| cowanrg |
after many many problems:
http://www.diyaudio.com/forums/show...&threadid=61362
http://www.diyaudio.com/forums/show...&threadid=60218
http://www.diyaudio.com/forums/show...&threadid=57946
im finally at the point to where its almost done. it plays music seemingly fine, but its NOISY and there is still turn-on thump. i built and installed a velleman K4700 circuit, but it still thumps on turn on. after the 6 second delay, the light on the kit goes off (as it should), the relays click, and THUMP. i thought that was the whole point, it was supposed to get rid of that. maybe i need a longer delay, but i doubt it.
also, one channel is getting a nice loud hum now (didnt happen before) and the other channel has a quieter hum. both are unacceptable, you can hear it from a few feet away. and when no input is connected, it is very loud.
it sounds like a grounding issue, but i cant seem to track it down. does the velleman kit need special grounding (i just connected it as it said, with the ground connected to the RCA output grounds). thanks guys. |
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| Magura |
Don't you have a star ground you could try to connect it to?
A star ground have solved many a grounding problem for me.
Magura :) |
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| cowanrg |
i dont really have a star ground.
here is how ground is connected...
it comes in from the IEC connector, then it goes straight to a euro-style connecting block, where it connects to chassis ground and out to both of the power supply boards (maybe that is a star ground point). a ground wire goes from here to each power supply board, goes out each board to the main preamp board (along with + and - power).
on the inputs, ground goes from the input jacks to the volume control, then to the main board. on the outputs of the main board, it goes out to the output RCA's.
thats pretty much it... should the input and output RCA's be connected to that star ground as well? i would think that would create a ground loop. |
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| Magura |
Nope, the whole thing to the star ground. There are other solutions that I have little experience with, but all to star ground is 99% proof.
Magura :) |
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| pinkmouse |
| Sounds like you have some dc on the output. That's usually the cause of thumps, especially as it happens when the relay kicks in. |
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| Magura |
a quick solution to tell if DC is the issue is to put a 50 uF cap in series with the output.
Magura :) |
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| cowanrg |
magura,
thanks. so, all RCA input jacks and output jacks straight to a common star ground? so on my board, instead of connecting + and GND, i would just connect the +, and connect the RCA jack's ground to the star ground instead?
i want to make REALLY sure of that because thats like 6 hours of re-wiring...
pinkmouse,
i tried measuring DC on the output and just got like 3-7mv. i watched the meter when it turned on, and it went from 0.1mv or so to about 3mv when the relay clicked on. it wasnt like it shot up really quickly and backed down, it just slowly went up. my meter has a little bar graph thing at the bottom that shows spikes and stuff, and it didnt move.
so, now i just realized that the turn-on thump is random :whazzat: . i went in the shop really quick to see again if i could measure it, and i didnt get it this time. which is REALLY strange. i tried it 3 times. nothing. i made sure the amp was on first and everything. but im still getting a nice buzz which changed volume with the volume knob. |
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| Magura |
| quote: | Originally posted by cowanrg
magura,
thanks. so, all RCA input jacks and output jacks straight to a common star ground? so on my board, instead of connecting + and GND, i would just connect the +, and connect the RCA jack's ground to the star ground instead?
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That's how I usually do it, works fine.
Magura :) |
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| cowanrg |
ok, ill give that a try. im just wondering why one channel is much louder (buzzing) than the other.
and also why i cant seem too measure any of these problems. it measures like its dead quiet. i think it might be my amp that could be causing some of it. im going to bring down on of my rotel amps and test it with that... |
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| cowanrg |
i brought one of my rotel 2-ch amps down to test it out with. its much quieter, but still has the same problems really. still no turn on thump, maybe thats fixed?
the humming/buzzing in one channel is now more of a hissing (like when you turn your volume knob all the way up and it just has that hissing background noise). its still much louder on one channel than the other. |
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| vdi_nenna |
| could it be a bad/leaky zener in the power supply?? |
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| cowanrg |
i dont know, could it be?
there are 32 zeners between the two power supplies...
how would i test this? im getting the right voltage out of the power supples (within like 1%). so, can they be bad and still give me the right voltage? |
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| cowanrg |
is that site in english? :xeye:
it appears as though its explaining how to correct a circuit that has a problem with leaky diodes. however, this circuit has been built hundreds of times. is a leaky diode a bad diode, or just a problem with a circuit design? |
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| Magura |
| quote: | Originally posted by cowanrg
is that site in english? :xeye:
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I just gave it a go with babelfish, it seems a leaky zener is a bad zener.
What brand of zeners are you using?
Personally I am very critical when it comes to zeners. Zeners from Vishay and Onsemi have never let me down so far.
Magura :) |
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| cowanrg |
to tell you the truth, i have had bad zeners before and they have caused me MAJOR headaches (remember the aleph3?). i had a few bad ones in this power supply circuit as well. maybe i should just get all new ones. hell, ive replaced every OTHER part in this thing so far.
from mouser's catalog it seems that the vishay zeners are only about $0.07 each for the 9.1V 1W type.
is this something i should try? id rather not go and buy more parts and waste money is its not a valid problem, or if there is some way to test for it. can i just make an unregulated supply with a bridge and some caps to see if thats the problem? |
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| Magura |
I usually go for the 3W version, can't tell you why, maybe because they can be used anywhere, I simply bought a good stock of the 9.1V 3W zeners.
I would replace those zeners ASAP, simply to exclude them from the equation.
You can't just make an unregulated supply, as your trafos will give you more than 80V unregulated.
Magura :) |
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| GRollins |
I scanned the thread quickly and may have missed where someone tackled the thump problem.
Is it safe to assume that you are using the turn-on relay to interrupt the output?
If so, that is likely the problem.
When the circuit is turned on, the outputs jump to a positive DC voltage. What happens when you put a pulse (an AC signal) into a cap? It causes a charge to appear on the other side of the cap. This is normal. This is good. This is what you want a cap to do. If it didn't work this way, then the music wouldn't get through the cap and all would be for naught.
But that's also the problem. Now you've got a charge on the output side of the DC blocking cap. Two things can happen. One--it can sit there until doomsday or until the real-world imperfections of the cap allow it to leak away. Or--Two--it can discharge to ground.
Fair enough. There's a resistor at the output that will allow this DC charge to dissipate. (You did install that resistor, didn't you?)
Now, here's the deal...you can either allow that resistor (100k?) enough time to discharge the DC blocking cap down to ground--or--you can kinda help those electrons find their way home by shorting the output to ground (not open) for those first few seconds while the preamp is powering up. This will do an excellent job of removing that thump-inducing DC charge. Once it's gone, it will not come back.
