2. amps-preamps
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Help choose best amp/preamp combo?

Hi there
I am new to audio forum.Helo every one here can help me.I do build a 2 channel stereo with JBL sub.here is my system :Parasound a21 amp + Emotiva xsp1(gen 2)+ pair of B&W 805 Nautilus.To be honest, I do loved the sound system very clear and crisp on high and midrange with powerful bass tights.but it is LACKing of Warm sound.I do loved the warm sound is top priority.couple months ago I do have Rotel 1095 amp pair with Rotel rsp1570 + b&w cdm1 Nt sound is clear crisp and WARMER but sound is THIN compare to Parasound.but Rotel sound is warm which I like much.I also heard that Parasound a21 is warm sound too.but in my taste it is not.my question is the amp do produce a warm sound or Pre-amp produce a warm sound or the speaker do make the sound warm?I am confused and I want change my system to Rotel rb1582mk2 + Rotel rc1580 pre-amp because I heard that B&W speaker and Rotel is relate to each other and their product is matching together in sound.especially BW speakers is sound good with Rotel amp.is this true.and how you guy advised me to keep Parasound a21 and changing Pre-amp to either Parasound P5 or Rotel rc1580? Or go full system with Rotel like Rotel rb1582mk2 + Rotel rc1580?I am confused now and need your help.Thank You in advance.
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mesch
1,679 posts
 
The differential input impedances of amplifiers is a product of their design and what brings this on is beyond my scope of understanding. I do believe that this differential, in consideration alone, has little value in determining which amplifier is 'best' for a particular system.

What is of most importance is that the ratio of the amplifier input impedance be at least 10X (some say 20X) that of the output impedance of the driving preamplifier. What is the output impedance of the preamp? It is likely that it is low enough that the ratio would be met by all the aforementioned amplifiers.

I agree with those who suggest trying a tube preamplifier. Hope you enjoy the Rotel amplifier. 
erik_squires
5,268 posts
 
One other thing to try of course is the treble control.  I would try turning it down a couple of notches.  This depends on how it's implemented though. They aren't all shaped the same.

Usually any impedance over 10k is considered high and acceptable by most preamps.  The more sensitive preamps will start to roll off high frequencies as the amplifier impedance drops or the volume control is changed.  Look at a couple of reviews at Stereophile. In the measurements you'll see this effect.

No modern solid state amplifier should care however, and many if not most can tolerate down to 600 Ohms.
andrei_nz
106 posts
 
Whatever you do, keep the Parasound.  I agree a tube pre-amp is a good way to go.  Have a look for example at Rogue Audio.  Also the Doge pre-amp (I nearly bought one).
auxinput
1,538 posts
 
I will also vote for a new preamp.  Many people suggested tube.  I would suggest looking at a Class A preamp (Krell or maybe Pass Labs, maybe even Parasound JC2).  The FET preamps may have more of a lush sound then the bipolar Krell stuff (which is typically more clean sounding).  All of it should be tight and crisp, but would give you a lot more warmth and body then the Emotiva XSP.   Tube may be good here too (also McIntosh), but the tube or mac stuff may be too slow if you like crisp sound.
atmasphere's avatar
atmasphere
7,068 posts
 
Usually any impedance over 10k is considered high and acceptable by most preamps. The more sensitive preamps will start to roll off high frequencies as the amplifier impedance drops or the volume control is changed.
This statement is not correct! For example ARC recommends the amplifier input impedance be no lower than 30K. In any event, if the preamp does not like the input impedance because its too low, bass will suffer at any setting of the volume control.

This is moot if the Parasound stays and I agree with others that it is the better amp over a Rotel! It has a high enough input impedance that most tube preamps will be fine with it. There are balanced line tube preamps; we make some, so does BAT, ARC and others.
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