mace Posted January 2, 2007 Share Posted January 2, 2007 Hi, Some questions, mostly for Craig (if he needs a break from conceiving his baby) but others may benefit so I decided to post. I've seen this discussed to some extent in this thread, but I have some specific questions: 1) My Scott 299 specs claim the high level input stage for TAPE and TUNER as "Signal for Rated Output - TUNER and TAPE inputs 0.45 volts". My Sony SCD 222ES has an output of 2 Vrms (both values from the respective manuals). Assuming the Scott rating is Vrms then is the Sony 2 Vrms too much for the Scott?? Plus, I've measured the Sony output as 2.2 Vrms with a 0 dB sine wave (1 kHz) which I burnt to CD. For normal music the voltage fluctuates between 0.5 and 1.1 Vrms for CD output from player. 2) Imput Impedance of Scott - High Level Inputs is 500,000 ohms. Sony "load impedance is over 10 kohms". Is this compatible? 3) (Right now, with my KHorns, I generally listen to everything at a setting less than 2. At a setting of 2 - 9 o'clock- I get about 85-95 dB peaks at listening position, classical and rock). My loudness switch is always set to off and tone controls flat. Will lowering the splitter tubes voltage allow more range of low level output? I was advised several years ago when I purchased the amps to set these to 0.275 VDC, or as low as 0.25 VDC (and the tubes will love me for it!). Question: Does the 0.25 vs. 0.275 affect the sound/tonality in any way? Does the 0.25 setting allow for less gain on the loudness knob? 4) See attached graph of volts out of back of amp (with 8 Ohm resistors hooked up to speaker outputs, voltage measured accross resistors). Input signal was 0 dB 1kHz sine wave from CD player. Can the slope of the voltage output from 0-4 on the volume knob be lowered easily? 5) I've installed cheapo 6 dB attenuators (as recommended by Craig in an email... great tip!) from PartsExpress. This will halve the voltage of the CD player signal going to amp. I went for the cheapo's instead of the $60/pair ones just to check out the concept. Does anyone know if there is a quality difference between the cheapo's and the harrison labs models? I don't want to start a great debate of zip cord vs. $200/foot wire or anything, just wondering if anyone has any throughts based on experience with these attenuators. Thanks much, Mace Quote Link to comment Share on other sites More sharing options...
jcmusic Posted January 2, 2007 Share Posted January 2, 2007 Mace setting the voltage down to 0.25 will not have any effect on the volume or gain at the knob, however if you want some range of travel with the gain control or volume knob; try changing the imput tubes from 12AX7's to a 5751. This will lower the gain and thus allowing more travel at the knob. This is exactly what I did for my 299 awhile back, and everything is peachy. Jay Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 3, 2007 Share Posted January 3, 2007 Hi, Some questions, mostly for Craig (if he needs a break from conceiving his baby) but others may benefit so I decided to post. I've seen this discussed to some extent in this thread, but I have some specific questions: 1) My Scott 299 specs claim the high level input stage for TAPE and TUNER as "Signal for Rated Output - TUNER and TAPE inputs 0.45 volts". My Sony SCD 222ES has an output of 2 Vrms (both values from the respective manuals). Assuming the Scott rating is Vrms then is the Sony 2 Vrms too much for the Scott?? Plus, I've measured the Sony output as 2.2 Vrms with a 0 dB sine wave (1 kHz) which I burnt to CD. For normal music the voltage fluctuates between 0.5 and 1.1 Vrms for CD output from player. 2) Imput Impedance of Scott - High Level Inputs is 500,000 ohms. Sony "load impedance is over 10 kohms". Is this compatible? 3) (Right now, with my KHorns, I generally listen to everything at a setting less than 2. At a setting of 2 - 9 o'clock- I get about 85-95 dB peaks at listening position, classical and rock). My loudness switch is always set to off and tone controls flat. Will lowering the splitter tubes voltage allow more range of low level output? I was advised several years ago when I purchased the amps to set these to 0.275 VDC, or as low as 0.25 VDC (and the tubes will love me for it!). Question: Does the 0.25 vs. 0.275 affect the sound/tonality in any way? Does the 0.25 setting allow for less gain on the loudness knob? 4) See attached graph of volts out of back of amp (with 8 Ohm resistors hooked up to speaker outputs, voltage measured accross resistors). Input signal was 0 dB 1kHz sine wave from CD player. Can the slope of the voltage output from 0-4 on the volume knob be lowered easily? 