"But, Grey, won't that blow up the preamp? After all, you're shorting the output to ground. My buddy George did that with his amp and it..."
The short (ahem) answer is no. It won't hurt anything.
The somewhat longer answer is that the MOSFETs are not going to exceed their ratings and that the DC component isn't going anywhere anyway because it's being held back by the salf-same cap that's causing you annoyance in the first place. The AC part of the signal can take care of itself. The preamp will be fine.
The noise(s) could be any number of things. Bad solder joint. Wiring harness in the wrong place. Wrong value resistor in the wrong place. Etc. etc. etc. Right off the top of my head, I find it unlikely that it's anything to do with the power supply. One, the audio portion of the circuit is a differential. Differentials have, to greater or lesser degrees, something called Common Mode Rejection Ratio (CMRR). This means that a signal that appears on both sides of a differential is ignored. Yes, this applies to noise on the rail, too. Now, the BOSOZ doesn't exactly have the greatest CMRR in the world, but it tends to weigh against rail noise. Another argument is that hiss, per se, is just not something that you see coming off of your rail. Why? Because hiss, in the sense that most people mean, is a higher frequency sound. By definition, high frequencies are shunted to ground by the power supply caps. Hum, yes. Hiss, no.
Hiss, in this context, suggests oscillation. Check your Gate stopper resistors (those 221 ohm resistors that Nelson puts in front of the MOSFET Gates).
Buzzes and hums can be caused by scads of different things. Not enough capacitance in the power supply. This includes caps that you think are there, but aren't really, meaning bad solder joints or screws that aren't tightened properly. Ground problems. Ground loops...if you're using a three-prong AC plug, use a "cheater" plug to lift ground, not only for the preamp, but also try the amp, source, and anything else in your system. If the hum stops, you've got a ground loop. Curing ground loops can be annoying and frequently involves large quantities of alcohol and cursing. Persistence is the key.
Good luck.
Grey |
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| cowanrg |
oh yeah, forgot i would get +-80v.
ok, ill replace the zeners. i was hoping to get this done today (well, months ago actually), because im visiting my partents this week, so i could bring it with me if it was fixed and working. i guess ill just have to wait. |
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| cowanrg |
Grey,
great post, thanks. in response to the thump question, yes i am using a relay to interrupt the output. its the velleman k4700 kit. i understand you completely though. but should the kit correct this problem? could i maybe wire it up to short to ground before the relay kicks in?
i will check my solder joints again. they should be fine. my hakko and the WBT solder are a match made in heaven. but ill check it all anyways.
as far as the noise issues you bring up, a few could be possibilities. not enough capacitance (aside from bad solder joints) isnt likely. oscillation is most likely the problem, although i dont know why. also, i had mentioned before that im getting significantly louder humming on the left channel than the right. im not sure why this is.
ok, i did a little checking. since i posted this thread, i have yet to hear that thump again. i think it was happening before i re-grounded the relay circuit, so that may have cured the thump.
however, the noise is still there, and its best described as just noise. its not really a hum or a buzz, but just background hiss. like on a poorly mastered cd, you heard this noise in the back. it happens with or without a source plugged in.
at full volume, it does hum, like a ground hum. its inaudible at lower volumes, but from about half to full volume it becomes apparent, and very loud. i lifted the ground on the amp, preamp, and cd player. none had earth grounds, just grounds through the interconnects. nothing changed at all, i still got the same noise and hum. so i guess its NOT a ground loop.
i did some more general messing around and found more wierd things. with a cd player plugged into the inputs, there was LESS humming. when i unplugged the jacks, the humming increased. this was whether or not the player was on or playing. even off and sitting there, having the player plugged in made it quieter. as soon as i unplugged them, the noise was much higher.
if i unplugged the cd player, but left the cables attached, there was no differene in noise. there wasnt a change in noise level when i plugged and unplugged them into various inputs. but as soon as the other ends were plugged into the cd player, plugging and unplugging them was like making music with noise...
i disconnected the velleman thingie and the noise floor was much higher and there was a MUCH more apparent hum at lower volumes than before. that is just confusing and i wont say more about that...
i think i might buy a rotel preamp from work at cost and toss the guts into the case and call it a day :dodgy: |
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| cowanrg |
i think i might spend several hours on this tomorrow. here is the list of things im going to try:
1.) remove ALL grounds and create a star ground.
2.) remove all RCA jacks and have temporary input/output jacks to correct any grounding issues
3.) temporarily get rid of all input switching and volume control (i have a cd player with volume control)
4.) recheck all solder joints
5.) recheck resistor values
anything i missed? |
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| Cobra2 |
Picture?
You could also try twisting the trafo, 0-90º, sometimes it makes a difference! (even with toroids).
Arne K |
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| mark stones |
| quote: | Originally posted by cowanrg
Grey,
great post, thanks. in response to the thump question, yes i am using a relay to interrupt the output. its the velleman k4700 kit. i understand you completely though. but should the kit correct this problem? could i maybe wire it up to short to ground before the relay kicks in? |
Consider for a moment what grey wrote re:
or--you can kinda help those electrons find their way home by shorting the output to ground (not open) for those first few seconds while the preamp is powering up. This will do an excellent job of removing that thump-inducing DC charge. Once it's gone, it will not come back. "But, Grey, won't that blow up the preamp? After all, you're shorting the output to ground. My buddy George did that with his amp and it..."
The short (ahem) answer is no. It won't hurt anything.
If my understanding is correct the velleman kit is currently wired in series with the output (it disconnects the output for X amount of time) if you are going to strip the unit back to basics once you have your "other" problems solved if you still feel the need to use the velleman kit seriously consider using it to short the output to ground for x amount of time rather than disconnect the output this will not only yield the benefits that gray explained but will also mean that the velleman relay is not in the signal path.
for what its worth your strip it down to minimum requirements to assist fault finding gets my thumbs up as it removes some potential problems from the equation.
Best of luck, Mark |
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| cowanrg |
| quote: | Originally posted by Cobra2
Picture?
You could also try twisting the trafo, 0-90º, sometimes it makes a difference! (even with toroids).
Arne K |
if you follow some of the threads i posted, you can see some pics. here is a link:
http://www.diyaudio.com/forums/show...2241#post662241 |
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| cowanrg |
| quote: | Originally posted by mark stones
Consider for a moment what grey wrote re:
or--you can kinda help those electrons find their way home by shorting the output to ground (not open) for those first few seconds while the preamp is powering up. This will do an excellent job of removing that thump-inducing DC charge. Once it's gone, it will not come back. "But, Grey, won't that blow up the preamp? After all, you're shorting the output to ground. My buddy George did that with his amp and it..."
