Slewmaster - CFA vs. VFA "Rumble"

[Carl_Huff]

... Cascoding the Symetri inputs also allows using ultra low (2db)noise JFETS as input transistors.

Has anyone here built (offered up??) a JFET version of Symetri?

 

[bimo]

The "SYMETRI" simple complimentary (Bimo) has many supporters. ROBUST topology.

"Symetri-Cascode" post #8349. You can run the .asc file to confirm ~ 25% lower THD with your models.

The "spookyamp" (leach amp) also uses complementary cascoded inputs, with a Hawksford VAS instead of the second complementary diff VAS used in Symetri. The BC5xxC transistors have a 4db noise figure. Cascoding the Symetri inputs also allows using ultra low (2db)noise JFETS as input transistors.

The "SYMETRI" should use high local negative feedback and use Miller compensation as small as possible. I tried it using double emitter output and PSU +-45VDC, and I pleased. Here the simulation result:
Phase Margin = 84
Gain Margin = 19
Slew Rate = 140
THD at 70W/8Ohm, 1kHz -> 0.004852%
THD at 70W/8Ohm, 20kHz -> 0.008530%
PSRR 1kHz -> 103

 

[LineSource]

Has anyone here built (offered up??) a JFET version of Symetri?

Normal JFET input conversion.

 

[borys]

I have no idea how does the Symetri j-fet sounds like but with mosfet OPS sound really nice. Just look at the harmonics level - like in the good old book 😀

 

[bimo]

I have no idea how does the Symetri j-fet sounds like but with mosfet OPS sound really nice. Just look at the harmonics level - like in the good old book 😀

😎

 

[Esperado]

I have no idea how does the Symetri j-fet sounds like but with mosfet OPS sound really nice.

There is an interest to use Jfets as input devices, as they don't demodulate HF parasitic components like does the diode of bipolars. But to take full benefit if it, you need to low pass their outputs as they are fast.

 

[thimios]

update list

Nad look at post# 832,963,967.988,989,1005
Spooky #1247,1267,1292,1301
Gnome v1.3 #1455,1467,1485,1500,1516,1531,1538,1567
Symasui #1642,1671,1672,1673
Cfa ver.1.2 #1754,1756,1757,1784
Cfa v1.3 #2976
Wolverine ver1-c #3543,3564,3637,2279
Kypton C #4797,4765
Kypton V #5261,5282
Eyessee #5521
Kypton ND #6830,6850,6888
Bimo-Ostriper Symetry #8064,8066,8091
Infidel an unsuccessful IPS #5385
Ostriper schematic list look at post # 1
I hope this is a complete list and may be useful.

 

[Esperado]

I hope this is a complete list and may be useful.

Thanks a lot. May-be it should be usefull to add in your list, for each design witch are VFA, VFA or the both?

 

[thimios]

Thanks a lot. May-be it should be usefull to add in your list, for each design witch are VFA, VFA or the both?

Ok i will try do🙂

 

[thimios]

List with more details.

Nad (CFA)look at post# 832,963,967.988,989,1005
Spooky (VFA)#1247,1267,1292,1301
Gnome v1.3(CFA)#1455,1467,1485,1500,1516,1531,1538,1567
Symasui (VFA)#1642,1671,1672,1673
Cfa ver.1.2(CFA) #1754,1756,1757,1784
Cfa v1.3(CFA) #2976
Wolverine((VFA) ver1-c #3543,3564,3637,2279
Kypton C (CFA)#4797,4765
Kypton V(VFA) #5261,5282
Eyessee (CFA)#5521
Kypton ND(CFA) #6830,6850,6888
Bimo-Ostriper Symetry(VFA) #8064,8066,8091
Infidel an unsuccessful IPS #5385
Looking for more explanation ? see Ostriper detail list on post # 1
I hope this is a complete list and may be useful.

 

[Kindhornman]

Thimios,
Thank you for posting this information, it does make it much easier to see what everything really is.

 

[thimios]

Thimios,
Thank you for posting this information, it does make it much easier to see what everything really is.

Thanks Steven,as all these are tested in real world and this is a long thread i want to help anyway.🙂
What happen with Pete?🙁

 

[Carl_Huff]

I have no idea how does the Symetri j-fet sounds like but with mosfet OPS sound really nice. Just look at the harmonics level - like in the good old book 😀

Hello Borys,

I am interested in your mosfet OPS. Could you please point me to the details? I presume that it swaps in place of and Slewmaster OPS, correct?

 

[LineSource]

Would someone please post LTSpice .asc file for Kypton-ND V1.1
The "final" version named "super NAD CFA"
I can find the schematic, but not the .asc file.

 

[borys]

Carl
I will post the files later, now I am at some work. I have few more tests to do with this mosfet OPS.
For 5eur I have bought 20 to220 mosfets, they are dead cheap.

Regards Peter

 

[MiiB]

I wonder where OS is hiding..??

 

[borys]

I wonder where OS is hiding..??

I bet he is planning a fancy new IPS ....

 

[31697B]

Nad (CFA)look at post# 832,963,967.988,989,1005
Spooky (VFA)#1247,1267,1292,1301
Gnome v1.3(CFA)#1455,1467,1485,1500,1516,1531,1538,1567
Symasui (VFA)#1642,1671,1672,1673
Cfa ver.1.2(CFA) #1754,1756,1757,1784
Cfa v1.3(CFA) #2976
Wolverine((VFA) ver1-c #3543,3564,3637,2279
Kypton C (CFA)#4797,4765
Kypton V(VFA) #5261,5282
Eyessee (CFA)#5521
Kypton ND(CFA) #6830,6850,6888
Bimo-Ostriper Symetry(VFA) #8064,8066,8091
Infidel an unsuccessful IPS #5385
Looking for more explanation ? see Ostriper detail list on post # 1
I hope this is a complete list and may be useful.

THx for labeling which are CFA and VFA. Now can you please a minimum of specs -- add their SR and THD and power etc?


THx-RNMarsh

 

[jwilhelm]

THx for labeling which are CFA and VFA. Now can you please a minimum of specs -- add their SR and THD and power etc?


THx-RNMarsh

I think OS has hoping you would take care of that. He has me assembling a bunch of different input boards to send to you for testing.

 

[thimios]

THx for labeling which are CFA and VFA. Now can you please a minimum of specs -- add their SR and THD and power etc?


THx-RNMarsh

Sorry Richard, for more details you must look on posts where any IPS was tested. Unfortunately i haven't full details such as distortion and SR no damping factor🙁