Hi Massimo, all the documents are liked to in the first post of this thread.
Best,
Dan
FE Rev A uses the same schematic, it just uses different values for certain components and leaves other out. Just study the BOM. and look for the EVO A component differences.
I don't know of anyone using a higher corner frequency for the C9 - R10 filter, but it shouldn't be a problem. The main point of the filter is to reduce the gain of the op-amp at DC. A higher corner frequency will still be low gain at DC.
As for bipolar caps, some have been tried, but didn't sound better than other choices. To my knowledge, no one has tried that specific cap. The best advice is to build the amp by the BOM because those components have had lots of work by Dario (and to a lesser extent, others) to optimize the package. Then, after you know what it sounds like with the BOM, experiment.
Enjoy,
Jac
Hi Dario, first of all I hope everything is fine for you and your loved ones. I have a feeling of great closeness and solidarity.
I saw big news in the presentation of the 14th GB!
"I would like to:
-change C13 pads and dimensions
-support TO247 resistors for R3
-support feedback capacitor for fet-opamps compensation (if possible)"
I am a happy user of My_Ref FE with My-Evo Rev.A compensation. During this forced cloister I am also listening to the fet-opamp version that George had left me.
This version is very interesting, an excellent alternative with great potential. I understand Jac and would like to have both versions!
I was skeptical of "betraying" LM318 and its compensation not only for the excellent musicality of this chip, but also for reasons of philological respect for the original choices of Mauro Penasa. But it was a limited view, I think.
For this reason I wanted to express my esteem to you. You have shown intellectual honesty and open-mindedness. Making this possibility available on FE boards is an opening to diversity, to experimenting with new paths.
Thank you!
Ciao
Giacinto
I saw big news in the presentation of the 14th GB!
"I would like to:
-change C13 pads and dimensions
-support TO247 resistors for R3
-support feedback capacitor for fet-opamps compensation (if possible)"
I am a happy user of My_Ref FE with My-Evo Rev.A compensation. During this forced cloister I am also listening to the fet-opamp version that George had left me.
This version is very interesting, an excellent alternative with great potential. I understand Jac and would like to have both versions!
I was skeptical of "betraying" LM318 and its compensation not only for the excellent musicality of this chip, but also for reasons of philological respect for the original choices of Mauro Penasa. But it was a limited view, I think.
For this reason I wanted to express my esteem to you. You have shown intellectual honesty and open-mindedness. Making this possibility available on FE boards is an opening to diversity, to experimenting with new paths.
Thank you!
Ciao
Giacinto
About R3:
An Isabellenhuette resistor is mounted on George's FE fet-opamp instead of the Caddock. Dario is experiencing a Mundorf in this position.
George confirms to me that vibrations and resonances are a problem with this resistance. He found improvements using thermal paste and heat sink which apparently work as dampers. Mundorf seems to solve this aspect with different materials (copper plate).
Even if Munford has better damping, I was wondering if it makes sense to think about using a silicon thermal pad (instead of just paste) together with a small copper plate (instead of more resonant steel or aluminum) to improve dissipation and absorption of vibrations. Maybe doubling on both sides of the resistance.
Ciao
G
An Isabellenhuette resistor is mounted on George's FE fet-opamp instead of the Caddock. Dario is experiencing a Mundorf in this position.
George confirms to me that vibrations and resonances are a problem with this resistance. He found improvements using thermal paste and heat sink which apparently work as dampers. Mundorf seems to solve this aspect with different materials (copper plate).
Even if Munford has better damping, I was wondering if it makes sense to think about using a silicon thermal pad (instead of just paste) together with a small copper plate (instead of more resonant steel or aluminum) to improve dissipation and absorption of vibrations. Maybe doubling on both sides of the resistance.
Ciao
G
If using heatsink pads to damp potential ring the rubber may be of help. I looked for the ones George recommended, did not seem aavailable in the US. Requested samples from distributor but they saw through my request. Would not respond to a request from my work email.
One pad to avoid is the beryllium oxide pads. They will poison the high frequencies.
One pad to avoid is the beryllium oxide pads. They will poison the high frequencies.
I have looked for the Isabellenhutte, VPG Powertron, and the new Mundorf in the US and no luck. They all seem to be made by the same manufacturer, just different builds, brands, and price. The most audio version, the Mundorf that Dario is testing, and the Powertron are available at hificollective in the uk and there are a few German distributors that seem to stock the cheaper Isabellenhutte. The only silver lining is that the US dollar is strong amidst this economic mess, so its a little less expensive buying from Europe.
