Hi everyone,
Let me tell you my story and ask for advice.
One day I decide to upgrade my home stereo system and sold my Technics amplifier, which I was using for last 15 years.
Looking for an amplifier to replace it I found a guy who was selling nice looking Denon poa 3000. Price was lower then the other's was asking for this model. He told me that he bought it on Japan auction as working, but when it arrived it doesn't work properly, seems like protection circuit was blocking it. Seller told me he didn't want to fix it, and sell it as is. I decide to buy it, and fix it.
When amplifier arrived, I've open it and was very "surprised" to see that the right channel pcb is missing, but the output transistors was on the place.
The first idea was just find missing pcb, but it wasn't so easy. I spent a lot of time on different web sites looking for it, even contact with Denon dealer in UK, but nothing.
The other bad thing is, that when I sought how this amplifier assembled I wasn't impressed, it's looks like the guy took soldering iron in hands first time in his life and made this amplifier. Connections between boards made with awful pins, even signal wires...
That's why I decide to totally rebuild it.
For now I have:
Great chassis, with pretty power indicators.
4 huge heatsinks.
10 transistors 2 sa1216, and same quantity of 2sc2922.
Unfortunately I will have to replace power transformer, as it's for Japanese 100v, and we have 220-230, and if amplifier will be rebuild I see no reason to keep it.
So the question is: what would you do, if you have such parts, and idea to build amplifier?
I spent a lot of time deciding what to do. What scheme to choose to build a new amplifier.
The idea is to build good 100 - 150watt amplifier probably using transistors from Denon, I just can't decide.
Sorry for mistakes in text, I did my best to avoid it 🙂
Let me tell you my story and ask for advice.
One day I decide to upgrade my home stereo system and sold my Technics amplifier, which I was using for last 15 years.
Looking for an amplifier to replace it I found a guy who was selling nice looking Denon poa 3000. Price was lower then the other's was asking for this model. He told me that he bought it on Japan auction as working, but when it arrived it doesn't work properly, seems like protection circuit was blocking it. Seller told me he didn't want to fix it, and sell it as is. I decide to buy it, and fix it.
When amplifier arrived, I've open it and was very "surprised" to see that the right channel pcb is missing, but the output transistors was on the place.
The first idea was just find missing pcb, but it wasn't so easy. I spent a lot of time on different web sites looking for it, even contact with Denon dealer in UK, but nothing.
The other bad thing is, that when I sought how this amplifier assembled I wasn't impressed, it's looks like the guy took soldering iron in hands first time in his life and made this amplifier. Connections between boards made with awful pins, even signal wires...
That's why I decide to totally rebuild it.
For now I have:
Great chassis, with pretty power indicators.
4 huge heatsinks.
10 transistors 2 sa1216, and same quantity of 2sc2922.
Unfortunately I will have to replace power transformer, as it's for Japanese 100v, and we have 220-230, and if amplifier will be rebuild I see no reason to keep it.
So the question is: what would you do, if you have such parts, and idea to build amplifier?
I spent a lot of time deciding what to do. What scheme to choose to build a new amplifier.
The idea is to build good 100 - 150watt amplifier probably using transistors from Denon, I just can't decide.
Sorry for mistakes in text, I did my best to avoid it 🙂
Sounds a bit like an expensive door stop to me.
Yes use the parts and make a nice power amplifier from them.
Yes use the parts and make a nice power amplifier from them.
For sure this will be quite expensive project, so far transportation and The unit it self cost me about 450$, this is similar to price of good chassis with heatsinks only, as "bonus" I have transistors, 4 nice 25000uF capacitors, and some other stuff. For sure I can sell it now as is to someone else, but I feel a huge potential in this Denon. As almost 40 years passed after it was made (mfd1980), new technologies allow me to make it better then it was, I hope so.
Hello Sergeym.
I guess the first thing to do is to make sure the power transistors are all ok, as i understand you have 10 NPN, and 10 PNP, if all of them checks out ok, then they are a good base to start on.
The next thing is to decide the power, you said up to 150W, but not if you want it on 4 or 8 Ohm, and that is quite important. If you choose the 4 Ohm speakers, then you can calculate the needed power supply, and that will give you the required power transformer. Depending on the exact schematic, 150W on 4 Ohm would require about 40, maybe 45Vcc of rail voltage ( that would be +/-40 to +/-45Vcc ). I think a power transformer with 2x30V or 2x35Vac, and about 6A should be enough.
