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Old 10th August 2010, 07:18 PM   #271
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Good point Wahab. Others say the CCS is audible and that is why I'm investigating. It's probably of little significance. However a weak CCS will disrupt LTP balance at HF and cause phase shifted LTP currents.

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Old 10th August 2010, 07:30 PM   #272
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I really would like to use this CCS on my experimental board ,the FX , which already has a super pair. (below)
Try it , you will like..

Quote:
By wahab - The question is rather what is the real importance of a CCS
as a THD source..

THD for a classical CCS implemented with a bjt and a voltage
reference is in the order of a few ppm, while the distorsion
due to the VAS itself is about 1 % and soaring with high
voltages swings...
I am not leaving these factors any room with those 2 cap multipliers on the pb250 , RIPPLE is the enemy !

OS
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File Type: zip mongrel_FX1.0.zip (7.8 KB, 56 views)
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Last edited by ostripper; 10th August 2010 at 07:35 PM.
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Old 10th August 2010, 08:05 PM   #273
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Quote:
Originally Posted by keantoken View Post
Good point Wahab. Others say the CCS is audible and that is why I'm investigating. It's probably of little significance. However a weak CCS will disrupt LTP balance at HF and cause phase shifted LTP currents.

- keantoken
indeed it is audible if designed this way :

Dx Blame ST - Builder's thread - post pictures, reviews and comments here please.
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Old 10th August 2010, 08:11 PM   #274
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Quote:
Originally Posted by wahab View Post
Ha , HA ... "Designed" might be an improper term in this case. Carlos should of used 2 current sources like the AX.. 1/10th the distortion (I simmed his )

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Old 10th August 2010, 08:14 PM   #275
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Ostripper, quiet you. That is a schematic from Doug Self's book! Carlos's amp uses a bootstrap, if you look at the beginning of that thread.

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Old 10th August 2010, 08:14 PM   #276
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Quote:
Originally Posted by keantoken View Post
Good point Wahab. Others say the CCS is audible and that is why I'm investigating. It's probably of little significance. However a weak CCS will disrupt LTP balance at HF and cause phase shifted LTP currents.

- keantoken

I have noticed that the LTP balance actually gets better up and beyond 10Khz with the 2 tranny CCS's .. very noticable on the AX and CX.
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Old 10th August 2010, 08:16 PM   #277
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Quote:
Originally Posted by keantoken View Post
Ostripper, quiet you. That is a schematic from Doug Self's book! Carlos's amp uses a bootstrap, if you look at the beginning of that thread.

- keantoken
But he has the other one too , without the bootstrap. 100pF miller and all.
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Old 10th August 2010, 08:30 PM   #278
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Okay, I digress, the LTP of Carlos's amp uses a weak CCS.

For some reason the AC impedance of the voodoo CCS is the same as the two-Q version, in spite of the much lower DC impedance. This I do not understand.

Wait a sec - Ah! Ostripper, your KSC3503 model is botched I think... Try this one:

.MODEL SC3503 NPN IS=7.010E-13 BF=156.09 VAF=600 IKF=0.12325 ISE=1.2538E-14 NE=1.5 BR=0.64499 VAR=100 IKR=0.05102 ISC=6.4644E-09 NC=1.5 RE=0.108 RC=1.215 RB=12.134 RBM=0.034 IRB=3.0e-6 CJE=7.10E-12 CJC=8.20E-12 TF=7.025E-10 XTF=2 VTF=35 ITF=1 TR=1.0E-8 EG=0.76 XTB=1.5 FC=0.5

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Old 10th August 2010, 08:39 PM   #279
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Quote:
Originally Posted by keantoken View Post
Okay, I digress, the LTP of Carlos's amp uses a weak CCS.

For some reason the AC impedance of the voodoo CCS is the same as the two-Q version, in spite of the much lower DC impedance. This I do not understand.

Wait a sec - Ah! Ostripper, your KSC3503 model is botched I think... Try this one:

.MODEL SC3503 NPN IS=7.010E-13 BF=156.09 VAF=600 IKF=0.12325 ISE=1.2538E-14 NE=1.5 BR=0.64499 VAR=100 IKR=0.05102 ISC=6.4644E-09 NC=1.5 RE=0.108 RC=1.215 RB=12.134 RBM=0.034 IRB=3.0e-6 CJE=7.10E-12 CJC=8.20E-12 TF=7.025E-10 XTF=2 VTF=35 ITF=1 TR=1.0E-8 EG=0.76 XTB=1.5 FC=0.5

- keantoken
"Botched" it is the genuine fairchild model. I put yours in , no difference.

Back to the topic of CCS's , it is alright to "share" the LED or diode referenced CCS's between LTP and VAS (my "supersym" has a RED LED CCS), but they are rather low performance to begin with. The 2 transistor ones work best alone since they are based on the gain of the transistors rather than an external referance.


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Last edited by ostripper; 10th August 2010 at 08:47 PM.
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Old 10th August 2010, 08:58 PM   #280
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A question , Keen. Why do you use LT instead of multisim or microcap. And do you believe all models are created equal.

I have noticed that the newer models along with LT can simulate problems (oscillation , saturation) MUCH more reliably. I have multisim and it is too easy(optimistic). Where a circuit WILL work in multisim , sometimes it will not work or oscillate in LT. Could it be that LT's output is a more realistic representation of the real world ???
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