Mhm. Has bugged me ever since I got it. I don’t see the point of of having so short secondary wires. Difficult to work with.
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If I was to aim for a new transformer: would you go for 600 or 800va? I have room for the big one. Thinking Toroidy supreme audio grade. Supposed to be dead silent. Looks fancy too. Though a bit expensive. Should be a lifetime of transformer that thing.
Link to 600va here: TTSAS0600 - SUPREME AUDIO grade transformer TSAS600VA - voltage to 50V - Shop Toroidy.pl
760 zloty amounts to round about 180 dollars. The 800 a bit more expensive.
Link to 600va here: TTSAS0600 - SUPREME AUDIO grade transformer TSAS600VA - voltage to 50V - Shop Toroidy.pl
760 zloty amounts to round about 180 dollars. The 800 a bit more expensive.
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Thanks, as usual. Have to thank you for making me realize the BA-3 was the way to go. What a learning experience, and what sound. Guess the manual stating 600-800va, as well as the guide, is what made me look for a bigger one. But I know, the amp will not consume enough to overload the transformer. The money saved can be put in a Toroidy DC blocker. Should be a perfect match.
Have I missed something, or should the 3 deep PSU recommendation be the standard Pass 300-400va? After all, it is basically the F4 output stage. So the answer is allready there... No gains from bigger one, I kinda like it.
Have I missed something, or should the 3 deep PSU recommendation be the standard Pass 300-400va? After all, it is basically the F4 output stage. So the answer is allready there... No gains from bigger one, I kinda like it.
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Cause 6L6 talked me out of dual mono. For which I am glad, since it is my first project. But the future is bright =D
I have a little more to go on wrt temp. Might aim for 200 watts total dissipation. Means a 400 will do, but 500 gives some more headroom.
Btw I talked with my amp. It resents being called sissy! It says it is the only real burning amp it knows.
I have a little more to go on wrt temp. Might aim for 200 watts total dissipation. Means a 400 will do, but 500 gives some more headroom.
Btw I talked with my amp. It resents being called sissy! It says it is the only real burning amp it knows.
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Hello Andy,
I have bought a number of transformers from Toroidy. I usually choose the Audio Grade, not the Supreme. Only once have I used a pair of Supremes, and that has been with the output transformers of my EL84 tube amp, and there it was more for looks
The Audio Grades are perfectly fine and all have been quiet in my builds. With my ear directly on the amp chassis, I can barely hear it under full load. Have got my F4, Aleph J, SissySIT absolutely quiet through the speakers with 100 dB/W widebanders.
This has more to do with proper PSU CRC or CLC specs and proper wiring / dressing (mimimizing loop area) than with an extremely shielded transformer. (It can be different with something like an M2, which has an audio input transformer that could pick up magnetic fields).
With your stereo PSU, I would recommend an Audio Grade 500 VA transformer - this is built on the next bigger core from the 400 VA. The 600 VA brings no advantages, because it is built on the same core as the 500 VA, so leads to a higher magnetic excitation of the iron core, and potentially more stray field.
You could choose 500 VA with 2 x 20V or 2 x 22V.
When ordering, you could ask Toroidy for longer secondary wires as well, so that it would be easier to rotate the transformer once in the chassis.
I always mount my transformers with a neoprene disk below and above the transformer so that I don't have mechanical vibration transfer to the chassis; this helps in quieting as well.
Great that you like the BA-3 so much !
All the best,
Claas
I have bought a number of transformers from Toroidy. I usually choose the Audio Grade, not the Supreme. Only once have I used a pair of Supremes, and that has been with the output transformers of my EL84 tube amp, and there it was more for looks
The Audio Grades are perfectly fine and all have been quiet in my builds. With my ear directly on the amp chassis, I can barely hear it under full load. Have got my F4, Aleph J, SissySIT absolutely quiet through the speakers with 100 dB/W widebanders.
This has more to do with proper PSU CRC or CLC specs and proper wiring / dressing (mimimizing loop area) than with an extremely shielded transformer. (It can be different with something like an M2, which has an audio input transformer that could pick up magnetic fields).
With your stereo PSU, I would recommend an Audio Grade 500 VA transformer - this is built on the next bigger core from the 400 VA. The 600 VA brings no advantages, because it is built on the same core as the 500 VA, so leads to a higher magnetic excitation of the iron core, and potentially more stray field.
You could choose 500 VA with 2 x 20V or 2 x 22V.
When ordering, you could ask Toroidy for longer secondary wires as well, so that it would be easier to rotate the transformer once in the chassis.
I always mount my transformers with a neoprene disk below and above the transformer so that I don't have mechanical vibration transfer to the chassis; this helps in quieting as well.
Great that you like the BA-3 so much !
