i love my new 5f2-a, but i wonder

[pietro_moog]

hi guys.
i built my amp and i love it.
it works great, it sounds better after a few days..

i have a few questions:

-) the amp doesn't seem to break. it breaks around 8, slightly, and there an
overdrive at 12. i was expecting hell at 12.
maybe it's me, i was used to hi gain amps..

-) the input with the 1M resistor on it produces a very low output volume.
with the gain all the way up i can barely hear anything.
if i put a tubescreamer in the chain, there's a sound. very low.
the other input works fine.
does it have to work this way?

[loudthud]

Something could be wired incorrectly at the input jacks. Unplug the guitar cable at the guitar and measure the resistance from tip to sleeve. Now move the cable to the other input and measure again. The amp should be off for this test.

[pietro_moog]

thanks
yeah, i did. i found 134k on one input and 1,06M on the other.
are those correct values?

[MWJB]

Yes, close enough. Something farther down the chain must be wired wrong. Anypics of the circuit?

Tube screamers were invented much later than 5F2A's, so no, they don't require a tube screamer to work properly.

Attach your AC voltmeter accross the speaker terminals and play, the reading will fluctuate but try and determine an average, square this voltage, then divide by speaker load in ohms, you should get around 6W?

[pietro_moog]

thanks guys.
i checked some resistance values and i found out the wiring on the low gain input was inverted.
now everything is working and the amp seems dirtier to me, bur maybe it's a placebo.

now i just need a good diy tremolo pedal

[pietro_moog]

WTF!
there's something that's ringing!
i don't know.. every screw has nail varnish on,so they can't ring.
can the 5y3gt tube rings? something ringing inside?

[MWJB]

Possibly, sub out tubes for known good ones to eliminate them from your enquiries.

Could be grounding/layout issue...do you have any pics of the amp? Describe your grounding scheme.

[pietro_moog]

unfortunately i don't have a camera..

it's not a ringing in the sound, it is actually a physical ringing..
my rectifier tube is a sovtek. is it a low quality tube? ( i don't have much experience with tubes..)

if i shake it,it rings. that's why i thought it..

thanks

[MWJB]

Sovtek "5Y3" provide more voltage than a real 5Y3 so I'd be looking to pick up a NOS version anyway. As long as your plate voltage isn't too far over 400vdc to ground, the voltage itself is not a problem.

Ringing in the tube may be related...maybe not (it's probably not a good sign either way). Try a SS or GZ34 BRIEFLY, if you have them to hand.

If it's not a ringing sound...how can you hear it? If it is physically ringing and you can hear that, then surely you have a ringing sound?

[pietro_moog]

do you think that the 5y3 sovtek could damage the amp?
i'm a little afraid of measuring voltages on tubes, so i'd prefer not to do it..

about the ringing:
i'm sorry. i'm italian, english is not my mother language.
so there might be a little communicational problem here.
ringing maybe is not the right word, i hear a mechanical vibration.
not coming from the speaker.
since there's not a screw free to let the bolt go (nail varnish), i thought
there might have been a filament or something vibrating in the tube..
the tube is working.
is this possible?

[MWJB]

"do you think that the 5y3 sovtek could damage the amp?" Not likely.

It's possible that there is mechanical vibration in a tube...you are absolutely sure that it is not coming out of the speaker? Do you have a speaker cab that you can attach with a longer cable to satisfactorily prove that? Be aware that there are conditions related to layout wiring that can sound like mechanical rattle.

If it is a tube, replacing that tube with one that does not ring is the only cure.

[pietro_moog]

thanks.
i' m reading a bit of the tubes sub-forum.
i'm gonna change tubes

i'm not a meat-head! i recognize the difference between something from the speaker and something physical!

[MWJB]

I'm not suggesting you are a meat-head, but your posts suggest limited experience in troubleshooting...a lot of other guys, who aren't meat-heads either, have wasted days/weeks/$ chasing down "mechanical rattles" only to discover that they are electronically generated oscillations caused by poor layout. If you are sure that the rattle/ringing is mechanical, then great, but be sure that you are sure, before going off on a wild goose chase.

Isolating the chassis from the cab (with a longer speaker lead) can also reduce mechanical vibration from the speaker, which may exacerbate mechanical rattles in the chassis.

[pietro_moog]

easy pal, that was a joke.
i have no experience with tubes, but i built a lot of 1176 and 1073.
now i strongly believe there something vibrating in my tubes (6v6 or 5y3)
i'm gonna change tubes in the next few weeks, i'l report.

thanks for your inputs

don't wanna bother you but, do you know about life expectancy of a 5y3 NOS tube?

[MWJB]

"don't wanna bother you but, do you know about life expectancy of a 5y3 NOS tube?" Some last longer than their owners...many are still fine after 50+yrs.