Lazy Singing Bush mono block build using THF51s

2 x 22 mF/100V caps and 2 x 10 mH/5A chokes have been ordered.
Then next chapter of this project can start. At least I heard them play in 1st chapter.
It could be interesting with a distorsion measurement before and after modification of PSU.
The voltage can be readjusted to 65 VDC after a bit of voltage drop over the chokes.
These mono block chassis are a bit on the small side for linear PSU with CRCLC filtering and 400 VA toroid.
Now with SMPS and LC filer it may just fit.
 
Very Interesting development! 🙂👍

But it could be considered more than just a slight overkill, on behalf of the fact that we humans very, very, very seldom actually listens to music with the full sized speakers placed with the tweeter wave guides so close that they actually touch the left and right ear.

Just sayin… :Pirate:

🙂
 
hum/hiss/garbage issues - in general one can be happy to hear nothing of these when ear is at least 30cm away of speaker

that's completely proper criteria, and in many cases one can live perfectly with that

however, if more is invested to elevate that level of blackness (well, one must push its ear in cone and then 50cm more, to hear anything) that will certainly increase SNR thus enabling even tinier details (if present in source material) to be presented

when one is going to stop with chasing da Rainbow - strictly matter of personal taste and OCD

anyhow, you already have opportunity to hear 95% of what that amp is capable, even with that faint hum

last 5% - up to you :clown:
 
The amp deserves the best. I know how quiet amps can be.
I thought it was only the tweeter but when I concentrated I could hear a bit from mid and woofer also.
It has to disappear. What I did not quite understand is that a relative sensitive DMM could not measure any AC at speaker out (when no signal in).
Usually when I had noise issues it showed like 0.4 mV. I have had up to 4mV from a tube amp. That was really bad. Is was audible from listening position. An upgraded PSU cured it.

The 20 kg chokes in cellar (used for the MoFo amp.......a fantastic amp......but too unpractical). The weight is estimated only but it is heavy. I have of two them. It was ordered as 100 mOhm but they were able to get it down to 73 mOhm DC loss (50 mH is at 3A). Choke can handle more than 20A current. Copper wire is not round but square......I think 12 mm wide......flat wire. They "sleep" in the cellar. There are also four twin filter chokes (2 x 200 mH, 2 x 2A). For future projects.

The company told me they could get down to about 33 mOhm if they used an UI-core but then weight was 75 kg. I started asking for 10 mOhm DC loss. They went back with the message that it was not realistic. They make transformers for trains so it was possible to make one.......but.....
Why the DC loss was so important was that I would try to avoid the output cap for the MoFo. But I ended up using it.
 

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MEPER, After reading the Connex article that you referenced in your post #108 (Connex SMPS), I have a few thoughts.

The SMPS has ripple but the ripple frequency should be above the audible range. The article showed an example where the frequency was 101kHz. If you have an oscilloscope, you should measure the frequency of the ripple that you measured. Knowing the frequency may help you identify the problem and come up with a solution. The ripple may not be the cause of the noise that you heard if it is way above the audible range.

The article mentioned positioning the SMPS away from other circuits because of radiated emissions:

Due to the high power and intense stray magnetic field around the power transformer and resonant inductor the SMPS2000RxE should not be installed directly on top or below any amplifier board and a distance of at least 50mm must be kept to prevent any interference. The magnetic field intensity decreases exponentially with the distance from the source and thus 10-15cm away would be low enough to not affect the other stages.

You mentioned that your VFET amplifier with a SMPS is silent but the SMPS is externally mounted. As an experiment you can try taking the SMPS out of the chassis to see if that lowers the noise.

As I mentioned in a previous post, you can perform a FFT on the amplifier output to see the noise at the amplifier output. I have an amplifier that I could hear noise if I had my ear to my 103dB speaker. The FFT showed 120Hz noise that was 70dB below the 1W 8R 1000Hz fundamental signal. By looking at the FFT results you can determine the frequency and magnitude of the noise. Because of the FFT results, I knew that it was a power supply filtering issue, so I changed the power supply filter from CRC to CLC. That lowered the noise to more than 90dB below the 1W fundamental and I could no longer hear any noise.

I think you should determine the properties of the noise that you heard and also determine the frequency of the measured power supply ripple, as I think they are keys to resolving the issue.
 
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When I looked at the PSU out with scope I saw some 100 Hz (quite a lot). It was thinking that this could be magnetic fields picked up by the probe and not something direct from output. When I mounted the SMPS and boards I tried to mount SMPS as far away as possible. The mu-follower board is closets but still away from the dirty part of the SMPS which I assume is the rectifier part of it. Original it was my plan to have the SMPS in its own boxes but more practical to have it inside. I could make one box with both SMPS's in and two outputs and then have choke and 22 mF cap inside amp chassis. I can change PowerCon input to a SpeakOn connector which I use for DC power for other amps (also to avoid mistakes and Neutrik claims that SpeakOn can take more DC current). And then the mains fuse on amp chassis would be the rail fuse. Then all the dirty parts were outside amp chassis. I switched back to VFET amp and it is amazing how quiet it is. VFET amp also have some voltage gain. A follower amp should be 100% silent.

