Lang PEQ-2A clone...RESURRECTED

[Biasrocks]

Good news, I would recommend getting the transformers in their original cans, they are physically large enough to present a problem with mounting them inside a case and it just makes sense.

It's shaping up that the Lang wasn't a cheap Pultec knock-off afterall...

If you'd ever plugged into one you'd know instantly that a Lang is no-ones poor cousin. It does things the Pultec can not.

Mark

 

[damnyankee]

I've never plugged in to one and I haven't built the Pultec because I'd rather invest in a Lang; and we're on the cusp to learn what makes the Lang so special.

And whoever said the "magic" is in the EQ Networks was absolutely correct; so far all we've been able to determine is there's a power supply, pots, and I & O trafos.  Compare the Lang to the innerds of a Pultec and its hard to imagine all that packed up with inductors into those two EQ Network cans.

DY

 

[damnyankee]

A sidebar question to Lang:  Does anyone know anything about this company other than it was on Fifth Ave in NY and made everything from EQs to Tape Decks?  

Look at page 3 of this flyer (http://studioelectronics.biz/newsletters/64dec.pdf) from Dec 1964: Lang was also a distributor for Universal Audio.  Anyone else find this strange???

Don't forget to check out the complete line of Universal Audio products on page 7 including the 175B, 175BT, and 175TBT!

DY

 

[damnyankee]

Freed update:

Called Cliff again today, he pulled the folders for the EQ Networks but has been too busy to sit down and review them.  Said he'd get back to me in a day or so.

Stay tuned...

DY

 

[abechap024]

See if he could scan them!!!
Well if he could just confirm what components are in them that would be exciting.
looking forward to it
Abe

 

[MHanson]

Did this ever get any further?!? 

Michael

 

[Nobru]

Is there a schem for the Lang eq? This is A project ;-)

 

[abechap024]

Yes there are kinda schem infos...I found there were some missing holes that I haven't taken the time to quite figure out yet. No doubt somebody could though. Go fo it!

 

[creal]

Is there a schem for the Lang eq? This is A project ;-)

Yes it's A nice project like the plutec

Nobu your PM is full.
I try to contact you for the Ten81

 

[fazeka]

Freed update:

Called Cliff again today, he pulled the folders for the EQ Networks but has been too busy to sit down and review them.  Said he'd get back to me in a day or so.

Stay tuned...

300 or so days later: Any update on this?

 

[lassoharp]

Cliff told me he would send me specs for two unknown Freed PTs - this was over a year ago so I'm not surprised . . .

 

[fazeka]

Maybe DY (or someone else) can put a call in for follow-up?

 

[creal]

I started to work on the PEQ clone.
For the moment, i've done the PSU and the amp boards. The schematic i used is the PEQ-2A. I used the 32035 freeds transformer on i/o instead the original (#38165 & 38166) but they sound nice for me.
All works well

Now, it's time to do the eq network.
I just looking quickly the docs posted on the page 2.
So, i have some doubts about this notes.
If i look the hi cut section i just saw 3 freqs like the pultec EQPA, but the lang have 6 freqs.
Also, 6 caps on the Hi Boost for 8 freqs. first, i thing the some caps are coupled to get the correct values. But it's not the case when i look the pictures (Langpeq-12) posted by Biasrocks on page 3. All switches looks to have just one circuit???

The Bass section looks also wrong but i don't take the time to looking this part for the moment.

Maybe someone here have more informations about the EQ network or one original piece for retro...

to be continued...

 

[mitsos]

It's been a year! wow, you've gotten farther than me, I got as far as buying some transistors....

As for the filters, I'm not sure I would even bother trying to decipher those handwritten ones. Does anyone know the source?  Like you say the high atten is wrong, the frequencies match the EQP-1A and even the wire colors match a photo of a vintage pultec I found on my pc, but as you noted, they don't match Mark's original Lang.

hmm.. if we ask nicely, maybe Mark would do us a favor and measure his original Lang, we can probably get most of the cap values for the shelves with a simple LCR meter.  I'm not sure it will work on the high boost, but one thing at a time. 

good luck, nice progress....

cheers!

