A couple of questions about optimizing my analog/digital stereo setup.

[MrMcSick]

First my setup is as follows.

Yamaha HTR-5990 A/V reciever - used solely as a preamp
Crown Com-tech 410 power amp
Technics SL-1500 turntable with Shure m91 cartridge
HP desktop for all digital media using the Digital Coaxial output on the motherboard
Acoustic Research AR90 speakers

Now there are 2 issues I would like to address-
First being, the yamaha reciever gets rather toasty after around 60 mins of hard use.
It is being used as only a preamp for this system and the Crown comtech is used as the poweramp. Reason's being the yamaha only has options of 8 or 6 ohm speaker loads while my AR90's are 4 ohms and can dip down to 3 ohms during playback. Also the AR90's LOVEEEEEEEEEEEEE power and everyone suggest at least 200 watts per channel rms to drive them since they aren't efficient. This seems to work out great and sounds wonderful but the heat out of the yamaha is crazy since it isn't even powering anything. I have a set of rca cables going from the preamp front left and right outputs on it into the left and right inputs of the Comtech. I have the speaker selector in the yahama to off (A,B,off) and no speaker cable hooked up to the back of it. I also went in and turned the fan on to run at all times in the one submenu. Now WHY does it give off soooo much heat like its actually driving speakers when it is hooked up to nothing? It even shut off on me 2 times for thermal overload in the 6 months or so with this setup. Is there a way to just unplug the power amp section inside since its not being used anyways? Like say can I just unplug the connector going to the board that the speaker outputs are on or something? I don't understand why it would still be sending everything through the poweramp and generating so much heat when there isn't even a load to drive on it. Any ideas here?

Second is I have a ground loop between my computer and Yamaha reciever. As soon as the digital coax cable is connected hum instantly is produced and you can hear the hard drive spinning and everything. This computer is not stock. I had it setup exactly the same way, digital coax out into digital coax in of the yamaha before when the computer was bone stock. Now I have a different/upgraded motherboard/processor/power supply/graphics card but still the same computer case and it still made no difference in the grounding. I swapped out the motherboard backing plate where the connectors are on the back as they have a different layout too so I am not sure why the loop exists. As for the home wiring outlets - I am using 2 different outlets to power all of my stuff in this setup as I have tons of more gear for studio use intermingled. Both outlets are on the same circuit. One is on the left of the room and the other on the right of the room, that is all. The house is from the 70's so its all 3 prong cabling. I have a surge protector on each outlet. If I plug the power amp into the opposite outlet as the computer the hum significantly increases. I have them on the same outlet which keeps the noise down to a level where it is only really noticable during music breaks or soft parts. It makes no difference if I plug the yahama reciever into the same or opposite outlet. If I don't have the coax cable from the computer hooked up everything is fine and almost dead quiet. Does the ground loop exist in the computer, the yamaha reciever or the crown poweramp???????

Thanks for the help guys.

 

[johnda]

Wow, a ton of work out there!
I am assuming you are using the pre out from the Yamaha to the crown. Is the Crown connected to an external outlet and not the outlet on the Yamaha? Is the volume control on the Yamaha controlling the Crown OK?
If this how you are doing the lash up, I am out of ideas, good luck!

 

[AlphaEcho35]

If you have the option of using a TOSLink interface (optical) instead of the coax, that might solve your ground loop issue.

 

[AlphaEcho35]

Any other special reason why you are using the Yamaha as a preamp? If it is just for volume control, there are quite a few inexpensive alternatives to using such a complex component as a preamp. (A Schiit Sys for $49 is a good example.)

Wait a minute - if you are going digital coax (SPdif) from the computer to the Yamaha, then you are also using it as a DAC....

If it were me, I would get that overly complex Yammy out of my audio system. (I use a similar model in my home theater system...)

