60's ampeg jet 12 too quiet?

[tonewave]

I have a vintage ampeg j12, sounds great and all
however my fender vibro champ is much louder, by about 40%
is that right?
shouldn't the ampeg 12 watts be louder than the champs 5 watts?

[slider313]

Check all you resistors. I had a friend bring me a Jet J-12-D with no output at all. The speaker was good as were the voltages in the power supply. The 470K resistor in the phase inverter drifted up to 1.95 meg. Changed it to a 470K and there it was.

[wingwalker]

I assume you are talking about a 6V6 version, pre 1964.

I have one and while they are not very loud amps it shoudl be louder than a Champ for sure.

[tonewave]

Thanks for the replies
Resistors, I hope it is just that.
I think mine is from 66, which has the weird little 3 way tubes in them plus some other esoteric output tubes

[GAT]

Mine's pretty loud, more than a Champ.

Hogy, from Komet Amps, really serviced mine to peak performance!

[slider313]

Thanks for the replies
Resistors, I hope it is just that.
I think mine is from 66, which has the weird little 3 way tubes in them plus some other esoteric output tubes

If it's a J-12-D then it has either 7868 or 7591 power tubes and a pair of 6BK11 compactron tubes. Should be as loud as a Princeton Reverb.

[tonewave]

yeah I think those are the tubes
its the one with the trem
the faceplate just has J-12 on it

the trem has this really annoying buzz in it, that gets louder when you turn on the trem, and somehow a tremolo-ing buzz is more annoying than a constant one.
take out the first 6bk11 and all the buzz goes away, and so does the trem,
apparently the whole trem circuit is in that first tube,
anyway thats what one amp tech told me

good to hear it should at least match a Princeton
its off to the tech we go...

[FFTT]

If you still have the original Ampeg label 15watt CTS speaker,
those are very inefficient speakers and you can increase your volume
considerably just going to a more efficient speaker.

[tonewave]

If you still have the original Ampeg label 15watt CTS speaker,
those are very inefficient speakers and you can increase your volume
considerably just going to a more efficient speaker.


d'oh! I just got the original speaker reconed

what replacement speaker would match well with the ampeg?

[smolder]

If it's a J-12-D then it has either 7868 or 7591 power tubes and a pair of 6BK11 compactron tubes. Should be as loud as a Princeton Reverb.

The 'D' will only have four tubes (solid state rectifier).

Based upon a recommendation here I went with a slightly brighter weber. A 12F125 I believe.

[FFTT]

d'oh! I just got the original speaker reconed

what replacement speaker would match well with the ampeg?

I blew mine and had to have it re-coned too, but not to worry, it's still
a great low volume recording speaker.

These amps run naturally a bit dark, so it's good to team the amp up
with something tight and bright.

So far the Fane Ceramic Axiom 12 75 in my R12R has been great.

If I had the funds, I'd go to a Fane AXA12, Celestion Gold, Scumback M75

[tonewave]

good speaker ideas thanks
took amp to amp tech, he couldn't find anything astray
apparently he checked over everything in the circuit, esp at the usual prob spots
hmmm.....
so its getting a bit curly for me.
I feel that maybe I should check the resistors myself, just to be %100 sure
to check them properly do you have to take them completely out of the circuit?

[eyeofsetSG]

I am in the process of getting a 1960s Ampeg J12 T with Tremolo and I am trying to find out what kind of tubes it uses. Anyone have any info?

[pelkie123]

The "T" is

68K11 68K11 7591 7591 5Y3

[Rockinrob86]

good speaker ideas thanks
took amp to amp tech, he couldn't find anything astray
apparently he checked over everything in the circuit, esp at the usual prob spots
hmmm.....
so its getting a bit curly for me.
I feel that maybe I should check the resistors myself, just to be %100 sure
to check them properly do you have to take them completely out of the circuit?


This is how I learned to work on amps. The tech said "it looks good" but I knew something was off. You should do some reading, learn about the safety procedures, etc. get a copy of the schematic, and try to follow it while using a chopstick and looking at the amp. Use a resistor code guide and determine if the resistors in the amp are the same as the ones listed on the schematic. Then measure them. You dont have to remove them, although and resistors in parallel cannot be measured individually.

Ive had two amps with curiously low volume. Both needed to be biased (they were fixed bias, but nonadjustable. the factory resistor value was wrong.) They both also had several resistors severely out of spec. Originally, spec was +/- 20%. I usually make a chart and replace the ones outside of that. I listen to the amp when making any changes, as occasionally an out of spec resistor sounds really great. I have a gibson ga-20T with a very out of spec resistor in the trem circuit that was the key to why the trem circuit sounds amazing in that amp.

My gibson took me probably 30 hours to research, study, plan, make changes and analyze the changes before I had it perfect. That amp is now amazing and absolutely kills, but it never would have happened if I didnt know how to do the work myself. It is impossible to expect a working tech to put that much time in, unless you are paying them a few grand or something.