Helios thread

[ruffrecords]

I am in touch with one of the original designers of the Helios circuits. He told me that the 10H inductor did not have a spec as we would think of it today. The first units were made from a bunch of inductors purchased from a surplus store in the Edgeware Road.

Cheers

Ian

 

[ruffrecords]

I got some more info and a pic from my ex-Helios contact today. The bass inductor was made by Parmeko (see attached pic). it looks to be some kind of choke or plate load as it is specified as 4H at 22.5mA dc current but he measured it with no dc flowing and its inductance was 9.97 H which is very close to the 10H I use in my design. He said the dc resistance was 573 ohms.

Cheers

Ian

 

[Strat96]

Hi everyone. Hopefully it's not too late to join the conversation, but I can confirm that 10H and 12H were used in different versions of the Helios. There isn't a 'Holy Grail' recipe for the exact sound, because the company used what was available at the time and modified the design throughout the 10 years these were made. Certain combinations did sound "better" than others of course, but any gear lover would be happy with any of the Helios modules.

The schematic kpearsall posted is actually from my book. I purchased the Musicland Helios a few years ago, and have been working to restore it (a major undertaking). There are three EQ designs: v1 is Lustraphone Transformer w/ 10H Bass and 220mH/680mH mid; v2 is a Lustraphone  Transformer w/ 10H Bass 115mH/180mH/360mH/680mH; v3 is a Beyer w/ 12H Bass and the same mid from v2.

**Note the inductors are calculated based on the capacitors and freq in the schematics, as the inductor values never are listed.  12H works for all capacitors in v3, except the 60Hz boost would be in actual use an 80Hz boost based on the capacitor used. In other posts from people who know about the equipment, there is mention that 12H and 10H were both used for Helios. From the math anything from 12-16H would be in an acceptable range to work on v3 since nothing ever exactly lines up to the exact boost/cut frequency on a Helios.

 

[ruffrecords]

Thanks for the additional info Strat69. It is always good to hear first hand information. I am sure my ex Helios man would help you with your restoration. PM me with your email and I'll introduce you if you want.

Cheers

Ian

 

[warpie]

I have some free time and I was thinking of breadboarding the preamp to hear how it sounds.
I only have a spare Lundahl ll1538 mic tx (1:5) though.

I think the original had 1:10 tx. Do I need to change any resistors in order to get the thing working with the ll1538?

PS. I'm referring to this schematic which i believe is the right one?

 

[ForthMonkey]

Any info about Sowter 7490? There is no datasheet on website. I need to know pins and mounthing hole.

 

[Whoops]

Just to let everyone know that there are Lustraphone clone transformers available from 2 different sources.
Those were cloned by analyzing and  dismantling original Lustraphone transformers.

In my opinion the lustraphone clones are the best option for an Helios project.

Sowter makes great transformers, and Im sure the sowter transformer is high quality, although the lustraphones were very much part of the sound of this circuit, and they have a behavior that was not Sowter's intention to emulate. The Sowter transformer is overall better speced what might not be not desirable.
just my 2 cents

 

[Whoops]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

 

[ForthMonkey]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

Lots of info but nothing about transformer.Sowter 7490 is clone of Lustraphone M10.Needed datasheet.

 

[Whoops]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

Lots of info but nothing about transformer.Sowter 7490 is clone of Lustraphone M10.Needed datasheet.

You're wrong.
Sowter 7490 is not a Lustraphone Clone, its a replacement transformer.

 

[ForthMonkey]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

Lots of info but nothing about transformer.Sowter 7490 is clone of Lustraphone M10.Needed datasheet.

You're wrong.
Sowter 7490 is not a Lustraphone Clone, its a replacement transformer.

Yeah,you're right.My bad...It's a replacement transformer.But still there is no info about Sowter 7490 or Lustraphone M10.How to wiring?

I have no Lustraphone M10.So i have to find info about 7490.

 

[Whoops]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

Lots of info but nothing about transformer.Sowter 7490 is clone of Lustraphone M10.Needed datasheet.

You're wrong.
Sowter 7490 is not a Lustraphone Clone, its a replacement transformer.

Yeah,you're right.My bad...It's a replacement transformer.But still there is no info about Sowter 7490 or Lustraphone M10.How to wiring?

I have no Lustraphone M10.So i have to find info about 7490.

Ask Sowter they’re helpfull in providing info

 

[ForthMonkey]

Helios Schematics and documents, here:

http://groupdiy.com/index.php?topic=58393.0

Lots of info but nothing about transformer.Sowter 7490 is clone of Lustraphone M10.Needed datasheet.

You're wrong.
Sowter 7490 is not a Lustraphone Clone, its a replacement transformer.

Yeah,you're right.My bad...It's a replacement transformer.But still there is no info about Sowter 7490 or Lustraphone M10.How to wiring?

I have no Lustraphone M10.So i have to find info about 7490.

First of All,
when someone posts rare and difficult to find Technical Documents what you should say is "Thanks",
instead of coming here complaining.

Those documents were collected by me after 4 years of research, and Im sharing them with everyone, so I can help the community as the community helps me.

If you are looking for info about a Sowter product you shouldn't search for it in a Helios Technical Docs page, as there was never any Helios module with Sowter transformers, you should search instead in a Sowter Technical Docs thread, or even more clever contact Sowter directly.

If there is no Sowter Tech Docs thread, maybe you should get the information you need yourself and create a thread and post that information sharing it with everyone.

Sorry...

I've sent email to Sowter.If i get any info,i will share.

Thank you for all.

 

[ForthMonkey]

I've found color code for Sowter 7490.

http://www.sowter.co.uk/colours/7490.pdf

 

[Whoops]

My Lustraphone Clone transformers arrived today.

They are manufactured by Cyril Jones from Raindirk

He went to great lengths to be able to produce a Lustraphone clone, they look great.
Will test them soon in an Helios type Mic amp

 

[Whoops]

more pics

 

[J0hanne5]

I bought eight preamp modules and 15 eq modules those are pulled out from a Helios console owned by the Finnish TV channel called MTV3  http://www.helios-electronics.com/Mainos_TV_Finland.JPG
I started to reverse engineer the pre and found already an input, an output and a voltage pins so I can test the preamp (it will happen in next weekend).  However, any info about Helios modules is welcome!

My plan is to build a side car with 8 pre and eqs. The rest of the eqs I will put in rack enclosures.

 

[Whoops]

I bought eight preamp modules and 15 eq modules those are pulled out from a Helios console owned by the Finnish TV channel called MTV3  http://www.helios-electronics.com/Mainos_TV_Finland.JPG
I started to reverse engineer the pre and found already an input, an output and a voltage pins so I can test the preamp (it will happen in next weekend).  However, any info about Helios modules is welcome!

My plan is to build a side car with 8 pre and eqs. The rest of the eqs I will put in rack enclosures.

Nice Buy,
were the modules expensive?

What are the card numbers inside?

 

[J0hanne5]

Nice Buy,
were the modules expensive?

What are the card numbers inside?

Thanks! No, they were not I paid 500 euro from all of those.
I will post new info soon. Here is some pics https://drive.google.com/open?id=0B53QfYJWE3UVUUczOFo4bGxfSm8 The pre is fully discrete but the eq has one IC and there is no inductors.
The seller said that he might know a guy who has the rest of the modules and maybe the original manual!

Does someone know what is the type of those connectors? Maybe I should just replace them with connectors those are easier to find.

 

[Whoops]

Well if you know a source for more modules and dont want them all for yourself please let me know, I would buy a few.

Thanks