 

[MrMcSick]

johnda - Yes, as stated I am using the preamp outputs of the yamaha to the inputs of the crown and controlling the volume of everything with the volume knob on the yamaha.
I have the crown and the computer plugged into the same surge protector on the right side of the room outlet. The yamaha is plugged into the surge protector in the left side of the room outlet. It makes no difference whether the yamaha is plugged in to the same or different outlet. The power amp and computer must be plugged into the same outlet though or the hum and background noise increases substantially. I cannot plug the power amp into the outlets on the back of the yamaha as the power amp uses a 3 prong plug and the outlets are only 2 prong on the reciever but more importantly the power amp draws waaaaaayyyyyyyyyyyyy too much current and wattage to be plugged into there anyways. The circuit breaker on the back of the power amp is freaking 12 amps lol. I forget exactly how much wattage it consumes at a high duty cycle but it has to be at the very least 500 watts.

gguillot - The digital out on my computer is only a coax, no optical. I did experiment with another piece of gear though - I am a recording musician and have a home studio setup with that computer as well. I run a Focusrite Sapphire pro 40 firewire audio interface for my recording and it has a coax digital output on it as well. When I have the signal routed to go from the computer to the Focusrite then from its digital out into the yamaha it is fine. It's just a hassle to have it setup that way as you have to configure the software to route the stereo signal to the digital out instead of the analog balanced outputs that are feeding my studio monitors. Plus it's another piece of gear to eat power and complicate things. I'd rather just figure out why i get a ground loop when running from the computers motherboard digital out.

I understand that using the yamaha as just a preamp isn't the best choice over just a dedicated stand alone preamp but it's hard to match all the great feature of the yamaha's preamp section. I use the speaker calibration it has built in that you use a mic with to correct for room acoustics and distance ect. I also use the dual channel digital graphic equalizer. It also has great high quality ad/da convertors at 24 bit 192khz resolution that i push all my digital music up to in the computers output configurization. Needing a preamp with both a phono preamp and a digital preamp for both of my play sources is also a necessity. I would love to find a preamp that had features such as all of these but can't seem to find anything or if you do it's usually super expensive high end gear which I can't afford. Edit- I also use this setup to listen to high quality digital audio like DVD Audio disc's and high resolution Flac files that require Dolby digital or DTS 2 channel encoding to play from my computer that the receiver can decode. I can even play Blu-ray audio discs but lacking the newer DTS Master and Dolby TrueHD of more modern receivers it will play them at the lower encoded DTS format ect but still work. A regular DAC won't have DTS and such and won't be able to play these files.

 

[AlphaEcho35]

Since you want to keep the Yamaha in your system, you should eliminate the Crown amp. You can run those AR90's on the Yamaha just fine unless you like to really crank it up for long periods of time. If that's the case, buy/sell/trade the AR90's for a more efficient pair of speakers that better match your amplifier (the Yamaha.)
Also, where is your Yamaha placed - does it have enough space around it for cooling? That could be the source of your heat problem. I am guessing the ground loop hum goes away if you eliminate the Crown amp from the signal path....

 

[MrMcSick]

See the thing is the Crown amp just gets slightly warm under hard use. Hard use is playing at near maximum volume for 60-90 mins. I think I agree that the Crown amp is the culprit in the grounding issue and will investigate it further. If the Yamaha gets near thermal shutdown without even a load on it I doubt it will fair better when trying to push the AR90's but I guess it's worth a try. When I steeped up from my old Kenwood receiver that was 100 watts 20-20k rms to this setup with the Crown pushing 200 watts from 20-20k rms there was a significant improvement in the bass. The crown has indicators on the front of it that I love too. Not sure if they are to be trusted but they are great for peace of mind. The ODEP indicator stays lit until the power amp's energy supply starts to diminish. I can't recall if I've ever seen it flicker even on the most intense bass demands. Also there is a IOC indicator which seems to light up when the amp senses distortion in the output section, which I have seen light up under the most demanding needs and backed off the volume until gone. I think these are great tools to use in keeping the system in an optimal safe setting. Regular receivers won't tell me of such things until I can pick up distortion or such with my ears and by that time it might be too late. I have no desire in getting rid of my AR90's unless for a pair of AR9's lol. I realize they are more of a critical listening/reference style speaker than an efficient party/rock speaker like my fathers JBL L-100's but the sound quality is no comparison between the two. If there was just a way to shut off or disable the power section of the Yamaha so that it was not on the verge of overheating I would have almost no complaints for the setup. As for wear it is placed - it is inside an open faced cabinet/tv stand with around 3 inches on each side and about 5 inches on the top of clearance. The Crown power amp is in the same cabinet and has no problem with cooling what so ever though.