The short (ahem) answer is no. It won't hurt anything.
If my understanding is correct the velleman kit is currently wired in series with the output (it disconnects the output for X amount of time) if you are going to strip the unit back to basics once you have your "other" problems solved if you still feel the need to use the velleman kit seriously consider using it to short the output to ground for x amount of time rather than disconnect the output this will not only yield the benefits that gray explained but will also mean that the velleman relay is not in the signal path.
for what its worth your strip it down to minimum requirements to assist fault finding gets my thumbs up as it removes some potential problems from the equation.
Best of luck, Mark |
i think i might rewire the velleman kit... its just a preamp, so how much DC can really be on its output? so i might as well just use it as a short to ground at startup, not a full protection circuit...
BUT, i will try to bring it back down to basics as soon as i can. i had a slight "delay". i got my new toys in that ive been waiting on for 6 months. im gonna play with those all day, then i work tomorrow, then im out of town for vacation. it might have to wait. maybe that will give me some time to step back and rethink things.
(dual velodyne DD-18's in cherry)
http://www.cowanrg.mesanetworks.net...ages/subs_2.jpg
(mmmm, pretty)
http://www.cowanrg.mesanetworks.net...ages/subs_4.jpg
(gotta love full parametric EQ and room correction from a sub)
http://www.cowanrg.mesanetworks.net...ages/subs_6.jpg |
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| SvErD |
Hi, first of all I would really recommend you to get rid of that enormous trafo. 800 VA in a preamp is way beyond overkill. It must put up a huge hum-field.
If you must use it you could improve a couple of things IMO:
1. Rotate the trafo 180 deg to get all AC wiring towards the front of the amp, now you have ac and dc wires close together.
2. Shield the input power leads and rout them along the left side of the amp all the way to the front and then along the front to the trafo.
3. Twist or braid your DC wires between the PSU boards and amp board.
cheers |
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| fcel |
Cowang,
In your other thread, I did add a big reminder to let you know that I have wired my Vellerman kit not according to what the manual says. I have mentioned that I have wired it in such a way that before turn-on and during turn-on, the output is short to ground and after a couple of seconds, the relay opens and the signal is outputed to the speakers. |
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| grataku |
I think it's time for you to throw this whole thing in the toilet and flush. It seems to be getting you to a place you don't wanna be. ;)
Not to mention these incessant new threads about problems with the world most succesfully built preamp may start to get Nelson aggravated. :cool:
I have a lot of experience with the circuit. I built the boz and made it X added ccs and never-ever-ever had any problems with hums, startup thumps or blownup parts or anything (working super well as with any other circuit designed by 'The Zen Masta' ). Vellman kit is not needed here so you might as well save your money. |
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| cowanrg |
SvErD,
you cant really tell from some of those pics, but there is a half-round piece of steel around the transformer as well as the piece of steel that separates the PSU section from the preamp section. i guess thats not enough?
ill try temporarily re-routing cables to see if it makes a difference.
fcel,
i do remember that. you werent using the DC protect features of the circuit, just the turn on relays.
grataku,
that doesnt help me out a whole lot. as you can probably see, ive spent a LOT of time and money making this, and im not about to just abandon the project.
sorry about the multiple threads, but new problems just keep popping up. its obviously not a design flaw on nelson's part. i just cant understand how i could mess it up SO much. i mean, looking through the passdiy gallery, there seem to be a LOT of these that are just thrown in a box and wired up like somoene was on crack. maybe they dont sound very good, but ive not seen very many people have problems with theirs.
and actually, i thought that some kind of circuit was needed to stop turn on and turn off thump. i remember reading that in the article. plus, many people on this forum see to have had problems with it as well. im not the only one there.
do you have any pictures of your perfect unit? maybe some constructive advice then? im willing to give anything a try at this point. i understand the concerns with some of the wiring and transformer, but i dont see how that can make it do what its doing. maybe an incredible amount of noise could cause it to oscillate, but i didnt think that was possible. |
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| jh6you |
I think things are mixed up here.
I understand there are two problems: hum and turn-on-off thump noise. In my opinion, solution to the turn-on-off thump noise is considered “nice-to-have.” Probably, it might be a kind of aesthetic desire. Meanwhile, solution to the hum and buzz is considered “necessary.” Therefore, I would put the first effort on the solution to the hum and buzz. After that, if I have any good opportunity, I would try to fix the turn-on-off thump matter.
I think, before we complain any circuit name or its designer, we need to ask a question to ourselves first—ie whether I understand the basic grounding principle or not. As far as I understand, the most hum and buzz happens mainly because we ignore the basic grounding principle. There could be other reasons, but in general at very low probability level or at minor magnitude.
I would do the followings: Make one star ground where located away from the PSU. From the star ground, send pair of any AWG wires having the same length separately to the center of input RCA complex, separately to the output RCA, separately to the volume unit, separately to the circuit grounds, and separately to the PSU. And re-check whether such wire arrangement is forming symmetry about the star ground to the left and right channel.
This method might result in an ugly look wiring. But, it doesn’t matter as long as there is no hum and buzz. It doesn’t matter as long as safety hazard free is still valid, and it doesn’t matter because the amp top cover hides it. Now, there is no hum and buzz. But, if the ugly look wiring is somewhat concern, then we could go back, rearrange and minimize number of wires, carefully monitoring any potential hum or buzz.
If we are focusing too much on the neat and beautiful wire arrangement from the beginning, we easily overlook the basic grounding principle. I know this based on my poor experience.
Drinking a cup of coffee . . .
And, hoping this info will help . . .
Good luck!
Regards
jH |
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| grataku |
Cowangr,
obviously it must be something that you are so blinded by the months and the times you've looked at the pcb that you can't see.
Other sending me the boards for inspection I don't know what to suggest besides starting over.
I am espacially concerned about your grounding. In your description of the path to ground I haven't heard the word 'thermistor' anywhere. You should have a second look at some of the recent schematics that nelson published, he is being consistently showing the same gnd scheme.
I agree with one of the earlier posts about the trafo. Try moving that 3ft away during testing.
