Great news!
I kept measuring those MOSFETs I had pulled and since the gate > drain measured inf. I figured it might not hurt anyting to reinstall them and see what the DC offset would be. So I soldered them back in and hooked it up to a power supply with the 100ohm 5W resistors installed. Hoorah, 5mV at the output.
So I mounted it into the case and hooked everything back up. Still only 5mV at full power so I hooked up a speaker and it sounds great!
I ran the amp hard for two hours with my JBL 4425s to two of the channels and a JBL B360 sup hooked to the center channel. Absolutely great and it barely got warm at all. This is a keeper.
Blessings, Terry
I kept measuring those MOSFETs I had pulled and since the gate > drain measured inf. I figured it might not hurt anyting to reinstall them and see what the DC offset would be. So I soldered them back in and hooked it up to a power supply with the 100ohm 5W resistors installed. Hoorah, 5mV at the output.
So I mounted it into the case and hooked everything back up. Still only 5mV at full power so I hooked up a speaker and it sounds great!
I ran the amp hard for two hours with my JBL 4425s to two of the channels and a JBL B360 sup hooked to the center channel. Absolutely great and it barely got warm at all. This is a keeper.
Blessings, Terry
Hmmm....
So the good news is that the amp works, without replacement of components (if I understand it correctly?).
The bad news is, it didn't before. Unless it was tested with all components in place, but accidental solder bridges removed), we cannot explain what has changed.
Is this correct, or haven't you tried to turn it on after removal of the solder bridges?
Other than that, CONGRATULATIONS on the completion of your first DIY project, Terry!!!
Jennice
So the good news is that the amp works, without replacement of components (if I understand it correctly?).
The bad news is, it didn't before. Unless it was tested with all components in place, but accidental solder bridges removed), we cannot explain what has changed.
Is this correct, or haven't you tried to turn it on after removal of the solder bridges?
Other than that, CONGRATULATIONS on the completion of your first DIY project, Terry!!!
Jennice
Actually, the very first thing I did was remove the solder bridge, but I was still getting rail voltage at the output. Bob Ellis had recommended checking Q7 and I found it to be faulty. I replaced it. I now believe that was the problem because that is the only thing I changed other than removing the solder bridge and now the channel works. I was still getting a kind of funny reading between the source and drain on one of the MOSFETs but it seems to be working just fine. I was able to adjust the bias fine and have very low mV on the output.
It feels very good to have this working. Thanks to everyone for all the help. There is no way I could have done this without you guys.
Blessings, Terry
Terry,
I must admit that it was with a touch of "I hope this goes well" and "I wonder if he knows what he's up to?" feeling in my stomach that I (for my part) started supporting you with.
Then again, every DIY'er has to start somewhere, regardless how many or few books he's read, and support is what this forum is about, I think.
I'm just happy for you to have solved the last problem and have yourt project completed with 100% success (even if the costs were higher than expected).
SOOooooo... what'll be next, Terry?
Jennice
I must admit that it was with a touch of "I hope this goes well" and "I wonder if he knows what he's up to?" feeling in my stomach that I (for my part) started supporting you with.
Then again, every DIY'er has to start somewhere, regardless how many or few books he's read, and support is what this forum is about, I think.
I'm just happy for you to have solved the last problem and have yourt project completed with 100% success (even if the costs were higher than expected).
SOOooooo... what'll be next, Terry?
Jennice
For my nest project, I'm thinking about a Super Leach amp so I can take advantage of the Toriod I bought that was too big for this project. I've got my name on a list for the PCB's for that amp.
Truth is I'm thinking about building a good preamp that I can put in a matching case to this amp. Might look real nice in the right kind of rack. Do you know of any 5.1 DIY preamp designs?
So many designs, so little time.
Blessings, Terry
Truth is I'm thinking about building a good preamp that I can put in a matching case to this amp. Might look real nice in the right kind of rack. Do you know of any 5.1 DIY preamp designs?
So many designs, so little time.
Blessings, Terry
I don't think that a DIY 5.1 decoder / pre-amp will be easy to build. After all, it involves quite a bit of signal processing. After decoding, there's volume control. Syncronizing 5 (6) channels volume isn't the easiest thing on the planet, unless you wanty to mechanically hook up 3 stereo pots to turn together.
There are digitally controlled potentiometer chips and dedicated digitally controlled volume control circuits, but using these chips isn't really in my spirit of DIY, aiming at quality as good as I can make it.
