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Old 27th August 2011, 10:01 PM   #181
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Quote:
Originally Posted by mickeymoose View Post
Elvee:
I looked for it in all these posts (179, I almost went blind), but could not find it:
The Circlophone produces about 20+ watts as shown in the current schematic. Changing the output power requires what changes to the circuit? I believe 25/50/100 watt versions would be of interest to the Circlophonites. Could you post suggestions to the parts value changes?
Thanks, E
I'm using about +-40V and I only had to change value of R21 and use higher Vceo for two small signal transistors. Others may have to use something other than BD139/40 And depending on the output transistors, use more of them.

I'm not sure of the power capabilities of mine but it is more than sufficient. I'm moving and have been packing and cleaning with it cranked right up.
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Old 28th August 2011, 10:46 AM   #182
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by mickeymoose View Post
Elvee:
I looked for it in all these posts (179, I almost went blind), but could not find it:
The Circlophone produces about 20+ watts as shown in the current schematic. Changing the output power requires what changes to the circuit? I believe 25/50/100 watt versions would be of interest to the Circlophonites. Could you post suggestions to the parts value changes?
Thanks, E
The output power is related to the supply voltages and the load impedance, in this case:

Po=(Vs-1.5)˛/(2*Rload)

With the 25V supplies of the example, this translates into ~34W on 8Ω, ~30W for practical purposes, 60W on 4Ω, 120W on 2Ω and 15W on 16Ω
  • For :

Po=25W Vs=22V R21=33K

Po=50W Vs=31V R21=47K

Po=100W Vs=42V R21=68K

  • For :

Po=25W Vs=17V R21=22K

Po=50W Vs=23V R21=33K

Po=100W Vs=32V R21=47K

All small signal transistors except Q13 must have a Vceo>Vs, all the other, including Q13 must have a Vceo>2*Vs.

The combination of output transistors + heatsink must be able to dissipate ~Po/2 with an acceptable temperature rise.
For the lowest power levels, account must be taken of the quiescent power, which is higher than for a standard class AB: ~200mA.
That translates into heatsinks of 9°C/W for 10W, and 1.5°C/W for 100W for example.

At higher power level, the SOAR of the transistors will be the limiting factor, rather than Pdmax or Rth.

Quote:
I'm using about +-40V and I only had to change value of R21 and use higher Vceo for two small signal transistors. Others may have to use something other than BD139/40 And depending on the output transistors, use more of them
That's about 90W for 8Ω
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Old 28th August 2011, 02:39 PM   #183
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Needs... more... circles...
Like a hole in the head.
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Old 28th August 2011, 04:12 PM   #184
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Single ended with the offset correction of an LTP:

Q2 is in a CFP, and operates at constant current.
Q1 sees low impedance tail strongly following Q2.
Q1 gets full amplification rather than usual half...
Q1 and Q2 balance at same current and voltage.

Go figure...

FFT shown at 1W 1KHz
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Last edited by kenpeter; 28th August 2011 at 04:14 PM.
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Old 28th August 2011, 04:32 PM   #185
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You see, I was screwin' with dis here one armed LTP.
Frustrated that currents did not automagically balance.
Something should be able to modulate the tail to fix that.

Now Q2 is held constant current by R19 and CFP loop.
Q1 is held similar average current by R7 and Noble loop.
Single ended result was complete unexpected accident.
Unexpected too was doubling of Q1's gain, probably why
the closed loop distortion went down so much as it did..

Was at least 10db worse H2 H3 before this new circle
began chasing its own tail.

C4 might not be needed. I just stuck it there cause it
looked "symmetrical". No thought process involved.

Last edited by kenpeter; 28th August 2011 at 04:43 PM.
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Old 28th August 2011, 04:44 PM   #186
Bigun is offline Bigun  Canada
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Kenpeter - I like it, simple and effective. At least in sims. Unfortunately, I don't understand how it works
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Old 28th August 2011, 05:47 PM   #187
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Whoa, thats weeeerd. C4 might be essential!
ACurrents in Q2 are much smaller than Q1 as expected, but phase shifted.
Wasn't planning, didn't want, and who invited a phase shift to this party?
I think this might be caused by compensation cap C3 in the Noble loop.

C4 definitely works to re-align push and pull phases in the LTP.
Aligns best at some value between 1200pf-1500pf, much higher than C3!?!
But why should this value be any different than C3? I don't get it...

---------

OK, I get it now... C3 sees VAS swing (Miller), C4 sees far less movement.

Last edited by kenpeter; 28th August 2011 at 06:00 PM.
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Old 28th August 2011, 07:18 PM   #188
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Other than thermal backbond and fuses, can't figure a benign
way to soft limit current into a shorted load.

Does the Noble loop relegate the other loops to Peon status?
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Last edited by kenpeter; 28th August 2011 at 07:22 PM.
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Old 28th August 2011, 09:42 PM   #189
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Messin to find ideal comp and junk... This 1W after reducing C2 to 33pF.
I'm guessin soft clip Zeners in parallel must have added a few picos?

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 4.040e+00 1.000e+00 -0.26° 0.00°
2 2.000e+03 4.856e-05 1.202e-05 -104.81° -104.55°
3 3.000e+03 9.788e-06 2.423e-06 2.27° 2.53°
4 4.000e+03 1.788e-07 4.425e-08 149.89° 150.15°
5 5.000e+03 6.531e-06 1.616e-06 179.04° 179.30°
6 6.000e+03 1.198e-07 2.965e-08 161.53° 161.79°
7 7.000e+03 4.024e-06 9.959e-07 -1.21° -0.96°
8 8.000e+03 7.927e-08 1.962e-08 -161.45° -161.19°
9 9.000e+03 2.339e-06 5.790e-07 178.96° 179.22°
Total Harmonic Distortion: 0.001242%

And this at +/-19.5V peaks, just under threshold of soft clipping:

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 1.914e+01 1.000e+00 -0.22° 0.00°
2 2.000e+03 1.367e-03 7.143e-05 -101.98° -101.75°
3 3.000e+03 8.989e-04 4.697e-05 3.44° 3.66°
4 4.000e+03 7.046e-05 3.682e-06 85.50° 85.72°
5 5.000e+03 6.071e-04 3.172e-05 178.42° 178.64°
6 6.000e+03 6.539e-06 3.417e-07 56.44° 56.66°
7 7.000e+03 4.896e-04 2.558e-05 -2.90° -2.68°
8 8.000e+03 3.884e-06 2.030e-07 -108.80° -108.58°
9 9.000e+03 3.726e-04 1.947e-05 176.43° 176.65°
Total Harmonic Distortion: 0.009676%

And C4 is 1000pf right now too. Allowin' just a little shift seemed to
reduce simulated distortion. Again, its a mystery to me why a phase
shift across the LTP would do anything beneficial???

Last edited by kenpeter; 28th August 2011 at 10:00 PM.
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Old 29th August 2011, 08:12 AM   #190
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Quote:
Originally Posted by kenpeter View Post
Needs... more... circles...Like a hole in the head.

Dear all,
please remind me how to use asc file to get from it working schematic in ltspice, my ltspice reads it as txt file
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Last edited by padamiecki; 29th August 2011 at 08:26 AM.
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