For many years now, I have been using Dick’s (Audio Creative) N30P Mu Stage Design. He called it the Cleo 6. It is a great double mono MU-Stage amplifier (see circuits) with top components. Over the years I started to see the benefit of using Arduino computer boards as a control tool, so I decided to upgrade this preamplifier to the next level of convenient usage: The CLEO 7 🙂
This is what it will be spec’d with:
- Tube Power supply with GE 6X4 and CLCLC filter
- 6N30P (actually 6H30Pi) Mu-Stage with Mundorf Gold-Silver-Oil & V-Cap couple C’s
- Volume and other functions to be Arduino controlled (Both by a rotary encoder at the front panel as well with a IR remote)
- 24 Steps relay driven volume control with individual 2 resistors shunt attenuators
- 6 Source inputs
- 2 Tape Out, independently selected from Source
- 3 outputs: XLR and RCA
- Tube amplifier BIAS points checked by Arduino analog inputs: Power supply voltage, Output voltage and Triode current
- 4×20 LCD display showing all relevant information
At the left you can click for the first draft to get a PDF file with the schematics other information of the Cleo 7
This will be updated as soon as I finish the new drawings…
I designed a PCB which contains the selections, input and outputs, as well the volume control. The Arduino board is embedded on the PCB. This will make my life easy and they (plural; the minimum order was 5 pcs) just arrived. Additional parts and a new chassis were ordered. Next step is to build the control board:
The mainboard control unit
Next step was to build the control board, write the Arduino code and test everything. Finally all components arrived so I could start building. That has been done now and 95% of the code works fine. As you know software is never ready, so any tweaks will be done later. But the basics are working. The volume control, the selection of the source and tape out as well the Bias Check of the Tube stage.
As you can see in the picture, I am using a generic remote control I found on Ali Express. It has some nice basic buttons which fitted nicely to my desired functions. I have a simple Arduino UNO setup to read the codes and plug these in the code. The display shows the normal condition. It also has a LCD settings menu and Bias check function, but as said, it is all software.
More important, all hardware and the volume control works fine. The number of relays indicate, recognizably, that I choose to go the complex way of shunt volume and not a ladder network. So for 24 steps you need 48 relays 😉 It is quite a puzzle to calculate the resistor values which are actually available, but I managed to have pretty precise 2dB steps and some 4dB steps at the end of the scale.
In the meantime I have dismantled the “old” Cleo 6 and designed the front, back and top plates. I use the software of Schaefer Berlin for this, as for all my projects. This also leads to a nice coherent look of all equipment together you find them here: https://www.schaeffer-ag.de/
Next step is the re-construction of the amplifier and do the functional testing and of course the listening tests!
to be cont’d !!