Jennice
There are digitally controlled potentiometer chips and dedicated digitally controlled volume control circuits, but using these chips isn't really in my spirit of DIY, aiming at quality as good as I can make it.
Jennice
I was at a high end shop the other day where they has an (expensive) 5.2 preamp, but with one difference. It was analog only. Many of the newer all-fomat disc players provide 5.1 of analog including bass management and all the bells-and-whistles. They also have DACs as good as most pre-amps. So you combine a disc player that does all the multichannel processing and conversion to analog and you eliminate one set of redundant digital processing. This also keeps digital circuitry out of your pre-amps enclosure.
In the commercial product mentioned above they claim a noise floor 10-20dB below their sister product that does it's own digital processing.
So . . . if you really want to build a 5.1 preamp consider getting a 5.1 source (Disc player) that provides all the digital processing and gives you analog outputs.
Possible flaw: what if you want to use a second 5.1 source such as the 5.1 audio that comes with some HDTV set-top boxes. Then you have a problem because I don't think ANY of these have analog outputs - bummer.
In the commercial product mentioned above they claim a noise floor 10-20dB below their sister product that does it's own digital processing.
So . . . if you really want to build a 5.1 preamp consider getting a 5.1 source (Disc player) that provides all the digital processing and gives you analog outputs.
Possible flaw: what if you want to use a second 5.1 source such as the 5.1 audio that comes with some HDTV set-top boxes. Then you have a problem because I don't think ANY of these have analog outputs - bummer.
yeah i think that might be what Terry was thinking of doing?
the 6channel DAC in even my cheap as chips budgo DVD player is quite reasonable (a burr brown item) , all it needs is better opamps , dc blocking caps , and to get rid of the switchmode or maybe i can filter it more im not sure, but thats getting offtopic .
point being i think a reasonable 5.1 source with onboard analouge would have good potential to be modded as i intend to do , and have rewarding results.
the 6channel DAC in even my cheap as chips budgo DVD player is quite reasonable (a burr brown item) , all it needs is better opamps , dc blocking caps , and to get rid of the switchmode or maybe i can filter it more im not sure, but thats getting offtopic .
point being i think a reasonable 5.1 source with onboard analouge would have good potential to be modded as i intend to do , and have rewarding results.
After thinking about this, maybe a 5.1 preamp is a little ambitious for a second project.
I should probably stick to the "Keep It Simple Stupid" method until I get a little better grasp on all of this.
You guys have all been so helpful, I'd hate to wear out my welcome.
While I'm waiting for the Leach super amp boards to become available, I think I'll spend some time listening to my new amp. It's been a while since I've just sat a listened to music, just for the joy of it. Maybe I'll work on the acoustics of my room while I'm at it. That's something that's long overdue.
Blessings, Terry
I should probably stick to the "Keep It Simple Stupid" method until I get a little better grasp on all of this.
You guys have all been so helpful, I'd hate to wear out my welcome.
While I'm waiting for the Leach super amp boards to become available, I think I'll spend some time listening to my new amp. It's been a while since I've just sat a listened to music, just for the joy of it. Maybe I'll work on the acoustics of my room while I'm at it. That's something that's long overdue.
Blessings, Terry
Terry,
If we were to get tired of you, we would let you know and just wouldn't reply. That's no problem yet, though.
If I wasn't prepared to help with whatever I can (and can find time for, before the spouse starts yelling ), I wouldn't feel entitled to the support I've got with my questions on this forum.
This isn't meant to be a comment about you not being able to help, as we all started somewhere, and most have probably been in your situation.
If I recall correctly, you don't know very much about the electronics. Maybe this is the time to put on some good music, and listen to your first achievement, while you read some books about the components and how they work. Just a suggestion.
Jennice
If we were to get tired of you, we would let you know and just wouldn't reply. That's no problem yet, though.
If I wasn't prepared to help with whatever I can (and can find time for, before the spouse starts yelling
), I wouldn't feel entitled to the support I've got with my questions on this forum.This isn't meant to be a comment about you not being able to help, as we all started somewhere, and most have probably been in your situation.
If I recall correctly, you don't know very much about the electronics. Maybe this is the time to put on some good music, and listen to your first achievement, while you read some books about the components and how they work. Just a suggestion.
