| Gainclone HUM, THUMP problems - The solution - Click HERE for Original Thread |
| gainphile |
There are numerous resources on the internet to build a Gainclone. I have successfully built 4 of them without any dramas, except on one area: Hum and Thump. These can be minimal but in a very quiet night can be very disturbing. My latest build had hum audible at 10cm which is low enough - but not perfect.
Thump is a more serious issue for me. I use the gainclone to drive speakers actively, and without protection to the tweeter. Thump means bye-bye tweeters.
So I researched the issue for about 3 months and it was quite a character building experience :smash:. So many times spent trying, untangling wire, ecetera which cost me lots and lots of valuable listening and family time. It has too, cost me a speaker (a test one thankfully).
So now that I finally have a "black amp" so quiet that you could hear your neighbour fart :angel:, let's write it down to help beginners and non-engineers like me.
First of all there are excellent resources about grounding. I will list a few which had greatly helped me in this endeavour:
1. Peter Daniel's layout
2. Digi01's post about multi-channel amp grounding
3. Nuuk's (decibel dungeons) grounding
4. RJM Audio binary star grounding
5. LM3875's datasheet, very good ground loop explanation
For each of the contributors above I thank them for their insight about the topic. There is however, a lack of real wiring diagram for a complete, multi-channel, and specially non-PCB Gainclone systems.
So to cut to the chase, here is the final wiring diagram of a 4-channel Gainclone. Have a look and you may get the idea immediately. It is not overly complicated but there are minute criticalities which I will try to explain later.
Critical #1
'Separation' of signal ground and output ground. Notice that in the drawing there is a small ground point for inputs per channel, and one big ground point for everyting else. I use the term 'separation' loosely here as they are not really separated in electrical sense. There is a connection between 680R with the input ground, but it is not the same with connecting that input ground to the big centre ground point! This was my first mistake - thinking that connection points are all the same (thinking they measure 0 resistance on the ohm meter anyway)
Critical #2
Run the ground connection separately using cable to each relevant ground point. Yes there is a temptation to 'tidy up' and just use one cable and "hop" to the final ground point - it just won't work. Now, this may be different if you are using PCB as it may have beed designed well with large ground area etched.
Critical #3
Use different size of wire. Smallest for input ground, medium for output ground, and a really big one for PSU ground. This relates to point 1, and we try to make the signal flow from input ground to PSU ground - not the other way. Electric signal runs like water to the path of least resistance, and we want that path towards the PSU. During my experiment I found that using the same wiring topology, but also same wire throughout caused hum and more annoyingly loud THUMP when the amp is turned off.
In this photo you can see that my PSU is integrated with the first pair of Gainclone (my second pair would be mounted on top of this). The big cable come from PSU's ground.
Critical #4
Isolate input RCA ground from the chassis. Enough said, we want to 'control' the flow of signals to each ground point, and chassis is definitely not it. It took me quite sometimes to find RCA terminal with good isolation, found it at Dick Smith for $4 each.
Critical #5
Move the signal cables AWAY from any mains/transformes cables. I noticed that putting the signal wire really close to the amp's switch and cables produced noticeable hum. Good practice is to put potentiometers at the back, as close to the input as possible and use some kind of extention like Peter Daniel's chassis. But as you can see above I don't have the luxury of space by cramming 4 amps into such small chassis. I found out CAT5 cables for signal wiring is both neat and easy to tuck away from the mains/transformer.
Not so critical in terms of hum is that 5ohms resistor to AC ground. Some will question the wisdom of doing this in terms of safety, but it does help. I will leave this to you with disclaimer that yes, it is much safer to directly connect AC ground to the chassis.
There you go, hopefully my experience will help many, and if you're an experienced engineer please let us know if there are any inaccuaracy about the concept of this diagram. Thanks. |
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| DECKY999 |
With a proper PCB everything is smuch easier.
I assume you do not suggest to run all those individual ground wires if they are connected on a common ground plane of the PCB. Connecting input grounds to the star yes, but all of them,hmmm. |
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| gainphile |
| Yes. If you use PCB then the grounding would be designed properly then. Like in Peter Daniel's instruction. |
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| Leolabs |
| Actually there is an easier way:each channel has it's own star ground,then connect those 4 star grounds together at one point. |
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| gainphile |
| quote: | | Actually there is an easier way:each channel has it's own star ground,then connect those 4 star grounds together at one point. |
I'm sure I did that early in my experiment, but still got hum. |
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| gootee |
| quote: | Originally posted by Leolabs
Actually there is an easier way:each channel has it's own star ground,then connect those 4 star grounds together at one point. |
Sorry. But that would not be optimal.
It would partially defeat the purpose of the star grounding scheme: You'd still have the large and dynamic ground-return currents sharing the same conductor, with each other as well as with the signal input's ground reference point.
The ground-return conductor that they share has impedance, i.e. resistance and inductance, at least. The various return currents all induce voltages across that impedance, according to both V = IR and V=L(di/dt), where R and L are part of the shared conductor's impedance, i is current magnitude, and di/dt is rate-of-change of current magnitude. [The induced voltages can very easily be 10's of mV (or even 100's of mV), peak-to-peak.]
The induced voltages all add together and appear back at the non-ground end of the ground-return conductor, and everywhere it connects.
That means that the signal input ground reference point would then not be 'zero volts'. It would be varying according to the voltages induced across the shared ground-return conductor.
The amplifier only sees, as its input signal, the voltage-difference between the signal input point and the signal input ground reference point. So all of those nasty voltage variations would be directly arithmetically summed with the input signal. Not good. |
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| salesmonster |
Gainphile: Thank you for taking the time to share your hard-earned knowledge so throughly. The graphics and pictures are great too!
I dealt (somewhat successfully) with a HUGE turn-on thump issue with my first amp build a few months ago. It almost soured my from building anything else. I can see where this would have saved me a lot of hours. And now I see things I should consider doing next time I have the case open to chase down the last few hum gremlins.
Thanks again!
:) |
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| gootee |
| quote: | Originally posted by DECKY999
With a proper PCB everything is smuch easier.
I assume you do not suggest to run all those individual ground wires if they are connected on a common ground plane of the PCB. Connecting input grounds to the star yes, but all of them,hmmm. |
If the power supply is on the same PCB, then with a ground plane you wouldn't need separate conductors, except maybe still for the input ground reference.
