Convert cartridge output voltage to db gain
Kal, please note the word OR between 1.25 mV cartridge output and 80 db gain phono preamp in my previous post. Darkmoebius and Al, actually that link shows that my integrated amp is a VAC Avatar Super, NOT the SE version. Your specs are correct for the SE version, the Super is different. The only spec I can find on the Super is the 80 wpc output in ultra-liniear (no triode option). The Super does use different preamp tubes, different driver tubes, and different power tubes. So I don't think I can use the SE gain specs. My Walker Signature phono stage specs the same as the Reference, and is set for the max gain of 66 db. According to the calculator that Darkmoebius provided, my 0.24 mV cartridge with 66 db of gain outputs a signal of 0.48 V. That would explain the difference in my volume control knob positioning, since my CDP output is 2.5 V, over 5 times the output of the phono stage. Both signals pass through the same line stage and power stage, so I discounted the gain of the integrated amp. Does this help clarify things? Again, thanks for the help. Cheers, John |
Yeah, not a lot you can do about that, except as you've already concluded. 1.25mV cart or up, it seems. BTW, which cart are you currently using? And, I forgot say it before, but you've got an awesome system. Bet it's musical as all get-out! Here's the Avatar Super's manual(.pdf), which has the spec sheet on the 3rd to last page Have you ever had the chance to compare the Avatar Super's built in MM phono section with anything else? Obviously, at 42dB gain, it doesn't have enough for your current cart. |
Yes, there don't seem to be any published specs on the gain of the line stage or power amp section of the Avatar Super, but the manual does indicate, as with the SE, that "attenuation precedes line stage" and consequently there is no practical limit on input voltage. And if 2.5V from the cdp doesn't overload anything, 480mv from the phono stage certainly won't. BTW, John, if I may I thought I'd point out that Hdm, to whom you've addressed a couple of comments, is not Kal. Kal is Kr4. Best regards, -- Al |
Al, you are right, I misread Hdm's first reply when he said "I'm with Kal above", I read "I am Kal from above". I thought maybe Kal had two monikers. My mistake, I apologize to Kr4 and Hdm. No, 2.5V does not overload the VAC at all. Darkmoebius, thank you for the compliment on my system and yes it does sound pretty good, even after the downsizing of '08. Thanks also for the VAC manual link, but I do have the VAC manual, I just misplaced the Walker manual. The specs in the VAC Avatar Super manual do not give the line and amp section gain levels like the Avatar SE did. FWIW, the VAC replaced a stock ARC REF 3 preamp and a highly modified BAT VK-75SE by Bob Backert of RHB Dezigns running fully balanced. My cartridge is the low output version of the ZYX UNIverse S-SB, same as listed in my system at AA. I have tried the built in MM phono stage of the VAC using a cheap SUT with the same ZYX cartridge. The sound was pretty good, but not in the same league as the Walker phono stage. I would not expect the inboard phono stage of a $6500 integrated amp to beat a $6650 outboard phono stage though. I know, to be fair I probably should have tried the VAC with a better SUT, but I was nervous about spending big $$$ on a SUT without hearing it in my system first. Thanks again for that calculator, I saved it in my favorites. Thanks for all of your help too Al, you bring a wealth of knowledge to these forums that is very refreshing. I think I'll try to give Lloyd a phone call tommorrow. I still think I'm best to: a)check the DC offset in the Walker (no coupling caps, Lloyd believes the best cap is no cap). If that doesn't help then... b)change the line stage tubes in the VAC. Hopefully that will solve my problem, if not, then I will probably proceed to looking at higher output cartridges. Happy Holidays, John |
