hi grege, thanks for your help. i was wanting to try to match the mje15045/mje1504 drivers i'm not sure if this is the input transistors you are refering to or maybe, i need to be looking for pre drivers. also, at my amp input, i have two op amps ad8610s i think one is being used as a buffer. i have no schematic so that makes things worse since i'm no tech. when i say match, i mean match the two mje15035s with each other and, the two mje15034s with each other. for the quiescent current, does that mean the mjl4281a should get about 50 ma. and, the mjl4302 should also get about 50 ma meaning 100 ma. total for that channel? and the same for the other channel? thanks again, crippledchicken 
hi crippledchicken,
Sorry if I confused the issue. I seem to be out of step with the other posters on this issue, so I hope I'm not misunderstanding something.
Matching transistors to me, means picking transistors that have the same paramenters, hfe for example. This requires a large number of transistors to start with, and measuring them until you find some near identical ones. I now realise you just mean setting the quiescent current the same.
The input pair are the transistors of the input stage. I assumed that your amp has them as it is fairly common. The ad8610s MAY have been used as an alternative. Without the scehmatics its a bit hard to tell. So, in my earlier post I was trying to say, it is more important to match the input pair than your output transistors.
Have you confirmed your amp is EF topology?
The talk of quiescent current still confuses me as I understand it is not important as it is only the result of setting the Vq to the right value. Vq is the important. Iq is just a result of the value of the emitter resistors, Vq and ohms law.
This is how I would set Vq for an EF amp.
1. set DMM to mV
2. attach probes across both emitter resistors
3. adjust to get reading of roughly 46.2 mV
4. allow amp to warm up and repeat step 3.
5. repeat 4 until you get a nice stable reading.
In all honestly, you may not notice a difference betwen 23mV and 46mV so the lower value may be better for your heatsinks.
Sorry if I confused the issue.
I seem to be out of step with the other posters on this issue, so I hope I'm not misunderstanding something.Matching transistors to me, means picking transistors that have the same paramenters, hfe for example. This requires a large number of transistors to start with, and measuring them until you find some near identical ones. I now realise you just mean setting the quiescent current the same.
The input pair are the transistors of the input stage. I assumed that your amp has them as it is fairly common. The ad8610s MAY have been used as an alternative. Without the scehmatics its a bit hard to tell. So, in my earlier post I was trying to say, it is more important to match the input pair than your output transistors.
Have you confirmed your amp is EF topology?
The talk of quiescent current still confuses me as I understand it is not important as it is only the result of setting the Vq to the right value. Vq is the important. Iq is just a result of the value of the emitter resistors, Vq and ohms law.
This is how I would set Vq for an EF amp.
1. set DMM to mV
2. attach probes across both emitter resistors
3. adjust to get reading of roughly 46.2 mV
4. allow amp to warm up and repeat step 3.
5. repeat 4 until you get a nice stable reading.
In all honestly, you may not notice a difference betwen 23mV and 46mV so the lower value may be better for your heatsinks.
ah, i'll run it at 23 mv. across both emmiter resistors for awhile and then, try the 46 mv. and try to listen for a difference. i'll let you know the outcome and thanks again! crippledchicken ps. i'm not sure what you mean by EF amp?grege said:hi crippledchicken,
Sorry if I confused the issue.
Matching transistors to me, means picking transistors that have the same paramenters, hfe for example. This requires a large number of transistors to start with, and measuring them until you find some near identical ones. I now realise you just mean setting the quiescent current the same.
The input pair are the transistors of the input stage. I assumed that your amp has them as it is fairly common. The ad8610s MAY have been used as an alternative. Without the scehmatics its a bit hard to tell. So, in my earlier post I was trying to say, it is more important to match the input pair than your output transistors.
Have you confirmed your amp is EF topology?
The talk of quiescent current still confuses me as I understand it is not important as it is only the result of setting the Vq to the right value. Vq is the important. Iq is just a result of the value of the emitter resistors, Vq and ohms law.
This is how I would set Vq for an EF amp.
1. set DMM to mV
2. attach probes across both emitter resistors
3. adjust to get reading of roughly 46.2 mV
4. allow amp to warm up and repeat step 3.
5. repeat 4 until you get a nice stable reading.
In all honestly, you may not notice a difference betwen 23mV and 46mV so the lower value may be better for your heatsinks.
THANKS richieooboy i'm reading elliott sounds projects about amps trying to learn more about the different topoligys used. wish i could have gotten into this hobby years ago when i was younger it's very interesting indeed. thanks for clearing that up for me. crippledchickenrichie00boy said:
CFP is usually taken to mean complementary feedback pair, rather than compound. They are also commonly called Sziklai pairs.
You should note that the most common output topology is not just an emitter-follower, but a Darlington pair, which is a specific type of emitter-follower. Technically a normal CFP output stage is an emitter-follower too, so it's best to call output stages Darlington or CFP rather than EF or CFP.
You should note that the most common output topology is not just an emitter-follower, but a Darlington pair, which is a specific type of emitter-follower. Technically a normal CFP output stage is an emitter-follower too, so it's best to call output stages Darlington or CFP rather than EF or CFP.
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