Someone with a fresh pair of eyes should have a look. Don't you have a friend with the same hobby that can help? |
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| cowanrg |
ok. so i was on vacation for awhile, school just started back up, i started my own business (now self employed) and a few other things have delayed me even going down into my shop for awhile.
jh6you,
thanks for the words of encouragement. i have taken your advice (although not original to you alone)
grataku,
thank you as well. the grounding was adequate, but maybe not the best. the thermistors are built into the PSU boards im using. i have one for each channel for each ground.
here is what i have done recently. i took the entire thing apart, into pieces. i wired up just what was necessary to run the preamp. i completely cleared my workbench and hooked up the most basic version of the circuit. i had a power inlet to transformer, out to a single power supply board, to the preamp. the preamp has NO input RCA's, just a single mono RCA output (just doing one channel for now). ground of rca is connected to star ground, as well as earth ground from inlet, ground from psu board and ground from preamp board.
i arranged it on my workbench so that the transformer is about 2 feet from the preamp board, the psu board is 1.5 feet from both the preamp and transformer. and, the conclusion? i still get a hum/buzz. its more like the hissing i was describing before. its just not very quiet at all. 1-2 feet away from the speakers you can definately hear them. its a hissing kinda like a background noise that is relatively common, but its much louder, and there is a buzz in the background too. this is with NO input at all, and nothing else connected other that what i described above. so, its definately a problem with the circuit.
i hope this helps some people to get some ideas as to what is really going wrong. i checked all my solder joints on the preamp and PSU boards. i even swapped to the other PSU board with same exact results. all solder joints look great. it might be a tad quieter than when it was all crammed inside the case, but its marginal (and its been a month since i heard it last). and it still buzzes pretty loud as soon as it comes on and slowly quietes down, but never goes away.
bad zeners, bad fets, bad builder? |
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| Tom2 |
cowanrg,
I looked at your bosoz web page and you seem to sharing the secondaries with both power supplies using Kirstijans boards.
I think that would lead to weird ground and power supply problems.
I would think you need four seperate secondary windings or two separate power transformers each with two separate secondaries.
I know someone asked this before but, is the common heatsink for four mosfets of the gain stage electrically isolated? In other words are the drains not shorting out?
Just trying to help. I've been there also.
Tom |
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| Magura |
This could be a bad transformer as well, I have seen that before. In your case I would go and get 2 <120VA trafos and see what happens, such small trafos are cheap after all.
Magura :) |
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| butler853 |
cowanrg,
I was wondering if you are making sure to bleed the power supply caps every time before connecting/unconnecting the power supply board to the preamp board. I am building an aleph P1.7 using Kristijan's boards. After testing it the first time, I disconnected the power supply without draining the caps, and fried the 3.3 ohm resistor at V+ on the preamp. Maybe the 6.8 ohm resistors at V+ and V- got fried on your preamp boards? I dont know if that would cause the problems you are having with it though. The only other thing I might suggest is try to disconnect the earth ground from star ground and see if that reduces the hum. |
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| grataku |
Hi,
if all you have stated is true then the only thing that comes to mind is badly routed grounds on the PCB maybe the ground of the bypass caps runs together with the signal ground inducing the buzz or hiss.
I used Nelson's PCB and never heard hissing. |
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| cowanrg |
Tom2,
i am sharing secondaries with both left and right channel boards. however, when i did the test, i was only testing one channel, so the entire setup was acting like a mono configuration. and it still had the hum/buzz/hiss to it.
The heatsinks is electrically isolated. im using some mica pad thing, and even nylon screws just in case.
Magura,
i got your email as well, thanks. i checked on that transformer, and it was like $40 when bought in the US. it was only like $9 in the UK, but their US distributor is much higher. ill have to look elsewhere.
butler853,
ill have to check those resistors to see. usually i DO let it bleed before i disconnect and reconnect things, but ive been messing with this so much that it could have slipped.
i have tried lifting the earth ground and it gets worse if i rememeber. but i havent tried it with the "minimal" configuration.
grataku,
i have heard of MANY people building this preamp with kristijan's boards with much success. he has built it as well, and everyone seems to think it was dead quiet.
so, i guess it has come down to the transformer. Magura had a good explaination of how the larger transformer could have been inducing the noise im hearing. it seems valid enough. at this point, im willing to try anything.
i cant seem to fine a cheap transformer suitable for this project. nelson suggests 2 avel lindbergs per channel, the 30VA 30+30 ones, but i would have to call avel to get a price. they seem to be around $25 each though, which is $100 for all 4. i would hate to spend that money just to "test" a theory.
would a 55+55 work for one channel? avel makes a 80VA thats 55+55 that might work. |
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| Magura |
| quote: | Originally posted by cowanrg
would a 55+55 work for one channel? avel makes a 80VA thats 55+55 that might work. |
Yes, that is what most of us have used as far as I know, myself included (I used a 120VA 2*55V). I had my version of the BOSOZ out for a test spin a couple of days ago, the trafo's I gave you the number of are the ones I'm using. The test was performed with a birdsnest and bad grounding tech. and it still was dead quiet. I even ran it off a 75VDC unregulated supply. I am now contemplating if I should make the supply regulated, but I guess I will.
Magura :) |
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| Raoul |
| quote: | | would a 55+55 work for one channel? |
I built my BOSOZ with a couple of Apex Jr. Avel surplus transformers. The secondaries are 28.4V + 28.4V, 150VA. I adjusted the zener stack in the P/S to compensate for the lower voltage. They cost $22.00 a piece, but I think Steve posted a special offer for diyAudio members somewhere on the forum.
http://apexjr.com/miscellaneous.html
edit: Found the link to Apex Steve's special offer
http://www.diyaudio.com/forums/show...9625#post609625
It's kind of old, so you might need to check and see if it's still valid. |
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| Magura |
According to my experience the BOSOZ runs off pretty much anything between 25 and 80V, it supposedly sounds better with lower distortion around 50VDC and up, but I have not been able to hear any difference.
Magura :) |
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| cowanrg |
do you think having an 80VA per channel would be a good idea? it looks like two of those would fit perfect in the case as is. and price-wise it would be decent as well.
i just hope thats the problem! |
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| Magura |
80VA is plenty. I have seen people run it off 25VA trafos.
