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In Reply to: Re: I challenge you to publish your measurents of that rolloff! posted by fatbottle on September 30, 2004 at 01:40:41:
> I'll make a guess , 15Hz-20kHzI'm not interested in your guess and neither are other innocent readers that might mistaken you for an "authority" on the subject.
Try 12Hz to 80KHz at 10 watts into 8 ohm, which I measured on the particular amp only a few weeks ago with a real scope and signal generator. Not only fresh in my memory, but also written on real paper.> The coupling caps are too small for a start
Too small? Your own "guess" was 15 Hz on the low side, what's too small in that?!
By the way, the math fully agrees with you and with the measured bass rolloff. 47K plate load plus 100K grid/bias load in series with 0.1uF yields a rolloff at 11 Hz. I measured 12Hz!> Anecdotal evidence is all you have so far , so get your scope out and try to prove me wrong !
Sorry to disappoint you.
The scope was out and all my quotes are from REAL MEASUREMNENTS.
Perhaps you should get your scope out and be more careful to not mislead people with blank statements about something you don't know for sure and apparently someone else does.
There is no anecdote or guess in my statements - all HARD EVIDENCE. So, I'm asking again - where are YOUR REAL MEASUREMENTS?If you neglect to measure, at least offer a theoretical analysis of some sort. If you can't do that, then offer us circuit simulation results. Takes only a few minutes to simulate my circuit on HSPICE (which I did!).
I have nothing against your cascode diff amps but I have a lot against your blank statements with nothing behind them regading my circuit. If you had measured it or listened to it and then debate facts, I might have paid more attention. So far all I hear is "your guess"!
Do you have any clue how many engineering projects fail because someone guesses instead of doing the job right?!
Sorry, not interested!
Follow Ups:
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...FB
Hello ,
Temper , temper . Remember deep breathes and count to then then breathe out slowly . 12Hz is still piss-poor LF response and will impact into the audio band but if you're happy with it , up to you and your ego . It has been a pleasure disscussing such a great design with such huge claimed bandwidth , it must be the work of a true genius , surely a manufacturer will incorporate it into their designs . Never realised just how fantastic a 12AT7 running at 2mA per section could sound . All my experience into concertina stages is completely wrong and I had better get my ears syringed .Happy trolling !
ps I would still like to see the 'HARD EVIDENCE' which contradicts with my own findings . You ask me for evidence , I'll have to find my old notebooks which have the results in . You have the amp already so perhaps to provide convincing (instead of anecdotal) proof , any chance of a picture of a scope trace of 500kHz sinewaves or 10kHz squarewaves ? Thanks !
In the coarse of a constructive discussion I will accept all sorts of critique and suggestions, but that's not what you are conducting here.
You just continue to post misleading general opinions as "facts".
You may have general experience with this type of circuit but at some point it's time to stop waiving your hands and be more specific. While I built this circuit and listened to the modified amp and posted specific data, you continue with unfounded "facts" - anecdotes...
Since all that "blurry" talk makes me look like someone who has no clue what he's doing and the (proven) mod as incompetent, what could I do but set things straight?I just wanted to clarify that issue to other readers.
It is legitimate for you to say "it's my experience" or "it's my opinion", but going on and on with blank claims and dismissing all my data, just because it suits your pre-conceived general opinion?
Then you tell me "Anecdotal evidence is all you have so far", refering to my actual measurements? Why?!
If you submit repeated hard accusations you better have irrefutable evidence, Counsellor!You can review my simulations (below). Please don't post that it's all wrong without serious data!
You want scope pics? You'll dispute anything I say anyway, so it's best that you take them yourself (with my specific circuit please).
After you review that data against my claims, I believe an apology would seem quite appropriate.
Hello ,
It's amazing just how misleading these simulations can be . Quite frankly I don't believe the graphics provided (anyone could do this in MSPaint) . Please supply some shots of some scope traces . What about the distortion ? Surely you can provide a shot of a (non-simulated) spectrum analyser sweep , can't you ? I'll believe you then ;) I'm very interested in 12AT7's , after all I have 700 of them . If your circuit performs as specified , I'd love to press a few into service . Not really a fave of mine at the I'm afraid . It was the same with E88CC's until I tried Allen Wrights circuits . Convince me or stop all this bull
cheers
How predictable...
Since we don't have any baseline rules, what's exactly the point you're trying to make in asking for more data?
Hello ,
There is no need to get defensive and no I'm not prepared to build one . The bench is already taken up with a PP GM70 amp , no more room ! Scope traces perhaps will settle this ? I thought you had access to distortion measuring equipment also ? You have a digital camera and you say you have a scope . Off you go , I'm easily pleased . Looking forward to seeing the pictures :)cheers
Given your ever argumentative suspicion, how will I ever be able to prove to you that the pics are not taken directly from my signal generator?
As we both know, anybody that has a scope and a digi cam can do that, especially if he's profficient in MSPaint... :-)
(You got a chuckle out of me on that one...)
It's a futile exercise. Just take my word for it...
Never mind , I'll leave you to your simulations . Just make sure you use a scope and sig gen to take your measurements next time .
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