Jennice
Thanks Jens,
You're right. I do need to read a bit, if for no other reason than to begin to understand the terms and what they mean.I surely would like to understand transistors and how they function.
Any suggestions as to some reading material that a dummy can understand?
I've read your notes and they have helped a lot, but some of it still goes over my head. Shere's a good place to start?
Thanks, Terry
You're right. I do need to read a bit, if for no other reason than to begin to understand the terms and what they mean.I surely would like to understand transistors and how they function.
Any suggestions as to some reading material that a dummy can understand?
I've read your notes and they have helped a lot, but some of it still goes over my head. Shere's a good place to start?
Thanks, Terry
books
Hi Terry,
For the basics "Radio Shack" sells a work book or project book. It contains formulas, theory and circuits to build & test components.
Searching the internet using "basic bipolar transistor theory" ought to be helpful.
If the old Q7 transistor hasn't been tossed do the diode test and transistor gain (hfe) test in dmm socket and resistance. Also compare with a good working transistor almost any PNP type will do.
Joe
still4given said:
Hi Terry,
For the basics "Radio Shack" sells a work book or project book. It contains formulas, theory and circuits to build & test components.
Searching the internet using "basic bipolar transistor theory" ought to be helpful.
If the old Q7 transistor hasn't been tossed do the diode test and transistor gain (hfe) test in dmm socket and resistance. Also compare with a good working transistor almost any PNP type will do.
Joe
OK... So we're REALLY basic here....
No offence meant, Terry, it's just that from an engineers point of view this should be obvious, but then again, I spend years studying, so I OUGHT to know more then you on this issue. Each his own skills... I can't put together any notes that make music.
I have one book on speaker building from Radio Shack, and I like the way it is set up, so I agree with the suggestion to find their books.
When you've got a grip on things, you can advance to something like Barry Woollard's "Practical Electronics".
Where do my notes start giving you trouble? Maybe it's just not understandable to anyone but the author, so it needs a revision? I got little feedback on the notes, especially considering that it's downloaded 1.5 times a day on average (and it's been long since it's release!)
The most important subject to keep track of, is that some of the electronic components are current controlled devices, while others are voltage controlled. This requieres the designer to think differntly, depending on the situation.
Example (simplified and not 100% correct, but just to illustrate):
If you take an ordinary light bulb and connect it to your vario-transformer, the light intensity is voltage dependent. The more you turn up the vario, the more the bulb lights up.
If you take a NPN transistor like the BC547 (which is cheap and actually very good), the controlling pin (BASE) is operated by the current flowing into it, not the voltage applied to it.
Jennice
No offence meant, Terry, it's just that from an engineers point of view this should be obvious, but then again, I spend years studying, so I OUGHT to know more then you on this issue. Each his own skills... I can't put together any notes that make music.
I have one book on speaker building from Radio Shack, and I like the way it is set up, so I agree with the suggestion to find their books.
When you've got a grip on things, you can advance to something like Barry Woollard's "Practical Electronics".
Where do my notes start giving you trouble? Maybe it's just not understandable to anyone but the author, so it needs a revision? I got little feedback on the notes, especially considering that it's downloaded 1.5 times a day on average (and it's been long since it's release!)
The most important subject to keep track of, is that some of the electronic components are current controlled devices, while others are voltage controlled. This requieres the designer to think differntly, depending on the situation.
Example (simplified and not 100% correct, but just to illustrate):
If you take an ordinary light bulb and connect it to your vario-transformer, the light intensity is voltage dependent. The more you turn up the vario, the more the bulb lights up.
If you take a NPN transistor like the BC547 (which is cheap and actually very good), the controlling pin (BASE) is operated by the current flowing into it, not the voltage applied to it.
Jennice
Thanks both of you. I will look into the books you've recommended.
Jens,
I read through your notes again this morning, after I posted. I hadn't realized how much I've learned through putting this amp together and all the advise you guys have shared. I understood a great deal more this morning than I did the first time I read through them.
I'm surprised you haven't gotten more feedback. I think it is a great resource! It was very good of you to take the time and effort to do that.
Blessings, Terry
Jens,
I read through your notes again this morning, after I posted. I hadn't realized how much I've learned through putting this amp together and all the advise you guys have shared. I understood a great deal more this morning than I did the first time I read through them.
I'm surprised you haven't gotten more feedback. I think it is a great resource! It was very good of you to take the time and effort to do that.
Blessings, Terry
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.