External Amps dont make a difference ...whaa?

[panteragstk]

I hate to say it, but I think that's just a fact of life with the Crown XLS. Many of us use them for subs where such issues aren't really a concern. I have an XLS 1502 powering a sub but I never considered using it full range. It definitely gave me a hum, so I put a low pass on it with a miniDSP which pretty much took care of it--something you can't do if running it full range.

I've had a Crown XLS running my subs for years. Never had any sort of hum.

 

[lovinthehd]

I've had a Crown XLS running my subs for years. Never had any sort of hum.

Me too, even when running as external amps or two ch amps. I did have some ground loop hum that was pretty bad at the previous place I lived due poor cable installation.

 

[PENG]

Me too, even when running as external amps or two ch amps. I did have some ground loop hum that was pretty bad at the previous place I lived due poor cable installation.

If we are still talking about AdrianQ 's issue, in his post#3 he said it was a "high pitch feedback.

I read so much on ground loops and obviously still dont understand it fully but how do I get a ground loop if the crown isn't even plugged in to anything, only the two rca's from my avr ? I've also grounded both chassis together but still can hear a high pitch feedback.

Ground loop hum typically would produce a 100/120 Hz (depending on the power line freq.) that should not sound "high pitch" though somehow I think it probably has something to do with a ground loop via the RCA connectors that are typically connected to the chassis "ground". I know that doesn't make logical sense but you probably what I mean..

@AdrianQ , I suppose the high pitch noise came from your speakers right? If so, is the level constant or would vary with the volume setting?

 

[lovinthehd]

If we are still talking about AdrianQ 's issue, in his post#3 he said it was a "high pitch feedback

I was also thinking of JonAAs comment but noise in general. I did wonder if it was some sort of amp hiss he was hearing which has been reported on extremely high sensitivity speakers. Feedback didn't make sense to me unless maybe he had plugged something in very oddly....or has something picking things up like a microphone....

 

[PENG]

I was also thinking of JonAAs comment but noise in general. I did wonder if it was some sort of amp hiss he was hearing which has been reported on extremely high sensitivity speakers. Feedback didn't make sense to me unless maybe he had plugged something in very oddly....or has something picking things up like a microphone....

Exactly, I was going to say that about "feedback" too, that we typically hear when someone grab a mic in a meeting hall, or even church..

 

[lovinthehd]

Exactly, I was going to say that about "feedback" too, that we typically hear when someone grab a mic in a meeting hall, or even church..

Or Jimi! Is it remotely possible that the Crown amp is exciting some transformer or similar (at least I think you were mentioning something similar elsewhere). Where is the amp in relation to the avr?

 

[highfigh]

I'd still try lifting the ground rather than tying a ground between that and the avr.

Hum caused by a ground loop happens because there's resistance between equipment- lifting the ground could potentially cause the chassis of the piece that's no longer grounded to become electrically 'hot', no pun intended.

 

[highfigh]

Or Jimi! Is it remotely possible that the Crown amp is exciting some transformer or similar (at least I think you were mentioning something similar elsewhere). Where is the amp in relation to the avr?

If only the audio cable is connected, I seriously doubt it although transformers can buzz if they were made poorly.

 

[lovinthehd]

Hum caused by a ground loop happens because there's resistance between equipment- lifting the ground could potentially cause the chassis of the piece that's no longer grounded to become electrically 'hot', no pun intended.

I just meant to test the problem, not as a permanent solution unless of course yer willin' to get fried perhaps.

 

[highfigh]

I just meant to test the problem, not as a permanent solution unless of course yer willin' to get fried perhaps.

I heard a comedian say that his ex-wife called to tell him that the bathroom light had burned out, then she asked what she should do. He told her "First thing, you need to fill the tub with water...".

 

[lovinthehd]

If only the audio cable is connected, I seriously doubt it although transformers can buzz if they were made poorly.

