atomicbob's SMPS Noise Nuke for HP amps with external SMPS

External Switch Mode Power Supplies are included with many headphone amps as a way to keep cost and shipping weight down, except Schiit which use external transformers with true Linear Power Supplies internal to the chassis in their lower cost products. SMPS offer higher efficiency, less heat, smaller size and weight. Unfortunately they often have higher residual noise which does affect amplifier performance. SMPS vs. LPS effect on an example headphone amplifier may be found here:
SMPS vs LPS effect on Garage1217 Project Sunrise III

The following single massive stage LC filter will reduce SMPS residual ripple and noise. Parts cost was approximately $42 US in component single unit quantities, and about 2 hours of construction time. It will work with any external SMPS or LPS between 1 and 48 VDC with current less than 2A. Examples include Garage1217 and the Massdrop Cavalli Tube Hybrid (MCTH) headphone amps.



Component values were chosen to achieve greater than 20 dB reduction at 60 Hz with greater than 60 dB reduction at 1000 Hz. Here are the Linear Technology Spice simulations with various dB vs. frequency noted:

Noise reduction at 60 Hz


Noise reduction at 1000 Hz


Noise reduction at 10 KHz


Noise reduction at 75 KHz


Measured performance

Meanwell GS40A24-P1J - 24Vdc with 430 mA resistive load


Meanwell GS40A24-P1J + Noise Nuke LC filter - 24Vdc with 430 mA resistive load


SMPS noise has been nuked substantially.


Linear Power Supplies may also have residual ripple and benefit from the Noise Nuke LC filter.

Jay's Audio Talema LPS - 24Vdc with 430 mA resistive load


Jay's Audio Talema LPS + Noise Nuke LC filter - 24Vdc with 430 mA resistive load


Keysight U8001A will have lower residual noise but is also rather large, heavy and expensive; currently approximately $440 US. The Jay's Audio Talema was $115 US at the time I acquired it. $42 US for the Noise Nuke plus several hours construction time to achieve nearly the same performance in a much more transportable format is a good tradeoff for me.

 

Amplifier performance measurements

PS-III THD, THD+N and 1 KHz spectrum - Meanwell SMPS:


PS-III THD, THD+N and 1 KHz spectrum - Meanwell SMPS + Noise Nuke LC filter:

Note substantial reduction in spectrum residual noise and thus a reduction in THD and THD+N.



PS-III THD, THD+N and 1 KHz spectrum - Jay’s Audio Talema LPS 24V:


PS-III THD, THD+N and 1 KHz spectrum - Jay’s Audio Talema LPS 24V + Noise Nuke LC filter:

Again note a useful reduction in spectrum residual noise, though not as dramatic as for SMPS.


PS-III THD, THD+N and 1 KHz spectrum - Keysight U8001A 24V:

Keysight U8001A for reference.


Bill of Materials (parts list):

 

reserved 3/3.

 

What about output impedance?
Noise is one aspect, but audio is not steady state; the PSU needs to respond to power surges quickly.

 

I'm going to build one of these. Mind putting the final parts list up for us?

Edit: See the BOM in the second post.

 

If you look at most audio power supplies you will find a large electrolytic capacitor somewhere just prior to the actual amplifier circuit. This LC filter has a 13600 uF cap providing 3.91 Joules of energy storage for the Garage1217 PS-III at 24Vdc and 5.3 Joules for the MCTH at 28Vdc. Now consider a 97 dB SPL / mW, 30R headphone. Take a kick drum hit of 50 mS in duration and ask for the peak to deliver 97 dB SPL to the listener. This will require 203 micro Joules, which is minuscule compared to the reserve now available.

 

I used a Bud CU-234 enclosure. The power jacks were uxcell 2.1mm x 5.5mm metal panel jacks. Then one needs an additional pair of 2.1mm x 5.5mm CCTV power plugs and some 14 to 16 awg cable. I used Cable Matters. I'll create a spreadsheet in a bit. Multitasking at the moment.

 

Edited second post with BOM.

I intend to make a few more of these. Maybe I should send one around on a loaner tour.

How many o' you nice folks think I knows what I's talkin' 'bout? RAISE Y'HAIN UP! Uh-huh!
An' how many thinks my potato been bakin' too long? RAISE YO MIZZABLE HAIN UP! Uh-huh!

(Bonus points for knowing the album from which that is taken.)

 

As the owner of a PSIII with the talema LPS, this looks like a worth first DYI project.

 

Tom at Neurochrome does a similar application with his SMPS-86. Although the inductor is nowhere near as heavy duty as what you are using.

 

As a new owner of a HP/Aligent 3717A LPS and a Horizon III, I'd be in on a listen for sure. I gave up trying to build shit anymore I'm afraid. So I razing my hain up! Assuming it would a good idea with this unit.

 

I'm assuming you mean E3617A. Ha! You already own one of the finest LPS on the planet designed by Real Engineers(TM). I don't think the Noise Nuke will provide you much benefit, if any at all. Maybe should do a tour and send one your way to hear for yourself.

 

Damn. I could of sworn I typed that in correctly. Numeric dicks Lessia. . I'm in on a loaner to see what, if anything it does. I remember Real Engineers (TM). A lot of them are enjoying retirement. Are they the same folks that designed my Marantz 2245 integrated amp back in the stone ages?

 

While I'd be genuinely surprised if it provided audible benefit to the E3617A, it'd be interesting if it managed to clean it up even further somehow.

I'm planning on building one as soon as the two big ticket sales I have pending actually come through (Orchid and JVC cans).

I don't actually have anything at home at the moment that can use it, though. Would have to connect a switching power supply and make sure it's okay via a multimeter, then send it along to someone.

Actually, I suppose I can try it with a Schiit Wyrd. Yeah.

 

I can tell you it has had a definite and not subtle audible improvement to the Horizon III. Not getting enough sleep lately. Fell asleep last night listening to all of Beethoven's Symphonies. Was way down the list about 4 a.m.

 

I doubt you'll see any improvements from the Wyrd. An Apple USB cube though....

 

Sorry, my wording was unclear. I mean I doubt Noise Nuke would make an audible improvement over and above the E3617A. I know how much of an improvement that LPS makes to the Horizon.

 

I think I was unclear. Lack of sleep. You came through loud and clear. You and @atomicbob are probably right. Scientist in me wants to check the hypothesis. And my hearing. In the meantime, Boston Pops Rhapsody in Blue never sounded better. I owe you one Luckbad.

 

Somebody has been listening to 'Porn Wars'.