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used budget pre-amp or use denon 2 channel receiver as pre-amp?

post #1 of 23
Thread Starter 
Hi guys. I have a 2.1 setup in my bedroom that I use to play around with different speakers and compare them. I currently have a pair of Jamo C403's, Energy V5.1's, and a modified pair of BIC dv62si that I switch around periodically and I use them with and Energy S8.2 sub to handle the "bass".

I have been driving them with a denon dra-635r receiver (80 w/ch @ 8 ohm) for a couple years now, and it sounds pretty good. The one limitation I had was that its only rated down to 6 ohm in stereo mode, so I recently picked up an Audiosource Amp 3 (150 w/ch @ 8ohm). I figured the extra power and the capability to play down to 2 ohm in stereo would be good to have in case I pick up some 4 ohm speakers to play around with some day.

I hooked it up the other night using the pre-outs from the dra-635 to the amp 3 and it sounds pretty good. Didnt notice any big improvements, but I also havent had a chance to crank it up since it was 10:00 at night and I live in a condo.

My question is would a true preamp give me any better results over using the dra-635r as the preamp? I would only be looking to spend about $100+/- for a used preamp, maybe something like a adcom GFP-500. I definitely wouldnt consider myself an audiophile and I typically use an ipod dock as the source (ripped at 256 kbps), so I am thinking it wouldnt really be that beneficial to me, however that upgrade bug is biting me.

Just wanted to see peoples thoughts or if you have any recommendations for a budget preamp.

I look forward to the lossless vs. lossfull media bashing to follow biggrin.gif
post #2 of 23
If it were me I would just live with it for a while before I made any changes.
post #3 of 23
I would keep all electronic and max budget on upgrade speakers.
post #4 of 23
Quote:
Originally Posted by dwong View Post

I would keep all electronic and max budget on upgrade speakers.

+1 ...to both previous comments, actually.

keep thing as is for a bit. If you're looking for drastic change, speakers will satisfy that itch best. Having an amp with plenty of power on tap will give you good results with just about any speaker you throw at it... or connect to wink.gif
post #5 of 23
A good-quality preamp can easily cost $2000.

You could spend the money better on new speakers.

I suggest that you go to the KEF Direct website and get a pair of iQ70 speakers to replace your current front speakers; they have a great deal on them right now.

This will make your system sound about 200% better.
post #6 of 23
Thread Starter 
Quote:
Originally Posted by dwong View Post

I would keep all electronic and max budget on upgrade speakers.

Quote:
Originally Posted by aquaphile View Post

+1 ...to both previous comments, actually.
keep thing as is for a bit. If you're looking for drastic change, speakers will satisfy that itch best. Having an amp with plenty of power on tap will give you good results with just about any speaker you throw at it... or connect to wink.gif

Quote:
Originally Posted by commsysman View Post

A good-quality preamp can easily cost $2000.
You could spend the money better on new speakers.
I suggest that you go to the KEF Direct website and get a pair of iQ70 speakers to replace your current front speakers; they have a great deal on them right now.
This will make your system sound about 200% better.

Thanks for the thoughts guys. My energy V5.1's are pretty good speakers. Like I said, this is just for a bedroom setup so towers arent an option. In order to upgrade my speakers, I would have to spend some decent $ so I think I am set with my speakers.

After hearing your advice confirming that a true preamp wont make a huge difference, I was going to stick with the dra-635r as the preamp. But unfortunately, i started having a problem with it on sunday. I played around with it a bit on sunday morning and it was fine. I went to do some work on my kitchen and went back several hours later, turned it on and there was a buzzing/hum coming from the speakers. So I played around with some connections to trouble shoot where its coming from and I'm pretty sure its coming from the dra-635r. Its heard it when using the preouts to the amp and also when the speakers are connected directly to the dra-635r. I tried both the ipod connection and the CD player, and it was buzzing/humming for both. The volume of the buzzing/hum does not vary with the volume knob, its constant.

Any ideas what the problem may be?

