Rocinante

Re: HE-569 pre/eq 500 series
« Reply #40 on: October 11, 2019, 12:02:51 AM »
How we doing Pahstah?
If there's a harder way to do this, I haven't found it yet.


pahstah

Re: HE-569 pre/eq 500 series
« Reply #41 on: October 18, 2019, 12:04:18 PM »
How we doing Pahstah?

building version 3, fingers crossed

Ricardus

Re: HE-569 pre/eq 500 series
« Reply #42 on: October 18, 2019, 12:40:15 PM »
building version 3, fingers crossed

 I've got some toes crossed, too.  :)
Audio mastering for hire..

pahstah

Re: HE-569 pre/eq 500 series
« Reply #43 on: October 25, 2019, 03:42:13 AM »
sooo...

the preamp works fine, no oscillation and a good amount of gain.
the eq works nice but i want to try to get closer to the original unit:
compared to a helios 500 (the reissued version now discontinued), the mid section eq curves in my version have an higher Q, so now i will try to find the right choice of inductance an capacitance with the inductor VTB 9048. I think the ideal inductor for mid bands would be VTB 9042 but unfortunately there isn't enough real estate on the pcb for that.
Also i've found that when the eq is activated a little ripple in the mid curves appears, let say half a dB at max frequency boost at 6.8 kHz, this disappear when the low band frequency switch is engaged, but is present in all the others switch position.
I think that this could be caused by the low frequency boost circuit not being terminated by the switch.

Paolo

pahstah

Re: HE-569 pre/eq 500 series
« Reply #44 on: October 25, 2019, 06:13:40 AM »
here is the plot of all the mid bands boost cut of my unit:


pahstah

Re: HE-569 pre/eq 500 series
« Reply #45 on: October 25, 2019, 06:15:55 AM »
here is the Helios 500 plot for the mid bands, notice that on some frequency the Q is lower


pahstah

Re: HE-569 pre/eq 500 series
« Reply #46 on: October 25, 2019, 06:23:40 AM »
Low boost comparison:

Top: He569
Bottom: Helios 500

40Hz


80Hz


120Hz


240Hz


400Hz
« Last Edit: October 25, 2019, 06:39:07 AM by pahstah »

pahstah

Re: HE-569 pre/eq 500 series
« Reply #47 on: October 25, 2019, 06:31:39 AM »
Hi Shelf plot

Top: He569
Bottom: Helios500

-2dB


-4dB


-6dB


-8dB


-10dB


+2dB


+4dB


+6dB


+8dB


+10dB

« Last Edit: October 25, 2019, 06:41:00 AM by pahstah »

pahstah

Re: HE-569 pre/eq 500 series
« Reply #48 on: October 25, 2019, 06:38:21 AM »
Mid Bands

Top: He569
Bottom: Helios500

700Hz


1400Hz


2000Hz


2800Hz


3200Hz


4500Hz


6000Hz

Rocinante

Re: HE-569 pre/eq 500 series
« Reply #49 on: October 30, 2019, 10:21:58 PM »
So are we good to go?
If there's a harder way to do this, I haven't found it yet.


pahstah

Re: HE-569 pre/eq 500 series
« Reply #50 on: October 31, 2019, 08:33:35 AM »
So are we good to go?

I'm going to design a version 4 pcb to open up the selection of frequency Q a bit, but ver 3 is good too.
now i have to find somebody here to do the L-bracket, the faceplate design is done.

input transformer is Sowter 7490e: on the online shop there's only the 7490f wich has a mounting boss, to order the one with the "e" suffix you need to send an email to softer when ordering.

output transformer is EA2623-1

inductors are VTB 9043 and VTB9048 from audio maintenance

pahstah

Re: HE-569 pre/eq 500 series
« Reply #51 on: November 01, 2019, 10:28:34 AM »
Getting there...

700Hz


1000Hz


1400Hz


2000Hz


2800Hz


3500Hz


4500Hz


6000Hz

OneRoomStudios

Re: HE-569 pre/eq 500 series
« Reply #52 on: November 01, 2019, 10:37:30 AM »
Looking good! We really appreciate all your work on this.

Rocinante

Re: HE-569 pre/eq 500 series
« Reply #53 on: November 01, 2019, 03:38:20 PM »
Paolo you are killing it.
If there's a harder way to do this, I haven't found it yet.

manulaudic

Re: HE-569 pre/eq 500 series
« Reply #54 on: November 02, 2019, 01:09:38 PM »
Wow that's looking very promising !

Re: HE-569 pre/eq 500 series
« Reply #55 on: November 04, 2019, 04:09:57 PM »
Your EQ is as good as need be Paulo.    Helios channels differed somewhat from batch to batch during the years they were built, and, within a batch, there were tolerance differences too. 
Also, most all the early channels used whatever inductors could be bought inexpensively on the surplus market and, from what I remember, don't measure exactly as "written on the tin"

IOW, you done good👍

Whoops

Re: HE-569 pre/eq 500 series
« Reply #56 on: January 18, 2020, 12:15:00 AM »
the main problem is oscillation above 70 db of gain with the 1:10 tap inserted, no oscilation with the 1:1 tap.

Do you have that oscillation also in the "oficial" reissue unit?

You are doing great work mate, thank you so much for sharing this

Bobby Baird

Re: HE-569 pre/eq 500 series
« Reply #57 on: January 27, 2020, 05:47:35 PM »
These look nice. I bet they would be perfect for guitars and drums. You would need these to get that reggae snare sound. Bob Marley used Helios consoles as well as Led Zeppelin and many others.

Whoops

Re: HE-569 pre/eq 500 series
« Reply #58 on: January 27, 2020, 10:11:03 PM »
the eq works nice but i want to try to get closer to the original unit:
compared to a helios 500 (the reissued version now discontinued), the mid section eq curves in my version have an higher Q

Hello Paolo,
remember that you don't know how much the Helios 500 series reissue is close to an original.
Helios doesn't exist for a long time, that reissue is just a name.

I remember a big thread somewhere were Helios experts talked about and compared all the Helios reissues/clones at the market at the time.
I remember big disagreements between the people,  some of the disagreements where about that Reissue module.

Let me see if I can find it
« Last Edit: January 27, 2020, 10:24:44 PM by Whoops »

Whoops

Re: HE-569 pre/eq 500 series
« Reply #59 on: January 27, 2020, 10:28:00 PM »
I found it,
there was an event called the "The Great Helios Listening Party Held"

https://www.prosoundnetwork.com/archives/the-great-helios-listening-party-held

The thread that had all the nice Helios photos and then ended with big disagreements.
It's a good read I liked it, but only for the hardcore Helios fans....

https://repforums.prosoundweb.com/index.php/topic,17863.2385.html


 

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