I'm new to tubes. I recently purchased a used Herron VTSP 3a ro2 pre amp, which has a High and Low gain option. It's paired with a NAD M22 v2 power amp, which has High, Mid, and Low settings. I futzed with the settings for several days and finally settled on High for the Herron and Low for the NAD. This combination makes my Tannoy DC8 Ti speakers really sing.
General question about tube preamps and gain
I have a (possibly moronic) question unrelated to my previous thread. This is a general question about tubes and gain.
So say you buy a tube preamp and it sounds clean and clear. You decide you want that dark, syrupy sound (classic tube sound?). So you buy tubes that impart this sound on the signal and install them.
Now installed, you notice that the more you turn the preamp volume up, the more the tubes impart that sound on the signal. But you can’t play it loud.
So could you, theoretically, put attenuators (lets say -10db) between said preamp and the power amp to lower the output signal which you’d then turn the volume up and drive the tubes a little harder to impart more of the tube’s sound at lower levels?
I hope this makes sense. It does in my head but that don’t mean much.
So say you buy a tube preamp and it sounds clean and clear. You decide you want that dark, syrupy sound (classic tube sound?). So you buy tubes that impart this sound on the signal and install them.
Now installed, you notice that the more you turn the preamp volume up, the more the tubes impart that sound on the signal. But you can’t play it loud.
So could you, theoretically, put attenuators (lets say -10db) between said preamp and the power amp to lower the output signal which you’d then turn the volume up and drive the tubes a little harder to impart more of the tube’s sound at lower levels?
I hope this makes sense. It does in my head but that don’t mean much.
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Perhaps relevant...I installed an attenuator potentiometer in my Akitika GT102 amp in order to lower its gain to match my Dyna ST70 (w/VTA driver PCB upgrade) to enable hybrid bi-amping (SS on woof, VT on Mid-tweets). The pot was supplied by the designer of the amp to allow a single source input to be run w/o preamp. See: https://akitika.com/documents/VC102AssemblyManualRev2p00.pdf |
jj 12at7 :as the first gain stage or preamp tube the nature of the 12at7 type tube is is a bit bright with a 60-70% gain factor.the nature of jj tubes is even with nice mids and not bright. a bit colourless and dull compared to nos greatest hits off course but not harsh like the chinese or russian tubes usually. ide use a 12ax7(100%gain factor) nos early 70's mullard 12ax7 i63(great low mids ) with low gain ratings or 5751(80% gain factor). that will raise the preamp gain which will result in earlier breakup or clipping and more overall output so if the breakup started at volume 5 now it will be from 3 or 4 so and you will be on lower volume with more of the tube’s gain in the sound and less of the circuit’s gain .the other option is opposite -to lower the gain : more clean range later breakup less overall output and then you can dial more volume which is also nice and makes more sense in audio gear and angry guitar amps i highly recommend mullard 70’s or 60’s 12au7 this type has more lows and about 30% gain factor so the added bass sort of makes up for the loss in preamp gain .within the 12at7 type you can also choose a higher or lower gain tubes and get less dramatic results . you don't need much knowledge or consulting the amp maker for swapping preamp tubes . |
- 41 posts total