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Big amp is in storage so I took my Ampmaker SE5A to 1st rehearsal of new band on Sunday.
I was pleasantly surprised that it MORE than kept up with acoustic, piano, bass & drums.
So I got to thinking that I might even be able to gig small venues with it.
I decided to mod it to take a 6L6 instead of an EL84 in the hope of achieving a bit more headroom, so I ordered an octal socket and:
- hooked it up to green heater supply,
- shared the signal stuff and B+ with the existing nonal socket
- connected 1 & 8 to ground via the new looking 47uf cap and the 470r resistor (yellow lead that goes under the turret board).
It works with the 6L6 tube in (and the EL84 removed) but at a VASTLY reduced volume.
Can anyone spot what I might have done wrong?
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"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Does that account for the low volume?
Your 47uF cathode cap. Looks more like 4.7u and non polarised. Also quite old. Try just running with the resistor only. And in that state measure all the voltages on the 6L6.
EL84 is a very sensitive valve, needs less drive than a 6L6, that may be a factor, plus load impedance.
Drop that cap and measure voltages first though to see if your 6L6 is running with sensible dc conditions.
I'll give that plan a try tonight!
I was a bit tired yesterday and didn't want to electrocute myself. I'll get the multimeter out and stick one hand in my pocket over the weekend...
Not trying to put a downer on your plan just saying that be wary of chasing a fault that doesn’t exist.
There may be an ampmaker forum where someone has done similar and safely lowered the cathode resistor value or modded the preamp for more clean drive etc.
I don't have rose-tinted specs regarding a 6L6 magically transforming a 5watt amp into a gigging amp!
For about a fiver's worth of parts, I thought it was worth having a fumble about! (I already have 6L6s knocking about for my Blues Deville)
I'll take some voltages over the weekend and see where I get. I've built an 18-watter for my uncle since making this SE5A - just really enjoying learning about what goes on in valve amps!
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
So by using a "higher power" valve which is also a different impedance and not compensating for that, you will get less power output not more.
Think of it as being like putting a lorry gearbox in a car. Even though the box is *capable* of transferring much more power when used in a lorry, would you get more useful power to the wheels in the car?
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein