|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
205.238.183.48
In Reply to: RE: One last try at convincing you ... posted by Naz on October 23, 2014 at 06:13:54
Is your model for the 12AT7 freely available? I'd like to compare it to mine.
--------------------------
Buy Chinese. Bury freedom.
Follow Ups:
Here it is but any tube will exhibit similar characteristics after optimising and equalising the operating points. Incidentally, I would have liked to see higher idle current through the 12AT7 in both scenarios but I didn't want to throw another variable into the mix for the purpose of the exercise.
.SUBCKT 12AT7_ECC81 A G K
XV1 A G K TRIODENH
+PARAMS: LIP= 1 LIF= 0.0037 RAF= 0.09869 RAS= 1 CDO=-0.5
+ RAP= 0.1 ERP= 1.4
+ MU0= 45.093 MUR= 0.012937 EMC= 0.00000863
+ GCO=-0.5 GCF= 0.00012
+ CGA=1.60E-12 CGK=2.30E-12 CAK=4.00E-13
.ENDS
Naz
OK, we're using the same tube model, it's the one from the Duncan Amps Website.Being as this discussion seems to be centering on distortion, gain and output swing, I'll elaborate on my previous points in this regard. However, I want to stress that I consider the choke-loaded totem pole that you've introduced into the discussion a kludge. I've stated why already, but you've failed to acknowledge the points I made in any meaningful way, even after I posted a SPICE analysis showing the horrendously distorted currents within the tubes.
After creating the image below, I took a last look at your latest post and realized it's not quite the same as what we were discussing. I regret not noticing that sooner, but I'm already spending too much time on this. I won't sim it again for the sake of a minor variation, so we'll have to make do. Below are the circuits I tested, with text under each describing the results I saw, plus FFT plots. I've also posted the internal currents again, including those of the standard totem pole, for comparison.
Clearly, the choke loaded circuit isn't responding for me in the way you describe it, other than exhibiting more gain. Nevertheless, it is what it is. Given these results, I'll never use it, and I have no intention of discussing the circuit ad nauseum for no purpose. Of course, if you can address the non-linear currents within the triodes in a way that demonstrates this characteristic to be a trick of the simulation, a ghost, an anomaly that doesn't truly exist, I will reconsider. Absent that, I don't see any reason to continue this discussion.
Choke-loaded totem pole at 1V RMS input:
Standard totem pole at 1V RMS input:
Internal Currents - Choke-Loaded Totem Pole:
Internal Currents - Standard Totem Pole:
--------------------------
Buy Chinese. Bury freedom.
Edits: 10/23/14
TK, you keep ignoring what I'm saying.
Also, for a guy who attacks others for their beliefs on what they hear Vs what can be verified technically I find your "kludge" statement attacking a circuit which is both technically superior and better sounding extraordinary. You haven't built or listened to the choke loaded variation whereas I have built, tested and Simmed most possible variations of the "Totem Pole" circuit.
I will summarise one last time.
The choke loaded circuit has more than twice the gain so comparing both on the basis of an identical input signal as opposed to output is clearly ridiculous, especially since the input signal is on the point of overloading the choke loaded circuit.
The compromises in the simple mods I made to the original circuit provided other benefits. However, since this became an argument over topology I Simmed both circuits and levelled the playing field by optimising the values for a fair and direct comparison.
You are not the only one who hasn't the time for an endless and pointless argument over this but I want to ensure that the message would not be lost on anyone following this thread as to which variation of the circuit is technically best. As for sound, anyone can form their own view, I can only provide my opinion.
Finally, can you not see the glaring error in your SIM depicting my mods? Does the total current through the tubes not provide some clue? It's obvious that you have not included any resistance in your choke. Sorry, my bad in using the resistance of a real world Hammond choke of 1666 ohms without pointing it out.
Frankly, I don't care what you personally think of the circuit as long as it's for good and real reasons but you've shown neither so far! Further, to suggest that I've somehow tampered with the Sim to provide the result I want is a personal affront to my integrity ... I thought you were better than that.
My last word on the subject is an attached link to the ASC files so you and others can verify my Sims. Dave Slagle was always big on posting the ASCs and made it easy for us on his Web site. I should have headed his good advice and posted the damn things in the first place.
Naz
It's clear that you want validation for this circuit, and because I'm not giving it to you, I am now your target for personal attacks. I don't disagree with everything you've said, but we're not going to discuss this further. I'm done with it.
--------------------------
Buy Chinese. Bury freedom.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: