Help, my newly build amp sems far to quiet??

[ajs]

Hey, i just finished my mission amps kit- a 5e3 circuit, with a celestion g12h 30, in a home made pine cabinet... Im a bit confused tho- i finished all the soldering, got everything else done, and switched it on... All ok so far... Then i started playing gently to warm up the speaker, all still ok... After about 20 mins i decided to crank it and hear that awsome tone everyone talks about... It sounds good, great in fact, but its alot quiter than i expected...

This might sound daft- i wasnt expecting it to be really loud, but i cant help thinking- is there something i could have done wrong- maybe sent something to grond be accident somewhere, that would make the amp work, yet not give out full power? I compaired it to an epiphone valve junior through the same speaker, and the valvejuniour was noticably louder- its only got one power amp valve, and its rated at 5 watts- the 5e3 has two, and should be about 18 watts... What have i done wrong? Could there be a valve problem?

Sorry for the long post, but im just left a bit confused and a bit gutted- i wanted to gig with this (my orange ad30r is too loud, and the epiphone valve junior to quiet, i thought this would be perfect)...surely it should be louder when fully crancked, i am able to have a conversation (normal talking- no shouting required)while playing?

Im looking over the diagrams that came with it again, cant see anything wrong- any suggestions would be much apreciated, or even a way to mesure what power im producing- i have a voltmeter handy...

Thanks for the time to read this, and replys will be greatly apreciated...

Adam...

[hasserl]

The difference in volume between 5 and 12 is not a lot. The Epiphone can be quite loud thru an efficient 12" speaker. A lot of this has to do with the frequencies being amplified and perception. The 5E3 tends to be a dark amp, the Epiphone may be a bit brighter, giving the impression that it's louder as the high's cut thru. I know I have a single 6V6 amp with a JEnsen C15N speaker that is really quite loud. The little sucker really screams.

Still, your description of your 5E3 doesn't sound right, a good 5E3 should make you ears ring if you crank it up. You say it's a Mission Amps kit, if Bruce doesn't address your question here (he does check in here a lot and answers a lot so posts) I would contact him for advice. But, in the meantime you should make a full record of voltages thru the amp, as a good starting point.

[MWJB]

Put your voltmeter accross the speaker terminals, set to AC.

Turn your volumes up, Mic all the way up, Instrument halfway, plug in to mic and let rip (or the other way round - inst full up, mic halfway). The reading on the voltmeter will jump about, try to establish an average and report back.

[ajs]

Ok, thanks guys... Just tried taking an ac voltage reading off the speaker... I think im getting alot less power than i should- played different things- first middle c, which i thought would be a good starting point, for whitch i go a reading of about 0.8 volts... then tried strumming an open a chord hard and repeatedly, which gave readings of about 0.8 to 1.1 volts... Thats deffinetly correct, i was sceptical, so i tried two different meters- a new digital one, and an older analoge one- both gave the same readings... That seems very low...

Im running the amp in britain, so i had to use the mojo 761ex power transformer that bruce sent me... Could this be something to do with it? I checked and rechecked the wiring as well all seems ok- im stuck- especially because it is producig sound...

I can take readings form inside the amp as well- which caps should i mesure to give you guys an idea?

Cheers...

Adam...

[ajs]

Also- im just off to band practice, but ill be back in a couple of hours, and ill mesure the voltages then... Does someone have a list of what i should expect, or can someone point me in the direction of a web page with a list of the values?

Thanks again...

Adam...

[Bruce / Mission Amps]

Your MA Tweedy Deluxe schematic has + - voltages written all over it... also, it has the AC voltage output across an 8 ohm load/speaker so you can compare what it will do.
If your's doesn't, email me for the values.
You should be able to measure something like 10vqc-12vac across your speaker load ... if you have the speaker and OT wired right.
761EX PT
If you have it wired correctly, the PT you have is not the problem.
Your amp will actually make a tiny bit more power then the same amp using the 122vac power transformer for my USA and Canadian customers.
So, off the top of my head I'd say you have just mis-wired something as you certainly CAN NOT talk over any 5E3 with either volume pot dimed and the tone set to around 7-8!!

Bruce

[ajs]

Cheers for the help guys... While checking out all the proper voltages i realised my mistake- i had wired pin 6 and pin 8 on the 2nd valve the wrong way around! As soon as i swithced them back to the correct way, the amp got alot louder...

I love this amp now, and i got it fixed just in time- my band are in the studio tonight... Thanks again... And it sounds awsome! I actually cant write in words how pleased i am with it!

Oh, and just out of interest- mixing up the annode and the cathode (is that what i did?) why did it work, but just quiter- is this bad for the amps, and could i make some sort of switch to allow me to have full loud power, or quiet house volumes? Or is this damaging the amp?

Cheers...

Adam...

[dbtk44]

When you say "Valve #2" do you mean one of the 6V6 tubes?

I'd be curious about this too. I think you can take a signal from the cathode, power or pre tubes, and it will be lower voltage but higher current...cathode followers are of that principle I'm pretty sure.
( I wonder if it would mess with the impedence the output transformer would see though).

I gotta crack open a book to confirm the cathode thing, so please don't take this as an "expert opinion" or anything like that...I'm just a tube noob.

Was the sound before you discovered the wiring error anywhere near as good as the sound is now, aside from the volume difference?

Hopefully someone more knowledgeable than I will chime in, because this actually sounds like a pretty neat idea if it's non-destructive.

[stokes]

You only had half your PI tube working properly,so you only had one of the power tubes getting the full signal.

[Bruce / Mission Amps]

You only had half your PI tube working properly,so you only had one of the power tubes getting the full signal.

No, it was a 5E3, which uses one triode as a PI with no gain.

[dbtk44]

Ok let's assume he had 6 and 8 switched on the pre half of the 12ax7...not the splitter half. Sounds like it would simply be a voltage loss, but where would the current be? It would be like a cathode follower...but still that would explain a serious drop in volume I think.

Or let's assume he wired the phase inverter half of the bottle wrong...he would be taking the signal from the cathode and plate still, just swapped around, and they would be inverted from eachother. Wouldn't it still even out though? One's going into one 6V6, and another is going into the other 6V6, just out of phase with eachother...