You can search for a power amplifier project that uses 2 complementary BJT output pairs, and that can work with that power supply. There are loads on the net, just make sure you choose wisely.
I guess the first thing to do is to make sure the power transistors are all ok, as i understand you have 10 NPN, and 10 PNP, if all of them checks out ok, then they are a good base to start on.
The next thing is to decide the power, you said up to 150W, but not if you want it on 4 or 8 Ohm, and that is quite important. If you choose the 4 Ohm speakers, then you can calculate the needed power supply, and that will give you the required power transformer. Depending on the exact schematic, 150W on 4 Ohm would require about 40, maybe 45Vcc of rail voltage ( that would be +/-40 to +/-45Vcc ). I think a power transformer with 2x30V or 2x35Vac, and about 6A should be enough.
You can search for a power amplifier project that uses 2 complementary BJT output pairs, and that can work with that power supply. There are loads on the net, just make sure you choose wisely.
Last edited:
Hi Sergeym,
Very good amplifier for the purpose - NS Modular with one of the front-end options:
NS Modular Home
Your 2sc2922/2sa1216 will fit perfectly into the project.
Look at X4 VFA front-end.
Let me and/or Jeff (jwilhelm) know if you will have some questions.
We provide full support for the build.
Cheers,
Valery
Very good amplifier for the purpose - NS Modular with one of the front-end options:
NS Modular Home
Your 2sc2922/2sa1216 will fit perfectly into the project.
Look at X4 VFA front-end.
Let me and/or Jeff (jwilhelm) know if you will have some questions.
We provide full support for the build.
Cheers,
Valery
Dear Valery,
Looks like this is exact what I am looking for.
Just want to ask about few moments:
How such amplifier feels with 6 ohm speakers, which I will use before I found something more interesting,
Can out be connected to 59-60 volts power supply, I have 42 v transformer with enough power and it will be great it if I can use use it, instead of buying other one, and the last question, what if output transistors will be connected to board with wires, there is not enough place for whole pcb, but if connect transistors with wires, I can put just 3 transistors to one heatsink, as I have 4, the temperature will be much better in this case.
Hi,
No problem with 6 ohm speaker - that's actually what I tested the first prototype of the output stage with - 6 ohm Monitor Audio RS-8 speakers.
Later on, NS Modular was tested with 4 ohm and even 2 ohm loads, driving up to 600W into 2 ohm during short period of time (the build was not ready for that kind of power handling during long time). We actually abused the test boards in many different ways - they are really difficult to break 🙂
+/-60V rails are fine - we tested the board in the range from +/-50V to +/-70V DC.
That will allow up to around 180W @ 8 ohm or 240W @ 6 ohm.
Connecting the output transistors with the wires is fine - one of the builders did it successfully. Of course, we recommend to use the wires fat enough as well as short enough. Can you please drop a photo of your heatsinks configuration - we will try to come up with some recommendations.
Also - look at the control boards - DC offset, over-current and temperature sensing circuits are integrated into the amplifier boards now for easy interaction with our micro-controller based soft-start / protection boards.
Cheers,
Valery
No problem with 6 ohm speaker - that's actually what I tested the first prototype of the output stage with - 6 ohm Monitor Audio RS-8 speakers.
Later on, NS Modular was tested with 4 ohm and even 2 ohm loads, driving up to 600W into 2 ohm during short period of time (the build was not ready for that kind of power handling during long time). We actually abused the test boards in many different ways - they are really difficult to break 🙂
+/-60V rails are fine - we tested the board in the range from +/-50V to +/-70V DC.
That will allow up to around 180W @ 8 ohm or 240W @ 6 ohm.
Connecting the output transistors with the wires is fine - one of the builders did it successfully. Of course, we recommend to use the wires fat enough as well as short enough. Can you please drop a photo of your heatsinks configuration - we will try to come up with some recommendations.
Also - look at the control boards - DC offset, over-current and temperature sensing circuits are integrated into the amplifier boards now for easy interaction with our micro-controller based soft-start / protection boards.
Cheers,
Valery
- Status
- Not open for further replies.