Kudret Posted March 23, 2003 Share Posted March 23, 2003 When using the phono input on my 299B, there is some low level hiss that increases as I raise the volume. I have unplugged the turntable, but the hiss remains. I have also replaced the 7189 and 6BL8 tubes, but still the same. I've recently replaced the cartridge on my TT to Shure V15-VxMR and I find myself turning the volume up to 12 O'clock position to get normal volume. At this level hiss becomes unacceptably high. One possibility would be to get a high output cartridge so that I wouldn't have to turn the volume so high, but I would prefer to solve the problem. Any idea what might be the causing this, and possible fix for this issue? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 23, 2003 Share Posted March 23, 2003 Kudret, What if anything have you done to the amp so far ? What phono input are you using. You should use Mag 2 Low input with the V15. But still the hiss should just begin at 12:00 and not get real bad till 2:00 or 3:00 if all is well with the phono section. Is the his equal out of both channels ? Have you tried different 12AX7's in the phono section ? Which brand are you using ? These are the 2 on the far left when looking at the front of the amp. 95% of the Scott amp I have done (some 30 or so) the hiss produced with the stock components intact isn't audible until the volume knob reaches 5 or 6 which would be over 100db playing music with a V15 cartridge. Craig Quote Link to comment Share on other sites More sharing options...
Kudret Posted March 23, 2003 Author Share Posted March 23, 2003 Craig, thank you for your suggestions. As you suggested I tried Mag 2 Low, and I don't have to turn the volume as high now. I can definitely live with this level of audible hiss at moderate listening levels, but of course it gets louder as I turn the volume up (5-6 or louder). Is it possible to reduce it any further? So far, I've replaced all the coupling capacitors, two PS filter capacitors and the selenium bridge (also upped the 10ohms 2W resistor after the silicone bridge to 33ohms 5W). All the voltages underneath seem to be right on and I biased it to 55mA. I am using Telefunken 12AX7s and 6BL8s, and Mullard 7189s. This is my favorite amp among the three scotts that I own and I might go all the way with better caps on this one. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 23, 2003 Share Posted March 23, 2003 Kudret, If the 12AX7 have been eliminated as the culprit then changing out all the resistors on the 2 phono section tubes can quiet things down nicely. When I do this I even strip insulation off hookup wire and use it to insulate the resistor leads (I'm anal that way). I have found Kiwame resistors do a real nice job at this and have all the values needed for you to do it. This is a pain in the butt to do but if its real noisy then well worth the effort. Email me and we can set something up if you want them. But definitely exhaust all other options before yanking them great Allen Brady resistors in place now also test all of these for there stated value and variations from each other channel to channel. I do want to caution you that the Kiwame's do take some time to settle in but once they do it really sounds about the same as the originals and is quieter you will never get the phono section dead quiet with are speakers above about 1:00 on the volume dial but my 299B is usable at full volume without objectionable noise (If your ears can stand the DB LOL !! ) Also what type of cap did you put on the Phono section 12AX7 if you didn't replace this then the existing ceramic caps is a real noise producer do this first then see but usually this cap will produce hum more then hiss. The .022 Russian film and foils do nicely here even a orange drop can make a big improvement. Auricap will do a great job also ! Craig PS, They are the best Scott integrated amp made except maybe the 272 or 296 which I havn't heard yet. If you want I will give you a great deal on all the Russians caps to put in and Kiwame's to really make that amp sing !! Just so you can join the 299B club LOL !!!! This is a offer that hurts because the availability of these caps are a thing of the past. I have been excepted as a factory direct Auricap dealer because of this ! Now all I need is $1000 bucks for my first order Quote Link to comment Share on other sites More sharing options...
Kudret Posted March 23, 2003 Author Share Posted March 23, 2003 Thanks again Craig. >>If you want I will give you a great deal on all the Russians caps to put in and Kiwame's to really make that amp sing !!<< I am definetely interested in some Russian capacitors and Kiwame resistors. Probably we should take this offline - I am sending you an email. Quote Link to comment Share on other sites More sharing options...
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