F5 Parts recommendations

[Brian Kingsbury]

I'm about to start building an F5. Since this design is so low on both parts count and overall cost I'd like to spend the little bit extra it costs to get some nice quality resistors (what's another $20 anyway?). I imagine since so many people have completed this amp already there's quite a few BOM's floating around that could point me in the right direction. Preferably ones that will fit into the PCB's without too much monkeying around. Oh and I haven't ordered PCB's yet so feel free to make your recommendation for either pcb that's available.

So, what's in your F5?

[Beftus]

Peter Daniel sells top notch quality F5 PCB's, but bear in mind that Peter designed the PCB with miniature resistors in mind. My F5 PCB's are stuffed with 0.6W resistors that are too large to be lying flat on the PCB surface. If money isn't an issue, Vishay/Dale CMF-55 resistors are quite popular.

[Brian Kingsbury]

Which resistors would be the most beneficial place to put high quality parts? I assume R9, R13 and R14? I'd rather spend my money for some "boutique" parts where it counts the most and stick to more budget oriented parts in non-critical parts of the circuit.

[sangram]

The Vishay S102 should fit the Peter Daniel PCBs just fine, they are ~$20 a pop. I think PD had a picture showing his build with Caddocks.

In such a simple circuit, each and every component is pretty much in the signal path.

The current limiting and thermal compensation circuits may not need to be exotic (though some have reported better results with them removed altogether).

Here's mine, with the PD PCB and the Tech-DIY kit. I had to solder the bigger resistors on the back, but it's OK for my proposed layout for this set.

[Brian Kingsbury]

Originally Posted by sangram

The Vishay S102 should fit the Peter Daniel PCBs just fine, they are ~$20 a pop.

I think I saw them for <$10 for some smaller values. $20 sounds right for the bigger ones though.. It's kind of ironic that you can buy EVERYTHING to stuff a stereo set of PCBs for $20 .. or just one resistor for $20.

In such a simple circuit, each and every component is pretty much in the signal path.

That was what I was alluding to in my previous post when I asked which resistors were the most beneficial to spend money on. I figure someone with more knowledge than myself can make a recommendation on which ones will show the most improvement

The current limiting and thermal compensation circuits may not need to be exotic (though some have reported better results with them removed altogether).

I'm not using those in my build so no prob there.

[alazira]

Hi,
I built an F5 with cviller's board, tech-diy kit and panasonic power caps. Since seeing Peter Daniel's build I've wanted to do something similar and have been collecting mid-grade parts: caddock resistors ($3-$7), vishay metal-film 5K trim ($8 mouser or michael percy) and mundorf caps from parts connexion (the $18, not $80 ones).

I agree that the gate resistors R9, R13 & R14 are the most critical, followed by the feedback R5-R8, R1 & R2, then power/bias R11/R12, P1/R3 & P2/R4, and least important is the ground reference R10.

[Tea-Bag]

I like PRP parts typically in the signal path. There is no doubt that Caddocks also sound good in about any circuit, but they are not worth the price to performance value IMO.
I use mills MRA-5's for the source resistors as well.

[alazira]

Originally Posted by Tea-Bag

I like PRP parts typically in the signal path. There is no doubt that Caddocks also sound good in about any circuit, but they are not worth the price to performance value IMO.
I use mills MRA-5's for the source resistors as well.

I may agree with you in the end if I don't hear any improvement. However, like it's been said, there are so few resistors in this project that upgrading just the gate resistors (6 resistors = $30) might be worth a try. I'm spending more by going dual mono since I have to get 2 transformers, which perhaps will make even less difference. Finding out will be the fun part.

[Damon Hill]

Vishay bulk foil resistors can be found on EBay by searching for "RNC90Y", "S102c", or "Vishay bulk foil"; most can be found for lots less than $20. The tighter the tolerance of any metal film or wirewound resistor the better; the temperature coefficient has to be correspondingly better and that seems indicative of sound quality. 100ppm is pretty standard--the best Vishay z-foils are less than 1ppm. RN55E resistors have a tighter tempco than the usual RN55s, and Dale PTC resistors are among the best, but rare.

Another good source for quality resistors is: http://www.surplussales.com/ They list resistors with ppm tempcos that the search engines can isolate, and have quite a few Vishay foil resistors for around $4 to $7.

Also have a look at: http://www.percyaudio.com at his selection of resistors. The Vishay VSH series foil resistors are significantly less expensive than the S102C types, but I think his stock is limited.

I consider the bulk foil resistors to be the best resistors, period. Not just the very, very low tempco, but virtually non-existent voltage coefficient as well. Too bad they're so expensive.

Agreed that a good and affordable metal film resistor is nice, just trying to decide how "good" is "good enough" for a given budget. I like to think that .1&#37;/25ppm types should rank as "better".

[calvinhpk]

anyone tried Ohmite Little Demon OD series resistors?
are they good quality resistors?