Mighty Favog Posted May 21, 2005 Share Posted May 21, 2005 Yesterday I pulled out a mothballed Carver C-1 that is in really good shape. I now remember why I stored it in the first place. The gain on the volume control comes up way too fast for me. The room measure's about 9 1/2' X 11' X 8'4". The speakers are 87db sensitive with a 150wpc amp. With the volume control facing 10:30 to 11 o'clock (off being about 7 o'clock) it just about runs me out of the room. I don't have a portable SPL meter to tell me what that come to. I found a copy of the owner's manual and they actually have a section on this "problem/preference". It says: "The line amplifier gain may be reduced as follows. Reduced 3db 910ohm for resisters R258 & R358, 4.3k on resisters #R259 and #R359. Reduced 6db 1.3k and 2.2k (respectively) Reduced 9db 1.8k and 1.5k (respectively)" I'm leaning towards the 1/4 watt 5% tolerance. Factories are 10%. I guess my question is where the volume control would be to pruduce the same gain with each one of those reductions. I would like to get the same volume at the 12 o'clock position that it now gives at 10 o'clock. Maybe there no easy answer to this other than to get a bag full of resisters and try each one. Quote Link to comment Share on other sites More sharing options...
scriven Posted May 21, 2005 Share Posted May 21, 2005 Tom, You haven't given us enough information to tell. If you can put a dummy load on the output, feed it a sine wave and measure the output at the 10 and 12 positions we could take a stab at which would be closest. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted May 21, 2005 Share Posted May 21, 2005 Hi Tom Not sure with the Carver Control but if you want to have the 12:00 close to the 10:00 position then my guess would be at least the -6db to -9db option. Its said that most people will perceive -10db decrease as a halving of loudness level. So does that seem like what you hear when you go from 12:00 to 10:00 position on the Volume control? Also I would look at the tolerance and wattage size of the resistors already there. You can't go wrong with a tighter tolerance. Seems like years ago Radio Shack sold a pack of 1% resistors in small wattage approx 1/4w if I remember correctly if these did happen to be small wattage resistors in those locations. mike Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted May 21, 2005 Author Share Posted May 21, 2005 Mark- I wish I had something to make a sine wave with. I ust don't have much equipment at my disposal. Mike- Yea, I don't want to go past 12:00, it would be the same position as my Mac C33. These look to be either 1/4 or 1/2 watt resistors. I won't know for sure until I get to RS and compare the sizes. RS doesn't have 1% tolerance like I'd want but 5% is still better than the 10% ones that are in there. I wa sgoing to get the ones for a 3db reduction but now that you gave me a little info I may go with the 6db setup. Quote Link to comment Share on other sites More sharing options...
scriven Posted May 21, 2005 Share Posted May 21, 2005 Tom, With out and solid measurements I think you are pretty much stuck with trial and error. The good news is that even at RS resistors are cheep! Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted May 21, 2005 Author Share Posted May 21, 2005 Yea, I think I'll just get all the ones they mention and make a day of it. Quote Link to comment Share on other sites More sharing options...
scriven Posted May 21, 2005 Share Posted May 21, 2005 Good idea. Try the 6 dB drop first so if you are not happy with it you will know which one to try next. Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted May 21, 2005 Author Share Posted May 21, 2005 Figures! Just got back from RS and they discontinued most resistors that are not an even thousand value. grrrrrrrrr...... I don't even know what RS is listed under in the Yellow Pages so I can see if there are any other places that sell em'. I didn't really want to mail order these but Parts Express may be getting a call from me. Quote Link to comment Share on other sites More sharing options...
LarryC Posted May 21, 2005 Share Posted May 21, 2005 ---------------- On 5/21/2005 2:28:13 PM Tom Blasing wrote: Yea, I think I'll just get all the ones they mention and make a day of it. ---------------- It's probably trial and error anyway, for which of the different level control settings sounds best. I once had an SAE amp with a quality -3, -6, -9, and -12 db click-stop control, and with K-horns, I had to set -9 or -12. The -12 sounded too subdued. I'm a little surprised that 87db speakers need that much attenuation, though the room is small. Intuitively, -6 might be good to start with (as Mark's logic also suggests). Larry Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted May 23, 2005 Author Share Posted May 23, 2005 Think it hurt to use 1/2 watt instead of 1/4? I can't find 1/4's in the value I need anywhere. (1.3k and 2.2k) Quote Link to comment Share on other sites More sharing options...
scriven Posted May 23, 2005 Share Posted May 23, 2005 Electrically there is no problem. The only possible problem using the 1/2 watt is mechanical. They are larger, including the leads. If they have to go into a PC board the leads may be too fat. Quote Link to comment Share on other sites More sharing options...
WMcD Posted May 23, 2005 Share Posted May 23, 2005 I would not go modifying the line amp unless it was absolutely necessary. Rather, why not pad the output. The Dope from Hope mini-box circuit shows how to do this with two 25k audio pots. You could probably use any value down to 10k with no problem and even use a dual pot. Gil Quote Link to comment Share on other sites More sharing options...
scriven Posted May 23, 2005 Share Posted May 23, 2005 Particularly sage advice if the new parts don't fit! Quote Link to comment Share on other sites More sharing options...
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