Magura :) |
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| cowanrg |
so, im re-opening this thread!
im tired of the preamp just sitting there collecting dust. i ordered a 1.7 kit from a guy on here, but after 2 months, he has yet to ship it, and still have my money. im still working it all out, he claims it was lost in the mail, but still, it sounds fishy.
anyways, i want this thing fixed and working. i have a scope now! im not entirely sure how to use it, but im pretty sure it works, and i have test leads.
i hooked it up to the wall outlet and looked at the AC voltage coming in from the wall. it looked like a nice sine wave, with just a tiny bit of distortion at the peaks. i went step by step hooking up the preamp. i started with just the transformer, and looked at it through the scope. it looked pretty much the same, nice and smooth lines.
then i hooked up the power supply board. i got +-59v, a little low, but fine. however, i tried to stick the scope probe on it, but all i got was a solid line, no matter how many knobs and dials i messed with. so obviously im doing something wrong there. or maybe it is supposed to look like that. but it was always pretty much perfect.
i hooked up the preamp circuit and measured it all, the voltages are perfect. i put the scope on the output, and same story, straight line. it kicks up and down when the amp turns on an off, but other than that, it looks the same as if the probe wasnt even plugged in...
ill try hooking up a source and see what it sounds like. maybe staying away from it for so long has made it work finally. haha, yeah right.
so, can someone tell me how i can use the scope to diagnose this problem? |
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| cowanrg |
an update:
i threw on an RCA connector for the output on the preamp board and plugged it into an amp i have in my shop that i use for testing. i hooked the scope up to the outputs on the amp. after fiddling with a lot of settings, i got a something that was interesting.
with the preamp off, the scope just shows a pretty much perfect straight flat line. with the preamp on, it goes a little nuts on startup (i get a buzzing at startup through the speakers, so the scope shows this), and then it shows a line that is "decent", but has some bumps in it and is a bit fuzzy or looks kinda like static. its not a perfect line anymore. and when i kick the preamp off again, or unplug it, the line jumps around a bit (turn off thump), and then stabilized to an almost perfect line again.
SO, im seeing whats going on. what can i do from here to troubleshoot? ive checked and rechecked all my components for the most part. i THINK all the components are fine. ive replaced ALL fets twice or more. where should i go from here? |
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| lgreen |
| quote: | Originally posted by cowanrg
an update:
i threw on an RCA connector for the output on the preamp board and plugged it into an amp i have in my shop that i use for testing. i hooked the scope up to the outputs on the amp. after fiddling with a lot of settings, i got a something that was interesting.
with the preamp off, the scope just shows a pretty much perfect straight flat line. with the preamp on, it goes a little nuts on startup (i get a buzzing at startup through the speakers, so the scope shows this), and then it shows a line that is "decent", but has some bumps in it and is a bit fuzzy or looks kinda like static. its not a perfect line anymore. and when i kick the preamp off again, or unplug it, the line jumps around a bit (turn off thump), and then stabilized to an almost perfect line again.
SO, im seeing whats going on. what can i do from here to troubleshoot? ive checked and rechecked all my components for the most part. i THINK all the components are fine. ive replaced ALL fets twice or more. where should i go from here? |
1. If your bosoz is making 60hz humming noise, you should be able to see it on the scope, turn your timebase down to 60hz, which is about 1/60= 16.6ms/div, so use 20 or 10ms/div. Your trace will slow down, as it goes across the screen.
then turn your v/div on the input amps up till you see the hum as a pattern of waves or partial waves on the screen.
2. turning up the v/div on the input amps will show you all the noise that is there, the straight line will not be so straight after all once you start cranking the amp. However, you have to play with the timebase to learn where the noise is in frequency as HF and LF noise cannot be seen on the low/fast speed (ns) settings.
3. If you want to see AC make sure you select "AC couple" the waveform will not shift position if there is DC on it. this is good to look at the noise on your 60V rails, for example. You may want to see if noise is coming in from your power rails, check them out, if they have bumps then your MOSFETs are probably working right, your power supply might be bleeding the AC to the circuit.
4. You might want to look at the output and rails/input simultaneously on the screen to see if the bumps are happenning at the same time or not in the ps and amp circ.
did this help? |
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| sklimek |
| quote: | Originally posted by cowanrg
so, im re-opening this thread!
i have a scope now! im not entirely sure how to use it, but im pretty sure it works, and i have test leads.
so, can someone tell me how i can use the scope to diagnose this problem? |
Hi cowanrg, I too hope to get a scope soon, in the meantime I have been reading/studying on which ones to get on Ebay. I found a great tutorial from Tektronics on oscilloscopes that may be helpful.
http://www.tek.com/Measurement/cgi-...t=oscilloscopes
Stan |
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| cowanrg |
thanks for the help guys. unfortunately, i cannot see ANYTHING connected just to the preamp itself. it always shows a straight line, no matter how many knobs and dials i turn. this is also true for my meter, the meter registers almost no voltage out on the preamp. in theory, its quite.
however, here is what i see when hooking it up to an amplifier:
(no making fun of my scope) |
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| cowanrg |
this is with no input into the preamp at all. the phoenix connectors are completely empty. the outputs just a single rca going from + and GND to an RCA jack. then, an interconnect connects that RCA to the amplifier. i put the probe at the positive output of the amp's speaker terminal. i could of course be picking up noise from the amp itself, but without the preamp connected, there is just a straight line. so, the preamp is introducing it.
it SEEMS like its a ground loop issue, but ive tried everything. ive lifted grounds, ive shorted inputs, etc... it never goes away. and the preamp board is almost 2 feet away from the transformer, etc... this is a perfect test condition. and the power supply appears to be pretty clean.
the settings i used are: 1ms/cm, .05 v/cm, AC input.
i hope that tells someone SOMETHING. i just found a very small plitron transformer at a surplus shop. its rated at 30 watts and has 55v secondaries i believe. im going to make a small power supply using that, a couple bridge rectifiers, and some caps. i will get rid of the regulated supply and xformer, as they might be the issue. ill see if i still have noise then. |
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| cowanrg |
well, well, well.
i finally used a completely different power supply and the results are interesting. previously, i used the transformer that was in the original build and removed the PSU boards and just made a simple linear unregulated supply. i had the same results as with the regulated PSU boards.
well, it was said that it could be the transformer causing the issues because it was so oversized. i used this little 30 watter i got to test that theory. in the writeup for the bosoz, nelson says that you can use 30-60v rails, but at 60v, you get lowest distortion. this transformer gave me 30v rails loaded. i just used a single bridge rectifier and a pair of smaller value caps. nothing fancy at all.
the exact same noise was still there, but now it was louder. that was probably due to the lower voltage supply, and noisier supply. here is what it looked like (is that what oscillation looks like?): |
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| cowanrg |
| different timebase: |
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| poobah |
cowanrq,
What type of solder are you using and how have you washed your boards? |
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| cowanrg |
| quote: | Originally posted by poobah
cowanrq,
What type of solder are you using and how have you washed your boards? |
hey there poobah!
im using WBT silver solder. i havent washed my boards. is this the problem?
:xeye: |
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| poobah |
cowanrq,
Well I don't know exactly what "WBT" means. If it means "water-based-something" then yeah... you need to wash these boards.
