Don-Audio MEQ vs Analogvibes midrange eq chassis

[Script]

Noise and pickup should get better once the lid is firmly screwed on. Did you try ?

Mine even picked up a radio station when lid was open.

 

[HerbertR]

Thanks Script, it is better. My MEQ5 EQs with Gyrafs SSRP Makeup Boards and Don's MEQ5 Filterboards are finished now.
Here are my building experiences:

- there is one really big advantage with Dons MEQ5 Filterboards compared to the original schematics - you can directly use cheap 2x6 and 1x12 Pos Lorlins. The PCB circuits for the LC Filters are modified. There is no need for the expensive 2x11 Position...or other expensive rotary switches.. But Don's PCB employs the same Inductorsvalues like known from the original and in other clones. So you can easily use other good manufacture companies like from Cinemag or Vintage windings....

- as said my EF Inductors from Dons were way away for the target values but they sound incredibly good. I compensated the frequencies with recalculating the capacitors values.

- The Hi Band Inductor / Circuit is especially very sensitive and works like a big antenna. I had never any sensitive builds like this one before. If I would build a new pair I would necessarily use shielded Inductors. Thats makes REALLY sense! Not so in my build... ....and that leads to a lot of extra work to get the EQs quite...

-I ve implemented a EMI/RFI Schaffner FN Filter for 230V Power Supply filtering - that also helped enormous getting noise away

- I ve used lots of shielded cables. Mine one are shieled Alpha Wire Cables (expensive....) from Farnell, top quality, all shieldings are connected to ground

- I ve outsourced all Psu transformers in extra hardwired cases. The used Dons EF inductors were way to sensitive to house in the same case, both EQs are now really quite, yeah....

-The most "hard to come by" part is the C2K5 Revlog Potentiometer. Read my upper post. I took a more commonly used Dual C5K like from Alpha Potentiometer (Tyda Electronics) with both 5K gangs in parallel to achieve a C2K5 Potentiometer, works perfectly

-The Gyraf GPultec SSRP Stage is fantastic in this build. It does with the Lundahl thing "the ready to Mix" .... Not overdrawn low end, nice expensive transparent Hi and mids... The used Sovtek Tubes are driven with about 220VDC B+, the Heater Voltage is exactly set from 6.03V to 6.3V through changing the 470R / 1K8 from the LM317 a little bit, the LM317 is mounted on the case, it gets hot, a small heatsink is to less

- The Dons MEQ5 boards do not provide an "active" Bypass, so I decided to use a "real" Relay Bypass. For switching these 12V Relays and also all Lamps a cheap 12V Meanwell PSU is employed. Using the 6.3V Heater-Rail in parallel for driving the Relays ended in overloading the LM317 with to much heat dissipation - Themal shutdown. Honestly - the rectified Voltage of a 12V AC TX1 Secondary with 12V AC *1,41 Voltage difference to 6.3V DC is a little bit high for a LM317 providing the 300mA Heater current for the Tube. But with more consumption on the LM317 you will easily reach the limits.
(I think it would be worth to test the Gpultec PSU/SSRP Board with TX1 220V AC Pri / 9V AC Sec and back for the B+ with TX2 12V AC Pri / 220 V AC Sec. After rectifieing the DC Voltages should fit much better for LM317 regulating and for tweaking the B+. Much less / Delta Voltage and following heat dissipation on the LM317, and also about 235V DC after the B+ recifier, the suggested 3K3 B+ Drop/Tweakresistor at 5mA should pushes then the Voltage down to ideal 220V DC B+)

For a perfect passive loss Makeup performance I would need about 2.5dB more level out from the SSRP Circuit. Does anybody know how to achieve that / with a feedback loop? If not, it is not a problem. A awesome good EQ.

Cheers

 

[Script]

Awesome builds.

 

[soapfoot]

This discussion is timely, because I’ve got three MEQ5 builds in AV chassis that are giving me fits. I just cannot get them quiet enough.

In my case it was the mid dip that caused the most hum when turned up.

I noticed what I think is a pretty big potential issue—the power transformer mounting holes on the chassis position the PT in an orientation that’s rotated 90 degrees from the original MEQ-5 and the Pulse Techniques reissue.

After some drilling and rework, I rotated the PT to a position that matches the vintage and reissue units, and I believe this got me about a 9dB reduction in hum.

Then I started experimenting with the orientation of the coils inside the filter box, and discovered that even with the PT in the new position, it really mattered a *lot* how the inductors are oriented

I got them all co-planar (in the orientation as though they were “sitting on the floor” as opposed to “standing on their end”) and the noise got bad again. But rotating the box so that all three were “standing on their edge” as far from the PT as possible and it was almost as quiet with controls maxxed as with the unit in bypass.

There’s a caveat, though—after making this discovery, in the process of trying to install the coils permanently in this orientation, I noticed the lead-out wires were breaking as a result of stress from all the rework. It’s at least possible they were broken or intermittent on my earlier test, so I’ll have to confirm this result once new coils arrive.

No wires in mine are shielded, for the record.

 

[HerbertR]

This discussion is timely, because I’ve got three MEQ5 builds in AV chassis that are giving me fits. I just cannot get them quiet enough.

In my case it was the mid dip that caused the most hum when turned up.

I noticed what I think is a pretty big potential issue—the power transformer mounting holes on the chassis position the PT in an orientation that’s rotated 90 degrees from the original MEQ-5 and the Pulse Techniques reissue.

After some drilling and rework, I rotated the PT to a position that matches the vintage and reissue units, and I believe this got me about a 9dB reduction in hum.

Then I started experimenting with the orientation of the coils inside the filter box, and discovered that even with the PT in the new position, it really mattered a *lot* how the inductors are oriented

I got them all co-planar (in the orientation as though they were “sitting on the floor” as opposed to “standing on their end”) and the noise got bad again. But rotating the box so that all three were “standing on their edge” as far from the PT as possible and it was almost as quiet with controls maxxed as with the unit in bypass.

There’s a caveat, though—after making this discovery, in the process of trying to install the coils permanently in this orientation, I noticed the lead-out wires were breaking as a result of stress from all the rework. It’s at least possible they were broken or intermittent on my earlier test, so I’ll have to confirm this result once new coils arrive.

No wires in mine are shielded, for the record.

Hi soapfoot,
I really can recommend to use shielded wire and connect the shields to the ground. I bought screened "Alpha Wire 3312" 12 screened wires / about 8 Euro per meter for connection of the rotary switches, and "Alpha Wire 3303" with 3 screened cables for connecting the Potentiometers/ about 5 Euro per meter. Farnell has a lot of other screened diameters and amount of wires on stock. I would replace as much Audio paths as possible with screened/grounded cables. I think this is also the only way in your builds to solve the most hum/noise issues. For the Power TX the same. Outsourcing, or at least as far away as possible, especially from the Pots, switches and inductors. Or shielding with expensive Mu Metall.... At the end it is really worth to do every effort fixing these issues....

 

[MiamiBoy]

Don's front panels looks great, beautiful blues.

It just annoys the crap out of me, when they're advertising the front-panels with closed "rack ears" on their website, and when you order one, you'll received a front-panel with open "rack ears", and they expect you to accept that!

Manufacturing "open rack ears" is lazy and cheap. You should be honest about what you're selling!