Holco H4P Resistors, Should I use them? - diyAudio
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Old 2nd August 2012, 07:11 PM   #1
mbeards is offline mbeards  United States
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Default Holco H4P Resistors, Should I use them?

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
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Old 2nd August 2012, 08:49 PM   #2
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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
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Old 3rd August 2012, 02:09 AM   #3
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Quote:
Originally Posted by mbeards View Post
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
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...

Last edited by soundguruman; 3rd August 2012 at 02:18 AM.
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Old 3rd August 2012, 09:10 AM   #4
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Quote:
Originally Posted by soundguruman View Post
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...
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
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Old 3rd August 2012, 09:14 AM   #5
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Originally Posted by soundguruman View Post
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.
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
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Old 3rd August 2012, 03:57 PM   #6
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Originally Posted by Rundmaus View Post
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.
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Old 3rd August 2012, 04:23 PM   #7
12E1 is offline 12E1  United Kingdom
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Quote:
Originally Posted by soundguruman View Post
FYI I highly recommend that you use 1 watt for plate and cathode resistors, and 1/2 watt for the signal path...
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.
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Old 3rd August 2012, 04:28 PM   #8
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Originally Posted by 12E1 View Post
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.
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Old 3rd August 2012, 04:49 PM   #9
TheGimp is offline TheGimp  United States
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...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)
What resistor value, under what conditions?

A 1W resistor below 10Kohms with 100V across it will not survive long term. The lower the resistance the faster it will fail, and the greater the probability it will fail in a spectacular manner.
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Old 3rd August 2012, 05:05 PM   #10
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Originally Posted by TheGimp View Post
What resistor value, under what conditions?

A 1W resistor below 10Kohms with 100V across it will not survive long term. The lower the resistance the faster it will fail, and the greater the probability it will fail in a spectacular manner.
Like I said, oversized is better.
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