Which Resistors CF or MF

[bnwitt]

Ok, I'm in the process of ditching CC resistors and restocking my shop with a quieter longer lasting resistor type for my amp builds.  I am currently thinking of going to 1 watt metal film for all signal resistors and metal oxide for power resistors.  I've been using MO for power resistors for many years now and carbon film for signal circuit recently but their noise floor (while less than carbon composition) is still pretty high for my taste.  The only down side I see to the metal film 1 watt is the available values.  It seems like a few are missing in that wattage range.  Carbon film has metal film beat in that area but would the noise of 1 watt CF resistors be low enough for a really quiet dimed amplifier.  I'm interested in opinions and what everyone one else is doing on new amps.  Thanks in advance for your feedback.
Barry

[davidwpack]

I just bought an assortment set of 1750 pieces of mf resistors for $16. I haven't used them yet but will on my next build. There are a few missing values but I'll buy those individually. I'm not sure which type yet but I wouldn't think it would hurt to mix resistor types.

[sluckey]

I am currently thinking of going to 1 watt metal film for all signal resistors and metal oxide for power resistors.

+1

[dpm309]

I recently changed all of my 1/2 watt CC resistors in my 5F6A Bassman clone with 1/2 watt MF resistors and am pleased with the noise reduction. Still getting the same great sound out of it. Are 1W resistors an overkill for the signal resistors?

[bnwitt]

Are 1W resistors an overkill for the signal resistors?

Yes.  But as I understand it, contact noise in a larger resistor is going to be lower than in a smaller resistor per a specific current hence my choice to go to 1 watt instead of 1/2 watt.  Someone can correct me if I'm wrong.
Barry

[bnwitt]

I just bought an assortment set of 1750 pieces of mf resistors for $16. I haven't used them yet but will on my next build. There are a few missing values but I'll buy those individually. I'm not sure which type yet but I wouldn't think it would hurt to mix resistor types.

I did that quite a few years ago and I've still got a bunch of odd (not used in tube amps) values I'll probably never use but I'm have low on quantities of the ones I use in the amps I build.  I just went and purchased (6) Plano 3700 storage boxes and my plan is to reorganize my MF 1 watt resistors putting only the amp value resistors into the new bins and leaving the odd values in their current bins.  It should save me lots of time searching the bins for what I need when building an amp
Barry

[bnwitt]

I recently changed all of my 1/2 watt CC resistors in my 5F6A Bassman clone with 1/2 watt MF resistors and am pleased with the noise reduction. Still getting the same great sound out of it.

And that is what I am finding as well.  The MF resistors are much quieter when an amp is turned up loud with no signal input.  The quiet on idle effect.  The last HDR that went out the door was almost all CC and when you dialed the volume up to 8 or above you could hear more noise than I like to hear.  I'll be comparing this next one to that one with the owner to see if the difference is a good thing.
Barry

[tubenit]

On higher gain amps, I have started using the Vishay Dale RN65 metal film resistors and like them.  I think they're pretty quiet.

with respect, Tubenit

[bnwitt]

On higher gain amps, I have started using the Vishay Dale RN65 metal film resistors and like them.  I think they're pretty quiet.

with respect, Tubenit

Thanks for the recommendation Tubenit

[Willabe]

On higher gain amps, I have started using the Vishay Dale RN65 metal film resistors and like them.  I think they're pretty quiet.

I've been using these also and really like them.

Some of the MF resistors have very thin diameter leads and I don't trust them. The RN65D's have a thicker lead.
 

[pompeiisneaks]

And for general info, RN65's are a milspec type of resistor with higher spec requirements, so generally better build quality etc.

~Phil

[bnwitt]

Well it does not appear that the RN65 resistors are available in 1 watt version.  If I'm going with 1/2 watt I will just buy what Doug sells as those are just fine with me.

[Willabe]

IMO, Doug's R's are a very good choice.

But for the Dale R's, I believe the .5w (1/2w) rating is underrated for the military rating.

