Nice Variac! yes you could solder the resistor onto a blown fuse or directly to the fuse holder. But with a judicious twist of the knob on your variac, you don't really need it. I would start wiht low value fuses, though.
The light bulb goes in series with the power cord - but it is a no variac solution, too.
black wire --- switch --- fuse ---- light bulb ---- amp --- \
white wire --------------------------------------------/
having more than one voltmeter helps, but what I would do is start by monitoring the transformer output to be sure you get what you expect.
then hook up the bridge(s). Bring the voltage up and DC voltages ought to be roughly the same as the AC you just measured. - verify polarities.
Hook up the filter caps. Double check the polarity. bring up the voltage a little (5 volts output or so) and verify that you have DC on the caps. If you have a cap backwards you won't get much DC voltage, if any. If this tests good, bring the voltage up.
bleed off the caps and connect your amp. bring the voltage up slowly and check to see that the rails both come up together. they don't have to be exactly the same absolute voltage, but they should stay close. If not, check for backwards caps or transistors.
Now check voltages at the test points on the board as you bring it up to full voltage.
The light bulb goes in series with the power cord - but it is a no variac solution, too.
black wire --- switch --- fuse ---- light bulb ---- amp --- \
white wire --------------------------------------------/
having more than one voltmeter helps, but what I would do is start by monitoring the transformer output to be sure you get what you expect.
then hook up the bridge(s). Bring the voltage up and DC voltages ought to be roughly the same as the AC you just measured. - verify polarities.
Hook up the filter caps. Double check the polarity. bring up the voltage a little (5 volts output or so) and verify that you have DC on the caps. If you have a cap backwards you won't get much DC voltage, if any. If this tests good, bring the voltage up.
bleed off the caps and connect your amp. bring the voltage up slowly and check to see that the rails both come up together. they don't have to be exactly the same absolute voltage, but they should stay close. If not, check for backwards caps or transistors.
Now check voltages at the test points on the board as you bring it up to full voltage.
Terry,
Those bridge rectifiers should do fine for your project.
Just remember a little heat sink for them, or mount them to a good spot on the chassis. Not directly next to your amplifier electronics, as they will carry high peak currents. The magnetic field from this may interfere with your amp, causing audible hum. (or making it worse - few amps are 100% silent, when putting an ear to the speaker or measuring.)
BobEllis,
Are you 100% sure about that 100R 0.25W resistor. Usually, I bias my amps to use about 100-250mA idle. 100mA would cause 10V and 1W of power being burnt off in the resistor. To me, this aproach does not sound right...😕
Jennice
Those bridge rectifiers should do fine for your project.
Just remember a little heat sink for them, or mount them to a good spot on the chassis. Not directly next to your amplifier electronics, as they will carry high peak currents. The magnetic field from this may interfere with your amp, causing audible hum. (or making it worse - few amps are 100% silent, when putting an ear to the speaker or measuring.)
BobEllis,
Are you 100% sure about that 100R 0.25W resistor. Usually, I bias my amps to use about 100-250mA idle. 100mA would cause 10V and 1W of power being burnt off in the resistor. To me, this aproach does not sound right...😕
Jennice
Jennice,
The 100R is for verifying that nothing is catastrophically wrong. You're right, you couldn't bring the output stage up to full bias with them in there. There should be very low voltage when testing just the front end. With the output stage set to minimum bias they should last long enough to measure. With a major problem they will smoke instantly, but limit the current. Sorry if I wasn't clear.
With the completed amp, if the 100R lasts more than a second, shut it down and drop the fuses in, you should be good to go.
The 100R is for verifying that nothing is catastrophically wrong. You're right, you couldn't bring the output stage up to full bias with them in there. There should be very low voltage when testing just the front end. With the output stage set to minimum bias they should last long enough to measure. With a major problem they will smoke instantly, but limit the current. Sorry if I wasn't clear.
With the completed amp, if the 100R lasts more than a second, shut it down and drop the fuses in, you should be good to go.
It will e a few days before I am ready to power anything up. I don't even have heatsinks or a box for it yet. I did sit down and solder in all the parts that I have for the boards. Still waiting for a few to come in the mail.
