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L'Amp: A simple SIT Amp
L'Amp: A simple SIT Amp
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Old 8th May 2018, 07:35 PM   #2911
maxlorenz is offline maxlorenz  Chile
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Quote:
Originally Posted by sontero View Post
Hi Max
Also me have a pair of sk180 as a soon experiment with l'Amp.
For now i have build a pair of MoFo monoblock....very great amplifier.
Waths is the gain of your interesting CFP?
Waths bias have the sk180 for 50v B+?
Hi and thanks for your interest.
I now realize that I never posted the updated schematics...I will do ASAP. My AMNESIS amp project is consuming all my free time My whim was to put there a CFPcascoded-CFP output and now I my trying to stabilize it That amp rivals this one soundwise...

No idea what the gain might be; I confess I didn't measure much parameters and went directly to listening. The gain is formidable though as both stages amplify. The gain can be set by trimming R1 and R2 on the diffamp, well and also trimming Rd on the output stage.

IMHO, key to good sound is providing separate regulated supplies for each section. I might test now separating signal and power ground with 10R, now that I think of it...

The bias is -3.3VDC for my 180 units and that for 1Amp current, last time I checked...

Mr Pass published a version with CCS that of course must be more efficient. I have it here somewhere...

As I said before, I had not the time to do the multiple mods that swarm in my head

Cheers,
M.
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Old 8th May 2018, 10:51 PM   #2912
maxlorenz is offline maxlorenz  Chile
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From memory...
It is a good idea to put some pins (like from DIP8 adaptors) on PCB to play a little with R values.
Attached Images
File Type: jpg diffamp CFP comp cascodo TOKIN SK180.jpg (99.2 KB, 241 views)
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Old 9th May 2018, 01:15 AM   #2913
sontero is offline sontero  Italy
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Quote:
Originally Posted by maxlorenz View Post
From memory...
It is a good idea to put some pins (like from DIP8 adaptors) on PCB to play a little with R values.
Hi Max
thanks for the schematic.
your CFP scheme fascinates me and I would like to try to adopt it as a front-end of the MoFo. since you've posted the diagram from memory I'd like to ask you to verify it.
I could make it fast on a perfboard with a supply at + 15v / -15v.
I would also like it if you describe in detail the most important parts of the circuit and possibly how it works
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Old 9th May 2018, 10:49 AM   #2914
maxlorenz is offline maxlorenz  Chile
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Thanks again.

Be aware that I'm only a dilletante with no formal tuition in electronics, and that I don't know MoFo nor its requirements from input signal point of view...

The diffamp is a classic differential amplifier with a common-drain buffer attached. I suppose C1 is not strictly necessary if you have something like C2.

Better go with +/-24 supplies for better headroom. Use your favorite low power VReg.
R1-R2 decide the gain and the resistor tail (R5->Rn) defines the current for the CCS. You must check with oscilloscope to avoid clipping and to secure adequate gain for your next stage. Choose high quality, low noise resistors for best sound. IF you cannot have desired gain, you can mod it with the transistor based mods recommended above.

Note and respect pin description (G.S.D.) for the JFETs as there is a small mistake on the original schematics that I always forget to correct...

Good luck and may the Force be with you.
M
Molti auguri
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Old 9th May 2018, 01:00 PM   #2915
sontero is offline sontero  Italy
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Quote:
Originally Posted by maxlorenz View Post
Thanks again.
.................................................. .................
Be aware that I'm only a dilletante with no formal tuition in electronics, and that I don't know MoFo nor its requirements from input signal point of view...
M
Molti auguri
many thanks Max
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Old 9th May 2018, 11:20 PM   #2916
maxlorenz is offline maxlorenz  Chile
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You´re welcome. I'll be here to help...if I can.
I hope you like the sound.

I wonder if anybody here has the Spice model for that 2SK180(???)

Best wishes.
M.
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Old 10th May 2018, 12:43 AM   #2917
vanofmonks is offline vanofmonks  United States
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Has anyone tried using the 193u? I searched for 193u and didn't get any results. It is 200mh with 2A rating. 1.7ohm resistance though. Would it work on the self biased version @1.6A, or is the resistance too high?

Thanks
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Old 10th May 2018, 10:28 AM   #2918
gadut is offline gadut  Indonesia
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Quote:
Originally Posted by vanofmonks View Post
Has anyone tried using the 193u? I searched for 193u and didn't get any results. It is 200mh with 2A rating. 1.7ohm resistance though. Would it work on the self biased version @1.6A, or is the resistance too high?

Thanks
You need to increased B+ for self bias, use 2x25V transformer
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Old 10th May 2018, 03:47 PM   #2919
BeardyWan is offline BeardyWan
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HI Max,


Mike Rothacher suggested this...




*--------------------------------------------------
*2SK180
*GENERATED BY SIT MODELER @ AUDIOHOBBY.COM
*MODEL RANGE: 100V, 5A
*--------------------------------------------------
.SUBCKT 2SK180 D G S ; Drain Gate Source
+ PARAMS: MU=17 X=1.5 K=0.67 N=1.76 VCT=0 RG=2MEG
*--------------------------------------------------
B1 D S I=K*PWR(URAMP((V(G,S)+VCT)+(N*LN(V(D,S))+(V(D,S)/MU))),X)
*FOR MULTISIM COMMENT OUT ABOVE LINE (*) AND UNCOMMENT NEXT LINE
*B1 D S I=K*PWR(MAX((V(G,S)+VCT)+(N*LN(V(D,S))+(V(D,S)/MU)),0),X)
R1 G S {RG}
CGS G S 2000P
CGD G D 2000P
CDS G S 0P
.ENDS 2SK180
*--------------------------------------------------
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Old 10th May 2018, 06:00 PM   #2920
maxlorenz is offline maxlorenz  Chile
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Quote:
Originally Posted by BeardyWan View Post
HI Max,


Mike Rothacher suggested this...


*--------------------------------------------------
Great! Thanks.
I'll see if it works for me...

Best wishes,
M.
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