Split load plate resistor: which goes where?

[nee]

Greetings!

I'm a little confused over the 3rd stage split load plate resistor switch.

I've seen some diagrams drawn with the 82K resistor closest to the plate, and some with the 22K resistor closest to the plate. I understand that there is no "correct" version, and the ears should be the judge, but what is generally accepted as the better choice?

With the 82K resistor closest to the plate then the signal is - I guess - 82/104ths away from normal, which seems a lot.

[paulster]

82K to the plate, 22K to B+

[collinsamps]

Depends on which switching drawing you are viewing. If your plan is to place one before the coupling cap and one after(true split load) then you'll want to use the 22K on the plate as the 82K would nearly kill the entire AC component and you wouldn't be happy.

[nee]

If your plan is to place one before the coupling cap and one after(true split load) then you'll want to use the 22K on the plate as the 82K would nearly kill the entire AC component and you wouldn't be happy.

Well, I'm not sure what you mean by "before" and "after". The diagrams I refer to have the B+ connected to two resistors in series going to the plate, and the coupling cap connected to the junction of the two resistors.

[collinsamps]

If your plan is to place one before the coupling cap and one after(true split load) then you'll want to use the 22K on the plate as the 82K would nearly kill the entire AC component and you wouldn't be happy.

Well, I'm not sure what you mean by "before" and "after". The diagrams I refer to have the B+ connected to two resistors in series going to the plate, and the coupling cap connected to the junction of the two resistors.

Yes, one resistor before the coupling cap and one after, or at the junction of the two resistors. Meaning that the AC signal is going to be attenuated by the resistor you have attached to the plate. The 82k there would knock it down to almost nothing, just as indicated in your first post, so unless that's what you want. Use the 22K on the plate.

[paulster]

Presumably the OP is referring to the Komet Concorde or K60 since he has specified the 82K and 22K values that these use. Both of these use the 82K at the plate side and the 22K at the B+ side.

[collinsamps]

Presumably the OP is referring to the Komet Concorde or K60 since he has specified the 82K and 22K values that these use. Both of these use the 82K at the plate side and the 22K at the B+ side.

Presumably, posting in the tech forum vice wreck forum and not specifying the platform would get you non platform specific reply's that leaned more toward the other 99% of build topologys available.

[paulster]

I wasn't aware that a switched plate split was in common use other than in the Komet amps, and especially with those particular values.

I've got to be honest and say that even if it was common, I couldn't see how the -2dB gain difference that having the 22K on the plate side would be of any tangible benefit in the real world. The -13dB gain difference that having the 82K on the plate side would at least change the character of the amp, which is the idea of the circuit.

[nee]

Thanks for all this info. collinsamps - I hadn't seen that Ahola article. It's true that the only implementation I was aware of was the 82K/22K in the Komet. Diagrams for this have been drawn both with the 82K next to the plate - which I learn is the correct way, thanks Paulster - and with the 22K next to the plate, which I'm sure came about because many people - myself and collinsamps included - thought that 82K would produce way too much signal loss.

[collinsamps]

Common? It's a common mod where I'm from(not sure about your island) and no one mentioned a certain production amp until you did. The man got his answer and even some data to support doing it differently. If you want to get personal with me try using a PM and spare the masses.

[FunkyE9th]

I've got to be honest and say that even if it was common, I couldn't see how the -2dB gain difference that having the 22K on the plate side would be of any tangible benefit in the real world. The -13dB gain difference that having the 82K on the plate side would at least change the character of the amp, which is the idea of the circuit.

An LTP has slight imbalance that you see a lot of amps use an 82k on the inverting triode plate and 100k on the non-inverting triode. Actually, a Fender Blues Deville uses a split load to compensate for the imbalance, 91K and 9.1K. The 9.1K connects to the plate.

[collinsamps]

Thanks for the PM SunnyDaze & yourwelcome. FunkyE9th thanks for another example of what I would consider a normal application of a splitload plate.

[sunnydaze]

Thanks for the PM SunnyDaze & yourwelcome. FunkyE9th thanks for another example of what I would consider a normal application of a splitload plate.

Hey, thanks for posting the article. As I said in the PM, thought it was very interesting, and until I read it and looked at the excellent diagrams, had no idea what anyone was talking about. I've learned a ton on this forum and appreciate when very knowledgeable people such as you take the time to respond to someone’s question.

Thanks
Mike

[markr14850]

One thing to be aware of with this is that the power supply ripple rejection (PSRR) gets worse as you have less resistance between you and the ripple.

If your B+ is really clean, no worries. If not, keep it in mind.

[M Fowler]

I found this circuit when I built my Komet 60 and had no other experience with it before. But I was only rebuilding Fender Bassman, Tremolux and Bandmasters before I joined this Forum.

Both Craig(collinsamps) and Paulster have been very helpful thanks guys and Sunny is right been learning a bunch.

Mark