traderbam said:What you say in the earlier post seems to be inconsistent with what you just said.
Previously, you said that when using Mooly's psu the hum only arises when you attach the phono stage.
Now, you seem to be saying that the hum has nothing to do with whether the phono stage is attached, the hum arises when you use a poorly regulated psu.
Would you clarify this?
Okay. I did jinx myself but not intentionally.
The transfo creats buzz when I connect the h-amp to my main hi-fi system. Very low audible buzz when used in the workshop with a CD-Rom unit.
Firstly I am going to order a regulator and then see what's up...
D
A single cap will VERY unlikely produce the clean supply a simple class A amp will need...
Add a second channel to it, and its probably double as hard.
Look at the circuit carefully, see how variations in supply (ripple) will modulate biasing and virtualy every part of the circuit... It also has no method for dealing with noise...
I think the battery supply will be the best.. it has a cost factor and they need to be replaced over time... just not sure how many hours you'd be able to get in on a battery...
I think some of the concepts you have been showed so far will also work...
Also it will not hurt looking at other small class A amps, like the JLH etc... and see how their supplies evolved....
The regulator I pointed out earlier, originated from there...
Add a second channel to it, and its probably double as hard.
Look at the circuit carefully, see how variations in supply (ripple) will modulate biasing and virtualy every part of the circuit... It also has no method for dealing with noise...
I think the battery supply will be the best.. it has a cost factor and they need to be replaced over time... just not sure how many hours you'd be able to get in on a battery...
I think some of the concepts you have been showed so far will also work...
Also it will not hurt looking at other small class A amps, like the JLH etc... and see how their supplies evolved....
The regulator I pointed out earlier, originated from there...
it seems that you didnt
read my post ......
but thats ok
its not the regulator that is going to solve your problem even if you use my circuit without regulator will work like hell ( presumed that volyage produced is correct )
what you dont understand is that all this ground rooting issue ...
for example i dont understand where the word PC is related to your set up .....
for your information there almost certain that the ground of the box ...the sassi of your pc is not isolted from signal ground of audio in and out of your pc......
meaning that if you conect this PC to this preamp you will get a buzz no mater how well regulated is you psu ....
there i rest my case ....when you find out you will let me know
read my post ......
but thats ok
its not the regulator that is going to solve your problem even if you use my circuit without regulator will work like hell ( presumed that volyage produced is correct )
what you dont understand is that all this ground rooting issue ...
for example i dont understand where the word PC is related to your set up .....
for your information there almost certain that the ground of the box ...the sassi of your pc is not isolted from signal ground of audio in and out of your pc......
meaning that if you conect this PC to this preamp you will get a buzz no mater how well regulated is you psu ....
there i rest my case ....when you find out you will let me know
I do agree though, that if there is a ground loop problem, no amount of regulation will work... A handy tool, is to have some wires with crocodile clips on both ends to investigate diffirent grounding solutions...
Sakis re the PC, I think he just tried to point out that his PC was quiet through another amp.
Sakis re the PC, I think he just tried to point out that his PC was quiet through another amp.
I know the feeling!
It is tricky in these posts to understand anyone clearly. It helps if you deliberately try to over-explain and make sure you use very specific terminology.
For example, when you talk about "transfo creating buzz" do you mean mechanical noise?
This is not to be confused with buzz heard through the speakers, which is electrical in origin.
Now there are 3 classes of buzz being discussed in these posts:
1) buzz heard through the speaker, originating from psu ripple
2) buzz heard thought the speaker, originating from ground loop or stability issues
3) mechanical buzz, originating from the psu transformer
On anything that draws this current correct grounding is VITAL. If you are running two amps (left and right) one wrong connection will easily cause all this trouble. Are you using a proper star earth in the PSU. You can not connect grounds to any old point on the zero volt line.
You say you are familiar with "earth" faults and noises in which case you will know that the frequency and "characteristic sound" will help identify whether it is a true earth loop or PSU ripple problem or a wiring problem i.e. Is it mains frequency or F*2.
