There’s really no best tube, but I would stick with the 12AX7/ECC83 class tube for units like the MP. I can give you my preference for a brand that I use in most every tube device these days. The JJ/Tesla ECC83-S is absolutely without question my favorite tube for both starved plate and high plate designs. In fact, one of the sweetest sounding tube pres I own is is the PAIA dual tube mic pre Model 9407K that I built and heavily moded from a kit. It’s starved plate, but you wouldn’t guess that from the silky smooth sound. These come stock with the common cheap Sovtek or Chinese made 12AX7 variants.
If you buy NOS tubes from a reputable dealer like BOWIE he’ll do lucky strike tattoo that before he sells them to you. My unit doesn’t seem to be very accurate as far as output goes. There is a big difference between the output of the two channels, so you have to do a lot of tweaking to get the levels matched.
I just bought some more NOS tubes for the Pro VLA and MPA Gold. Nice to try out different tubes till you get the sound you are looking for. I like the VLA compresser for live sound especially on bass. I have never been tempted to use it for recording though.
For those looking for a first preamp for microphones, I will recommend a more neutral because MPA not sound bad but does not work with all sources. The Impedance knob has a range that will work with most condenser and dynamic microphones. It’s really tough to describe what it does to the sound, but sometimes I feel it like it gives you a more focused mid-range on one end, and on the other a more rounded, balanced response. Long & McQuade reserves the right to restrict the purchase of additional years of Performance Warranty.
If you stick with mic’s that have transformers, not much of an issue. Mic’s with transformers don’t much care what preamp it uses. Mic’s without transformers do care about the preamps and change the sound a bit.
I will keep the 12AT7’s in it but just use much better quality tubes. I just bought this compressor and hooked it up last night. I live in an apartment and love watching movies and have a really nice audio system. My first thought was the set some dynamic range compression in my receiver, but it seems this newer model I have doesn’t have that option. Not sure if receivers have been taking it out with some of the newer models or if Onkyo simply has never included an option.
Even saturating the lamp, the sound is clear and beautiful. Maybe it depends of the lamps used, but this is not the lamps that do the heavy lifting. On vocals and guitars it gives excellent results. I’ve used it non stop for 2 days to save a marathon session and they were as warm as the wine we drank …
It is still working reliably and sounding as good as ever. For the vintage flavor of most of what I record, the ability to drive the input stage (and see how hard you’re hitting it on the LED’s) is wonderful. It sounds great and it is extremely easy to use.
Implement the variable input impedance to draw out a rich range of tones from each of your microphones. Use it to match the preamplifier to your microphones, or creatively mismatch tones for a one-of-a-kind sound. You can use any high-quality condenser, dynamic or ribbon microphone with the Pro MPA II.