RMI-FC100, a single stage audio power amplifier

[AKSA]

Mihai,

These are terrific figures.

Wonderful - Congratulations!!

Now commercialise the amp and make some money.......

Are you ready for the challenges?

Hugh

 

[roender]

Mihai,

Now commercialise the amp and make some money.......

Are you ready for the challenges?

Hugh

No thanks. I don't want to make any money from that.
I just do it to prove myself that I'm capable to design and build a good sounding amplifier from scratch.
Now, a nice amplifier case is another challenge ...

 

[P.Lacombe]

I love this wonderfull design too (= excessively + also) !

But... I'm sorrowfull because of C21. An electrolytic capacitor at the most critical node... even of very superior quality...

Regards,

Pierre Lacombe.

 

[AKSA]

Pierre,

With a servo, and using JFET LTP, you could easily remove it.

However, what makes you think this cap will destroy the sound?

Hugh

 

[roender]

Dear Pierre,

In an earlier design stage I was worried about this elcap and for tests I've replace it with a DC servo with 0.1Hz response time. The change in sound fingerprint was NULL ... or my ears are not able to hear it.
Not the same thing I can say about the series input cap, even a very good quality one will affect the sound, not in a bad way but will make it colorful and unnatural. I have a pre with almost zero DC so I decide to not use one.

Mihai

 

[roender]

One more thing regarding elcap to ground in feedback network.
I don't know why many designer use to bypass that cap with a polywhatever "good quality" capacitor. There is no need for that if you use a low ESR one.
The risk for micro oscillation is huge at paralleling low esr elecaps with other very low esr capacitor.

 

[GEirin]

HI Pierre Lacombe.

C21- no electrolytic capacitor. Why?

GEirin

 

[atiq19]

RMI-FC100

Congratualtions Roender!

Very unique design. I'm interested in building your amp.

-Atiq

 

[destroyer X]

I am learning a lot, in special because of Roender and Hugh

Thank you Nordic....by the 2SK170, as you will mail the HRII boards will be easy to put them inside..thank you very much.

Well.... by appointment of Mr. Hugh.... and also because Roender's superior design i will try this one in January.

I am printing your conversation to read and study, there are important informations...thanks Hugh and Roender...in special those two ones, because of exchange of informations are turning this thread very rich in knowledge offered to all of us.

Thanks,

Carlos

 

[sparkle]

Dear Roender,
can we have some parts info related your "shunty" psu ??
please?

thanks

 

[johanne]

hello roender

great design, and i´m in phase with carlos!
please tell us how to buy the thermal traks.

regards
Ralf

 

[roender]

hello roender

great design, and i´m in phase with carlos!
please tell us how to buy the thermal traks.

regards
Ralf

Thank you Johane.
You can order sample from ONsemy and you have to pay for transport only:
http://www.onsemi.com/PowerSolutions/product.do?id=NJL0281D
http://www.onsemi.com/PowerSolutions/product.do?id=NJL0302D
Or you can buy from Digikey.

Mihai

 

[roender]

Re: I am learning a lot, in special because of Roender and Hugh

... and also because Roender's superior design i will try this one in January.

Thanks,

Carlos

Dear Roender,
can we have some parts info related your "shunty" psu ??
please?

thanks

Dear Carlos,
I am glad to hear that!
You will have my full support because this amp is not ease to build.

Dear Sunrise,
The BOM and construction details will be ready tomorrow

Mihai

 

[sparkle]

Re: Re: I am learning a lot, in special because of Roender and Hugh

Dear Sunrise,
The BOM and construction details will be ready tomorrow

Mihai

thanks

 

[johanne]

thanks for info, so on not off

regards
Ralf

 

[roender]

RMI-FC100 amplifier BOM
Resistors and capacitors values are printed on schematic.
http://www.diyaudio.com/forums/attachment.php?postid=1349109&stamp=1194852081&
All resistors are 0.6W metal film with exception of
R3, R4, R10, R33, R39, R47: 2W metal film.
R8, two 10ohm 0.6W metal film resistors conected in parallel
C8, C9, C18: silvered mica or styrofelx or ceramic NP0
C1, C10,C11: WIMA MKS4 63V
C2, C7: WIMA MKS4 250V
C21: 16V LOW ESR (Panasonic, Rubycon)
Biggest capacitors on PCB: 4 x SAMWHA 10.000uF/50V HC series *
Capacitors colse to power BJTs: 4 x Panasonic 1000uF/63V LOW ESR FC series *
*- see amp pcb http://www.diyaudio.com/forums/attachment.php?s=&postid=1349504&stamp=1194895504
D1, 1N4148: 1W glass case
D2, D3, D8: Green LED type LT433B or any other rectangular LED with Vf>=1.9V at If=5mA
D7, D6: BL-R5122B.RED or any other rectangular red LED
J1, J2: 2SK170BL with Idss >= 9mA
Q6, Q7, Q9: BC550C
Q11, Q13, Q17: BC560C
Q8, Q15, Q18, Q19, Q21: 2SC3423Y
Q10, Q14, Q16, Q20: 2SA1360Y
Q1: MJE15034
Q3: MJE15035
Q2, Q12, Q25: NJL0281D (prefered) or NJL3281D
Q4, Q5, Q27: NJL0302D (prefered) or NJL1302D

The following BJT peers must have hfe as close as possible:
Q21-Q18
Q11-Q13
Q6-Q7
Q14-Q16
Q19-Q20
Q1-Q3
The folowing power BJT must have the same Vbe +/- 1mV (only between the same type NPN/PNP) and all must have hfe as close as possible:
Q2-Q12-Q25-Q4-Q5-Q27
J1 and J2 must have the same Idss>=9mA and must have the same Vgs +/- 1mV at Id=6.25mA

 

[roender]

RMI-FC100 frontend PSU BOM
http://www.diyaudio.com/forums/attachment.php?s=&postid=1349112&stamp=1194852836
All resistors are 0.6W metal film
R1, R2: 2R2
R3, R4: 33R
R5, R6: 11k
R7, R8, R9, R10: 2k
R11, r12: 560R
C1, C2, C3, C4: 10nF/100V ceramic
C5, C6, C7, C8: 2200uF/63v
C13, C14: 100uF/50V Low ESR
C9, C10: 2u2 WIMA MKS4 63V
C11, C12: 2n2/100V ceramic NP0 or CG0
C15, C16: 470nF/250V MKP or MKT
D1, D2, D3, D4: FR107
LED1,2: Green LED type LT433B or any other rectangular LED with Vf>=1.9V at If=5mA
D7, D8: Z39/1W zener diode
T1: BD140
T2: BD139
Q2, Q3: BC550C
Q4, Q5: BC560C
Q6: MJE15034
Q7: MJE15035

 

[roender]

Starground connection to main capacitors

 

[roender]

NFB connections and starground point

 

[roender]

One NJL diode must be bypassed