A few general comments…
So, yeah, if pushed to state a preference, I like the M-500 series better. But as a related aside, you won’t find an 8-channel M-500 series console, and I think the M-308B is one of, if not the best mid-range 8x4 consoles you can find when you consider the full feature set, build and signal path.
Mic amps…I think both the M-500 and M-300 mic amps sound fine. I think they sound full. There are a ton of mid-price or budget consoles you can get. And different people equate “good” with different things. And it’s all relative to what an individual has experienced and what their needs and taste are. And when somebody gives a review of any sort of device or product we often don’t ask what that reviewer’s experience set is. So I’ll tell you my experience set ranges from what are, to me, great mic amps in my Studer console, to what I’ll categorize as crappy mic amps on a Behringer MX-802 mixer I used to have…took the life out of anything with any sort of dynamic range. And the Studer mic amps have life and sparkle and handle what you throw at them, clean and quiet, lots of gain range. And I’ve worked with many, many Tascam mic amps, as well as MOTU, Presonus, Yamaha, Allen & Heath, Audio Technica, Alesis, ART, Biamp, Mackie, and Soundtracs…and out of sheer curiosity looked at the circuit topology of most of those. The M-300 mic amp has a fairly common dual transistor input stage with an opamp following. There’s a fairly large polar bootstrap cap in there. The opamp is the 5532 which I like. I think the M-300 mic amp sounds good. It has a full sound. It has 44dB of gain. The M-500 mic amp utilizes 4 transistors up front, with an 072 following. There is also a fairly large bootstrap cap but the circuit design affords that cap to be non-polar. By the spec sheet the M-500 mic amp has 58dB of gain. I never had a problem with how it sounded. There was an earlier comment in this thread about how it handles transients. Who knows. The transistors are 1844 and 1815 parts which were widely used in a lot of audio gear…but maybe messing with those might do something with how the front end handles transients. Or maybe replacing the bootstrap cap with a higher quality audio-grade part would help. There’s also always the option of trying different opamps. The TL072 gets bastardized. It’s not a bad part and you’ll find it *everywhere*. Even in holy grail equipment. It’s not about the individual part. It’s about the whole circuit design. Anyway, I know something like the OPA2134 is an easy drop-in replacement for the 072 in this circuit. I’ve never tested the 5532 there. The 072 is a jfet part and the 5532 bi-fet. You can’t always put the bi-fet part in place of the jfet part. It depends on the circuit and you have to test it by first measuring the DC offset at the output of the stock part, and then install the 5532 and re-checking the DC offset. If there’s a significant increase then the 5532 is not happy in the circuit. I’ve never tested the 5532 in the M-500 mic amp. Now I’m curious to do that. Generally my experience is, when I can swap in a 5532 in place of an 072, the sound is more exciting or alive. Yes. This is all horribly subjective. But that’s the best way I can describe how I experience it. The signal path of my early 80s prototype Tascam console, the “Tascam M-__”, is, like the M-500, all based around 072, 2041 and 4556 parts. This is because it was a prototype for the M-50/M-500. The EQ section utilizes 6 TL072 opamps. The 5532 works as an upgrade for 3 of them. I like the change. The mic amp in the M-__ is identical to the M-50/M-500. It is also the the same mic amp as is found in the MX-80 rack-mount 8x2 mic mixer, which is a neat box. My point? The mic amp in the M-500 is more intricate with higher gain than the M-300 and most mid-range consoles from that era. And when you compare to more present day offerings you have a number of devices that have very basic garden-variety differential input circuits. But those are touted as “quiet” and “transparent”. Fine. I think the mic amp was more expensive to manufacture in the M-500 than many contemporaries as well as products that followed, and the marketing people are super good at convincing something is “better” that is cheaper for the manufacturer to produce. And all the while the designers and engineers are quietly dying inside because they know it’s not better. But that is how it goes. And the masses on the interwebs follow the words of the marketing people. And this is how it goes. So I’ll just say it is important to, when possible, try stuff out for yourself. And form your own opinions. Because your needs and ears and specific setup are unique. You’ll read plenty of negative opinions about the M-500 on the interwebs often without any frame of reference as to the reviewer’s background and experience with other gear, and, again, often the questions to fill in those gaps go un-asked. I know it’s not typically easy to just go try stuff out and compare. But that really is always the only thing that will inform you how a device or part of a device performs and works for you.
Okay…that’s probably too much.
But thank you for all of the info! I haven't gotten into the circuitry yet of consoles, but that's something I plan on getting into in the future.