Thanks.
post #7 of 23
Thread Starter 
So i did some trouble shooting and have found that its the connection from the pre outs on the receiver to the amp. from what i have been reading it sounds like a ground loop issue. anyone have any idea how to diagnose the problem? thanks in advance.
post #8 of 23
Quote:
Originally Posted by kgallerie View Post

So i did some trouble shooting and have found that its the connection from the pre outs on the receiver to the amp. from what i have been reading it sounds like a ground loop issue. anyone have any idea how to diagnose the problem? thanks in advance.

In your situation the most common source of a ground loop is the antenna connection to the receiver.

Since it seems like all inputs hum, the problem might be between the receiver and the power amp.

A Radio Shack ground isolator inserted between the power amp and the receiver can be a big help, or you can get a ground isolator for the antenna connection. These are two different kinds of devices - a ground loop isolator for RCA cables or for antenna cables, but they both accomplish the same basic thing.

Try disconnecting the antenna from the receiver and see if that is it, if so - go with the antenna ground isolator.

Other wise disconnect the receiver from the power amp and see if that is it. If so go with the RCA cable ground isolator.
post #9 of 23
Thread Starter 
Thanks for the advice. The hum goes away when disconnecting the interconnects between the receiver preouts and the amp. It also will go away when I unplug the amp.

When I take the amp out of the picture and run everything through the receiver, there is no hum. So I believe i narrowed it down to the amp.

From here, I will try using a "cheater plug" on the amp power cord (one that turns a 3 prong plug into a 2 prong plug) and see if that works. If not, then I'll likely try a ground isolator between the receiver and amp.

Another option that I was talking with a co-worker about is that I may have damaged the input RCA jack on the amp. He ran into that problem before, and it might make sense here. I have read that the RCA jacks on this particular amp are a bit on the cheap side and I had a set of interconnects that were really tight and need some force to get them on and off. I'll have to take the cover off and see if there's anything loose on the connection as well.

Thanks again for your advice. If you have any additional thoughts based on this additional info, I would appreciate it.
Edited by kgallerie - 1/7/13 at 10:29am
post #10 of 23
Quote:
Originally Posted by kgallerie View Post


From here, I will try using a "cheater plug" on the amp power cord (one that turns a 3 prong plug into a 2 prong plug) and see if that works. If not, then I'll likely try a ground isolator between the receiver and amp.

Cheaters are common but they represent a massive safety hazard. Nuff said?
post #11 of 23
Thread Starter 
Quote:
Originally Posted by arnyk View Post

Cheaters are common but they represent a massive safety hazard. Nuff said?

So what you are saying is that they are basically a band-aid to the real problem......think I got it. wink.gif

Besides that, you think I am on the right track?

Thanks again.
post #12 of 23
Quote:
Originally Posted by kgallerie View Post

Quote:
Originally Posted by arnyk View Post

Cheaters are common but they represent a massive safety hazard. Nuff said?

So what you are saying is that they are basically a band-aid to the real problem......think I got it. wink.gif

Understates the problem. Interfering with safety grounds (which is what cheaters do) is like drawing a sharp knife across your wrists.

Quote:
Besides that, you think I am on the right track?

I advised some specific actions in post 8, none of which involved a cheater.
post #13 of 23
Have you checked is the power amp is grounded ( with socket earth )? Reverse the status to try.
post #14 of 23
Thread Starter 
Quote:
Originally Posted by TLCW View Post

Have you checked is the power amp is grounded ( with socket earth )? Reverse the status to try.

Not sure exactly what that means? I have a outlet checker and it says the outlet they are plugged into is grounded properly. Is that what you are talking about?

What do you mean by reverse the status?

Thanks.
post #15 of 23
Quote:
Originally Posted by kgallerie View Post

Quote:
Originally Posted by TLCW View Post

Have you checked is the power amp is grounded ( with socket earth )? Reverse the status to try.

Not sure exactly what that means? I have a outlet checker and it says the outlet they are plugged into is grounded properly. Is that what you are talking about?

What do you mean by reverse the status?

OK, it seems that hinting around isn't working.

Here's your answer, more directly:

http://www.radioshack.com/product/index.jsp?productId=2062214



Plug it between the power amp and the preamp.
post #16 of 23
Thread Starter 
Quote:
Originally Posted by arnyk View Post

OK, it seems that hinting around isn't working.

Here's your answer, more directly:

http://www.radioshack.com/product/index.jsp?productId=2062214



Plug it between the power amp and the preamp.