 

[for_p1]

If Yamaha has setting for speaker impedance (like 8 vs. 4 ohms) - set it to lowest value. It will reduce amplifier rail voltage. Even if no speakers are connected, it will reduce power dissipated in output transistors. But I suspect the most heat is produces by digital audio and video processors in your Yamaha, which are always running.

To eliminate ground loop the best option is to use optical connection from your computer. Check if your audio card or motherboard has this option. Sometimes you have to install add-on card for that.

 

[cartop]

Not to harp on it but you do not hook up your wires going to the amp to the speaker outputs. If your receiver can run an amp,and it can, it needs to have pre-outs and they will be labeled pre-outs. If you have the wires hooked up to the same connections you would normally connect your speakers to, That is wrong.

 

[MrMcSick]

I will try to lower the ohm selection to the 6 ohm setting. It only has an 8 and 6 ohm setting. I hear you on the video and digital section be on all time but if played at background volume the heat is barely noticable. Also there is a listening mode that can be used that is basically mosty analog. It shuts off the front display, the digital eq is bypassed and the video circuits are shut off and it still makes no difference. Remember i have the cooling fan running at all times once the power is turned on and this is still happenning. Its like the signal is going through the whole power amp section with a high load on it like it would with it playing through the speakers as the heatsink that the power amp mosfets are on are where most of the heat is coming from. Thanks for_p1

Cartop - i am well aware that you cannot take power amp outputs and use them as an input signal. I never stated i was doing this. My receiver has seperate preamp outputs for all 5.1 channels. I am running the front left and right preamp out rca's into the input of the crown power amp as already stated.

 

[MrMcSick]

I went back and read over the crown's manual. They listed all the ways to connect the input signal. They give you 2 ways to connect a unbalanced signal (which is what i am dealing with) and i tried the other method and it fixed my ground loop. The inputs on the power amp a screw terminal and are positive, ground and negative on each of the 2 channels. The first way (which it was originally hooked up as) had the center pin of the rca out going to the positve input and the outside of the rca cable goung to the negative. I then hooked up a small jumper wiring going from the negative input terminal to the ground input terminal as well and it took away the hum.

 

[cartop]

[QUOTE="MrMcSick,
Cartop - i am well aware that you cannot take power amp outputs and use them as an input signal. I never stated i was doing this. My receiver has seperate preamp outputs for all 5.1 channels. I am running the front left and right preamp out rca's into the input of the crown power amp as already stated.[/QUOTE]

OK great, I wasn't trying to insult you, just making sure.

 

[BradV]

First my setup is as follows.

Yamaha HTR-5990 A/V reciever - used solely as a preamp
Crown Com-tech 410 power amp
Technics SL-1500 turntable with Shure m91 cartridge
HP desktop for all digital media using the Digital Coaxial output on the motherboard
Acoustic Research AR90 speakers

