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Nelson Pass F5 Mono's

specialidiot said:
I just had to do it. Gary's mono pair is different from my F5 in 3 ways:

  • Panasonic filter caps instead of Cornell Dubilier
  • HEXFRED rectifiers instead of standard Vishay rectifiers
  • Toshibia outputs instead of Fairchild.

Speaker cables are from Blue Jeans, MAC Sound Pipes for interconnects. Source is a 160gb ipod full of lossless goodies.

I can't think that splitting into two chassis makes a lot of difference, perhaps some on real dynamic tracks with lots of stereo separation where bass slam on one channel robs from the other in a shared/common power supply. But I don't think that I'm listening at a level that would affect that.

I have been listening to Miles Davis' "Right Off" from A Tribute to Jack Johnson because I'm pretty familiar with it.

First up was my amp. Upstairs I feed it with a passive pre and use RayW built Indignias. Right now I have my Yamaha C-2x and Cornwalls going.

I like the sound of Cornwalls with the F5, certainly has a better low end than the Indignias. The immediacy and intimacy of the F5 is still there. However there are a couple of moments where Miles' horn in the right channel is a tad harsh. Not bad, but in this case noticeable and a bit surprising because I hadn't heard that in the Indignias.

Moving the speaker cables from my F5 to Gary's was a snap. Gary did you know that your binding posts have a locking feature? You have to unscrew them before inserting banana plugs.

Right away the difference in amps is apparent. The low end is just a tad more taught, the overall impression is that things are a bit more pure. A more "natural sound", to coin a phrase.

The bass line at about 13:55 of Right Now has an attack to it, the following organ notes and guitar "wah wah" jumps out at me. The crescendo organ section sounds pretty cool - has kind of a brash brittleness that jumps out and grabs me in a good way. The trumpet comes in and there is none of the harshness that I heard with my F5.

I have the HEXFREDs, I'd better find another set of Toshibas pretty quick.
f5trio.jpg
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Are you sourcing the Toshibas from the guy on DIY? I'd like to aquire some,
also did you alter any component values from standard due to the Toshibas?

Thanks in advance,

russellc
 
Russellc said:
Are you sourcing the Toshibas from the guy on DIY? I'd like to aquire some,
also did you alter any component values from standard due to the Toshibas?

Thanks in advance,

russellc
Click to expand...

I did buy them from "Bear" at diyaudio. Since I burned up a set in building these, I put the set I bought for myself into Gary's amp. I emailed Bear to see about getting another set but several days have gone buy without a response.

I read somewhere that the Toshibas should be biased lower than the Fairchilds but I can't find it now. I measured my .47 ohm resisters at .60 so I just set the voltage across them at .625, slightly higher than the .6 spec'd for use with .47. Unscientific, but they sound pretty good.
 
specialidiot said:
I did buy them from "Bear" at diyaudio. Since I burned up a set in building these, I put the set I bought for myself into Gary's amp. I emailed Bear to see about getting another set but several days have gone buy without a response.

I read somewhere that the Toshibas should be biased lower than the Fairchilds but I can't find it now. I measured my .47 ohm resisters at .60 so I just set the voltage across them at .625, slightly higher than the .6 spec'd for use with .47. Unscientific, but they sound pretty good.
Click to expand...

Great, and congrats on the build. Very unique!

Russellc
 
ejfud said:
They are PS Audio binding posts. Bought them from a tip here on AK.
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Where does one find these units? Or do you mean they were pirated from a PS Audio amp? WBT has some that look similar but $$$, and PE has something that looks like that for reasonable. I like the insulation, Being the F-5 without protection circuitry is very sensitive to accidental crossing of leads.

Thanks,
Russellc
 
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specialidiot said:
Gary grabbed his amps from me this afternoon. He's probably still sitting there with his jaw on the floor.
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I hope he has the decency to report back.....:D

cdfac said:
if only those had quadruple the power!
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Easy to do, order the dual output boards from cviller, fill them, and you'll end up with 50w. a board. Use as many boards as you need.

Let me know when you are going to do this so I can buy some stock in aluminum, you are going to need some hellacious heatsinkage.:D
 
Well, I just got lucky....binding postwise, anyway. Just received an email informing me of same, they should be on the way.

A Big Thankyou to ejfud!

Russellc:banana:
 
Russellc said:
Well, I just got lucky....binding postwise, anyway. Just received an email informing me of same, they should be on the way.

A Big Thankyou to ejfud!

Russellc:banana:
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I thought he may be able to help you out. They are a very nice post.
 
Russellc said:
So how are the amps?:scratch2:

Russellc
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They sound real nice in the basement shop. That's as far as they've made it so far. I'll be trying them on the Altec 604's in the listening room hopefully tomorrow and I'll report more than.
 
ejfud said:
I thought he may be able to help you out. They are a very nice post.
Click to expand...

Posts arrived today. Very nice posts. Very heavy, locking Banana plugs, and I love the little bolt on the inside end, no need to solder, nice tight fit.

Thanks again for the tip on these, if anyone else out there needs a set, I can highly recommend these. Transaction was lightning fast, shoot I just inquired a few days ago and noe they are in my hand!:thmbsp:

Russellc
 
specialidiot said:
I still have the final chassis assembly to do. When I get home from work I'll fire it up to get the circuit warmed up for a good 2 or 3 hours before final calibration. I found (with the first amp) that leaving the heatsink in a fins down (copyright Jimmy Buffet) orientation heats things up way more than in Real Life, so I'll lean it against the chassis while it warms, then just lay it down for the calibration.

Once adjusted for bias and offset, then I put the spades on the power connections and hook up the Blue LED before final chassis assembly. I'll probably have both of them playing through my Ohm Walsh 2's by bed time.
Click to expand...

On the Daniels boards, where did you run the leds from?

Thanks,
Russellc
 
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