New project finished, NEW PROBLEMS!

[pdf64]

I would also try lifting that 1meg resistor off of the input of the output tube.

That seems a bad idea? The power tube needs a grid leak resistor, but it should be lower in value, the limit (ie max) is 500k in cathode bias.

[John_P_WI]

This is the 3rd time I have said it, get the power tube grid under control. Change the 1M to a 150k or 220K or 470K like pdf above suggests. Also I suspect your signal level is too high, hence the previous question asking the p to p level.

You cannot remove the 1M the power tube loses the ground reference.

[Ranalog]

I do it. I change the 1M resistor for 150k.


The same rare noise

I attached a file recorded with my phone with the volume at half (5).

I think that the problem come for the volume section. If I suprime the volume the amps sound amazing but I need a volume control and gain control.

I change the pot but it isnt the fail!

[pdf64]

After the gain control there's a 220k grid stopper, bypassed by 500pF.
Try removing that 500pF cap.

Also I suggest adding a 22k grid stopper to the last pre-amp stage.
Grid stoppers should be mounted at the tube socket terminal.

[passfan]

Would also be nice to jumper across your effects loop to see if something is wrong there. It's always best to make them work first and then add all the extra's later.

[Ranalog]

pdf64 this solution reduce a little the crack but the amp lost all caracher, When I play hard I can hear the cracks

the amp runs like before, when I put the volume at 10 I hear the best sound I hear in many amps of about 5-10W.


Now when I put the volume between 2-8 no affects to the LOUD, The crack sound desapear but all notes have a lot of punch.

[Stevem]

Jump out the effects circuit and then jump out the volume control and if the amp then works normal when using differing levels of the gain control you simple have a bad volume pot!

[Ranalog]

In the next audio you can hear:




In 00:07 the pot is at 3 of 10
In 00:13 the pos is at 5 of 10 ( the loud dont change)
In 00:17 the pot is at 7
In 00:22 the pot is also at 7 but I play hard. CRACKKKKKKKK
In 00:27 the pot is at 9-10 the LOUD change, also the sound. I want this sound always!

I chasing bad luck...

[Ranalog]

I found one solution.

I change the pot for three of equal value ( 250k) CRACk on the three


I put 25K and now I dont have any crack....... why?

Now sound incredible!

[V2]

I suspect that your problem lies with the design of your effects loop. Here are a couple of potential concerns off the bat (perhaps others could chime in):

- your volume control doubles as the effects loop SEND level.
- the SEND resistance helps to determine the output impedance of the send stage. here you have a cathode follower with low output impedance, but the 250k pot is otherwise very high. the 25k pot would be better for a send; you might even try 10k.
- for the loop to be less sensitive to hum, you might want to increase the coupling cap off the cathode follower to 10uF.
- your recovery stage doesn't seem to have a grid leak (1M would be fine) or a grid stopper (10k or more).

But maybe I am all wrong... it's been a while since I read Merlin's FX chapter....

[Ranalog]

Do it!


Sound amazing!


Thanks every body!

[Ranalog]

One more thing:


If I want to put a 6v6 intead of the 6l6. What I need to do? I need to mod something?

[Stevem]

To run a 6v6 start off with a 470 cathode resistor, 5 to 7 watts is more than enough.
What you want is for the tube to idle at 45ma.
You need to check your peak drive signal into the grid beacause to do NOT want that audio signal to drive the current to more than 47ma!

You can check that drive signal with your meter set for AC volts.
Good to hear it's working for you!

[Ranalog]

I have made this modificactions

I put the 470r in the cathode of the 6v6 and a 1ohm resistor to read the current.

I read 27mV..... very low...

What I need to do?

[Stevem]

I would say that a 300 ohm cathode resistor should get you idling right in mid 40s where you want to be.
This is assuming that the 6v6 plate voltage will be between 245 and 255 or so once that 300 ohm resistor is in place!