Mike Lindsey Posted September 10, 2002 Share Posted September 10, 2002 Well, for some reason, the left channel just doesn't sound as good as the right channel. Aside from the right channel being louder, it is also crisper, clearer and more detailed. I decided to use my Stereophile Test CD #2 and compare both channels individually using the test tones from 250hz - 20Khz. The right channel was about 2 - 4db louder thruout, and cleaner to boot. I'm not sure what's going on here but I'm pretty sure it's the Scott and not the speakers. Even though I don't have a balance control on the Denon 4800 (why the hell is that?), when I play back music, the voices are dead-on center and the left channel is as clear as the right. Can someone give me some ideas what the problem may be? BTW, my ALK's should be here tomorrow or Thursday... Mike Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 After playing around with it, it seems that it is more pronounced during phono playback versus CD. I also tried moving the volume around to the left (about -1 on the dial) and that seems to have centered it again. If I lock it in here, am I doing anything to the signal (good or bad)? Thanks, Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Well this is a bummer !!! I still say its volume pot and is being pronounced by your Lascalas being 104db. I have never found a vintage amp that didn't have some channel imbalance especially at lower output levels. But lets start with the Treble and Bass controls. Turn them all in there complete revolutions both ways and make sure both channels are lined up. What I do is use the set screw hole as a guide turn the bass and treble for one channel all the way right and line the screw hole up with the -1 or +1 Db they should land equal on the 1's. I just did this to Danocasters amp and found both channels had been moved alot. I can't remember if I ever took yours off I don't think so. You also for the heck of it can trade the 12AX7s around from each other try the 2 on the right side of the amp when looking at it from the front. also the 6U8A can be done safely. The only ones that shouldn't be moved are the 7189s. The 12AX7's just need to be kept in the pairs to save there match. Does the imbalance seem to be the same when using phono or does it seem less extreme ?? Also I find that moving my head 2" when listening to a album can center the vocals with a good imaging tube amp. Are you sure your sitting dead center. SS amps don't image like this !! At least none that I have ever heard. I actually have a measured mark to line up dead center in my Shop/listeningroom if I'm off center at all so are the vocals. This is actually more pronounces having the speakers firing dead at you like we both have are placed. How are you measuring these imbalances are you using the stereo switch ?? This is the proper way to do it turn the selector to the left for mono and than left channel and right if your using the balance pot while sending a stereo signal the channels will never bo the same there getting a different signal in stereo. Doing it this way set the balance pot so the same DB is coming out of each channel and then compare the sound qualty of both channels. This will narrow down if there is a problem with the amp or if it is indeed just the controls. Even then it could be that volume pot not allowing a clear signal thru. If this is the case we are going to have to have Mark layout a mod to except a newer volume pot. This kind of modification to the curcuit is beyond my abilities without a audio engineer to redesign the curcuit. Let me know what you find out Craig Quote Link to comment Share on other sites More sharing options...
edwardre Posted September 10, 2002 Share Posted September 10, 2002 Mike, did you swap speaker leads and R/L inputs to isolate the problem to speakers/Denon/Scott? ------------------ Ed Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Mike, You moved what ?? to -1 db ?? Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 I moved the balance to -1 (around to the left)... Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Mike, Check the treble and bass controls as I discribed above and get back to me. Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Also I don't think you can lock the Balance pot in place in anything other then dead center it is half mooned shaped. The bass and treble controls are adjustable like your talking about doing. Craig Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 Well, the bass and treble are exactly like you say for both channels. They line up on the 1's in either direction. As for the balance knob, it is identical to the volume knob. I turned it to 1 on the left, loosened the screw, turned it so that it was pointing straight up and then tightened the screw. The vocals are now coming from the center and it seems to be in balance. However, the left channel does not sound as good as the right channel. I may try swapping the speaker wires and I may even try swapping the speakers, just to make sure it's not the speaker... Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Mike, So your saying that if you take the Balance nob off the amp the shaft sticking out is completely round ?? If it is its the first Scott I've ever seen that way. Craig Just checked 5 amps here and none of them have a round shaft all are half moon shaped. That is kind of strange. This message has been edited by NOS440 on 09-10-2002 at 04:23 PM Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 I don't have to take the knob off to adjust it. All I'm saying is the knob itself looks like the volume knob. I never removed it however. All I did was adjust the balance (moved it to the left) until I felt both speakers were balanced. I then loosened the set-screw and turned the knob back to the right until it was centered on 0, and then tightened the set-screw again. It is now balanced but like I said, the right channel is clearer and crisper... Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Mike, Take the nob off and see what I mean no matter what you do as far as adjusting it it still goes back to center period mark there is no adjusting the Balance pot the only pots that can be adjusted are the Treble and Bass. Unless of coarse its different than every Scott I have worked on or own. Craig Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 Well... you were right. It's a half moon. Not sure what's going on there but all of a sudden it seems balanced again. I'm losing my mind here. Will see what happens when I put the ALK's in there tomorrow. I must say it sounds really good at the moment... especially the phono. I'm still looking for a relative bargain on some used Mullard 12AX7's and hope to hear an improvement when I get a set. Will keep you posted... Mike Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 10, 2002 Share Posted September 10, 2002 Mike, Had the amp warmed up completely ?? Another thing you might want to try is pickup some DeoXit and give the Pots a good shot every now and then. You have to do this from under the chassis. There is a small slot that you can shoot into where the solder lugs are on the pots. Craig Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted September 10, 2002 Author Share Posted September 10, 2002 Well... you were right. It's a half moon. Not sure what's going on there but all of a sudden it seems balanced again. I'm losing my mind here. Will see what happens when I put the ALK's in there tomorrow. I must say it sounds really good at the moment... especially the phono. I'm still looking for a relative bargain on some used Mullard 12AX7's and hope to hear an improvement when I get a set. Will keep you posted... Mike Quote Link to comment Share on other sites More sharing options...
Kudret Posted September 21, 2002 Share Posted September 21, 2002 Mike, did you ever found out what was wrong with your amp? I am also having a balance problem with my 299A. I noticed that the sound-stage is always on the left - close to the left speaker. Then I did some testing with the STEREO BALANCE knob. When I turn the knob all the way left to Channel A, the right speaker goes silent (as expected) but when I turn the knob all the way right to Channel B, the left speaker does not go silent - there is a considerable amount of sound coming from the left speaker. This is probably the reason that all the vocals are coming from the left side. Does anybody have any suggestions? Thank you. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 21, 2002 Share Posted September 21, 2002 Kudret, Try this center the Balance control. Then turn the volume to say 3 turn the stereo switch to mono channel A and then B (to the left from stereo) notice the volume imbalance difference (If you happen to have a DB meter actually test it). Then turn it to 4 and then 5 and so on and test it and see if the amount of imbalance stays the same, lessons or changes in anyway. If it does change its the volume pot. Note what I mean is that if there's a 4 db difference at 3 and only 1 at 6 on the volume dial as the resistance varies in the pot it is correcting at louder volumes. They all have some imbalance by design all the pots used in any vintage amp are + - 20% and this worsens with usage and age. You might get lucky and just pickup a can of deoXit and reclean it and it might help. Let me know Craig This message has been edited by NOS440 on 09-21-2002 at 10:03 PM Quote Link to comment Share on other sites More sharing options...
Kudret Posted September 21, 2002 Share Posted September 21, 2002 Thanks Craig, I will give it a try and let you know. kudret Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.