Several of Q-s about Citation 12 MosFet

[argo]

Hi to all Pass fans

I have been thinking to build a Mr. Pass Citation 12 MosFet version for some time.
Looking at the schematic in the original article I got several questions?
 Why the outputs Fets (Q6, Q7) are not equipped with the Grid stop resistors?
 Are the diodes D1, D2 between Drain and Source really necessary with modern Fets like IRF240, where the Fets already have those diodes installed internally?
 What’s the purpose of R8?
 Why the input cap is excluded?
 I cannot easily source suggested ZTX450; ZTX550 transistors locally so I think to use BC560 for the diff pair (Q1, Q2). Can they be safely used for Q3, Q4, and Q5 as well or should I use some more powerful devices like BD139 and BD140.
 Would adding the rail decoupling caps (like 100uF parallelled with 100nF) improve anything?
 Are there any other improvements to the circuit that could be made?

Cheers,

Argo

 

[Nelson Pass]

1) They apparently not needed as they are driven by
relatively high impedances.

2) No, they would be superfluous.

3) I recall connection to chassis, which is otherwise isolated.
This might be an error.

4) Why include it?

5) I imagine they will work fine.

6) Maybe

7) No doubt. Norm Thagard wrote an excellent piece for
AudioXpress on the Mosfet 60.

 

[argo]

Short and sharp
Thanks a bunch Mr. Pass

Argo

 

[Zen Mod]

Short and sharp
Thanks a bunch Mr. Pass

Argo

hehe-old Fox!

 

[Drafance007]

First One

Well on sugestion by Millwood...i built Mosfet citation 12 and was very satisfied. Well my first Mosfet amp ever but good one. Good Job Mr.Pass.
Pcb was made for about half an hour. Everything elese on about 1 hour. and there is the music. I also did destroy one pair of irf540. Maybe beacouse bias tromier pot was old 1o years like all the other components

 

[Drafance007]

other side...panic and acid made board...

 

[Nelson Pass]

Very excellent.

 

[Nat Riscica]

Hello,

I am built the Citation 12 using the MPSA 42 & MPSA 92 for all the transistors used, and the IRFP 240 for the Mosfet.
He work great!

Thank you Mr Pass.

Nat

 

[wputera]

i build citation 12 mosfet using 2sk1058, sounds great but the amp runs very hot, my finger can't hold the output transistor for 10 seconds

Any suggestion Gentlemen? I love the sound of this amp very much.

What should I do if i want to parrallel the output with 10 pieces IRF 450? Are there any changes for the components and its value?

Thank you Gentlemen, especially Mr. Nelson Pass.

Cheers,

 

[Nelson Pass]

Sounds like too much bias. You need to measure the
idle current in the output stage, for starters.

 

[lumanauw]

Why nobody ask about D3? It's very clever to put it there due to bootstrapped VAS.

 

[lumanauw]

Hi, Wputera,

Apa kabar?

The amp is designed for Vertical mosfet. The threshold is about 3.5-4V.
K1058 is lateral mosfet, the threshold is below 1V. You must modify the Vbe multiplier's resistors (R14 or R15).

 

[wputera]

Okay Mr. Nelson, i will try to set the bias current. Thank you for your help.

Hai Mr. Lumanauw, kabar saya baik.

Thanks for your help too, I will modify R14 or R15. Should I increase the or decrease the value of R15 (10 k Ohm)? Thank you Gentlemen.

Cheers.

 

[lumanauw]

Hi, Wputera,

To reduce bias voltage in VBE multiplier, B-C resistor must have less value or B-E resistor have more value. (Perbandingan resistor B-C dan B-E yang dimainkan)

 

[wputera]

Thank you Mr. Lumanauw. That's will solve my problems with my MF-CITATION 12.

YBU.

CHEERS,

 

[atcgreg]

Hi all fans of Citation mosfet12 .

I build one, sounds great, but I have a huge problem with HUM when hooked up to a preamp Sony TA E80ES When the amp is not connected to the preamp it is silent.

I have checked all ground connections on the amp seems all ok could it be that the impendance of preamp does not match the amps.

the hum is only when I connect the preamp .
Preamp it self connected to any other monoblok amp has no hum.

Please help!

 

[nrg2009]

I wonder if anybody offers boards for this amp? It seems like a very rewarding build.

 

[Rafy]

Hello,

I am built the Citation 12 using the MPSA 42 & MPSA 92 for all the transistors used, and the IRFP 240 for the Mosfet.
He work great!

Thank you Mr Pass.

Nat

Hi Nat,
Did you make any changes to the value of r1, r2 and r12, within the set mps 92/42?
What is the value v rail that you use?

My plan will also use IRFP240 complementary. Your information will be very helpful to me to get a good sound on the amp that I will build.

Mr Nelson,
Thanks. I really appreciate your great masterpieces.

 

[Bangla H]

Mosfet Citation 12 by kramskee

Because the long time interest here about Mr. Pass work (on kitchen table) in early days....i bought these clever boards- two options possible.
For me a must build to listen an Oldie Amp .
12th September 2016, 03:36 PM
* #1271
kramskee *
diyAudio Member
*
Join Date: Jan 2015

Ranchu, I've just produced a set of baords for the citation mosfet 12, configurable as complimentary or quasi complimnetary separate output and driver boards. designed to fit a standard square extrusion. PM me if you're interested ......... you can see pics here on this thread

citation 12 mos fet