All the best,
Claas
Clamp the secondary wires to terminal block, add extra wires to secondary on other side of terminal block. Once in "correct" position, bolt down terminal block and dress secondary wires.
I don't think it's rotating the transformer, that is the problem. I took no special pains with assembly, laid out exactly as did 6l6 in his build guide, to the letter.
My transformer is gigantic, 1000 VA 24 volt x 2. This is the quietest amp I have ever been around. Dead silent. Unless your transformer is defective, rare but I've had two recently. Keep looking, you will find it.
Maybe it is DC, but that likely would have been a problem before now? Maybe not...
Maybe transformer is radiating more hum inducing trash than should be the case?
I guess my point is that I haven't found any of my BA3 stuff (2 FE units one power amp) to be susceptible to hum. It should be very quiet, don't give up! The FE units I built both have 50 VA Antek, the power amp SUMr for transformer.
Russellc
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Will respond to all your brilliant advice a little later. But I came to think of the fact I take power both from the euroblocks AND from the PCB edge plus and negatives. Maybe that is one of the issues? Small differences in potential and resistance might contribute, right? Dis this because there are 4 wires and only 3 spots in eqch Euroblock. Btw, do you connect your speaker nega to the FE or the PSU PCB? What is best and why?
Worth doing some wiring tests before bying new equipment =S Dont wanna waste money if I dont have to.
Worth doing some wiring tests before bying new equipment =S Dont wanna waste money if I dont have to.
to Andynor
In my BA-3-builds I connected all groundwires (frontenmd, outputstage, speaker ground,....) to the mid of the PSU (ground). I tried, that the groundwires meet at one point (star ground point).
But there are different ways, how you can do it.
and: BA-3 is a sound-machine!
Greets
Dirk
In my BA-3-builds I connected all groundwires (frontenmd, outputstage, speaker ground,....) to the mid of the PSU (ground). I tried, that the groundwires meet at one point (star ground point).
But there are different ways, how you can do it.
and: BA-3 is a sound-machine!
Greets
Dirk
Ok. So now I have done a few more tests over the last hour and a half.
1: Corrected miswiring on negative secondary to rectifier: reduced hum, and equal levels on both speakers. It is now so low in volume, I have to put my ear right up against the speakers to her it.
2: electrically discoupled PSU from chassis using nylon standoffs. No change
3: Connected all ground wires to same euroblock. No change
4: it does NOT help to move the front end back and forth.
5: I disconnected the front end. And, SILENCE. Zen Mod: where to go from here? Or maybe settle with that, as good enough? Maybe, but I am a perfectionist.
What do you gather, people? I gather it is not a ground loop. Yet somehow this noisy transformer gets into my speakers, allthough very subtly. I am the kind of guy that wants to know WHY. But this you allready know.
I no longer think it is the sound of the tranny getting to the speakers. I also do not believe we are talking about a ground loop. Shorting the inputs, changing grounding scheme and using both grounded and ungrounded outlets, provided no change what so ever.
So in conclusion: only thing that worked, was disconnecting front end from PSU.
Are we talking magnetic coupling? And if so, with what can it couple with? I don’t get it. Or is it ripple?
Will a completely silent transformer with a DC filter fix this?
And maybe it dont need fixing. Plays like hell =) or maybe Heaven is the correct term in English.
Regards,
Andreas
1: Corrected miswiring on negative secondary to rectifier: reduced hum, and equal levels on both speakers. It is now so low in volume, I have to put my ear right up against the speakers to her it.
2: electrically discoupled PSU from chassis using nylon standoffs. No change
3: Connected all ground wires to same euroblock. No change
4: it does NOT help to move the front end back and forth.
5: I disconnected the front end. And, SILENCE. Zen Mod: where to go from here? Or maybe settle with that, as good enough? Maybe, but I am a perfectionist.
What do you gather, people? I gather it is not a ground loop. Yet somehow this noisy transformer gets into my speakers, allthough very subtly. I am the kind of guy that wants to know WHY. But this you allready know.
I no longer think it is the sound of the tranny getting to the speakers. I also do not believe we are talking about a ground loop. Shorting the inputs, changing grounding scheme and using both grounded and ungrounded outlets, provided no change what so ever.
So in conclusion: only thing that worked, was disconnecting front end from PSU.
Are we talking magnetic coupling? And if so, with what can it couple with? I don’t get it. Or is it ripple?
Will a completely silent transformer with a DC filter fix this?
And maybe it dont need fixing. Plays like hell =) or maybe Heaven is the correct term in English.
Regards,
Andreas
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Addition: electrically discoupled the FE from it’s rise panel. Got rid of some leaky DC apparently. Now one channel of FE is connected, the other not. I can actually hear the hum faintly from the speaker with only output stage connected. The orher channel, connected to FE, i can hear. There is no difference in ground potential between chassis and PSU ground. But maybe there is some leakage of ripple to ground somewhere? Just that it is amplified in the FE so I can hear it better. The only source of ground on one of the channels now, is speaker neg.
