RMI-FC100, a single stage audio power amplifier - Page 26

roender · 30th January 2008, 04:03 PM

Amplifier case is almost ready!
Hellp me friends, shall I make the front plate and volume button anodized black?

roender · 30th January 2008, 04:05 PM

View from inside

roender · 30th January 2008, 04:08 PM

Mounting support for volume pot

DRZ1 · 30th January 2008, 05:29 PM

Roender , very good job.

why not mounting the pot at the back and use a extention rod ? I do it like that with my Symasym.

Personaly i prefer black.

roender · 30th January 2008, 07:04 PM

Quote:

Originally posted by DRZ1
Roender , very good job.

why not mounting the pot at the back and use a extention rod ? I do it like that with my Symasym.

Personaly i prefer black.

Thank you Denis

Your case is very nice too.
I will put a DAC inside, monted in front of the case and very close to the volume pot.
This amplifier will have digital inputs only.

Mihai

DRZ1 · 30th January 2008, 07:55 PM

Ohhh, i see.

emanuel_hr · 2nd February 2008, 08:46 PM

Hello everybody, my first post on this forum!
@roender I'm mesmerised ! Congratulations for an excellent amp, I'm really impressed by your skill and knowledge!
I have a few questions about your design. I hope they don't sound stupid, but i am a newbie in electronics and I have quite a hard time trying to understand how amplifier work. So why have you chosen higher supply voltages for the input stage than for output stage? Why is the current source Q17,D8 and R20 connected to the anode of D17(and not the positive supply rail)? What is the purpose of C7?
Thanks in advance for the answers. Maybe you could point to me some good sources of information about amplifiers and electronics.
Once again I congratulate you, and I wish you good luck on your projects!

roender · 3rd February 2008, 01:56 PM

Hi Emanuel,

The only stupid question is the one you don't ask.
Are you doing EE at Politehnica Bucuresti?
Way bigger rail voltage in front than in output stage? It's a folded cascode design, with limited voltage swing in "VAS" at cascode base reference voltage.
"Why is the current source Q17,D8 and R20 connected to the anode of D17 ?
That's a very good question! You are the only one who see that and ask about reasons.
The firs stage is a class A stage and I like to have symmetrically currents in every class A stage I design, with as little as possible return currents to ground, to keep the zero reference clean.
The role of C7 is to slow down voltage response in output stage bias circuit.

Mihai

destroyer X · 3rd February 2008, 05:36 PM

Card boxes used for shoes.

Carlos

emanuel_hr · 3rd February 2008, 05:51 PM

Thanks for the answer! I see that your design is more clever than i thought! I really like your way of implementing current sources. Fancy that!

. Now i see that a good amplifier has a lot of "secrets" and much thinking and work behind. Keep up the good work!

About Politehnica Bucuresti, you came close. I'm doing Automatics.

3rd February 2008, 05:36 PM	#259
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	You amplifier sounds so good that i would be happy with them even inside those Card boxes used for shoes. Carlos __________________ Audiophoolery; http://www.youtube.com/watch?v=m7ERMu825m4; Dx Super Etching; http://www.youtube.com/watch?v=WED3Bvmxepk

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30th January 2008, 07:55 PM	#256
DRZ1 diyAudio Member Join Date: Jan 2007 Location: Quebec City	Ohhh, i see.

2nd February 2008, 08:46 PM	#257
emanuel_hr diyAudio Member Join Date: Feb 2008	Hello everybody, my first post on this forum! @roender I'm mesmerised ! Congratulations for an excellent amp, I'm really impressed by your skill and knowledge! I have a few questions about your design. I hope they don't sound stupid, but i am a newbie in electronics and I have quite a hard time trying to understand how amplifier work. So why have you chosen higher supply voltages for the input stage than for output stage? Why is the current source Q17,D8 and R20 connected to the anode of D17(and not the positive supply rail)? What is the purpose of C7? Thanks in advance for the answers. Maybe you could point to me some good sources of information about amplifiers and electronics. Once again I congratulate you, and I wish you good luck on your projects!

3rd February 2008, 01:56 PM	#258
roender diyAudio Member Join Date: Sep 2006	Hi Emanuel, The only stupid question is the one you don't ask. Are you doing EE at Politehnica Bucuresti? Way bigger rail voltage in front than in output stage? It's a folded cascode design, with limited voltage swing in "VAS" at cascode base reference voltage. "Why is the current source Q17,D8 and R20 connected to the anode of D17 ? That's a very good question! You are the only one who see that and ask about reasons. The firs stage is a class A stage and I like to have symmetrically currents in every class A stage I design, with as little as possible return currents to ground, to keep the zero reference clean. The role of C7 is to slow down voltage response in output stage bias circuit. Mihai

3rd February 2008, 05:51 PM	#260
emanuel_hr diyAudio Member Join Date: Feb 2008	Thanks for the answer! I see that your design is more clever than i thought! I really like your way of implementing current sources. Fancy that! . Now i see that a good amplifier has a lot of "secrets" and much thinking and work behind. Keep up the good work! About Politehnica Bucuresti, you came close. I'm doing Automatics.