Marantz 7 clone tape head preamp

[Foxbat]

Yes, and it is well described in the video linked here. Also in the video you will find my description of its sound, which is very, very good.

Now, about the comparisons... I think the A807 is a very easy target and that preamp will - in my view, of course - beat it.

I can't speak of the M21 and I have no experience with it, I only have the M15A.

tapepath - you are very welcome, I am always willing to share my experience. Your construction is indeed very nice.

You are right about the input loading - I also put the trimpot in that position, but you need to be careful with it, as it and the HF EQ pot will both affect that region, so I would start with that 100k pot wide open while adjusting the EQ, while watching for some high frequency peaks - sometimes you will see 20KHz or 25KHz ones... then you can tame them with that trimpot.

Another minor comment has to do with the front panel mounted pots. I have done that in some of my preamps. It is, of course, very convenient, but you always run some additional risk of power line interference due to their long wires. Twisting the wires tightly will reduce that pickup, but you will still be able to see those peaks on the spectrum analyzer. They are very small, and nearly impossible to hear, but they are there.

That is why I eventually moved to mounting the adjustment as close as possible to the EQ network. Not as convenient, but less prone to pickup.

I am still curious about your project as I don't see any switching there. How do you select the EQ you want?

 

[tapepath]

Thank you for the very helpful recommendations. I tightly twisted the connecting wires in a drill and then inserted them in a grounded shield braiding. I considered placing all of the wiring inside copper tubing, but will want to do some additional testing before I try that approach. For me, this project is a working test bench, a way to see how the different calibration adjustments effect each other and how they sound in comparison to a reference. I designed the enclosure so each panel is removable to give easy access to any part of the construction.

 

[tapepath]

 

[Foxbat]

So it looks like you are not switching between the different EQ's, but adjusting as you need. I then presume you are going to use the ten-turn dial on each one, so you could quickly return to the desired EQ?

Waiting to hear your impressions!

 

[tapepath]

At this point I'm concentrating on an NAB 7.5 response for this project. I enjoy searching out those vintage London and RCA tapes made in the late '50's and early '60's that have some amazing sound qualities. My principal listening test tape, for this project, is the 1958 London recording of Britten's Peter Grimes. The recording technique they used involved placing the chorus and singers on a stage that had been marked with numbered squares. Each performer was positioned in a specific location after testing how it related to the stationary microphone "tree". Then as the scene in the opera required the singer would move to another marked area of the stage. So if, for example, the Peter Grimes character moves from stage left to the rear of stage right he would continue his dialogue and walk to the assigned area. The result is a palpable recreation of a sound palate with the chorus, singers and orchestra. While I'm sure this was done to highlight the then new "miracle" of stereo sound it meant that spatial clues could be preserved.