EZ Tube Mixer Support Thread

[anjing]

I'm thinking of moving the eq on top of the amp card so i can add a new row of backplanes under the amp cards for the master amp module, the aux amps and also some stereo line amps.
It would be like this:
-eq
-Preamp
*master(or other module)
-fader module.

The reason i want to do it like is to keep the top and bottom backplane next to each other. Also since the eq don't go as deep i can stack a shallow 3u eurorack on top and use the empty space on the top  of the longer 6u eurorack to mount the panel connector vertically.

The only thing i'm worried is that it's gonna cut the top to bottom flow of the channel strip.
I have been thinking about this a lot and i want to keep the 84 width but want to add more channels...

What do you guys think?

Pierre

 

[anjing]

Front view

 

[ruffrecords]

Hi Pierre,

The only real difference is in the wiring to and from the EQ. In a 6U module this is entirely internal. With the EQ above you need to route the screened cable from the fader to the EQ input at the top and then from the EQ output back down to the second stage of the mic pre - probably into the fader pins which would be spare.

The extra distance from the fader to the EQ should not be a problem as the source is a reasonably low impedance. The output impedance of Helios and REDD EQs are always close to 5K so the short length from the EQ output to the mic pre input should be OK. The Pultec EQ has a higher output impedance, especially when using bass cut, so its output lead needs to be kept short so as not to invite interference or HF loss due to cable capacitance. However, the distance is very short so I think this should not be a problem. Note that you would have to use the 3U versions of the EQ and there is not one for the Pultec.

Cheers

Ian

 

[anjing]

Thanks Ian!

 

[dipfrik]

Hey,

i'am searching for the right Grayhill Switch for the Low Boost/Cut on the Helio69 PCB.
Is this one correct?

71ADF30-02PAJN
http://www.digikey.com/product-detail/en/71ADF30-02PAJN/GH7328-ND/665931

It's a 1-Pole 2 Decks and 2-12 Positions.

Thanks for any help, Sven

 

[ruffrecords]

Hey,

i'am searching for the right Grayhill Switch for the Low Boost/Cut on the Helio69 PCB.
Is this one correct?

71ADF30-02PAJN
http://www.digikey.com/product-detail/en/71ADF30-02PAJN/GH7328-ND/665931

It's a 1-Pole 2 Decks and 2-12 Positions.

Thanks for any help, Sven

That one is OK if you want one with a one eighth inch diameter shaft. If you want a quarter inch shaft its the 71BDF version you need.

Cheers

Ian

 

[Holger]

A historic moment (at least for me): the first working channel in my 12 channel frame.

 

[anjing]

Amazing Holger! This is gonna be one big achievement!

Regards,

Pierre

 

[dipfrik]

...as of today i'am starting my EZ Tube Mixer journey

Step 1: Building a PSU (with a missing big 4700uF cap so far)

Can't wait to push some volts through that board tomorrow!

Night, Sven

 

[Holger]

I/O modules.

 

[dipfrik]

Stage 02 -> Assemble the EZ Mixer Card and connecting the PSU without burning down my loft  8) = completed

Learnings so far - definitely need to tweak the resistors on the PSU PCB to match the correct voltages under load.

Tomorrow i will feed some audio through that baby!

Night, Sven

 

[dipfrik]

Friday the 13th...i can tell you stories!

After a fight of death with some (two is the correct number) toroidal transformer (i burned both completely) - who knows what the issue was - i started from scratch and what can i say: i have a working and lovely sounding EZ-Tube Mixer "Channel" (which sounds awesome and provide gain until the ambulance is needed  ) with a Helio69-EQ in its purest form runnig.

I was totally surprised how this EQ sounds in real. Kick ass! I build a lot of different EQ's the last months with an obsession for pultecs, but now i need to call it even! Unbelievable on the drum buss - crazy on bass guitars, even on my master chain i can tweak the hell out of the mix.

@Ian - Nice Jobs! Well done!

Now its time for football or maybe the REDD EQ.  8)

Night, Sven

 

[ruffrecords]

@Sven,

Well done. Nice build and many thanks for the kind words. It makes it all worthwhile when someone says they like your designs.

Don't worry too much about trying to tweak the HT voltage. The circuit is very tolerant of HT voltage but if you are running just one channel you could probably up the HT series resistors to 1K.

I always like to have audio samples because many people contact me asking what does such and such an EQ sound like. I would rather have samples from people who have built my EQ. So if you would make a sample for me I would be very grateful. Drop me a pm if it is OK.

Pierre also hosts a gallery of completed projects of my designs so if you want to submit pictures for that as well that would be good.

Cheers

Ian

 

[dipfrik]

Maybe someone of you can help me with a strange problem after i bring in an output transformer.
I'am using the Carnhill VTB2291 wired in a 2k4:600 configuration. I attached a screenshot of my output transformer setup.

Without the output transformer, i run into no problems if i'am switching through the gain steps. (at some higher gain values i got a lot of distortion and clipping but everything as expected).

With output transformer i have exactly at the the gain step position from 6 to 7 that loud hiss/hum immediately. It's not distortion/clipping because i can eliminate the transformer (unbalanced output) and everything ist normal. Also this loud hiss/hum is exactly at the same gain switch position in mic - mic with pad - or line with the output transformer. Without output transformer is everything fine.

Anyone know this problem?
Wrong output transformer wiring? (yes, i tested two different VTB2291 with exactly the same outcome).

Thanks, Sven

 

[ruffrecords]

Hi Sven,

That is a strange problem. First I can say your transformer is wired correctly so that is not the problem. However, it might be worth checking the dc resistance of the windings to make sure the secondary is lower than the primary - the reason I say this is that I had one VTB2291 in a batch of 8 that had the primary and secondary swapped! Even so, such a fault should not cause the problem you have. The first thing I would do is check the value of the gain resistor at the gain setting that causes the problem.

Cheers

Ian

 

[dipfrik]

Hey Ian,

thanks for your help. I checked all the resistors in the meantime and everything seams correct and it is the same behaviour on both carnhills that i have here.

And to update the situation: It is not the "one" gain settings but also any higher gain setting from there. Again, without transfomer no problem in all positions.

Cheers, Sven

 

[dipfrik]

...also i checked with an Edcor 15K/600 and the same behaviour but now the effect happens at later/higher gain settings.

 

[dipfrik]

...i also checked without the helios eq. Same behaviour when i grab the signal direct from OUT1. After position 6 the strange hiss/hum is starting.

 

[dipfrik]

...a video tells more than words

http://youtu.be/_Sb6LEVztPg

Cheers, Sven

 

[ruffrecords]

...a video tells more than words

http://youtu.be/_Sb6LEVztPg

Cheers, Sven

OK, if it does it with OUT1 then it is clearly in the first stage. It sounds a bit llke the problem I had a few weeks ago with the HT supply of the EZTubeMixer I am building. Try connecting a 100nF 400V capacitor straight across the HT supply where it enter the PCB.

Cheers

Ian