5F11 current question

[d95err]

I second The Dude's suggestion of a less efficient speaker. Your user will get less volume and earlier apparent breakup. He doesn't know it but he wants a new speaker.

To be significant, the difference in efficiency should probably be at least 3dB. Unless the player is currently using a very efficient speaker, it may be difficult to find a speaker with similar tone but significantly less efficiency.

An attenuator would probably cause less change to the tone, if it's a question of only a small reduction of output.

[robrob]

To be significant, the difference in efficiency should probably be at least 3dB. Unless the player is currently using a very efficient speaker, it may be difficult to find a speaker with similar tone but significantly less efficiency.

I'd suggest a Weber Alnico with a smooth cone and light dope which comes in around 95dB with earlier speaker breakup.

[Chuck H]

FWIW you may want to find out what brand of 5y3 is in the amp now. I know that for some time Sovtek was selling 5y3's that didn't exhibit the usual voltage drop. Like A LOT less. It was a real problem in amps like the SF Champs that already had 410Vp on a 6v6 in class A.

[jimboyogi]

Bias wiggle can work well with cathode bias. If you grounded the bias side of the "depth" pot (disconnect the bias supply though, do not ground that), then inserted cathode resistor/cap on the 6V6 cathodes, it should work.
The only caveat is that the trem depth may not be large enough, as the "depth" pot and the 220K grid leaks form a voltage divider for the trem signal, and give only ~1/2 of the maximum depth. It may still be enough depth.

[Enzo]

FWIW you may want to find out what brand of 5y3 is in the amp now. I know that for some time Sovtek was selling 5y3's that didn't exhibit the usual voltage drop.

That is sure true. In fact you may find two different 5Y3 tubes that have a greater difference between them than a 5W4 and a 5Y3 you happen to have.

[SoulFetish]

I agree that a speaker change probably offers a bigger change in response than switching the rectifier. However, a cheap option you may want to experiment with, is the current limiting plate resistors which SHOULD be in series with the plates of the rectifier tube. Fender didn't incorporate them in earlier amps (they may or may not be there in newer amps. Not sure), but the datasheets indicate minimum values depending on the operating conditions. You could increase these resistor values within reason (and power ratings accordingly) to exagerate the effects of the rectifier tubes under full drive.

[nickb]

Bias wiggle can work well with cathode bias. If you grounded the bias side of the "depth" pot (disconnect the bias supply though, do not ground that), then inserted cathode resistor/cap on the 6V6 cathodes, it should work.
The only caveat is that the trem depth may not be large enough, as the "depth" pot and the 220K grid leaks form a voltage divider for the trem signal, and give only ~1/2 of the maximum depth. It may still be enough depth.

To make it work you need to have a very low frequency -3dB point for the cathode bias RC network. Practically this means at least 1000uF in parallel with a cathode bias resistor of 390 ohms.

A easier option is to lower the screen voltage or have a pentode/triode switch.

[SoulFetish]

What's the primary impedance on the OT? The reason I ask is, we can find out what the max current draw for the amp (roughly) with some load lines for the 6V6. The 12AX7s are operating in class A so those are easy enough to figure, we have the B+ and cathode resistor values. This dude may have it in his head that a 5Y3 is what he's looking for, so long as it isn't stressing the rectifier, swap it out and see what he thinks. I've had people come in looking for a 100uF/16V cap and I can try and convince them that a 100uF/25V the same size will be just FINE-- that they could use a 100uF/1000V cap if they chose to (all other things being equal). Size and cost are the limiting factors. But they want to stick to the exact specs.
At least then he'll know it was or wasn't what he was looking for.

[Tom Phillips]

A customer who is a tone chaser and quite knowledgeable wants to try a 5W4 rectifier in his 5F11 Vibrolux. This an excerpt from an email I received
"Also, is there a way to monitor an amps' total tube-current draw while in operation? I'm still chasing this "tone Quest" involving that tweed 5F11 Vibrolux, thinking of trying a 5W4GT in place of the 5Y3GT rectifier. I've been told that would work but only if the Total tubes' current draw ( 5-volt rectifier, 2-6V6GTs & 2-12AX7s) is under 100ma for all. If there's a considerable risk of frying the power transX &/or output trannie I won't risk it"...

Randall,
There have been a lot of valid ideas offered in this thread that will alter the tone and feel of a 5F11. However, it seems to me that the customer never clearly stated what his "tone quest" goal is. That is, specifically what characteristic of the existing amp does he wish to alter and by how much etc? Many tone questers are never satisfied but they like to keep trying things sometimes going in circles. They won't give up on an idea that they read about on the web until they actually try it. You could consider just telling him that the amp won't be damaged by the 5W4GT substitution and letting him try it and decide for himself. Keep in mind that a single substitution is not necessarily a valid test. One would need to try several tubes and they would need to be pre-tested and graded to verify that there were no issues with the old or the new tube. Of course you need to monitor and adjust the line voltage during the testing and yada yada yada. But...if the tube is changed AND the customer thinks that the change makes the amp more to his liking then all is good. Doesn't mean that it will work for others though. That's the way it works in the guitar amp world.
My 2¢,
Tom

[SoulFetish]

Randall,
There have been a lot of valid ideas offered in this thread that will alter the tone and feel of a 5F11. However, it seems to me that the customer never clearly stated what his "tone quest" goal is. That is, specifically what characteristic of the existing amp does he wish to alter and by how much etc? Many tone questers are never satisfied but they like to keep trying things sometimes going in circles. They won't give up on an idea that they read about on the web until they actually try it. You could consider just telling him that the amp won't be damaged by the 5W4GT substitution and letting him try it and decide for himself. Keep in mind that a single substitution is not necessarily a valid test. One would need to try several tubes and they would need to be pre-tested and graded to verify that there were no issues with the old or the new tube. Of course you need to monitor and adjust the line voltage during the testing and yada yada yada. But...if the tube is changed AND the customer thinks that the change likes the effect then all is good. Doesn't mean that it will work for others though. That's the way it works in the guitar amp world.
My 2¢,
Tom

Good thinking! I couldn't have said it better myself