Filmosound 18Watt conversion, Help!

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LeifH
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Re: Filmosound 18Watt conversion, Help!

Post by LeifH »

JMPGuitars wrote:
Wed 03/31/21 5:30 pm
LeifH wrote:
Wed 03/31/21 5:08 pm
I got the new tubes from the Tube Store today.
As I'm now a little paranoid about this. I had added screen resistors to my 5E3 when I built it on what seemed like everyone's recommendation as a little protection and to limit blocking distortion.

Is this a good idea on the lite iib? And, what size and wattage are preferred?

Again, thanks.
The lite 2b already has screen resistors. If you're following my docs: files/JMPGuitars_18_Watt_Lite_2b_Schematic.pdf

...then it is sharing a 1K 3W screen resistor. You could use 2 separate 1K 3W resistors instead if you prefer.

The old doc versions had 100Ω screen resistors, but they should really be 1K.

Thanks,
Josh
Thanks Josh, I'm not good at my words today.
Yes, I meant individual, for each tube. And does that provide better protection as well as blocking the isolation?
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Re: Filmosound 18Watt conversion, Help!

Post by JMPGuitars »

LeifH wrote:
Wed 03/31/21 6:06 pm
Thanks Josh, I'm not good at my words today.
Yes, I meant individual, for each tube. And does that provide better protection as well as blocking the isolation?
Words are hard sometimes, I hear ya. ;)

It's maybe better protection. Like if a resistor fails, then only one of the tubes will be directly affected, but I've never actually had that happen. I don't know what you mean by "blocking the isolation." I wouldn't overthink it. Either use two or use one, as long as you use 1K 3W, you're good.

Thanks,
Josh
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Re: Filmosound 18Watt conversion, Help!

Post by LeifH »

Sorry, that time I swear it was my stupidity. Not auto correct.

When I built my 5E3, as I recall, I was advised to put individual resistors on each tube to both prevent blocking distortion and help protect the tubes from each other. What i meant by isolation.

I wasn't sure about just one shared resistor both protecting the screens and helping to prevent blocking distortion.
I thought the blocking distortion was one tube pushing when it was supposed to be pulling or vice versa, ( out of phase) into the other tube via the screens?
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Re: Filmosound 18Watt conversion, Help!

Post by JMPGuitars »

LeifH wrote:
Thu 04/01/21 6:00 pm
Sorry, that time I swear it was my stupidity. Not auto correct.

When I built my 5E3, as I recall, I was advised to put individual resistors on each tube to both prevent blocking distortion and help protect the tubes from each other. What i meant by isolation.

I wasn't sure about just one shared resistor both protecting the screens and helping to prevent blocking distortion.
I thought the blocking distortion was one tube pushing when it was supposed to be pulling or vice versa, ( out of phase) into the other tube via the screens?
Read the maestro: https://www.aikenamps.com/index.php/wha ... distortion
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Re: Filmosound 18Watt conversion, Help!

Post by LeifH »

JMPGuitars wrote:
Thu 04/01/21 6:08 pm
LeifH wrote:
Thu 04/01/21 6:00 pm
Sorry, that time I swear it was my stupidity. Not auto correct.

When I built my 5E3, as I recall, I was advised to put individual resistors on each tube to both prevent blocking distortion and help protect the tubes from each other. What i meant by isolation.

I wasn't sure about just one shared resistor both protecting the screens and helping to prevent blocking distortion.
I thought the blocking distortion was one tube pushing when it was supposed to be pulling or vice versa, ( out of phase) into the other tube via the screens?
Read the maestro: https://www.aikenamps.com/index.php/wha ... distortion
He sure is, that was an explanation and a half. Thanks!
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Re: Filmosound 18Watt conversion, Help!

Post by LeifH »

As an update, i received the NOS 6P14P and installed them. To my ear, and at lower volume it's running well. The 6P14P seem less chimey than the Tung-Sol's.
They sound good, more creamy.
Again, its in an apartment. Sadly, we've been in lockdown for the past month now, so going to the cottage to crank this up, ot getting to a jam hasn't happened.

Thanks to you the community for your help!
I can't wait to get this turned up beyond almost 2!
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Re: Filmosound 18Watt conversion, Help!

Post by Bieworm »

LeifH wrote:
Sun 05/09/21 5:24 pm
As an update, i received the NOS 6P14P and installed them. To my ear, and at lower volume it's running well. The 6P14P seem less chimey than the Tung-Sol's.
They sound good, more creamy.
Again, its in an apartment. Sadly, we've been in lockdown for the past month now, so going to the cottage to crank this up, ot getting to a jam hasn't happened.

Thanks to you the community for your help!
I can't wait to get this turned up beyond almost 2!
Leif... hope you're not expecting Mil Spec from these 6P14P tubes.. I already ahve a pair rattling at higher volume.. even with dampening rings.
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Re: Filmosound 18Watt conversion, Help!

Post by zaphod_phil »

LeifH wrote:
Sat 04/03/21 5:52 pm
JMPGuitars wrote:
Thu 04/01/21 6:08 pm
LeifH wrote:
Thu 04/01/21 6:00 pm
Sorry, that time I swear it was my stupidity. Not auto correct.

When I built my 5E3, as I recall, I was advised to put individual resistors on each tube to both prevent blocking distortion and help protect the tubes from each other. What i meant by isolation.

I wasn't sure about just one shared resistor both protecting the screens and helping to prevent blocking distortion.
I thought the blocking distortion was one tube pushing when it was supposed to be pulling or vice versa, ( out of phase) into the other tube via the screens?
Read the maestro: https://www.aikenamps.com/index.php/wha ... distortion
He sure is, that was an explanation and a half. Thanks!
The screen resistor arrangement is quite irrelevant to blocking distortion. The series resistor on the signal grid (g1) is intended to help with that.

Apart from that, I usually have the screen grids fed by individual 100 ohm resistors fed from a shared 1k resistor.
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