The "Holy Grail" of resistors?

[George61]

I have just started my third build, an 18W tremolo, and I have enough experience that I am now, probably, one step beyond a rank amateur.

I can't decide what I want to use for the 1/2W resistors. I was going to use all 1W Xicon carbon film resistors but I know there are spots where people use 1/2W carbon composition. I believe the 100K's on the PI plates is one of them.

I am open to, and would appreciate, any suggestions. I would have posted this inquiry on 18watt.com but I am afraid that zaphod_phil would reply.

Solder on,
George

[M Fowler]

Now that was funny, ZP never like me much!

Do you have Merlin's preamp book? I think he makes suggestions in their I'll see if I can find the info unless someone beats me to it.

[dave g]

1 watt xicon carbon film are fine.

In general with respect to resistors, I would like to see anyone who claims they can hear a difference pass a double blind test.

[echuta13]

I guess it depends on what you are going for.

I use 1 watt cf's for the majority of work. They're cheap (like me!), and decent (not like me). I generally use a metal film resistor anywhere in the signal path and on the plates to keep the noise floor down (especially in the first stage). Carbon comps are for color , but I'm not really sold on that. If you're going to use them, I would suggest on the plates of the phase inverter perhaps.

I suspect that dave is right and that you probably would have a hell of time telling the difference between any of them. It's just mojo, and I wouldn't sweat it too much. My $.02 is just use the CF's everywhere.

[gldtp99]

1 watt xicon carbon film are fine.

In general with respect to resistors, I would like to see anyone who claims they can hear a difference pass a double blind test.

I use a lot of Xicon carbon film resistors---- 1/2 watt and 1 watt-----last night a talented Jump Blues player demo'd an amp i'm building and said it's the best sounding amp he's ever played----and this amp has Xicon carbon films in most positions----- It's a 40 watt, 6L6GC x 2 version of the BF Princeton circuit---- But it has the additional Reverb Recovery gain stage (but no reverb) and a Raw control, and my tweaks------ built inside a 1950's Stromberg-Carlson AU-33 PA amp----- gutted and rebuilt with all new parts--- it's a fun to play amp-- ..............................gldtp99

[Structo]

Not sure if it is true but I have read more than one time that the larger wattage resistors have less noise than a smaller resistor of the same value.

We are talking carbon film here.

Plus the larger size is easier to work with.
Longer leads.

[M Fowler]

Regarding CC resistors here is a Marshall board showing where to use them.

[dcribbs1412]

Thanks Mark
I have not seen this before

Darin

[George61]

The official, definitive, etched in stone, actual choice is a matter of builder preference, list of resistors I found on 18watt.com. Looks like a plan to me since I don't really have one.

Solder on,
George

[Mark]

The trouble with carbon composite resistors are noisy as previously mention, they drift in value which is a bit of a pain as there is no telling if the drift will go your way.

As far as resistors go there are lots of choices.

http://angela.com/resistors.aspx

http://www.partsconnexion.com/resis_main.html

[Turret]

Regarding CC resistors here is a Marshall board showing where to use them.

Is there any theory behind this?

[roberto]

Not sure if it is true but I have read more than one time that the larger wattage resistors have less noise than a smaller resistor of the same value.

Yes, here you can find a deeper explanation: http://www.aikenamps.com/ResistorNoise.htm

[Roe]

For a plexi, I prefer piher and iskra CF and a few AB CC

[rp]

The trouble with carbon composite resistors are noisy as previously mention

This has not been my experience. Can they become noisy down the road? Sure but in my new builds all I get is minimal background 'tube rush'. I really doubt I could get the amps quieter with cfs or mfs.

In general with respect to resistors, I would like to see anyone who claims they can hear a difference pass a double blind test.

One here and there I'd agree. But shotgun an amp from cc to mf and I sure as heck can here a difference. As for cf to mf, I never tried, but it'd prolly be minimal.

[Ken Moon]

I like resistors that are small and have the value written on them - my old brain gets tired reading color codes.

So I use a lot of the KOA/Speer 2W MFs (the green ones in this pic), IRC 3W MFs (small black ones), and Mills power resistors (5W for B+ dropping resistors across the top, and 12W cathode bias resistor next to the last cap on right):

[img761]http://i514.photobucket.com/albums/t346 ... 2board.jpg[/img]

I have used big old 3W CCs for grid stoppers on the power tubes, because they're supposed to work well there, but to be truthful, I can't hear any benefit.