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Just a couple of F5 build questions...

cdfac

cdfac

AK Subscriber
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There have been so many good build threads here I don't feel the need to start my own, but I do have a few questions that other less-experienced builders might also have.

For reference, here is the "kit" I just bought, which I received in the mail today:

http://www.diyaudio.com/forums/swap-meet/191715-fs-parts-f5-build.html

229196d1309309323-fs-parts-f5-build-f5-parts_1.jpg


I've been told these are both CVILLER boards (the audio board is version 1.1 from 2010, but the PS board wasn't labeled at all). For starters, I'm going to buy HEXFREDs to replace the regular bridge rectifiers that were included, but it looks like the setup is otherwise pretty complete. I guess I just have three main questions so far.

1) Do you think the 6" tall version of this heatsink (one per channel) will be enough for the 25Wpc build? Note that the fins are 2.5".

http://www.heatsinkusa.com/products/10.080"-Wide-x-6"-Long-Heatsink.html

2) I had two 0.0033uf/400v film caps included, supposedly for the power supply -- what are these for?

3) Are the Toshiba outputs really worth the extra $30+? If you could elaborate a bit more on this topic, that would be great. Or, if only a "yes" is necessary, that's great too.

TIA!
 
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Looks like you're off to a great start! I would strongly suggest maintaining this as a build thread. You never know when you get tied up with life and then when you get back to the amp you forget where you were. Happened to me once or twice.

1. As for the heatsinks, I bought those same exact ones you are looking at except in 7" x 10.80" and they work just fine. :thmbsp:

2. Not sure what those caps are for. Bypass caps maybe?

3. Mine is built with the original Fairchild so I can't help you there. Specialidiot has built his both ways with fairchilds and toshibas so he can help you more with that question.

One thing I would do differently is buy the chassis prefab. It took me a loooooooooong time to cut, drill, powdercoat and assemble the sucker. Much more time then I spent actually working on the electronics and in the end the cost wasn't much different. I do like the look I ended up with on mine though.

Also, those are daniels power supply boards, the amp boards are cvilers.
 
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is there a prefabbed chassis that would work well with these sinks?

westend has agreed to help with the chassis, starting with only the heatsinks.... i did find a newly-introduced Par-Metal prefabbed high-power amp chassis on eBay for a reasonable price, but both westend and specialidiot were concerned that there wasn't quite enough sinkage. i know that it would be possible to buy a non-sinked Par-Metal chassis and retrofit their sinks over the side panels, but this would involve cutting through those side panels to mount the MOSFETs, and the expense begins to add up quickly.
 
cdfac said:
is there a prefabbed chassis that would work well with these sinks?

westend has agreed to help with the chassis, starting with only the heatsinks.... i did find a newly-introduced Par-Metal prefabbed high-power amp chassis on eBay for a reasonable price, but both westend and specialidiot were concerned that there wasn't quite enough sinkage. i know that it would be possible to buy a non-sinked Par-Metal chassis and retrofit their sinks over the side panels, but this would involve cutting through those side panels to mount the MOSFETs, and the expense begins to add up quickly.
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If westend has agreed to help I'd go that route for sure. He made a chassis for my B1 and its fantastic and he didn't charge much for it either.
 
Another question I meant to ask, about ordering matched Toshibas. How do I choose Vgs? Here is what is available right now from a reputable DIYAudio seller:

http://www.diyaudio.com/forums/swap-meet/161366-matched-toshiba-fets-sale-47.html#post2639633

If someone with relevant knowledge could tell me exactly which pairs to buy, that would be great! At the very bottom are dual-matched pairs, which I think I am probably interested in, but again the Vgs thing has me confused.
 
Chris, my understanding is that matching pairs with VGS is not all that necesary if using only one pair per channel. It is when you are building a balanced version or have two pairs per channel that VGS becomes important.

Nelson has this published about matching devices.
 
My F5 was built with a pre-fab'd enclosure and Conrad heat sinks. Cutting the side panels to accommodate the heat sinks was trivial - just a couple of minutes with my dremel. Another 30 minutes or so to drill and tap some holes to fix the sinks to the side panels and I was done. It's not rocket science - just mark some holes and get busy.

