I'm happy that you found the problem.
Replace also both zeners and it's not a bad idea to replace also the LM317s.
LM318 and LM3886 should not be affected.
I replaced 2 zener, bd139 and bd140 (not lm317) and now I have the same behaviuor for both boards.
I prepare a dummy load of 5,4ohm with some resistors in parallel and try to do some test and measurement. I use a wave generatore on input pin with a sin at 1Hz and 100mV of amplitude and an oscilloscope probe on the load.
In attach you can see the result... the output is not clean but there is a troble at 50Hz.
If I don't put any input, the output is clean. If i put only positive pin of the input I havea strange wave at 50Hz (see attach foto).
In attach also the ampli build...
I don't know if I have some wrong insulation or if toroid create interference on input...
Attachments
No, the 25V version of Cerafines does not sound as good, the PKs will be better.
Fine
The My_Ref is a floating design, it takes its ground reference from inputs.
Without signal ground connected at the input it will hum, the strange wave you see is exactly that.
Check also that heatsinks (the side panels) are at ground potential.
I can't see a connection to safety ground, the whole chassis should be grounded.
If the hum (with input grounded) does not disappear you should try to rotate the toroids until it vanishes.
C9 usually see at best 2V so a much smaller rating than 50V can be used.
The theoretical maximum is 36V but just in case of fault.
So, in the past, we considered acceptable that C9 could fail in case of fault (the DC protection kicks in before anything bad could happen) to be able to use a really good sounding cap as a BlackGate PK.
Now using Cerafines rated at 50V we could have both, really good sound and circuit resiliency.
ok great to take that out of my confusion list! So we can use any audio cap like kz, es , pk or cerafines if they are rated 35v or more.
you don't recommend the elnas silmic II , brown version , but you like the black sleeve ones.
Did you ever try the nichicon ka? they are suppose to be audio caps at 105c!!!!!
And one more thing , the direction of the resistors and the plastic or ceramic capacitors, does it really matter?
you don't recommend the elnas silmic II , brown version , but you like the black sleeve ones.
Did you ever try the nichicon ka? they are suppose to be audio caps at 105c!!!!!
And one more thing , the direction of the resistors and the plastic or ceramic capacitors, does it really matter?
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Yes but that cap will have a great influence on sound, so far nothing sounded better than Cerafines 50V and Black Gates.
Nichicon ES is extremely clean but also really colored in the midrange, much better Elna BP if you want to use a bipolar, but Cerafines will sound better.
Yes, but they have steel leads, I don't bother trying them.
IMHO absolutely yes, otherwise I wouldn't have recommended a preferred orientation.
But you can try for yourself... build the amp according the build guide, including preferred orientation, and simply mount sockets (Mouser 506-510-AG90D) in a pair of positions (a cap and a resistor, like C12 and R12) and listen in both directions.
If you think about it enough, it matters.
If you build two amplifiers and one of them has a resistor "reversed" by mistake, you will never know the difference.
But, as Dario suggests, try it for yourself. Simply "reverse" any single passive component in one of the amps, a component that's easy to remove and resolder and you won't even need sockets. Listen carefully. Change the direction of that component. After several hours of playing, listen carefully again. Do NOT make your judgment immediately, as it takes time for the solder joint to settle and/or the part to "repolarize" itself (even if you use sockets). Comparing instantly is not the way to make this evaluation. I believe that every part of a circuit becomes directional after a certain amount of passing current, which is what accounts for hearing break-in, directionality of wire, etc.
Peace,
Tom E
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Hi Tom,
Break-in is not related to directionality... it's a almost permanent change in measured and/or perceived performance after some time of use.
On the contrary components/parts with a preferred direction doesn't change this behaviour with time/use, they will exhibit the differences (thinner/drier Vs fuller/rounder) when new as after years of use.
See this pic from a previous version of boards:
You can see that markings are toward C1 and C2.
All 3 Amtrans should have markings toward C1 and C2.
Attachments
Dario, that's your opinion, and it is valid but hardly definitive. Do you have any technical insights or even speculation about possible causes? I am not claiming it doesn't exist. I know you have experimented exhaustively to determine directionality, and sometimes your results seem ambiguous, possibly because your indicator, the direction of the printed label, can be random. Perhaps part ARE directional, but the label is not a suitable indicator. These are my thoughts on the topic.
Break-in is a phenomenon, not a quantifiable process. It has never been measured and can be detected only by listening. It has not been suitably explained by electrical theory, other than forming of electrolytics. However, it has been detected by the majority of audiophiles with a wide variety of components and systems, although there are skeptics who claim it does not exist. It is not necessarily permanent.
