamps have really stupid open loop bandwidths...like 100Hz. It's only after you apply gonzo amounts of feedback that the bandwidth becomes tolerable.
If you meditate on all the ramifications and implications of this junk you're likely to end up like me--meaning someone who thinks that 250kHz to 300kHz open loop bandwidth is a good start. I say that having just come up from the Dungeon wherein my Evil Experiments managed a whole, astounding 10kHz. Unsatisfactory. Need to stop and think things over. Bummer.

Grey

P.S.: Good talking to you. There's no one to talk audio with out here in the hinterlands.

flg · 28th January 2007, 11:16 PM

Grey, Southern R.I. isn't any better. But, MikeW, your only a stone's throw away...

Babowana · 29th January 2007, 01:26 AM

Quote:

Originally posted by GRollins

Yes, the bandwidth shrinks as the power (interpret this as gain) increases.

Somewhat difficult for me to understand.
I am simplified. Nevertheless, as the rolloff is hapenning
depending purely on the RC network, I understand that the
rolloff point is independant of the power level.
I.e. the bandwidth of an amp is the same at any power level.
The distortion might be increased at the power increase, though.

Where I'm wrong . . . ?

jackinnj · 29th January 2007, 02:17 AM

Quote:

Originally posted by GRollins
P.S.: Good talking to you. There's no one to talk audio with out here in the hinterlands.

the hinterlands aren't in SC -- at least you guys know what a "grit" is.

Nelson Pass · 29th January 2007, 06:18 PM

Quote:

Originally posted by MikeW
How much does the frequency response change for one watt output to full rated output power on a Pass labs amp? All the reviews I read are for small signal frequency response. Is there a difference. Does anyone have some data?

It's pretty much the same.

Nelson Pass · 29th January 2007, 06:24 PM

A little later:

Since there was an XA100.5 on the bench being tested for
frequency response, I checked it at 2W, 50W and 100W.

It was 2 dB down at 100 KHz at 2W, 2 db at 50W, and 2.2 dB
at 100W.

gl · 29th January 2007, 11:28 PM

So Nelson,

I don't recall having heard of an XA100.5 previously. What is the difference between it and the the XA100? Thanks.

Graeme

Babowana · 30th January 2007, 12:49 AM

Quote:

Originally posted by Nelson Pass

It was 2 dB down at 100 KHz at 2W, 2 db at 50W, and 2.2 dB
at 100W.

I guess the last value, 2.2dB, must be due to
the accuracy tolerance of your farsighted glasses

MikeW · 30th January 2007, 04:31 PM

Quote:

Originally posted by Nelson Pass
A little later:

Since there was an XA100.5 on the bench being tested for
frequency response, I checked it at 2W, 50W and 100W.

It was 2 dB down at 100 KHz at 2W, 2 db at 50W, and 2.2 dB
at 100W.

Thanks

28th January 2007, 10:12 PM	#1
MikeW diyAudio Member Join Date: Sep 2002 Location: North of Boston	Frequency response vs. output power How much does the frequency response change for one watt output to full rated output power on a Pass labs amp? All the reviews I read are for small signal frequency response. Is there a difference. Does anyone have some data? __________________ MikeW

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
Understanding Zaph's Frequency Response and Power Handling Curves	jarsoffart	Multi-Way	5	24th March 2009 08:29 PM
Output transformers and frequency response	dsavitsk	Tubes / Valves	21	3rd December 2006 06:48 PM
frequency response	pmarcouxx	Digital Source	2	20th July 2005 07:43 PM
Doubts on Phase Response and Frequency Response	dumrum	Multi-Way	11	5th April 2004 10:39 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

28th January 2007, 10:58 PM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Mike, Bode is the keyword you're searching for. As in Bode plot. Yes, the bandwidth shrinks as the power (interpret this as gain) increases. Chip opamps have really stupid open loop bandwidths...like 100Hz. It's only after you apply gonzo amounts of feedback that the bandwidth becomes tolerable. If you meditate on all the ramifications and implications of this junk you're likely to end up like me--meaning someone who thinks that 250kHz to 300kHz open loop bandwidth is a good start. I say that having just come up from the Dungeon wherein my Evil Experiments managed a whole, astounding 10kHz. Unsatisfactory. Need to stop and think things over. Bummer. Grey P.S.: Good talking to you. There's no one to talk audio with out here in the hinterlands.

28th January 2007, 11:16 PM	#3
flg diyAudio Member Join Date: Jul 2005 Location: North East	Grey, Southern R.I. isn't any better. But, MikeW, your only a stone's throw away...

29th January 2007, 06:24 PM	#7
Nelson Pass The one and only Join Date: Mar 2001	A little later: Since there was an XA100.5 on the bench being tested for frequency response, I checked it at 2W, 50W and 100W. It was 2 dB down at 100 KHz at 2W, 2 db at 50W, and 2.2 dB at 100W.

29th January 2007, 11:28 PM	#8
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	So Nelson, I don't recall having heard of an XA100.5 previously. What is the difference between it and the the XA100? Thanks. Graeme