Resistor types ??? (carbon or metal film)

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Greetings all,

I need some help with resistors.

I recently acquired a Harman Kardon Citation V power amplifier. It was supposed to have been completely rebuilt and in proper working order. However, when I attempted to set the AC and DC balance, it became apparent that something was not correct.

All caps have been changed and the work was done very well.

I started measuring resistors and found several that are far out of spec.

Hence, I've decided to go through it and replace all of the resistors.

My question is, I have no idea what type to choose - i.e. carbon comp, carbon film, metal film, wire-wound, etc. that would sound the best.

I am toying with trying the 1 watt versions of these: TAKMAN - REX 1 Watt Carbon Film Resistor

From what I've read, metal films tend to sound "harder." I really don't want to do this twice if I choose incorrectly. Also, I'm concerned that resistor working voltages might be an issue since this is a tube amp.

I do know Jim McShane offers resistor kits for these amps, but wants $89 for them. I figured that I'd either save some $$ or spend the same amount and get better components for that kind of money. The unit has primarily .5 watt and some 2w units and has about 50 resistors total.

My thought process on using the carbon film was that if the original design also used carbon, it might stay truer to the original sound. I don't know if this thought process is sound, so I decided to ask for some help.

Also, please note the same company also builds a metal film that is non-magnetic. Not married to them specifically, just found them interesting:

TAKMAN - REY 1 Watt Metal Film Resistor

I've also considered using Dales, Mills, Holcos, Yageos or even Rikens. I don't want to toss money down the drain, and am not partial to any particular brand, but would like the amp to sound the best possible. I was tending to lean to non-magnetic types if possible.

Any help/thoughts would be appreciated!

Thanks,

Steve
 
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JMO, pay McShane the money and you are certain to get parts proven to work well. What Jim has forgotten about in "the care and feeding" of vintage H/K Cit. tubed gear, the rest of us are likely never to learn.

BTW, does your specimen have Jim's choke tweak for the O/P tube screen grid supply? That change goes a fair way in improving performance. A stable g2 B+ supply is well known for making full pentode mode "finals" work well.
 
Looking up your TAKMAN brand resistors, I am dismayed at the words used, like "bright","detailed","warmth","natural sounding"...........these 'definitions' are purely marketing ploys for you to drop dollars when you should be spending quarters for your resistors.
Stick with so-called 'common' metal films & you'll be fine. 1% tolerance & packs of two to five will allow you to measure & nail your values.
They used carbon comps purely for cost concerns in the old gear...films will get you less noise especially at the front end.

__________________________________________________________Rick......
 
Step up one size in all resistors to help reduce noise. If the circuit is dissipating .6W and you would choose a 1W MF resistor, go with a 2W one instead. This will help reduce noise. This helps in two ways. (1) it reduces thermal shift of the resistor value (minor effect) and (2) it reduces noise by using a larger cross section of resistive element. It won't address noise that is related to resistor value.

Wire wound tend to be the quietest, but you will only get wire wound in low ohmic values. Metal film is next, then carbon film and carbon comp last. I quit using carbon comp in anything but low end guitar amps (<10W) where some guitar players insist they sound better.
 
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Given the doubts you are experiencing regarding the selection of the resistor types, ratings and the problems in sourcing them (you may be forced to resort to more than one supplier), a kit of parts tailored to your requirements, even at $89, may prove the best solution.

While quarter watt resistors may cost only cents, higher wattage are more expensive, and prices vary from source to source. Simply listing the values, ratings, types, description, manufacturers part number, suppliers part number, number of items, price each and total price is quite a task, without trawling through to discover which part is cheapest where and whether it's in stock.

w
 
Just to be clear, in NO way did I mean to sound negative at all regarding the offerings from Jim McShane. I've bought multiple items from him the past and he's extremely responsive and knowledgeable. I was simply exploring options as $89 for 50 resistors seemed a bit pricey to me.

I also know ZERO regarding tube gear, so I figured I'd ask.

Eli - I don't know about the choke mod. I'll look into it. I was just on Jim's page and wasn't able to find what you're referring to but I'll keep digging. Thank you for the tip!

I paid top dollar for the Citation V because my time is extremely limited right now and I didn't want to have to work on it. In the seller's defense, he did show me the problem with the meter "displaying incorrectly" on one channel once at his home when I was purchasing the amp. He claimed that it'd been that way since he purchased it off eBay. I am simply not comfortable running it as it is because I have no way of knowing how much current the tubes are running at on that channel.

I also have two Citation II's needing rebuild that I was also planning on going through top to bottom. Hence, I thought that I'd see if there was a way to reduce the overall cost a bit. When I start looking at $300 in just resistors between all three from Jim, then add cap kits for the Citation II's at several hundred dollars each, then new tubes for all three, the total cost makes me cringe a bit, as it adds up very quickly.

