[Igor]

Thanx. If someone have VTB9048 drawings with measures, can be great.

[Rob Flinn]

Colin at Audio Maintenance is normally pretty useful for supplying drawings for the Carnhill stuff !

[hobiesound]

Insert can be done with relay and active line receiver/driver....
This complicates a bit and requires +/- audio power supply instead of single + or - 24V
(depending on how old the Hel**s model is...)
Just a thought. Older Hel**s modules were using -24V supply. We need +24V for makeup stage (second half of BA283).
So, why not use +/-24V power supply and power from here switchable insert's balancing driver/receiver?
This way we have (if insert is "on") balanced micpre out and balanced input into EQ.
When insert is off, relay takes care of insert and sound does not passing thru balanced driver/receiver.

i might be the odd one out, but if you run the amp card on +24 you have a PNP on input which theoretically should be lower noise than a NPN. Not sure if that is still the case with modern transistors. I'm gonna be building 2 old skool style, i've got enough info/parts to build it more or less as authentic as possible. only difference with mine is probably gonna be the output amp which i'll be making balanced out. (still deciding on the options out there, so i'm watching this thread closely .

Still hoping to find some info that i don't already know. i was kind of disappointed when this thread turned into a ordering thread instead of a sharing info and learning thread... but then again that's the way this forum is heading lately.....

greetings,

thomas

[audiovisceral]

I agree with Keith, Why find trouble? it's a current product.

It's decades old. The patents for the original designs are long expired. The trademark still applies, but this is a Phaeton project, not Helios. This is no different from the UA 1176, LA2A, and G-SSL clones which are also  of current products.

And I agree with the others - mic and eq (plus di) in one is great, but only if we can also use the eq alone with line levels.

[hobiesound]

i don't understand the discussion whether to include a line input the original already had a line input.... although unbalanced but that can be solved in a number of different ways if need be.

[audiovisceral]

i don't understand the discussion whether to include a line input the original already had a line input.... although unbalanced but that can be solved in a number of different ways if need be.

Could we incorporate a little circuit we can switch in  to electronically (or transformer) balance this line input when the mic in is not being used?

Could be a nice modern upgrade.

[tommypiper]

...the original already had a line input.... although unbalanced but that can be solved in a number of different ways if need be.

I prefer to have unbalanced options when possible.  I suggest we have OPTIONZZZ    for unbalanced input and unbalanced output. 

[MikoKensington]

Could we incorporate a little circuit we can switch in  to electronically (or transformer) balance this line input when the mic in is not being used?

Could be a nice modern upgrade.

The idea mentioned a little while back was to pad the signal before the input transformer for line level. 

Perhaps Igor can layout the board in a way that can leave it up to the builder how far they want to go.  Like leaving off the preamp or keeping it and having solder points for an optional unbalanced in.  Which ain't my bag, but I can see how people may want it for mixer inserts.

[audiovisceral]

The idea mentioned a little while back was to pad the signal before the input transformer for line level. 

Perhaps Igor can layout the board in a way that can leave it up to the builder how far they want to go.  Like leaving off the preamp or keeping it and having solder points for an optional unbalanced in.  Which ain't my bag, but I can see how people may want it for mixer inserts.

The only problem with padding if I understand is to get a balanced line input, we're essentially having to run signals through the preamp a whole second time (40 dB pad to mic level, 40 dB gain back up to line), which might add coloration we don't always want.

I doubt Igor will be able to find a design that works for everyone, but I hope he will be able to develop a bit more elegant of a line/mic/DI in solution.

[MikoKensington]

...we're essentially having to run signals through the preamp a whole second time (40 dB pad to mic level, 40 dB gain back up to line), which might add coloration we don't always want.

Isn't color kind of the point of this unit?  If you want cleaner EQ, I'd elect to build something else.  There are plenty around.  

Going without the input stage of this is kind of like getting an old sports car, taking out the engine, having a tow truck pull you around everywhere, and telling everyone you drive a sports car wherever you go.  It sort of kills the point of the old sports car, doesn't it?

On the other hand... I love flexibility as much as the next guy, I'm just worried that adding too much could eventually take this so far way from it's origin it may not be worth the cost and effort.  

Igor, you're a smart fella.  I'm sure you'll do a wonderful job putting together something we can use with pride.  Cheers.

BTW.  I sent Colin at Audio Maintenance an email about the inductor dimensions. 

[drpat]

...

[MikoKensington]

Is that anything like putting a huge wing on the back of a front wheel drive Honda? 

I'm demo-ing the 500 series Helios in a couple weeks.  I'm curious to see what they sound like.  They're priced pretty well.

[Biasrocks]

I'm demo-ing the 500 series Helios in a couple weeks.  I'm curious to see what they sound like.  

Ah yes, those are pretty. What's the selling price on those Mike?

And there's the Realios Mic Pre's as well.

http://www.realios.com/

Mark

[strangeandbouncy]

Hi,


  as a current owner of several original helios modules, and a former owner od several other types of Helios modules, both active and passive eq's, I suggest that going in and out un-balanced is a good idea. I have tried several different trannies in and out, and I can honestly say that they sound best un-transform(er)ed. They sound loads better imho going unbalanced Line-in than Mic in padded. Just give it a try if you don't believe me. Strange, since the mic pres are pure sex! I only have modules with the tiny Beyer trannies at the mo, but I have had Lustraphone, and also some big Sowter inputs on my stolen Active 3 band eq's.(If it was you that stole them, I am coming to get you, and it is going to hurt quite a lot when I find you . . . . ) My life is NOT the same without them.

    Let me know if I can help!


       ANdyP

[Biasrocks]

And there's this beauty.

[MikoKensington]

Thanks for chiming-in Andy.  Good to know the EQ does have its "own" thing.  Have you ever seen the green Helios console made for Apple Records?  I was at VK the other day and they had a repair in from someone famous.  They looked like Helios modules but they were bright green anodized faceplates.  

Mark, any idea what those Realios are going for?  Vintage King is selling the 500 Type 69's for $1375.  Which is a lot for any 500 module, but perhaps these might be worth it.  

[audiovisceral]

 as a current owner of several original helios modules, and a former owner od several other types of Helios modules, both active and passive eq's, I suggest that going in and out un-balanced is a good idea. I have tried several different trannies in and out, and I can honestly say that they sound best un-transform(er)ed. They sound loads better imho going unbalanced Line-in than Mic in padded.

From your post I will skip the trannies. I feel uncertain about how good an idea it is to have unbalanced gear in an otherwise balanced studio, but if we want  balanced line input without using transformers it would be fairly easy.

All we need is a little circuit like this on the line input jack:



If people don't want the line input balanced, they could just bypass the circuit and wire the jack in to a given point directly after it. Simply as can be.

Then for the output, we could similarly have a simple balancing circuit like:



Those that want unbalanced out or transformer balanced out would again skip this little bit and take their output from a given point before it.

(figures from http://sound.westhost.com/project51.htm)

I don't design gear though and I don't know the Helios so I don't know if this would work. But it seems to make sense to me and seems simple enough.

It would only take up a tiny spot on the PCB if integrated. If it's not an integrated option, I think it would be easy enough to breadboard in.

[Biasrocks]

Isn't there a provision for a line input on the original schematic?

I'm certain I saw it there.

Ah yes, it looks like it bypasses the input transformer and goes into Pin 1 on Card 1.

Unbalanced isn't a big deal, you lose 6db but it's not like I need to run a signal to Cleveland and back.

Here's the first gain stage from the Olympic modules.

Mark

[Biasrocks]

1973 V69 schemo #1

[Biasrocks]

2003, V69 schemo #1

créer son PE1A

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