Nelson Pass F5 Part Deux

I'll be waiting to hear about any differences, also. I ordered this Vishay device.

If the hexfred devices work out better for you, Tal, let us know. It is a simple enough swap out, I'm thinking, an additional screw hole and termination change.

BTW, if the USPS doesn't deliver my Digikey order, today, you'll be seeing something in the news-"A postal truck was hijacked, this evening, enroute from Thief River Falls to the Twin Cities. The truck was later found with only one small package missing".:D

Westend, I'm sure those are more than adequate, but I dont see anything about "super fast recovery or anything like that. Allegedly, these ultra fast rectifiers remove a lot of grunge and improve things sonically. All my previous builds have just used basic rectifiers, I have never tried these fast devices, but I am this time.

Tech-DIY isnt shipping until after 10/20, so I've got a wait before I can stuff boards.

Russellc
 
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I'll be waiting to hear the "listening impressions" from the Hexfred users, especially Tal, who will be able to compare the standard device with the IXYS devices.

I probably should have gone with the fast recovery diodes, originally, but price controls some of my decisions and others have reported good results with the standard devices. On the other hand, this amp is certainly a build for the "best quality" of sound available so why not spend an additional $30 if it returns even a slight improvement.

I guess I'm starting to understand the decisions that mfg.'s have to make regarding component choices. From reading the F5 thread at DIYaudio, it seemed NP's decision to use the faster diode was somewhat placed upon some type of Euro standard involving EMI, IIRC.

I am still trying to totally understand the speed relationship regarding the fast-recovery diodes vs. the standard devices. This is all measured in nano seconds and I've never seen electrons race so don't know which to put my money on.:D

I'm waiting on parts, also, Russell.
 
I'm a self admitted tube guy, but after seeing all these F5 build threads with the beautiful amps everyone is making it got my curiosity piqued. I read a little about these "F series" amps that Nelson Pass has so kindly put in to the public domain, and I must say that I'm more than intrigued. From the description of each amp, I'd really like to try both the F4 and the F5. I like the idea that you could put the F4 between a flea tube amp and an inefficient speaker for some wild combos. Drive a Vandersteen with a SE EL84? Crazy. Sign me up. The F5 appeals to me in the same way the classic Pioneer "M" series amps does: Solid state done strictly for the sound, damn the specs. The difference is that I'd never feel comfortable with something as rare and expensive as an M series, but I'm pretty cavalier with stuff I build for myself. If it dies, I should be able to be my own tech.

I've been seeing different PCB vendors, some clearly approved by Mr. Pass, some less so. Where did you guys get your F5 PCBs? I didn't see anywhere that I could clearly get F4 PCBs. The power supply looks pretty much identical for each amp, there seem to be PCBs aplenty on the 'Bay and elsewhere for them. They also seem easy enough to homebrew, if one wanted. The ideal transformer seems to have dual 18VAC secondaries, and over 300VA. The Antek AN-4218 looks to be about where the best price/performance break to me, it's 400VA, and less than $50. I think it's neat that there is some ambiguity as to which rectifier is best, it will give me something to "roll".

I'm finishing an audio deal today in which I get a Hafler DH-200 amp that is on the fritz. I want it because I plan to gut it and use the chassis for this endeavor. After seeing everyone source heatsinks and do a bunch of metalwork I said, "nah". I hope to find some F5 PCBs that will fit on to the Hafler's heat sinks without too much work.
 
Could anyone tell me how big physically the amp PCB is? Thanks!
 
Could anyone tell me how big physically the amp PCB is? Thanks!

not measured, but this should give you an idea

oops.jpg
 
Could anyone tell me how big physically the amp PCB is? Thanks!
3 15/16" X 2" for the C Viller boards. I think the P Daniels boards are even smaller.

BTW, I would seriously consider getting the PS board from Christain Viller, as well. The layout and quality fit this project.
 

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One week follow up.
After running the FREDs for a week I can say they are definitely 'a little' better.
It is kind of hard to quantify, and I guess it could be somewhat of a placebo effect, but the amp seems now to be voiced even smoother than before; the proverbial velvet sledgehammer when paired with the cornwall III's.
With literally ZERO noisefloor, wonderful dynamics, the pride of DIYing an amp of this magnitude is just the delicious icing on the cake called the F5:music:
my f5 was a well worthwhile project, tons of fun to build and a joy to own. My only regret is that I wish I could afford to build another!!

i hope to see even more builds spring up:thmbsp::thmbsp:

IMO the FREDs were worth the extra $30, not that i ever doubted anything Mr. Pass would design or implement into one of his designs:ntwrthy:
Lovin' the F5!
cheers,
tal
 
Thanks for the update, Tal.
My strategy on the rectifiers will be to keep the Vishay devices installed and roll in the rectifier boards I already have and then the Hexfreds. The rolling will be at a later date when I have my dirty little hands on the osciliscope that is on it's way to me and have cleared the deck of other projects.

I'm with you on the benefits of being able to build an amp like this, a fairly easy project that has a lot of reward, along with being able to modify. Icing on cake says it all :yes
 
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I have exactly 3.75" of clearance where I want to put the PCB. Any wiggle room on the C.Viller PCB's? No hope in hell of getting them in there?
 
If anyone wants to order a few heatsinks as to get to the minimum order, I would be interested.

What is everyone using to go from the input rcas to the boards? Seems like some of my reading is suggesting some kind of shielding?

Thanks,
Russellc
 
If anyone wants to order a few heatsinks as to get to the minimum order, I would be interested.

What is everyone using to go from the input rcas to the boards? Seems like some of my reading is suggesting some kind of shielding?

Thanks,
Russellc
That's what I comprehend, also, from reading the F5 thread at DIYaudio. I plan on using this interconnect wire I have on hand, copper shield, foil shield, twisted pair stranded 26 Ga.. I will leave the shield to float, using the inner pair for connections.

If you need a couple of feet, shoot me a PM.
 

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If anyone wants to order a few heatsinks as to get to the minimum order, I would be interested.

What is everyone using to go from the input rcas to the boards? Seems like some of my reading is suggesting some kind of shielding?

Thanks,
Russellc
I used this mogami neglex star-quad 2534
2534.JPG

http://www.markertek.com/Cables-Con...Audio-Cable/Mogami-Wire-Cable-Corp/2534.xhtml

this is my wire of choice for IC's:thmbsp: has been plenty shielded for use in my f5!

For speaker output wiring I used Kimber TCX teflon variable strand OFC
wire003.jpg

wire005.jpg

wire006.jpg

cheers,
tal
 
Nice, thanks for the tips guys, my parts are supposed to be delivered today!
got Bruce Springsteen ticket this eve, so likely wont even get it opened.

Thanks again,

Russellc
 
Good pics, as always, Tal. Thanks.

I have a couple more questions of the "did you do this" type: 1. I assume your AC filter is handling any in-rush current but did you use a thermistor on the transformer primaries?, 2. What type of adhesive did you use for mounting the standoffs to the chassis? TIA
 
I did NOT use a thermistor at all on the primaries, only on the driver boards
I used a 2 part epoxy to tack the standoffs to the chassis. I clearly used too much considering that there is no real need for any strength of bond here but i decided that a little 'extra' to be sure they couldn't shift couldn't hurt:no:

your f5 looks great.
cheers.
tal
 
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