Driver/Input tubes


I need somebody to either explain or steer me to an explanation of the 12AX7/12AT7 tube's purpose in my Jolida JD502P power amp. I get preamp tubes in a preamp, but I've found it difficult to find a clear explanation of what the "driver" and "input" tubes are actually doing, and their relative importance to the sound of the amp. The 502P seems to have a typical compliment of these tubes, sharing its basic design with a lot of apparently similar power amps. Brain trust...hep me...hep me...
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Showing 5 responses by wolf_garcia

What point about phase inversion? I do understand the concept of the signal level boosting my preamp does, but wondered why 2 similar tube pairs, 12AX7 and the lower gain 12AT7 are utilized in the power amp...I think I did read someplace about signal splitting...so we're close!
Good answer but Johnsonwu...come on dude...you know me...I would NOT understand a schematic. I could take a basic electronics course at a local community college but it would drastically cut into my nap time. Also, the Jolida doesn't have 12AU7s but my tiny headphone amp does have one. Just one. And it's cute. Your post has only one tube I'm actually employing in my amp but I sort of get it anyway. I think your explanation, although convoluted, has dragged me kicking and screaming toward almost understanding this thing. Closer...I'm getting closer...
I appreciate all of this...although I think my comprehension capabilities are being woefully overestimated. I'll look for the schematic...but bear in mind my amp is a 502P basic power amp, NOT an integrated, hence the query.
My understanding is that the 12ax7s are the input tubes, have the greater influence on tone, and the 12at7s do the driving. It seems the EH 12at7s are relatively well regarded in the driver role so I'm using them (they're stock with a new JD502P), and switched the Tung Sol 12ax7s to a matched pair of Thetubestore's "preferred" ones (select Chinese it would seem) and I love 'em...they provide a little more sparkle, tonal accuracy, and aren't expensive.
I bought a Class A single ended boutique guitar amp and the manufacturer (Burriss) swears by new Mullard 12AX7s, and they seem to work fine.