If the power supply is on a different PCB, a ground plane on the amplifier PCB doesn't do as much good. It might be OK, as long as you use a separate wire for the input ground return (since any induced ground bounce voltage, there, gets directly amplified by the gain of the amp). But why not also split up the grounding for the speaker return and the power/decoupling return? The speaker return, especially, can have very large and dynamic currents. Why let it modulate your power rails? It's only one more wire, after all. And the speaker return-current doesn't need to go back to the PCB, anyway. |
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| gootee |
Hi gainphile,
Thanks for posting your diagram! That's a great idea.
I am not completely certain, at the moment, but, I think it might be better to have the power pins' decoupling grounds connected at the chipamp, which would mean that they'd have to (or might as well, at least) share a single ground-return conductor.
Did you try it with them connected at the chip, and still get hum?
If the power pins' decoupling grounds are NOT connected at the chipamp, then it would probably be a good idea to add a small capacitor, 0.1uF or 0.22 uF, directly between the two power supply pins of the chip. |
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| gootee |
Hi gainphile,
AndrewT will probably soon comment on your 5-Watt 5-Ohm 'safety disconnect' network. :-) By the way, he recently started a very good thread about 'safety disconnect' networks, with some actual high-current fault-test results, IIRC.
I think that many people also connect a very-high-current bridge rectifier in parallel with the resistor, and also put a small-value (0.1 uF) capacitor in parallel with the resistor. And, very often, the resistor's value is somewhere from 10 Ohms to 100 Ohms.
As I'm sure you know (besides lifting the system ground slightly above any disturbances in the earth ground, I guess it is), the main idea is to be able to pass a worst-case fault current, for a long-enough time to allow a mains circuit breaker to trip. [That's also why the safety disconnect network should not have solder used to attach it. It must be bolted or welded, since a large fault current could possibly melt solder, undoing the safety connection to earth ground.]
The concern is, I think, that the component(s) in the disconnect network might fail before the mains circuit breaker trips, allowing a lethal fault condition to remain, powered by the mains.
Your 5-Watt resistor's datasheet should indicate how long it can survive various overload conditions. Assuming that the 5-Ohm resistor had 115VAC applied across it, the current through it would be 23 Amps RMS, giving a power dissipation of 2645 Watts.
That sounds like a lot. But I regularly dissipate almost 1000 Watts in a similar 5W resistor, for up to tens of milliseconds or so at a time (but at widely-separated times, such as no more than once every few minutes), and the resistor never even gets detectably warmer to the touch.
At any rate, a couple of huge anti-parallel diodes (or series pairs in anti-parallel, for more separation voltage from earth ground disturbances), or a large bridge rectifier, if placed in parallel with your 5W resistor, would help to make your system safer. (And there must be some good reason why most people also use a parallel 0.1uF capacitor.)
Sorry to have blathered-on, for so long, about all of that.
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P.S. How is your power supply configured? I have seen questions from people wondering how to avoid hum when using a single supply to power multiple chipamps. If you could make a schematic, or better yet maybe, a layout and wiring diagram, and show exactly how you did the grounding, that might be extremely helpful for a lot of people. |
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| gainphile |
You're most welcome !
This is nothing new as I got the information from those links at the start of the article. Just emphasizing few critical points.
Of course there are more elegant and simpler way like using good PCB but I think the concept is the same. |
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| AndrewT |
Hi Gain,
I think Tom has explained the Safety implications well enough for you to take action AND modify the diagrams in post1. |
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| danielwritesbac |
| Hi Gainphile! I'm so curious. What are the 8 little green Tracon 100v Polyester caps, and what do they do to the bridge rectifiers? It looks cool. . . |
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| valleyman |
| Thanks, very helpful post. I'm about to assemble a couple of chip amps and was wondering about grounding. You've solved my problem |
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| gainphile |
| quote: | | Hi Gainphile! I'm so curious. What are the 8 little green Tracon 100v Polyester caps, and what do they do to the bridge rectifiers? It looks cool. . . |
They are snubber capacitors. Supposedly to surpress HF ripple but I really don't know what they do. I just followed the diagram from:
http://diyaudioprojects.com/Chip/Sy...clone/index.htm |
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| Mike514ml |
Thanks Gainphile and everyone else for the excellent posts.
I've got a couple of newbie questions.
I realize that the exact wire gauges may not be critical, but could you give me an idea of the relative sizes of the small, medium and huge ground wires?
Also, I'm currently finishing up a BrianGT 3875 dual mono chipamp kit (it's been lying around here for a LONG time), and was wondering if it would reduce the hum and thump potential more if it's built with single or dual power supply boards.
GooTees' 'antiparallel' diodes had me a bit confused, so I Google'd 'audio safety ground disconnect' and came across a page on the ESP site with a wiring diagram. I assume that this is what you meant when you talked about adding a bridge rectifier and capacitor?
http://sound.westhost.com/earthing.htm
Again, thanks everyone. This post has got me interested in putting together a hand-wired, thumpless 'black' amp next. That way, the next time my wife asks me what we're going to do with all of my speakers, I can tell her not to worry, I'm building amplifiers to power them :D
Mike514ml |
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| gootee |
| quote: | Originally posted by Mike514ml
Thanks Gainphile and everyone else for the excellent posts.
I've got a couple of newbie questions.
I realize that the exact wire gauges may not be critical, but could you give me an idea of the relative sizes of the small, medium and huge ground wires?
Also, I'm currently finishing up a BrianGT 3875 dual mono chipamp kit (it's been lying around here for a LONG time), and was wondering if it would reduce the hum and thump potential more if it's built with single or dual power supply boards.
GooTees' 'antiparallel' diodes had me a bit confused, so I Google'd 'audio safety ground disconnect' and came across a page on the ESP site with a wiring diagram. I assume that this is what you meant when you talked about adding a bridge rectifier and capacitor?
http://sound.westhost.com/earthing.htm
Again, thanks everyone. This post has got me interested in putting together a hand-wired, thumpless 'black' amp next. That way, the next time my wife asks me what we're going to do with all of my speakers, I can tell her not to worry, I'm building amplifiers to power them :D
Mike514ml |
Yes. Figure 3, IIRC. |
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| gmilitano |
Those small bypass caps on the rectifier bridge reduce the diode switching noises and results in cleaner DC. |
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| AndrewT |
I see that the Safety Earth connection is still shown wrongly in post1.