The bodies are very close to 5/8" x 3/16", that's big for a MF .5w R.
 

[PRR]

> RN65 resistors are {not} available in 1 watt

RN70 used to be the 1 Watt job, but for military work is now rated 0.75W.

The commercial equivalents may have higher ratings.

https://www.vishay.com/docs/31027/cmfmil.pdf

The usual 100K plate resistor lives at less than 1/4W. The main reason to over-over size is for the occasional tube short, when it may rise to near 1 Watt. (Also because the cost difference is negligible in DIY economics.)

[EKDENTON]

If you use the metal film resistors that you can not make out the color bands something like in the photo below, to keep them organized sure helps. Otherwise if your like me you have a pile of loose resistors in your parts box when your done with your amp to go through one at a time and check with a meter. LOL

[purpletele]

If you use the metal film resistors that you can not make out the color bands something like in the photo below, to keep them organized sure helps. Otherwise if your like me you have a pile of loose resistors in your parts box when your done with your amp to go through one at a time and check with a meter. LOL

That's a pretty cool idea!

[bnwitt]

Well I've been using plastic bait storage bins for a long time to keep my parts organized.  Even so, sometimes an errant part jumps into the wrong compartment so everything gets checked by my BK Precision 878 meter when it comes out of the bins.  I didn't follow that rule on the last HDR and got an incorrect resistor value in the tremolo circuit.  Learning the same lessons over and over again it seems.  I was using the Shimano parts bins but I've switched over to the Plano 3700 Pro Latch units as the latches are much easier to open and close.  Plus you can get them in a 4 pack with a rack holder too.

http://www.tacklewarehouse.com/Plano_Pro_Latch_Utility_Box_3750_/descpage-PPLUB37502.html

[MFowler]

I've been finding old MF resistors for my Dumble builds but it's drying up fast.  Heck finding 1w 110K this week has been a bitch.


Mouser is hit and miss too.


Attached two photos of the old MF resistors I look for.


Mark

[bnwitt]

Yep, I'm getting a bit frustrated trying to find 1 watt MF in all the values I need.  It looks like I'm going to end up going with 1 watt C.F. resistors as my stock resistor.  The 1/2 watt MF and CF are just to flimsy for my taste hanging off of turrets.

[kagliostro]

I use 2W MF, they have the right measure for turret and eyelet board, and ........

I can see it using my glasses and without the use of a magnifier 

the more, bigger resistors are less noise sources

Sometime is hard to find all the values I need, but on ebay I place orders to China sellers

and there I can find (at very low price and often 1% tollerance) all the values I want

Franco

[bnwitt]

Thanks Franco.  I'll check 2 Watters out on the bay.  I'd rather buy them from Doug if he stocked them.

[jojokeo]

Just throwing out some general helpful resistor knowledge seems appropriate?
Quietest to noisiest:
1) wire wound
2) metal film
3) metal oxide
4) carbon film
5) carbon comp

Positions of importance: low level or input stages, plate/load, grid to ground, and divider/attenuation areas.

[kagliostro]

If Doug didn't sell it

here is one of the possible sources for 2W MF resistors

http://www.ebay.com/itm/20Pcs-2W-2-Watt-Metal-Film-Resistor-1-1K-910K-Ohm-1-K-910-K-Free-Shipping-/192110365581?var=492013624748

and here one for 100W (aluminium case) Dummy Load Resistors

http://www.ebay.com/itm/1-2-4-8-10-Ohm-100W-Watt-Shell-Power-Aluminum-Housed-Case-Wirewound-Resistor-New-/141957695607?var=&hash=item210d568877:m:mTihmKm-hBqIO03-aYwyRmw

Franco

[bnwitt]

Thanks fellas

[PRR]

> Quietest to noisiest: 1) wire wound 2) metal film 3) metal oxide 4) carbon film 5) carbon comp

I would simplify.

The wire/metal/c.film types are all so close that I would worry more about color and size than ingredients.

