Hi X,
I am looking for a way to supply some tube heaters with 6.3vdc. Do you think one of your single rail SLB boards would do the job? Specific to my application the tubes will require 5A total at 6.3vdc, my transformer has 2 6.3vac secondaries rated at 4A each that I can use to feed the SLB.
I am looking for a way to supply some tube heaters with 6.3vdc. Do you think one of your single rail SLB boards would do the job? Specific to my application the tubes will require 5A total at 6.3vdc, my transformer has 2 6.3vac secondaries rated at 4A each that I can use to feed the SLB.
Ah ok, thanks. So the drop is 3V fixed, I was thinking it may be a % of rectified DC.
Sorry I missed this earlier and thank you for bumping it.
It’s a strange one. I have never had my speakers make a tapping noise. 200Hz - can you tell me more about the setup? What is the current draw? No LEDs is odd.
Only thing I can think of off the top of my head is you may have an interaction of the SLB and your amp and it’s “Motorboating”. A low frequency oscillation.
Look at the feedback resistors R17/18. Try a larger value like 15R and see if that helps. Or maybe try smaller value like 4.7R.
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Hi XRK, I am not sure what other details you are looking for but here's a few. It is dual mono with Antek 3228s, all parts for the SLB bought from the Mouser BOM provided. The BA3 FE is biased at 1v and the output boards are biased at .25v for now with matched sets from the DIYAudio store. The noise was present at it's current volume regardless of whether the BA3 was biased or not. As noted, its not volume dependent and music will cover it. The noise is identical in both channels. The only thing connecting both channels is chassis ground and the power switch. I suppose I could disconnect the transformer from one channel or the other and see what happens. For each channel, input grounds go to FE ground which goes to PS ground which goes to chassis ground using the provided earth ground connection. Output boards have no ground, and speaker grounds go to each channel's PS ground. The transformer's static shields also go to chassis ground.
If you can make a diagram like this, it would be very helpful to debug. Plus a few photographs so we see what we are dealing with. You might have a ground loop and it’s in the 180Hz or 240Hz range.
Grounding topology is very important. There needs to be a distinction between “dirty ground” and “clean ground”. They cannot touch directly, and need to be separated by an NTC or 10ohm ground loop breakers.
Try disconnecting one channel (remove power from SLB to amp) and disconnect audio input to that channel. See if that makes it go away.
Grounding topology is very important. There needs to be a distinction between “dirty ground” and “clean ground”. They cannot touch directly, and need to be separated by an NTC or 10ohm ground loop breakers.
Try disconnecting one channel (remove power from SLB to amp) and disconnect audio input to that channel. See if that makes it go away.
Hi SWS,
I checked out the pics of BA-3 build on the thread, SWEET! Nice job.
Looking at the SLB's build details are a bit tough because of them being installed, but the flying leads for the pass transistors look a bit long and cross across the chassis. I wonder if the long'ish leads are picking up interference or possibly causing oscillations? I used this psu in several different builds but the leads were never longer than 5-6 inches.
Just a thought...Try assembling another set of BJT's with shorter leads mounted on a temporary heatsink positioned above the SLB.
I want to build an hifi tube amp with a push pull of kt88. The only problem I face is creating an alternative to the LT module.
So i want to replace it with fast diodes, do you have any recomendation? Also should i use capacitors in paralelle with diodes, or is it just slowing down the recovery time, creating another form of noise (noise from slow diodes) ?
Thank you.
So i want to replace it with fast diodes, do you have any recomendation? Also should i use capacitors in paralelle with diodes, or is it just slowing down the recovery time, creating another form of noise (noise from slow diodes) ?
Thank you.
I have seen people use film caps in parallel with the diodes. The more important one is to use a tuned RC snubber at the transformer input. There is provision for an RC there. Use the Quasimodo bell ringer circuit to test and adjust for optimal damping. I am not knowledgeable about slow vs fast rectifier diodes. You would think slow is better - less spikes?
Linear Audio sells individual articles, they don't require you to purchase the full volume in hardcopy form:
Soft Recovery Diodes Lower Transformer Ringing by 10-20X: Linear Audio magazine
Hi Soundwavesteve,
Thanks for the diagram. I am not sure how the BA-3 front end board is wired but it appears to be a board made for stereo output with a common ground. It is being used to drive two "monoblock" output stages, but the stages share a common ground and have +32v provided by two separate rails (one from each SLB). It could be that the BA-3 FE board doesn not like to have two different +32v inputs? They could be beating against each other. Try running only one side at a time by disconnecting the 32v to the unused side of the FE board and power off the trafo on the unused channel to see if the 200Hz noise is still there. Alternatively, connect the BA-3 FE to only 1 of the SLB's. Please report back with your findings.
