A series RC circuit is, in principle, the same even if it is reversed. However, the actual part generally has a larger surface area for the Cap. In the case of a feedback circuit, if the Cap is on the inverting input side, it will easily pick up signals and noise from other circuit. In the case of Zobel, on the contrary, it acts as a "transmitting antenna" and can spread the signal to other parts. Usually, a film cap is often used there, and the surface area becomes large.
Experienced designers such as Cordell and Self make Cap the ground side as a consideration to prevent such problems.
In most cases, I think that it is rare that either of them causes actual harm, but I think it is desirable to make a habit of setting Cap to the ground side.
However, in the case of this Venomoose, the cap seems to use a small ceramic, so I can't say which one is better. 🤔
Omitting the LPF on the input is not a good idea. Please refer to my previous post and know that there are other important functions besides LPF.
https://www.diyaudio.com/community/...in-of-an-amplifier.137436/page-7#post-7164930
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It might be the reason as to why I can't even pass the DC test. In my post#40 the VAS stage transistor Q7 is heating up so much it smokes. I suspect the IPS is trying to drive it a lot. Perhaps it has something to do with not having an LPF in the input? I got the circuit simplified for now.
I don't know the cause of the abnormal fever in Q7. Oscillation of the major loop usually generates a lot of heat in the OPS.
Are there any simple implementation mistakes?
Are there any simple implementation mistakes?
None, I think so. preivously I got the oritentation of D4 when I was placing components on the actual PCB, I powered it up and R8 smoked then fried. While troubleshooting for that, I think there was a time I saw D11 smoked and Q11 and Q13 became really hot.
So so far the reason as to why the VAS Q7 is heating up is because I may have destroyed some components.
I can't chack the voltage at the base of Q7 anyway cause it is really getting hot quick. I might have to desolder then replace all the components for sure.
oh and, no heat so far in the at the output stage, It seesms the output transistors are not even turning on, really cold to the touch so the problem seems to be on the VAS section
update, I replaced most of the components in the input and vas stages. This time, Q7 is still heating excessively and the input stage, I am also picking up heat from them, most is from R4 and R5. So the problem is pretty much in the IPS and VAS
You might want to measure the voltages across some of the resistors in LT Spice and compare them to your build to try to isolate where the problem is coming from.
Its a bit tricky to measure specific current with the circuit in PCB. I'll just measure voltages
and work out th current from there. Gotta be quick though.
Unfortunately, I really cant get it to work. I first replaced the transistors as well as the LED bias for the current sources. I measured the voltages and they are everywhere. Like for the differential pair Q1 and Q2, about 3V+ is measured at its base while Q2's base is a about 2.6V. Bases of the current mirror is about 14V, same with Q7. And furthermore, I am getting a whopping +6V-ish DC voltage at the output terminal despite not adding any input signal to Q1, I do not even feel any heat coming from the output transistors U1 and U2.
There's a lot of things messed up. I must redo the whole thing from the start 😢. I even ran out of replacement parts and have to resort to series 100ohm for R8. As seen in the picture, things are getting fried in the IPS and VAS stages.
There's a lot of things messed up. I must redo the whole thing from the start 😢. I even ran out of replacement parts and have to resort to series 100ohm for R8. As seen in the picture, things are getting fried in the IPS and VAS stages.
UTC 2N5401/2N5551 seems to have EBC type and ECB type pin assignments. It’s OK? ?
https://akizukidenshi.com/download/ds/unisonic/2n5401.pdf
https://akizukidenshi.com/download/ds/unisonic/2n5551.pdf
https://akizukidenshi.com/download/ds/unisonic/2n5401.pdf
https://akizukidenshi.com/download/ds/unisonic/2n5551.pdf
I've checked the transistors pins using a diode tester before soldering, both the 2N5401 as well as 2N5551 have EBC pin assignments
If you need a good reference for building 3 stage amplifier, I would recommend getting Audio Power Amplifier Design by Douglas Self.
Yeah, I got their books, that's where I did my readings even where most of the design came from. If you would notice, the small signal transistors are the same from what was shown in Cordell's book, 2N5551 and 2N5401.
Also, I found another great reference, https://sound-au.com/index.html
But, I am not discouraged though, I would re-do the project.
You've posted your schematics multiple times, each time with different reference numbers or different circuits without your having to point it out. It confuses the viewer.
Looking at the boards so far, the emitters of driver Tr Q11 and Q13 both face outward. So Q11 and Q13 should be oriented in opposite directions, but in the photo they are oriented the same way. Are either directions wrong? (probably Q11)
Looking at the boards so far, the emitters of driver Tr Q11 and Q13 both face outward. So Q11 and Q13 should be oriented in opposite directions, but in the photo they are oriented the same way. Are either directions wrong? (probably Q11)