You say you are familiar with "earth" faults and noises in which case you will know that the frequency and "characteristic sound" will help identify whether it is a true earth loop or PSU ripple problem or a wiring problem i.e. Is it mains frequency or F*2.
Enter with 17 to 30 volts rectified...best results will
be when you adjust to 12 volts DC into your output.
The extra diode is to install when you need lower voltages...as this circuit will not adjust voltages lower than 6 volts (around that) with the zener diode (4V7) into the circuit..using a switch and producing a short into the zener (installing both in parallel) you gonna adjust from 2.5 volts and upper voltages till the maximum DC supply limit reduced by 1 or 2 volts because of power transistor saturating voltages.
Use to the power transistor, the big series pass regulator transistor, the one you have no number on it, the NPN you have, the NPN you like, the one can hold twice the current you gonna use...and install it into a good heatsink if needed....and this will depend your power demands..if 1 ampere, use 10 by 10 centimeters aluminium plate that will fit...... 2 amperes, then use two blades or 200 square centimeters (calculate one side only)...each 100 square centimeters will dissipate, easy, 10 watts of power...using that ratio you will have the needed dimensions.
Precise?.... no...nothing precise here.... precise is the day we gonna die...no negotiations...the moment, the hour, the day, the year, no negotiations possible.... this is precise.... eletronics use to have 10 percent of tollerances.
Other supplies can be as good as...but i doubt will be easier, cheaper and better.
Condensers are for 1 Ampere operation.... the bigger the units you decide to use, the better will be your results.
Carlos
be when you adjust to 12 volts DC into your output.
The extra diode is to install when you need lower voltages...as this circuit will not adjust voltages lower than 6 volts (around that) with the zener diode (4V7) into the circuit..using a switch and producing a short into the zener (installing both in parallel) you gonna adjust from 2.5 volts and upper voltages till the maximum DC supply limit reduced by 1 or 2 volts because of power transistor saturating voltages.
Use to the power transistor, the big series pass regulator transistor, the one you have no number on it, the NPN you have, the NPN you like, the one can hold twice the current you gonna use...and install it into a good heatsink if needed....and this will depend your power demands..if 1 ampere, use 10 by 10 centimeters aluminium plate that will fit...... 2 amperes, then use two blades or 200 square centimeters (calculate one side only)...each 100 square centimeters will dissipate, easy, 10 watts of power...using that ratio you will have the needed dimensions.
Precise?.... no...nothing precise here.... precise is the day we gonna die...no negotiations...the moment, the hour, the day, the year, no negotiations possible.... this is precise.... eletronics use to have 10 percent of tollerances.
Other supplies can be as good as...but i doubt will be easier, cheaper and better.
Condensers are for 1 Ampere operation.... the bigger the units you decide to use, the better will be your results.
Carlos
Attachments
Well boys.... do you know what drive us happy
What make us happy.
We turn happy when we are near the ones we like, and also when we are doing things we like...do not matter if makes sense or not.
As everything in our lifes, depends on the point of view....if you are tall, the others are not tall..... but for someone bigger than you are....you are mini or micro.
I would like to see this schematic Jacco Vermeullen
panzertoo@yahoo.com
Carlos
What make us happy.
We turn happy when we are near the ones we like, and also when we are doing things we like...do not matter if makes sense or not.
As everything in our lifes, depends on the point of view....if you are tall, the others are not tall..... but for someone bigger than you are....you are mini or micro.
I would like to see this schematic Jacco Vermeullen
panzertoo@yahoo.com
Carlos
Here is my findings
Mains PSU (Transfo with standard regulation)
Prominent Freq: -54dB at 108Hz
Battery
Prominent Freq: -67dB at 151Hz
See attached graphical measurement
Unit measured by 600 ohm dummy load on outputs tapped to Line in of soundcard. "Silence" recorded.
