this is the option too, Pioneer Super Linear Circuit, reaches power 2MHz:
https://www.diyaudio.com/community/threads/the-pioneer-super-linear-circuit.313163/
https://www.diyaudio.com/community/threads/the-pioneer-super-linear-circuit.313163/
here you have Pioneer circuit cascoded, RIAA correction should be ommited, with proper transistors you should get BW>2MHz
Thanks for all the leads: I'll have some work testing all of them, in isolation or combination.
Regarding the distortion of the input stage, in its environment, it is ~4ppm. A bit high to my taste, but a very minor contributor with my current options.
I don't intend to include everything in a GNFB, it would be too demanding. Having individual blocks with a low enough THD looks more sensible
Regarding the distortion of the input stage, in its environment, it is ~4ppm. A bit high to my taste, but a very minor contributor with my current options.
I don't intend to include everything in a GNFB, it would be too demanding. Having individual blocks with a low enough THD looks more sensible
It could be 50ohm; in fact an inverting topology with a 50R input resistor could eliminate a number of distortions, but I don't see how to implement it in an effective way
The Pioneer circuit seems to use regenerative bias on the input diamond, which is something I was going to suggest. I'm not sure how well it works at 1MHz? They also seem to be obsessed with reverse bias clamping diodes?
The simulations I did were a bit better without Q15, Q16. And a tiny bit better with bypass caps on R3,R4. Other things that I though should help had unexpected results.
And from the PG508, it helps to cross couple the folded cascodes, caps between R9 and R10, and between R1 and R2.
Thanx but I don't have models for BF469 and BF470. Perhaps I could sub BD139/140? It would be great if you could share your models.
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Hi, you can use any HF TO126 device with high enough VCE and low capacitance,
.MODEL BF469 NPN(IS=7.974E-15 ISE=2.266E-16 ISC=4.33E-12 XTI=3
- BF=122 BR=6.235 IKF=0.01029 IKR=0.02746 XTB=1.5
- VAF=25.51 VAR=19.43 VJE=0.4581 VJC=0.197
- RE=0.3814 RC=0.439 RB=1 RBM=0.5 IRB=1E-06
- CJE=1.742E-11 CJC=5.045E-12 XCJC=0.1041 FC=0.8555
- NF=0.993 NR=0.999 NE=1.18 NC=1.397 MJE=0.3092 MJC=0.1947
- TF=7.073E-10 TR=1E-08 PTF=0 ITF=0.1495 VTF=6.144 XTF=289.5
- EG=1.11 KF=1E-9 AF=1 MFG=PHILIPS)
.MODEL BF470 PNP(IS=9.124E-15 ISE=1.672E-15 ISC=2.139E-13 XTI=3
- BF=198.2 BR=1.256 IKF=0.13 IKR=0.1 XTB=1.5
- VAF=465.9 VAR=13 VJE=0.8484 VJC=0.6298
- RE=0.635 RC=1.42 RB=5 RBM=0.5 IRB=1E-06
- CJE=1.447E-11 CJC=8.483E-12 XCJC=0.619 FC=0.99
- NF=0.9904 NR=0.99 NE=1.527 NC=1.08 MJE=0.3884 MJC=0.4561
- TF=1.38E-09 TR=1E-32 PTF=0 ITF=0.065 VTF=2 XTF=21.78
- EG=1.11 KF=1E-9 AF=1 MFG=PHILIPS)
anyway I found this circuitry has too much distortion @1MHz for Elvee's demands, and is little peaky at this frequency.
cheers
Pawel
PS for 1KHz it is excellent
I rechecked, and indeed with the current version, the transistors seem to do nothing.
Several iterations before, it provided a >4 fold improvement n THDi
I am still trying to improve my amplifiers, and the best candidate so far is the Groner-based one, but I am faced with a strange behaviour: when the compensation cap C1 is too small (12p), the THD is relatively good (0.003%), and logically the FR has a nasty peak due to insufficient margins.
If the cap is increased to 22p, the FR is ~flat, and the THD increases, which is to be expected. What is surprising is the magnitude: it shoots to 0.015%, a five-fold increase, when the cap value is not even doubled.
In addition, the circuit tolerates an output-inclusive scheme, which means that increasing the compensation should have a minimal effect on the THD.
Can someone explain that paradox?
If the cap is increased to 22p, the FR is ~flat, and the THD increases, which is to be expected. What is surprising is the magnitude: it shoots to 0.015%, a five-fold increase, when the cap value is not even doubled.
In addition, the circuit tolerates an output-inclusive scheme, which means that increasing the compensation should have a minimal effect on the THD.
Can someone explain that paradox?
