mace Posted November 17, 2003 Share Posted November 17, 2003 Hi, On some CD's I can hear distortion during certain passages, which is very repeatable. To my ears, it sounds like pre-amp distortion. I have ripped these passages to my computer (as AIFF) and taken a look at the waveform and noticed that the waveforms are very close to zero dB (the Audiophile test CD calibrated -20 dBFS signal gives me -19.8 dBFS with my computer program, zero dB = 2.2 V). This distortion can be heard on music ranging from folk music vocals to heavy metal guitars - what the passages have in common is the near zero dB line level. My question: Is the line level of the SACD (2.2 V) too much for the "line in" on the Scott 299A? Do I have to step down the line level by 1 or 2 db? I've tried different 12AX7 pre-amp tubes and the distortion is still there. I don't think it is a power amp section problem since the distortion occurs at low power levels (volume dial at 8 o'clock). Any help or things to try would be appreciated. Regards, Mace Quote Link to comment Share on other sites More sharing options...
djk Posted November 18, 2003 Share Posted November 18, 2003 On 99.9% of the gear on the market the signal goes from the input jack ~ selector switch ~ volume control ~ balance control ~ tone/line amp ~ main amplifier. IOW when you turn the volume down the signal fed to the line stage gets smaller too. A Marantz 7 does not follow this flow, but I have not heard it overload. Quote Link to comment Share on other sites More sharing options...
Deang Posted November 18, 2003 Share Posted November 18, 2003 djk -- I guess you don't answer PMs or email? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 18, 2003 Share Posted November 18, 2003 Mark, I'm either confused or you are I believe the volume and balance control is after the Preamp section and feeds the Phase splitter on all Scott amps. Mace, Is this something your just now finding issue with ? I would take it yes since you have had the amp for a long time with out a word about this. So maybe something is going wrong here. As always your welcome to send it in for a check up at no charge . But first check the amp with another high level source to ensure its not a CD player problem. Craig Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted November 18, 2003 Share Posted November 18, 2003 Well, I don't know... I've always had the same problems with music off the computer. Same stuff Quote Link to comment Share on other sites More sharing options...
mace Posted November 18, 2003 Author Share Posted November 18, 2003 Hi All, I've got some experimenting to do with different CD sources, input selection, swapping speakers etc. I first noticed the problem several months ago but I just haven't had time to sit down and trouble shoot since I've been travelling so much. However, looking at the specs for the Scott 299A and the Sony SACD: SACD Player Output: 2 Vrms @ 50 kOhm Load Impedence: >10 kOhm Scott 299A Input: 500 kOhm input impedence, 0.45 V. I don't know the difference between load impedence and output impedence. Are these specs compatible? Thanks, Mace Quote Link to comment Share on other sites More sharing options...
Tillerman Posted November 22, 2003 Share Posted November 22, 2003 Hi Mace, I find this an interesting topic. I also have thought I heard distortion from my CD player through my vintage preamp. I wound up reducing the CDP output with a pair of Harrison Labs 12dB in line attenuators between the CDP and preamp. Inexpensive experiment that I still use, as I found the distortion (if there was any) to have disappeared and I have more "control range" with my preamp's volume control as well. Scott Quote Link to comment Share on other sites More sharing options...
mace Posted January 15, 2004 Author Share Posted January 15, 2004 Thanks for the line reduction tip... I may look into that at some point (along with getting a bottle of De-oxit to clean the contacts on this old beast). However, I must update. I got some headphones for Christmas. I had never thought of listening to these "problem" CD's with headphones before (duh!). Well, guess what... the distortion I was hearing seems to be on the CD. I hang my head in shame. I've read how tubes and horns will reveal flaws in the source, I never realized to what extent (or course, headphones help hear flaws too, I suppose, but they just don't pound your chest the in the same fashion as Cornwalls). So, I'm back to thinking my SACD/Scott combo is fine and my source material isn't. I may start another thread and see if anyone else has these CD's and ask others opinions on the distortion I'm hearing. Or perhaps I'll post a short AIFF of the passage for others to play with. Anyway, I still may look at some line level attenuation between CD and Scott, because the "increased control range" would suit me since I do most listening with family around (i.e. at about 8 o'clock on the Scott). Mace Quote Link to comment Share on other sites More sharing options...
mace Posted January 15, 2004 Author Share Posted January 15, 2004 ---------------- On 11/19/2003 2:08:49 PM Ryan C. Inman wrote: Mace, You shouldn't have any problem using a CD player with a 2V output. Mine also has a 2V output, and I have not experienced any problems with overloading. The Scott's input impedance is certainly high enough for your CD player, so that is not a problem either. Was your 299 rebuilt? You could possibly have some bad cathode bypass capacitors in the line stage preamp. If they fail, distortion increases. Are you using a line-level input, such as extra or tape monitor? If the amplifier is not at fault, then your CD player probably is. Instead of using 12AX7 tubes in the line stage, try a tube with lower gain, such as a 5751, 7025, or 12AT7. The 5751's work very well. Best Regards, Ryan ---------------- Hi Ryan, My CD player is rated at 2.0 V but I've measured it as 2.2 V out (see my method outlined above). Anyway, I've since determined that my source material contains this distortion I've been hearing, so I think the amp is OK. Thanks, Mace Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 15, 2004 Share Posted January 15, 2004 Mace, Glad your CD's are the problem and not the Scott I hear distortion on many old 70's and 80's music that was pourly captured on the new wonder format ! I just don't listen to those CD's and spin the vinyl ! I wondered what ever came of your problem. Craig Quote Link to comment Share on other sites More sharing options...
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