Neutrik MINIRATOR pocket-sized audio generator - Quick fix and teardown

[ciccio]

Yesterday I opened for a quick-fix  my trusted, 12 years old,  Neutrik Minirator pocket-sized audio generator.
The fix was really quick: I had to re-solder  the RCA socket (an "esoteric" pin plug was inserted and it was so tight-fitting that removing it resulted in a desoldered socket), and I did not document it, but when I looked at the internals of the instrument I thought that it was worth a post.
This instrument is a MINIRATOR made about 12 years ago  by Neutrik in Lichtenstein.
At present time  an improved version (actually two version) are made (still in Lichtenstein) by NTI audio a.g.,
This small size, battery powered unit ( 2 X AA)  is invaluable for professional audio work, because it can source a balanced (or unbalanced) signal (low distortion sine, square, sweep sine, asymmetrical polarity test, pink or white noise), with selectable frequency (all standard ISO third-octaves)  and level (from -60dB to + 6 or 4 dB).
Being battery powered, it will not give ground loops problems, and you can plug it in place of a microphone, even if no mains power is on site.

The engineering of the unit, both electronic and "packaging", is remarkable:

Figure 1 show the unit,  Figure 2 shows the rotating 3-pin XLR connector (balanced out),  Figure 3 shows the unbalanced RCA pin socket.

The unit opens by undoing  4 self-tapping screws:  Figure 4 shows the 2 parts of the body.
See the rotating XLR and the spring contacts. More of this later.

The PCB is held in place by a single self-tapping screw (and by one of the battery tabs, that fits inside grooves in the molded case).

Figure 5 shows the PCB, component-side. It is a multilayer board (4 layers, I believe).
There is a label stating "copyright 1998. I believe that the there were no DDS chips available, so the  design uses a microcontroller driving a D-A converter, with (I believe) some type of stored tables.

The quality of the photographs is not very good, so I'll list the active devices, from left to right:

The DC converter is a MAX1672, placed between two big tantalums caps.
The main controller is an ATMEL  AT90S8515,  which drives the LCD and the D-A converter, an ASAHI KASEI AK4317VF.
The latter is an interesting component, because it includes both a 18 bits DAC and a programmable attenuator.

The 16 pin is a HC4053 triple analog multiplexer (don't  know it's function), and the 8 pin are two OP284 dual op-amps.  These op-amps are low-noise, low voltage, rail-to-rail devices that spot a very high price (about 9 USD each!!).

Figure 6 shows the spring contacts which connect to one of the battery poles and to the 3 pins of the output XLR. They are held in place by suitable grooves of the plastic molding, as shown in Figure 7.
The rotating XLR is shown in figure 8. I's very simple to rotate it inside the instrument's body before putting it inside your pocket.
Figure 9 shows the two rigid wires that connect the RCA unbalanced connector to the spring contacts. You can see the soldered joint I had to rework.

Last,  Figure 10 shows the back panel with complete operating instructions, and a "Made in UK" label.

Best regards

P.S. I've tried to place the images inside the text, for clarity, but I could not find a way for doing so.
Other poster do that, so it's my fault. Please let me know how to do this.

[Polossatik]

lovely stuff,

I like a piece of equipment  where you might pay extra $$ but the tool is actually useful IRL seen it's properly designed.

[djsb]

I love the name Neutrik, very clever brand name. Sounds like a name thought up by a smart US audio engineer but it's a Swiss company, which I didn't know. Love their audio connectors and it's one name you won't find associated with audiophoolery.

David.