Was more thinking there's something in my Crown manual about placing directly on top of certain gear....so went to my manual and it sez (the odd spacing is the copy function from the pdf :

CAUTION! Do not locate sensitive high-gain equipment such as
preamplifi ers or tape decks directly above or below the unit. Because this
amplifi er has a high power density, it has a strong magnetic fi eld which can
induce hum into unshielded devices that are located nearby. The fi eld is
strongest just above and below the unit.
If an equipment rack is used, we recommend locating the amplifi er(s) in
the bottom of the rack and the preamplifi er or other sensitive equipment at
the top.

 

[lovinthehd]

That said I have two Crowns sitting fairly close below my avr, on a lower shelf, so also separated by a thick shelf.

 

[PENG]

Was more thinking there's something in my Crown manual about placing directly on top of certain gear....so went to my manual and it sez (the odd spacing is the copy function from the pdf :

CAUTION! Do not locate sensitive high-gain equipment such as
preamplifi ers or tape decks directly above or below the unit. Because this
amplifi er has a high power density, it has a strong magnetic fi eld which can
induce hum into unshielded devices that are located nearby. The fi eld is
strongest just above and below the unit.
If an equipment rack is used, we recommend locating the amplifi er(s) in
the bottom of the rack and the preamplifi er or other sensitive equipment at
the top.

Not saying you got it, but exactly the kind of innovation or even just imagination that I was hoping for!! But yeah, as someone insisted before on another thread about EMI being the cause for hum, but you know my opinion on this if you frequented that thread.. that nothing is certain when it comes to this kind of thing!! In this case though, I think it is a good possibility, and it could be easily tested, simply by relocating one of the units, assuming he has a long enough RCA interconnect.

Edit: We forgot one thing though, OP said the high pitch noise was there with the Crown power cord not connected. So the position issue should not apply, we are back to square one I guess!!

 

[highfigh]

Was more thinking there's something in my Crown manual about placing directly on top of certain gear....so went to my manual and it sez (the odd spacing is the copy function from the pdf :

CAUTION! Do not locate sensitive high-gain equipment such as
preamplifi ers or tape decks directly above or below the unit. Because this
amplifi er has a high power density, it has a strong magnetic fi eld which can
induce hum into unshielded devices that are located nearby. The fi eld is
strongest just above and below the unit.
If an equipment rack is used, we recommend locating the amplifi er(s) in
the bottom of the rack and the preamplifi er or other sensitive equipment at
the top.

Right, but that would be more likely recommended to prevent the field from the Crown amp intruding on the other pieces since the Crown transformer needs to provide more for its output than a source device or AVR.

The recommendation that the amp(s) be placed at the bottom is interesting, too- usually, amps are placed at the top to prevent their heat from affecting anything above, although the Crown amps run pretty cool when compared with some others.

 

[panteragstk]

Was more thinking there's something in my Crown manual about placing directly on top of certain gear....so went to my manual and it sez (the odd spacing is the copy function from the pdf :

CAUTION! Do not locate sensitive high-gain equipment such as
preamplifi ers or tape decks directly above or below the unit. Because this
amplifi er has a high power density, it has a strong magnetic fi eld which can
induce hum into unshielded devices that are located nearby. The fi eld is
strongest just above and below the unit.
If an equipment rack is used, we recommend locating the amplifi er(s) in
the bottom of the rack and the preamplifi er or other sensitive equipment at
the top.

I will say it doesn't have the lowest noise floor, but you have to get awfully close to the speaker (at least in my experience) to hear it.

I've got an AVR and another external amp right next to my XLS 1500. I've also got a PC in the mix. No issues. Granted it is one of the class D models.

 

[lovinthehd]

Right, but that would be more likely recommended to prevent the field from the Crown amp intruding on the other pieces since the Crown transformer needs to provide more for its output than a source device or AVR.

The recommendation that the amp(s) be placed at the bottom is interesting, too- usually, amps are placed at the top to prevent their heat from affecting anything above, although the Crown amps run pretty cool when compared with some others.