When are you planning to ask the Mods to substitute a safe diagram? |
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| gainphile |
| I got the diagram with no 5W resistor. How do I update the diagram? |
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| AndrewT |
| Does anyone have a view on whether the two decoupling caps (in post1) should be connected together first and then taken to the Audio Ground? |
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| gootee |
| quote: | Originally posted by AndrewT
Does anyone have a view on whether the two decoupling caps (in post1) should be connected together first and then taken to the Audio Ground? |
My view is that they SHOULD be connected together, near the chipamp, and should also connect to ground very close to each other, there. Otherwise (or even additionally), another small cap should connect directly between the V+ and V- power pins. |
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| AndrewT |
Hi Gootee,
I have already sent him a private message with instructions on where to find the less dangerous disconnecting network and how to contact the moderators to remove the dangerous diagram and substitute the safer one.
It's just a pity he does not realise how many newbies may have read his first post in the intervening 17days of inactivity. |
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| gootee |
| quote: | Originally posted by AndrewT
Hi Gootee,
I have already sent him a private message with instructions on where to find the less dangerous disconnecting network and how to contact the moderators to remove the dangerous diagram and substitute the safer one. |
Very good.
| quote: |
It's just a pity he does not realise how many newbies may have read his first post in the intervening 17days of inactivity. |
Agreed. |
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| BWRX |
| quote: | Originally posted by AndrewT
contact the moderators to remove the dangerous diagram and substitute the safer one. |
The image is hosted on photobucket. All that needs to be done is to change the link url in the post to the url of the new image. Post the url of the new image and we can change it. |
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| gainphile |
| quote: | Originally posted by Mike514ml
I realize that the exact wire gauges may not be critical, but could you give me an idea of the relative sizes of the small, medium and huge ground wires?
Also, I'm currently finishing up a BrianGT 3875 dual mono chipamp kit (it's been lying around here for a LONG time), and was wondering if it would reduce the hum and thump potential more if it's built with single or dual power supply boards.
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Hi Mike, I don't understand about wire gauges so I posted that picture (I have medium-size thumb :D). Basically the largest wire is from good speaker cable about 4mm in diameter, the smallest is jumper cable about 0.5mm diameter. The middle size is about 1.5mm diameter.
Mine is built using single supply board for 4 channels. I don't know how using 4 PSU will help more as my amp is very quiet ie. no hump/thump... |
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| BWRX |
You can only edit your posts for up to 30 minutes (I think) after posting. After that you need to ask a moderator to do it.
I've updated the url in your first post so the correct diagram should now show up. |
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| gainphile |
Thanks for updating the diagram :cool:
Now, about "private messages" ... where is this located? I can't find private messages as AndrewT mentioned above? |
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| ratza |
| Click on member then go to 'Click here to email ----' |
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| AndrewT |
or go to the bottom of a posting and choose to click on "Email" or "report"
Email goes to the poster and report goes to the Moderating team. |
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| Mike514ml |
| quote: | Originally posted by gainphile
Hi Mike, I don't understand about wire gauges so I posted that picture (I have medium-size thumb :D). Basically the largest wire is from good speaker cable about 4mm in diameter, the smallest is jumper cable about 0.5mm diameter. The middle size is about 1.5mm diameter.
Mine is built using single supply board for 4 channels. I don't know how using 4 PSU will help more as my amp is very quiet ie. no hump/thump... |
Gainphile,
Thanks! The speaker return wire is bigger than I thought. I can work with this info.
Of course, it's kind of ironic that your amp sounds better if you don't use gigantic wire for the speakers! :D At least internally.
I think I'll go ahead and use a single supply board for my BrianGT amp, since I'm using a single (center tapped) transformer. It'll simplify the ac wiring. Of course, I'll stuff the largest wire I can into the ground connections!
Thanks again,
Mike514ml |
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| jaycee |
In my own amp I have as follows:
Each channel's rail decoupling capacitor grounds have a common ground trace. This include the ground pin of the LM3886. This is returned via one fairly thick wire (same thickness as the power supply wires) to the central ground.
Signal grounds are seperated and connected at one place - the input jacks. This in turn is connected to central ground via a 10 ohm resistor.
Speaker grounds are returned direct to central ground. The zobel networks are on the output posts, so the speaker ground is also the return for the zobel.
The central ground is on the capacitor side of the supply - not the rectifier.
Central ground is connected to chassis earth via a 10 ohm 3W resistor bypassed with a 100nF capacitor. I could add diodes but I suspect this combination would allow more than the 30mA trip point of the household RCD to flow, so it is safe.
No hum heard at all :) |
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| Baka |
| quote: | Originally posted by jaycee
In my own amp I have as follows:
Each channel's rail decoupling capacitor grounds have a common ground trace. This include the ground pin of the LM3886. This is returned via one fairly thick wire (same thickness as the power supply wires) to the central ground.
Signal grounds are seperated and connected at one place - the input jacks. ..
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Hi jaycee,
I'm here in a little doubt since, for example, Mick Feuerbacher on his site http://dogbreath.de/Chipamps/ThreeR...hreeResAmp.html (comment with figure 6) connects the ground pin (pin 7) of the LM3886 to signal ground.
What should be the better approach?
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No hum heard at all :)
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No hum/noise with ear close to the woofer/tweeter with, let's say, a volume pot up to 12 clock?
Thanks,
Baka |
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| jaycee |
| quote: | Originally posted by Baka
Hi jaycee,
I'm here in a little doubt since, for example, Mick Feuerbacher on his site http://dogbreath.de/Chipamps/ThreeR...hreeResAmp.html (comment with figure 6) connects the ground pin (pin 7) of the LM3886 to signal ground.
What should be the better approach?
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I never liked point to point construction. I also dont agree with a number of things in his design, for example, he has an outboard power supply consisting of the transformer and some 30,000uF of capacitance per rail - but then he has a small power supply connector with tiny pins.
His star grounds are at the chip. He doesn't really connect pin 4 to signal ground - he just doesnt have any isolation between the two grounds.
You can try it, but I would think it's more prone to hum myself.
| quote: | Originally posted by Baka
No hum/noise with ear close to the woofer/tweeter with, let's say, a volume pot up to 12 clock?
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No hum - some hiss, but no hum :) |
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| ratza |
| quote: | Originally posted by Baka
No hum/noise with ear close to the woofer/tweeter with, let's say, a volume pot up to 12 clock?
Thanks,
Baka |
On my system there's no hum with the pot at maximum, the amp is dead silent. I use a LM3886 at +/-30V, 3x4700uF/rail, 330uF/rail on the boards. Speakers have 92dBm efficiency. I will make a diagram to explain better. |
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| Baka |
| quote: | Originally posted by jaycee
I never liked point to point construction. I also dont agree with a number of things in his design, for example, he has an outboard power supply consisting of the transformer and some 30,000uF of capacitance per rail - but then he has a small power supply connector with tiny pins.
