CraigBuckingham said:
You are entitled to your opinion. It is just incorrect. I do not intend on wasting any more time with these claims that this does not work. It does. Get over it or go away.
I'm just (at the moment) a reader of the thread, having followed it from the start. Now having recently finished restoring a SS 70's pre and power amp, I have the time to build something and this amp intrigues me.
Steve I thank you for posting this design, Its refreshing to see a professional audio engineer present a worked out design in a way I can follow. I intend to layout and etch boards this being the spirit of DIY 🙂 though the misses is not so keen on etchant in the kitchen 😉
Building one though it may take a while. Other commitments may have to take precedence. Unfortunatly I do not have distortion measuring equipment, just an old scope, a soldering iron and a few meters, so I will not be able to report figures when done.
Thanks
Alan
Steve I thank you for posting this design, Its refreshing to see a professional audio engineer present a worked out design in a way I can follow. I intend to layout and etch boards this being the spirit of DIY 🙂 though the misses is not so keen on etchant in the kitchen 😉
Building one though it may take a while. Other commitments may have to take precedence. Unfortunatly I do not have distortion measuring equipment, just an old scope, a soldering iron and a few meters, so I will not be able to report figures when done.
Thanks
Alan
But not that voltage over that capacitor changes with signal right?
I guess "non switching" depends on where you draw the line between being off and on for the output devices.
I guess "non switching" depends on where you draw the line between being off and on for the output devices.
Steve Dunlap said:
By definition that means the circuit depends on hfe. You need to adjust it if hfe is different. I wouldn't do it that way but I'm not going to stop you 🙂
megajocke making a megajoke?
This statement was made immediately before stating the point about the dependency on hfe. In that context, the implication was made that the design was device intolerant and not robust. This is a negative slant when you consider the excellent adjustability built into this circuit. He even accounts for thermal drift! Which designs that we revere and build on this website are as forgiving about part selection and mismatching as this one?
Steve Dunlap said:
You match their hfe, or what?
megajocke said:
Criticizing is one thing, designing an ingenious SOTA audio amplifier is another thing.
nania said:
You are forgetting the overall context - that was a reply to CraigBuckingham who had quoted me in his post and stated the circuit had much more severe flaws than I believe it has. "Too device dependent for my taste" like I wrote is more positive than "D5-D7 is not biased correctly. R12 doesn't make sense", isn't it?
Joshua_G said:
I'm not the one criticizing. I earlier replied to CraigBuckingham but Steve replied to that post, thinking it meant something else than it did, so I had to try to explain what I meant, but I might have failed to do so.
See my previous post.
megajocke said:
Have you checked to see how a change in hfe over a range of 4 actually changes the bias? I have. I has a very small effect. At the currents involved here, the voltage change across the diodes varies very little.
I would not stop you either. If you like another way, that 's OK. There is no rule that says we do everything the same.
Joshua_G said:
I match hfe. I test and sort transistors (well I did) when they arrived. That makes building with matched transistors easier.
megajocke said:
I do not take your comments as criticism. I consider them a discussion. We may have different views on how we feel something should be achieved, but there is always room to discuss why we disagree.
megajocke said:
I am sorry if I misunderstood your meaning in that post. It seems to have been made clear now.
Steve,
That could be it. 🙂 It seems context is treated a little bit differently in english than my native language and this seems to make misunderstandings easy. Among other things, context seems to be "forgotten" faster than I expect normally.
Also there are the two different ways of looking at circuit operation: "current is driving force/voltage is a side effect" and "voltage is driving force/current is a side effect". Both are right, but the one you are not used to using yourself can be confusing.
But I think a lot of the misunderstandings are because many here thought you implied that the voltage over the capacitor had a signal component. Glen's, traderbam's and Craig's comments come to mind besides mine.
When Craig wrote "All of the talk about the OP bias section D5-D7, Q8, Q11 dynamic action is misplaced as C6 will clamp most of it. " I think he meant by "dynamic action" that there would have been some signal voltage over the capacitor.