LOL.....Thanks Arny......I understood the ground loop isolator you recommended. I will be trying that.

That doesnt appear to be what TLCW was referring too though. I was looking to see if he had another idea in case the ground isolator doesnt work.

This system is in my condo (i live with my girlfriend elsewhere) which I only get to once every week or two, so I havent had a chance to try any of this out yet. I am looking for any suggestions so that when I do get up there, I can try several different things if necessary. I will post back after I have a chance to try this out.

Thanks for all the advice!
Edited by kgallerie - 1/10/13 at 12:09pm
post #17 of 23
Thread Starter 
Also, Arny......since you have your full name in your profile, I figured you were "somebody" in the audio industry. So I did a google search and found a lot of things about blind listening testing. I'm finding it all to be a very interesting and complicated debate. I'm not going to go into details of my opinions on the matter since we could read for a lifetime on it (even though I do agree that blind listening tests are probably the best method of comparing audio equipment for "audible" differences). However, I find your research and experimentation on the issue quite respectable. wink.gif
Edited by kgallerie - 1/10/13 at 12:08pm
post #18 of 23
Quote:
Originally Posted by kgallerie View Post

Also, Arny......since you have your full name in your profile, I figured you were "somebody" in the audio industry.

I have my full name in my profile because I wish to be as truthful as possible.
Quote:
So I did a google search and found a lot of things about blind listening testing. I'm finding it all to be a very interesting and complicated debate.

Interesting, yes.

Conceptually, DBTs are pretty simple and simplify many things.
post #19 of 23
Thread Starter 
Quote:
Originally Posted by arnyk View Post

I have my full name in my profile because I wish to be as truthful as possible.

lol......i stated that solely for the reason I decided to google you.... i hope you didnt take it any other way! biggrin.gif

Quote:
Originally Posted by arnyk View Post

Interesting, yes.
Conceptually, DBTs are pretty simple and simplify many things.

As a structural engineer (obviously not electrical per posts above tongue.gif), I agree its a simple concept.....but alot of people make it complicated.

I'm really looking forward to listening to your debate with John Atkinson on the subject. From what I have read, it sounds like it gets a little heated at times....... I love good debates. Coming from the engineering/science mindset, I'm sure I'll get a little fired up too! biggrin.gif
post #20 of 23
Thread Starter 
So I connected the receiver (preamp) to the amp using the radio shack ground loop isolator yesterday. It worked for the most part. When I put my ear within 6 inches of the speaker, I could hear a very faint hum (barely audible from 6" away), but besides that its good.

But then when I turned off the receiver (preamp) so that the amp was the only thing still on (using the auto-on/off feature), it hummed again. It isnt as loud as the previous hum, but definitely noticeable. Is this normal?

Is there anything else I can try to minimize or get rid of the hum besides bringing in an electrician?

Thanks again for all your help guys!
post #21 of 23
Quote:
Originally Posted by kgallerie View Post

So I connected the receiver (preamp) to the amp using the radio shack ground loop isolator yesterday. It worked for the most part. When I put my ear within 6 inches of the speaker, I could hear a very faint hum (barely audible from 6" away), but besides that its good.

Reading between the lines, your speakers are very efficient for your application, which makes them more sensitive to hum than is typical.

One might say that this is part of nature's way of telling you to just hook the speakers to the receiver and dispose of the power amp.
Quote:
But then when I turned off the receiver (preamp) so that the amp was the only thing still on (using the auto-on/off feature), it hummed again. It isnt as loud as the previous hum, but definitely noticeable. Is this normal?

Yes, it can be.
Quote:
Is there anything else I can try to minimize or get rid of the hum besides bringing in an electrician?

Most people control power to the preamp and the amp together. The crudest way to do this is to plug them both into the same power strip and use the swtich on the power strip to control both components.

Many components have a switched power outlet for controlling the power to other components in the system.

At this point your problem is self-inflicted.
post #22 of 23
Thread Starter 
Quote:
Originally Posted by arnyk View Post

Reading between the lines, your speakers are very efficient for your application, which makes them more sensitive to hum than is typical.

One might say that this is part of nature's way of telling you to just hook the speakers to the receiver and dispose of the power amp.

