Helios 2128 + 22113 build attempt

[Squeaky]

I thought I'd post a couple of pics of a prototype Helios pre/eq that I recently completed (well the pre and eq are completely functional). This build attempt was inspired by some of the pictures of early Helios modules floating around this site and others. The boards in those early pictures looked pretty "hand made", which gave me confidence that I could try and knock it together on my desk.

This is certainly not an attempt at a replica, I added a line input transformer (original line input was unbalanced without a transformer) and an output transformer. I also added a few extra mid-eq points (I used a 12 position switch and a multi-tapped inductor, what was I supposed to do with those spare switch positions?)  The gain switch has also been changed to 5dB steps.

The input preamp (2128) voltage rail is at +24V and the output (22113) at slightly over +30V, which seems enough headroom (for me) for the output. It is pretty loud. With the power section I have in place, a higher voltage for the output is possible (with a change of a couple of resistors) but I am not sure I'll bother.

I think it retains a bit of Helios-ness. I recorded myself playing the intro to "Over the Hills and Far Away" through it and it completely fooled my wife. My wife is not the most astute audio analyst you say? Well, probably true that (no disrespect).

The front panel is not going to win any beauty contests (recall it is a prototype), and I always end up with stuff back to front (I put it down to being left-handed). However, aesthetics, and knobs going the wrong way, aside, it is my new favourite pre. It has low self-noise, sounds great, and I can see it getting a lot of use.

Thanks to all those who provided information about the 22113 line amp and all the interesting Helios discussions to be found here. I've greatly appreciated it. This site is unparalleled for the knowledge and expertise to be found. Thanks also to Joe Malone for his help with the power section.

 

[Squeaky]

Front panel-ish.

 

[ruffrecords]

Great effort.  Well done.

My wife reads a lot of magazines about interior design and in many of them one of the current trendy things is to have items that are 'shabby chic' - basically vintage stuff that is all scuffed and tatty. I reckon your front panel would make it into one of these magazines  ;D

By the way, the enclosure is interesting. It look very similar to many pro channel modules. Where did you get it?

Cheers

Ian

 

[Squeaky]

Thanks Ian,

Reading your previous posts about the high line level amp was very helpful when I was putting this pre/eq together. There really isn't that much information available (for public view) about this card. It does seems to work in the application, as you previously suggested it would. I have limited analytical capabilities (except for some somewhat tired ears from too much loud electric guitar) so I can't comment much about technical details (high frequency oscillations, etc).

When mixing an album with friends recently, we did a tone test. I don't think any of us could hear past about 16k.

The enclosure is an off-the-shelf item from Hammond. Part number is 1441-29BK3. It is a 2" x 10" x 12" enclosure and a cover is available. I'm not sure, but think I the dimensions are non standard for channel modules (too wide)? Since I'm just doing it for myself the (extra) width doesn't bother me (makes fitting an output transformer relatively straight forward) and if I get around to building a few of them, as planned, it is easy enough to mount the modules into some sort or frame, probably with a shared power supply for the remainder. Maybe some faders? Meter bridge? Pan? Aux send? Buses? I haven't worked out in my head how to do all of this yet, so maybe I'll get no further than building a couple more pre/eq modules and leaving it at that. It is one thing to build stand alone modules, another thing entirely to integrate them. I get the feeling I'd be biting off far more than I can chew.

I have all the resistors, capacitors and transistors for about 16 modules, and I'm quite excited about how the first one turned out so who knows? The greater cost, of course, lies with the transformers, switches, &c.

Again, since I'm just building this for my home studio I can live with (and somewhat wryly appreciate) the "shabby chic" aesthetic. If I settle on a layout (this one worked ok), then I might get some panels engraved, which will no doubt ruin the whole vibe!

Cheers,

Nick

 

[leadbreath]

very nice...

 

[Rocinante]

I forgot to mention how great I thought this is. Good job man.

 

[Whoops]

Nice one,
Love the handmade looks on the boards and the module itself.

So how did the 2128 board work with the 22113?
How much gain in total with the 2 boards?

was there any balanced output in an Helios console?

 

[Squeaky]

Hi, thanks for your comments and apologies for the late reply. the whole (home) studio has been packed up for a few months due to a big move, so I haven't been able to do any more than the initial rudimentary tests. That being said, I was pretty happy with the initial outcome, I though the boards worked well together. I thought that there was plenty of gain and headroom (I did recording tests with an acoustic guitar and a dynamic mic). I haven't really made it behave too impolitely yet, but I will.

I'll also try and do some audio spectrum frequency analysis at some stage but I'm not really set up yet to do robust technical analysis.

When I am settled I'll look into it a bit more. I have parts for additional channels, with different transformers though. I'm a little intrigued by the possibilities.

There are many others better placed than I to comment, but I'm fairly confident there were never output transformers on individual channels on Helios desks, so what I have made is far from Helios authentic. There was probably a bay of OTs somewhere on the frame for bus/stereo out? The Helios desk topology is a bit of a mystery to me and no two desks were probably the same anyway.

No doubt there will be some tweaking down the track, when I get my stuff back!!

 

[Whoops]

There was probably a bay of OTs somewhere on the frame for bus/stereo out? The Helios desk topology is a bit of a mystery to me and no two desks were probably the same anyway.

