helios preamp pcb's [boards now available]

[Joechris]

It was a Helios console that was ordered to somewhere here in Norway, so it was called the Arctic console
I dont now when or where, but in 1995 it was installed for a short time in a studio in Oslo, before it went abroad to somewhere.
It was a nice looking black and red console in a L shape. I had the schematics in my hands for a while when the console was in Oslo, and made some handdrawn
copys of parts I thougth looked interesting..No iPhones then..This console didnt have much headroom, pushed a little it had a nice rocky sounding distortion
that was very cool. I can try do digg up some more info...

 

[drummerjoe]

I'll take 4, I need a new Project!

 

[mus1k_freak]

Shoot me a pm if you you want a few  put you on the list

The early Helios were all discrete that looks like one of the later ones that used ic' s, the newer Helios eqs also used a ic make up gain stage

I'll take 4, I need a new Project!

 

[Joechris]

No, the "Arctic" console is all discrete.

 

[mus1k_freak]

Oh awesome was that some kind of op amp in the schematic? Crazy how Helios are all so different

No, the "Arctic" console is all discrete.

 

[kpearsall]

Just dropping by to say good job and good luck! I've had a few boards made for myself and a friend of a layout I did with both amp stages and the output buffer on a single board, but neither of us have finished yet, so I still don't know if they work I designed it to work as a stand alone preamp, or to interface with Ian's EQ board, with the intention of giving the design to the group for anyone to make their own boards. However, my pcb layout skills are quite amateur, and I never got around to asking for advice on it. I hope your boards work out well. I salute you!

 

[mus1k_freak]

Thanks! Hopefully after some trial and error with the first run of boards I'll be able to offer a  better second run,  maybe even 500 series version I'll have schematics, build docs and any info I've gathered available for anyone else that wants to tackle this,  should be a fun project!

 

[mus1k_freak]

Here is a link to a mouser cart with everything you need for the build, including the 120v to 24v transformer for the power supply, of course feel free to modify the cart to your liking but it should give you a good start http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=3772d0feb8

 

[mitsos]

any news?  ;D

 

[mus1k_freak]

boards should be shipping any day now just waiting to get rolling, got all my mouser parts in last week!

 

[mjrippe]

Here is a link to a mouser cart with everything you need for the build, including the 120v to 24v transformer for the power supply, of course feel free to modify the cart to your liking but it should give you a good start http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=3772d0feb8

Hi, just curious about some of the resistors.  There are a mix of 1%, 2% and 5% tolerances - are these critical?  Some of the 1% 50ppm are close to $1 each and if I can use regular 5% from the stock that I have on hand I'd rather not order those parts.

 

[mus1k_freak]

not super critical the cheaper ones should be fine, double check the size of the caps too, i may have order a few of the larger wimas instead of the smaller size, the values are all correct though 

Here is a link to a mouser cart with everything you need for the build, including the 120v to 24v transformer for the power supply, of course feel free to modify the cart to your liking but it should give you a good start http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=3772d0feb8

Hi, just curious about some of the resistors.  There are a mix of 1%, 2% and 5% tolerances - are these critical?  Some of the 1% 50ppm are close to $1 each and if I can use regular 5% from the stock that I have on hand I'd rather not order those parts.

 

[ruffrecords]

When the Helios circuits were designed, 5% resistors were all that were available.  Most commonly available resistors these days are in fact 1% tolerance simply because of improved manufacturing processes. I would suggest you get regular 1% types all round.

Cheers

ian

 

[mus1k_freak]

pcbs should be in this week! going through all my parts and sorting things out, i may offer kits if anyone is interested, hopefuly ill have the first prototype up and running by the end of the weekend, ill keep you guys posted!

 

[mus1k_freak]

told you guys i wouldnt forget about you! Boards finnally came in, makepcb takes forever, but they came out beautiful! if youve paid ill have them in the mail this week, if not and you would like a few boards check out the first post. i have 20 boards (thought i only had 15) so come and get em! should be a great little project, boards are about 4x3

Apple for scale 

 

[mjrippe]

told you guys i wouldnt forget about you! Boards finnally came in, makepcb takes forever, but they came out beautiful! if youve paid ill have them in the mail this week, if not and you would like a few boards check out the first post. i have 20 boards (thought i only had 15) so come and get em! should be a great little project, boards are about 4x3

Seven weeks later...

 

[mus1k_freak]

Ugh I know I've been real busy with moving and work I rarely have time to touch the iron. Things went out this morning if you're in the states you should have them by Thursday

 

[mjrippe]

Arrived today, thanks!  Next Mouser order should fill in whatever I don't have in stock...

 

[mjrippe]

So I finally got the parts ordered and had a minute to sit down and start this.  Should have gone over the schematic more carefully first.  Seems you got microfarads (µ) and nanofarads confused in several spots, possibly due to the way it was drawn on the line out schematic.  Specifically C4, C5, C10, C11, and C12 should all be in µf.  It also appears that C6 and C10 should be tantalum and C4, C5, C11 and C12 should be electrolytic.

Will keep plugging away and let you know what I end up with!

 

[mjrippe]

OK, so after comparing all the schematics from page one of this thread, I came up with this composite which includes the modified preamp stage, single frequency HFP (80Hz), and output stage.  My drawing does not show the power supply components because I am using an off-board PSU.  It *should* have all the correct values and polarities for capacitors.

I added the HPF for two reasons.  First, it is useful!  And second because it seems like it will influence the output stage as the 4K7 resistor provides feedback even when the HPF is off.  I chose just the 80Hz but you could do the 40Hz as well.

This circuit can be built using the Mus1k_freak PCB.  Simply substitute the cap values and cut the trace after C5 (now 47uf electrolytic) and run leads to the switch for the HPF.  Return from the switch to the junction of C10 (now 1.5uf tantalum) and R13.