I also have some mu-metal foil I can play with. But as more as I am thinking about putting the SMPS's in own chassis......I like it better and better. Choke and 22 mF cap can live its life in amp forever. The PSU part could still be changed/modified.

Would a screened power cables from such a PSU box be necessary?

It is better to go with correct solution than spend more time with no so optimal solution. It may end up with same solution anyway......and then better to take decision now. It was nice with the Modulus chassis with base plate that the holes fits the mounting holes for SMPS modules. I wonder which modulus chassis I could use for those two SMPS boards......they need the height but overall rather small.
 
Separating/shielding the dirty power supply from the audio amplifying parts simply cant be a bad way to go.

How much better the music will sound in the end, by doing that, in every specific case, is of course more open for endless debates 🙂
 
I also sent a mail to Connex regarding my measurements like the 130mV ripple etc.
I got at response back with some documentation and a guideling how to measure this kind of noise.
My measurement metode lacks for this kind of applications. I just used my Tektronix probe with scope and DMM with the wires that were included to be used with DMM. So first Connex response below and next post I will write a bit of my own measurements.


Hello
The noise should be measured properly, with a high bandwidth oscilloscope and properly connected probes. otherwise the measured value will be way above the real value because of noise pickup.

Below are some measurements for the SMPS600RxE +-55V tested at 200mA, 1A and 5A the noise is in mV RMS domain with peak noise of 50mV.
You can see the measurement setup with the probe wires connected directly to the output wires without the GND cord.


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It seems that the reason for relative high ripple from DMM in AC mode was caused by some noise pickup by the long wires.

When I used my scope using standard x10 Tek probe in AC mode I was quite disappointed but I was thinking that maybe it was caused by some noise pickup.
From memory the 100 Hz noise I measured was something like 2-300 mV pp. The shape looked (from memory) like at capital "D" if you place a centerline horizontal and then look at the upper part. I bit like the charge current would be in rectifier capacitors? .....how this can translate to a voltage I see on scope I don't know.......but this it from memory.....I could be wrong.

To me it makes more and more sense to take out the SMPS's and place in own chassis and then just have the filter choke and 22 mF cap in amp chassis. It should filter the 100 kHz and also if there should be some 100 Hz left. Then the cap will ensure amp look into a low impedance PSU. So that is the plan.
 
recapitulation?

you have 100Hz present in speakers?

you can connect your lab psu temporary instead of switcher, then check do you still have buzz

then you can move switcher out of case for test, then check do you still have buzz

main catch is to investigate what's culprit for buzz - now we can exclude switcher output ....... but we need to deduce garbage route
 
Yes, I can hear a bit of 100 Hz from mid woofer and woofer with ear 10-20 cm from it when living room is completely silent.

The lab-supply I have has ripple noise. I know that from an earlier test. It is not SMPS based but with a large transformer with a lot of secondary windings and relays that clicks them in when you increase voltage. So a supply with a lot of compromises.

I am confident that 100 Hz problem gets solved when SMPS's gets its own chassis. After all the noise is relative low at speaker output. Less than my DMM can measure. It measured 0.0 mV in AC mode.

I would like to have the SMPS in a chassis with mains power connector etc......to not make any stupid mistakes with mains 🙂
I have two small Modulus chassis I purchased to lower the shipment cost. Think I can use them for the SMPS's. Will have to check.......
 
I had enough listening time to rate the amp to be very good. A lot of "punch". Stereo imaging and depth very fine also.
It is the plan that this amp should be my primary amp and take over from VFET kit amp 🙂
The 400W both Lazy amps burns together creates quite a lot of heat. The VFET is nothing compared to this.
I need much more time to evaluate as I where so focused to the noise problems......but it must wait until power supplies has been built.
The Modulus chassis I have two of are Galaxy 2U with base plate. Large enough. I just need to find a way to get a bit of additional heatsinking for the SMPS. The Galaxy side panels are a bit strange profile. Not easy just to screw something to them. Will see if I can find some smaller heatsink just to screw on SMPS heatsink mount.
 
Then it is planned that the preamp will be the balanced version of the IronPre kitamp if I am lucky to get one. Then I can try balanced out from my DAC.
Lazy seems easy to drive with a 220k input resistor to jfet drivers. Should not be a problem for IronPre output transformer......I assume. Then I can set gain so it just fits my needs.