Metropoulos Forum

Hi guys. What is the lowest possible wattage 1k resistors to use for the grid protection? ......I have 5 watt ones on the way but for temporarily what wattage can I get away with using?

I have seen some older amps that used resistors as low as 1-2 watts on the screens. These almost act like a fuse in the event that a tube goes bad the resistor will open and protect the amp. Some folks will go the other way up to say a 7 watt for reliability. If a tube blows, the resistor should hold if you shut the amp down quickly and then you can change the tube and keep playing. If you just want to test the amp and don't plan on pushing it to hard the lower rating resistor should be okay.

Thanks danman.

It also depends on the resistance and the tube type. EL34 screens draw considerably more than other types so 1K at 5W is a sensible area to be in.

What about values.....can I use 2.4k? .....I have 5watt wirewound ones and waiting for my 1k's. ......if I use 2.4k will 6v6s work?

2.4k?? no please.

from 470ohm to 1k5 sounds good (different tones, but good).

2k4... I don't like it, and remember, the more the resistance is, more wattage is needed.

Carbia wrote:2.4k?? no please.

from 470ohm to 1k5 sounds good (different tones, but good).

2k4... I don't like it, and remember, the more the resistance is, more wattage is needed.

Okay thanks man

I just ran 6 1/2 watt resistors in parallel twice with the same values and I get 1.32k 3w. Do you guys think that'll be okay for temporarily until my 1k 5 watt get here next month?

Like Carbia said, going up to 2.4k will change the sound slightly. The amp will likely sound more compressed from what I have heard but that will not damage anything. I think I would choose those over the 6 1/2 watters for a temporary solution. I don't believe that you ever mention what type of tubes you were using though. 1k is standard for EL34's and 470ohm will be ok for KT66's. Back in the 60's the amps were not fitted with screen resistors because the quality of the tubes were much better. If you will be using current production tubes then it is necessary to use them to protect the screen grid from meltdown. If you have to use a very low wattage resistor the worst thing that would happen is that the resistor would go open if you push the amp too hard or a power tube blows. If you are only testing the amp and/or playing at low volumes then you should be fine.

Sorry, I just reread your post and saw that you mentioned 6v6 tubes. I have heard folks go as high as 10k on 6v6 screens. They did mention that the amp became much darker and tighter with the higher values though.

about 6v6... check plate voltage first.

6v6 can run at 400v, and some, like JJ, handles around 450v without issues, but if you put a 6v6 at 490v...

danman wrote:Like Carbia said, going up to 2.4k will change the sound slightly. The amp will likely sound more compressed from what I have heard but that will not damage anything. I think I would choose those over the 6 1/2 watters for a temporary solution. I don't believe that you ever mention what type of tubes you were using though. 1k is standard for EL34's and 470ohm will be ok for KT66's. Back in the 60's the amps were not fitted with screen resistors because the quality of the tubes were much better. If you will be using current production tubes then it is necessary to use them to protect the screen grid from meltdown. If you have to use a very low wattage resistor the worst thing that would happen is that the resistor would go open if you push the amp too hard or a power tube blows. If you are only testing the amp and/or playing at low volumes then you should be fine.

Actually I'm using el34s. ....I'll use the 2.4k 5watt ones.....it'll be just temporary anyways until the others come in the mail.

danwelsh wrote:

danman wrote:Like Carbia said, going up to 2.4k will change the sound slightly. The amp will likely sound more compressed from what I have heard but that will not damage anything. I think I would choose those over the 6 1/2 watters for a temporary solution. I don't believe that you ever mention what type of tubes you were using though. 1k is standard for EL34's and 470ohm will be ok for KT66's. Back in the 60's the amps were not fitted with screen resistors because the quality of the tubes were much better. If you will be using current production tubes then it is necessary to use them to protect the screen grid from meltdown. If you have to use a very low wattage resistor the worst thing that would happen is that the resistor would go open if you push the amp too hard or a power tube blows. If you are only testing the amp and/or playing at low volumes then you should be fine.

Actually I'm using el34s. ....I'll use the 2.4k 5watt ones.....it'll be just temporary anyways until the others come in the mail.

Hold off, have patience and wait till you get the proper ones. A couple days is insignificant.

OnTheFritz wrote:

danwelsh wrote:

danman wrote:Like Carbia said, going up to 2.4k will change the sound slightly. The amp will likely sound more compressed from what I have heard but that will not damage anything. I think I would choose those over the 6 1/2 watters for a temporary solution. I don't believe that you ever mention what type of tubes you were using though. 1k is standard for EL34's and 470ohm will be ok for KT66's. Back in the 60's the amps were not fitted with screen resistors because the quality of the tubes were much better. If you will be using current production tubes then it is necessary to use them to protect the screen grid from meltdown. If you have to use a very low wattage resistor the worst thing that would happen is that the resistor would go open if you push the amp too hard or a power tube blows. If you are only testing the amp and/or playing at low volumes then you should be fine.

Actually I'm using el34s. ....I'll use the 2.4k 5watt ones.....it'll be just temporary anyways until the others come in the mail.

Hold off, have patience and wait till you get the proper ones. A couple days is insignificant.

I know I should wait.......but I don't want to especially for just 2 darn resistors. I've been building this for 3 months now and it's just so frustrating waiting for things to come as I sourced alot of stuff separately and I'm in canada so alot of it got held up at customs for weeks at a time......having vented this I most likely will wait.

danwelsh wrote:

OnTheFritz wrote:

danwelsh wrote:
Actually I'm using el34s. ....I'll use the 2.4k 5watt ones.....it'll be just temporary anyways until the others come in the mail.

Hold off, have patience and wait till you get the proper ones. A couple days is insignificant.

I know I should wait.......but I don't want to especially for just 2 darn resistors. I've been building this for 3 months now and it's just so frustrating waiting for things to come as I sourced alot of stuff separately and I'm in canada so alot of it got held up at customs for weeks at a time......having vented this I most likely will wait.