I was experiencing this also. I initially used .25 amps, then .5A . Even with nothing connected to the single 200VA toroidal, I was still blowing fuse. I'm now using 2A fuses. I can't find any slow blow fuses.
Oleg, Inrush current could be the problem, what do you use? Is 2A enough for the MyRef, or should I go up?
Ah, thanks. Maybe that's the problem. Somebody said it shouldn't be a problem. But even with 1.6 it still blew. Will go to the shop today and buy a few fuses. Hopefully they have slow blow
Thanks, then I will buy those again and some stuff to cover the tabs from the transformer.
Hopefully nothing has been damaged.
Fast blow fuse will need to be overrated too much for successful start up which makes it less safe later on.
It's enough for 2 boards (total of 4*10,000uf) plus one JC-2 clone
Attachments
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New fuses, gone headache. Measured DC ofsett directly from the board, almost none: one channel 0.001 volt, the other 0.006.
Hopefully a first listening session in the evening!
One question: the label on the board at the input tab say HOT and in. IN meaning the audio signal and hot ground?
Edit: hot is signal, had a photo of the back of the board...
Hopefully a first listening session in the evening!
One question: the label on the board at the input tab say HOT and in. IN meaning the audio signal and hot ground?
Edit: hot is signal, had a photo of the back of the board...
Last edited:
Hi rough512,
I like what you did with the heatsinks. The spring clip is an interesting idea too. If you have it running, do you see a temperature difference between the fin that the LM3886 is attached to and the other fins? If so, does it seem like a big or small difference?
I know that MyRefs generally don't need a very big heatsink, so maybe it doesn't matter. I was curious for a different project that does reject some heat.
Jac
I thought I had a very good amp. And I did, it was way better than the one before that (rotel RA07)
But this one. Another league. Better control of the bass and more detail.
My wife and I were listening to Arcason the other night(from Candido - the Master). Control of the bass and detail in the bass is better than my tube amp. Somebody said he liked the 'thereness' of the musicians, I completely agree! Razor sharp imaging, not too big, just right. As if they are in the room. Not warm, surely not analytical. You feel the enthousiasm of the musicians, at a certain point someone on the left is really enjoying the moment, and starts laughing/humming. You just 'see' him playing, laughing, enjoying. We both smiled. Listened to that song a few times, that never happened...
And that's most important, at least for me. Not the lowest THD+N or some other statistic/measurement. So a big thanks to Dario for this great sounding amp! I love that I can have a sound quality at home I can't afford if I should have to buy it from the store! You and all the FremenEdition pioneers made that possible.
About measurements: couldn't believe my eyes: DC offset is 4mv on the left channel and 6 on the right. Seems like real good values.
My transformers are buzzing quite a bit, is that normal? I also experience a buzz from the speakers, any tips besides turning the transformers? My speakers are 95db, so a little buzz will stay, I think.
But this one. Another league. Better control of the bass and more detail.
My wife and I were listening to Arcason the other night(from Candido - the Master). Control of the bass and detail in the bass is better than my tube amp. Somebody said he liked the 'thereness' of the musicians, I completely agree! Razor sharp imaging, not too big, just right. As if they are in the room. Not warm, surely not analytical. You feel the enthousiasm of the musicians, at a certain point someone on the left is really enjoying the moment, and starts laughing/humming. You just 'see' him playing, laughing, enjoying. We both smiled. Listened to that song a few times, that never happened...
And that's most important, at least for me. Not the lowest THD+N or some other statistic/measurement. So a big thanks to Dario for this great sounding amp! I love that I can have a sound quality at home I can't afford if I should have to buy it from the store! You and all the FremenEdition pioneers made that possible.
About measurements: couldn't believe my eyes: DC offset is 4mv on the left channel and 6 on the right. Seems like real good values.
My transformers are buzzing quite a bit, is that normal? I also experience a buzz from the speakers, any tips besides turning the transformers? My speakers are 95db, so a little buzz will stay, I think.
I'm happy you're enjoying the amp 🙂
Yes, those are good values.
Toroidal transformers, if not defective, usually buzz if there's DC on mains, eventually try to measure it.
If it's so there are circuits that can fix the problem.
First of all try rotating transformers until you reach the minimum amount of noise, after that with such sensitive speakers heatsinks' grounding is critical, try ground them to safety ground point you have on chassis.
Finally, only if nothing of this will work try connect PGND on boards to safety ground (there will be a small performance cost), better via a ground breaker circuit.
It that
DC Blcoker
I highly recommend the DC blocker of Aleksandar. Only PCB or populated.
ATL Hi-Fi Audio Company | Just another HiFi Company with stunning products!
al_tsankov | eBay
I highly recommend the DC blocker of Aleksandar. Only PCB or populated.
ATL Hi-Fi Audio Company | Just another HiFi Company with stunning products!
al_tsankov | eBay
Thanks for all the tips, will try them somewhere the next few weeks.
The DC offset board looks good. Definitely going to try that one!
The DC offset board looks good. Definitely going to try that one!
toroidal transformers with one output
I need your help. Do you know if there is any negative impact in the following scenario.
By accident i bought 2 toroidal transformers with a mono instead of a double output ( 2x24v). The trafos are 200 VA each.
I plan to split the output to create the 2x24v input that the board needs.
Will there be any negative effects from that configuration?
I need your help. Do you know if there is any negative impact in the following scenario.
By accident i bought 2 toroidal transformers with a mono instead of a double output ( 2x24v). The trafos are 200 VA each.
I plan to split the output to create the 2x24v input that the board needs.
Will there be any negative effects from that configuration?
...too clumsy and unlucky in this period...
I fried another board...The very last version, just finished!
I accidentally shorted the loudspeaker terminals with a screwdriver, and the left channel has gone with a beautiful spark...
...and now my amp is on the desk again...
I checked the voltages written on the board. I had to change T201 and now they are ok but the led doesn't turn on...
Any suggestion?
Thank You very much for your help...
I fried another board...The very last version, just finished!
I accidentally shorted the loudspeaker terminals with a screwdriver, and the left channel has gone with a beautiful spark...
...and now my amp is on the desk again...
I checked the voltages written on the board. I had to change T201 and now they are ok but the led doesn't turn on...
Any suggestion?
Thank You very much for your help...
Pekodot: I think You can do it, no problems. I had used a similar config for a period. You have two secondaries, like if it were from one transformer.
Soulfuel: The usual culprit is R11, the 1ohm ground-separator resistance. It likes to die, sometimes with an output short. (it opens)
But You could be a bit more unlucky and that means both active parts, unfortunately.
Ciao, George
Soulfuel: The usual culprit is R11, the 1ohm ground-separator resistance. It likes to die, sometimes with an output short. (it opens)
But You could be a bit more unlucky and that means both active parts, unfortunately.
Ciao, George
Just for clarity, run one secondary in parallel to AC1 of both boards and the other secondary in parallel to AC2 of both boards. Do I have that right?
Jac