His star grounds are at the chip. He doesn't really connect pin 4 to signal ground - he just doesnt have any isolation between the two grounds.
You can try it, but I would think it's more prone to hum myself.
No hum - some hiss, but no hum :) |
Thanks, jaycee.
I have already implemented the point to point construction like it was explained on this thread, but on the gainphile's schematic ground pin on the chip and the way it should be connected is missing. Maybe LM3875 doesn't have the ground pin.
Other than that I discovered that a volume pot body itself (Alps blue) generates a strong hum and noise disregarding the properly connected its ground pins! When I touched the pot audible hum and noise could be heard through the speakers. I have tried then to connect a metal part of body to a central ground and eventually solved the problem.
Should I, maybe, connect the body via disconnecting network (R||C||D1||D2) to earth rather than power and signal central ground since the pot is additionally connected to extension rod and aluminum knob?
With my ~85dB efficient speakers with a volume pot up to 12 clock I can detect some hiss but close to the tweeter. |
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| ratza |
| There you go, I hope it's easy to understand. |
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| jaycee |
| I've pretty much got what Ratza has drawn (well, the pot has now been replaced by an active preamp, but was initially as shown) except there is a 10 ohm resistor between signal ground and main ground. |
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| ratza |
I also had a resistor first time when I powerd it up, but removed it afterwards. The sound is just the same, as well the lack of hum and noises. The only noise I have is when I power down the amp, due to the fact that the pot is very close to main power cord, switch and toroid.
Funny part: some days ago I moved my spekars around and they have hum while they're not connected to the amp:bigeyes:. It took me some time to realize that the passive filters where very close to a transformer. |
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| Baka |
| quote: | Originally posted by ratza
There you go, I hope it's easy to understand. |
Yes, that's it. Wire from gnd leg of chip to central ground.
Thanks. |
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| chylld |
after upgrading my speakers i'm starting to hear a buzzing/humming from my gainclone as well.
i'd love to follow gainphile's tips (very well written btw!) however i'm using the lm3886 kit from chipamp.com, which iirc has signal ground, output ground, power ground and "chassis ground" all connected on the amp PCB.
i'm currently using the same size wire for all ground connections, and am wondering given that all the ground connections are already connected together on the amp PCB, would using different wire sizes be futile? |
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| DECKY999 |
| For chipamp.com kit - bring two ground wires together (as thick as you can fit) from each of the PCBs - connect them to one side of the Elliot Sound ground breaker (10R||CAP||D1||D2) . Connect the other side of the ground breaker to the chassis ground point. Connect the mains ground to the same chassis ground point. You should not have any hum after this. |
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| chylld |
| quote: | Originally posted by DECKY999
For chipamp.com kit - bring two ground wires together (as thick as you can fit) from each of the PCBs - connect them to one side of the Elliot Sound ground breaker (10R||CAP||D1||D2) . Connect the other side of the ground breaker to the chassis ground point. Connect the mains ground to the same chassis ground point. You should not have any hum after this. |
thanks for the reply.
from which ground holes on the amp boards should i run the ground wire? at the moment I am running the ground cables from the "CHG" chassis ground holes to what i believe is a similar ground loop breaker (10R 5W resistor, 0.1uf cap, 35A 400V bridge rectifier) which then connects to the chassis/mains earth. i have verified that the zero volt line is raised above the chassis/earth by at least 10ohms.
so if i just thicken the cables coming from the CHG holes it should be fine? (at the moment i am using all cables of the same thickness) also am i correct in assuming that i need to use this thick cable all the way from CHG to the breaker?
btw here is a pic of my loop breaker:
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| chylld |
| quote: | Originally posted by DECKY999
For chipamp.com kit - bring two ground wires together (as thick as you can fit) from each of the PCBs - connect them to one side of the Elliot Sound ground breaker (10R||CAP||D1||D2) . Connect the other side of the ground breaker to the chassis ground point. Connect the mains ground to the same chassis ground point. You should not have any hum after this. |
ok i did this, upgraded the chassis ground wires to mains cable (largest size that i have that will fit in the PCB) and joined them as soon as possible to a thick subwoofer cable (about 4-5mm2) and then ran this to the loop breaker.
the noise is still there :(
is there an audio sample on the web somewhere of the humming? perhaps i'm tackling the wrong problem... |
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| chylld |
| quote: | | is there an audio sample on the web somewhere of the humming? perhaps i'm tackling the wrong problem... [/B] |
i managed to capture the sound of the humming/buzzing i'm experiencing, another piece of hi-fi equipment was malfunctioning which made the gc amplify the noise enough to record it. here's the sound that i hear:
http://temp.jw.id.au/gcbuzz.mp3
you can hear it at a distance of about 1m, and the volume control has absolutely no effect on it. |
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| AndrewT |
Hi,
that buzz is due to the high current charging pulses that flow from the secondary through the rectifier into the smoothing caps.
This is probably connected electrically due to a wiring error to the clean side of the amp supply or to the audio ground.
It may be EMI being radiated from the pulsing side and interfering with the signal side. |
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| chylld |
| quote: | Originally posted by AndrewT
Hi,
that buzz is due to the high current charging pulses that flow from the secondary through the rectifier into the smoothing caps.
This is probably connected electrically due to a wiring error to the clean side of the amp supply or to the audio ground.
It may be EMI being radiated from the pulsing side and interfering with the signal side. |
that seems to correlate with another observation i made: when i turn the power off, the buzzing goes away immediately, even though music still plays for a few seconds. the power switch cuts off both the live and neutral connections, i.e. the whole 'dirty' side of the PSU, so i believe my problem is something power-related rather than ground-related.
here is a pic of my amp layout:
with the exception of the ground loop breaker, i have followed the chipamp.com instructions exactly; so i do not believe there is a wiring error.
if it is EMI, how can i fix it without taking the PSU components out and putting them in a separate box?
also, would it help if i fitted snubbing capacitors to the rectifier diodes? |
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| AndrewT |
Hi,
try reducing the radiating area of the primary side and of the charging side.
twist the mains input pair together.
twist the twin secondaries together.
Twist the rectified outputs together.
Finally slacken the transformer fixing bolt and rotate the transformer in small steps and listen/measure, the effect of each new position, at the output. |
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| chylld |
| quote: | Originally posted by AndrewT
Hi,
try reducing the radiating area of the primary side and of the charging side.
twist the mains input pair together.
twist the twin secondaries together.
