Here's the thing, well two things, with the Aikido
Because everything is direct coupled (no caps) all four triodes in each channel are codependent.
Imbalances between triodes in each tube can affect both triodes in its neighbour in the same channel. This puzzled me at first when I would switch the same four tubes around but couldn't get the same voltage measurements. For instance: I'd measure the balance between input tube sections but only changing the output tube would give different input tube measurements.
Get your 12Vac up and running then, if you wish, you may start "balancing" your Aikido.
Here's the procedure I use. It takes a lot of words to describe but it's really quite simple and once you've been through it once or twice it will be easy.
To quantify a tube's balance I measure the voltage across the anode and cathode right at a tube socket pins. Start with the input tubes, measure across pin 1 and pin 3 and note the voltage. Then measure across pin 6 and 8. Ideally, the voltage should be the same on both triodes. I consider a voltage delta up to 5 OK but I've seen as high as 9 or 10 at times. This is, of course, ONE measure of how well matched the triodes within one tube are.
Don't be too discouraged if the delta between triodes is high. Power down and leaving the same tube in the input socket, swap the output tube on the same channel with one of the tubes from the other channel.
Input tube imbalance can "pull" the imbalance around on the output tube and vice versa.
Once you've tried all three other tubes in the output socket the one that gives the lowest delta on the input tube likely has the best balance of the three remaining tubes.
Swap your best input and output tubes around in the same channel and the lowest delta in the input tube position is likely your best balanced tube.
Using this method find the best two balanced tubes and use these as the input tubes. I find it's best to use the ones with the best balance (smallest delta) in the input position and relegate the less well balanced tubes to output duties.
GOOD LUCK!
Steve
Because everything is direct coupled (no caps) all four triodes in each channel are codependent.
Imbalances between triodes in each tube can affect both triodes in its neighbour in the same channel. This puzzled me at first when I would switch the same four tubes around but couldn't get the same voltage measurements. For instance: I'd measure the balance between input tube sections but only changing the output tube would give different input tube measurements.
Get your 12Vac up and running then, if you wish, you may start "balancing" your Aikido.
Here's the procedure I use. It takes a lot of words to describe but it's really quite simple and once you've been through it once or twice it will be easy.
To quantify a tube's balance I measure the voltage across the anode and cathode right at a tube socket pins. Start with the input tubes, measure across pin 1 and pin 3 and note the voltage. Then measure across pin 6 and 8. Ideally, the voltage should be the same on both triodes. I consider a voltage delta up to 5 OK but I've seen as high as 9 or 10 at times. This is, of course, ONE measure of how well matched the triodes within one tube are.
Don't be too discouraged if the delta between triodes is high. Power down and leaving the same tube in the input socket, swap the output tube on the same channel with one of the tubes from the other channel.
Input tube imbalance can "pull" the imbalance around on the output tube and vice versa.
Once you've tried all three other tubes in the output socket the one that gives the lowest delta on the input tube likely has the best balance of the three remaining tubes.
Swap your best input and output tubes around in the same channel and the lowest delta in the input tube position is likely your best balanced tube.
Using this method find the best two balanced tubes and use these as the input tubes. I find it's best to use the ones with the best balance (smallest delta) in the input position and relegate the less well balanced tubes to output duties.
GOOD LUCK!
Steve
Thanks Steve!
I measured the voltages across 1,3 and 6,8. All tubes measure almost same voltage of around 40 volts (+/- 1 volts). For now I'm not planning to swap tubes to test - chief reason being time difference between power up to power down and waiting for voltages to drain. Is it ok to swap tubes when the B+ voltage hovers around 40+ volts after power down? I didn't solder a bleeder resistor as i don't have 100k resistor with me - max I've is 6.8k one.
Can't wait to hear the output! By the way , I'm going to connect it to my Jean Hiraga mono blocks (30W each). It's replacing Kualtron buffer .
Hi Steve!
I'm not aware of input impedance of my monos. But Aikido seems to be working just fine. To be frank, initially music sounded all muddy.. i thought let it run for sometime before i go back to my passive set up.
But! after about 30 minutes or so, music started to sound clean. I'm not good with reviewing/putting in words about the music response but tube seems to make the music bit rounded - might be a good combination for my bit sibilant DAC.
I can hear hissing sound in the background. I've not grounded the pre amp board. Pdf suggests 0.01uf cap in parallel with 10ohm resistor. Can i make use of 0.1uf cap instead?
Pic of pre board in the chassis: chassis is still a WIP.
Attachments
0.1 cap is fine.
If your amp has a fairly low (less than 25K ohm) input impedance the 0.1uF output caps on your 12Vac might be a little low and restrict bass response. You might want to go to say, 1.0uF.
I like to break new components in for AT LEAST 50 hours before even starting to judge sound quality. Then at least another 50 to 100 hours before I'm comfortable passing judgement. Of course if you replace a tube or an output cap say, the break in starts all over again.
S.
If your amp has a fairly low (less than 25K ohm) input impedance the 0.1uF output caps on your 12Vac might be a little low and restrict bass response. You might want to go to say, 1.0uF.
I like to break new components in for AT LEAST 50 hours before even starting to judge sound quality. Then at least another 50 to 100 hours before I'm comfortable passing judgement. Of course if you replace a tube or an output cap say, the break in starts all over again.
S.
I have been reading this thread and would like to thank Steve for all his help here and on the WOS forum. Useful info!
I am almost finished with soldering my Aikido 12Vac board and I am stuck at the J1 and J2 jumpers. I can not seem to find any info about these. Does anyone have recommendations for what to use here?
I am almost finished with soldering my Aikido 12Vac board and I am stuck at the J1 and J2 jumpers. I can not seem to find any info about these. Does anyone have recommendations for what to use here?
If you are using E88CC (or equivalent) just a piece of cut off resistor lead will do for J1 and J2. These ground the internal shield (pin 9) in the tubes. Leaving a small loop in one of them will serve as ground connection when making voltage measurements.
If you are building the 12AU7/ECC82 version pin 9 is connected to the filament centre tap. DON'T USE A JUMPER!!!! Just omit J1 and J2 or put a small value film cap in. I'd just leave J1 and J2 empty if building this version.
Cheers, Steve
If you are building the 12AU7/ECC82 version pin 9 is connected to the filament centre tap. DON'T USE A JUMPER!!!! Just omit J1 and J2 or put a small value film cap in. I'd just leave J1 and J2 empty if building this version.
Cheers, Steve
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