Finally, I have a question: Did you measure how low current fell in the inactive side of the output stage?
Perhaps the "switching"/"non-switching" argument is just over semantics, like the discussion on whether non-switching is a form of class A or not in the other thread.
edit:
Those two last posts where not directed at you. I thought it was clear that "you" referred to Joshua_G and nania because I had quoted them. I'll try to be more clear in the future 🙂 Sorry for that!
That could be it. 🙂 It seems context is treated a little bit differently in english than my native language and this seems to make misunderstandings easy. Among other things, context seems to be "forgotten" faster than I expect normally.
Also there are the two different ways of looking at circuit operation: "current is driving force/voltage is a side effect" and "voltage is driving force/current is a side effect". Both are right, but the one you are not used to using yourself can be confusing.
But I think a lot of the misunderstandings are because many here thought you implied that the voltage over the capacitor had a signal component. Glen's, traderbam's and Craig's comments come to mind besides mine.
When Craig wrote "All of the talk about the OP bias section D5-D7, Q8, Q11 dynamic action is misplaced as C6 will clamp most of it. " I think he meant by "dynamic action" that there would have been some signal voltage over the capacitor.
Finally, I have a question: Did you measure how low current fell in the inactive side of the output stage?
Perhaps the "switching"/"non-switching" argument is just over semantics, like the discussion on whether non-switching is a form of class A or not in the other thread.
edit:
Those two last posts where not directed at you. I thought it was clear that "you" referred to Joshua_G and nania because I had quoted them. I'll try to be more clear in the future 🙂 Sorry for that!
For all that have problems with simulations (attached) is
.asc files of the OPS and the whole shabang. neither oscillate
in VR or real life, included is the text file with known
accurate models as well as andy c's sine generator .asc .
OS
.asc files of the OPS and the whole shabang. neither oscillate
in VR or real life, included is the text file with known
accurate models as well as andy c's sine generator .asc .
OS
Hi OS,
That sine generator is nothing special really, and it wasn't my creation. I copied the idea from someone else who posted it over in the SPICE thread. I can't remember who it was though. It was just easier to recreate it from scratch than to go through that long thread to find it.
That sine generator is nothing special really, and it wasn't my creation. I copied the idea from someone else who posted it over in the SPICE thread. I can't remember who it was though. It was just easier to recreate it from scratch than to go through that long thread to find it.
But it is really useful, as you can get a good idea (in %) of
what changes in compensation , balanced operation, etc.
have on the different distortion components.
instead of interpreting the FFT's.. Thanks.
OS
Steve Dunlap said:
I am not sure what you mean here Steve.
You said 'I'm not sure which schematic you are referring to. There is no X13."
To which I replied with the PDF document properties that referred to X13.
In my original post I also, in the same instance, referred to the output devices to save any abiguity for what seemed a typo.
Steve Dunlap said:
"Incorrect' is a very strong black and white sort of claim.
I didn't say "it didn't work" I used the words optimal or optimally or incorrectly for subcircuits of the amplifier.
Steve, I was just trying to present some objective constructive critique of the design. My reasoning for this was there were so many claims about what each section did or didn't do by so many members that I thought I would contribute to one of the many consensuses being devoloped.
I jumped to page 31 from page 5 seeing that those issue were still not resolved.
In my original post I had talked about the saturated bias circuit for the output stage biasing, but later edited out for risk of being too blunt. However some other very learned member chimed in with the same response so I added it back in.
I thought this was a discussion forum so I was contributing.
There are many ways of looking at what is said.
The stingingly guarded exchanges in this thread remind me of the 1956 movie Forbidden Planet. If this were Dr. Morbius' amplifier, perhaps he might have said:
"The fools, the meddling idiots! As though their ape's brains could contain the secrets of the Krill!"
"The fools, the meddling idiots! As though their ape's brains could contain the secrets of the Krill!"
- Status
- Not open for further replies.