Twist the rectified outputs together.
Finally slacken the transformer fixing bolt and rotate the transformer in small steps and listen/measure, the effect of each new position, at the output. |
just spent the whole evening trying to debug my buzzing problem, starting with your helpful suggestion.
1) tried twisting the primary and secondaries together: no difference.
2) wasn't convenient to twist the rectified outputs together, so i just unbolted the power supply board and held it as far away from everything else as possible: no difference.
3) tried zip-tying the rectified output wires, no difference. tried moving them around as far as they would go while the amp was running, no difference.
4) unbolted the transformer a bit and rotated it every which way, no difference.
5) unbolted the transformer and stood it up vertically outside the case: NOISE IS GONE! something doesn't like being too close to the transformer!
6) put the transformer back in, and moved the loop breaker away from the transformer all the way to the other end of the case: buzz is still there.
7) popped the IEC socket out and held it as far away from the case as possible: no difference (buzz still there.)
8) tried standing the transformer on 1cm (3/8") tall rubber feet inside the case: no difference.
9) stood the transformer vertically inside the case: buzz is still there. if i move it away from the heatsink, buzz gets quieter; if i move it towards the heatsink, buzz gets louder. moving it towards/away from the power supply board makes no difference to the buzz.
10) unbolted the heatsink and elevated it using (non-conductive) foam pads: buzz still there.
11) constructed a metal shield out of aluminum sheet and placed it between the transformer and the heatsink, ensuring that the shield was electrically connected to ground: buzz still there.
i think that's all i tried. the noise seems to be inversely proportional to the distance between the transformer and the amp boards / heatsink.
is there anything else that i can try?? |
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| DECKY999 |
Try different transformer :D - joking!
You said when you trip the switch the noise goes away but the music is there while the caps are discharging.
OK try puting larger metal disk on top of the transfomer. Twist the primary wires and the socondary wires, twist +V-GND and -V-GND (output from your PSU) and move them away from the transformer. Consider using a shielded twisted pair for the voltage output. Maybe also turn your PSU PCB for 90deg so the output side is facing back of the case rather then the heatsink. By the way - is the noise equal level on both L and R? Check if your transforemer fixing screw is making good contact to the chassis.
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| chylld |
| quote: | Originally posted by DECKY999
Try different transformer :D - joking! |
actually not an unreasonable recommendation... been doing a lot of searching on transformer hum and apparently lower quality units hum more than higher quality ones.
| quote: | Originally posted by DECKY999
You said when you trip the switch the noise goes away but the music is there while the caps are discharging. |
correct, hence i believe the problem lies somewhere before the power caps.
| quote: | Originally posted by DECKY999
OK try puting larger metal disk on top of the transfomer. Twist the primary wires and the socondary wires, twist +V-GND and -V-GND (output from your PSU) and move them away from the transformer. Consider using a shielded twisted pair for the voltage output. Maybe also turn your PSU PCB for 90deg so the output side is facing back of the case rather then the heatsink. By the way - is the noise equal level on both L and R? Check if your transforemer fixing screw is making good contact to the chassis. |
when i had the wires twisted, i tried moving them around but it made no difference to the buzz. I tried this with the wires untwisted as well, no difference. currently the wires are untwisted and as physically far away from the transformer as possible, no difference.
i have tried turning the PSU PCB 90 degrees every which way, it made no difference.
the noise is equal and the same on both left and right channels. the power cables going the left channel's amp PCB are about 3x closer to the transformer than the right channel's ones, so given that the noise is of the same volume in both channels, and that the noise does not change at all when moving these cables around, leads me to believe that these cables are not the culprit and shielding/twisting will not help.
the transformer screw is making good contact, and i tested with the screw in place as well as not in place; no difference.
in my searching i found a schematic for a dc blocker (http://diyparadise.com/dablok.html) and i bought the parts today and intend to try it out tonight. i really hope it works, otherwise i might be faced with having to build a separate box for the power supply (and keeping that box far away from the amp!) |
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| owen |
Lets get back to basics.
The LM packages with metal tabs have -ve DC on the smoothed side of the PSU.
Something on the heatsink is acting as an inductive coupler for the AC field from the transformer - a steel bolt or screw perhaps.?.. If so, this will induce an AC voltage in the heatsink, that will in turn modulate the smoothed -ve rail on the PSU. That produces HUM.
As you are trying to block an alternating magnetic field, I personally would choose a ferro magnetic material (thin sheet steel) to screen between the TX and the heatsink.
What is your earthing like - have you decoupled signal earth from PSU earth using the classic parallel cap (typically a few millifarads) and a resistor (typically 100 ohms IIRC).
Just a few thoughts.
Owen |
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| chylld |
hi owen, thanks for your reply, more than happy to get back to basics!
the lm3886 chips i have are fully insulated (lm3886tf), i don't think they have metal tabs as such. don't have a pic of the back, but here's a pic of the front:
the heatsink is the following unit: (link) and has an extension coming out in the middle of the heatsink onto which i've mounted the chips. the heatsink is secured via 3 zinc-plated bolts to a couple of metal brackets which are bolted to the bottom of the case. i've tried unbolting the heatsink and sitting it on foam pads but that didn't reduce the noise at all.
i'm not sure what a ferro-magnetic material is, but i assume steel is and aluminum isn't? i've already tried aluminum and it didn't work at all, but i can probably find some steel scrap and give that a shot.
earthing is done using the ground loop breaker described on this page, the amp's signal/output/power ground all connect to the zero volt line which is only connected to the chassis/earth through this loop breaker. i don't think my problem is an earthing one however, as the noise is inversely proportional to the distance between the tx and heatsink, and the noise goes away as soon as power is cut (but audio still plays off the remaining charge in the power caps.)
it makes a lot of sense for the heatsink to be involved somehow; the tx is about 50% closer to the left channel's amp board than the right, but the noise is the same volume in both channels. *rummages around for random sheet steel* |
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| AndrewT |
| quote: | Originally posted by chylld
.........the amp's signal/output/power ground all connect to the zero volt line |
no,
the audio ground should be separate from the zero volt line.
Then connect the zero volt line to the audio ground.
This avoids the charging currents flowing around the secondary/rectifier/smoothing caps circuit from contaminating the audio ground.
That is also the reason for twisting the charging circuit wires, to minimise the effect of these current pulses by reducing the radiating area between the flow and return wires.
Is there any orientation of the transformer that achieves both close proximity and lowest buzz level?
