Yeah, I'll probably do that.
One of the sockets is VERY tight, I always wonder if I'm going to break a tube with that one.
Funny enough it wasn't that socket that broke a tube this time.
One of the sockets is VERY tight, I always wonder if I'm going to break a tube with that one.
Funny enough it wasn't that socket that broke a tube this time.
Would it be safe for me to run this preamp with just tubes in one channel?
This would at least allow me to test and figure out any problems while I wait for my replacement tubes.
This would at least allow me to test and figure out any problems while I wait for my replacement tubes.
Yes, you can run the preamp with tubes in one channel, no problem.
Did you say that you had the volume pot connected at the output? It should be at the input.
Did you say that you had the volume pot connected at the output? It should be at the input.
OK, I will try running just one channel.
Yes I currently have the volume pot on the output, that made sense to me at the time.
I will be relocating that to the input after a few good points were given.
I'm hoping to have my replacement pair here by Saturday and I should have my pot rewired by then so I should be ready to rock.
I have already ran grounds from I&O to star, from Pot L&R to star and from star to third prong.
Yes I currently have the volume pot on the output, that made sense to me at the time.
I will be relocating that to the input after a few good points were given.
I'm hoping to have my replacement pair here by Saturday and I should have my pot rewired by then so I should be ready to rock.
I have already ran grounds from I&O to star, from Pot L&R to star and from star to third prong.
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Actually I've found the best way to do earthing is like this : Use the normal practice of star earthing all the electronics. But don't connect the star earth point directly to the mains earth.
Instead use a pair of back-to-back diodes, in parallel with a 10R resistor, then connect the mains earth (and any other metallic chassis parts). You can see what I mean on this circuit diagram, which shows an amp power supply, but also is the power for an aikido. It's located at the bottom right hand corner.
Instead use a pair of back-to-back diodes, in parallel with a 10R resistor, then connect the mains earth (and any other metallic chassis parts). You can see what I mean on this circuit diagram, which shows an amp power supply, but also is the power for an aikido. It's located at the bottom right hand corner.
Attachments
FANTASTIC, I think I have a pair of 4002's in my junk box, it's full of goodies.
The 10R I think I have leftover from the unused bits in the Aikido kit.
It almost looks like the back to back diodes create a sort of half wave....maybe so only DC has ground and the resistor is for ballast?
The 10R I think I have leftover from the unused bits in the Aikido kit.
It almost looks like the back to back diodes create a sort of half wave....maybe so only DC has ground and the resistor is for ballast?
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WOOOOT!
Looks like my replacement tubes departed the USPS sorting facility 140 miles away at 0:00:00 this morning.
That means I should have them today.
Yippee!
Looks like my replacement tubes departed the USPS sorting facility 140 miles away at 0:00:00 this morning.
That means I should have them today.
Yippee!
OK, I have the pot rewired to the input and the ground modified with 2 diodes and a 10Ω 1W resistor.
IT WORKS!!!!!!!!!
One problem,the left channel has a very noticeable hiss that is independent of the volume control.
The right has a hiss but it is very faint and you can't hear it when even quiet music is playing.
Even with the source turned off there is still a hiss on the left channel.
I will go through and check solder points on the left side.
Any other thoughts?
IT WORKS!!!!!!!!!
One problem,the left channel has a very noticeable hiss that is independent of the volume control.
The right has a hiss but it is very faint and you can't hear it when even quiet music is playing.
Even with the source turned off there is still a hiss on the left channel.
I will go through and check solder points on the left side.
Any other thoughts?
I have not tried moving tubes yet, but ....... i did notice also that when the static is playing with no source material (source connected) the woofer cone will flex out slowly and then back to neutral once every 10 seconds or so.
The woofer moving sounds almost like a power amp thing. Not sure the cap-coupled aikido could transmit signals slow enough to do that. The calculation depends on the cap you used at the output of the aikido, and the input impedance of your power amp.
Does this happen on both channels or just one? If just one, swap the left/right leads going from the pre to power amp. Is it the same channel that hisses? If so, swap the tubes left to right and see if it moves.
Does this happen on both channels or just one? If just one, swap the left/right leads going from the pre to power amp. Is it the same channel that hisses? If so, swap the tubes left to right and see if it moves.
Cone movement happens on both channels.
The hiss is louder on the left channel than the right.
The hiss slowly gets louder over a 15 second period of time (tube warmup?).
Once the level of hiss stabilizes the hiss is independent of volume setting.
I believe I chose 1.0uf obbligato's for my output caps.
I don't have woofer movement with just my blackberry plugged directly into the amp.
Input impedance of the LM4780 is 22k.
I will put some time into this tonight after the kids are in bed.
The hiss is louder on the left channel than the right.
The hiss slowly gets louder over a 15 second period of time (tube warmup?).
Once the level of hiss stabilizes the hiss is independent of volume setting.
I believe I chose 1.0uf obbligato's for my output caps.
I don't have woofer movement with just my blackberry plugged directly into the amp.
Input impedance of the LM4780 is 22k.
I will put some time into this tonight after the kids are in bed.
I have 3 sets of 6cg7's one pair likes to run "hot" the other two do not. I have a feeling it is tube related.
One of the pairs hisses like mad at 10mA and if I drag it back to about 6 mA they are fine and the other pair hiss unless they are in the phono pre running around 4mA...
Gotta love the tubez...
One of the pairs hisses like mad at 10mA and if I drag it back to about 6 mA they are fine and the other pair hiss unless they are in the phono pre running around 4mA...
Gotta love the tubez...
Reading through the manual here says that with 6CG7 (what I have) at 300V (What I Have) at 1k cathode you get 26mA.
It was suggested to run these tubes at 10mA each.
The manual says to run a recommended 470Ω on the cathode for my 6CG7's.
At 300V B+ what am I getting for cathode current?
I'm not understanding this formula in the manual for cathode current.
It was suggested to run these tubes at 10mA each.
The manual says to run a recommended 470Ω on the cathode for my 6CG7's.
At 300V B+ what am I getting for cathode current?
I'm not understanding this formula in the manual for cathode current.
At 300V how do I calculate the MU of the 6CG7.
I'm having a difficult time trying to follow the charts.
I'm having a difficult time trying to follow the charts.
More info on the cone movement.
With the preamp connected to the amp.
Amp on, preamp off.
Both woofers slowly pull in and hold.
After turning off the amp the speakers make a soft pop and return to neutral.
With no input on the amp.
The woofers remain neutral.
Connect an input from my blackberry to the amp and the amp functions properly.
Should I increase or decrease my output cap value?
Someone mentioned an impedance issue being a possible culprit.
Maybe it is something in the output stage of the Aikido?
Could the hissing be a symptom of whatever is making my woofers move?
With the preamp connected to the amp.
Amp on, preamp off.
Both woofers slowly pull in and hold.
After turning off the amp the speakers make a soft pop and return to neutral.
With no input on the amp.
The woofers remain neutral.
Connect an input from my blackberry to the amp and the amp functions properly.
Should I increase or decrease my output cap value?
Someone mentioned an impedance issue being a possible culprit.
Maybe it is something in the output stage of the Aikido?
Could the hissing be a symptom of whatever is making my woofers move?
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To get your cathode current just take a voltage reading across the cathode resistor and divide the voltage by the resistor value.
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