I kept reading about the Toshiba outputs and their sound signature was something that interested me. I didn't do anything about it until Gary's build, where I also used the HEXFRED rectifiers.

I did an A/B with all other components exactly the same, and Gary's monoblocks exhibited a punchier bass and played better with the horns in my Cornwalls. So I built new boards using Toshibas and updated my rectifiers to HEXFREDs.

Gary's monoblocks with my F5 in the middle, using a Yamaha C-2x for pre, driving Cornwalls

f5trio.jpg
 
As a past wannabe-Rocket Engineer, I resemble that remark.:D

BTW, what did you use for spacers for the top plate on Ray's F5?
 
My office is across the hall from some rocket engineers, you don't want to be like them.

For spacers, I just bought some while nylon jobs and hit them with some rattle can paint.
 
Those .0033 caps are line caps...if you look at the power supply schematic on the Firstwatt site, you will see them in the power line.

Russellc
 
I only see two Cl-60 thermistors, you'll need three if you want it just like its shown on the Pass site...6 for dual mono.

Russellc
 
I've just been a little slow to order the chassis -- I'm going to have Par-Metal do a custom jobby for around $190 and Lance will help with punching the holes. I'm going to order the HEXFREDs and binding posts from P-C tonight, I think. And I got a little care package from Jeff today -- Toshiba outputs, extra Toshiba drivers in case I have any problems with mine (my J74's are GR, which I understand is not as ideal as BL), an IEC jack, and some LEDs.

I figure I could have this thing running in a month, possibly.
 
Russellc said:
Those .0033 caps are line caps...if you look at the power supply schematic on the Firstwatt site, you will see them in the power line.
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got it, i'll take a look.

I only see two Cl-60 thermistors, you'll need three if you want it just like its shown on the Pass site...6 for dual mono.
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they're all there, just checked.

speaking of the power supply, has anybody been putting film bypass caps over the filter caps? also, what the heck is the point of putting those four 0.47R resistors in between the positive filter cap terminals? i don't think i've seen that before in any of the power supplies i've worked on where each rail has multiple caps in parallel.
 
specialidiot said:
What are the odds on Chris finishing before Wil?
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marantzfan said:
I'm just glad I don't have a horse in that race anymore. :D
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cdfac said:
I figure I could have this thing running in a month, possibly.
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I will do everything I can to make sure you win the race. :D Actually, I have a nag in the gates, too.:scratch2::sigh:

cdfac said:
..........speaking of the power supply, has anybody been putting film bypass caps over the filter caps? also, what the heck is the point of putting those four 0.47R resistors in between the positive filter cap terminals? i don't think i've seen that before in any of the power supplies i've worked on where each rail has multiple caps in parallel.
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I haven't seen but a couple using bypass caps in any of the PSU's. My suggestion would be to keep it simple, initially.
The resistors are part of the CRC circuit, the design of the power supply. I believe you have a P Daniels PS board, right? I looked at the pictures of your buy and noticed it wasn't a C Villers board.
 
westend said:
I haven't seen but a couple using bypass caps in any of the PSU's. My suggestion would be to keep it simple, initially.
The resistors are part of the CRC circuit, the design of the power supply. I believe you have a P Daniels PS board, right? I looked at the pictures of your buy and noticed it wasn't a C Villers board.
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ok, easy enough to skip the bypasses.

CRC, yeah, i've heard of that now that i think of it. i assume it provides some kind of filtering or rejection that you wouldn't get by putting those caps direction in parallel.

i don't know what kind of board the PS is. it looks the same as Sir.Byrd's, i think.

bad news, kind of. i just got an email and P-C is out of the 27A now as well, apparently, so i'm probably going to bump up to the 68A. that's fine, just an extra $7 or so in the end.
 
You guys better take it easy on Will and the rest of us NW folk, we've been in a mini ice age which slows down all activity. Article in yesterdays paper said a weather type person did calculations/programming that resulted in us having a total of 78 minutes of 80 degree or higher(ha!) temp this summer.:thumbsdn:

But after seeing what the eastern US is going through, maybe it isn't soo bad after all.:scratch2:
 
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