Yes.
If you get -23.4V and +23.4V, that is a good indication that the transformer centre tap is centred which is good. It also indicates that the capacitors are working properly in V+ and V-, in that both have the same amount of ripple smoothing.
I suppose you can get an idea of the power supply voltage ripple by setting your meter to AC mV and measuring V+ to Gnd and V- to Gnd.
How much capacitance do you have in your power supply?
If you get -23.4V and +23.4V, that is a good indication that the transformer centre tap is centred which is good. It also indicates that the capacitors are working properly in V+ and V-, in that both have the same amount of ripple smoothing.
I suppose you can get an idea of the power supply voltage ripple by setting your meter to AC mV and measuring V+ to Gnd and V- to Gnd.
How much capacitance do you have in your power supply?
My last gasp, and it's a reach, but grounding can be finicky. Most people use dual secondaries with the diyAudio PS board but in this case it is a centre tapped secondary. Now does the + and - ground on the board being only connected at either end become a problem?
I don't have the knowledge to answer that.
But a possible try is to connect the V+ and V- capacitor grounds together at the bottom of the board, so that the two sides of ground are stitched together.
What do you think, 6L6?
I don't have the knowledge to answer that.
But a possible try is to connect the V+ and V- capacitor grounds together at the bottom of the board, so that the two sides of ground are stitched together.
What do you think, 6L6?
My M2 has hum as well and it helps when I put a mu metal hat on the Edcor. I found an SPL app for my android phone and it actually has a FR chart as well, don't have my phone in front of me and don't recall the name offhand but should be easy to find something like this. I held the phone up to the speaker (Fostex Fe126 in old FH cabinet so high sensitivity) and I can see a spike at 60Hz and 120Hz quite clearly. Even with the tin hat on it still hums so I think the next step would be to try a snubber.
There are two solder joints that appear iffy. I have circled them in red.
In bipolar supplies with centre tapped transformer, the ground that is connected to the centre tap is usually one conductor. Because the diyAudio PS board was designed for versatility, the ground conductor is split into two. What I had suggested in my previous post was to try to joint the two halves of ground at a few more places, as marked in red.
Sometimes in the case hum or no hum, something that seems as minor as that may have quite an effect. However, I am most certainly not certain (being just an amateur diyer) so I hope someone with electronics knowledge will jump in. I may be totally out to lunch.
Jim, I'm not sure whether this has been tried.
In bipolar supplies with centre tapped transformer, the ground that is connected to the centre tap is usually one conductor. Because the diyAudio PS board was designed for versatility, the ground conductor is split into two. What I had suggested in my previous post was to try to joint the two halves of ground at a few more places, as marked in red.
Sometimes in the case hum or no hum, something that seems as minor as that may have quite an effect. However, I am most certainly not certain (being just an amateur diyer) so I hope someone with electronics knowledge will jump in. I may be totally out to lunch.
Jim, I'm not sure whether this has been tried.
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Hi Music,
I've been reading through this thread and finally just zoomed in on your first pic and see that you are using a transformer from SumR. Coincidentally my first amp build (Aleph J) also used a toroid from them and had the exact same problem with buzzing. Not only through the speakers but from the toroid itself. Is this a similar issue? I would reach out to them and speak to Richard the owner as I did and see if there is something he may be able to help you with. He was a very helpful, kind man who stands behind his products and even sent out a new transformer to me after some trouble shooting with me over the phone. Let him know that your amp is a Class A, FirstWatt/Pass Labs design. He has supplied many Canadian DiyAudio members in the past and is familiar with the requirements of the amp designs. My dealings with him regarding my issue are even documented in a thread a few years ago.
Worth a shot, hope this helps.
Joe
I've been reading through this thread and finally just zoomed in on your first pic and see that you are using a transformer from SumR. Coincidentally my first amp build (Aleph J) also used a toroid from them and had the exact same problem with buzzing. Not only through the speakers but from the toroid itself. Is this a similar issue? I would reach out to them and speak to Richard the owner as I did and see if there is something he may be able to help you with. He was a very helpful, kind man who stands behind his products and even sent out a new transformer to me after some trouble shooting with me over the phone. Let him know that your amp is a Class A, FirstWatt/Pass Labs design. He has supplied many Canadian DiyAudio members in the past and is familiar with the requirements of the amp designs. My dealings with him regarding my issue are even documented in a thread a few years ago.
Worth a shot, hope this helps.
Joe
Thank you Joe.
This is good info I did notice it buzz against the tin cover when I had it out on the table as far as possible away from amp. But didn't click with me at the time. I personally think its the transformer I wanted to be sure I illuminated all possible areas that could cause this. I will be contacting him this week. Thanks again.
Peter.
Glad to help! Hopefully you get this resolved and can get back to listening to a great amp.
If there is still hum with transformer far away from amp boards I don't think it is the transformer that causes hum ("electrical hum"). But a loose winding that causes mechanical hum is not nice to listen to. Power transformers that is loaded will have a bit of noise if ear is close to it and sound can be amplified by chassis. The magnetic fields in trafo generates mechanical forces inside trafo.
Electrica: Mechanical Forces Acting on Transformer
So the question is how much is noise from the mechanical vibrations in trafo?
The real issue is the hum in speakers?
Electrica: Mechanical Forces Acting on Transformer
So the question is how much is noise from the mechanical vibrations in trafo?
The real issue is the hum in speakers?
If you are like most here, it won't hurt to try a different transformer. If that one turns out OK, you have a transformer for your next build.
If defective, SUMR will take care of any problem. I have one of their 24 + 24 1000 VA in my BA3 amp, and it dead quiet. Anyone can get occasional bad item.
Russellc
If defective, SUMR will take care of any problem. I have one of their 24 + 24 1000 VA in my BA3 amp, and it dead quiet. Anyone can get occasional bad item.
Russellc
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