Feeler: Quad 8 444 EQ with M/S extension in 51x format.

[ToneShack]

Disclaimer: I have not seen the original thread. That being said, I'm wondering how it happens that the "input" transformer has the same footprint as the "output" transformer. An output type transformer (QEE parts were typically bifilar-wound with no Faraday shield and designed for low-Z drive and loads) and an input type (with Faraday shield for CMRR and designed for hi-Z loads). Their similarity pretty much begins and ends with passing a signal ... they're not interchangeable!

The QEE-3436 input transformer in fact did not have any shielding from what I have seen. There is also a QE-4436 input transformer that is in a can type shield.

 

[MisterCMRR]

The QEE-3436 input transformer in fact did not have any shielding from what I have seen. There is also a QE-4436 input transformer that is in a can type shield.

I guess I'd have to make some measurements to be sure, but it's very, very uncommon for an input transformer to be that large or to be unshielded magnetically. The terms input and output refer to their design, not just to where someone puts them in the signal chain. I was chief engineer at QEE from 1971 (I replaced Deane Jensen, who left to start his transformer company( and was there until 1974 - I never saw anything like that used at a device input. A measurement of winding DC resistances is usually a strong indicator of the design goal. Readings under about 100 Ω each usually indicate output type - readings above a few hundred generally indicate an input type. I'm guessing this was never a QEE design, even in its original form.

 

[ToneShack]

I guess I'd have to make some measurements to be sure, but it's very, very uncommon for an input transformer to be that large or to be unshielded magnetically. The terms input and output refer to their design, not just to where someone puts them in the signal chain. I was chief engineer at QEE from 1971 (I replaced Deane Jensen, who left to start his transformer company( and was there until 1974 - I never saw anything like that used at a device input. A measurement of winding DC resistances is usually a strong indicator of the design goal. Readings under about 100 Ω each usually indicate output type - readings above a few hundred generally indicate an input type. I'm guessing this was never a QEE design, even in its original form.

I totally agree. I cannot find any documentation on the QEE EQ400X. But if it was anything like their earlier equalizers. Then it would have the round can type input transformer.

 

[waltzingbear]

I believe it’s a quad 8 444 eq with transformers added on the input and output. I do have the schematics here.

 

[coil_man]

I guess I'd have to make some measurements to be sure, but it's very, very uncommon for an input transformer to be that large or to be unshielded magnetically. The terms input and output refer to their design, not just to where someone puts them in the signal chain. I was chief engineer at QEE from 1971 (I replaced Deane Jensen, who left to start his transformer company( and was there until 1974 - I never saw anything like that used at a device input. A measurement of winding DC resistances is usually a strong indicator of the design goal. Readings under about 100 Ω each usually indicate output type - readings above a few hundred generally indicate an input type. I'm guessing this was never a QEE design, even in its original form.

The QE-3436 had 3 windings: Primary + Faraday shield + Secondary + Faraday shield + Primary reverse-wound. Both primary windings were wound 2-Pi. EI-625 "low nickel" Super Perm 49. Channel frame. No magnetic shielding. 5K/20K:600. CineMag/Reichenbach Engineering continues to make it, but with 50% high-nickel (Super Perm 80)+ 50% M6 steel, interleaved.

The QE-4436 also had 3 windings: Secondary + Faraday shield + Primary + Faraday shield + Secondary reverse-wound. "Low nickel" EI-375. Super Perm 80 can. 5K:600.

 

[MisterCMRR]

The QE-3436 had 3 windings: Primary + Faraday shield + Secondary + Faraday shield + Primary reverse-wound. Both primary windings were wound 2-Pi. EI-625 "low nickel" Super Perm 49. Channel frame. No magnetic shielding. 5K/20K:600. CineMag/Reichenbach Engineering continues to make it, but with 50% high-nickel (Super Perm 80)+ 50% M6 steel, interleaved.

The QE-4436 also had 3 windings: Secondary + Faraday shield + Primary + Faraday shield + Secondary reverse-wound. "Low nickel" EI-375. Super Perm 80 can. 5K:600.

thanks coil_man! These were "before my time" and never knew of them. But they are unorthodox for sure. It would be interesting to know the reasoning behind the larger cores ... perhaps to fit larger gauge and fewer turns to keep DCRs low. Interesting ...

Do you happen to have access to other QEE documents? If so, I'd love to have copies of the schematic sets for Compumix I and Compumix II. They were my designs but I didn't take any copies when I left.

 

[coil_man]

The larger laminations were to get more signal before core saturation, always measured as 1% @ 20Hz. The winding schemes were not particularly unorthodox. The reverse-wound windings were to reduced leakage inductance resulting in good bandwidth and a reasonably priced transformer. Ed Reichenbach always preached to "fill the window" with copper wire. There are tradeoffs between the number of turns (more means lower THD), the core saturation level (more turns decreases the point where saturation occurs), and net winding DCR with all of the effects that has on performance.

CineMag/Reichenbach Engineering provided almost all (if not all) of QE's transformers. Those engineering files remain in CineMag's archives.

QE's product design files were conserved by Ken Hirsch at Orphan Audio. He continues to support the QE product line. He may have your files. He is on vacation now, but will be back in another week.