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PostPosted: 22 Jun 2008, 22:33 
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EDIT (by diyAudioProjects.com): Split from Audio Nirvana Super 12 Bass Reflex Speakers
RiGuy wrote:
I am building an F5 stereo amp by Nelson Pass and am close to done with it. (I think I am close to done we will see how it works) I am waiting for a heatsink and I need two more 100 ohm resistors at 3watts and a few 4.7k thermistors and then it will be finished. So I am hoping by next weekend I will be able to figure if its my Harmon Kardon that is screwing up the sound or if its something else. I am pretty sure its the HK since other speakers had the same problem with it and the same benefit with the tube amp, but would another different and hopefully much better solid state amp make a difference? We will see. So until then I can only say they sound really good on my tube amp and the bass is not lacking. However, the tube amp can not produce the bass that the HK can so hopefully the F5 will solve several problems.

I've been thinking lately about such an amp. I'll be waiting for your results.

I don't have the skills to make my own, but that won't stop me.

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PostPosted: 23 Jun 2008, 08:08 
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Gary, You have the skills and the budget for this F5 or for a gainclone. Trust me. I had/have zero skills anyway except that I knew how to solder which if you dont know how you will pick it up in a few minutes. Just dont burn yourself, it hurts.
You can get PCB boards made for this amp but its not necessary. You can buy breadboards to pop it together at Radio Shack for 4.99, but you dont need to. You can simply twist wires together for this amp and its cheap to build and its really simple to copy the layout from the schematic. You can do this. Plus the voltage is low so you wont kill yourself building it. Most expensive part will be the Transformer and heatsink. You can put this together for a bit under $150. You could do Gainclone/Chipamp for about $100. Both these figures assume you build the enclosure with spare plywood you have laying around. Use http://www.apexjr.com for most of your supplies and go to Digikey for best prices/selection for the chipamp and to Mouser for best prices/selection for F5.
edit: You could use same power supply for both amps so you can save money if you decided to build both.
RiGuy

of course I will report back, but this is a Nelson Pass design.... Its gonna sound good.
http://www.6moons.com/audioreviews/firstwatt7/f5_2.html

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PostPosted: 23 Jun 2008, 12:17 
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Yes, all you really need are some basic soldering skills.

RiGuy, I can't wait to see some pictures of your build progress. I really like the idea of two amps sharing one enclosure and PS.

Cheers,
Gio

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PostPosted: 23 Jun 2008, 13:39 
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Gio, I will take some pics soon. I have the F5 mostly built now. I ordered thermistors, but they came in as chips. SMD type. So small they get lost under my fingernail. I soldered 24AWG to them for leads. But, lost one of them so still am waiting for thermistors. Am waiting for the Heatsink to. Will finish power supply today.
Gio, I am using this power supply, but with 3x12,000uF on each side of the resistors for a total of 12 caps. 400VA 18VDC transformer. Will little 3x4" heatsink work on each rectifier do you think? Any reason this PS would be wrong for a chip amp?

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PostPosted: 23 Jun 2008, 17:18 
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3 x 12,000 uF will be way more than enough for any gainclone amplifier (Class A/B) application. However, check the Pass documentation to see how much capacitance the F5 (Class A) will want. The schematic you posted is 4 X 15,000 uF. Class A amps like a stiff power power supply.

Did you buy pc boards or are you using a breadboard?

3 x 4" heat sink seems ok for the rectifiers. What are the rectifiers rated at?

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PostPosted: 23 Jun 2008, 17:46 
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Using Breadboard as no pcb were available for F5 (thanks for splitting topic). Will use breadboard for LM3886 as well.
I am using 6x12,000uF per channel but they are separated by the resistors shown in schematic. So 144,000uF for stereo operation. I have 8 more I could use if I take apart my power supply for the HRII and just use this power supply for it. That would put me at 240,000uF :)
The rectifiers are rated at 420Vrms and 600Max with 35Amps.
RiGuy

ps Got my heatsink today. Its a bit.. um. massive :) 12"x12"x4"

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PostPosted: 23 Jun 2008, 21:19 
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Thanks for your vote of confidence, but I can't even make heads or tales of the schematic. :confused:

I would need darn good instructions and a kit to build something like those amps. Maybe I'll have to check out BrianGT's Aleph boards and see if that gets me closer.

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PostPosted: 23 Jun 2008, 22:49 
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RiGuy wrote:
ps Got my heatsink today. Its a bit.. um. massive :) 12"x12"x4"

The chip amp won't need much heat sink, but the F5 will. Look at the heatsinks in that 6moons review.
ejfud wrote:
I would need darn good instructions and a kit to build something like those amps. Maybe I'll have to check out BrianGT's Aleph boards and see if that gets me closer.

Don't worry, RiGuy is going to take a lot of pictures and put together a good guide! :D

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PostPosted: 23 Jun 2008, 23:06 
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Oh my. Gio you are getting me in trouble here :)
I just suggested to him that he build the K502 to go with that fantastic pair of speakers he just built. I will send him some PIO caps and suggested he find a nice dual 100k pot or ask you for suggestion. Of course just a few months ago I spent $140 on my K502 and now they want $195. Its worth it though.
If he cant read that power supply schematic, which I never could have either if I didnt have to learn it at work, then I dont know how I can explain the F5 any better than Nelson does in his excellent article of how to build it.
However, if you are going to go ahead and build a Nelson Pass amp, get your feet wet with F5. I am sure Gio and Bruce will help and I promise I will help as well.
OTOH why not build both and have a DIY tube and a DIY class A?
So, up to you but either one is going to sound grrreat with those speakers.
RiGuy

Also, Power supply just about done. This you could build after I take pictures of it. No Problem at all. My F5 breadboard is a mess but will work I think. Very kludgy looking.
Yeah I saw the sinking in the review but I think this is even more sink than he was using. Plus you should see the sinks one of the more recent builds is using. They were a bit on the small side with not many fins. That doesnt mean it will last long I guess, but he claims stable operation and stable temp.

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PostPosted: 24 Jun 2008, 12:36 
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So is the plan just to have a switch on the power supply to select between the F5 and gainclone? Will they share the RCA inputs and speaker terminal outputs?

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