Lowering noise floor with a Rotel 1090 and RF7s

[Fast1]

I use my system for both HT and 2ch. My mains are the only thing external amped at this time with the Rotel 1090. I have an obvious hiss at higher sound levels. I am wondering if there will be any mods for the amp, cabling, or otherwise to correct the noise or if I need to find another amp? On that note, what is recommended for these 7s? Needless to say, I like to make these 7s scream but I also am looking for quality sound and I would say right now, it is damn loud but could be MUCH more refined and detailed. Are tubes the way to go? can I still get crystal clear highs for HT or should I stay in the solid state area?

I am wondering if my older Denon 2803 receiver or Pioneer Elite dvd player are hurting me in the quest for more detail? Do I need a real preamp first?

OH, I did not the 7s' crossovers with film and foil caps and did the resistor mod as well. I should also note that I have never been happy with these 7s in the mid bass area. I run Velodyne 18 sub with them so it seems like I get nice lows and nice highs but the mid bass just seems flat. Am I asking to much of what I have? Maybe I need two pairs of 7s to get it done

[Frzninvt]

The hiss is most likely coming from the DSP's in the Denon receiver unless that Rotel 1090 has a poor S/N Ratio. The high efficiency of the RF-7's does not help either, it also could be the source material that you are listening too that has alot of background hiss to it. Is it there with no source present and the volume set low?

It will be tough to make them perfectly silent due to the efficiency, but what you can do is with everything turned off disconnect the RCA leads from the receiver to the 1090. Then power the system on and see if the hiss is present, if it is then it is coming from the amp, if it isn't it is being generated by the Denon receiver.

[Fast1]

OK, the hiss is much less noticable when bypassing the 1090 and using the amp in the receiver. The 7s are dead silent when volume is all the way down. When volume is all the way up but no source material is playing, I get a little hiss but what I would consider tolerable. I guess I can trace it to source material, BUT, my brother has a Paradigm system with NAD amps and it is silent with the same material. Acoustical presentations are my problem as well as HT because you just need a dead silent noise floor for quality listening.

I guess it may be possible that the receiver is causing this and by using the preouts, it has noise. The 1090 s/n is 125db. I have heard the 1090 can be noisy but not real sure what is causing the noise but sure sounds better without the amp. Maybe it is just "amplifying" the problem.

[Frzninvt]

The Paradigms don't have near the efficiency of the Klipsch's so it is no surprise to me that they are quiet with the same material.

If the internal amp in the Denon is not as noisy than that tells you right there alot of the hiss is being generated by the Rotel 1090, 125db S/N Ratio is an outstanding number but I wonder at what frequency it was measured sounds like that is a noisy amp. Run an internet search on the 1090 and see if anyone else has similar complaints.

I get a level of hiss but the speakers I have are super efficient and the NAD T163's are noisy, but I like the sonic ability and ease of use so it stay's in the rack for now.

[MrMcGoo]

Brandon,

The hiss may be from a impedance mismatch between the Denon and the Rotel. Dig out the manuals and look up the output impedance on the Denon's preamp and the input impedance on the Rotel.

You can also try a different receiver if you can beg or borrow one. The manuals may be the easier route.

My RF-7s are run by an outboard amp and receiver. There is no hiss.

The last thing that I would do in your case is get rid of the Rotel. It should do very good work with the RF-7s, based on the information from other Rotel 1090 owners. Hiss can get into the signal chain in many ways, then the high sensitivity speakers faithfully reproduce the input. It taks more work to get the best sound out of Klipsch speakers, but the bottom like is that VERY few speakers can compete with the dynamics and sound quality once the klipsch are "dialed in."

Bill

[Fast1]

You are a familiar face here. I have not been on in a while. Just busy I guess. Anyway, I always hear that the Klipsch is solid when setup properly so maybe I am not there yet. I plan to call Rotel and see if the engineers can tell me what I can upgrade in that tank to improve sound. I just hate hearing that it is close to this and near the quality of that, that little bit might me what my ears seek. Dunno. I do know that the " line conditioner" by Monster did squat but look cool. There is a little AC line noise at times in the house and that did nothing to help it.

If there are impedance issues, what can be done to correct it? Do you think that old Denon is in need of upgrade? I guess I can grab my bros preamp and try that. What about these noise suppressors I hear about? A joke?

[MrMcGoo]

If there are impedance issues, what can be done to correct it? Do you think that old Denon is in need of upgrade? I guess I can grab my bros preamp and try that. What about these noise suppressors I hear about? A joke?

The Denon may have too high an output impedance. If that turns out to be true, then a lower output impdance preamp/receiver may cure the problem.

Other things to look at: Get a big (14awg or 12 awg) and long extension cord. Try plugging the system into different circuits. Sometimes, the system is on the same power leg as a noisey device. I've had trouble with halogen lights for example. The microprocessors in my garage door openers don't like halogen near by etc.

Bill

PS: Refrigerators are also very noisy in some cases. B

[Fast1]

Yeah, I have tried different outlets and I am on about the cleanest one. I know the hiss I am getting though is not AC line induced. I thought those Monster units were supposed to "clean" the power? I wonder if they even suppress transients?

[MrMcGoo]

Brandon,

My best GUESS is that the Denon has digital noise in the preamp section. In any case, it is obsolete. Then ad a less than ideal output impedance and you have hiss. A separate preamp may be a good investment down the road, especially if you can get a good one with HDMI inputs for a reasonable price in the future.

