steve Posted August 27, 2001 Share Posted August 27, 2001 Got a question for all you techies out there. As we all know, Klipsh are known for their sensitivity ratings, especially the KHorns. I run a pair of KHorns, powered by an 8 watt tube amp built by Assemblage (Sonic Frontiers) and an Adcom GFP565 preamp. I got tired of having no volume control range i.e. turning it up to "2" on a scale of 10 was the loudest I could take! So here's my question.. I bought an outboard attenuator made by Niles Audio, (4 inputs, one output) and put it between my CD player (Adcom GCD750) and the preamp. Turned it to about 1/3rd of the way up, and now I can use the Adcom's volume control with greater flexibility, from 1 to 5 out of a scale of 10, hence the volume changes gradually. Here's the question. What with a new piece of equipment introduced (basically a filter) would you say I have degraded the sound? I ask this, because I swear I can hear a very slight addition to "background hiss". I was told that since this attenuator is passive, that nothing would be added. Any input (pun not intended) is appreciated! Thanx! Steve Quote Link to comment Share on other sites More sharing options...
discorules Posted August 27, 2001 Share Posted August 27, 2001 quote: Originally posted by steve: Got a question for all you techies out there. As we all know, Klipsh are known for their sensitivity ratings, especially the KHorns. I run a pair of KHorns, powered by an 8 watt tube amp built by Assemblage (Sonic Frontiers) and an Adcom GFP565 preamp. I got tired of having no volume control range i.e. turning it up to "2" on a scale of 10 was the loudest I could take! So here's my question.. I bought an outboard attenuator made by Niles Audio, (4 inputs, one output) and put it between my CD player (Adcom GCD750) and the preamp. Turned it to about 1/3rd of the way up, and now I can use the Adcom's volume control with greater flexibility, from 1 to 5 out of a scale of 10, hence the volume changes gradually. Here's the question. What with a new piece of equipment introduced (basically a filter) would you say I have degraded the sound? I ask this, because I swear I can hear a very slight addition to "background hiss". I was told that since this attenuator is passive, that nothing would be added. Any input (pun not intended) is appreciated! Thanx! Steve With the addition of an attenuator, it makes sense that you detected a slight increase in noise, in this case a hiss which might possibly be thermal noise generated within the resistors. That should be your most significant and noticeable degredation. I would not concern myself with other nonlinearities like harmonic and intermodulation distortion. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted August 27, 2001 Share Posted August 27, 2001 Steve, The increase in hiss is called a reduced "signal to noise ratio". There is noise in the low level section of the amp. When you reduce the input level you hear this noise more becasue you have opened the volume control. Before, the higher input level overwhelmed the noise that was there all along. It's just one of the facts of life! AL K. Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted August 29, 2001 Share Posted August 29, 2001 Steve, Just to expand a bit on Al's comments, look at it this way. Your preamp and amp will produce some amount of noise - every active component, no matter how good, does. The GFP565 is a very good preamp, so it's producing a very small amount of noise (hiss, mostly). The tube amp will produce a bit more hiss and maybe some hummm - again, the Assemblage is very good, so this will be very low in level. Let's say, just for the the sake of argument, that the amount of hiss and hummm produced by your amp and preamp when the volume control is at "2" is, uh, 50dB. (I picked this out of the air just for illustrative purposes. Actual numbers don't matter - it's the concept we're talking about.) If you had the CD player turned off, and turned up the volume control on your preamp, eventually you'd be amplifying this noise enough where you'd here it. Let's say this happens at "6". Now, turn on your CD player. You can't turn it up past "2" without blasting yourself out of the room, so you can't hear the noise coming from the amp and preamp. Now, put your Niles attenuator in the circuit. Suppose you have to turn the volume level of your preamp up to "8" to get it as loud as it used to be at "2". You WILL hear the hiss, because with the CD player off, you could hear it at "6", and now you've turned it up to "8". In quiet parts of the CD, the hiss will be audible. You might try putting the Niles between the Adcom preamp and the Assemblage amp. That way, you'd be attenating the noise produced by the preamp in addition to the signal. Also, you may find that the output circuit of the preamp is more "robust" than that of the CD player, so it might sound better - you may be losing a bit of the lowest bass and some amount of bass "slam" depending upon how capable the GCD750 is of driving the variable impedence of the Niles unit. Also-er, this would allow you better control of other sources besides the CD player. Ray, always willing to give long winded complicated answers to simple questions. ------------------ Music is art Audio is engineering Quote Link to comment Share on other sites More sharing options...
steve Posted September 5, 2001 Author Share Posted September 5, 2001 Thanx guys.. Ray, I'll try the unit between the amp and preamp..this crossed my mind, but didn't think that it would make a difference..appreciate the advice and explanation was not long winded..just easy to understand. Steve Quote Link to comment Share on other sites More sharing options...
avman Posted September 5, 2001 Share Posted September 5, 2001 ray-al excellent answers! waiting to see how it goes,i've had to install a line level amp to split a ll signal to a 5ch. amp which was hooked to about a dozen 8" 2-way in ceiling speakercraft speakers for thru home audio-i get pretty innovative out in the field. really good results.avman. ------------------ 1-pair klf 30's c-7 center sony strda-777ES receiver NEW! sony playstation 2! dishnetwork model 7200 dishplayer satellite receiver/digital bitstream recorder pioneer dvd player sharp 35"tv panamax max dbs+5 surge protector/power conditioner monster cable interconnects/12 gua.speaker wire surrounds and a 'teens sub coming! KLIPSCH-So Good It Hz! Quote Link to comment Share on other sites More sharing options...
steve Posted September 8, 2001 Author Share Posted September 8, 2001 I put the attenuator between the preamp and amp, and as Ray stated..I got better low end, and no noise! I just had to adjust my Carver MKII sub, as I had it hooked to another preamp out on the Adcom unit. I'm happy now..I have some gain control! Thanx again to all who offered advice! Steve Quote Link to comment Share on other sites More sharing options...
JonM Posted September 21, 2001 Share Posted September 21, 2001 Just be aware that, depending on the value of the resistors used in the attenuator, and the capacitance of the cable from the attenuator to the power amp, you may be filtering out some of the highs a little. It's a classic, simple RC filter, and the effect may or may not be audible. To minimize it, use the shortest, lowest capacitance cables you can from the output of the attenuator. I've used a home made passive attenuator like this, and to my ears it's cleaner and quieter than an active preamp. More listenable. Maybe you don't need that Adcom preamp at all! Quote Link to comment Share on other sites More sharing options...
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