Now there are 2 issues I would like to address-
First being, the yamaha reciever gets rather toasty after around 60 mins of hard use.
It is being used as only a preamp for this system and the Crown comtech is used as the poweramp. Reason's being the yamaha only has options of 8 or 6 ohm speaker loads while my AR90's are 4 ohms and can dip down to 3 ohms during playback. Also the AR90's LOVEEEEEEEEEEEEE power and everyone suggest at least 200 watts per channel rms to drive them since they aren't efficient. This seems to work out great and sounds wonderful but the heat out of the yamaha is crazy since it isn't even powering anything. I have a set of rca cables going from the preamp front left and right outputs on it into the left and right inputs of the Comtech. I have the speaker selector in the yahama to off (A,B,off) and no speaker cable hooked up to the back of it. I also went in and turned the fan on to run at all times in the one submenu. Now WHY does it give off soooo much heat like its actually driving speakers when it is hooked up to nothing? It even shut off on me 2 times for thermal overload in the 6 months or so with this setup. Is there a way to just unplug the power amp section inside since its not being used anyways? Like say can I just unplug the connector going to the board that the speaker outputs are on or something? I don't understand why it would still be sending everything through the poweramp and generating so much heat when there isn't even a load to drive on it. Any ideas here?

Second is I have a ground loop between my computer and Yamaha reciever. As soon as the digital coax cable is connected hum instantly is produced and you can hear the hard drive spinning and everything. This computer is not stock. I had it setup exactly the same way, digital coax out into digital coax in of the yamaha before when the computer was bone stock. Now I have a different/upgraded motherboard/processor/power supply/graphics card but still the same computer case and it still made no difference in the grounding. I swapped out the motherboard backing plate where the connectors are on the back as they have a different layout too so I am not sure why the loop exists. As for the home wiring outlets - I am using 2 different outlets to power all of my stuff in this setup as I have tons of more gear for studio use intermingled. Both outlets are on the same circuit. One is on the left of the room and the other on the right of the room, that is all. The house is from the 70's so its all 3 prong cabling. I have a surge protector on each outlet. If I plug the power amp into the opposite outlet as the computer the hum significantly increases. I have them on the same outlet which keeps the noise down to a level where it is only really noticable during music breaks or soft parts. It makes no difference if I plug the yahama reciever into the same or opposite outlet. If I don't have the coax cable from the computer hooked up everything is fine and almost dead quiet. Does the ground loop exist in the computer, the yamaha reciever or the crown poweramp???????

Thanks for the help guys.

I can't see how an AVR used as a pre-amp could ever result in overheating.

Only solution that works properly to eliminate ground loop hum is to connect a grounding wire between the two chassis of the connected components.

 

[Bill Ferris]

I can't see how an AVR used as a pre-amp could ever result in overheating.

Well, I can`t speak about a AVR, as I`ve never owned one, but my Integra A/V/P runs pretty warm just turned on idling with no audio sent to it, and it is just used for my living room`s HT audio source selection and decoding only, with no HDMI video signal to be processed ever have been sent through it.

These A/V units electronics have a few very warm running LSI (Large Scale Integration) processing IC chips inside for processing the HDMI video and any decoding of digital audio signals, plus a power supply along with its various hot operating voltage regulators, and in the case of a AVR, there is the multiple power amps, which even though not connected to any speakers, still have their multiple power amp`s idling current running through them all generating waste heat internally, it all adds up !

And stacking gear on top of their enclosures blocking any cabinet vents, or installing them in a air flow constricted/restricted enclosed rack, furniture cabinet can cook their internal circuitry easily leading to premature equipment failures !

 

[jayvis]

Well, I can`t speak about a AVR, as I`ve never owned one, but my Integra A/V/P runs pretty warm just turned on idling with no audio sent to it, and it is just used for my living room`s HT audio source selection and decoding only, with no HDMI video signal to be processed ever have been sent through it.

These A/V units electronics have a few very warm running LSI (Large Scale Integration) processing IC chips inside for processing the HDMI video and any decoding of digital audio signals, plus a power supply along with its various hot operating voltage regulators, and in the case of a AVR, there is the multiple power amps, which even though not connected to any speakers, still have their multiple power amp`s idling current running through them all generating waste heat internally, it all adds up !

And stacking gear on top of their enclosures blocking any cabinet vents, or installing them in a air flow constricted/restricted enclosed rack, furniture cabinet can cook their internal circuitry easily leading to premature equipment failures !

True. I've never had an AVR that didn't run pretty warm, even at idle.