D
Mains PSU (Transfo with standard regulation)
Prominent Freq: -54dB at 108Hz
Battery
Prominent Freq: -67dB at 151Hz
See attached graphical measurement
Unit measured by 600 ohm dummy load on outputs tapped to Line in of soundcard. "Silence" recorded.
D
Attachments
Hi,
You might not think so but we are trying to help
If it's run off a lead acid battery where is the 151 hz from ? It has to be silent apart from thermal noise ( hiss ). And I think you said it was earlier when you used a battery.
What was the outcome of post #22
Do you have any zeners available up to 10 volts ANY AT ALL ? you can put them in series to make the voltage you want. Do you have a 7812 or a 7805 reg.
You might not think so but we are trying to help
If it's run off a lead acid battery where is the 151 hz from ? It has to be silent apart from thermal noise ( hiss ). And I think you said it was earlier when you used a battery.
What was the outcome of post #22
Do you have any zeners available up to 10 volts ANY AT ALL ? you can put them in series to make the voltage you want. Do you have a 7812 or a 7805 reg.
Mooly said:Hi,
You might not think so but we are trying to help
If it's run off a lead acid battery where is the 151 hz from ? It has to be silent apart from thermal noise ( hiss ). And I think you said it was earlier when you used a battery.
What was the outcome of post #22
Do you have any zeners available up to 10 volts ANY AT ALL ? you can put them in series to make the voltage you want. Do you have a 7812 or a 7805 reg.
Mooly - I appriciate every little piece of help and advice I get from guys like you.
I dont know where the 151Hz comes from on the battery but do notice the lower dBs - It is inaudible throught the headphones - probably induced by the soundcard... tiny bit of hiss is there but it is neglible.
I have no zeners and will have to order. I already have booked a 3A 12v regulator IC from RS Components.
D
As far as I can work out...
You have three possible inputs: PC soundcard, EAR and nothing at all.
You have 3 psus: battery, switchmode and linear regulated mains.
That's 9 combinations. I'm still not confident about which combinations hum and which don't.
I infer that any combination with battery or switchmode does not hum. Is this right?
This suggests that the amp hums sometimes with the regulated mains psu and sometimes not. If this is true then you only have a grounding problem.
If the amp hums with a regulated mains psu regardless of input type then you have a regulation issue and you might also have a grounding problem.
You have three possible inputs: PC soundcard, EAR and nothing at all.
You have 3 psus: battery, switchmode and linear regulated mains.
That's 9 combinations. I'm still not confident about which combinations hum and which don't.
I infer that any combination with battery or switchmode does not hum. Is this right?
This suggests that the amp hums sometimes with the regulated mains psu and sometimes not. If this is true then you only have a grounding problem.
If the amp hums with a regulated mains psu regardless of input type then you have a regulation issue and you might also have a grounding problem.
You can probably improve the situation somewhat by adding an emitter resistor at Q1, and changing a few values. See
http://www.dself.dsl.pipex.com/ampins/discrete/twoq.htm
The circuit below differs from the one on that page only minutely. It will sort out your biassing issue.
w
http://www.dself.dsl.pipex.com/ampins/discrete/twoq.htm
The circuit below differs from the one on that page only minutely. It will sort out your biassing issue.
An externally hosted image should be here but it was not working when we last tested it.
w
national makes the LM1085IS-12 regulator. it's a 3 amp device and a "low dropout" regulator, so you only need 13.3 volts for it to lock at 12V. it's a TO-263 package (like a TO-3P). they're about $3.00 US. i was going to suggest the LM78H12 or LM78K12, but can't find a current catalog with them. they were 5A and 3A devices in a TO-3 package. this would eliminate the PS ripple in a simple 3 terminal package. the only additional components required would be a pair of 0.1uf monolithic caps, a 1000uf-4700uf cap for the output side of the regulator, a 1N1004 diode (if you're using one of the 7800 series regs you need to protect the reg from backfeed when the power is shut off) and the appropriate heat sink.
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