AION Blueshift Headroom

[micmac]

Hi all,

Happy new year!

I built a Blueshift over the holidays from a kit. I like the modulation a lot actually, sounds great. But I'm running into a headroom issue: when I dig in it clips.

I've made a recording with my mobile. It's not a good recording, sorry for that. I don't have a microphone. And also my amp isn't 100% clean either (Marshall), so it may sound like there's clipping with or without Blueshift engaged.

But when I connect headphones to the Blueshift's output I can hear no clipping when it's in bypass, but it's audible when it's switched on.

I've read on the internet already a couple of times that the Dimension C had some headroom issues. But not owning the original I don't have a possibility for an A/B comparison, sadly. So I'm not sure if my Blueshift works as expected or if there's a problem that can be fixed somehow.

My guitar from the recording is an Epi 1958 Explorer (2022/23 model) with stock Gibson Burstbucker pickups. So not particularly hot pickups I'd imagine, but humbuckers nonetheless. In the recording I used the bridge pickup. With the neck pickup the clipping is less. I have also a Dean 79 ML (Korea) with stock pickups. They are hotter in my opinion, which makes the Blueshift clipping worse.

I also have an Aion Azure (like a CE-2), where I used the same 3207 BBD I have in the Blueshift and that doesn't clip. I biased both pedals with the same scope.

I used the opamps suggested in the build doc, OPA2134, TL072 and TL022. I also replaced the OPAs with TL072s I had, but no difference.

Sorry for the long text, but it's driving me nuts a little bit, because I like the modulation a lot so I really want to use the Blueshift, but the clipping is a turnoff.

I read here on the forum that R9 influences the volume, so maybe I try changing the resistor to see if that helps.

Can anybody with a Blueshift tell me if their pedal is also not doing so great in the headroom department?

Kind regards,
Seb

[jimilee]

Very nice! I keep looking at mine, but it just gives me anxieties every time I do.


Sent from my iPhone using Tapatalk

[micmac]

I'd think somebody with over 11k posts wouldn't even blink building this pedal 

[madbean]

I haven't built the Blueshift but my guess is the clipping you are experiencing may be from the compander. First I would pull both NE570s and test again. This eliminates the chorus output so it will tell you whether or not the clipping is in the clean through audio path or the delay (modulated) path.

If there's no clipping then it's happening in the delay path. There are a couple options you can try here.
One is to reduce C10 and C47 from .47uF to 220n. This will shorten the response time of the compressor portion of the circuit. It might help a little.

The other option is to leave those caps at .47uF and add a series resistor between C9 and pin6 of IC2. This resistor will add some signal attenuation to the compander input. Values to try are 47k through 100k to get the right amount of clipping reduction. This is kind of an awkward mod to do though.

Again, these are educated guesses. Only do them if you are comfortable desoldering and replacing parts. Otherwise you could screw up the expensive build!

[madbean]

I'd think somebody with over 11k posts wouldn't even blink building this pedal 

The fact that jimi has more posts than me shows just how hardcore he is!

[micmac]

Thanks Brian! I pulled the companders and the signal stays clean when on.

I don't have 220n to try your idea #1 right now. And #2 seems awkward as you say. I'll ponder these ideas, though.

I tried one other thing. I pulled the regulator and shorted in and out. But it didn't make a difference.

Thanks!

[jimilee]

I'd think somebody with over 11k posts wouldn't even blink building this pedal 

The fact that jimi has more posts than me shows just how hardcore he is!

Or I don't have a life and rely on you for my entertainment.


Sent from my iPhone using Tapatalk

[gordo]

I haven't had headroom issues with the 3 builds I've done but to be honest has been the least of my issues given how extreme this build is.  If possible can you post voltage charts for the pertinent parts and lets put some math to this?

[micmac]

Hello gordo,

Happy new year!

Below the voltages. Some I had to read from the back, but I think I got it right. Please be aware that the regulator is still out and the input of the regulator on the PCB is shorted to the output of the regulator on the PCB. As mentioned earlier I did that for testing. So the supply voltage on the BBDs is a tad higher.

Brian mentioned earlier he suspects the compander. I audioprobed yesterday and in my opinion the distortion is introduced by the compander like Brian said. You can't really notice it right after the compander, but between R28 and Q5 you can hear the distortion. I think that's just a buffer.

I had to order some items on the internet yesterday, so I added two NE570 chips. I guess they'll arrive tomorrow. I'll swap the Coolaudio V571 chips with these ones, maybe I'll get lucky.

Thanks!

