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You're welcome.
Tell me about the outcome.
Cheers,
Albert
Tell me about the outcome.
Cheers,
Albert
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Hi Albert.
Unfortunately, the package did not arrive,
so I end up having a quiet weekend.
I'll tell you something, as soon as I have news.
Cheers,
SIMPLINHOComment
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Hi Albert.
Yesterday came the pieces, and I've already set the stage inverter.
In fact, the LTD has a lot more gain. I followed the layout of the
Marshall 2550.
Now I need to do a test with a preamp, and make some adjustments.
I also have to check the voltages but for now seems to be working well.
Then I'll say something.
Cheers,
SIMPLINHOComment
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Hi Simplinho,
seems like you're making good progress
Cheers,
AlbertComment
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Hi Albert.
It seems so, but I still have doubts.
I just have only one bias probe, so I set the bias of the first valve,
and then the second, so far everything seemed fine, the problem
is that the trimmer of the first valve does also vary the values in
the second, and the opposite also happens.
Is there another way to do this?
How did you do in yourīs Dynacord?
These are the values:
-12AX7, with 406v B+
-1 - 277V
-2 - 28v
-3 - 44v
-6 - 264v
-7 - 29v
-8 - 44v
- EL34, with 420v B+
------1--------2-----
-1-(0.264v)--(0.448v)
-3-(418V)----(418V)
-4-(413v)----(413v)
-5-(-35v)----(-33v)
-8-(0.264v)--(0.448v)
What do you think, will be OK?
The amp seems to play well, but I wanted your opinion,
because you know much more of this. I am a beginner.
Again, thank you.
Cheers,
SIMPLINHOComment
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You don't need a bias probe. There is a 10 Ohm resistor from pin 1/8 of each EL34 to ground. You want 300mV across each of these (that equals 30mA per tube). So just measure from pin 8 to ground.
If you take your meter for these adjustments, you don't have to turn off the amp to change your bias probe.
0.264V is in the ballpark, 0.448V is a bit high. Go for 0.3V on both.
Oh, and check if those resistors are really 10 Ohms. They may have drifted over time.
Everything else looks fine.
When the trimmers are interactive, I use two meters simultaneously. Maybe you can borrow a second one?
Cheers,
AlbertComment
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Hi Albert.
In fact I am a beginner in these things, and a bit stupid.
In some cases there is a resistor of 1 ohm for that purpose,
that is why I have not listed them with the bias adjustment.
Iīve already adjusted to 350mv, is warmer, I read the values
in a table for the EL34, 300mV is a little cold.
I hope I'm not doing things wrong.
Resistorīs are in fact 10 ohm and they are new.
When everything is finished I will put some pictures.
Cheers,
SIMPLINHOComment
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Hi Simplinho,
350mV will be safe. I'd not go over 400 though. 300 is for long tube life.
And obviously you did everything right. After all it works, doesn't it?
Cheers,
AlbertComment
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Hi Albert.
It works, and connected to a cab with a 15" 50W loudspeaker
(Goodmans) has a sound very pleasant, even without a preamp.
And speaking of preamp, do you think your "JFET Bass" working
at 12V, will sound good?
And now for all who like these things I put here some photos of
the power-amp.
I hope you like it.
Thank you all, especially to Albert.
SimplinhoComment
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Hi Albert.
Thank youSweet. Congratulations!
.
This is the drawing I made for the panel of the preamp.
It will be a 1U panel, made of aluminum.
I just do not know when I'll start it, I have so many things to do and time does not stretch
.
But you can be sure that I'll post new developments as soon as I have them.
See you around.
Cheers,
SIMPLINHOComment
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