tape — Journal — Monohaus Recorders

So far, so good.

The Nagra showed up well packed and, as far as I can tell, ready to go. I really didn't have to do much to it. I cleaned the heads and guides with Q-tips and alcohol, and the guides were pretty dirty. Other than that, the machine is remarkably clean. It looks almost new.

The first problem was the microphone input. The Nagra has a male XLR, which is backwards from what we use today. I made a female-to-female XLR cable and plugged in the Electro-Voice 635A.

Check. Check. One, two, three.

The VU meter jumped and I could hear signal.

In one ear. Naturally.

The Nagra is true mono, so I'll need a 1/4-inch mono-to-1/8-inch stereo adapter to get the signal into both sides of my headphones. The line-in and line-out cables are being made now, but in the meantime I found a way to pad the Nagra's input so I can feed it a line-level signal and use the microphone gain control as the final level going to tape.

That has been useful for testing.

I've been putting jazz records through the machine and listening to the repro while the tape is recording. It is a simple way to hear what the Nagra is actually doing to the signal. I've been playing with the EQ, limiter, and the new CTX Color Card and listening to how each stage changes what comes back off the tape.

I also muted everything, turned the Nagra preamp all the way down, and just listened to the tape.

It is quiet.

I was expecting more noise, especially at 7.5 ips, but the tape and the Nagra preamp are both quieter than I expected. I don't think tape noise is going to be much of an issue.

The bigger thing I'm hearing is the frequency response at 7.5 ips. There is a roll-off in the highs, with the machine getting out to around 15 kHz, and there is a little lift in the lows. Switching back and forth between the source and the repro while it was recording made it pretty obvious that the signal had gone through a tape machine.

Which is exactly what I wanted to hear.

I've recorded two albums onto the reel now, mostly just playing around and getting a feel for the machine. It has been fun. I'm only working with one mono signal at the moment, but I'm learning what the Nagra is going to do before I put the whole system together.

The 600 Ohm Comb Net - aka “The Chuck Box”

The summing box is finished too. It is built by Chuck and labeled the "600 OHM COMB NET," which I assume means combining network. It looks exactly like the sort of thing I hoped would come out of this project.

The next test is the real one.

Four microphones into the 501s. Into the combining network. Through the CP5 and CTX Color Card, the 511 and the XLA-500, and finally into the Nagra.

If everything behaves, I'll take it out to a local location with a grand piano and make a test recording.

I'll do the first one myself. If that goes well, I'll bring a few friends in and make a proper recording.

I want to set it up exactly the way I've been imagining it.

For now, I have the first reel, the RTM SM911. Right out of the box I really like this tape. It feels good in your hands and it sounds good coming back through the Nagra. There is something satisfying about having a reel of tape that you actually recorded something onto.

I want a shelf full of them eventually. Good music. Good performances. Good moments. All on mono 1/4-inch tape.

That's the idea.

Well, I got the Monohaus Machine…a Nagra Model E.

It was originally designed for radio reporters and news gatherers. It is a mono, full-track machine, which means the mono signal is recorded across the entire width of the tape. A conventional stereo recording divides that same width between two tracks, with a guard band between them to keep the channels separated.

This is the beginning of the Monohaus setup.

The front end will consist of four Electrodyne 501 microphone preamps, passively summed to mono through a small metal box with four XLR female inputs and one XLR male output. Inside the box is a passive resistor network that attenuates the summed signal by approximately 10 dB. That signal will then be brought back up through the DIYRE CP5 preamp, which contains a CTX Color Card.

The Color Card consists of a 2520-style op-amp socket and a Cinemag transformer. Although the signal has already been passively summed, the CP5 will provide the makeup gain required to bring it back to a useful operating level, while the transformer and amplifier stage will add another layer of character to the summed signal.

From there, the signal will pass through an Electrodyne 511 EQ and an Acme Audio XLA-500. These will serve as the master-bus processing. The 511 will function as the program EQ, while the XLA-500 will provide the final compression, essentially acting as the program compressor.

Chuck at the oscilloscope — Chief Technical Engineer Chuck Garsha at the oscilloscope and Audio Precision testing the gear for the custom mono mixer. Sep 2026

A future project may be a master volume control with a mix-bus insert switch, allowing the entire master chain to be A/B tested at will. Both the Electrodyne EQ and the XLA-500 already have bypass switches, so there is no immediate need for this. But if the mix-bus processing changes in the future, having a dedicated insert point would make it possible to quickly compare the processed and completely clean paths.

For now, the system is simple:

Microphones → Electrodyne 501s → passive mono summing → CP5/Color Card → Electrodyne 511 → XLA-500 → Nagra E.

That is the machine.

In terms of microphones, I am particularly interested in trying the Beyerdynamic M 160 ribbon. The combination of a ribbon microphone and hypercardioid pattern seems like the right starting point for trying to recreate the sound and working method of the location recordings I admire, particularly jazz recordings where microphone placement and room interaction become a significant part of the recording itself.

I have selected RTM SM911 tape for the project. It is a +6 tape, and combined with the full-track mono format, I am hoping to achieve a signal-to-noise ratio that is comfortably usable while retaining a tape character that feels pleasing rather than distracting. That distinction matters. I am not trying to eliminate the fact that this is tape. I want the tape to become part of the sound.

The Nagra did not come with a power supply, hookup cables, or the various accessories required to actually put it into service, so I have been sourcing those pieces individually. So far, that process has been surprisingly straightforward. The remaining accessories I need are the input and output cables.

There is still a considerable amount of testing to do.

The next step will be to use the Audio Precision analyzer to establish the Nagra's actual operating specifications: input voltage requirements, impedance, headroom, and the other measurements that will tell us exactly what the machine wants to see at its input. The goal is to feed it the highest-quality signal possible without simply guessing at what the specifications ought to be.

500 series lunchbox with Electrodyne 501 preamps, a CP% Preamp, an Electrodyne 511 EQ and an Acme Audio XLA500 compressor — Ok, so technically not a console - but 4 Electrodyne 501s summed to mono though a passive summing network, make-up gain through a DIYRE CP5 equipped with a CTX color card and finally through an Electrodyne 511 EQ and an Acme Audio XLA 500 limiter as the master bus processing.

We have already gone through this process with the mixer components. Measuring the individual pieces gave us the information needed to design the passive summing network properly. There were some interesting discoveries along the way, including variations and tolerances that gave us confidence in moving forward with the resistor values we had initially selected.

There is something satisfying about that process.

Rather than assembling a collection of equipment and hoping that it behaves like a recording system, I am trying to understand what each piece actually wants electrically and then build the system around those requirements.

If everything works as intended, I will have created what may be the smallest Electrodyne console ever conceived. It is not a conventional recording system and more testing is needed, but the basic architecture is beginning to take shape.