I'm trying to get a good grasp on all of it before I put any power to anything.
Rod has this drawing for a power supply. It shows a resistor between each of the Filter caps. If I were to use say 10 caps, (five for each rail), should I put a resistor between each?
Thanks, Terry
I'm trying to get a good grasp on all of it before I put any power to anything.
Rod has this drawing for a power supply. It shows a resistor between each of the Filter caps. If I were to use say 10 caps, (five for each rail), should I put a resistor between each?
Thanks, Terry
still4given said:
No, I wouldn't put resistors between the next 4 caps in the PSU. Consider it to be a first order RC low pass filter (after the first cap). Actually I'm not sure I would use any resistor at all. You decrease hum (ripple) in the PSU but decrease output impedance, even if little. You know... we both use 5 caps per rail... I might just try it also, and see if it's a good idea for my circuit.
Jennice
Jennice said:
I would be interested in knowing what you find. I will be watching for your report. 😀
I still don't have a case or heatsink, so I'm not quite ready to put together the PSU.
Anyone know a good source for heatsinks? I will have a case made to fit the heatsinks one I get some.
Thanks, Terry
give steve at apexjr a call - he often has stuff that is not on his website. He's a decent guy, I've bought quite a bit of stuff from him.
HI, ref that psu drawing in still4given post; the star earth needs a rethink. The caps have a lot of hi current spikes flying back & forth on alternate AC cycles. These will contaminate the very small impedances between the various but separated earth connections shown on the drawing. The speaker returns and other earths and grounds (both clean and dirty) should be brought together at a separate star earth and then 1 cable or bolt to connect the star earth to the psu midpoint.
I have seen a number of designers recommending the RC filter in the PSU. I too await the results of your testing with and without the resistors.
Have you considered soft start?
regards Andrew T.
I have seen a number of designers recommending the RC filter in the PSU. I too await the results of your testing with and without the resistors.
Have you considered soft start?
regards Andrew T.
Terry,
I know it's been long... I promised a feed-back on the resistor/capacitor issue on the PSU, but I just haven't found time to get on with the project recenly. I hope to find some time for it in december, though.
Jennice
I know it's been long... I promised a feed-back on the resistor/capacitor issue on the PSU, but I just haven't found time to get on with the project recenly. I hope to find some time for it in december, though.
Jennice
Hookup wire questions.
I haven't seen this discussed anywhere, and this seemed like a reasonable thread to ask the questions.
1. Are there any standards or conventions regarding wire color that it would be a good idea to use in building an amp?
2. Stranded or solid?
3. Audiophile type wire? Teflon insulation? Silver plated copper? Oxygen free copper?
4. Recommended gauge sizes for different parts of the amplifier?
I haven't seen this discussed anywhere, and this seemed like a reasonable thread to ask the questions.
1. Are there any standards or conventions regarding wire color that it would be a good idea to use in building an amp?
2. Stranded or solid?
3. Audiophile type wire? Teflon insulation? Silver plated copper? Oxygen free copper?
4. Recommended gauge sizes for different parts of the amplifier?
GregD,
Wire colours:
Only the mains side has standards for this. However, the red is ususlly used as "+" (positive) in the DC side. Personally, I like the blue as neutral (GND) (like on the AC mains side of the transformer), and black as "-" (negative).
On the mains side, the green/yellow is earth, while brown is live (phase). (at least here in Denmark, northern europe).
Stranded or solid:
I prefer solid, simply because it keeps the amp tidy. 😉
Most (non-signal-level) cabeling I do is with ordinary solid installation wire (1.5 mm2 copper where I live).
Audiophile wire:
Personally, I don't give much for the term Audiophile [whatever component]. To me, it's 95% marketing, and a tiny bit research.
I even saw an add for a wooden knob, intended as replacement for the standard volume knob. We're not talking a new potentiometer - we're talking about a WOODEN KNOB!
It's special wood and laquer coating should have better resonance properties, which should result in better sound. The price tag was far beyond US$ 100 a piece! Judge for yourself...
