Re: He-69 build/support thread. PCB's/kits-available!
« Reply #120 on: March 12, 2014, 06:36:29 PM »
Good stuff. I think the silkscreen text refers to the inductors that Igor wound (and originally provided with the kit).

Re: He-69 build/support thread. PCB's/kits-available!
« Reply #121 on: March 13, 2014, 10:33:08 AM »

Just finished a pair of He-69eq's ,using the line reciever and Whistlerock Ml918 DOA's using 47k resistor in r6,r7 and r8 for 24v operation ,they sound great,also have a pair of the hybrid amps using opa604 opamps,used 12v relays with 100ohm resistors which work ok ,for r12,r15 i used 25k, 5k and used sockets so i could change the values.i installed the carnhill 9048's the wrong way round after a quick desolder i was back on track and the eq's sound good 8) .


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #122 on: March 13, 2014, 11:10:16 AM »
Looks great - is that in a 19" rack using the rackit?

Any choice of a 'full frontal' shot?

Looks like you managed to find some 2 deck 12 position grayhills...digikey or elsewhere?

I'm glad it worked out well for you.

Re: He-69 build/support thread. PCB's/kits-available!
« Reply #123 on: March 13, 2014, 11:46:08 AM »
Yip ,Digikey ,had to pay some import tax on the switches though,which was a pain!!


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #124 on: March 14, 2014, 06:38:34 AM »
Impressive stuff chris77! ;) Good to see people getting their He69s working...hoping to do the same once my digikey shipment arrives... (got another week to wait...)



Re: He-69 build/support thread. PCB's/kits-available!
« Reply #125 on: March 14, 2014, 07:05:58 AM »
Hey people.

As I'm still twiddling my thumbs waiting for parts to arrive to finish off my He69s, I thought I'd take a look at the relay/switch stuff, as looking through the thread it seems to be a point of confusion and I wanted to get on top of it myself.

First a disclaimer. I have literally no clue what I'm doing and so I'm just doing my best to understand things as I go. The following info is how I see things, and hopefully someone smarter than myself can tell me if I'm on the right path or not. Additionally, none of this is tested yet, but hopefully soon.

(Oh, and I know I could just wire things up by looking at the pictures, but I don't want to do it that way...I'd like to be able to understand why stuff works if at all possible... ;) )

So, first thing to note is the way the circuit seems to be set up. That is, it seems to be that Igor configured it for minimum energy consumption for his common case... (well, that's my theory!)... that's why the default is for the EQ to be IN when the relays aren't being energised and the PRE is also IN when it's relay is not being energised.

Relay BYP1 -> Switches between audio IN & pass through.
Relay BYP2 -> Switches between audio OUT & pass through.
Relay BYP3 -> Switches between PRE & EQ.

Now I've never seen an original kit, so I don't have any idea of what this PRE business was about. The info that follows is just designed to help people that want a simple IN/OUT setup without the optional PRE. If I'd have given this more thought before ordering my relays, I probably would have left out BYP3 and just hard-wired it to ignore that stuff, but as it's too late for that, I'm just going to wire the switches to bypass the PRE with the knowledge that I could always experiment with something later...

And now an attachment to show how I think things should probably be connected, and the reasoning behind it. Hopefully I'm not talking crap right now...



« Last Edit: March 14, 2014, 11:02:06 AM by taliska »


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #126 on: April 12, 2014, 09:45:29 AM »
Hey all.

A quick post to show people my (kind of) finished He69s along side my other EQs and also a request for a bit of advice on tracking down sources of distortion in the build.

Anyway, I spent some time last night putting my various EQs (EQNs/studer169s/he69s) through their paces as I haven't really had much time to use any of the stuff I've been building. I just sent sent some tracks from Logic out to each of them and back again and played with the knobs a bit to see what was possible. The good news for me is that they're all quite usable and seem to occupy different niches.

Obviously the studer 169s are the simplest ones and so unsurprisingly the ones that are best calibrated (less to go wrong!). Using those reminded me that the EQNs aren't actually properly calibrated yet. I'm going to need to get an oscilloscope before I can do that (will be starting an advice thread in the lab for that shortly).

