Products

Products

Since all my tube consoles are custom built there are no standard products as such, so this section simply lists all the products to date starting with the latest and ending with the first prototype.  Information on both completed products and work in progress is given.

EZTubeMixer

My early mixer designs were based on the mu follower circuit used in a gain structure based on early tube mixer designs by RCA from the 1940s. Although these give very good performance and allow the selective addition of tube tone, they do have a couple of disadvantages. The first is that their output drive capability is limited. They cannot drive both a mix bus and an output transformer at the same time so mixers with a direct out per channel are not possible. The second disadvantage is that their gain is fixed so mic pres with stepped gain switches are not possible. It was to solve these problems that a new preamp called the Eurochannel was developed. This has two identical preamps on a single Eurocard sized PCB that plugs into a backplane using a 32 way DIN connector. One amplifier has some additional components that turn it into a versatile mic pre i.e a microphone transformer, 48V, phase, pad and mic/line switches plus a stepped gain control covering a gain range from 26 to 60dB and a relay switched HI-Z instrument input. The output from this preamp provides a pre-fade bus feed and can also be fed to a fader and/or passive EQ circuit and back to the second preamp which provides gain make up and has its gain set by a pre-set pot. The second preamp provides post fade bus feeds and is also capable of driving a transformer to provide a balanced direct output (if a pre-fade direct output is required this can simply be taken from the output of the first preamp).



This PCB, along with new versions of the Helios 69 and Pultec EQP1A EQ are used to build channel modules that are 6U high and 2.8 inches wide. These modules plug into the backplane of a standard Eurocard sub-rack. Building relatively complex tube mixers now became so simple it was christened the EZTubeMixer and became a DIY project at groupdiy.com. The mic preamp has provision for fitting input transformers from Sowter, Jensen and Cinemag.




Three standard forms of passive EQ are currently available. One is based on the Helios Type 69 which is popular with musicians . The second is based on the Pultec EQP1A with an added mid boost/cut section based on the MEQ5. (above). The third is based on the bass and treble EQ found in the REDD 47 desks with an added mid boost/cut section based on the RS124 'brilliance' module.

Mic preamps and passive EQ are combined into channel modules which are 6U high and 2.8 inches wide. Six modules will plug into a standard 19 inch sub-rack.


To facilitate wiring between channel modules, a backplane PCB is used. This supplies HT, heater, phantom and relay power to all the modules, connects the mix buses across channels and provides  fader, mic/line input and line output connection for each module.


The backplane is in turn fitted into a standard sub-rack:


And the sub-rack is fitted into a frame:


And here is the finished mixer




6 Into 2 Mixer

My first custom all tube mixer was for a client who makes on location classical recordings. For maximum fidelity a minimum signal path design was used  with a simple passive switched high pass filter per channel. Each channel also has switchable phantom power, phase reverse and 20dB pad. Rather than pan pots, each channel has Left and Right assignment switches which allow each channel to be routed Left, Right, Centre or Off.


First Prototype

This was built in 2010 as a test unit so I client could check out the sonic signature of the design.


The  intention was that the metal chassis running along the centre and the tag board holding components above it would be replaced by a single PCB. Here is a picture of the bare PCB.



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