Rocinante
Well-known member
How we doing Pahstah?
HE-569 pre/eq 500 series
- Thread starter pahstah
- Start date
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Ricardus
WILL SOLDER FOR FOOD
pahstah said:
I've got some toes crossed, too.
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
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
Rocinante
Well-known member
So are we good to go?
Rocinante said:
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
Looking good! We really appreciate all your work on this.
Rocinante
Well-known member
Paolo you are killing it.
manulaudic
Well-known member
Wow that's looking very promising !
Winston OBoogie
Well-known member
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
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
pahstah said:
Do you have that oscillation also in the "oficial" reissue unit?
You are doing great work mate, thank you so much for sharing this
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.
pahstah said:
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
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
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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