Hi everybody.
I just finished a new project. A 5W SE amp, with one tung sol 6l6 and 2 12ax7. The power transformer is a 190-0-190 from amp maker and the OT is a 5k also from ampmaker.com.
The preamp is a schematic that I use for a 50w clean amp with 2 6l6.
It turns out that the amp sound very nice when the volume is at minium. When I put it at 4 its start to CRACKKKKKK and the sound lost all sustain. It's a fuck sound.
Here you can see the schematic, what do you think about it?
EDIT:
EDIT:
When I put the volumen at full, and I up the gain I can hear a clean sound until the 4/6 gain level after I can hear a overdrive.
The crackked and unsustained sound appears when I down the volume from the full (10)
New project finished, NEW PROBLEMS!
Moderators: pompeiisneaks, Colossal
New project finished, NEW PROBLEMS!
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Last edited by Ranalog on Fri Apr 10, 2015 10:42 am, edited 1 time in total.
Re: New project finished, NEW PROBLEMS!
have I a low HV????
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Stevem
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Re: New project finished, NEW PROBLEMS!
I can not open up your schematic posting to view it!
With a PT of 190-190 you should have some 266 of B+ with no tubes in the amp,how much current is the PT you are using rated for?
If the PT was in a former life powering a push pull A/B amp then you may be right at the edge of having enough current for the class A build you did?
What is the value of the cathode resistor that you are using on the outout tube?
If you have more than 13 to 16 volts of drive signal coming into pin 5 of the output tube than you are driving the hell out of it and that could be a piece of your problem also!
Please post the voltages you have on the preamp tubes plates and cathodes (pins 1 and 6 and 3 and
and also the voltage readings from the output tube pins 3-4 and 8?
With a PT of 190-190 you should have some 266 of B+ with no tubes in the amp,how much current is the PT you are using rated for?
If the PT was in a former life powering a push pull A/B amp then you may be right at the edge of having enough current for the class A build you did?
What is the value of the cathode resistor that you are using on the outout tube?
If you have more than 13 to 16 volts of drive signal coming into pin 5 of the output tube than you are driving the hell out of it and that could be a piece of your problem also!
Please post the voltages you have on the preamp tubes plates and cathodes (pins 1 and 6 and 3 and
and also the voltage readings from the output tube pins 3-4 and 8?When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: New project finished, NEW PROBLEMS!
You can see all voltages un the pic I attached
Re: New project finished, NEW PROBLEMS!
1M power tube grid leak seems a little high... What's the signal level voltage p to p at the power tube grid?
Re: New project finished, NEW PROBLEMS!
Sorry p to p??
Un the pin 5 Ive 0 volts
Un the pin 5 Ive 0 volts
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: New project finished, NEW PROBLEMS!
Your main cathode resistor off of pin 8 of the output tube needs to be about 180 ohms,then a 1 ohm resistor from the 180 to ground, what do you have for resistors there now?
All of your other voltages look ok!
All of your other voltages look ok!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: New project finished, NEW PROBLEMS!
Voltage peak to peak, I'm guessing you are driving the power tube too hard, and the grid signal voltage is too high. Especially since you are showing a cathode voltage of 8.5v,Ranalog wrote:Sorry p to p??
Un the pin 5 Ive 0 volts
Steve is correct about the cathode R's of the power tube, certainly you do not have 2) R89 ohm resistors in parallel!!!! IF so, you have about 1/4 the needed resistance.
I'd start by looking at the grid leak and cathode R of the power tube - get things under control there first.
Re: New project finished, NEW PROBLEMS!
What I need to do?
I change the cthode rsistor of the 6l6 for a 1k 5W and Its soun equal.
Why the sound is good when the Volume is at 10?
I ve 245 V on the pin 3 of 6l6
I change the cthode rsistor of the 6l6 for a 1k 5W and Its soun equal.
Why the sound is good when the Volume is at 10?
I ve 245 V on the pin 3 of 6l6
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: New project finished, NEW PROBLEMS!
Why 1k? Now your 40 % too high, do not go any higher than 250 ohms!
Across that .089 ohm resistor ( bias check) you want to read about 70 to 75mv at idle with a meter set for dc volts.
Across that .089 ohm resistor ( bias check) you want to read about 70 to 75mv at idle with a meter set for dc volts.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: New project finished, NEW PROBLEMS!
I put two 470 in parallel to get 220ohms and one resistor of 1 ohm. I mesured the voltage in the 1 ohm resistor and I get 50mV.
The sound doesnt change. with the volume pot at full the sound is good with the pot less than 10 its a big shit
The sound doesnt change. with the volume pot at full the sound is good with the pot less than 10 its a big shit
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: New project finished, NEW PROBLEMS!
Ok , at least you have the output stage at a workable idle now.
At the input grid of V2A are you reading any dc voltage?
At the input grid of V2A are you reading any dc voltage?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: New project finished, NEW PROBLEMS!
The V2 A is the cathode follower stage
And in the grid (pin2 ) I read 93V
in the V2b --> 0V
V1 both grid -->0V
In the cathode of the 6l6 I ve 0V with the volume at 0
about 15V when the pot is between 3-8 an 0 again at 9/10
And in the grid (pin2 ) I read 93V
in the V2b --> 0V
V1 both grid -->0V
In the cathode of the 6l6 I ve 0V with the volume at 0
about 15V when the pot is between 3-8 an 0 again at 9/10
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: New project finished, NEW PROBLEMS!
If you take a clip lead and jump the input at V1B (grid)to the input (grid) of V2B, does the amp sound good but just loud enough?
I would also try lifting that 1meg resistor off of the input of the output tube.
I would also try lifting that 1meg resistor off of the input of the output tube.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: New project finished, NEW PROBLEMS!
It'snt a problem of loudness.
Doing that you tell me of the V1b and V2b the loud is very very low and the character of the amp change.
If I eliminete the 1m resistor Its sound worse
Look this:
why??????????????????
If I put the volumen pot at 2 and gain at 3 I can hear a "good sound" when I play hard the guitar the sound start to break. The LOUDNESS (0-10) 3
If I play hard the guitar I can start to hear some breaks
IF I up a little the volume pot (louds up a little to) sounds BREAKs a lot.
If I put the volumen at 10 I loud is more than 5W and I can here the sound very well.
If I eliminete the 1m resistor Its sound worse
Doing that you tell me of the V1b and V2b the loud is very very low and the character of the amp change.
If I eliminete the 1m resistor Its sound worse
Look this:
why??????????????????
If I put the volumen pot at 2 and gain at 3 I can hear a "good sound" when I play hard the guitar the sound start to break. The LOUDNESS (0-10) 3
If I play hard the guitar I can start to hear some breaks
IF I up a little the volume pot (louds up a little to) sounds BREAKs a lot.
If I put the volumen at 10 I loud is more than 5W and I can here the sound very well.
If I eliminete the 1m resistor Its sound worse