BTW,
the transformer leads should all be swapped to flexible cable/cord and not solid core to allow for this experimentation. |
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| chylld |
i would separate the audio ground if i could, however since the audio ground and power ground are connected together on the amp pcb (chipamp.com lm3886 kit) this is not an option. :(
i tried twisting the wires and it had no effect.
i tried rotating the tx around the y-axis (i.e. spinning it around on the spot) which had no effect. i also tried standing it up on its edge with no effect. of all the things that i tried, only the distance between the tx and the heatsink showed any correlation to the buzz. |
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| chylld |
ok it's almost 2am here, and i've spent the last few hours trying to debug the problem again. i figure it's silly working with mains power when you're tired and everyone else is asleep, so i stopped.
i found that the aluminium sheet i used as a shield before wasn't ferromagnetic, so i went and found some steel and constructed a wall around the transformer, covering >95% of the line of sight to the heatsink. it extended from the bottom to the top of the case, and i verified that a) the steel was ferromagnetic, and b) the steel was grounded to the case well. result: noise is still there.
so i tried twisting the rectified output wires since i realised i can do it in place, except for a small parallel non-twisted bit in the middle, but >90% is twisted. noise is still there. (leaving it twisted cos it looks pretty)
so then i tried the dc blocker. used 2 diodes to account for up to 1.4V of DC, soldered everything together, heatshrinked it all and connected it up: yep, you guessed it, noise still there.
so i figure the loop breaker is somehow making things go bad (i wasn't thinking clearly at the time) so i uninstalled that and tested it again: noise still there. the loop breaker actually works to eliminate computer noise i get through the mains ground, so i'm glad i don't have to throw that one away!
so now i'm back to square one. guys i really appreciate all the advice so far, and i'm honestly giving this my best shot. a solution to my transformer <-> heatsink hum cannot come any sooner!!! |
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| pacificblue |
Could it be that the trick does not only lie in the distance between transformer and heatsink, but also in the fact that the transformer is removed from the amp case that looks very ferromagnetic.
Does it reduce the hum, when you lift the transformer up even without separating it further from the heatsink? I. e. put a sufficiently thick piece of wood or plastic below it, and so separate the transformer from the bottom and the sides? That would indicate that your case is the electromagnetic conductor.
Solutions could then be to move the transformer to a separate housing outside of the amplifier. Or to build a small shielding housing around the transformer, and mount that with as much separation as possible on all sides into your amplifier case. |
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| AndrewT |
Hi,
or use an all aluminium casing.
Try assembling the whole amp without any casing, but safely, and see/hear if the noise goes away. |
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| Nordic |
| arew your RCA sockets isolated from the case? |
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| chylld |
| quote: | Originally posted by pacificblue
Could it be that the trick does not only lie in the distance between transformer and heatsink, but also in the fact that the transformer is removed from the amp case that looks very ferromagnetic.
Does it reduce the hum, when you lift the transformer up even without separating it further from the heatsink? I. e. put a sufficiently thick piece of wood or plastic below it, and so separate the transformer from the bottom and the sides? That would indicate that your case is the electromagnetic conductor.
Solutions could then be to move the transformer to a separate housing outside of the amplifier. Or to build a small shielding housing around the transformer, and mount that with as much separation as possible on all sides into your amplifier case. |
the bottom half of the case (what you see in the photos) is aluminum which is non-ferromagnetic, and the top is steel which is ferromagnetic.
i tried standing the transformer up on 1cm tall rubber feet, didn't help the noise at all.
when i tried my ferromagnetic shield, i moved it around up and down side to side (as much as possible) and the noise character didn't change at all. the shield was made from an arrangement of flexible bracket steel strips, you can see here in this pic of it that it reaches around pretty much all the way (right third covered with electrical tape since it was close to the power supply PCB):
i verified several times that it was electrically connected to the chassis, but alas, no cake. i really expected this one to work :confused:
| quote: | Originally posted by AndrewT
Hi,
or use an all aluminium casing.
Try assembling the whole amp without any casing, but safely, and see/hear if the noise goes away. |
i tried with the cover on and off, no difference to the noise.
| quote: | Originally posted by Nordic
arew your RCA sockets isolated from the case? |
yes, rca sockets as well as power ground and output ground are all isolated from the chassis using a ground loop breaker. |
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| AndrewT |
| and shorten that transformer bolt. Then insulate over the washer and bolt to prevent electrical contact with the lid. |
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| pacificblue |
But you do hear that buzz from your speakers, right? Or are we talking about a resonating chassis?
| quote: | originally posted by chylld
i'm starting to hear a buzzing/humming from my gainclone |
You can check that best with the speakers disconnected, because the human ear is not so good in locating sources at low frequencies.
If it is not a resonating chassis, do you have that noise also with all inputs disconnected? |
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| chylld |
| quote: | Originally posted by AndrewT
and shorten that transformer bolt. Then insulate over the washer and bolt to prevent electrical contact with the lid. |
the bolt in the pic is actually about an inch away from the lid already. if it was near/touching the lid there would be a chance of shorted turn phenomena however this was not the case.
| quote: | Originally posted by pacificblue
But you do hear that buzz from your speakers, right? Or are we talking about a resonating chassis?
...
If it is not a resonating chassis, do you have that noise also with all inputs disconnected? |
the buzzing was from the speakers, not the transformer itself. (i.e. electrical noise, not mechanical noise.) the noise presented itself with inputs connected or disconnected (which made it easy to test, just plug in the speakers and the power and turn it on: bzzzzzzzzzzzzzzzzzzzzzzzz.
however...
PROBLEM SOLVED!!!!!!11
after a whole day's work i am glad to contribute the following solution to gainclone hum. i can now put my ear literally within ear-hair's distance away from the speaker and i cannot hear ANYTHING. (unless i'm playing music of course!)
i assume the pictures are self-explanatory. the transformer box (i call it "chibi") sits on the floor about 3 feet underneath the amp.
can i just say: transformers suck.
thanks to all who helped. your collective perseverance kept me motivated enough to reach this point. |
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| rabbitz |
That looks like an Altronics transformer and I've never had a problem with induced noise from them. I've had 1 fry and another was noisy, but generally fine.
I'm sure there was more to your problem as I've used these right next to the amp PCB without issues. The main thing is that it's working well.
Once thing you might look at for future projects is to twist your secondary wire pairs or any other AC line.
If you are looking for good transformers in Australia, get a Harbuch (in Sydney). They make Antrim under licence. |
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| chylld |
| quote: | Originally posted by rabbitz
That looks like an Altronics transformer and I've never had a problem with induced noise from them. I've had 1 fry and another was noisy, but generally fine.
