Wayne's BA 2018 linestage

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Hello gang, many months ago I started Wayne’s BA2018. I got super busy with work over the summer so it sat until recently I was able to complete it. I’ve included some pictures of the completed work. It sounds great sonically BUT I have a noise issue. I have a buzzing sound coming out of both speakers going through my F5T amp. I’m going to start digging into it tomorrow and I’ll also try it on a commercial amp I have to see if the problem is there as well. I was hoping to get some help with the grounding. I want real sure what to do with the shields since I connected the Linestage for SE input and not balanced. Thank you in advance
 

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6L6

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This is RCA in to RCA out, yes? It looks like you have the input wired incorrectly... Red to (+IN), white to (GND), jumper (-IN) to (GND).

You can attach the shields to GND as well.

A couple of questions -

Where does PSU ground (not safety earth) connect to chassis?

What's the circuit on perfboard?

What is the function of the gold capacitors (and a resistor...?) haphazardly jammed into the BA2018 PCB?
 
Hello gang, many months ago I started Wayne’s BA2018. I got super busy with work over the summer so it sat until recently I was able to complete it. I’ve included some pictures of the completed work. It sounds great sonically BUT I have a noise issue. I have a buzzing sound coming out of both speakers going through my F5T amp. I’m going to start digging into it tomorrow and I’ll also try it on a commercial amp I have to see if the problem is there as well. I was hoping to get some help with the grounding. I want real sure what to do with the shields since I connected the Linestage for SE input and not balanced. Thank you in advance

Second 6L6s comments.

Just a thought: did you test the circuit alone, and was it quiet then? Meaning nothing else attached but power? The Muse-circuit kinda complicates troubleshooting. So a thought would be to disconnect it, short your inputs (+ and - shorted to gnd, ref 6L6s handwritten schematic earlier in the thread, and if quiet then, connect more stuff and see when the noise kicks in.

Also, the question of gnd is relevant. Looks like your chassis and PSU gnd is directly connected together. I also see the muse board is connectd to gnd. Again, disconnecting these things and simpifying before troubleshooting, may be an idea.

I recommend a look at 6L6s Pearl 2 guide for gnd inspiration, very good stuff.
Regards,
Andy
 
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Or, as a variant to andy‘s way, just disconnect the muses, and hook up something with an attenuator ( phone, laptop etc) directly to the WLS‘s input.

Muses is said to require a separate psu especially for the display … if the pre is quiet without the muses, you could reconnect it, but without display (if thats possible), and hear what that gives…
 
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Member
Joined 2017
Paid Member
This is RCA in to RCA out, yes? It looks like you have the input wired incorrectly... Red to (+IN), white to (GND), jumper (-IN) to (GND).

You can attach the shields to GND as well.

A couple of questions -

Where does PSU ground (not safety earth) connect to chassis?

What's the circuit on perfboard?

What is the function of the gold capacitors (and a resistor...?) haphazardly jammed into the BA2018 PCB?

6L6, Thank you for the input. I totally forgot about jumping the in- to ground and I did that. I still have the noise.

The PSU is grounded at the chassis ground. From the power inlet, the green goes to the chassis and the another green wire comes from there back to the ground terminal block on the PSU board.

The circuit in the perf board is a muting relay circuit. It’s shown on the Academy Audio webpage in the schematic for the BA2018.

The gold caps and resistors on the BA2018 is another mod on the Academy Audio website. It’s and RC filter. This is how they describe it on their page

Referring to Figure 3 below, note extra components added to the positive and negative power rails of each BA2018 board. Referring to the Left channel, the RC filter R101 C14 on the V+ rail, and the R103 C15 on the V- rail improve transient response of the line stage and increase channel separation. Some of the available PCBs for 2018 may already have these components installed. There is no need to duplicate them. I didn’t recognize these on the schematic so I added them at this point.
 
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Second 6L6s comments.

Just a thought: did you test the circuit alone, and was it quiet then? Meaning nothing else attached but power? The Muse-circuit kinda complicates troubleshooting. So a thought would be to disconnect it, short your inputs (+ and - shorted to gnd, ref 6L6s handwritten schematic earlier in the thread, and if quiet then, connect more stuff and see when the noise kicks in.