Also measured between star ground and NTC connection point. 0,0mv dc.
Also measured between star ground and NTC connection point. 0,0mv dc.
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I'm starting to think its the transformer. I recall another member in another build fought and fought hum, and in the end it was his transformer.
Me? I'd buy another transformer, I know that it WILL get used so not a waste of money at all. Plus it should (unless you are really unlucky) answer the question "is this my transformer causing this or not?" I say this as my recent replacement for a transformer that went south came defective out of the box....now that's bad luck!
Those toridy are awful nice....
Russellc
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Thanks, Russel. I too have deduced that from all the fruitless efforts of troubleshooting. I allready sent an e-mail to Toroidy. They don’t ship to Norway by standard. Should be a good Christmas present for myself =) Luckily, the hum is not audible from the listening position, so I am having a good time nonetheless!
If you have reduced it that much you are on the right track. I havent noticed this circuit being particularly vulnerable to hum.
My transformer is high quality I guess, its silent. I bought it in a group buy for Turbo F5...but decided to do go with BA3. Saw 6l6 used 24volts x 2, so I used it.
I'm about to remove cover for my once a month mosfet tightening check (need to add split washers) and will take interior pic. Nothing out of ordinary, basically looks like the one in 6l6's build guide.
Well, there would be a cat sleeping on it....
Russellc
My transformer is high quality I guess, its silent. I bought it in a group buy for Turbo F5...but decided to do go with BA3. Saw 6l6 used 24volts x 2, so I used it.
I'm about to remove cover for my once a month mosfet tightening check (need to add split washers) and will take interior pic. Nothing out of ordinary, basically looks like the one in 6l6's build guide.
Well, there would be a cat sleeping on it....
Russellc
Hi, Not sure if this should be here or in the BA3-b (balanced thread) but this thread seems to have more troubleshooting help/traffic...
I have built balanced monoblocks of BA3 using the complimentary output stages. I did bias and offset for each channel individually and let things cook etc. to get good levels.
Then I connected R5 on the FE to bridge them, and hooked the amp up to my crummy test speakers to do a quick test. I hear music but I am getting an LF motorboating putt putt putt noise. There's no loud hum or distortion to the music. When music is playing at a reasonable level I can't here the motorboating, but it's there clear as day when the input is shorted or when the music is at a very low volume. The speakers don't exhibit this behavior with other amps.
I swapped out my PSU for a bench top unit to rule out the DIY PSU, but the same motorboating occurs. It starts up when the PSU reaches around 18V and gets faster as it reaches full 32V output. This was also observable when I was using a variac with my DIY PSU. Once I got sufficiently close to ~100VAC on the variac and the PSU's output was around 18/20V the motorboating would start and increase in frequency as I brought it up to full mains.
The thing that I am confused about, is how to do "final" "global" offset. I've read through both this thread and the BA3-b thread front to back multiple times, and I've read through the wonderful Balanced BA3 notes that one of the users put together (Burning AMPS Notes - May 1 2020 pdf). These notes were very helpful, but I am still confused by this one last bit w/r/t offset in balanced config:
"Zen Mods Notes re: offset with balanced:
“same as with any bridged gadget , most important offset is between two hot outputs - that's
what your speaker will see and respond to ; as usual , clock it to 0mV , keeping on mind that
up to 100mV is tolerable , steady state
second offset you need to think of is DC level of both outputs (together) ref. to GND
up to 500mV is ok , more than that will cut of available voltage swing
say that's on +10V ; rails are +/-25V ; there is 15V space to upper rail , and 35V space to
lower rail ; guess which side voltage swing would first hit the ceiling
resulting in usable range of just 30Vpp , instead of 50Vpp (not counting losses)
I'm notoriously forgetting established names for these two offsets, one is Relative, other is
Absolute ...... and I believe I got them in this tutorial (but lazy to check, so it's easier again to
reveal my dumbness in Public) : Pass Labs X150.5 , checking/adjusting offsets ,Iq and gain |
Zen Mod Blog
regarding actual tricks on particular pcbs, can't help - I'm not familiar with them , so better
to ask someone who got them in hands
btw. - offset - taking in account that BBA3 OS - each group- is having independent DC offset
setting mechanism , you can do each group in simplest possible way - setting DC
Global DC offset will be bias balance between the two halves (Phases). It will make
more sense when you are doing it."
In my amp, when I measure VDC between speaker + and - I get 32V.