That having been said, I know this hobby isn't cheap. I was simply trying to see if there was a more economical solution and that started with choosing the best sounding type of resistor for this application.

I'm not new to the DIY audio world and am more than comfortable modding and repairing the amps. I just know next to nothing about tube amps and would rather ask first than make dumb mistakes.

Thanks to each of you for the tips thus far!

Regards,

Steve
 
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Steve,

Cit. 2s and Cit. 5s are worth the big bucks you spend in overhauling. See how much buying equivalent "iron" in today's climate costs. That's truly frightening. Top notch magnetics deserve serving in units whose state of repair leaves nothing to be desired.

Your heirs and assigns, generations removed, will thank you for passing these GEMS on to them.
 
Your heirs and assigns, generations removed, will thank you for passing these GEMS on to them.

Eli,

All I can do is hope!

I can only imagine them being sold at a garage sale because they don't fit with the current fad of flush-mount, in-wall, 50 channel surround sound systems because "they're old."

But, perhaps the person who ultimately finds them at that garage sale, or on the eBay of the future, will love and appreciate them!

I'm still holding out hope for a niece or nephew to get bitten by the audio bug, but we'll see.

I'd take them with me when I go if I could... LOL!

For the record, it does appear that the choke on the V has been changed. I haven't drawn out a schematic of exactly what has been done, but the choke value is the same as Jim lists on his power supply page and that is different from the original Citation schematic. All diodes and power supply caps have also been changed. I don't know if the parts were purchased from Jim but very easily could have been as the mods drilled no new holes. As I mentioned, the completed work is top-notch.

:-]
 
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I have to agree, I'd expect to better these prices, with the input of some effort. The fact that you want 3 sets changes the balance of effort.

Film resistors have a maximum rating independent of their wattage, due to the potential for arcing between coils of the helix. For this reason film resistors must have their voltage rating checked if used as the anode load of a valve.

Just pick modern, cheap resistors of an appropriate wattage and suitable form factor (film in the smaller values) and you'll be constrained in your choice largely to wirewound in the higher wattages anyway. Wirewound types > 10k generally have negligible inductance.

w
 
Just found notes and installation sheets in the paperwork supplied with the amp. It does appear the cap and choke kits were purchased from Jim McShane.

Makes sense as the installation is very clean and the amp isn't all hacked up.

This is good news as it would appear that I have a very good foundation to work from.

Thanks for the comments/help folks, please keep them coming!

Steve
 
I have to agree, I'd expect to better these prices, with the input of some effort.

You have no idea what's in the kit he gets for the money, but you are sure he can buy it cheaper. Amazing!

The Cit V uses a large number of higher wattage resistors, they don't give those away. As well, 18 of the resistors have received parts with increased ratings of at least 1/2 watt, some are increased more than that.

The resistors in the kit are tighter tolerance than the originals, especially in locations where that is most important.

The resistors are not all one type, they are a variety of makes and constructions I've found work quite well together in that amp.

Some resistors have somewhat different values than found on the schematics. These values were selected by a careful process.

No one supplier can provide all the parts. It will take at least 3 to source what's in the kit. That means shipping expense x3 and minimum order issues in a couple cases.

FYI, I put those kits together years ago after receiving many requests from Citation owners. They are a pain in the a** to put together, pulling all these different resistor values/wattages/constructions to assemble them; trying to keep up with the discontinuations, supersessions, and ENDLESS back orders. Go ahead TRY to order all the resistors you need right now - I'll bet 20% are back ordered. Of course I have them all in stock, but I'm not CHEAP enough. I actually ask for a little compensation for all the effort and expense to have these parts available in one place for rebuilders of these great amps.

If you are trying to go cheap, Citation gear isn't for you.
 
Jim,

Understood.

Like I wrote to you, it was NOT my objective to offend in any way and I apologize if I have!

No, I haven't tried to track down all of the individual values. I was simply taken a bit back because I'm used to standard small metal films not costing very much.

That having been said, the very first place I went to source them was your page because I remembered you offered kits and I KNEW you would have chosen very carefully.

No, I don't object to you being compensated as well you should be!

Like I wrote, on the surface, once I started looking at doing 3 amps, it seemed to be adding up quickly. Hence, the questions.

I also wasn't aware that you'd tweaked values from the original design to improve performance but it certainly makes sense that you would have.

Like I mentioned above, I'm new to the tube world. I am not used to the voltages, larger resistor sizes, or where exactly they make the most difference in the sound. I don't have an unlimited budget; hence, I am trying to maximize the bang for the buck.

For some reason, I thought I had read someplace that they had a choke. I appreciate the clarification.