Also, the question of gnd is relevant. Looks like your chassis and PSU gnd is directly connected together. I also see the muse board is connectd to gnd. Again, disconnecting these things and simpifying before troubleshooting, may be an idea.

I recommend a look at 6L6s Pearl 2 guide for gnd inspiration, very good stuff.
Regards,
Andy


Andynor, thank you as well. As you suggested, i removed the input from the Muses to the BA2018 and it’s totally quiet on both channels. The power supply ground and power ground are connected together at the chassis. The muses MCU requires a +/-/g psu. I ran everything back to the psu for this. As for simplifying, I reconnected the inputs as normal but removed the +15v power lead to the muting circuit and sure enough it’s quiet as can be. I’m thinking this where my troubles are. Depending what I find, it’s not a necessity and can be easily eliminated. I will working on this later today.
 
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Joined 2017
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Or, as a variant to andy‘s way, just disconnect the muses, and hook up something with an attenuator ( phone, laptop etc) directly to the WLS‘s input.

Muses is said to require a separate psu especially for the display … if the pre is quiet without the muses, you could reconnect it, but without display (if thats possible), and hear what that gives…

Myleftear, Thank you for input as well. Prior to removing the power to the muting board, I removed the display ribbon cable and still have the noise. I think I will try to incorporate a separate power supply for the Muses and display later as well.
 
Nice work, finding the source of the noise so quickly! :cheers: Also means the rest of the circuit is fine, good work. Wrt the RC networks, I think you are good without. Smoothing caps were added to the boards current revision, and more is not always merrier, as 6L6 kinda points out.

Good luck with the rest! Can’t help you with digi-noise, other than suggest a separate PSU, wich others have done too and you yourself are allready considering.

Edit: You could also consider a ground loop breaker according to Pearl 2 / Waynes way, if you at a later date find the gnd scheme had room for improvement wrt noise (can also be in the higher frequencies).

Regards,
Andy
 
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Myleftear, Thank you for input as well. Prior to removing the power to the muting board, I removed the display ribbon cable and still have the noise. I think I will try to incorporate a separate power supply for the Muses and display later as well.

I don't think you need to give up the muting capability or use separate power supplies, just figure out where the noise is coming from. My configuration is pretty much the same as yours although implemented differently.

Back at post 2805 I put photos of my BA2018 which includes the stock BA2018 board and the Muses volume control (which I love, the sound is so clean). I used a single power supply -- my pcb design which uses a Mean Well +/- 15V module followed by the PO89ZB filter on both legs -- to power both the preamp and the Muses -- and it's dead silent. From my experience, I don't think you need separate power supplies for those two units (but I'm not using the display).

In the same pictures you can see my add-on board between the BA2018 and the back panel which provides turn-on delay muting and also mutes momentarily when inputs are switched, and it causes no noise whatsoever. I'll bet there's a simple fix, just need to find it.
 
As for simplifying, I reconnected the inputs as normal but removed the +15v power lead to the muting circuit and sure enough it’s quiet as can be.

Are you using the "mute" control signal from the Muses? If yes, where are you getting power for the separate mute pcb? could you be causing some kind of loop by taking signal and power from differently grounded locations?
 
Andynor, thank you as well. As you suggested, i removed the input from the Muses to the BA2018 and it’s totally quiet on both channels. The power supply ground and power ground are connected together at the chassis. The muses MCU requires a +/-/g psu. I ran everything back to the psu for this. As for simplifying, I reconnected the inputs as normal but removed the +15v power lead to the muting circuit and sure enough it’s quiet as can be. I’m thinking this where my troubles are. Depending what I find, it’s not a necessity and can be easily eliminated. I will working on this later today.