When I measure VDC between speaker + and GND I get 9VDC
When I measure VDC between speaker - and GND I get -23VDC
I'm thinking this is my problem, and these two values need to be equal to each other for "global offset" to be as close to zero as possible (or else you have one phase's peak voltage lower than the other etc.).
Is this accomplished by adjusting the P2 offset pots on the OS bias boards until both are 16V to split the difference (speaker + = 16V and speaker - = -16V)? What should these voltages be on Speaker outputs?
Or am I thinking about this all wrong? Is there some other place I should be chasing an LF oscillation?
FWIW I am running a 32v PSU (both my benchtop and my DIY) and i've made ALL the recommend pot changes in this thread to have larger ranges for biasing/offset adjustment. I'm also using 0.47ohm 3W source resistors on the output stage to get some more current. They're biased to 0.3VDC since that's about max safe current with my trafo etc.
I've done tons of board checking for roasted parts or bad caps but haven't found anything. Other than adjusting global offset on the outputs I'm not sure where else to go from here. I don't have an oscope but if I need to buy one I will (i've been wanting one anyway, and i'll just make it a self christmas gift ).
Thanks in advance for the help!
I have built balanced monoblocks of BA3 using the complimentary output stages. I did bias and offset for each channel individually and let things cook etc. to get good levels.
Then I connected R5 on the FE to bridge them, and hooked the amp up to my crummy test speakers to do a quick test. I hear music but I am getting an LF motorboating putt putt putt noise. There's no loud hum or distortion to the music. When music is playing at a reasonable level I can't here the motorboating, but it's there clear as day when the input is shorted or when the music is at a very low volume. The speakers don't exhibit this behavior with other amps.
I swapped out my PSU for a bench top unit to rule out the DIY PSU, but the same motorboating occurs. It starts up when the PSU reaches around 18V and gets faster as it reaches full 32V output. This was also observable when I was using a variac with my DIY PSU. Once I got sufficiently close to ~100VAC on the variac and the PSU's output was around 18/20V the motorboating would start and increase in frequency as I brought it up to full mains.
The thing that I am confused about, is how to do "final" "global" offset. I've read through both this thread and the BA3-b thread front to back multiple times, and I've read through the wonderful Balanced BA3 notes that one of the users put together (Burning AMPS Notes - May 1 2020 pdf). These notes were very helpful, but I am still confused by this one last bit w/r/t offset in balanced config:
"Zen Mods Notes re: offset with balanced:
“same as with any bridged gadget , most important offset is between two hot outputs - that's
what your speaker will see and respond to ; as usual , clock it to 0mV , keeping on mind that
up to 100mV is tolerable , steady state
second offset you need to think of is DC level of both outputs (together) ref. to GND
up to 500mV is ok , more than that will cut of available voltage swing
say that's on +10V ; rails are +/-25V ; there is 15V space to upper rail , and 35V space to
lower rail ; guess which side voltage swing would first hit the ceiling
resulting in usable range of just 30Vpp , instead of 50Vpp (not counting losses)
I'm notoriously forgetting established names for these two offsets, one is Relative, other is
Absolute ...... and I believe I got them in this tutorial (but lazy to check, so it's easier again to
reveal my dumbness in Public) : Pass Labs X150.5 , checking/adjusting offsets ,Iq and gain |
Zen Mod Blog
regarding actual tricks on particular pcbs, can't help - I'm not familiar with them , so better
to ask someone who got them in hands
btw. - offset - taking in account that BBA3 OS - each group- is having independent DC offset
setting mechanism , you can do each group in simplest possible way - setting DC
Global DC offset will be bias balance between the two halves (Phases). It will make
more sense when you are doing it."
In my amp, when I measure VDC between speaker + and - I get 32V.
When I measure VDC between speaker + and GND I get 9VDC
When I measure VDC between speaker - and GND I get -23VDC
I'm thinking this is my problem, and these two values need to be equal to each other for "global offset" to be as close to zero as possible (or else you have one phase's peak voltage lower than the other etc.).
Is this accomplished by adjusting the P2 offset pots on the OS bias boards until both are 16V to split the difference (speaker + = 16V and speaker - = -16V)? What should these voltages be on Speaker outputs?
Or am I thinking about this all wrong? Is there some other place I should be chasing an LF oscillation?
FWIW I am running a 32v PSU (both my benchtop and my DIY) and i've made ALL the recommend pot changes in this thread to have larger ranges for biasing/offset adjustment. I'm also using 0.47ohm 3W source resistors on the output stage to get some more current. They're biased to 0.3VDC since that's about max safe current with my trafo etc.
I've done tons of board checking for roasted parts or bad caps but haven't found anything. Other than adjusting global offset on the outputs I'm not sure where else to go from here. I don't have an oscope but if I need to buy one I will (i've been wanting one anyway, and i'll just make it a self christmas gift
). Thanks in advance for the help!