Lemme 'spain Rucy... Good ole Kester 44 and most other solders use a pine tar/oil based flux... it smells like pine when you use it. This stuff is non-conductive and can be left on the circuits forever without any harm (at least that is what we know after 100 years or so)
OTOH, water based fluxes are very conductive; so it's like having a bunch of 200K resistors connecting every point in your amp to every other point. Better still, it is mildly corrosive; so it eats away at your connections if left on the boards.
This is just a wild guess... but it sounds like that is where your at.
Go to their website... and post the link for us... give us the brand, part number and all that for the solder your using.
If you're just starting out building electronics... try to stay away from exotics... in just about anything. I am all about gold plated connectors simply because they don't rot; but I won't pay alot for them (10 cents worth of gold). Beyond that, the only people who can hear a difference are the people that actually spent a pile of money on something questionable.
Let us know about your solder... and we'll line you how on how to clean your boards... IF you need to.
;) |
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| cowanrg |
ok, here is the exact solder i used for the preamp and PSU boards:
http://www.wbtusa.com/wbtsilversolder.htm
ive used it for two working aleph3 monoblocks, a 2-ch gainclone, some stepper motor controller boards, and several other things.
i also have some backup solder that i use, which is kester "44" rosin core. the label is worn off, so i cant tell much more than that.
i have a VERY hard time believing that is the cause. BUT, its not the power supply, or the power supply boards, and both channels of the preamp are doing the same thing, so maybe it is... |
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| poobah |
OK,
For openers, WBT doesn't have a "spec sheet" on their product, the solder. In my book, that makes it a "non product" right out of the gate... looked like some audiophile cr4p there too. I would stay away, save your money, and deal with professional product. I don't know if your boards should be washed or not... you might send them an email and find out. I do agree, with the other amps working that flux is probably NOT the problem. Never hurts to clean your boards though... problem IS, don't know what to clean with... no specs. They are buying this from some one else... slapping on their label... charging 4 times more for it... and concealing the specs so other people won't match specs and find out it is just Kester, or the normal German brand solder being relabeled. Try to stay away from products and websites that don't have specs... not professional grade... you want tuna that tastes good.
I read back through the thread again. You changed power supplies and still the same problem. But your waveforms imply a hum problem.
The most telling thing in the whole thread was the fact that you could alter the input connections and change the noise problem. Ah-ha????
Can you post a schematic or link. I don't follow all threads and "fashions" etc...
:D |
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| wuffwaff |
Hi,
WBT is a German brand wich also makes all sorts of cinch and loudspeaker connectors. I´ve used their solder quite often without any problems (it smells very nice:) )
Since both of your boards do the same thing the mistake must be one that is constructed in and not a faulty part.
Since the schematic is very simple you could check the boards point to point if they comply with the schematics.
William |
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| cowanrg |
plenty of people on here use the WBT solder, its pretty popular. i got it off a recommendation about 2 years before poobah became a member! hehe. i didnt get it for sonics, etc.. i got it because its really easy to work with and melts at a low temerature. it isnt that expensive if you know where to buy it, and it truly solders a LOT better than the kester i use otherwise.
ive built to many things with it to think that its the solder thats causing the problem.
here is the schematic again:
http://www.kk-pcb.com/bls.html
the board and schematic are there.
here is a link to the full writeup from nelson pass. he includes a service manual that has voltages to check. im getting almost exact values at the spots. the schematic is on page 4. im getting within 1% or so of all the values given.
http://www.passdiy.com/pdf/balzenpre.pdf
this is why its so confusing to me!!!
poobah, you said this:
"The most telling thing in the whole thread was the fact that you could alter the input connections and change the noise problem. Ah-ha????"
where did you see that? all the noise you are seeing on this post is without a single thing connected at the input. i will try shorting the input to see if it changes things (ive done it before, but not with a scope). could you maybe show me the post where i said this? there are about 3 threads with 10+ pages of posts of this problem alone :bigeyes:
ive been trying to fix it for about a year now. |
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| poobah |
Well, enough about the solder. BTW, I was designing amps before the web existed... excuse the 2 months on DYI please.
Geeze there is nothing to this thing! Shouldn't be that hard.
Rig up 2 connectors for the input (cheap ones) just make a short circuit... "tip to ring". Short the inputs, read the outputs and listen... tell us what you get.
:D |
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| cowanrg |
| quote: | Originally posted by poobah
Well, enough about the solder. BTW, I was designing amps before the web existed... excuse the 2 months on DYI please.
Geeze there is nothing to this thing! Shouldn't be that hard.
Rig up 2 connectors for the input (cheap ones) just make a short circuit... "tip to ring". Short the inputs, read the outputs and listen... tell us what you get.
:D |
thats exactly what i was going to try.
oh, and i wasnt at ALL trying to call you a newbie. just to show that many people on here use WBT solder, and its popular, and im sure its not the problem. thats all. you know more than me at this, yet you've only been registered here for a few months, me, a few years. it doesnt relate in any way to knowledge. |
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| poobah |
Relax...
What is your input cabling like... and what are you (or wish to) driving it with? What are you using for input connectors?
This is a balance input... so Don't connect your inputs to ground... connect the plus to the minus with NO connection to ground... yet. |
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| cowanrg |
| quote: | Originally posted by poobah
Relax...
What is your input cabling like... and what are you (or wish to) driving it with? What are you using for input connectors?
This is a balance input... so Don't connect your inputs to ground... connect the plus to the minus with NO connection to ground... yet. |
well, the input cabling hasnt been on there in about a year. back when i actually had it all together and "working", i was using synergistic research alpha sterling. sure, its an audiophile cable, but its just a basic 22ga (or thereabouts) silver-plated copper stranded wire. its non-shielded. it terminates nicely, thats all.
right now, there is nothing where the input connectors are. i just have phoenix connectors and thats it. no rca jack, nothing.
it WAS being driven by multiple things. i used musical fidelity cd players, denon cd/dvd players, etc. i tested it with numerous players all with the same results.
the buzz/hum is created without an input connected.
i just tried shorting the input. i just took a wire and put it from + in to GND IN. it was a bit quieter, but still noisy. the scope didnt read a bump like it did before, but the whole line was really jumpy and noisy. it just looked like static.
for what its worth, when i had JUST the + IN connected, and left the other end hanging, noise was about 10-20 times louder, and noticeable from 10+ ft away. without anything at all in the input, it was louder than with the input shorted...
edit:
i just saw what you wrote about not connecting input to ground, but connecting + IN to - IN. i will try that now and see what happens. i had - IN and GND IN shorted because im using single-ended. |
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| cowanrg |
i replaced the jumper at the - and GND on the input and replaced it so ground was left untouched and - and + IN were connected. it sounds the same as when - and GND are shorted, and + and GND are shorted. there isnt a difference in noise level.