The EQNs obviously don't need any introduction as they get a lot of love around here. Calibration excluded (the real world effect of which was differing output levels), they're obviously quite powerful EQs. Sound good, look good. I think the only negative I have with them is that they can be a little bit intimidating because of the number of controls. I have to force myself to imagine there are fewer controls than there really is so that I don't over-sculpt.

The He69s IMO are the perfect sweet spot...when they're not distorting that is. Like someone mentioned earlier in the thread, I have to drop the level going to these by -20 db otherwise it's too hot for them. I haven't rushed this build, have had zero failures and feel like I've understood more than with other projects and on top of all that, they worked first time. This makes me think that my particular combination of I/O and DOA options has some undocumented problem/workaround that is required. Still, without that workaround in place, I really liked the level of control these EQs afforded. Not overwhelming and the high shelf is pretty tasty and the lo boost is pretty impressive.

Anyway, a picture is attached for those that like eye-candy. Now to talk about the distortion problems and working out how to fix them:

There are three possible configurations:

- transformer based I/O (pic shown in first post).
- transformerless I/O (other pic shown in first post).
- hybrid (never shown and the one I'm building: That1246 -> Cascode DOA ->LL1517 configuration).

I used the appropriate resistors for the cascode DOA as Igor suggested at the start of the thread (2k49, 511R).

I've had a quick look over the schematics and I'd like to answer the following questions if possible:

- Igor doesn't populate R10 in his examples. Looking at the schematic is looks like it's for smoothing out pops when using the mid-grayhill and without this there is no connection to audio ground. Surely this should be populated? Any ideas for a sensible value? I'm pretty sure things were popping last night when I was using it, so it would be nice to resolve that while I'm troubleshooting things.

- In Igor's builds in the first post, for the transformerless one where he's using his cascode DOA, he doesn't populate C8 (150 uF) and bridges it instead. Why? Could this be the source of distortion in my build? I've populated it as he never says not to.

- How did people trim their cascode DOAs with the onboard trim pot? Using a similar method to the F76 procedure? If this was set wrong, would it produce distortion? (it's for adjusting the DC offset, right?)

And finally...can anyone comment on what the most common sources of distortion are in these kinds of circuits?

If no one can think of anything useful I should do, I guess I'll probably pick up a cheap oscilloscope and try probing to find out where the distortion creeps in to the audio path...


« Last Edit: April 12, 2014, 05:28:17 PM by taliska »


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #127 on: March 26, 2015, 10:09:47 PM »
I will start this project soon although Igors documents link "http://ij-audio.com/downloads/HE_69.rar" doesn't work anymore.

Could anyone please share those documents or send them to me by email?

thank you
« Last Edit: September 02, 2015, 09:09:58 PM by Whoops »


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #129 on: March 27, 2015, 11:15:07 AM »
For the cascode doa where did everyone find the 2N4249?
What is a suitable alternative?
Internet is flaky would 2n2907 work?  Seems close right?
If there's a harder way to do this, I haven't found it yet.


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #130 on: August 30, 2015, 06:02:12 PM »
Time for an ol' fashioned thread resurrection...

I've been piecing together a pair of these for a while, and finally got everything situated and in place for one of them today. Since this is a more complicated project without official support, I thought its probably smart to build one all the way and get it working before starting on the second.

I'm happy to say everything works except for the relay business (more on that below) and, after a little initial testing, everything sounds good!

It's a pain to track down all the necessary info for this build, so I figured I'd list off my configuration and TBD values.

+/- 16v for 500 series rack
Cut off 51x fingers (not neccessary), jumpered jp1/2 - this sends the +/- 16v to the DOA(s)
Transformerless input using THAT 1246
Transformer output using Lundahl 1524 - bought a pair from Andre on the black market, he might have more
R14 = 2k, per BOM notes 2-3k
R13 = 200r
C10 = 4n7    Couldn't find any data from the ll1524 data sheet, so used BOM notes
DOA = gar1731
R12/15 = 24k9/5k1 for 1:2

Now, on the relay business...
I populated the relays for BYP1 & 2, left BYP3 out as this seems to be for the mic pre insert
Hardwired the BYP3 relay footprint to ignore the "to mic pre" traces
For switch, using SPDT on-on with BYP1 connected to top, BYP2 connected middle, NC on bottom
I'm using TX2-12v relays, R10 = 100r

Right now it's always in, so not sure if that means the relays I chose are energised/working or not. I'm assuming my issue is that I can't ignore the BYP3 relay and switch position altogether... I'll play around with a few things and report back findings.