I don’t have time to check the schematic for the Muse muting circuit. But let’s throw an hypothesis out there: If there is a separate gnd cable from the mute circuit, that you have connected together with the clean audio gnd at the rails of the PSU, this is a likely culprit. I recommend you try connecting that cable to chassis star instead, and then - just for testing - disconnecting audio gnd/PSU gnd from the chassis alltogether. Turn on and listen. Silent? Found your culprit. Same goes for all non signal return/non audio gnd cables from the Muse circuit.

Isolate and test, basically.

Regards,
Andy
 
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Hi guys, sorry I couldn’t jump on last night. Rather than calling everyone out individually, I will just say thanks to all who gave input and let you know what I’ve done to this point. So earlier in the day, I removed the muting board from the circuit and connected directly out of the BA with no success. Total brain fart realizing the muting board is on the output, my problem is more than likely upstream. anyways, made no difference, still have noise. Then I removed the ground from the Muse controller from the psu and brought it back to the chassis. No success, still has noise. Then I disconnected the Muse controller and plugged in my iPad directly to the input of the BA2018. It’s as quiet as can be. Reconnected Muse VCM and brought all grounds back to chassis ground, no success. I have a bipolar 15vdc psu from Academy Audio. I removed the muse VCM from the BA2018 psu and connected it directly to the psu. Still have the noise. Removed the VCM and pulled it far away from the x-former/psu, still noisy. I have another VCM, I’m going to try it later today. What did I miss? Not too many options left? Nice build btw wapo54001 and yes I am/was using terminal 8 on the VCM for the muting circuit
 
Well, just reading quickly, but from all your test isn't simply the Muse VCM the problem?

With it, whatever you did, it seems to be noisy. Once removed and dealing directly, noise is gone.

Just try another VCM or whatever passive volume control (one without PS) and work from there on?

Just read quickly, sorry...

Claude
EDIT : and / or check the VCM sound connections / cables
 
Is the "noise " you are referring to a buzz or a hum?
I have the BA2018 with Muses VC and display. Which version do you have (72320 or 72323)? Do you use a display?

I have the 732320 with Adafruit display and remote control. If you are using the same Adafruit display, it should have its own +5V independent of the Muses PSU.

For grounding, the BA 2018 PSU, Muses PSU, and the display PSU ground meets at star ground point then to chassis ground. The BA 2018 board ground should not be connected directly to the chassis ground point, but to the BA2018 PSU only via a single wire.
To troubleshoot for a buzz, install extra wire (with the other end not connected) at the BA 2018 PSU ground, the Muses PSU ground, and do the same to the display ground. You can connect to and probe one at a time, say 2018 PSU wire to Muses PSU ground, and see the noise level change when doing so. You will reach a point that the connection you made is the right grounding scheme, it will be quiet.
No need to short the input but make sure to set Muse attenuation level to high so that it has the attenuation needed to just hear the output at low level (easier to determine change in noise magnitude and protects the amp).
As I said, I have my BA 2018 with Muses 732320. It is very quiet and sounds great than when I was using a DACT 50k attenuator.
Hope this helps.
 
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Hi guys, sorry I couldn’t jump on last night. Rather than calling everyone out individually, I will just say thanks to all who gave input and let you know what I’ve done to this point. So earlier in the day, I removed the muting board from the circuit and connected directly out of the BA with no success. Total brain fart realizing the muting board is on the output, my problem is more than likely upstream. anyways, made no difference, still have noise. Then I removed the ground from the Muse controller from the psu and brought it back to the chassis. No success, still has noise. Then I disconnected the Muse controller and plugged in my iPad directly to the input of the BA2018. It’s as quiet as can be. Reconnected Muse VCM and brought all grounds back to chassis ground, no success. I have a bipolar 15vdc psu from Academy Audio. I removed the muse VCM from the BA2018 psu and connected it directly to the psu. Still have the noise. Removed the VCM and pulled it far away from the x-former/psu, still noisy. I have another VCM, I’m going to try it later today. What did I miss? Not too many options left? Nice build btw wapo54001 and yes I am/was using terminal 8 on the VCM for the muting circuit

I think you will find your culprit in either your wiring, or in the VCM/Muse circuit itself. Gremlins are everywhere, and many of them we put in there ourselves :clown: