5V4 instead of 5Y3 ?

[slidincharlie (Carlo P)]

Hi everybody.
I've just bought a Valvetrain 205, a 5W amp based on the Fender 5F2A circuit (narrow panel tweed Princeton).
12AX7, 6V6, 5Y3.
I didn't expect much headroom from this amp of course, but to be honest I'd like to have a 'little' more clean headroom
I've read that a 5V4 rectifier would help.
What should I expect from a 5V4 instead of a 5Y3 in this type of circuit, electrically speaking? Is it a safe substitution? Any advice? Or is it just a waste of time?
TIA,
Carlo

[Chuck H]

If the amp has similar voltages to a 5f2a then it should be fine. The 5v4 will increase voltage on the tubes. Quite a bit. Still not silly high like Vibro Champ. This should increase headroom a little. I don't know what speaker that amp uses but in my world louder is as good as more headroom if the goal is a cleaner tone at a given volume. You could try plugging the amp into an efficient 4 ohm cabinet for an increase in fidelity and volume.

[slidincharlie (Carlo P)]

Sorry for the missing info on voltages.
This amp reads 370 Vdc from the rectifier (5Y3) and 353 Vdc at the 6V6 plate (currently an Electro-Harmonix. I have a few NOS Marconi big-bottle 6V6's at home).
If I read the RCA Manual correctly, 350V is about the maximum plate voltage allowed, right?
The 5F2A schematics available on the web do not show voltages, but those for the 5F2 say 320 V and 305 V from the 5Y3 and on the 6V6 plate, respectively.
So what can I expect from a 5V4?
I can evaluate other options of course (e.g., a different cone), but changing tubes would be my first step if voltages stay at a safe level.

[Chuck H]

You can probably expect about 375Vp with the 5V4. Modern 6V6's tent to be more tolerant of high voltages. And even "back in the day" Fender was running (now vintage) 6V6's way over spec for the BF and SF Champs. It may help to consider that the working voltage of the tube is measured from the cathode to the plate. So for a cathode biased 6V6 with, say, 22V on the cathode, that 375Vp is actually 353 working volts across the tube. Besides, there are many vintage and cloned champs out there with 400+Vp that are working just fine. You also have the account of other Valvetrain 205 users that don't seem to be having any trouble with a 5V4 rectifier. Just plug it in and see what you think of the tone. I don't think you need to worry about the operating parameters.

[Justin Thomas]

JJs are spec'd @ 500V, and hundreds of bazillions of NOS & UOS 6V6s get run at 400+V every day. I will add that the ONLY (and last!) 6V6 my 79 Champ ever torched was an EH...

This one time, at Stupid Camp, I put a GZ34 in my Champ. The fuse blew.

Justin

[slidincharlie (Carlo P)]

Thank you guys.
I will try a 5V4 as soon as I buy one.

[Jammin'John]

Speaker

A speaker swap would do a lot more good than hitting the tubes with more voltage.
6v6's sound sweeter & compress better at lower voltages.

JJ

[slidincharlie (Carlo P)]

A speaker swap would do a lot more good than hitting the tubes with more voltage.
6v6's sound sweeter & compress better at lower voltages.
JJ

Thank you JJ. A speaker swap is indeed a potential option, but I don't have an 8" speaker available. In the meantime I could try a 10" CTS alnico speaker that I have.

[Jammin'John]

Ceramics are louder & tighter & cheaper than alnico.
If a 10" can fit in your amp it would be nice.

JJ

[Chuck H]

Ceramics are louder & tighter & cheaper than alnico.

Different tubes, plate voltages, speakers (ceramic vs. alnico too), cap values, guitar pickups, pick thickness, states of mind, etc., etc., etc... It all makes a difference. Why should a different speaker be a better ideal than higher plate voltages. Because 6V6 sound "sweeter" at lower voltages? Well alnico sounds "sweeter" than ceramic!?! Maintaining both of these positions is at least a little contradictory.?. It's natural to want to impress a personally successful formula on a situation where it could apply. If lower voltage 6V6's and a ceramic magnet speaker in a Champ works for you that's great. Maybe Carlo would be happier with a little more voltage and an alnico speaker! Maybe for some the best would be lower voltage AND the alnico speaker and for others it would be the higher voltage AND the ceramic speaker.?. Not arguing. Just sayin'. Carlo asked about higher voltage and the possibility of using a 5V4 rectifier. He can always plug the 5Y3 back in if he doesn't like it.

I don't know the specifics of all the Champ models, but I do know that you can fit a 10" speaker into a Vibro Champ. Since most 10" guitar speakers are 8 ohms, selection may be limited for 4 ohm options. 8" guitar speakers at 4ohms are available because people need speakers for their Champs. Running the amp with the correct load should be important if a louder clean tone is a criteria. Just things to consider on the subject.

[Jammin'John]

Alnico does sound nice but a champ has NO balls & a good ceramic is helpful in that regard.
6v6's DO sound better at lower voltages and with a more efficient speaker you get a more useful amp.
That said,I prefer 2 x 6v6's or 4 x 6v6's & I like to use an alnico with a ceramic.

JJ

[Chuck H]

Alnico does sound nice but a champ has NO balls & a good ceramic is helpful in that regard.
6v6's DO sound better at lower voltages and with a more efficient speaker you get a more useful amp.
That said,I prefer 2 x 6v6's or 4 x 6v6's & I like to use an alnico with a ceramic.

JJ

I'm down with that. I bet it sounds great! And I impress my own experience and successful gear and circuit formulas in my responses. I was just noting that there's nothing wrong with the path that Carlo is exploring. Even if it's wrong for you personally.

EDIT: FWIW I have a little amp built from the guts of an old VOM phonograph. A pair of 6V6's at 305Vp. The amp is a very basic build with a single channel BFish preamp and LTP inverter. It's in a combo cabinet with a 10" ceramic speaker. I don't play through it often, but I'm always impressed by how good it sounds. I've been thinking of reverse engineering the transformer so I can build a 4x6v6/2x10" version So I'm definitely down with your formula. I just don't think it necessarily applies to a single ended 6V6 amp, or Carlo's personal preferences. And there are certainly a lot of BF and Vibro Champ users out there that are very happy with their amps that don't follow your suggested formula. I never said you were wrong. Your post is worded such that you think anything other than your way is wrong. And that's not correct.

[Jammin'John]

He was asking for more headroom.
I offered him more headroom without makin' the amp harsh and loosing the mojo. That's all.
No harm,no foul.

JJ

[slidincharlie (Carlo P)]

I always appreciate all the advice I can get here - I elaborate and then try what I can with my capabilities and my budget

Just to be more precise, this amp is based on a narrow panel Princeton, not a Champ (5F2A vs. 5F1). I haven't studied the two schematics but both models share the same tube complement.

Said that, I was looking for some more clean headroom. I've read on another forum that a 5V4 (possibly coupled with a 12AY7, even though this would tame the gain quite a bit and reduce the output level - correct me if I'm wrong) might be the way. That's why I opened this thread here. I'm after a few 5V4's on ebay right now, I will buy one soon.

I have checked and this amp cannot accommodate a 10" speaker. So I have connected it to two different cabs: a Deluxe reverb (1x12" ceramic) and a Vibrolux reverb (2x10" ceramic). Believe it or not, there is not a HUGE difference between the three speaker combinations. There is some, but not that great, 2x10" being a little louder and cleaner than the others. I remember my silverface Vibro Champ (that I stupidly sold) plugged into the Vibrolux cabinet: THAT was different! Beautifully bolder and cleaner. I wonder why I didn't have the same big difference with this new little amp...

Anyway this amp sounds really nice and sweet with a warm, creamy distortion. I will try the tube(s) swap but am not sure that I won't be going back to its original setup!

[Chuck H]

IMHE (and many may argue for their own reasons) a 12ay7 plugged into the V1 position on many amps I've tried it on sounds wonderfully throaty and punchy. This experience applies to a few different amps too. It's a sort of punctuation of certain frequencies that sounds like a low mid bump with a notch just above that and then a low treble bump with no harsh top end. I realize this sounds like mojo speak, it's just my totally biased perception. It's always worth trying a 12ay7 in V1 for anything but a hard rock/metal amp. Good sounding tubes for guitar.