Congratulations on building yourself what looks like a very nice phono stage.
I assume the input load network with 2 C1s, R1,R2,&R3 are stuffed or not to conform to the load requirements of your cartridge.
I do have one little nit to pick with Bruce on his decision to not regulate the power supply. The circuity of the amp does not inherently have good power supply rejection. In most cases it won't make a difference but I have had an experience where it did. I had a bi-amped system with an ElectroVoice 30W. With my Harmon Kardon Citation IV every time the fridge would come on it would drive the sub nuts and invoke the protection in my sub-woofer amp. I went a bit nut-so in my protection since as you would expect I'm paranoid of anything happening to my ElectroVoice Sub.
I had to add a series pass regulator to the power supply of the Citation IV to protect the sub from the fridge.
Bruce has much larger power supply caps than were practical in the day when the Citation was designed so he may get by. In any case I don't see a downside in regulating at the point before the supply filter splits to the two channels.
Here is a shot of the monster sub of which I speak:
That is looking at the celing of my stereo room. It is infinately baffled to the attic. The diameter of the driver is 30".
GlassWolf wrote:When I inquired about making the MM pre-amp MC compatible with a low-voltage drive circuit, this was the response I received:
"Hi, Yes ... I would (budget considering) build the MM one and allow a about 6 square inches of board space for the transformers to be added at a later date. Allow room for the switch as well. I was rather hesitant to use transformers at first as I figured they would mess up a good thing. But the more research I did the more premium preamps I discovered that were actually doing that. The only phono preamps that I discovered that were in any reasonable price range to compare to (under 2500) that were as quiet and didn't use transformers were IC based. The Moon LP3 I have is one such unit. Really quiet... but also has a huge amount of negative feedback. I generally avoid NFB in my designs when possible and use it in very small amounts in some (the power amps) to insure stability and not to make them quiet or fix sonic problems. So the phono preamp uses no NFB and the equalization is fully passive. The advantage to that is you can (like I did in my main unit) make plug in cards for the equalization and if needed swap them in and out. So in a round about way, I settled on input transformers for low output MC cartridges. It kept the preamp quiet and didn't really harm the sound. BTW there are several brands of transformers and they come in several price ranges. I used Lundhals because they were available and reasonable in cost."
as per the designer of the pre-amp, which incidentally will be marketed shortly by Oddwatt as a commercial product available in either an MM or MC version.
I just wanted an affordable, quality pre-amp design I could build myself without dumping thousands of dollars on a pre-made commercial unit. Being disabled, money is tight. Having an E.E. degree, I'm able to tinker with building some of this myself as time and money and health permit.