Receivers have better features, but lower end receivers usally have noise issues. When you get into upper end receivers, the signal to noise ratios get better. Look for signal to noise ratios of 100 decibels or larger.

My machine has 105 db S/N ratio, but on certain recordings Dolby PL IIx post processing adds noise in the form of hiss. When I cut out the PL IIx post processing, the hiss goes away. Only a few recordings act this way and I have no idea what is going on. The process of converting SACD to PCM and then PL IIx Music post processing kills two cuts on the SACD. Bottom line is to try other forms of post processing to see if the hiss is reduced. All that takes is a few key strokes on the remote.

Bill

PS: See what stereo direct does to the hiss. B

[Fast1]

Yes, direct mode on the receiver does indeed lower the noise problem. Maybe I need to upgrade my preamp setup. So are you thinking that a high end receiver can hang with some of the quality preamps out there? I guess my brother is running an Outlaw. It seems to lack features like you say, but does everything that is really needed. I meen, who really uses all 200 of the dsp modes on a receiver anyway. Fun for about 30 seconds but is about it for me. PLII seems to work just fine for analog inputs.

So have you heard anything about these devices that attach to the speaker cables and are supposed to reduce noise?

[MrMcGoo]

The direct mode improvement tells me that the preamp section is not up to the task. The Denon 4xxx series should be more quiet as well as use better DACs etc. There are major model changes on the way at dates yet to be determined. HDMI 1.3 is on the way for higher end receivers that need to be hooked up to HD DVD and/or Blu-ray. Good deals will then be available for current models.

I bought my Pioneer flagship whenthe local Magnolia closed up. Full retail is never a good idea on a receiver due to the rapid rate of obsolescence.

Bill

[Fast1]

I firmly agree. I generally try to find year old models or something. So do you think the receiver can hold it's own against a pre/pro system?

OH, along the receiver lines, should I be staying with the Denon line or should I look at something else? I looked real hard at Marantz before because of the feedback on warmer sound. Any thoughts?

[MrMcGoo]

The upper end Denon's have a S/N ratio of 102 db or better. Some use torroidial transformers for better power and lower noise. Other brands that I like are the upper end Pioneer Elites and the better Yammies. Marantz is now owned by Denon.

I prefer to have THX post processing available, but this is a minor preference. Always get a processor or receiver with more inputs than you currently need.

The only complaint that I have with my Pioneer is that the crossover is global for all "small" speakers and has 50 Hz instead of 40 and 60 Hz on the crossover. these are very small problems.

Newer receivers handle bass frequencies better in some cases. I use a separate processor for bass, the Velodyne SMS-1. Look for better bass management in a processor/receiver and save a few bucks.

Bill

[Fast1]

Now you have me itchin to try something else to see where my noise factor will be. The whole time I was pointing at the amp because the noise only showed up when I brought the amp in. After only a few tests, it is damn interesting.

I heard the Yammies are pretty "to the point" on sound and not smooth with the Klipsch gear. Is that not the case?? I would be looking to use the receiver for 3-4 channels of surround and still run the mains with the Rotel if I can get by with it. I was kinda planning on pre/pro but who really needs 300 watts/chx5-6 for a movie? Klipsch is so sensitive anyway. Thoughts?

[MrMcGoo]

The upper end Denon will have plenty of power to run the center and surrounds, if they are run as small. The Rotel will take a huge burden off of the receiver. Just keep an eye on the Rotel's gain ratio versus the receiver's gain ratio. Be sure to calibrate with a sound meter and all should be well.

As far as brands are concerned, much of that depends on personal taste in sound. If you like Denon, you will be happy with the better models.

Bill

[Saturn5]

I'm running RF-7s with a QSC amp on an old Pioneer AVR. I can definitely tell I'm getting hiss from the Pioneer. With it off and the amp on, there is no hiss at all. Also, the hiss goes up quite a bit when using the Pioneer's digital signal processing.

I love the RF7s, but they will expose any weak links in the signal chain. I'll be upgrading to a new preamp before long. I may wait to see if Outlaw is going to release HDMI on their next flagship model.

[Fast1]

Well I just tried my brothers' Outlaw 950 preamp and it is actually more noisy than my Denon. Speakers are silent with the Rotel on until I turn on the preamp. I even tried turning off the DVD player to make sure there was no noise from it causing this and it looks like I will be in search of a "quiet" processor. What do I need? I am considering a higher quality Denon but is there something else I should look at?

[leok]

Brandon,

I suspect there is way too much gain in your system and you're not using any of the dynamic range of the pre .. just the noise floor. If there is gain on the amp, turn it down so the pre gain is higher. Otherwise try a Voltage divider between the pre and amp so the pre gain can be set higher. I'm not really a fan of preamps, but the performance shouldn't be as bad as you describe.

Leo

[Fast1]

Yes, I was rather surprised the Outlaw has noise. I guess they were noted for this and there are some fixes for it. As far as the gain on the amp, there is none and I know where you are coming from on that. The volume range on the Denon spans the entire range of adjustment.

[leok]

With a "noisy" pre, I guess a solution, if there is not a gain control; on the amp, is a voltage divider (attenuator) between pre and amp so that the pre can be run hot. What you want to do is be using a Volt or more of signal level out of the preamp. But this will blow you out of the house so you have to pad it back down to a fraction of a Volt before it goes into the amp. Cheap attenuators (volume controls) with RCA in/out connectors are available at various electronics stores. You can pick one up and see if it helps.

Leo