Lang PEQ-2A clone...RESURRECTED

Hi All,

I've done a search and there was some discussion of cloning this Eq - including the unwrapping of one of the Freed trafos.  Does anyone know if this clone ever came to fruition?  If not, are the trafos the barrier?

Thanks in advance,

DY

http://www.groupdiy.com/index.php?topic=36225.0
has pretty much all of the info that has been collected around here. Not all of it has been confirmed / corroborated, but its what there is.  

http://www.groupdiy.com/index.php?topic=36338.0
see CJ's last post to get an idea of where the collective progress on these stands.

Seems the iron is half-unknown, and the filter schems are maybe ok, and maybe not. Could be a lot of fun, could be a lot of work (probably both).

There's a whole lot of iron in the Lang, mostly "unobtainium" at this point.

I think PEQ-2A's are still reasonably priced, especially when compared to the Pultec equivalents.

Mark

HI,




  i used to have a pair of Lang PEQ2a. Fricken Awesome. Sad loss . . . .


        ANdyP

Biasrocks said:

There's a whole lot of iron in the Lang, mostly "unobtainium" at this point.

I think PEQ-2A's are still reasonably priced, especially when compared to the Pultec equivalents.

Mark

Click to expand...

Hi Mark,

So what I'm understanding is, the Lang cannot be cloned, and if I owned one and it needed repaired, there's a chance some parts couldn't be replace rendering it a $1,000+ door stop...?

DY

damnyankee said:

Hi Mark,

So what I'm understanding is, the Lang cannot be cloned, and if I owned one and it needed repaired, there's a chance some parts couldn't be replace rendering it a $1,000+ door stop...?

DY

Click to expand...

Google, "Freed 38165" and see what you find. I came up with exactly one hit and that was a pointer to the PEQ2 instruction manual.

I'm sure you could sub something in to prevent it from becoming a door stop, but I doubt it would sound the same.

CJ did dissect the Freed output transformer at one point (200:600), so that would get us 1/2 of the way there. It looks like the input is a 1:1 (600:600) transformer so there's plenty of options for that. Looks like a HS-56 might work in both spots or comparable UTC's.

Mark

Thank you, Mark.

Hmmm...do you think a trafo company like Antek (or any hungry trafo company) would make a prototype of one of these?  I ask because a few years ago, I needed a trafo for an SR&D Rockman Sustainor.  I explained the issue to the trafo mfr and I was told it was a custom trafo not available anywhere but they offered to pull the build sheet, build one and send it to me free of charge.

I know Freed is long out of business but if we supply the details, could one of these small companies make a small run for a reasonable charge?

Just a thought...

DY

damnyankee said:

Thank you, Mark.

Hmmm...do you think a trafo company like Antek (or any hungry trafo company) would make a prototype of one of these?  I ask because a few years ago, I needed a trafo for an SR&D Rockman Sustainor.  I explained the issue to the trafo mfr and I was told it was a custom trafo not available anywhere but they offered to pull the build sheet, build one and send it to me free of charge.

I know Freed is long out of business but if we supply the details, could one of these small companies make a small run for a reasonable charge?

Just a thought...

DY

Click to expand...

for custom transformers talk to brian weston at edcor. Edcor can do any custom job you want and at a good price too. edcor very friendly to DIY people

Sure, but the current stumbling block is no one has dissected the input transformer and I'm fairly sure I wouldn't be willing to sacrifice the one in my PEQ-2A. As for guys to do this, I like Ed Anderson's recreations quite a bit but I'm sure there's a bunch of companies that would do it, like Edcor as Pucho suggested.

I'd try building it with UTC's, TRIAD's or whatever you can get your hands on that are reasonably close to the spec.

I think most of the info is out there including a corrected schematic and access to an original to compare the results.

Mark

Thanks, Fellas.

By chance, would this company be the same Freed of years gone by?   

http://start.cortera.com/company/research/l1o7pyl6s/freed-transformer-co/

If so, I'll be willing to contact them to see if they have any data on their part #'s 38165, 38166, 38167, 37727, and 37744 they made for the Lang.

DY

Looks about right, they're certainly in the right part of the country.

Mark

http://www.electronictransformercorp.com/

Thanks!

I just emailed them...so let's see if I turn up anything (I hope I'm not duplicating anyone's efforts here...).

DY

Power is 50V-0-50V 150mA to give over 62V raw DC, plus a 6VAC which may not be used. One version had higher taps to light a neon with AC; today an LED off the DC would be a better idea.

Actual current draw is probably under 70mA at full roar, 30mA idle. With modern (do we dare?) bridge rectifier and regulators, a 36VAC 100mA PT should be ample.