Thanks for your input!

Regards,

Steve
 
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Apogee, unless you are rebuilding phone pre-amp, you can use any of metal film. metal oxide, carbon oxide or carbon composition. Wire-wound are fine for power supplies but not for signal path.

There is one thing to watch, however - 1K 1W vintage resistor doesn't necessary equal to the modern 1K 1W. Today's resistors are MUCH smaller, and may have LOWER maximum voltage rating. For 99% solid-state devices it doesn't matter, but for high-voltage tube equipment this parameter is absolutely essential, otherwise you may end with arcing/burning parts after all. So even if your schematic states 1K 1W, you may still have to order 1K 3W to comply with voltage requirements. If you are keen to shop resistors for yourself, do the following. Write the list of resistors with wattage and approx voltage requirements, go to digikey.com (they have voltage rating in description field). It will take a LOT of time, however.

IMHO, if you are rebuilding your first amp, I would suggest to buy parts from Jim. Yes, you can order resistors for $3 per 100 pcs from China (100 pcs is min order qty), use a couple of them, and keep the rest 98 for collection. So the "useful" part of this purchase still will be $1.5 per pc.

The price for parts you pay is actually a small part of service provided by Jim. His technical advices and expertise often are absolutely invaluable. Confirmed by my own experience!
 
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Film resistors have a maximum rating independent of their wattage, due to the potential for arcing between coils of the helix. For this reason film resistors must have their voltage rating checked if used as the anode load of a valve.

w

I'd be very wary on this: Recent bench testing a 50W amp threw me out: mysterious unexplained anode current variations. Fault: Dont' use cheap low ohmage metal film/oxide resistors for the cathode current sense in amp output stages. Although x4 overrated; the film & oxide resistors have very poor impulse properties. Both these resistors in the pic (left +centre) have been impulse strained and read wrong values and yet not a single scorch mark can be seen.
The solution in this amp example is use a Dale 10R 2-3W wirewound (on the right) available from Mouser.
I wouldn't go haphazard about using cheap film types for criticial positions. One could be looking for a fault quite soon after fitment. A hefty transient spike from a fridge or another appliance is quite enough to punch oxide and film resistors.

richy
 

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You have no idea what's in the kit

On the contrary, Jim, I know exactly what's in the kit; resistors.

Presumably you don't sell them at a loss? Then with some effort I could source them cheaper than I could buy them from you.

I'm not attacking you, or your livelihood. My original suggestion was that he buy the kit, please note my earlier post. I am well aware of the effort involved in compiling such and buying it from multiple sources, but he wants 3 kits, and as the number of repeats increases so the balance of economics changes.

I have an obligation to encourage other correspondents in their efforts to make judgement calls. By all means intervene to point out benefits of your product which you feel may not have been adequately represented, but please do not attack me for making the assumption that capitalism has not ceased to function. It hasn't has it?

w

Thinking about cyepitalism, and all that, there'll be a discount for 3 kits, won't there? Spasiba, tovarich...
 
I'd be very wary on this: Recent bench testing a 50W amp threw me out: mysterious unexplained anode current variations. Fault: Dont' use cheap low ohmage metal film/oxide resistors for the cathode current sense in amp output stages. Although x4 overrated; the film & oxide resistors have very poor impulse properties. Both these resistors in the pic (left +centre) have been impulse strained and read wrong values and yet not a single scorch mark can be seen.
The solution in this amp example is use a Dale 10R 2-3W wirewound (on the right) available from Mouser.
I wouldn't go haphazard about using cheap film types for criticial positions. One could be looking for a fault quite soon after fitment. A hefty transient spike from a fridge or another appliance is quite enough to punch oxide and film resistors.

richy

This is a real issue with film resistors and the reason "Surge Rated" resistors exist. They are considerably more expensive than non "Surge Rated" resistors and much more difficult to find. Wire wound is a good alternative in low ohmic values (lessthan 1K?).

I think these are refered to as "Flameproof" in through hole types. They are the only ones I see a surge rating for. Yaego rates theirs for pulse overload 4 RCWV.

I'm used to surface mount parts and the reatings for them are different.
 
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This is a real issue with film resistors and the reason "Surge Rated" resistors exist. They are considerably more expensive than non "Surge Rated" resistors and much more difficult to find. Wire wound is a good alternative in low ohmic values (lessthan 1K?).

I've read that wire wounds are not good to use in the signal path.

Is this bunk or accurate?

This is exactly why I was planning on upsizing whatever I purchased if I did my own "kit.'" If one considers the 1 watt or larger units, the working voltages jump up considerably above what they will ever see in the amp.

One other brand I was considering was Kiwami:

kiwame resistor page

Thoughts?

Thanks,

Steve
 
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