for grins, i shorted - and GND, and pluged an RCA into + and GND. i hooked up my test cd player i have in my shop (it has a volume control on it) and played a cd. wow, noisy noisy noisy. its even louder with the cd player plugged into it. |
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| pinkmouse |
| This may be an obvious question, and you've tried at already, but have you tried feeding a sine wave into your 'scope from a signal generator or PC app. to see if that's working correctly? |
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| cowanrg |
| quote: | Originally posted by pinkmouse
This may be an obvious question, and you've tried at already, but have you tried feeding a sine wave into your 'scope from a signal generator or PC app. to see if that's working correctly? |
not an obvious question. i was wondering that myself. im very new to scopes, this is the first ive EVER used, and ive only had it for a month or so. and its OLD.
but, the fact remains, the preamp is doing something very funny. my scope appears to have a signal generator of some kind. is that useful, or do i need an outside source? i also have test cds (not MP3's) with signals on them, could i use that? or would i just be testing my cd player... |
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| serengetiplains |
| I wonder if your amp isn't suffering from impaired differential psu noise cancellation? |
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| cowanrg |
| quote: | Originally posted by serengetiplains
I wonder if your amp isn't suffering from impaired differential psu noise cancellation? |
what the heck is that? :xeye: |
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| poobah |
Hey cowanrq,
Check your email.
:D |
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| cowanrg |
| quote: | Originally posted by poobah
Hey cowanrq,
Check your email.
:D |
hm, no email. maybe you meant "mail" and have sent me brand new working boards in the mail? hehe. |
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| pinkmouse |
| quote: | Originally posted by cowanrg
not an obvious question. i was wondering that myself. im very new to scopes, this is the first ive EVER used, and ive only had it for a month or so. and its OLD. |
Can't be much older than mine!
| quote: | | I also have test cds (not MP3's) with signals on them, could i use that? or would i just be testing my cd player... |
Well, if you use the cdplayer to pump signals into the scope at a certain frequency, say 1K, you can get it set up so that it shows something useful, and once that's done it will be much easier to use to find problems in your circuit. |
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| serengetiplains |
| quote: | Originally posted by cowanrg
what the heck is that? :xeye: |
Hi Cowan, the bosoz circuit operates differentially. One beneficial element of differential operation is that noise appearing on the power supply rail will be fed to both + and - legs of the circuit, and to the extent everything is equal on those legs (equal amplification per frequency, equal resistances, equal capacitances) will that noise be cancelled, including as amplified by the fets, on the output (think of combining two sine waves of same magnitude with 180 degrees phase difference between them). Any imbalance (inequality, if you will) in the operation of + and - legs will allow noise, to the extent of that imbalance, to pass into the output. With both hiss and hum, I would suspect a faulty fet, but you say you've replaced the fets. I wonder if you have a faulty resistor on either the + or - leg? With the amp idling, check voltage drop across all resistors. A faulty resistor could be a source of hiss and could allow one channel to amplify psu hum more than the other. |
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| poobah |
Check again,
I just sent it... |
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| cowanrg |
ok, more testing.
i found this out, which could be the issue. my coupling caps, the 10uf guys are only rated to 50v! i dont know why i have those in there, but i do. and they are non polar electrolytic black gates. i think they were a suggestion of peter daniel back when i listened to him :)
anyways, could they be causing some issues? i measured all the resistors after them in the circuit, and none are getting any voltage. they all just measure 0v at both ends.
i have some 3.3uf wima's laying around. can i pop those in to test them in the circuit? is the value ultra-critical? |
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| poobah |
Hey Cowanrq
When the circuit is idle (no input) all resistors except for R16, R17 & the 750 Ohm's should have zero volts across them.
:D |
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| poobah |
| Does your meter measure inductance (L)? |
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| cowanrg |
| well, i replaced them with the WIMA's, and you were right, they werent the problem. i still got the nasty nasty noise on startup, and the hum when it was running. |
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| cowanrg |
| quote: | Originally posted by poobah
Does your meter measure inductance (L)? |
nope, just the usuals, capacitance, and diode tester. |
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| BDP |
If you have +/- 60 volt rails each drain should see about 30 volts.
The source resistors should see the Vgs drop minus the neg. rail voltage. Example: -60 volts - 4 Vgs = -56 volts.
-56 volts / 750+750 source resistors = ~37mA.
37mA flowing through the mosfet and through the 750 ohm drain resistor = 37mA x 750 = ~28 volts. 28 volts minus the pos. 60 volt rail voltage = 32 volts. This would be the voltage measured between the drain and ground. The gates of the mosfets need to be referenced to ground. This is accomplished through R13,14 or an input pot. if used.
If you continue to have problems and the pain gets to great, you could ship it to me for repair. You pay only shipping.
It is a very simple circuit and you must be overlooking the problem.
BDP |
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| cowanrg |
believe it or not, im getting almost EXACTLY those values. ive measured them all.
im getting 29.9v at the drain, 4.006 at the source. and the 750ohm resistors are 57 and 26 or so respectively. everything adds up, but im getting nasty noise on turn on, and noise when its on and inputs shorted...
ive tried different power cords, interconnects, wiring (multiple times), amp, source, etc. every single thing has been swapped. all fets have been replaced twice. 3 different power supplies, with 3 different transformers at different voltages.
poobah seems to think it might be the inductance of the 750ohm resistors. i hope he's right. its not like i have a bad fet, everything measures as it should. so, one of the parts is acting up. and BOTH channels are doing the same thing. so, its not like i have two bad parts in the exact same place doing the same thing. thats too unlikely.
edit:
thanks for the offer. i MIGHT take you up on it. however, this is a phantom mystery board. look how many threads there are. and i have hundreds of personal emails from members of this forum helping me via email. after about a year, its still doing the same thing. i dont know if i would want to subject you to that kinda frustration. |
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| poobah |
OK,
Now put your meter on AC RMS, on the lowest setting (mV), and see if you can measure some AC across ANY of the 750 Ohms...
With the input shorted (+ to -) you should see nothing...
;) |
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| mpmarino |
hey cowanrg,
do you have those back to back zeners at input to ground in the circuit? If so, pull 'em out temporarily...they could be the problem. Just be careful to ground any input cable prior to hooking it up so u don't fry your fets.
marc
edit: I am talking about the pre circuit..NOT the PS. |
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| cowanrg |
a bit earlier in this thread a member (magura maybe?) suggested a leaky zener or something. it could be that. i never bothered checking it out because i put the project on the shelf and didnt mess with it.
but, its worth a shot. its strange that it would happen on both channels though. ill remove those and see what happens. |
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| poobah |
It would be doubtful that you would wind up with bad zeners in both channels... We have been told that to one degree or another; both channels have the same (bad) performance.