Directionality is a similar phenomenon, possibly a subset of break-in, which cannot be measured and has no technical explanation. It can be detected only by listening, and there are many skeptics who do not hear it at all. I disagree that it is permanent. Unless there is an actual physical difference between two ends of a component, I believe it can be reversed by simply passing a signal for a period of time. I have heard directionality in speaker cables that were identical on both ends. One was reversed and some effect (call it directionality) became apparent compared to the other, but the differences disappeared after a time of transmitting signal, until one was reversed again, when directionality again became apparent. Any evaluation of a component cannot be made until that interval of time has passed. Instant comparisons between orientations of components might not be valid because directionality is a function of time. I believe that all passive components, even solder, are non-directional until they become "biased" by passing signal. Unless there is a physical difference between ends, those little arrows on cables serve no purpose other than looking cute and raising the price some people are willing to pay.
Of course, it costs nothing and can do no harm to obsess over which way a resistor or film cap or piece of wire should be mounted, and it provides the satisfaction that one has done everything possible to maximize performance. However, I completely ignored it and my amps sound amazing. Just by chance I probably got half the parts "correct," but not necessarily the same parts in each amp. There is a greater difference between left and right sides of my listening space, my speakers, my crossovers, and my ears than there is between my two amps. I've swapped them left/right a number of times. Perhaps both amps are equally compromised!
I would be interested in hearing about other experiments and experience, especially regarding this amp. If you change direction of a component in ONE amp, does it sound different from the other? Immediately (of course it does!) and after playing a while?
Peace,
Tom E
Those, looking at datasheet, are very good caps but not Low ESR and axial.
For C1 and C2 you need a low ESR radial cap, mounting axial caps on radial pads will impact their decoupling effectiveness.
Hi Tom,
It's obviously my opinion, as your.
Yes, more later.
Yes and No...
As I've said several times resistors markings seems pretty consistent with the supposed 'directionality' in all the different brand and series I've tried.
I've only recently discovered that this is not the case with Wimas but seems much more consistent using the dent on plastic case, this is why some indication on preferred direction changed.
I wouldn't be so sure about it... burn-in is extensively used in the industry to assess reliability (usually defective parts will fail in the first hours of use).
I don't think it has not much to do with 'electrical theory' but more on changes on materials during use.
If this hypothesis has some merit it could be measured examing components and materials after a period of use.
I suspect that common distortion measures overlook somewhat noise characterization, more on it later.
Here your taking a conclusion based only, IMHO, on the analgy that both phenomens are controversial... if not, please elaborate.
This derive from the former...
And actually in most cases there's a physical difference...
All wires are drawn so metal crystals are aligned like a series of >>>>>>>> in the direction of drawning.
I've also read somewhere that some coatings used on parts like resistors exhibit a directional behaviour (I'll try to find again the reference).
Wound capacitors have an outer foil and according the direction they're used it can be measured a difference in picked up noise.
And we can keep going on...
Those physical differences will affect the signal?
This is controversial but a physical difference is present.
How you can affirm that?
That 'biasing' thing has some merit for some dieletrics and coatings, if I remember correctly polyester is one of those.
Obovioulsy this kind of directionality can be reversed but you're overlooking other directionality reasons, IMHO.
I'm sure of that, never said that that a 'reversed' component will sound bad but that it will sound better and more faithful.
Difference is not that big and randomized mounting in both channel will lead to pretty identical sounding channels.
In general such tiny differences are easier to detect with a mono signal.
I didn't extensive experiments but if you have both channels with coeherently oriented parts but one you will notice, with a mono signal, a slight imbalance.
When you change that single component orientation in just one of the channels so that all parts are coherent the two channels will sound more similar.
Parts 'directionality' and noise
An often overlookeed measure is the noise distribution Vs frequency.
Noise profile is IMHO relevant since, like noise shaping techniques used in the music industry demonstrate, it can shape sound so that is perceived by the human ear as colder, wamer, more dynamic, softer and so on.
Measured distortion of waveforms after applying different noise shaping profiles will be pretty identical but clearly perceived as different by the human ear.
Considering this aspect it became plausible that a wound capacitor could sound different according the direction it is mounted on circuit.
My hypothesis is that noise amount and its spectrum change according direction.
For resistors noise levels are pretty low so they will lead to neglegible, if any, difference in crude THD+N measures, maybe some hints can be sourced from THD+N Vs frequency measures.
An often overlookeed measure is the noise distribution Vs frequency.
Noise profile is IMHO relevant since, like noise shaping techniques used in the music industry demonstrate, it can shape sound so that is perceived by the human ear as colder, wamer, more dynamic, softer and so on.
Measured distortion of waveforms after applying different noise shaping profiles will be pretty identical but clearly perceived as different by the human ear.
Considering this aspect it became plausible that a wound capacitor could sound different according the direction it is mounted on circuit.
My hypothesis is that noise amount and its spectrum change according direction.
For resistors noise levels are pretty low so they will lead to neglegible, if any, difference in crude THD+N measures, maybe some hints can be sourced from THD+N Vs frequency measures.