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Old 19th December 2011, 03:04 PM   #71
pooge is offline pooge  United States
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I would favor keeping one pair of main caps on board, and a separate or breakaway portion for any PS extras; i.e., second pair of caps and/or bridges.
This would shorten the board, provide on board main caps, and allow for keeping bridge(s) and first pair of caps, with their associated ripple currents, away from the circuit.

This would also provide a generic board for all variations of PS front end tastes. Provision for the series resistor/inductor between pairs of caps can be kept, if there is room, or provided on any separate or separable section.

I would still favor a positive and negative input connector pair close to each other for each main cap to keep twisted pair supply lines twisted up to the board, and a split ground plane between the main caps up to the star point.

BTW, nice effort!

Another option, if the bridge(s) and first pair of caps were on a separate board, is to use that board for the PS components for the supply for the input stage of the amp. Put BOTH input and output power supplies on the separate board.

Last edited by pooge; 19th December 2011 at 03:21 PM.
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Old 19th December 2011, 03:32 PM   #72
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Ferrari, Anatech: I am with you.

The PCB with onboard-PSU looks like a big whale, makes it hard to handle and since most of you already have beautiful power-supplies,
it would be "money poured down the drain".

METAL and I will nevertheless offer to those of you, who do not have a power supply, a PCB based on these schematics: Greg's Web Site - DX PSU.

This PSU has been proven to work flawlessly, and I will even change its design to include 2 full bridge-rectifiers.

It will look like this:

Click the image to open in full size.

http://www.abload.de/img/birger0022gjtf.jpg

And, of course, we will offer a shuntie for the frontend.

Mihai's AMP will have to compete with this one:

Click the image to open in full size.

http://www.abload.de/img/joe003hekwo.jpg

This is a SYMASYM 5.3, Anatech, which I modified to include 2 pairs of beautiful NJW0281 / NJW0302 on the backend and a cap-multiplier for the frontend, and which I offered in a German group-buy several weeks ago.

You are welcome to visit me in Hamburg in spring 2012, when I will perform a "shootout" between Mihai's RMI FC-100 and Michael's SYMASYM.

Best regards - Rudi_Ratlos
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Old 19th December 2011, 08:16 PM   #73
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by metal View Post
YES, but there are better ones around.
Audibly better in this application? Or at least simulates better with this amp, enough so that a difference can be seen at the amp output?

I would suggest that tight coupling of the front end supply to the amp is probably more important for real life performance, than reaching for the nth degree of frequency response at the output of the regulator.

Sheldon
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Old 19th December 2011, 08:33 PM   #74
zdr is offline zdr  Belgium
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Quote:
Originally Posted by Rudi_Ratlos View Post

You are welcome to visit me in Hamburg in spring 2012, when I will perform a "shootout" between Mihai's RMI FC-100 and Michael's SYMASYM.
@Rudi&Metal: If you would like to discuss Mihai's design, maybe you should consider doing it in RMI-FC100 thread. We are derailing this one into something I do not like too much, and would probably dislike even more if I was the designer of FC100. I have a great respect for Mihai's work, and would not want to end up building Symasym, FetZilla or lawn mower with FC100 boards from this thread. I don't know about the rest of the guys, but unless PCBs respect the original proven and tested design, I think I will pass for now.

Sorry if I am getting too sensitive about all this, I still think you guys are doing a great job
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Old 19th December 2011, 09:19 PM   #75
anatech is offline anatech  Canada
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Hi zdr,
I referenced the Symasym purely to explain a related design that I thought filled a certain power class. No direct comparison was intended, although I have built these earlier designs. They are popular enough to make a valid reference point. What I am discussing is a similar or near identical design for a lower powered cousin.

If I wished for a Symasym, I'd have simply built another. Relax.

Hi Andrew,
No one said that the same bias network must be used. In fact, a Vbe multiplier that used a pair of internal diodes would probably work great. All you need is a fast reflection of temperature. Given the close matching these devices have, it would be a safe assumption those other die will be very close to the temperature you are monitoring.

Don't look for reasons "why not". Look for ways to move forward.

-Chris
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Old 19th December 2011, 09:29 PM   #76
anatech is offline anatech  Canada
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Hi Rudi,
Thank you for the invitation. I can't make it, but I would have really enjoy meeting with you. You and Metal have done some fine work here. I would be interested in what you find in comparing the two amps. This one looks like it should out-perform the Sym..... I don't think I'm allowed to say the name here.

I really love the NJW0281 and NJW0302 as well - you may have guessed. I am a huge fan of this line of output transistors, and also the MJW series (without the diode). I also think it's important to realize that you only need a couple devices with the sensing diode, the others can be straight transistors. I've been waiting for someone to show a design that wasn't straight out of the app note as far as the bias circuit was concerned.

If you have some info on your modification done to the Sym.... , would you be willing to share it with me?

So back to the design at hand. Front end regulation is the "secret sauce" that can make these designs special. I am anxious to see this design finalized. It looks extremely promising.

-Chris
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Old 19th December 2011, 10:08 PM   #77
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I respect your sentiments, ZDR, but - at the same time - like to say: I am different from you.

I am a very pragmatic type of person.

I have DIYed a lot of AMPs so far, have been listening to their sound, tried to improve it (if possible) by very small changes,
(adding a CAP-multiplier to the frontend-power supply of Michael Bittner's SYMASYM, integrating a PSU on Carlos Mergulhao's DX BlameES, ...),
I have never changed the inherent schematics of an AMP, but made my little progresses available to the DIY community.

Did you ever listen to Carlos' DX BlameES with big SANKEN transistors on the output, to Michael's SYMASYM driving a pair of TO-3 or TO-3P?

If not: I understand, why you will withdraw from this thread.

As I told in post #1 of this thread, I felt very appealed to Mihai's implementation of an amplifier.

I will not change any single track or component of Mihai's design, but feel free to offer to the DIY community a layout that does not have
any "PSU ingredient on-board" (on the right side of the PCB) at all.

I will offer - on the other hand - a proven backend- and frontend (Mihai's shuntie) power supply.

So: what?

I will of course - I am a pragmatic type of person - compare the sound of Mihai's RMI FC-100 to Carlos' DX BlameES and Michael's TO-3P SYMASYM or ... and will report the feedback.

May I not?

Best regards - Rudi_Ratlos
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Old 20th December 2011, 05:59 AM   #78
roender is offline roender  Romania
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Guys, calm down please! There is no FC100's cult here :-)
I'm more than glad that Rudi and Metal wanna compare my design with other very popular at diyAudio. Let's the battle begin!

Anatech, the RMI-FC100 biasing schematic is not implemented strait from ONsemi app note because they ignored the differences between BJT and diode thermal coefficients.
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Old 20th December 2011, 06:20 AM   #79
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Hi zdr,

"proved" doesn't necessarily mean perfect. If you add "im" to "proved", it becomes improved. Don't we like improved stuff?

Calm down, no need to consider changing as a disrespect to the original Amplifier designer.

Don't forget that we like you and want you with us in this thread :- )


Hi Sheldon,

There is a better design, but we will not discuss it in this thread. Rudi has already stated that we will not enforce serious changes at this stage. Forgive my loud thinking.



Today I will try to post an image for the final amp PCB. I still must work on the front PCB and the PSU PCB.
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Old 20th December 2011, 11:44 AM   #80
Ferrari is offline Ferrari  Netherlands
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One small wish on the amp power supply PCB...
Can we have the PSU PCB to support electrolytic capacitors with 35mm diameter?
Thanks!
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