CF vs MF plate resistors.

[Austin]

I am not talking about just in tube amp, the thread is about the difference, I mention one major difference.

Regarding to tube amp, I question the validity of using CC that cost so much more to get a little bit of volt coef that you can get by playing with the second harmonics using the load line.

In the site where I am buying them, the cc are about the same price as the others. $1.25 per 5 of them for 1/2 watt
CE Distribution LLC

What is it that you do to get more second harmonics? You make the loadline steeper with lower resistance plate load right?

[lowell]

Check out http://www.valvewizard.co.uk/Common_Gain_Stage.pdf

You would want to bias so the plate sits closer to the B+. The grid curves get more bunched up there. It's not solely the value of Ra, but a combo of that and Rk. A smaller Ra gives a steeper load line, and a larger Rk biases more cold and more towards the bunched up end of the grid curves.

[Alan0354]

In the site where I am buying them, the cc are about the same price as the others. $1.25 per 5 of them for 1/2 watt
CE Distribution LLC

What is it that you do to get more second harmonics? You make the loadline steeper with lower resistance plate load right?

It is in chapter 13 of RDH4 page 549 and 550, you change the Load resistance ( of cause adjust the voltage to maximize symmetrical swing) to tilt the load line, use the ruler given to turn it around!!!

[R.G.]

I am not talking about just in tube amp, the thread is about the difference, I mention one major difference.

You are right; there are applications where you do need peak surge ability. I just don't know where you'd need that in a tube amp, and this is, after all, a tube amp forum, so some special attention is justified for that use.

Regarding to tube amp, I question the validity of using CC that cost so much more to get a little bit of volt coef that you can get by playing with the second harmonics using the load line.

Well, there are remarkably few places in a tube amp where the signal is appropriate to setting up the voltage-coefficient distortion thing. Two CCs per amp should do it nicely. And now that CCs are popular in the DIY market, they are much easier to find and cheaper than they were even a few years ago.

[Alan0354]

You are right; there are applications where you do need peak surge ability. I just don't know where you'd need that in a tube amp, and this is, after all, a tube amp forum, so some special attention is justified for that use.


Well, there are remarkably few places in a tube amp where the signal is appropriate to setting up the voltage-coefficient distortion thing. Two CCs per amp should do it nicely. And now that CCs are popular in the DIY market, they are much easier to find and cheaper than they were even a few years ago.

Where can you buy CC cheaper, the surplus store here is like $1 each for the 1W and no 100K. I have nothing against the CC, I am just allergic to the price!!!!

No you never encounter in tube amp, and I doubted you ever even encounter in SS amp. I just talk in general.

Oh another thing, CC is noisy, there is no way out of this one. MF is quieter, there is no 1/f noise which is actually the dominant noise for audio. People should use MF at the front end before the first tube. Then after the first gain stage, everything is easier regarding to noise.....You know, that 68K grid stop or something at the input.

[R.G.]

Where can you buy CC cheaper, the surplus store here is like $1 each for the 1W and no 100K. I have nothing against the CC, I am just allergic to the price!!!!

I said:
they are much easier to find and cheaper than they were even a few years ago.

It was difficult to find them at all perhaps 10 years ago. Now, they are stocked many places. My favorite mail order place, Mouser Electronics has in stock 146 1W values, and 429 1/2W values. The 1W values are pricey, about $2.00 each, but this is hardly a bankruptcy issue, especially since in today's dollars they are likely to be cheaper than they were in the 1960s. The 1/2W stock is about $0.15 each in small quantities, and only about $0.18 in ones.

Mouser Electronics - Electronic Components Distributor

When I first started messing with tube amps in earnest and wrote the Tube Amp FAQ, Mouser stocked ==> zero <== carbon comps.

[Enzo]

Well, you supposed to use resistors that can handle the average power so it does not catch on fire.

Isn't just average power, you also must consider circuit failures. Like a shorted 6L6 that burns up the screen resistor.

[Alan0354]

I said:
they are much easier to find and cheaper than they were even a few years ago.

It was difficult to find them at all perhaps 10 years ago. Now, they are stocked many places. My favorite mail order place, Mouser Electronics has in stock 146 1W values, and 429 1/2W values. The 1W values are pricey, about $2.00 each, but this is hardly a bankruptcy issue, especially since in today's dollars they are likely to be cheaper than they were in the 1960s. The 1/2W stock is about $0.15 each in small quantities, and only about $0.18 in ones.

Mouser Electronics - Electronic Components Distributor

When I first started messing with tube amps in earnest and wrote the Tube Amp FAQ, Mouser stocked ==> zero <== carbon comps.

Then, I am definitely allergic to CC. I am going to replace all the CC with wire wound and/or metal film sooner or later. I bet it is not going to make a dent of a difference. Inductance from the wire wound is not going to make a dent of a difference for tube amp. With the high impedance circuit, it is hard to even design using an inductor as the value of the inductance has to be very high to be in the ball part of the high impedance value.eg. You want to get a reactance of 10K at 10KHz,

XL=2\pi fL => L=0.159 Henry!!! That is an awfully big inductor even with high u core.

I don't think the inter winding capacitance make a dent of a difference either. I experimented putting a 270pF cap to ground from the plate with 68K plate resistor, it did not make any difference in the sound. An extra 10pF due to the winding is not going to matter.

[Austin]

Then, I am definitely allergic to CC. I am going to replace all the CC with wire wound and/or metal film sooner or later. I bet it is not going to make a dent of a difference. Inductance from the wire wound is not going to make a dent of a difference for tube amp. With the high impedance circuit, it is hard to even design using an inductor as the value of the inductance has to be very high to be in the ball part of the high impedance value.eg. You want to get a reactance of 10K at 10KHz,

XL=2\pi fL => L=0.159 Henry!!! That is an awfully big inductor even with high u core.

I don't think the inter winding capacitance make a dent of a difference either. I experimented putting a 270pF cap to ground from the plate with 68K plate resistor, it did not make any difference in the sound. An extra 10pF due to the winding is not going to matter.

The cc look nice imo even if they dont sound any different...

Do you guys think it is 3w in the left in this pic?

I wonder where we can buy those?

[Alan0354]

The cc look nice imo even if they dont sound any different...

Do you guys think it is 3w in the left in this pic? [ATTACH=CONFIG]20125[/ATTACH]

I wonder where we can buy those?

The only think I worry about looking nice is my pocket!!!

I never seen a CC bigger than 2W yet.

[Chuck H]

There use to be a 5W CC in the standard type pictured. I've seen them in a couple of old single ended amps as power tube cathode resistors. They were bigger than the biggest one pictured though. About the size of a new pencil eraser.

[Austin]

There use to be a 5W CC in the standard type pictured. I've seen them in a couple of old single ended amps as power tube cathode resistors. They were bigger than the biggest one pictured though. About the size of a new pencil eraser.

I just realized your profile pic is a dogs butt.. I thought it was some kind of babboon or something all this time.... Too funny!

[Alan0354]

I don't see the dog butt!!! I see a hot dog on top of the dog's nose!!!

[Chuck H]

It's a dog butt all right. Funny at the time, but no staying power. Changing it soon.