Ahem... to return to your question:
During the recording process, the audio signals pass through a lot of not so incredible high-end wires and connectors in the studio. Thus, I belive in the use of well shielded cables, but nothing too fancy. The most important thing (to me) is that the shielding should not be going around the insulation one way only. This creates a coil effect (inductor), which induces error voltages at the presence of a magnetic field (usually from your power supply).
Wire gauge: Some times I have used aluminum or copper plates as star ground reference, at other times just a ground screw (bolt), to which I attach the wires with round terminals. Both have worked fine for me. The rest has been 1.5mm2 solid, and has not caused problems for my 300W amp.
I've spent my resources on good output transistors and the power supply instead of buying very expensive cables.
Just my 2 cents.
Jennice
Wire colours:
Only the mains side has standards for this. However, the red is ususlly used as "+" (positive) in the DC side. Personally, I like the blue as neutral (GND) (like on the AC mains side of the transformer), and black as "-" (negative).
On the mains side, the green/yellow is earth, while brown is live (phase). (at least here in Denmark, northern europe).
Stranded or solid:
I prefer solid, simply because it keeps the amp tidy. 😉
Most (non-signal-level) cabeling I do is with ordinary solid installation wire (1.5 mm2 copper where I live).
Audiophile wire:
Personally, I don't give much for the term Audiophile [whatever component]. To me, it's 95% marketing, and a tiny bit research.
I even saw an add for a wooden knob, intended as replacement for the standard volume knob. We're not talking a new potentiometer - we're talking about a WOODEN KNOB!
It's special wood and laquer coating should have better resonance properties, which should result in better sound. The price tag was far beyond US$ 100 a piece! Judge for yourself...
Ahem... to return to your question:
During the recording process, the audio signals pass through a lot of not so incredible high-end wires and connectors in the studio. Thus, I belive in the use of well shielded cables, but nothing too fancy. The most important thing (to me) is that the shielding should not be going around the insulation one way only. This creates a coil effect (inductor), which induces error voltages at the presence of a magnetic field (usually from your power supply).
Wire gauge: Some times I have used aluminum or copper plates as star ground reference, at other times just a ground screw (bolt), to which I attach the wires with round terminals. Both have worked fine for me. The rest has been 1.5mm2 solid, and has not caused problems for my 300W amp.
I've spent my resources on good output transistors and the power supply instead of buying very expensive cables.
Just my 2 cents.
Jennice
Thanks!
I don't quite get the following however.
I don't quite get the following however.
Do you mean that you use some shielded cables inside the amp? If so, where? Or only for connections between system components?Jennice said:
I use shielded cables between the audio input connectors and the amplifier PCB, and sometimes between the PCB and the bias-regulating Vbe-multiplier transistor.
Jennice
Jennice
OK, well, I've got my PCBs built and have kind of hit a wall trying to decide what to do next. I'm kinda thinkin' about making this a two channel amp instead fo the three channel I started out to build. I'm thinking maybe I'm making this too complicated for a first project. If I stay stereo I can get by using just one transformer which should simplify things in the PSU area. Still haven't found a suitible heatsink but am watching some on ebay right now.
Any suggestions on how big a heatsink I need for these ESP P101 boards. I've seen all kinds of different sizes being used. I've even seen pictures of folks using solid, 1/2" thick aluminum for heat sinks. I have no idea how to figure what I need.
Thanks, Terry
Any suggestions on how big a heatsink I need for these ESP P101 boards. I've seen all kinds of different sizes being used. I've even seen pictures of folks using solid, 1/2" thick aluminum for heat sinks. I have no idea how to figure what I need.
Thanks, Terry
Hi Terry,
http://sound.westhost.com/heatsinks.htm
It's a bit of a long read, math is not too hard even for me.
Or take a look at destroyer X's info on the heat sink problem thread under Solid State. Very practical advice from the South of US where it gets kinda warm.
Prosit
http://sound.westhost.com/heatsinks.htm
It's a bit of a long read, math is not too hard even for me.
Or take a look at destroyer X's info on the heat sink problem thread under Solid State. Very practical advice from the South of US where it gets kinda warm.
