The bass has fallen out of my amp!

inteificio · 3rd March 2006, 07:10 AM

Hi,

I have a Rotel RB-991 power amp. At everything but the lowest of volume levels is one of the best sounding amps I have heard.

The problem is recently I bought a new set of speakers that are VERY sensetive. At everything but the lowest volume levels the speakers are too loud to listen to.

At low volumes (sub 9'oclock on my pre) the bass is very quiet and the rest of the sound is sluggish. As soon as I break 9'oclock the whole hifi comes alive.

I have tried a variety of setups and this is a problem with the power amp, not a cheap volume pot as almost everyone assumes.

Is there a way of making the amp function well at a lower output level (even if it means losing some of the max power). I only tried this on max power once, when the neighbours were out. The people from two houses away complained.

sreten · 3rd March 2006, 07:19 AM

Hi,

Sounds like a problem with the speakers to me.

It is a simple fact the louder you play music the more bass
there appears to be, but it does level off at high volume.

So bass light speakers generally sound better with more juice.

Conversely rich sounding speakers designed for modest levels
can sound rather thick and syrupy if you press the loud pedal.

If this is the case the simplest option is a passive line level EQ.
Build in some attenuation to make your preamp more usable.

Very similar to this :

http://sound.westhost.com/bafflestep.htm#var-equaliser

Though the frequency might be lower than the BS frequency.

/sreten.

AndrewT · 3rd March 2006, 07:32 AM

Hi,
is the 991 a power amp?

Then attenuate the signal before it enters the power amp.

A pair of resistors inserted inside the RCA plugs will do it.

Try -10db to start with.

A line resistor of about 10k to the RCA centre pin and a 4k7 resistor from centre pin to ground.

Do this to the RCAs that plug into the power amp NOT at the output terminals of the pre-amp.

inteificio · 3rd March 2006, 12:14 PM

Hi,
thanks for that.

how would adding resistors in series differ from turning the volume down?

beppe61 · 3rd March 2006, 02:00 PM

Quote:

Originally posted by Peter Scowcroft
Hi,
I have a Rotel RB-991 power amp.
...

Excuse me, which preamp are you using?
Thank you and regards,

bg

Upupa Epops · 3rd March 2006, 02:17 PM

Problem is probably in new boxes, so voltage divider can't help, Andrew...

inteificio · 3rd March 2006, 05:07 PM

I use the rather pleasant RC-995. This is a huge improvment over the pooey RC-970bx. Even more than the HUGE 20 points in the name might suggest

inteificio · 3rd March 2006, 05:08 PM

While I am here the speakers are Acoustic Energy AE309s and the front end is a splendid AAA5

AndrewT · 3rd March 2006, 06:43 PM

Hi,
sticking my finger in the air and grabbing at anything that passes.

Could extremely low volume control settings affect the frequency balance of the signal passing to the power amp?

I wonder if capacitive coupling which will predominate in high frequency and almost no bass components of the music could augment the normal highly attenuated signal passing through the pre..

If this were the case then lost bass would be the end result.

inteificio · 3rd March 2006, 07:26 PM

that might be the case, it might be also completely over my head. The music sounds lifeless and with less bass at all below 9'oclock.

3rd March 2006, 07:10 AM	#1
inteificio diyAudio Member Join Date: Dec 2004 Location: York	The bass has fallen out of my amp! Hi, I have a Rotel RB-991 power amp. At everything but the lowest of volume levels is one of the best sounding amps I have heard. The problem is recently I bought a new set of speakers that are VERY sensetive. At everything but the lowest volume levels the speakers are too loud to listen to. At low volumes (sub 9'oclock on my pre) the bass is very quiet and the rest of the sound is sluggish. As soon as I break 9'oclock the whole hifi comes alive. I have tried a variety of setups and this is a problem with the power amp, not a cheap volume pot as almost everyone assumes. Is there a way of making the amp function well at a lower output level (even if it means losing some of the max power). I only tried this on max power once, when the neighbours were out. The people from two houses away complained.

3rd March 2006, 07:32 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, is the 991 a power amp? Then attenuate the signal before it enters the power amp. A pair of resistors inserted inside the RCA plugs will do it. Try -10db to start with. A line resistor of about 10k to the RCA centre pin and a 4k7 resistor from centre pin to ground. Do this to the RCAs that plug into the power amp NOT at the output terminals of the pre-amp. __________________ regards Andrew T.

3rd March 2006, 06:43 PM	#9
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, sticking my finger in the air and grabbing at anything that passes. Could extremely low volume control settings affect the frequency balance of the signal passing to the power amp? I wonder if capacitive coupling which will predominate in high frequency and almost no bass components of the music could augment the normal highly attenuated signal passing through the pre.. If this were the case then lost bass would be the end result. __________________ regards Andrew T.

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3rd March 2006, 07:19 AM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Sounds like a problem with the speakers to me. It is a simple fact the louder you play music the more bass there appears to be, but it does level off at high volume. So bass light speakers generally sound better with more juice. Conversely rich sounding speakers designed for modest levels can sound rather thick and syrupy if you press the loud pedal. If this is the case the simplest option is a passive line level EQ. Build in some attenuation to make your preamp more usable. Very similar to this : http://sound.westhost.com/bafflestep.htm#var-equaliser Though the frequency might be lower than the BS frequency. /sreten.

3rd March 2006, 12:14 PM	#4
inteificio diyAudio Member Join Date: Dec 2004 Location: York	Hi, thanks for that. how would adding resistors in series differ from turning the volume down?

3rd March 2006, 02:17 PM	#6
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Problem is probably in new boxes, so voltage divider can't help, Andrew...

3rd March 2006, 05:07 PM	#7
inteificio diyAudio Member Join Date: Dec 2004 Location: York	I use the rather pleasant RC-995. This is a huge improvment over the pooey RC-970bx. Even more than the HUGE 20 points in the name might suggest

3rd March 2006, 05:08 PM	#8
inteificio diyAudio Member Join Date: Dec 2004 Location: York	While I am here the speakers are Acoustic Energy AE309s and the front end is a splendid AAA5

3rd March 2006, 07:26 PM	#10
inteificio diyAudio Member Join Date: Dec 2004 Location: York	that might be the case, it might be also completely over my head. The music sounds lifeless and with less bass at all below 9'oclock.

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