2x160VA is the MINIMUM for toroidals, 2x200VA is the best cost/performance compromise.
Still 2x300VA, according bcmbob during beta testing, gives a nice improvement over 200VA.
1x300VA will work and sound good but for the best performance I would go with 2 transformers.
Can you explain how this can be? The LM3886 can only deliver 68W at 4-ohm and even then is probably current limited slightly less before SPIKE will kick in. So the math seems off, or I am missing something - most likely the latter, which is why I ask?
Math is fine but in my experience with toroidals happens.
The only difference is that when you measure secondaries disconnected from circuit you have a voltage higher than rating (like 26.5V for 25V rating), after you attach those secondaries to the circuit you will measure a voltage a bit lower than rating (like 24V).
This difference with/without load lowers with higher VA rating.
This could also be a factor.
In my construction, based on the industrial BOM, for ease I always chose the cheaper toroidal transformers in the Mouser catalog that met the minimum requirement of 160VA. These are the Triad Magnetics of which I enclose datasheets. Cost 40 euros plus tax and shipping. I must say that they work well, without noise or overheating. But I'm always the one looking for the most massive and full-bodied sound. So I find the listening experiences of those who have implemented transformers of 200VA or more very interesting.
In a lazy way, always on Mouser, I found this other 250VA Triad which costs 54 euros.
I ask if you have any more convenient models and suppliers for toroidal transformers from 200-300VA.
I also ask if anyone wants to argue technically, possibly also in relation to costs, about the advantages and disadvantages of the different types of transformer (toroidal, laminated, C core...) for this application, for the My_Ref.
As always thanks to all
Ciao
Giacinto
In a lazy way, always on Mouser, I found this other 250VA Triad which costs 54 euros.
I ask if you have any more convenient models and suppliers for toroidal transformers from 200-300VA.
I also ask if anyone wants to argue technically, possibly also in relation to costs, about the advantages and disadvantages of the different types of transformer (toroidal, laminated, C core...) for this application, for the My_Ref.
As always thanks to all
Ciao
Giacinto
As mentioned, bcmbob did subjective comparisons of transformer with different VA ratings. I looked for his posts, but couldn't find them. So, if memory serves, he compared 2x180VA and 2x330VA. He found the bass to be better with the higher VA transformers, fuller bass and better slam. This was a similar difference between the industrial BOM power supply reservoir caps and the Mundorf reservoir caps (lower ESR). If someone is better at searching old posts than I am wants to look for bcmbob's posts, I believe they were in the Beta/Fine Tuning thread, or possibly the Fremen Edition RC - Build thread.
With regard to Triad transformers, I have used these several times. They are good quality and perform well. Depending on the project, I have had hum issues when the Triad was in the same enclosure as the signal electronics. This isn't a criticism of Traid, just the reality of an EI transformer compared to torroids.
@ giacintopapa and Joseph K,
I hope you guys will share the results of your comparitive listening. I would really love to hear your impressions.
Jac
With regard to Triad transformers, I have used these several times. They are good quality and perform well. Depending on the project, I have had hum issues when the Triad was in the same enclosure as the signal electronics. This isn't a criticism of Traid, just the reality of an EI transformer compared to torroids.
@ giacintopapa and Joseph K,
I hope you guys will share the results of your comparitive listening. I would really love to hear your impressions.
Jac
Thank you Jac, I also remembered this post, but not the author and not your details. The only other indications that I remember are those of Dario reported a few posts above and his use of R-cores. And finally George who does not describe the effects of a 500VA transformer: he invites comparison with wise awareness ...
Ciao
Giacinto
Ciao
Giacinto
I would like to add, that I have heard with many configurations, these amps. I do like even the original, Talema 300VA transformers, suggested by Mauro.
I do love, absolutely, the sound of the FE modules of Luca72 - he did all the recent usual mods with opamp etc. + plus even more. He uses the R-cores suggested by Dario. More friends had gone with the R-cores, in our circles. Others, like me are fiddling with toroidals, Toroidy. I have the standard audio version, my friend had taken their top audio model. It is very good, indeed.
In the past, I had played with the dual mono, small core, like 160VA versions, too.
I would vote against that, today.
We could go into reasoning, if there is interest.
By the way, it's not 68W on 4ohm, it's more like 100W at clipping.. (98W) With my dual-pump per side Evolution. And my 4ohm Revelator monitors.
That is on the load. Count the Class AB efficiency, dual channel, transformer & rectifier losses.
Even with classical reasoning 300VA is too small for a stereo amp.
But count also conduction angle, and core saturation..
The current peaks are much higher than the RMS of the average musical output.
And we are talking about music, not sinusoidal currents with predictable constant power..
Ciao, George
I do love, absolutely, the sound of the FE modules of Luca72 - he did all the recent usual mods with opamp etc. + plus even more. He uses the R-cores suggested by Dario. More friends had gone with the R-cores, in our circles. Others, like me are fiddling with toroidals, Toroidy. I have the standard audio version, my friend had taken their top audio model. It is very good, indeed.
In the past, I had played with the dual mono, small core, like 160VA versions, too.
I would vote against that, today.
We could go into reasoning, if there is interest.
By the way, it's not 68W on 4ohm, it's more like 100W at clipping.. (98W) With my dual-pump per side Evolution. And my 4ohm Revelator monitors.
That is on the load. Count the Class AB efficiency, dual channel, transformer & rectifier losses.
Even with classical reasoning 300VA is too small for a stereo amp.
But count also conduction angle, and core saturation..
The current peaks are much higher than the RMS of the average musical output.
And we are talking about music, not sinusoidal currents with predictable constant power..
Ciao, George
Hi George
Very interesting information
Can i Ask you whats’ is your loudspeaker?
Antonino
Hi Dario,
I am just about ready to start to build the My Fef FE. My version of pcb is Version 1.05
I assume that I would be safe to use the BOM up to Version1.2?.
Can I modify this V1.05 pcb to make it a My Ref EVO or one of the newer versions.
It has been a long while since I purchased these and there has been lots of new pcb's, revisions, and BOM's, so I thought I would ask the experts. Thanks for the help.
Myles
I am just about ready to start to build the My Fef FE. My version of pcb is Version 1.05
I assume that I would be safe to use the BOM up to Version1.2?.
Can I modify this V1.05 pcb to make it a My Ref EVO or one of the newer versions.
It has been a long while since I purchased these and there has been lots of new pcb's, revisions, and BOM's, so I thought I would ask the experts. Thanks for the help.
Myles
Hi Myles
yes, it's safe and the recommended one to use.
No modification on the PCB is needed simple use parts or avoid mounting some as directed in the build guide and BOM