Crud....i just bought the amp....mad.gif I would like to keep it though to have the capability to safely run 3 or 4 ohm loads if the occasion arises. I like to play around and try out different speakers that I find on craigslist. For example, I just recently found the matching satellite speakers to the passive subs that I've had for years from the Cambridge Soundworks original Ensemble set. They are all 6 ohm so when run together in parallel they run at ~3 ohm. I also grabbed a pair of older ADS Sat7's that were 4 ohm a year or 2 ago to try out. Ended up not liking the sound and they were pretty beat up so I returned them.
Quote:
Originally Posted by arnyk View Post

Yes, it can be.

Most people control power to the preamp and the amp together. The crudest way to do this is to plug them both into the same power strip and use the swtich on the power strip to control both components.

Many components have a switched power outlet for controlling the power to other components in the system.

I have them both plugged into the same power strip but its behind the little tv/audio stand they are in. I guess I could move it out to the side so the switch is accessible.
Quote:
Originally Posted by arnyk View Post

At this point your problem is self-inflicted.

What do you mean by self-inflicted? By adding the amp to my system?

I was more asking if there are any other ways to get rid of the loop with my current and desired components. Would a true power conditioner help? Could it be that the power cord on the amp has a bad ground connection(the cord is removable)? Any other way to properly ground the amp to help?

The system sounds fine with the loop isolator installed, however in my mind I still know that there is an issue since its heard with the amp on and the receiver off.

Thanks again for you help Arny!
Edited by kgallerie - 1/14/13 at 10:28am
post #23 of 23
Thread Starter 
So i figured I would post an update.

I had read that using an amp with a 2 prong cord would probably eliminate the ground loop issue. It just happened that an Emotiva UPA-200 was available on craigslist for a good price, and when I looked at the pictures, the power connection on the back of the amp was only a 2 prong connection. So I picked it up and gave it a try. The cord that came with the Emotiva had a 3 prong plug, so it was a 2 prong connection on one end and a 3 prong on the other. However, since there was no ground connection at the amp, it is likely working as a 2 prong connection would.

The ground loop hum was much quieter with the Emotiva than it was with the Audiosource, but it was still present. I could only hear it within a couple feet of the speaker where previously i could hear it throughout the room. So I decided to hook up the ground loop isolator that had helped so much with the Audiosource, and it actually magnified the ground loop noise with the Emotiva a lot. It was louder than the original hum with the Audiosource without the isolator! Go figure......

However, I did find the root cause of the ground loop. I unplugged the cable wire from the digital converter in the same room and bingo! I have no idea why I didnt try that before, after all i had read about cable wires being the cause. I guess since I had previously isolated the TV and cable from the audio system, I didnt think it could be the cause, but it definitely was.

Since I found out what the cause of the loop was, it comes down to which amp I like the sound of better. So I did a quick comparison and it sounded like there was a distinct difference between the 2. I didn't do any level matching, etc. so it really wasnt a scientific test. I played a few songs that I know really well and use a lot for demo'ing speakers (dave matthews and zac brown). I found the emotiva to be more detailed and a bit more forward sounding, where the audiosource amp 3 was a bit more laid back and warmer sounding. The Audiosource seemed to be missing something in the upper midrange which left my ears wanting something more, almost like a hole in that range. This was strange to me because I typically like a more laid back, warm sound, but in this case I felt like it was missing something in comparison to the Emotiva. Perhaps it was the placebo effect, or the lack of level matching that made the difference, but if you read about Audiosource, the general consensus is that they are more laid back and warmer sounding.

Anyway......they are both great sounding amps (powerful and clean), and the difference in sound seemed noticeable, but not night and day or anything. The Emotiva is 125 w/ch where the Audiosource is 150 w/ch. The advantages to the Audiosource are that it has A/B switching and its spec'd to run down to 2 ohms, where the Emotiva only has one set of speaker outputs and is spec'd down to 4 ohm. I guess I will hold on to both for a while and listen to them a bit more before I make a decision.

Unfortunately I will have to sell one of them, because that was the deal with the girlfriend when I bought the Emotiva. frown.gif

Thanks again to the guys with original advice regarding the pre-amp, and Arny for all your help with the ground loop issue.
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