I'm sure there was more to your problem as I've used these right next to the amp PCB without issues. The main thing is that it's working well.
Once thing you might look at for future projects is to twist your secondary wire pairs or any other AC line.
If you are looking for good transformers in Australia, get a Harbuch (in Sydney). They make Antrim under licence. |
good eyes! that is indeed an Altronics 160VA 2x25V M5325 transformer.
i tried twisting primary, secondary and rectified output lines, none of those changes had any effect.
the most reasonable explanation is owen's theory that the particular heatsink i bought was acting as an inductive coupler, transmitting the noise to the amp PCBs.
i had eliminated ground and emi problems, so there are very few (if any) other explanations. i even went so far as to try a dc blocker, which no matter how you look at it, is not the safest thing you can do with an amp.
so i could either try a new heatsink with a 50% chance of working, or i could move the transformer out of the main case which had a 99% chance of working. not the cheapest solution, but my goal was to fix the problem and it is now fixed :) |
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| rabbitz |
| The joys of amp building. ;) |
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| Sparky OR |
I've been lurking, slowly building DIY Kit 50 LM1875 amps. The first unit I assembled after getting the PS working. It sounded fine, plenty of power for my 4 ohm T&B 4" TL spkrs. Second unit, lots of hum. Tried different grounding rountines, the AC gnd is still not hooked up, running through a Variac. Well, using a star ground point, and feeding EVERYTHING to it resulted in getting rid of hum. Thanks for all the info!:) Now I will have to work on reincorporating the Alps 50k pot back in, finallizing a chassis, and putting in a proper AC (safety) ground.
The only changes I did to the kit50 was lower R4 from 10l to 5.6k, it uses 180k fb resistor. It was interesting that the hum only occurred when I had both inputs hooked up to my little Panasonic CD player. Only one connected, no hum. |
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| chylld |
one thing i've been curious about with my transformer box... there are 2 cables going from the transformer box to the main amp box, each one carries 25v ac. inside the amp box, this gets turned to V+/PG+ and V-/PG-.
so my question: what happens if i leave one of the cables unattached? (i.e. giving the chips only V+ or V-) |
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| pacificblue |
Simple answer. It won't work.
You must connect at least one of the PGs to have a ground reference for the amplifier. |
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| chylld |
| quote: | Originally posted by pacificblue
Simple answer. It won't work.
You must connect at least one of the PGs to have a ground reference for the amplifier. |
what if i have V+ and PG+ connected, but V- and PG- not connected? (that's what would happen if one of the cables wasn't connected) |
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| AndrewT |
| quote: | Originally posted by pacificblue
Simple answer. It won't work. |
again |
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| chylld |
| quote: | Originally posted by AndrewT
again |
thanks for the clarification. reason i asked is because i was afraid it would blow my speakers up:
| quote: | Decibel Dungeon wrote:
When I reconnected the amp, I found that I had an offset of 34 volts! After assuming that I must have a faulty chip, and ordering some replacements, further investigating found that the negative supply rail measured 0 volts at the amp but -36 volts in the PSU. A wire had come loose in the umbilical from PSU to amp and reconnecting it solved the problem. It was lucky that I had decided to check the DC offset that morning of I would have destroyed a speaker. |
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| AndrewT |
| quote: | Originally posted by chylld
thanks for the clarification. reason i asked is because i was afraid it would blow my speakers up:
|
it might.
measure the output offsets with the various disconnections that you think are possible. |
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| chylld |
| quote: | Originally posted by AndrewT
it might.
measure the output offsets with the various disconnections that you think are possible. |
ok these are the offsets i've measured (all in +/- volts):
both V+/V- connected: 0.002
only one connected: 1.94
only the other one connected: 0.49
so max of about 2V. i assume that's not a harmful voltage given that the AA (1.5V) battery polarity test is quite common and harmless? |
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| gainphile |
| Never ever test using your 'real' speaker :eek: ... buy a $5 fullranger :cool: |
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| AndriyOL |
I have build a parallel configuration amp, based on LM4780 chips but have some nasty hiss at low frequency response, but the bass is not gone at all.
My unconventional solution is a use of non-polarized 47uF Ci cap in parallel to 100nF MKT cap.
Gould it be from improper grounding?
Thanks in advance for answers. |
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| AndrewT |
| quote: | Originally posted by AndriyOL
I have build a parallel configuration amp, based on LM4780 chips |
post your schematic |
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| AndriyOL |
| quote: | Originally posted by AndrewT
post your schematic |
Here is the schematic, except that I use 1% tolerance Rout, 0,1% tolerance Rf resistors and 2200uF of Cs5, Cs6 caps, according to parallel configuration of a datasheet of LM4780. Also, if it is important, when I place an Rg resistor between Power Supply Ground and Signal Ground the hiss grows even further, depending on the value of the Rg resistor is used. The most clear that hiss I guess is on 20-40 Hz of frequency response.
I use two power supplies for four LM4780 chips.
Besides, there is an additional hiss I have from amp which appears when an input source is ON, however I followed the recommendations placed on this forum, related on proper grounding. I used the schematic, published by Ratza in Post 40. I have no PCB and use point-to-point wiring.
DC offset in quiescent mode is 9-12 mV. With load it arises to nearly 30mV.
Best Regards,
AndriyOL. |
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| AndrewT |
Hi,
the tolerances on R1, 3, 4 & 8 are too wide.
C1, 2, 4, 5 & 6 restrict the bass extension.
Short the input using a zero ohm RCA plug.
Where is the decoupling located?
Where is the input RF filter?
C5, 6 and C13, 14 should be connected to R11 & input (signal) ground.
Pins 12 & 19 are permanently connected to power ground. |
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| aurche |
| Why do you bother making those shity gay clones? They sound bad and have stabillity problems. |
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| ratza |
| quote: | Originally posted by aurche
Why do you bother making those shity gay clones? They sound bad and have stabillity problems. |
Maybe yours sounds bad or has stability problems but this can be caused by alot of factors. What loudspeakers are you using? Mine works great with a pair of DIY TQWP, there's plenty of power and very detailed. Well, not as detailed as the SE tube amp, but still... Are you sure you didn't make any mistakes on the PCB? |
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| aurche |
| I have heard hundrets of gay clones - they sound bad! The dont have 1/100 of the sound of my Estonia HIFI amp! |
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| lanchile07 |
You have heard hundres of gainclones?.and they all sounded bad? Wow! that is really bad luck buddy! Because, these amps if they are build properly.they can sound really good.I can see that you are a Gainclone hater...
