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Old 3rd December 2011, 10:52 PM   #501
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The Capacitance of the G1 of 6SN7 is--7pf according to data sheet. The additional is a guess, but wouldnt be far out IMO...

--Close enough for 'Audio' work anyway!
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Old 3rd December 2011, 10:55 PM   #502
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by Alastair E View Post
The Capacitance of the G1 of 6SN7 is--7pf according to data sheet. The additional is a guess, but wouldnt be far out IMO...

--Close enough for 'Audio' work anyway!
Can I get a data sheet for the lottery numbers? thats not far out...LOL


I'll go with 10K...and see what happens..


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M. Gregg
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Old 3rd December 2011, 11:12 PM   #503
M Gregg is offline M Gregg  United Kingdom
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Just for fun post..

Capacitive Reactance Theory

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Old 3rd December 2011, 11:19 PM   #504
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Thanks for the input Alastair! I totally see what you are doing and will continue to follow this thread. I am still going through with the Tim Mellow but what I will do is to make your input-driver stage interchangable with the Tim Mellow circuit... as an assembly. That would allow some easy comparisons.

Thanks,
Mark
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Old 3rd December 2011, 11:32 PM   #505
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I will try using a direct connection...and see what happens.

I think you suggested 10K..I have seen some other schematics with a direct "no resistance connection"..what value do you use in your amps?

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M. Gregg
I suggested 10K or lower , I usualy 1k - 2,2 K . By the way the data of 6SN7 gives 2,2 - 2,6 pF input capacitance . Here is my post number 442 - Well , I talk about input capacitance of the 6SN7 and not about input impedance , in this circuit the 470KΩ resistor with the input capacitance of the 6SN7 Cgk wich is 3pF plus the capacitance of the tube socket plus the capacitance of the circuitry , makes an RC filter wich its cutoff frequency is from 42,5Khz to 56Khz ( Fc = 1/ 2 * pi* R * C ), remember that the output impedance of the previous stage will added to this resistance and then the cutoff frequency will be smaller , so there is no need to lower the frequency of the amp ( in open loop ) that much .With a more powerfull tube , I didn't mean output power tube , maby the use of low output power tube , and I say it only to reduce more the upper output ( anode ) impedance ( with smaller Ra and Rk ) of the phase spliter to reduce the Miller effect of the output tubes , and have a better frequency response , and there is no need to drive the output tubes in classAB2 . Thanks Dim.

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Old 4th December 2011, 08:24 AM   #506
M Gregg is offline M Gregg  United Kingdom
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Just for interest,

Looking at this there should be an improvement with the change in input resistor.. Page 7 & 8 of this link ..put togeather..

http://www.kennethkuhn.com/students/...ve_testing.pdf

I have some components on order and will try it on the next strip..just for fun of course...

Run out of solder..LOL..solder sucker needs a new tip..

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M. Gregg
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Old 4th December 2011, 08:45 AM   #507
M Gregg is offline M Gregg  United Kingdom
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Just a reflective thought,

I have used a full 100gm roll of Cardas in this amp...I wonder what 100gm of wonder solder would sound like..LMAO...

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Old 4th December 2011, 12:48 PM   #508
cnpope is offline cnpope  United States
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Full 6c33c..

At 8/9/10/11/12V...I did manage 13V however the 1.6A T fuse blew..so no picks ...didn't want to try it again..drawing 1.7A
Again X10 probe so you have to multiply..


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M. Gregg
Just want to check I'm reading this correctly. You are getting a maximum of about 12V peak-to-peak, into 7.9 ohms? That would be about 2.8W continuous power. That seems pretty low. Are you sure about the voltages? You mentioned blowing a 1.6A fuse at 13V peak-to-peak, but that would be only 4.6V rms, which doesn't seem like it should be enough to blow the fuse.

Could something be wrong with your voltages?

Chris
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Old 4th December 2011, 02:10 PM   #509
cnpope is offline cnpope  United States
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Here are a couple of traces for the Tim Mellow OTL, with a 1KHz sinewave input, driving an 8 ohm resistive load. Scope is set on 10V per division. The first trace is just before clipping, and the second is when clipping is just beginning. A DVM across the load confirms about 14V rms (i.e. about 40V peak-to-peak) just before clipping. This implies about 25W continuous power just before clipping.

Chris
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Old 4th December 2011, 02:22 PM   #510
M Gregg is offline M Gregg  United Kingdom
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I agree something is not right,

Just looking at your wave on the scope..

I will have a look there is something strange...

If power is that low...it does not sound low...

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M. Gregg
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