Thanks,
X
Thanks for the diagram. I am not sure how the BA-3 front end board is wired but it appears to be a board made for stereo output with a common ground. It is being used to drive two "monoblock" output stages, but the stages share a common ground and have +32v provided by two separate rails (one from each SLB). It could be that the BA-3 FE board doesn not like to have two different +32v inputs? They could be beating against each other. Try running only one side at a time by disconnecting the 32v to the unused side of the FE board and power off the trafo on the unused channel to see if the 200Hz noise is still there. Alternatively, connect the BA-3 FE to only 1 of the SLB's. Please report back with your findings.
Thanks,
X
Hi X,
The BA3 FE board is dual mono as well. It has V+, V-, in, out and a ground per side. I verified via MM that when disconnected the grounds are not connected on the board itself. The BA output boards do not have V- or a ground. I performed two tests for each side and the tapping sound remained at all times. First test I did as you requested and the tapping remained on the powered channel. Second test I disconnected everything from the unpowered SLB, including chassis return, and the tapping remained on the powered channel. (the neutral trany wires are all wired together with a wire nut and the static shields are connected to chassis ground; I didn't touch those) I didn't count the taps this time, but it seemed like one side was faster than the other; it was still rapid, around or above 200 every time. It was ~272 the other day. I also tried running the amp from another wall socket on another circuit with no change. Additioanlly, still none of the LEDs lit up.
Side question, if I start poking around the power supply do the big caps discharge themselves though the design of the circuit or do I need to manually discharge them?
The BA3 FE board is dual mono as well. It has V+, V-, in, out and a ground per side. I verified via MM that when disconnected the grounds are not connected on the board itself. The BA output boards do not have V- or a ground. I performed two tests for each side and the tapping sound remained at all times. First test I did as you requested and the tapping remained on the powered channel. Second test I disconnected everything from the unpowered SLB, including chassis return, and the tapping remained on the powered channel. (the neutral trany wires are all wired together with a wire nut and the static shields are connected to chassis ground; I didn't touch those) I didn't count the taps this time, but it seemed like one side was faster than the other; it was still rapid, around or above 200 every time. It was ~272 the other day. I also tried running the amp from another wall socket on another circuit with no change. Additioanlly, still none of the LEDs lit up.
Side question, if I start poking around the power supply do the big caps discharge themselves though the design of the circuit or do I need to manually discharge them?
R7 and R8 are supposed to discharge the caps slowly via the LEDs. Since your LEDs do not light up, the only possible answer is that the LEDs are either dead (unlikely) or you have them installed in reverse. If they are reversed your caps will not discharge. I like to use a 5W 10ohm power resistor to discharge caps. The tapping appears to be something particular to your amp and is not a ground loop if you tested each side by itself then and the BA3 FE has provision for a dual mono PSU. All I can suggest now is to use a DMM in AC mode and measure the ripple after the cap Mx pass transistor and at the input to the amp. Is the voltage fluctuating at 200Hz? How do you know it is 200Hz? If you have an O-scope to determine the 200Hz vs 272Hz, please show us the waveform of the amp output. And I think it is odd to call 200Hz a tapping noise. 200Hz is a high speed buzz or hum. Tapping is sub 10Hz impulses. Is there a sub 10Hz noise superimpsoed on the 200Hz buzz? If you can record the sound and post a video or mp3 that would also be helpful. Finally, an O-scope if you have one, would be very helpful here.
Slow 1N diodes have a 'lower slope' in the recovery time than UF diodes, it means they dont 'ring' the transformer as hard, but have a longer recovery time, so they make it 'rings' longer . My understanding is... it is almost a unsolvable quiproquo as adding capacitance in paralelle to diodes slow the recovery time, and make the spike in dv/dt less fast/sharp, making uf diodes behave like 1N diodes.... (I think of this like an op amp slew rate).
I mean if I use ultra fast diodes with soft recovery, is it the best you can get get, and dont use caps in parallel.
I know snubber before the bridge is ideal (I learned this from Mark Johnson), but does it means it can just put any diode, and it will just be perfectly smooth ?
I would love to see Mark Johnson take on my explanation, or scolding if I missed something
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