:D |
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| cowanrg |
| true. but lets say i hooked it up to something naughty at one time and it blew the zeners. it would have done so for both channels correct? |
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| poobah |
| It would take ALOT to blow those zeners... |
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| mpmarino |
| Your right, it would take a lot. Maybe they could have been overheated or bad out of the box? Anyway, regardless... when they go bad they make noise..it's something to try...a variable:xeye: |
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| Variac |
SerenghetiPlains:
Its considered a serious violation of the forum rules to publish private e-mail. You could easily pointed out that you had received a mistakenly addressed e-mail without publishing it. Another violation will have consequences.
Variac
DIY Moderator |
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| serengetiplains |
| Variac, can you kindly point me to where the rule is posted? |
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| cowanrg |
| i know im not a moderator, but as the starter of this thread, any more "personal" stuff should be dealt wtih privately, as in not in this thread. |
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| Variac |
Tom,
The rule is not posted. Not posting private emails is basic courtesy.
I assumed that you were not aware of this and that is why I mentioned it and did nothing other than move the post. This will help alert people that we don't allow this.
In the past people who have done so knowing that it is not permitted have gotten bin time.
I think cowanrg has a point- let's focus on his possessed preamp and not get offf topic. |
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| cowanrg |
well, as per poobah's suggestion, i replaced the 750ohm power resistors with some lower inductance ones. im not sure if they are non-inducting, but they are at least better than what i had.
sure enough, it really helped out. im not totally sure if it "fixed" the problem, but it certainly helped out a LOT. now i need to see if its a grounding issue or not. its still got a bit of noise, but it seems to be only a hum now. so, it could be a grounding issue.
BUT, i surely wont be putting those old resistors back. it still has the turn on issue though. however, its now fixed with the velleman unit. before it was so bad that the velleman couldnt even work. now it does. so thats nice.
i have another set of resistors to try that are supposedly zero-inductance, so ill try those to see if gets better, or fixes it. ill have to look at the scope and see whats exactly going on.
edit:
variac is totally right, this thing is possessed. |
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| poobah |
You can try... but don't hold any hope for those NH's in there... those are power resistors meant for different things. You just need a nice plain jane 3W metal film or metal oxide in there.
Oh, and ditch the big black heat sink, it ain't helping things...
Cheers... |
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| cowanrg |
| quote: | Originally posted by poobah
You can try... but don't hold any hope for those NH's in there... those are power resistors meant for different things. You just need a nice plain jane 3W metal film or metal oxide in there.
Oh, and ditch the big black heat sink, it ain't helping things...
Cheers... |
the big black heatsink hasnt been on for quite some time. and why is it not helping??? |
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| poobah |
The big black heat sink is making a capacitor (a very small one) between all your outputs (drains), it probably isn't hurting things... but it is NOT helping anything either. The circuit will be just fine with little $0.50 heat sinks that sit flat on the board.
:D |
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| Super_BQ |
One thing i've noticed on my BLS preamp is the transistors and 750/1.5Kohm resistors tend to give off a LOT of heat. So much that I had to upgrade my heatsinks and chassis mount the resistors.
Some simple checks if you have noise: check to make sure your transistors are completely isolated (ie. separate heatsink or fets isolated with sillypads or mica insulators).
http://www.geocities.com/super_bq/BLS1.html
My 4 channel BLS preamp appeared to be a disaster for ground noise. 2 power supply boards and 4 signal boards ALL off 1 toroidal power supply. I've upgraded to a much bigger 300VA donut and i'll agree, it's MUCH safer than what I had before.
BQ |
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| jh6you |
I use BOSOZ for unbalanced input and balanced output.
I had the unbalanced volume attenuator at input with ¡°somewhat¡± noise.
Later, I switched it into the balanced attenuator at output with ¡°dead¡± noise.
Good luck.
Regards
jh |
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| cowanrg |
i really wish i could test the preamp on a full balanced system. thats a LOT of work, as i dont have one here, so id have to make one, or find one... as much time as i have invested in this, i think its almost time to call it even.
a month or so ago, someone saw this thread and offered to sell me a P1.7 board fully populated and tested for a very low price. build quality was great and price was even better. not very DIY, i know, but at this point, this isnt fun anymore. i do this for fun, not for work.
i have a few other things on my plate, but im going to play with the new boards and see if they work ok. if they do, i will have a nice project for sale in the trading post for highest bidder...
i hate giving up on stuff, but for those of you who have been following this project, ive had this thing built for over a year, and been troubleshooting ever since. almost every single part has been replaced at least twice. its getting old... |
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| cowanrg |
| quote: | Originally posted by Super_BQ
One thing i've noticed on my BLS preamp is the transistors and 750/1.5Kohm resistors tend to give off a LOT of heat. So much that I had to upgrade my heatsinks and chassis mount the resistors.
Some simple checks if you have noise: check to make sure your transistors are completely isolated (ie. separate heatsink or fets isolated with sillypads or mica insulators).
http://www.geocities.com/super_bq/BLS1.html
My 4 channel BLS preamp appeared to be a disaster for ground noise. 2 power supply boards and 4 signal boards ALL off 1 toroidal power supply. I've upgraded to a much bigger 300VA donut and i'll agree, it's MUCH safer than what I had before.
BQ |
my transistors are FULL isolated. they have a little aluminum l-bracket for a heatsink right now, just enough so they dont fry or get too hot. they are not connected to eachother. even before, they had mica isolators, the l-brackets, AND, i used all nylon screws, just in case... but now, they are just kinda floating in free air. i dont have it on more than a minute at a time though, so they arent getting too hot...
also, i think my 800va xformer is big enough. i have tried it with lower power stuff too, a single 50va (for one channel, just as a test), and a 200va also. both had similar (or worse) results... |
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| lgreen |
It took me a full 2 years to get my 1st bosoz built and working. I understand the frustration, I was there about 5 times.
People might fault you for giving up, but not me, I barely made it. |
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| jh6you |
| quote: | Originally posted by cowanrg
. . . , but at this point, this isnt fun anymore. i do this for fun, . . .
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Fun not anymore . . . ? OK, here is more.
The original BOSOZ has one C of 1000uF just behind the bridge rectifier.
Replace it with CRCRCRC as shown in the sketch below, Fig.B.
Open you eyes wide and look at the location of the ground point.
Might be a part of help for cleaning up the noise.
Enjoy. :)
Regards
jh
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diyAudio seems to be getting ugly daybyday . . . |
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