Lang PEQ-2A clone...RESURRECTED

[pucho812]

It's been a while. Did we get anywhere with this?

 

[jensenmann]

It's been a while. Did we get anywhere with this?

Did we?



... just to bump this

 

[Lee_M]

....

 

[wolcott]

ill bet damn yankee has  the product line in the works and has trademarked lang already 

 

[damnyankee]

Hail no!  I'm just a solderer - and a marginal one at best. 

Dandeurloo/Collective Cases designed the front panel early on, Chrion or Peter can probably do the inductors now that I got the  inductor schemos for us.  I was hoping Abe could do the pcbs with iron but I'm sure he's swamped with his own stuff.  So this will be sitting until one of you pcb board gods step up and get it all rolling.  Whoever wants to take ownership, its yours!

 

[Lee_M]

Has anyone made any progress with this project?

I just finished assembling a copy of the LLA-4 amp stage on stripboard. It's working well, has lots of gain and sounds very nice...Particularly in the bass frequencies!
I'm just using it as a line amp for a synth at the minute, Haven't got round to building any of the passive EQ circuitry yet.

I can take some pics and try to make a digital version of my stripboard layout for uploading here, If anyone's interested?

By the way, Does anyone know what we're supposed to "select" for when choosing the 1.73MΩ Q1 base bias resistor? The closest I had was 1.8MΩ. Seems fine so far...

 

[Lee_M]

My camera ain't the best, But here's a couple of pics of my boards...

I decided to use a board mounted 10k trimpot instead of an externally mounted pot.
Seemed more elegant, Plus it's one less thing to worry about mounting inside the box.

 

[salomonander]

the user Forthmonkey did design a pcb for the output amp. he even sells them.

 

[Lee_M]

I've been running my amp boards from my bench PSU for testing, But now I want to build a dedicated PSU for them....kinda-based on the original Lang PSU.

From what I can tell, the original has the 2n3054 mounted on the rear panel.
If I go with the 36VAC transformer with full wave bridge rectifier (As PRR suggested towards the beginning of this thread), Will I need to use a heatsink for the 2n3054?
I haven't built a PSU using discrete transistors as regulators before, So any guidance would be greatly appreciated.

If so, Can anyone suggest a minimum size (max thermal resistance, I guess) to look for when heatsink shopping?

One other thing, Is there anything else I'd need to consider if I was to use a 2n3055 in place of the 2n3054?
I have some smallish To-3 heatsinks (and a fair few 2n3055's) on hand, Whereas To-66 heatsinks seem much less common and I'll need to order one.

 

[rascalseven]

The links to the filter network information photos damnyankee posted on the previous page are no longer active.  Does anyone have these pics?  I just stumbled onto this thread today and would like to help push this to completion if possible. 

Perhaps someone could post those pics to the Lang page of the Technical Information forum?

Thanks so much!

 

[Lee_M]

They're already in there, aren't they?

https://groupdiy.com/index.php?topic=48881.msg759156#msg759156

 

[fazeka]

The links to the filter network information photos damnyankee posted on the previous page are no longer active.  Does anyone have these pics?

Add-on for Firefox or Chrome, respectively. FWIW, I've tried successfully for the latter...

https://addons.mozilla.org/en-US/firefox/addon/photobucket-fix/

https://chrome.google.com/webstore/detail/kegnjbncdcliihbemealioapbifiaedg

 

[fazeka]

Some(what) bad news...?

Background: I was reminded of this thread when I saw a recent (series of) post(s).

I was inspired by the specs provided by ETC and posted by damnyankee back in 2014.

I decided that if there's any chance for these filter networks to be built, minimally, we would surely need the inductors.

So I emailed ETC and asked:

"We are in need of some inductors. OEM was made by Freed Transformer, who I assume was purchased by the current ETC. Hoping you have the specifications to recreate these inductors?

Coil, 267mH (taps at 212mH, 157mH and 92 mH), Freed #36641-I
Coil,  84mH (taps at 72mH, 62mH and 40mH), Freed #36642-I

Hoping you can advise on this?"

This was the response (it was no other than our Cliff that responded to the email) I got:

"These two items 36642 and 36641 have not been made since 1968 and are not available"

Are we dead in the water?  :'(

Funny how (seemingly?) receptive he was over 4 years ago...

 

[pucho812]

For simplicity sake can't you just make a pultec and have the frequency select switches separate for boost and attenuate?  Or is there that much a difference between the Lang and pultec?

 

[fazeka]

Sure, but then we might as well just do a solid-state Pultec. 

 

[groselicain]

Getting back to the question, though, are the Freed components the only hurdles left? Was Abe or someone else able to work out a PCB? This is one project that I would simply die for considering the going rate these are fetching here in 2018.

 

[Lee_M]

I've got a PCB designed for the LLA-2 amplifier board, it plugs into a 10-way 3.96mm card edge connector (somewhat similar to the original LLA-2) and features an onboard trimmer for gain adjustment. I'm in the process of putting together some LLA-2 kits (including LLA-2 pcb, amplifier components and edge connector socket) which should hopefully be available in the next couple of months, possibly sooner if there is much interest.

Transformers and inductors could be dealt with in a number of other (cheaper) ways, assuming you're not fixated on using parts that are direct clones/replicas of the originals.

I'm using mine with a modified Pultec circuit (albeit with some modified/extra frequencies), it should be relatively simple to transpose the Lang PEQ2 cap values onto a turretboard/p2p Pultec filter circuit.  I'm also using UTC A-20 transformers; Input TX is wired for 500:500 and output TX is wired for50:500, the prototype sounds great.

I'm sure one of our resident winders on here can put together some suitable inductors.

A cheaper TX option could be Carnhill VTB2281 (600:600) for input and Carnhill VTB9057 (50:600) for output. The Carnhill transformers have higher headroom (30dbm iirc?), so they might be a better performing option than the UTC A-20s. The very slight differences in ratio (50:500 vs 50:600) on the output TX can be accounted for with the LLA-2 gain trimmer.

I'm based in the UK, so could possibly offer an optional set of Carnhill transformers (at cost price) alongside LLA-2 kits, that would offer a slight saving on postage for non-UK residents who want to use the Carnhill option.

 

[Lee_M]

Come to think of it, I could possibly look into putting together some of the other parts of this unit.

There are two routes I can think of;

1) We abandon the original aesthetics and use a turretboard (for filter section caps and resistors) with canned inductors (possibly chassis-mounted using either aluminium angle or capacitor clamps?), I could get some sheets of Tufnol cut to a suitable size and drilled (or maybe use something like this, if the layout will conform to the available sizes) and I could get a bulk lot of turrets to offer sets at cost price.

2) We stick with the original aesthetics and house the filter components in big cuboid cans, mounted on the rear of the unit.  Something like this .

 

[Lee_M]

I managed to track down knobs which seem to be the originals.

It's kinda hard to tell which size we need based on just photos, but I'm fairly sure it's either #8005 or #8010 by Davies Molding.

I'd guess we need the 8010, but it would be handy if someone can confirm that.

Allied has both types available relatively cheaply, although quantities are limited at the cheaper price.

https://www.alliedelec.com/davies-molding-8005/70097837/

https://www.alliedelec.com/davies-molding-8010/70097838/

Galco has them both available for very good prices in bulk, possibly worth a group buy?

https://www.galco.com/buy/Davies-Molding/8005

https://www.galco.com/buy/Davies-Molding/8010

 

[dandeurloo]

The tricky thing is the tx's.  Everything else will be pretty easy.  If someone had the TX's good or bad I could recreate them.  That seems to be the hold up on this project.  I have the case design ready to go still!