Carbon Composition "can" be not-too-bad, or can be awful, especially with age and heat. OTOH CC is historically 1/10th the price of the others, so all our gear from 1920s well into 1980s uses this type, and it may have a "sound", which we may be accustomed to.

[bnwitt]

> Quietest to noisiest: 1) wire wound 2) metal film 3) metal oxide 4) carbon film 5) carbon comp

I would simplify.

The wire/metal/c.film types are all so close that I would worry more about color and size than ingredients.

Carbon Composition "can" be not-too-bad, or can be awful, especially with age and heat. OTOH CC is historically 1/10th the price of the others, so all our gear from 1920s well into 1980s uses this type, and it may have a "sound", which we may be accustomed to.

Yep.  My biggest complaint in the last 20 years with CC resistors has not been the noise but the drifting of their values way up over time.  I want my products to hang in there for a long period of time after they go out the door.  I'm almost done with this second HDR which has all CF/MF/MO resistors compared to the last one which had a lot of CC resistors and I'm really anxious to see if there is a big difference in the noise floor (the DR not being a high gain amp) between the two amps.  The first one is reaping all kinds of praise so obviously it sounds great now.  If this one sounds great too, then I'll probably end up using 1 watt CF resistors as my main type with MO resistors for the higher wattage needs.

[purpletele]

> Quietest to noisiest: 1) wire wound 2) metal film 3) metal oxide 4) carbon film 5) carbon comp

I would simplify.

The wire/metal/c.film types are all so close that I would worry more about color and size than ingredients.

Carbon Composition "can" be not-too-bad, or can be awful, especially with age and heat. OTOH CC is historically 1/10th the price of the others, so all our gear from 1920s well into 1980s uses this type, and it may have a "sound", which we may be accustomed to.

Yep.  My biggest complaint in the last 20 years with CC resistors has not been the noise but the drifting of their values way up over time.  I want my products to hang in there for a long period of time after they go out the door.  I'm almost done with this second HDR which has all CF/MF/MO resistors compared to the last one which had a lot of CC resistors and I'm really anxious to see if there is a big difference in the noise floor (the DR not being a high gain amp) between the two amps.  The first one is reaping all kinds of praise so obviously it sounds great now.  If this one sounds great too, then I'll probably end up using 1 watt CF resistors as my main type with MO resistors for the higher wattage needs.

Are you putting your amps into a combo or a Head Cabinet?  I think I am going to put my Deluxe into head cabinet. 

[bnwitt]

I'm putting all of my amps into combo cabinets except the Marshall 2204 I'm building.  I'm using nylon stand offs on the Turret boards and the last amp was totally silent with a viloent chop sticking attack so I think we're ok.  I also put a foil shield on the bottom surface of the cabinet top.

[Sonny ReVerb]

I generally use CF, but I just bought some Xicon MF because I needed an odd value: 510k. When they arrived, I measured them with my meter and they were not even close in value. Most were less than 470k. 1% tolerance - I think not.

[Joel]

Years ago I worked in an avionics workshop repairing circuit cards for various F-18 boxes (armament computer, flight control computer, and a small host of others).  Many resistors were CC types, and had been stored un-sealed in un-airconditioned warehouses for years.  Consequently they were often quite far out of tolerance (5% in this case).  We used to bake them in an oven (mil-spec oven no less) at 80 degrees celsius overnight.  More often than not, this treatment would bring them back into tolerance (by baking the moisture out).  BUT, they quickly drift out again if not coated in some sort of conformal coating to prevent moisture ingress.  Once coated, they can stay in tolerance for quite some time.

[bnwitt]

That makes me wonder why the industry didn't coat the CC resistors as part of the manufacturing process.  Of course if I follow that process on my resistors in my home oven, my amps might smell like bacon or banana bread.   Well I have some conformal coating I use when building microphones so I'll give that a try and see what happens to the pre and post values.  Thanks again Joel.