Have built Aikido on old National chassis before using the circuit board version. Hooked it up and lots of noise. Looked at it on scope and it is power supply 120HZ. The power supply is 270vdc with 1.6vac rms ripple. I thought that the Aikido had excellent PSRR. I am measureing 150mv ac at the output. Looked at voltages that I could find on Tubecad and they look ok as far as plate voltages being 1/2 of supply and cathode's being a few volts. I did this pretty quickly and did not use shielded cable on input wiring from input through volume to input of tube 1st stage. Looking at the voltage coming from 1st stage out i can see the 120hz at about a 1/3 rd of the level of ripple at the B+ connection at that tube. Any ideas. Tempted to just go ahead and build the board, but would like to understand first. Have noticed some typos on resister values on instruction sheet , does anyone know if the website has the latest values updated.
P.S. I am using AC heater voltage but this would be 60hz.
RG
P.S. I am using AC heater voltage but this would be 60hz.
RG
Not sure exactly what you mean by "breaking into ripple loop" but your still talking of PS noise injected into circuit. The point is that the Aikido is touted as having excellent power supply rejection. Broskie claimed 30db with no tweaking on his first try at it. If I correct 30db should be about 1000 times less and i'm only getting about 10db. I've also noticed other posts commenting on hum issues with Aikido. I figure that there has to be alot of other people that have built this pre and can comment.
RG
RG
All the power supply rejection in the world won't overcome a grounding problem.
30dB as a voltage ratio is 31 times, not a thousand; that's a more realistic number and almost certainly what JB meant.
FWIW, I've built two Aikidos using JB's boards and they were as quiet as any line stage I've used.
30dB as a voltage ratio is 31 times, not a thousand; that's a more realistic number and almost certainly what JB meant.
FWIW, I've built two Aikidos using JB's boards and they were as quiet as any line stage I've used.
Sounds like I struck a nerve. I'm not disagreeing with you just trying to understand the problem. I originally thought it was 32 times and then confused myself by reading the explanation on wikipedia!! If the problem were related to grounding issues i.e. ground loops then it would manifest as a 60hz problem. It being 120hz means after the full wave rectification. Correct??? BTW this is a P2P wiring project wired to the sockets directly for most of the project. I was going to try it before I wired the board. Maybe that would be the best thing to proceed with the board. The ones you have built, did they use SS power supply or tube rectifiers? Thanks for the insight.
RG
RG
There's a big 120Hz source in your preamp, just waiting for you to slip up so that it can bite. In fact, there are probably two of them, the HV and heater supplies. And in those supplies are all kinds of ripple currents which try to find their way into your circuit, usually via innocent-looking grounds.
The Aikidos that I built used solid state rectification and regulation.
The Aikidos that I built used solid state rectification and regulation.
Aikido update......... just finished the circuit board version and sounds great!!. Using battery supply for the heaters. Do i have to worry about the catode to heater voltage with the floating battery supply??
No problems that I can see so far. I'm using cheap Sovtek 6sn7s' for both stages does anyone think I would get a significant improvement with new Tungsols?
RG
No problems that I can see so far. I'm using cheap Sovtek 6sn7s' for both stages does anyone think I would get a significant improvement with new Tungsols?
RG
I am glad that your Aikido sounds great. I too have had many issues with hum and the cause may be due to many issues.
As for typos in JB's instructions, I just downloaded the newest version (Rev-A) PDF. One thing is that my older PDF mentions are the caps for the heater circuitry. These are optional if using AC but seem to be required for DC. The PDF that I used for assembly and part selection states that 10-100uF electrolytic should be used with voltage greater than heater voltage. I am using 22uF rated at 50V.
HOWEVER, the new version states that for these caps, the rating should be 100uF to 1000uF. It also calls these caps C5, which must be a typo, as the actual C5 is already listed correctly as 0.1-10uF. The second listing for C5 is 100uF to 1000uF, 16V electrolytic (the part designation must be a typo).
So, is 22uF for the heater shunting caps sufficient? Could this value be too low and result in some of my hum issues? I am using rectified DC for the heaters.
Charlie
As for typos in JB's instructions, I just downloaded the newest version (Rev-A) PDF. One thing is that my older PDF mentions are the caps for the heater circuitry. These are optional if using AC but seem to be required for DC. The PDF that I used for assembly and part selection states that 10-100uF electrolytic should be used with voltage greater than heater voltage. I am using 22uF rated at 50V.
HOWEVER, the new version states that for these caps, the rating should be 100uF to 1000uF. It also calls these caps C5, which must be a typo, as the actual C5 is already listed correctly as 0.1-10uF. The second listing for C5 is 100uF to 1000uF, 16V electrolytic (the part designation must be a typo).
So, is 22uF for the heater shunting caps sufficient? Could this value be too low and result in some of my hum issues? I am using rectified DC for the heaters.
Charlie
Dear Thread Originator,
Which tube sounds great is second issue, first concern is your
safety and safe and functional circuit Battery heater supply, DC heater supply, AC heater supply is your choice, BUT pls ref your DC supply to 1/4 of B+, not 1/2 B+ as my friend suggests. This is so because the uppoer triode cathod is at 1/2 B+.
Regards
Which tube sounds great is second issue, first concern is your
safety and safe and functional circuit Battery heater supply, DC heater supply, AC heater supply is your choice, BUT pls ref your DC supply to 1/4 of B+, not 1/2 B+ as my friend suggests. This is so because the uppoer triode cathod is at 1/2 B+.
Regards
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