 

[creal]

It's been a year! wow, you've gotten farther than me, I got as far as buying some transistors....

As for the filters, I'm not sure I would even bother trying to decipher those handwritten ones. Does anyone know the source?  Like you say the high atten is wrong, the frequencies match the EQP-1A and even the wire colors match a photo of a vintage pultec I found on my pc, but as you noted, they don't match Mark's original Lang.

hmm.. if we ask nicely, maybe Mark would do us a favor and measure his original Lang, we can probably get most of the cap values for the shelves with a simple LCR meter.  I'm not sure it will work on the high boost, but one thing at a time. 

good luck, nice progress....

cheers!

I agree with you Mitsos, it's looks to be a EQP-1A network.
If i remember i found this note on the web( google is my freind) two years ago.

I ordered the inductors to chiron this year, today i play and looking around the network of the pultec network for basis.

For sure, it's will be better to have measure of an original PEQ2

 

[Biasrocks]

I'll do what I can to help out.

Unfortunately I don't have a way to measure inductance.

If you have specific positions that you want me to measure, fire away.

Regards,
Mark

 

[abechap024]

I'll do what I can to help out.

Unfortunately I don't have a way to measure inductance.

If you have specific positions that you wan me to measure, fire away.

Regards,
Mark

I have an inductance meter, but just judging how it wigs out when there is any capacitance in the signal path, I don't think we would find any joy by trying to measure the inductor/cap networks, unless someone can verify their are not caps or inductors connected together inside the cans?

I think our method of advance should be through the company... unless someone wants to take apart their lang, but that would be a shame.

 

[mitsos]

Mark, you rock!

the block diagram looks like it might be original, if so, then we know where to take measurements.

If the low boost/low cut/high cut are all shelves, there should be just caps on the other end of those wires, AND you can measure the caps. If you connect your DMM between the pole of each respective switch and the other side of the caps that are connected to the switch (other side of caps in each section should be connected together like in the pultec).

For example, to measure the low boost caps, put the DMM between the pole of the low boost switch and ground.  Then as you rotate the switch through each position, your meter will show the capacitance of each individual cap (this won't show parallel caps, but that's ok for now).

For low cut, one DMM lead goes to the pole of the switch, then (looking at the block diagram), the other lead goes to the HF boost/HF droop/LF droop junction.  (LF droop is mistakenly marked boost in this diagram... it's the one within the LF droop circuit). 

I confirmed the above two procedures with one of my EQP-1S5's, it works and gives accurate capacitance readings.  The high cut somewhat "worked"  but I consistently got readings 15-25nF higher than reality in each position, which could be my LCR meter or battery.  You would connect the DMM between the pole of the switch and the pot wiper.  I'll try this one again later with a new battery.

This is ASSuming th Lang block diagram is correct of course. Obviously if the switches are set up differently then it might take some detective work to find what's connected where, but it's still possible.

The high boost is another problem, maybe a better LCR bridge would measure it in circuit, but my LCR just gives me funky readings trying to measure the pultec high boost so I know my LCR won't work.  (old BK 875). 

I hope this makes sense, I tend to ramble! But if we can get these measurements we'll at least have the real LAng shelves.

thanks in advance mark!

 

[creal]

Prototype in progress...
All working well, the filter sounds good to my ears
I replace the filter bypass by a true bypass.
The filter network has inspired by the EQP-A with little modifications for use the simple and easy to find lorlin switches.
Also change the output transformer by a 600:600r NEVE VT24499 output transformer with zobel.

Actualy, i working on the PCBs
Stay tuned, to be continued...

Cyril

 

[damnyankee]

After my last call to Cliff, I left several messages to have him call me back. No luck.  If he and his guys couldn't build the High / Low Eq Networks, I was hoping he would scan a copy of he builds.  No luck on that either.  maybe he figured us for crackpots...who knows.

Just a thought:  If Pultec had 3 filters and Lang had 6, do you think Lang took Pultec's 3 filters and split them to get the 6 frequencies on the Lang???