Hi everyone,
I have stash of H4P resistors and I am thinking of using them for my latest tube amp project. I have never used them before but a few people have said on the web that they are unreliable and can let go at a 100V drop. (This was only one source)
The spec sheet suggests 500V.
Anyone have a similar experience? I don't want to put them in my amp and then have them let go left and right a week later. If they are no good Ill have to get something else because that is all I have.
Thanks
Matt
I have stash of H4P resistors and I am thinking of using them for my latest tube amp project. I have never used them before but a few people have said on the web that they are unreliable and can let go at a 100V drop. (This was only one source)
The spec sheet suggests 500V.
Anyone have a similar experience? I don't want to put them in my amp and then have them let go left and right a week later. If they are no good Ill have to get something else because that is all I have.
Thanks
Matt
Hey there,
unless Holco is a very unreliable manufacturer (don't know them), the stated specs should be reached - though it might be wise to not stretch them to the outermost limits.
If spec sheet says 500V, I would use them up to 400V maybe, depending on criticality of their duty, power dissipation and other boundary conditions.
Greetings,
Andreas
unless Holco is a very unreliable manufacturer (don't know them), the stated specs should be reached - though it might be wise to not stretch them to the outermost limits.
If spec sheet says 500V, I would use them up to 400V maybe, depending on criticality of their duty, power dissipation and other boundary conditions.
Greetings,
Andreas
The best resistors for a tube amp are metal film or bulk metal foil.
FYI nobody has produced an audio resistor quieter than bulk metal foil. It's the ultimate.
FYI I highly recommend that you use 1 watt for plate and cathode resistors, and 1/2 watt for the signal path...
(use metal oxide for the power supply drops)
Carbon resistors (i hate to break the news to you) are GLUED together. The leads are glued in.
The glue can break down, causing noise and crackles....or failures.
On the other hand, metal film resistors are welded together with a laser. This is why they are much quieter...and much less prone to failure.
NON INDUCTIVE is the way to go. parts in the circuit can act like antennas for 60 cycle fields, like the heater wires...
ALSO silver mica capacitors, instead of ceramic disks, will keep your noise and hum way down...
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Am I a little slow this morning or why do I not see the connection between that post and the OP's question?
The Holcos in question *are* metal film resistors - and Matt simply wanted to know if he could use them. So why arguing about carbon resistors, mica caps and all that stuff?
Greetings,
Andreas
Do you have references for that?
As far as I know, the only thing done on metal film resistors using a laser is the structuring of the resistive element.
The end caps are usually simply pressed on the ceramic base, the leads are welded to the end caps using conventional welding methods.
Greetings,
Andreas
Perhaps you should read the post again.
I never argued, I just provided the information.
So the conclusion you could draw is,
If the Holcos are metal film, then you are doing pretty good.
The only thing better is bulk metal foil.
Hmm.. Maybe, but only if the known dissipation requirements of the circuit are lower than those figures. They can easily be higher in some designs.
Generally speaking, many manufactures are using 1/2 watt or 1/4 watt, carvin is using, or has used 1/8th watt.
It's better to use, as you infer, oversized resistors.
With the voltages usually present in tube circuits, I wouldn't use 1/4W or even less due to the small sizes of the resistive element and the resulting low voltage ratings, though some manufacturers (the ones you named) seem to do so...
If no higher dissipation rating is needed, I use 1W 1% or 2W 5% metal film resistors per default. These are readily available and reasonably cheap.
Greetings,
Andreas
I gotta agree, I would rather use 2W than 1W...
But I don't want to listen to the critics who say that 2W is "unnecessary." For me, it is.
There's a lack of 2W metal film, it's not so easy to buy that fast, I gotta wait for them. So I settle for 1W.
+1
With resistors it's more about power dissipation than voltage tolerance; that's more of a capacitor issue.
Voltage rating for resistors is more about body length (length between the leads) to ensure enough creepage distance to prevent flashover.
For instance if you are going to use a resistor to bleed a power supply capacitor in a tube amp with a 450V rail; a 500V part would probably be marginal. Use two in series to double the body length; each of half the value you need and make sure that you are within the dissipation limits of the part. H4Ps are 1W at 70°C. 450V on 100K is a bit over 2 watts. Too much power and marginal on the voltage (only 10% margin which is reduced in humid or dusty environments). Using two 100K in series would reduce the total power to about 1W total (0.5W each) and each resistor would see 225V which is better margin.
I have used Holco parts many times in tube and solid state applications with no issue. I ususally get them at the Parts Connexion.
Matt
Thanks for the help.
I know not to go over the power rating or right up to it for that matter, which is most likely why people were saying that theirs failed at 100V. Yeah... 100V but at what power?
I just wanted to double check that there weren't reliability issues with these failing well under tolerance.
-Matt
I know not to go over the power rating or right up to it for that matter, which is most likely why people were saying that theirs failed at 100V. Yeah... 100V but at what power?
I just wanted to double check that there weren't reliability issues with these failing well under tolerance.
-Matt
I usually buy these, when 1% tolerance is not needed:
http://www.reichelt.de/Metalloxid-2W-5-/2/index.html?;ACTION=2;LA=2;GROUPID=3082
Otherwise, 1W 1% metal film by Vishay-Dale are my default choice.
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You know it's funny but I tried some Chinese metal film resistors from e bay and they worked great. I'm ashamed.
Maybe we should call an exorcist?
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