derrickdj1 Posted January 28, 2017 Share Posted January 28, 2017 Schu started a thread about preamp tubes and which ones where the best for his amp. That thread got me thinking about what are the V1-V4 slots on the preamp. I also have V1-V4 on the power tubes. The Vi preamp slot is the first tube to influence the signal and dictates the overall tone. The other tubes serve a function but, are not quite as important as V1 for the overall tonal quality of the amp. V1 push the first stage and will influence how and where the amp will distort. It's better to have the amp distort at the power tubes. A lower voltage gain tube will give more clean headroom but, push the power tubes a bit harder. The distortion from the power tubes delivers the pleasant harmonic that people talk about. I am new to this game but, if the above is correct, play with different V1 tubes is the most beneficial with tube rolling? I wish I had a high quality recording device to try my 3 different 12AX7 on the same songs a see if I can hear a difference. Maybe, I don't need three different 12AX7's and should of brought a lower gain tube like the 12AT7? On my amp, V1 and V4 are the 12AX7, do these have to match? Quote Link to comment Share on other sites More sharing options...
Schu Posted January 28, 2017 Share Posted January 28, 2017 I dont match my follower and output on the pre... I did extensive critical listen sessions swapping tubes in and out of both slots. Once I got in the ball park, I switched to the output and swapped tubes in/out until satisfied, then I started with the follower and finalized that slot. after that I went back to the output and rechecked what I had heard before... since then I have been very happy. surely the follower is MUCH LESS critical but it did change as I changed tubes. 1 Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 28, 2017 Share Posted January 28, 2017 2 hours ago, derrickdj1 said: Schu started a thread about preamp tubes and which ones where the best for his amp. That thread got me thinking about what are the V1-V4 slots on the preamp. I also have V1-V4 on the power tubes. The Vi preamp slot is the first tube to influence the signal and dictates the overall tone. The other tubes serve a function but, are not quite as important as V1 for the overall tonal quality of the amp. V1 push the first stage and will influence how and where the amp will distort. It's better to have the amp distort at the power tubes. A lower voltage gain tube will give more clean headroom but, push the power tubes a bit harder. The distortion from the power tubes delivers the pleasant harmonic that people talk about. I am new to this game but, if the above is correct, play with different V1 tubes is the most beneficial with tube rolling? I wish I had a high quality recording device to try my 3 different 12AX7 on the same songs a see if I can hear a difference. Maybe, I don't need three different 12AX7's and should of brought a lower gain tube like the 12AT7? On my amp, V1 and V4 are the 12AX7, do these have to match? Okay, first thing is why do you want to roll the AF/Pre-amp/driver tubes? Is there anything objectionable in the sound of the amp that you think may be corrected with a different brand but same type of tube? If you do still have and use newer Chinese front end tubes, rolling brands might not be a bad idea... I'm not sure which exact types of tubes go in the pre-amp sections V1-V4...but if the socket calls for a 12AX7, I would use a 12AX7. Same with the other sockets, if it print near the sockets mentions 12AU7 or 12AT7, use those types. I don't know if swapping a higher gain 12AX7 for a lower gain 12AT7 would do any harm, but the circuit for that tube is wired with the proper Rs and Cs for a 12AX7. Download the Duncan amps tube sheet data locator. You can look at the data and the differences (some slight) in tubes like 12AX7, 12AU7, 12AT7, 12AZ7, 12AV7. There is lower gain versions of 12AX7...5751, or 7025. 1 Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted January 29, 2017 Author Share Posted January 29, 2017 8 hours ago, mike stehr said: Okay, first thing is why do you want to roll the AF/Pre-amp/driver tubes? Is there anything objectionable in the sound of the amp that you think may be corrected with a different brand but same type of tube? If you do still have and use newer Chinese front end tubes, rolling brands might not be a bad idea... I'm not sure which exact types of tubes go in the pre-amp sections V1-V4...but if the socket calls for a 12AX7, I would use a 12AX7. Same with the other sockets, if it print near the sockets mentions 12AU7 or 12AT7, use those types. I don't know if swapping a higher gain 12AX7 for a lower gain 12AT7 would do any harm, but the circuit for that tube is wired with the proper Rs and Cs for a 12AX7. Download the Duncan amps tube sheet data locator. You can look at the data and the differences (some slight) in tubes like 12AX7, 12AU7, 12AT7, 12AZ7, 12AV7. There is lower gain versions of 12AX7...5751, or 7025. I'm just curious as to what exactly each slot is doing. My V1 and V4 are both 12AX7 but, from what I read they are each doing a different function. V4 is the phase inverter where as, V1 is the first amplification stage. This is why I asked if they need to match. There are some slight differences in the Telefunken, Tung-Sol and Electro Harmonix 12AX7's but, a more dramatic change may come from a 12AT7. Just trying to learn a few more things. I've not found anything saying the power tubes V1-V4 serve different functions. I have noticed the 12 AU 7 is the dimmest of the preamp tubes. The 12 UA 7 is only 20% of the gain of a 12 AX 7. It is my understanding that the preamp V2 and V3 are also doing different things. Quote Link to comment Share on other sites More sharing options...
jimjimbo Posted January 29, 2017 Share Posted January 29, 2017 Listen to Mike Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 29, 2017 Share Posted January 29, 2017 1 hour ago, derrickdj1 said: I'm just curious as to what exactly each slot is doing. I could tell you in about 30 seconds if there was a online schematic floating around or a manual. And I have searched a bit... My best guesstimate is the 12AX7 are the AF/pre-amp tubes, and the 12AU7 are for phase inversion. 1 Quote Link to comment Share on other sites More sharing options...
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