5) I've installed cheapo 6 dB attenuators (as recommended by Craig in an email... great tip!) from PartsExpress. This will halve the voltage of the CD player signal going to amp. I went for the cheapo's instead of the $60/pair ones just to check out the concept. Does anyone know if there is a quality difference between the cheapo's and the harrison labs models? I don't want to start a great debate of zip cord vs. $200/foot wire or anything, just wondering if anyone has any throughts based on experience with these attenuators. Thanks much, Mace Man look at the awesome low fluctuation out of those channels. You have a nice example! I don't remember it exactly now. So do you hear any degradation with the -6db attenuator over them not installed? Technically speaking you have a slight mismatch from the voltage source of the CD player but the attenuator should actually take care of it pretty well. But no free lunches exist here. Just like suggested by canyonman the 5751 can indeed knock some of the gain down but it will not do it by a huge margin and absolutely raises the distortion levels of the amp by some degree just like the attenuator will create some distortion in the source entering the amp. I say if it sounds good to you then it is good and forget about it. You have had the amp for a very long time so I'd say it must sound good to you[] By the way the specs your reading can be off by some margin? no printed specs or schematic exists for the second addition 299. Its basically half 299 and half 299B. My modifications make it nearly a 299B with the bias mod and a few other tweaks you have. By the way the bias has absolutely nothing to do with this issue. If your not turning the amp up you have no benefit to biasing it above the .250 I suggest in the manual. This has to do with how hard the output tubes are working at idle and low volume and has nothing to do with gain. When I owned and ran a 299 same model as yours I built my own in-line attenuators and I thought it worked great to knock just a bit of the extra gain from my Sony that I did not need. Craig Quote Link to comment Share on other sites More sharing options...
mace Posted January 3, 2007 Author Share Posted January 3, 2007 Hi, Thanks for the insights. I'll give these attenuators a try. My initial impressions is that they muddy things up a bit, but I really haven't had a chance to listen without interuption for more than 3-5 minutes. One thing I have noticed with source material is that lower level source material seems to sound better, more open, less harsh.. this is at about 90 dB listening level. I love the Who album Who's Better, Who's Next. At high volumes, around 100 dB, it is just wonderful. I've noticed that I really have to turn the Scott up a bit, like to 5 on the dial. To get that same SPL from newer material which has a noticably higher line level I am around 2-4 on the amp and the sound isn't as smooth as with the Who. Perhaps it is just how it is recorded but I've noticed this trend in general with low line level source material... perhaps it has to do with voltage of the CD signal. When I get some time I'll check out these attenuators. Mace Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 4, 2007 Share Posted January 4, 2007 Mace, I must have been really tired when I wrote that man did I butcher some spelling.......and forget to use spell check One more thing if one opts to use the 5751 route or any modification inside the amp to knock some gain down you will also knock down the combined effective gain available when playing LP's! Which is why I recommend the attenuator route at the source. LP's in my opinion is the real reason to own a 299A it happens to have one of the sweetest phono sections of the vintage integrated world. It's no mistake that LP's were the source King of the era all other available sources of the day were pretty nasty unless big $ were spent. The best method for CD's would be to have a variable output control on the CD player. Try the front headphone jack as the source also I believe the 222ES has one with a volume control on the front. You can pickup the adapter to go from standard headphone jack to RCA output at Radio Shack. Never ending tweaking to find the best solution. Craig Quote Link to comment Share on other sites More sharing options...
mace Posted January 4, 2007 Author Share Posted January 4, 2007 I don't use LP's and thus maybe the 5751 route would be an option. How do these tubes affect the sound/tone? My CD player does have a variable headphone jack but that wouldn't work so well with my set-up. Maybe I should just get a better matched pre-amp and use my B&K power amp... which is the route I was going before I got the KHorns! Thanks much, Mace Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 5, 2007 Share Posted January 5, 2007 You'll have to tell me. I've never used them since I did not want to lose over all gain because I used the rig mostly for LP's. I did the inline attenuators for CD's. Sounded fine to me. Give them a whirl and see what you think. They surely won't hurt a thing. Craig 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.