Or it's less shielded than some amps? I've maybe gotten my Crowns slightly warm....in a warm room. In an enclosed cabinet the additional air circulation mightr even help another unit? Dunno.

I do wonder the physical stack or not the OP might have, tho....

 

[PENG]

Right, but that would be more likely recommended to prevent the field from the Crown amp intruding on the other pieces since the Crown transformer needs to provide more for its output than a source device or AVR.

The recommendation that the amp(s) be placed at the bottom is interesting, too- usually, amps are placed at the top to prevent their heat from affecting anything above, although the Crown amps run pretty cool when compared with some others.

I think the Crown XLS amps use switching mode power supply and class D amp. So that thing should be okay even at the bottom. Worst case scenario the forced air cooling could save the day.

 

[dolamite]

I do believe that external power amps can make a difference, but there are many variables that you have to consider. I believe it really depends on the speaker and amp combo. I have a pair of Klipsch La Scalas which are 105 dB efficient. I have used a Marantz SR-5009 and I have used a Denon POA-8200 amp to drive them. In comparing the marantz receiver to the denon amp, I do get better sound with the denon amp. Is it night and day different? No, but the midrange and high end just have more magic to them. I believe the imaging is better and things jump out better. I'm out of audiophile lingo... I'll just say I like it better to keep it simple.

The denon amp is a dual mono design. It should have no cross talk issues and it has thd of .02. The denon amp also has lower noise floor. I believe on lesser speakers I wouldn't hear a difference or if my speakers were less efficient maybe it would be closer. I also think if I moved up the chain in receiver quality I think it would be closer as well. I think the true is answer is it depends, but I believe for most situations that getting a solid quality receiver is going to be good enough for most scenarios.

 

[JerryLove]

Sigh...

Crosstalk: The speakers cross-talk in the room. What do you imagine the actual threshold is for cross-talk to be audible in a real listening scenario?

THD: Again: this feels like a number for the sake of a number. Do you have any data suggesting that any ABX test has shown a preference (or even detectability) on the THD numbers described?

Noise Floor: That's one of the numbers for dynamic range. Again: can you relate this to something audible?

"Highs sound better"; which is really strange since the tweeter is about the easiest thing to drive. Has this been DBX tested? It seems like this might be psychosomatic.

I've owned one pair of speakers that I can recall where amp made a difference (A pair of B&W 801Ns). Bass response was better with an amp that scaled down to 2 ohms well (I used a McIntosh 2120 to accommodate that). Looking at their resistance curve, I think I might understand why.

I assert that amps are "sufficient" and "insufficient", and when they are the latter, we can see why in the numbers.

 

[lovinthehd]

Sigh...

Crosstalk: The speakers cross-talk in the room. What do you imagine the actual threshold is for cross-talk to be audible in a real listening scenario?

THD: Again: this feels like a number for the sake of a number. Do you have any data suggesting that any ABX test has shown a preference (or even detectability) on the THD numbers described?

Noise Floor: That's one of the numbers for dynamic range. Again: can you relate this to something audible?

"Highs sound better"; which is really strange since the tweeter is about the easiest thing to drive. Has this been DBX tested? It seems like this might be psychosomatic.

I've owned one pair of speakers that I can recall where amp made a difference (A pair of B&W 801Ns). Bass response was better with an amp that scaled down to 2 ohms well (I used a McIntosh 2120 to accommodate that). Looking at their resistance curve, I think I might understand why.

I assert that amps are "sufficient" and "insufficient", and when they are the latter, we can see why in the numbers.

What cracks me up is when vinylphiles think they need separate amps to help out with crosstalk I always liked this comment from Douglas Self, the well known amp designer:


"There is no need to go to the expense of monobloc power amplifiers in order to keep crosstalk under control even when making it substantially better than the -20dB that is actually necessary. The techniques are conventional; the last stereo power amplifier I designed managed an easy -90dB at 10kHz without anything other than the usual precautions in this area. Dedicated followers of fashion pay dearly for the privilege as the cost of the mechanical parts will be nearly doubled."