Prosit
Greetings,
I have read all the way through this thread and let me say that I am very, very impressed with the help everyone here is giving still4given, (and the rest of us). Most other forums would have told him to search, search and search again. Not one mention of this. Cool.
I am currently in the process of aquiring the components for a seven channel ESP P101 amp and this thread has helped me on a few issues.
Just a note, I have gotten all my components from Newark and they have been very good to me, fast and curtious.
Just a suggestion on the heatsink issue, as you can imagine I have wrestled with this one for a while. I have searched long and hard and have come to the conclusion to purchase mine from Conrad Heatsinks in Australia. A friend of mine is building two mono P101's and he already got his, they didn't take too long to arrive. When they did arrive they were very well packed and just awesome heatsinks. VERY NICE. I have no doubt they are some of the best around. Also very reasonable prices, around $20 each. www.conradheatsinks.com . Check them out.
Later
I have read all the way through this thread and let me say that I am very, very impressed with the help everyone here is giving still4given, (and the rest of us). Most other forums would have told him to search, search and search again. Not one mention of this. Cool.
I am currently in the process of aquiring the components for a seven channel ESP P101 amp and this thread has helped me on a few issues.
Just a note, I have gotten all my components from Newark and they have been very good to me, fast and curtious.
Just a suggestion on the heatsink issue, as you can imagine I have wrestled with this one for a while. I have searched long and hard and have come to the conclusion to purchase mine from Conrad Heatsinks in Australia. A friend of mine is building two mono P101's and he already got his, they didn't take too long to arrive. When they did arrive they were very well packed and just awesome heatsinks. VERY NICE. I have no doubt they are some of the best around. Also very reasonable prices, around $20 each. www.conradheatsinks.com . Check them out.
Later
Nice selection of heat sinks, they got there 🙂
Terry,
The PSU shouldn't give you that much more trouble when using two transformers. My main concern is the physical size of the completed amp.
Have you tried to lay out the components and PCB's roughly the way you have in mind, and see how it would all line up?
This is also a good way to check is there's something you've forgotten.
DestroyerX has a real safe approach o heat sink calculation. Then again, he has a hot environment, but it's only a relative off-set, while the math is the same.
This reminds me... I got that issue covered in my notes also. That should give you an idea of, what size you'll need.
I can't remember the rated power per channel you plan on - can you please repeat that? (Then I'll give you my suggestion on heat sinking).
Jennice
Terry,
The PSU shouldn't give you that much more trouble when using two transformers. My main concern is the physical size of the completed amp.
Have you tried to lay out the components and PCB's roughly the way you have in mind, and see how it would all line up?
This is also a good way to check is there's something you've forgotten.
DestroyerX has a real safe approach o heat sink calculation. Then again, he has a hot environment, but it's only a relative off-set, while the math is the same.
This reminds me... I got that issue covered in my notes also. That should give you an idea of, what size you'll need.
I can't remember the rated power per channel you plan on - can you please repeat that? (Then I'll give you my suggestion on heat sinking).
Jennice
Wow, those Conrad heatsinks look nice. I may go that way. Would make building the case easier.
Jens,
I believe my Hafler tranformers put out 63V per rail. According to Rod that should yield 200WPC.
If I go with the three channel I would have to have two PCBs on one side and one on the other. I'm not sure if having more heatsink for one PCB will effect things or not. For esthetic reasons, I would rather not have a smaller heatsink on one side. Perhaps I could use four seperate heatsinks, two per side and just not use one of them.
I'll check through your notes again for heatsinks. There is a lot to absorb there and I'm sure I missed a lot the first time through.
Thanks again, Terry
Jens,
I believe my Hafler tranformers put out 63V per rail. According to Rod that should yield 200WPC.
If I go with the three channel I would have to have two PCBs on one side and one on the other. I'm not sure if having more heatsink for one PCB will effect things or not. For esthetic reasons, I would rather not have a smaller heatsink on one side. Perhaps I could use four seperate heatsinks, two per side and just not use one of them.
I'll check through your notes again for heatsinks. There is a lot to absorb there and I'm sure I missed a lot the first time through.
Thanks again, Terry
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