In all the documents on Helios consoles I've seen, I never seen an Audio transformer besides the Mic Input.
For all I know there was never any output transformers on Helios desks. It seems all Outputs were unbalanced. These consoles were used mainly in music recording studios and never really went into the Broadcast industry, so that might explain why the outputs were unbalanced instead of transformer balanced.
If anyone knows more info please let us know.

As for as Mic input transformers, originally they used Lustraphone , then Beyer BV 35600 (1:20), and I've read somewhere that Sowter 3374 and 3773  could have be used in some modules but I can't confirm that.

 

[Squeaky]

You are probably correct about the Helios desks being completely unbalanced, I just outright don't know. All discussions around the 22113 indicate that it could drive a transformer, not that it ever necessarily did though.

I think I also read somewhere that Sowter transformers were used in some later Helios desks, after the period when the little Beyers were used maybe?

As has been widely discussed, there is a fair bit of attribution of the original Lustraphone input transformer to the sound of the "classic" Helios module. However, Beyer module owners are also very happy.

I used the Sowter 7490 in the first build, I've always been happy with Sowter transformers so it seemed like a good place to start.

I have Jensens and Cinemags to trial. I was really keen to get hold of a couple of input transformers from Cyril Jones of Raindirk but I might have asked him a little late in the game and I think I caught him on the verge of retirement.

 

[Whoops]

You are probably correct about the Helios desks being completely unbalanced, I just outright don't know. All discussions around the 22113 indicate that it could drive a transformer, not that it ever necessarily did though.

I think I also read somewhere that Sowter transformers were used in some later Helios desks, after the period when the little Beyers were used maybe?

As has been widely discussed, there is a fair bit of attribution of the original Lustraphone input transformer to the sound of the "classic" Helios module. However, Beyer module owners are also very happy.

I used the Sowter 7490 in the first build, I've always been happy with Sowter transformers so it seemed like a good place to start.

I have Jensens and Cinemags to trial. I was really keen to get hold of a couple of input transformers from Cyril Jones of Raindirk but I might have asked him a little late in the game and I think I caught him on the verge of retirement.

I bought some Lustraphone clone transformers from Cyril Jones not so long ago, he was making more at the time

 

[Cyril Jones]

Hi, Interesting read, Lustraphone transformers v Cinemag and Soweter. having read a few referrances to me here's an update.  I have removed and supplied loads of transformers from Tony's re-issued Helios modules (Sowters) for mine. In the process of supplying a few again.  These with a supplied bracket fit neatly into the re-issues.  Interesting to see some of corrections and the phase change pcb in those type 1 pcb issues in the earlier re-issue modules. [email protected]

 

[Whoops]

Hi, Interesting read, Lustraphone transformers v Cinemag and Soweter. having read a few referrances to me here's an update.  I have removed and supplied loads of transformers from Tony's re-issued Helios modules (Sowters) for mine. In the process of supplying a few again.  These with a supplied bracket fit neatly into the re-issues.  Interesting to see some of corrections and the phase change pcb in those type 1 pcb issues in the earlier re-issue modules. [email protected]

Hello Cyril,
thank you so much for joining.

I never used a Re-issue module,  what was the phase change and pcb issues in the re-issue first modules?

thanks

 

[Squeaky]

Hello Cyril,

Thanks for your comments. I checked my email history and about three and a half years ago someone at Raindirk indicated that you were more or less retired. However, I'm glad to know that your input transformers are still being manufactured (although I am not personally in the market for any at the moment).

I wasn't sure if the Helios reissues were still being manufactured? I sadly read recently that Tony Arnold passed away (RIP).

Regards,

 

[beatnik]

Hi, sorry to hijack your thread. I am building an eq based on the Helios 69 circuit and I am looking for some advice regarding the amplifier section.

I have some make up gain pcbs based on the 2128 amplifier card (schematic attached)

I have to choose suitable input / output transformers. Can you point me out what sort of ratios should be used ?

All I know is the Helios channel used a 1:10 input transformer and the output was unbalanced.

Also I am unsure wether my make up amps pcbs need extra components to connect an output transformer ?

 

[Whoops]

I have to choose suitable input / output transformers. Can you point me out what sort of ratios should be used ?


Also I am unsure wether my make up amps pcbs need extra components to connect an output transformer ?

I think to drive an output transformer you need to add the 22113 output card as been said here that the 2128 can't drive the output iron.

As for tansformers, I would recommend you to buy lustraphone clone transformers from Cyril, then you have the correct thing for the circuit.

These are the specs from Sowter for their 7490 transformer, that can replace the original Lustraphones (it's not a clone per se):

7490 Helios Input transformer Lustraphone M10      1:10, tap for 1:1 200/20K  _9 dBu

 

[Rocinante]

Yeah you need to add the 22113 for balanced out. Helios didn't do this.  I will say Cinemag in to 2128 to 22113 to Cinemag out works well. Some modifications and it's also a damn cool di.

 

[beatnik]

Is there a verified schematic for the 22113 ?

I have found quite a few different versions with various changes.

Would be great if someone can point out to a good schematic.

 

[ruffrecords]

Here is the one I have have. Is is on Helios drawing paper so I guess it should be legit.

Cheers

Ian

 

[Squeaky]

Hi Rocinante, I've read a few things about the Helios DI but I've never seen a schematic. Are you willing or able to elaborate at all on the DI modification you mentioned? Cheers.

The above-posted schematic is the one that I have used.