I also wound my own inductor on an rm8 core for the mid-band, using the carnhill for the low band.  First time winding an inductor, so I'm really happy that A) it's working, and B) seems to be working as intended. I'm currently using a n87 400 core, but I think I'll try a n48 400 core for the second of the pair. Looks like that's the core that Carnhill uses for their rm8 inductors, so it'll be interesting to see if there's a noticeable sound difference.

More to come.
« Last Edit: August 30, 2015, 06:06:44 PM by Krcwell »


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #131 on: June 02, 2017, 08:44:15 AM »
FYI new location for docs & supporting files:


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #132 on: January 22, 2018, 02:13:30 PM »
New He69 PCB's in stock:


New lower price for our new site :D


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #133 on: August 01, 2018, 08:06:28 PM »

It's my understanding that there is a 6db loss when using the balanced line receiver, as the That1246 is a 1240 series component, and the 6 means -6db of gain. There are other 1240 series ics available, but the 1246 seems to be the best for input headroom.


I'm having some issues with my Helios!
I've used;
- ML918( used 47k for +/-24V)
- LM317
- LL1524
So everything works so far so good but when the unit is engaged there is -6db loss. I've checked everything twice and read igor's notes but I lost my mind :-\ ! as igor never sent me back my 2 finished units so I've started to building another pair but I'm not sure if it was a good idea... btw I'd like to fix this issue!
The second issue that I'm having is that the MID is not doing anything? when I turn the knob so nothing goes there... again! I've checked all capacitors twice and nothing wrong with them :-/
Please let me know if you have any idea why I'm getting-6dB when unit is turn on and why the MID does nothing?


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #134 on: August 29, 2019, 12:08:09 PM »
Is there any support for these boards? I'm very interested in a 51x EQ but don't want to dive into anything too old. Thanks!

Bobby Baird

Re: He-69 build/support thread. PCB's/kits-available!
« Reply #135 on: April 11, 2020, 01:13:11 PM »
I have a pair of these on the bench right now. I was wondering if I can get a consensus on which grayhill switch version people used on the high and middle frequency bands. The BOM states to use 2 x "71ADF30-01-1-AJN" 1X12 grayhill rotary switch's the non-shorting version, but on the silkscreen on the PCB says to use 2 x  "71ADF30-01-1-AJS" 1X12 grayhill rotary switch's the shorting version. Unfortunately, I have already purchased 4 non-shorting versions. I'm sure they will work. I'm just concerned because I have read on the thread that people have experienced pops when switching frequency points. Also, I'm running 16 volt with "that" receiver, a "Gar 2520" booster, and 1524 output transformer. Right now, I have R12=24K9/R15=5K1, R14=604,  C7=33pf for the TBD values. I don't really understand how I'm suppose to choose a value for C7. There was an example from the BOM which states


Based on this example value of R12 in my case 24k9, I approximated using an RC calculator to come up with 33pf for C7 based on R12=24K9.
To my understanding the ratio of 25/5.1 for R12,R15 sets the make up gain for the 2520 op amp for use with the output transformer 1:2 output ratio. Just a bit confused on C7?

Any insight from previous builders would be appreciated.


Re: He-69 build/support thread. PCB's/kits-available!
« Reply #136 on: July 26, 2020, 05:53:25 AM »
Hi Bobby,

I am about to start stuffing my PCB's.
-Do you happen to have an original copy of Igor's BOM (a ...bom.txt file) or even the complete rar package Igor put up on page 1, that you could share?

My email: rogydoggy -at- telenet -dot- be

Many thanks!

Best regards,



Re: He-69 build/support thread. PCB's/kits-available!
« Reply #137 on: July 26, 2020, 07:16:09 AM »
Hi Rogy
I sent you the docs to your email.



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