Irene was born today

[Oswald1958]

Thanks to all the information on this forum, I've built my first tube amp. I'm naming her Irene. My wifes name. At first there was no volume. I could tap on the chassis and heard it loud and clear. The amp was working, but not through the input jack. I checked all the voltages. They were good. I then figured it had to be something with the input jack and wiring to the first tube. It was. Rewired. It's alive! It's Alive! I have several pre amp tubes available for the build. Some tubes cause motor boating. I switch tube positions....no more motor boating. What's with that? Should I use all new JJ's? Is this thing that tube sensitive? She does everything as advertised. 9:00 to 10:00 on volume....Oh my! Feedback and volume swell is there. Loud as hell. Volume controlled from guitar is required. It's a real amp.

I hear a faint buzz on some notes, that is not musical. I have no trim pot for bias yet. I put a 15K resistor there until I get my trim pot from Mouser. Hopefully tomorrow. I'm thinking that biasing will help. Can't hurt. Maybe it's my speaker. Maybe, I'm the only person that can hear the faint buzz at the end of certain notes. Maybe it's parasitic oscillation. I'll investigate.

I've tried the output transformer center tap shunt method for reading current at pin 3 on the output tube. I'll be damned if I can get a reading with my digital multimeter. I put my black lead on pin 3......red lead just before the 1K 25w power resistor.......nothing. What am I doing wrong? Is it my multimeter?

At least she's breathing....I have some tweaks ahead....It hisses...but no hum.

Maybe I should build a Liverpool.

[ScottW]

Hey congrats. I'm about to build my first Express.

As for the transformer shunt method, remember you have to set your meter to DC amps AND (at least in the meters I've seen) move the red lead to a different jack on the meter to handle current - usually marked "A".

[Humbucker]

Oswald, you're a full year older than me and can still hear insects...
But seriously, I've noticed the same but don't consider it a nuisance. I suspect it is inherent with this amp type? And you certainly can't hear it when blowing your heart out with Mountain, Cream and Purple...

Experienced builders will suggest some value changes and it's paramount to use first class tubes - i.e. JJ's or Tung Sol or NOS Telefunken and such for preamp and at least C-stamped Svetlana EL 34's for power amp.

I tried some New Sensor products (Sovtek, S-logo Svetlana) but after listening the amp decided to leave them as spares.

And yes, congrats! Burn Irene in and let your neighbours have it.

Bucker

[Oswald1958]

I was correct in thinking the trim pot would fix the buzzziness to certain loud notes and chords. I put the trim pot in (after waiting a month to receive it from Mouser) and the buzzzz is gone. Just great sustaining tone. Still has hiss. But, that's what ya get. I'm a happy camper. Now, How to properly bias.....I might just have to do the 1 ohm to ground method. Again...great site...all the info to build a wreck is here. I've proven it. Thanks to all. I'll post pic's soon (it looks a lot like all the other Express builds).

[Humbucker]

Put the trim pot where, at which point? Value? Might try the same just for fun.

[Oswald1958]

Humbucker, The Trim Pot was the 25K bias adjustment on the power board. My Tubes must have been under biased causing buzzzzz. To reduce Hisssss, you can change to lower gain pre amp tubes. 12AU7's virtually eliminate the hiss, but lower gain. Great for clean tone. The Tubestore has a chart that shows how the different 12A*7's compare. I'm thinking about using 12AY7's at 45% gain of 12AX7's. Half the Hissss?

[Humbucker]

O.K. no problem. I set the bias at -33 and had no trouble getting the tone.
I just have to get more gunk (check Weber netsite) for the speakers to eliminate ghost notes...

[Oswald1958]

Here she is. I've tweaked a bit. Overall, an awesome amp. My bright switch was noisy. I clipped it off and used the 100 pf cap for now. That is bright enough for me. I'll put a better switch in its place. I want to replace the tube sockets also. They squeal if they touch the metal base sides. Cheap ones. The metal caps don't stay in place and the springs are cheapo. These are pictures before the bright cap out and bias adjust isn't soldered in as yet. It is now, though! My first amp build. It was fun. I would like to build an 18 watt next. I'll work on some sound clips next.

[Drumslinger]

Nice work Oswald!

[5150loveeddie]

+1