Scott
I trust your formulas are correct actually both fomulas are correct yours are more accurate. I had access to Aiken's formula when I did the RkCk chart but I did not consider cathode output impedance because I couldn't measure it at the time. You can only get these values from the tube data sheets. And, as we discussed, the values will vary depending on the tube and manufacturer. Look them up in the RCA/GE/Sylvania manuals. The values in the manuals are averages and at the time we were using JJ's no tube data, If you want to consider cathode impdiance we would have needed to use an average of the three manuals at a minimum. If they don't vary greatly you can just pick one for your calculations. Otherwise, do the math. Calculating Rk//Rk' is not hard. Basically, it's two resistors in parallel.
non-HRM Findings
Moderators: pompeiisneaks, Colossal
Re: non-HRM Findings
Scott, given the assertiveness of your post, I suspect you may have conducted spectrum analyzer tests to assess the accuracy of formulae, Aiken's or any others', correlating theory to real world phenomema. I have never done that myself, so I'd love to see any results you may have. Personally, because of the work I have been doing for so long, I am usually confident with most of the statements I make about real world vs mathematical abstractions, but I am always prepared to learn something new! Looking forward to some screen shots from you, if you have any.dogears wrote:Well, wrong is wrong..... If you look at he knee of a 1uf on CL2 both ways, it is almost an octave. Very noticeable in the real world, hence way wrong.....
Cheers,
Gil
Re: non-HRM Findings
Geez guys.... Tony posted a chart with values that corroborate what I am saying. (Where did you get the chart btw??) There are not two different formulas. Just that in a bypassed tube stage, you use Rk' and not Rk. No need for tube data sheets (using standard internal plate resistances and mu is fine...much better than ignoring their existance). You get Rk' from available values specific to the circuit. If there is no significant difference, we may as well change the spreadsheet to show values that can be off by an octave.
And yes, in the real world you most definately can hear going from a 1uf to a 2uf on Cl2.
Don't shoot me because I have pet peeve for accuracy.....
All is well that ends well since Gil posted the killer spreadsheet that has Rk' in it!! Now you can get much closer approximations so this is all moot.
And yes, in the real world you most definately can hear going from a 1uf to a 2uf on Cl2.
Don't shoot me because I have pet peeve for accuracy.....
All is well that ends well since Gil posted the killer spreadsheet that has Rk' in it!! Now you can get much closer approximations so this is all moot.
Last edited by dogears on Sat Nov 10, 2007 6:48 pm, edited 2 times in total.
Re: non-HRM Findings
Gil,
Our numbers agree. I agree with your calculations. They are correct from a theoretical point of view. Do you not agree that there is zero value to leave out Rk' as the results are not correct? Why bother if the numbers are wrong. Kind of like weighing yourself on a scale that could be off by more than 50%......
If you calculate the knee of CL2 due to bypass cap, 100K plate, 1.5K Rk, and 1uf bypass, you get either 100hz using just Rk or 170hz using Rk'. That is 70% higher and well into the guitar fundamental range.
Our numbers agree. I agree with your calculations. They are correct from a theoretical point of view. Do you not agree that there is zero value to leave out Rk' as the results are not correct? Why bother if the numbers are wrong. Kind of like weighing yourself on a scale that could be off by more than 50%......
If you calculate the knee of CL2 due to bypass cap, 100K plate, 1.5K Rk, and 1uf bypass, you get either 100hz using just Rk or 170hz using Rk'. That is 70% higher and well into the guitar fundamental range.
ayan wrote:Scott, given the assertiveness of your post, I suspect you may have conducted spectrum analyzer tests to assess the accuracy of formulae, Aiken's or any others', correlating theory to real world phenomema. I have never done that myself, so I'd love to see any results you may have. Personally, because of the work I have been doing for so long, I am usually confident with most of the statements I make about real world vs mathematical abstractions, but I am always prepared to learn something new! Looking forward to some screen shots from you, if you have any.dogears wrote:Well, wrong is wrong..... If you look at he knee of a 1uf on CL2 both ways, it is almost an octave. Very noticeable in the real world, hence way wrong.....
Cheers,
Gil
Re: non-HRM Findings
In my opinion Scott has a point! Maybe he came off a bit strong but the point is valid IHMO.
BTW I always use the formula/ spreadsheets to see if I am pounding too much bass of maybe too little into a next stage.
A good spreadsheet helps a lot in this case.
Have fun and Gil please let us know what you think sounds best, I'd love to read it.
Thanks,
Jelle
Maybe he came off a bit strong but the point is valid IHMO.BTW I always use the formula/ spreadsheets to see if I am pounding too much bass of maybe too little into a next stage.
A good spreadsheet helps a lot in this case.
Have fun and Gil please let us know what you think sounds best, I'd love to read it.
Thanks,
Jelle
Re: non-HRM Findings
Thanks Jelle...
I already apologized for my strong wording. I did not mean it in an aggressive way. I was trying to strongly persuade the other forumites reading here to not use the "light" version of the computation as it serves no purpose and in fact is misleading due to the margin of error.
Talbany is a friend and I hope he doesn't think I was attacking him... (I was't)
I already apologized for my strong wording. I did not mean it in an aggressive way. I was trying to strongly persuade the other forumites reading here to not use the "light" version of the computation as it serves no purpose and in fact is misleading due to the margin of error.