Jac
Thanks fir the heads up on Hi-Fi Collective. I looked to see what these sell for. It appears they do not stock the VPG Powertron in 0.33 ohm. And a greedy person has purchased all the Mundorf.
That might be 2 or 4.
I want to try the Isabellenhutte. Have not located yet.
These three resistor brands remind of a decision on RCA plugs last week. The brand I have used for along time is gone. They were 2.00 parts for 8.00 - 10.00 USD. But excellent.
The principles have a new brand and much revised product. Four levels of construction now. They are 10.00 - 45.00 USD each. Difference is the thickness of the silver plating.
Crazy game we play.
That might be 2 or 4.
I want to try the Isabellenhutte. Have not located yet.
These three resistor brands remind of a decision on RCA plugs last week. The brand I have used for along time is gone. They were 2.00 parts for 8.00 - 10.00 USD. But excellent.
The principles have a new brand and much revised product. Four levels of construction now. They are 10.00 - 45.00 USD each. Difference is the thickness of the silver plating.
Crazy game we play.
Hi Jac, after reading your approach with series/parallel i want also to give them a try and found some 2W Susumu from the same KRL series Pn KRL3264E-C-R330-F-T1
What do you think about using them instead of 1W that you used?
I can't say because the 2W, although listed, were not available when I was doing it. I will say that the 1W KRL on the small pcb with lots of copper that I used has no problem with temperature. Going to 2W versions would not be for thermal capacity, but because of the idea that higher power is better sounding.
The Vishay 3W is interesting, but I'm not clear on its construction. Its hard to tell if its a foil that is made of different material or deposited film. It could even be a different material for a thick film. Generally speaking, I don't care for the sound of thick film resistors, but the typical ones are have a metal oxide resistive element. Basically, the only way to know is to try it. That said, George has tried the Manganin resistor with success and Manganin has a good reputation for sound, so I'm waiting to see how Dario likes the Mundorf.
Jac
It is a crazy game we play.
I do admit to buying a pair of Mundorfs. If they are gone, it looks like hificollective didn't stock many. I haven't tried to order them, but the Isabellenhutte PBH are shown as available at Reichelt and Burklin in Germany.
Here in Europe I found these two sellers for R3, around 17 euros each + shipping.
MUNDORF MREU30, highest possible grade power resistor
Resistors
One question: what would happen using a value of 0.39 or 0.27 Ohm?
Thank you
ciao
g
MUNDORF MREU30, highest possible grade power resistor
Resistors
One question: what would happen using a value of 0.39 or 0.27 Ohm?
Thank you
ciao
g
Thank’s to the people writing from many years about Mauro Penasa my_ref amplfier i was encouraged to give new life to a old myref rev A,the original board of Mauro .
I did it just for play with a new toys ,discovering that my_ref isnt a toy amplifier
I have applied the evo A mods,add two big 25 volt 6 ampere surplus talema transformer,and and few better components in the crucial place
My original built of rev A many years ago was’nt so accurate..
It sound now very ,very good.
A lot of detail,armonious and fast
I think that the transformers help the amplifier to play very well at low mid frequency that are fast and articulate
It works with low frequency as 100 watt amplifier,very clean
I did it just for play with a new toys ,discovering that my_ref isnt a toy amplifier
I have applied the evo A mods,add two big 25 volt 6 ampere surplus talema transformer,and and few better components in the crucial place
My original built of rev A many years ago was’nt so accurate..
It sound now very ,very good.
A lot of detail,armonious and fast
I think that the transformers help the amplifier to play very well at low mid frequency that are fast and articulate
It works with low frequency as 100 watt amplifier,very clean
Attachments
Very nice, Tonix. That's an innovative approach to the heat sink. These things don't need huge heat sink, but using the side panel and adding an additional remote heat sink is a cool idea.
@thunderchicken,
TONIX amp shows nice principles in the layout, IMO. He as kept his pcbs close to the back panel so that the signal runs from the panel inputs are short and away from the transformers. The My_Ref (FE or not) has pretty good PSRR, so you can run the AC to the transformer close to the pcb, but the farther away, the better.
Alas, I manage to complicate most of my builds, so they aren't good examples to show.
Have fun.