I have had many good amps like: Marantz,Luxman,Adcom,Portal panache,Bryston,Arcam,Blue circle etc,etc.
These gainclones can put a good fight with the above amps.as I mention before...if you build it right! you can achive an excellent amp no doubt!.;) |
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| aurche |
Hi, again
Oh, you dont understand me! I am a DIYer for 30 years. When i got my present amp (the Estonia HIFI UM-010 - http://www.postimage.org/image.php?v=gx1Dp3nJ) i was so happy. It sounded so good. That was 20 years ago. I havent changed my amp since then and i havent felt the need to as well. No gainclone can beat my amp's sound :) I mentioned the problems of the gainclone, but it is good for beginers. No one I know can build something better than my amp. Excluding tube amps.
BYE |
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| lanchile07 |
"No gainclone can beat my amp's sound I mentioned the problems of the gainclone, but it is good for beginers. No one I know can build something better than my amp. Excluding tube amps.
BYE"
Well, as a "Beginner" (38 years old).I know these amps can kick some a$$ (if they are build right).
and for the... " No one I know can build something better than my amp"... lol,lol...it looks like you do not know many people...
but again I can be wrong...
As long as you are happy and "think" you have the best amplifier in the entire world and nobody can have or build a better amp then yours....you should be proud very proud...:smash: |
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| AndriyOL |
[QUOTE]Originally posted by AndrewT
[B]Hi,
the tolerances on R1, 3, 4 & 8 are too wide.
Hi, AndrewT.
I have tolerances on R3, 4 - 1%; R1, 8 - 0,1%(measured on tester).
I cannot understand you, what you mean - "restrict the bass extension". I have constructed it according to datasheet.
Decoupling located almost on IC pins.
What is the input RF filter? There is no any RF filter in datasheet. I have no RF filter, only Cin cap. Do I need this filter? (I don't even know what it is look like).
I already have connected C5, 6 and C13, 14 to R11 & input (signal) ground and pins 12 & 19 to power ground.
One more I forgot to write - my two heat sinks are not isolated from chips and carry 'V-' voltage rail and I'm not isolated my ground connections (links). - Is this critical? Perhaps, this is smth like Jackinnj wrote on post 5 of "lm4780 Zobal resistor burns immediately on Power ON" I guess.
Could the problem arise from utilising unpolarized caps?
Best Regards,
AndriyOL. |
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| aurche |
I want you to find millitary quality transistors, 0,125% tolerance resistors, build this circuit and say what is better this or gay clone of what sort you like.
Here is the schematic.  |
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| Sparky OR |
| Not exactly an enticing prospect for one who seems to be in the beginning stages of DIY eletronics...my 2p worth. Gainclones offer a way for a budding DIYer to make something for themself without having to understand all aspects of it, including PCB layout and construction, RF issues, biasing, etc. |
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| lanchile07 |
Well,0,125% tolerance resistors does not mean nothing to me.
as you can see they use ONE big cap 15000uf per channel...
it would be better if the use small ones like 3.300uf x5 or 2.200uf x7 per channel.but hey they are using 0.0000000001% tolerance parts right?.so it must be the best amp ever .lol...
Maybe you like the sound of this amp ,but for other people is not the sound they are looking for.
I am not saying gainclones amps are the best,but they can put a fight with some of the good commercial amps out there for sure...:smash: |
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| ratza |
| quote: | Originally posted by lanchile07
as you can see they use ONE big cap 15000uf per channel...
it would be better if the use small ones like 3.300uf x5 or 2.200uf x7 per channel.but hey they are using 0.0000000001% tolerance parts right?.so it must be the best amp ever .lol... |
It depends very much on the capacitor. There are industrial capacitors with huge charge/discharge currents, say around 30...50A. I rather put some of these inside instead of using many smaller ones. Anyway, aurche, there is no "best amplifier", just amplifiers which either suites your expectations or not. If you like the sound, then it's fine, don't expect everybody to agree with your choice. |
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| aurche |
The toroid is 900W, the cap has a diameter of about 5". Do you think it isn't enough? The sound is better than the sound from the most perfectly built gainclone. If you want better sound, gainclone is a lost cause...
The amp was made by an russian millitary factory that was obligated to make a public production. There were no more than 2000 amps made. The trasistors put in the amp are matched by their parameters and the same transistors were put into the tactical missiles of russia. Do you think the russians will put lousy transistor and parts into the missile that is destined to hit America?:bawling: :bawling: :bawling: :rolleyes: :D :D :devilr: |
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| AndriyOL |
| quote: | Originally posted by aurche
I want you to find millitary quality transistors, 0,125% tolerance resistors, build this circuit and say what is better this or gay clone of what sort you like.
Here is the schematic. |
Maybe I need some kind of factory production equipment to build the amp you propose?
What are the technical parameters of this amp?
Regards,
AndriyOL. |
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| Sparky OR |
| way off topic!!:o |
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| aurche |
| 50W of power over what load you can find(4, 8, 16 ....). 2 channels. Protection for everithing you might do with the amp. The PCB is super complicated, but i have ot on paper, so i can scan it. You don't need any equipment different from a soldering iron. You will need a hefty load of transistors to match them. |
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| pacificblue |
| quote: | Originally posted by Sparky OR
way off topic!!:o |
Exactly! That amp belongs into the thread UGLY Looking Amp! - but good working :smash:
On the other hand it doesn't even seem to fall into the DIY category. |
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| lineup |
| quote: | Originally posted by chylld
PROBLEM SOLVED!!!!!!11
after a whole day's work i am glad to contribute the following solution to gainclone hum.
i can now put my ear literally within ear-hair's distance away from the speaker and i cannot hear ANYTHING. (unless i'm playing music of course!)
http://temp.jw.id.au/gcchibi1.jpg
http://temp.jw.id.au/gcchibi2.jpg
http://temp.jw.id.au/gcchibi3.jpg
i assume the pictures are self-explanatory. the transformer box (i call it "chibi") sits on the floor about 3 feet underneath the amp.
can i just say: transformers suck. |
i can now put my ear literally within ear-hair's distance away from the speaker and
i cannot hear ANYTHING.
(unless i'm playing music of course!)
You can not hear ANYTHING with amplifier on.
Great!
Now, do not ruin this by playing some noisy humming modern stinking rap music :D
transformers suck
well, why do you use them?
At least they have to do some thing right ... or ;)
regars lineup |
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