Talbany is a friend and I hope he doesn't think I was attacking him... (I was't)
Re: non-HRM Findings
Right, I think that's our phylosophical diffference, Scott.dogears wrote:Gil,
Do you not agree that there is zero value to leave out Rk' as the results are not correct? Why bother if the numbers are wrong. Kind of like weighing yourself on a scale that could be off by more than 50%......
Cheers,
Gil
Re: non-HRM Findings
You're welcome! I also wanted to point out that in the designing process these charts are REALLY helpfull.
BTW....Talbany: I love that voltage regulator in your amp...GREAT stuff!
BTW....Talbany: I love that voltage regulator in your amp...GREAT stuff!
Re: non-HRM Findings
Thanks its a cool mod
There are so many variables here that can obviously be factored in to get a more accurate #. Like buying a car that says this car gets 22 miles to the gallon but did they factor in wind resistance, ambient temp, Tire pressure, octane content of the fuel, gravity. ever changing properties. So how accurate is accurate. If you are really a stickler for this kind of thing better take a Variac to every gig. Gill I would also like to see your results.
There are so many variables here that can obviously be factored in to get a more accurate #. Like buying a car that says this car gets 22 miles to the gallon but did they factor in wind resistance, ambient temp, Tire pressure, octane content of the fuel, gravity. ever changing properties. So how accurate is accurate. If you are really a stickler for this kind of thing better take a Variac to every gig. Gill I would also like to see your results.
Last edited by talbany on Sat Nov 10, 2007 7:45 pm, edited 1 time in total.
Re: non-HRM Findings
As for the variac...I do! Kind of scary in a way because I can use it to increase the voltage too...I do not want to know what will happen when the line voltage comes back up a little bit. 
I do agree about the other factors but these charts do give great starting points but nothing more...Have you ever measured the value of a bunch of 1uF e-caps? They can be all over the place....
Anyway..have fun!
I do agree about the other factors but these charts do give great starting points but nothing more...Have you ever measured the value of a bunch of 1uF e-caps? They can be all over the place....
Anyway..have fun!
Re: non-HRM Findings
Me too! I use a voltage regulator in my rack.
Tony, so where did you get the chart? It agrees with what I am saying. Is that from some tube handbook??
I don't agree with your analogy about mpg. What I am saying is more like an 8 cylinder car has 8 cylinders and not 4. Although in the end, it doesn't matter as you are just driving the speedlimit, I would certainly refer to my engine in technically correct terms.
We can spar about it when you swing by here....
Tony, so where did you get the chart? It agrees with what I am saying. Is that from some tube handbook??
I don't agree with your analogy about mpg. What I am saying is more like an 8 cylinder car has 8 cylinders and not 4. Although in the end, it doesn't matter as you are just driving the speedlimit, I would certainly refer to my engine in technically correct terms.
We can spar about it when you swing by here....
Re: non-HRM Findings
Both my partner and I created it back several years when we were obsessed about createing the perfect amp. My partner Jim works for Nav Air designing underwater weapons systems, so he is big into the math. At one time we built what he thought was the perfect amp on paper from some Spitfire schem I think and the amp Totally SUCKED. We will revert back to some of the earlier data when run into a problem and we really don't do much prototyping any more. We've kind of migrated to the grip it and rip it school.
and yeah we have to hook up
Tony VVT
and yeah we have to hook up
Tony VVT
Re: non-HRM Findings
Oh
Thought I would post this. My favorite bypass caps are the silver spragues 5uf and 1 uf if you use them, smoother less gritty to my ears than the xicons or nicheons, a bit pricey but well worth it IMHO of coarse.
Tony
Thought I would post this. My favorite bypass caps are the silver spragues 5uf and 1 uf if you use them, smoother less gritty to my ears than the xicons or nicheons, a bit pricey but well worth it IMHO of coarse.
Tony
Re: non-HRM Findings
I have some of those silver ones too.... Big ass suckers....
Btw, I think we are all on the same page. I never would use math to design an amp. I think what Jelle and I are saying is that if after using your ears, you check what you did with math, use the correct formula. Can I get you to give in that you need to include Rk'? Pretty please?? LOL
Btw, I think we are all on the same page. I never would use math to design an amp. I think what Jelle and I are saying is that if after using your ears, you check what you did with math, use the correct formula. Can I get you to give in that you need to include Rk'? Pretty please?? LOL
Re: non-HRM Findings
NO WAY I am taking this one to my grave LOL.
Sure everyone should use the data to improve and better understand the amps functionality by all means.
The big guy did.
Id use it when I get an amp in or build one that has the grail tone like Gill said #124 had it ,but on the surface there was nothing special, maybe the answer lies in the numbers. I guess if you are lucky enough to run into enough of those amps, do the numbers on them catalogue it and try to find some sort of a pattern there. I think Dumble did this.
why else would he be scratching etches and writing down transformer specs, he had his own mathmatical recipe for his tone.
Scott I like Gill would love to see some real world analysis on your formulae or anything you see that might be worth posting. I will do the same.
Tony
LOL. Sure everyone should use the data to improve and better understand the amps functionality by all means.
The big guy did.
Id use it when I get an amp in or build one that has the grail tone like Gill said #124 had it ,but on the surface there was nothing special, maybe the answer lies in the numbers. I guess if you are lucky enough to run into enough of those amps, do the numbers on them catalogue it and try to find some sort of a pattern there. I think Dumble did this.
why else would he be scratching etches and writing down transformer specs, he had his own mathmatical recipe for his tone.
Scott I like Gill would love to see some real world analysis on your formulae or anything you see that might be worth posting. I will do the same.
Tony