Input is 600:600 with primary options for that 150-ohm radio network. Since the whole box is nominally unity gain, the input must handle the same levels as the output, 1 Watt max 0.25 Watt with low THD at 20Hz.

I am not happy about the documented OT primary connection; it gives 25 ohm load on the amp, the amp has 100uFd output cap, is unlikely to drive 25 ohms to 20Hz.

Check: unit is rated for +30dBm output, 24.5V RMS or 69V peak-to-peak into 600 ohms. Amp is powered with 33V DC, is good but not great, can swing 25V-30V peak-to-peak. Assuming OT ratio is no higher than required to satisfy a +30dBm spec, OT ratio must be near 1:2.3 to 1:2.8 turns ratio. Primary impedance must be 76 to 113 ohms.

Since we are not driving transmitter or recorder-bus lines, and the original is BIG and should be uncolored at "normal" operating levels, the exact value is not critical. 150:600 would smack the snot out of any modern load, maybe smoke it. Some increase of gain will compensate the ratio difference to get unity gain in bypass.

To preserve transparency, OT should be sized for 1 Watt at 20Hz working far below saturation so we get 0.25W at 20Hz with under 1/2% THD (and smaller for more bass-tone color).

PRR said:

I am not happy about the documented OT primary connection; it gives 25 ohm load on the amp, the amp has 100uFd output cap, is unlikely to drive 25 ohms to 20Hz.

Click to expand...

Not really, these two 50 ohms winding in parallels still make 50 ohms. The 100uF caps into 50 ohms gives 32Hz -3dB power response, but global feedback probably extends frequency response. In fact the cap in conjunction with primary inductance gives a small bump at VLF.

Thanks for the additional info, Fellas!

Ok, for the power supply: would one of these 50V toroidals work?

http://www.antekinc.com/gview.php?d[]=0

For the Lang's power supply card:

C1, C2 = 50V/50uF (available)
D1, D2 = 1N2859A (substitute NTE125? or 1N4002?)
D3 = 1N974B (substitute 1N5258B?)
R1, R2 = 27k (available)
Q1 = 2N3053 (available)

Will the above create the necessary power supply?  (Be gentle...I'm learning here).

Thanks!

DY

PRR said:

Power is 50V-0-50V 150mA to give over 62V raw DC, plus a 6VAC which may not be used. One version had higher taps to light a neon with AC; today an LED off the DC would be a better idea.

Actual current draw is probably under 70mA at full roar, 30mA idle. With modern (do we dare?) bridge rectifier and regulators, a 36VAC 100mA PT should be ample.

Input is 600:600 with primary options for that 150-ohm radio network. Since the whole box is nominally unity gain, the input must handle the same levels as the output, 1 Watt max 0.25 Watt with low THD at 20Hz.

I am not happy about the documented OT primary connection; it gives 25 ohm load on the amp, the amp has 100uFd output cap, is unlikely to drive 25 ohms to 20Hz.

Check: unit is rated for +30dBm output, 24.5V RMS or 69V peak-to-peak into 600 ohms. Amp is powered with 33V DC, is good but not great, can swing 25V-30V peak-to-peak. Assuming OT ratio is no higher than required to satisfy a +30dBm spec, OT ratio must be near 1:2.3 to 1:2.8 turns ratio. Primary impedance must be 76 to 113 ohms.

Since we are not driving transmitter or recorder-bus lines, and the original is BIG and should be uncolored at "normal" operating levels, the exact value is not critical. 150:600 would smack the snot out of any modern load, maybe smoke it. Some increase of gain will compensate the ratio difference to get unity gain in bypass.

Click to expand...

Not sure if this makes a difference;

On CJ's output transformer dissection notes he rated the primary at 200 ohms and the secondary at 600 ohms.

Perhaps the Lang spec paper is not totally accurate.

Mark

I know this is a stupid question, but can't we substitute a modern power supply and Hammond/Lundahl IT and OT?

Obviously I don't have much electronics experience but in my puny brain, the heart of the Lang lies in those Freed Network trafos/inductors in the EQ section.

DY

Biasrocks said:

On CJ's output transformer dissection notes he rated the primary at 200 ohms and the secondary at 600 ohms.

Perhaps the Lang spec paper is not totally accurate.

Click to expand...

The information agrees, the nomenclature is different. 

Biasrocks said:

On CJ's output transformer dissection notes he rated the primary at 200 ohms and the secondary at 600 ohms.

Perhaps the Lang spec paper is not totally accurate.

Mark

Click to expand...

CJ has rated the two primaries in series and two secondaries in series.
In transformer parlance, 150 + 150 make 600, 50 ohms + 50 ohms make 200.
But in the Lang, the two primaries are in parallels; in that case 50//50 = 50