Code Select Expand

IC1
4,54
4,54
2,26
0
4,52
4,54
4,54
9,08

IC2
1,17
1,82
1,82
0
1,84
1,8
2,98
1,83
1,83
1,84
1,84
1,84
9,08
1,8
1,82
0,15

IC3
0
~4.25 fluctuates a bit
4,28
~8,2 fluctuates a bit
~8,8 fluctuates a bit
~4,25 fluctuates a bit
~5,2 fluctuates a bit
~5,2 fluctuates a bit

IC4
~8,8 fluctuates a bit
~4.25 fluctuates a bit
0
~4.25 fluctuates a bit
5-8 fluctuates
0,9-2,8 fluctuates
5,6-7 fluctuates
~8,2 fluctuates a bit

IC5
4,8-7,2 fluctuates
1,3-2,2 fluctuates
1,7-2,7 fluctuates
0
4,52
4,54
3,6-5,5 fluctuates
8,65

IC6
3,6-5,6 fluctuates
4,54
4,52
0
1,7-2,7 fluctuates
1,4-2,2 fluctuates
4,8-7 fluctuates
~8,65 fluctuates a bit

IC7
0,6-8,4 fluctuates
4,11
3-6 fluctuates
0
4,52
4,54
3,3-5,7 fluctuates
9,1

IC8
~8,8 fluctuates a bit
~4,2 fluctuates a bit
0
~4,2 fluctuates a bit
5,6-7,7 fluctuates
1-3 fluctuates
4,8-7 fluctuates
~8,2 fluctuates a bit

IC9
0
~4,2 fluctuates a bit
~4,12
~8,2 fluctuates a bit
~8,8 fluctuates a bit
~4,2 fluctuates a bit
6,42
6,42

IC11
1,16
1,83
1,83
0
1,84
3,06
3,06
1,84
1,84
3,05
3,05
1,85
9,08
1,83
1,83
1,18

IC12
4,53
4,54
4,52
0
4,52
4,54
4,54
9,08

OPTO
1,34
0
0
4,54
3,97
4,54

Qs (E, B, C) or (D, S, G)
#########################

Q2 3,86 4,2 9,08

Q3 3,6 (goes down, dmm?) 3,6 (goes down, dmm?) 0

Q4 3,62 3,17 9,08

Q5 3,84 3,92 9,08

Q6 3,22 3,79 9,08

Q7 8,1 7,51 1,4-2,2 fluctuates

Q8 8,1 7,49 1,4-2,2 fluctuates

Q9 3,21 3,799,08

Q10 3,62 3,16 9,08

[micmac]

Hi all! Small update...

I replaced the V571 ICs with NE570. No change. I double-checked all the component values around compander IC2 (C9 till R28) and also reflowed all the solder joints there. Also no change.

Then I put the regulator back in and measured all the voltages again (see box below).

I found voltages provided by aion himself here: Link

I don't have his voltages on IC2 pins 10 & 11, but I think his values may be off there because on the PCB pins 10, 11 & 12 are connected and he wrote down a different voltage for pin 12. And that side of the compander isn't used anyway.

And on IC1 pin 3 my voltage is a bit low, but I think that's due to the 1M pullup resistor loading down my DMM.

The rest of the voltages all seem pretty much in aion's ballpark, nothing sticks out.

Code Select Expand

IC1
4,54
4,54
2,26
0
4,52
4,54
4,54
9,08

IC2
1,17
1,82
1,82
0
1,84
1,8
2,98
1,83
1,83
1,84
1,84
1,84
9,08
1,8
1,82
0,15

IC3
0
~3,15 fluctuates a bit
3,14
~6,05 fluctuates a bit
~6,50 fluctuates a bit
~3,2 fluctuates a bit
~3,66 fluctuates a bit
~3,66 fluctuates a bit

IC4
~6,5 fluctuates a bit
~3,17 fluctuates a bit
0
~3,15 fluctuates a bit
4,8-5,8 fluctuates
0,6-1,6 fluctuates
3,9-4,9 fluctuates
~6,08 fluctuates a bit

IC5
3,6-4,9 fluctuates
1,05-1,5 fluctuates
1,25-1,9 fluctuates
0
3,3
3,33
2,7-4 fluctuates
6,28

IC6
2,7-4 fluctuates
3,32
3,31
0
1,3-1,9 fluctuates
1,0-1,5 fluctuates
4,0-5,0 fluctuates
6,28

IC7
0,6-6 fluctuates
3,01
2,3-4,3 fluctuates
0
3,3
3,32
2,5-4,1 fluctuates
6,66

IC8
~6,5 fluctuates a bit
~3,13 fluctuates a bit
0
~3,13 fluctuates a bit
4,8-5,8 fluctuates
0,7-1,6 fluctuates
4,0-4,9 fluctuates
~6,08 fluctuates a bit

IC9
0
~3,13 fluctuates a bit
~3,02
~6,08 fluctuates a bit
~3,13 fluctuates a bit
~4,2 fluctuates a bit
4,42
4,42

IC11
1,07
1,83
1,83
0
1,84
3,06
3,06
1,84
1,84
3,05
3,05
1,85
9,08
1,83
1,83
1,08

IC12
4,53
4,54
4,52
0
4,52
4,54
4,54
9,08

OPTO
1,34
0
0
4,54
3,97
4,54

RG1

9,06 0,66 6,66

Qs (E, B, C) or (D, S, G)
#########################

Q2  3,86 4,2 9,08
Q3  3,6 (goes down; due to my DMM?) 3,6 (goes down; DMM?) 0
Q4  3,62 3,17 9,08
Q5  3,84 3,92 9,08
Q6  3,22 3,79 9,08
Q7  6,01 5,45 1,0-1,5 fluctuates
Q8  6,02 5,46 1,0-1,5 fluctuates
Q9  3,21 3,79 9,08
Q10  3,62 3,16 9,08