Your cartridge output is only 0.42 milivolts. If you are using the 12UA7 tube, then perhaps you are not getting enough gain. Switch out the supplied 12UA7 tube with the supplied 12AX7 tube to get an additional 15 dbs of gain. That will allow you to turn down the volumn knob a bit.
In the future, if you buy a lower output cartridge, you might be in the same situation with not enough gain so keep this gain to cartridge output number in the back of your head.
Regards, |
Your preamp looks like its just a line stage. If you have a m/c cartridge you need additional gain from a pre-preamp. Loading that you mentioned is different...You can get a moving magnet cartridge or the pre/pre (Wyetech I saw makes one).
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Hi Gary, first, do you have the interconnects plugged into your MC input on your Rogers PA-1A? If not, then remove them from the MM inputs and put them on the MC inputs.
Second, you can do as griiffithds suggest, and use all 12AX7's which should provide 15 dB more gain.
If this still doesn't provide enough gain, have the tubes checked out, make sure they are reading okay.
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Agree with griffithds and jmcgrogan2, check to make sure you're using the right input and switch out the tubes. I think that using the 12AX7 tubes as suggested above will help, as 50 db of gain from the 12AU7s might not be enough for your cartridge. |
How much gain does the Rogers phono stage put out? If I understand from above the 12AU7 puts out 50db gain, but switching to the 12AX7 results in 65db gain...correct? If so, 65db should be plenty of gain to drive the .4mv output cartridge.
Absolutely no need to consider switching to a moving magnet! You've got a simple wiring error or a bad tube in all likelihood.
And for god's sake, never any need to turn the volume all the way up. If you pass 2:00 and it's not plenty loud, usually something is setup incorrectly.
Cheers,
Spencer |
Thanks guys- I bought the Rogers used and the guy sent a mishmosh of sovtek tubes so I guess they are no good-
I am going to order a new set of 12ax7- So the question is which one do you guys rec. I get- thanks again for all the help!!! |
65dB = 1778
0.42mV x 1778 = 0.75V
Still low - needs about 8.5dB more to get to standard 2V. Am I missing something?
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When I spoke to the guys at Charisma they rec. 61db for the cart?? |
According to the KAB gain calculator, 58 dB is optimum gain for 0.4 mV cartridge. https://www.kabusa.com/pregain.htmKeep in mind that fluffers Wytech Ruby preamp also has 12 dB of gain. So if he has it connected correctly, and all tubes are up to spec, he should have PLENTY of gain with his 65 dB of gain using 12AX7's in his Rogers phono preamp, and the 12 additional dB of gain in his Wytech preamp. |
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Guys- You are the best- thanks- Yes I checked this morning- Preamp phono out into MC of Rogers Phono Pre-ground connected- Front panel turned to MC not MM-SO I Guess it must be the tubes-
so which 12AX7 do you guys rec. me getting? |
Wait--phono OUT from preamp? You mean you're running the TT into the MC input of the phono stage, and the phono stage into an input of the preamp, right? |
fluffers,
If you have the Preamp outs connected to your Phono Pre, the Houston, we have a problem!
Turntable cable goes to the phono pre 'in'. The phono pre 'out' goes to the Preamp phono 'in'. Preamp 'out' goes to the amp.
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griffithds=sorry was not paying attention when i typed yes that is the way it is hooked up sorry about the typos-
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It sounds like you have narrowed it down to bad tubes, since all connections seem to be correct.
Asking for tube recommendations can be tricky, as we don't know your budget or personal tastes.
Choosing tubes can be subjective, just like choosing cables.
NOS can be pricey, but worth it to some. Some like the warmer sound of Mullards/Brimars, etc., while others like more revealing tubes like Amperex/Siemens, etc.
Try to find a reputable dealer like Brent Jesse if buying NOS tubes.
Personally, I like Amperex NOS tubes, and if going with current production tubes, I like the Psvane tubes. Obviously, YMMV.
Let us know how you make out with some fresh tubes.
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+1 @jmcgrogan2
If you have a buddy with tube tester,or a local dealer who can test your tubes it would be good to confirm that's the problem. However, most local dealers will have little tube selection. Cheers,
Spencer |
Ok- after playing around I think it is the 6gh8 tube that is bad- any rec. on which 6gh8 tube is the best- thks
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Bad news: Sorry, I have no experience with the 6GH8 tube.
Good news: However, a quick web search shows that they appear to be inexpensive to replace. Lots cheaper than the 12AU7 or 12AX7!
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UPDATE- it was the 6gh8 tubes- funny I just got them NOS MULLARDS- switched to some sylvania's and BAM there was the volume- thanks for all the help!!
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Congrats! Glad to hear things worked out!
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