There is no need, as far as I can tell, to "hide" the transformer behind the heatsink. I've built quite a few MyRef's with the transformer as close to the power supply edge as an inch, and there is no hum produced. In fact, the amp will probably perform better with short leads to the board and the heatsink over the air vent.
Peace,
Tom E
Peace,
Tom E
A couple ideas.
I have not used a My_Ref built this way in a while. The latest boards are designed for lower noise. The designer upgraded the design to an Evolution model around 2006.
One trick I used on this vintage design was to solder some 22 ufd 50v caps right to the power pins of the LM3886. Used FC or other low impedance caps.
With layout the leads can be as short as 0.5 cm.
Also added a 47 nfd stacked film cap with a sub 1 ohm resistor across each the main filter caps.
This each life and jump to the amplifier. The small value caps on the chip bring the biggest improvement.
The original designer was not a fan of fancy parts. He believed design, operating points, layout, and measurements were more important than expensive parts.
He changed his mind on power supply. Replaced the zener based low voltage reg to a proper current sourced supply and the single standard bridge rectifier with better quality rectifiers. Guess he could hear and measure the improvement.
Also installed a limiter and servo to control offset voltage.
But your amp can be improved as it is. There is a new Group Buy. The measured performance is much improved over the 1.05.
I just finished the new one. Dead silent on my 106 dB efficient horns. And blasting dynamics. Too good. Helped identify an issue with the power supply used on my dac.
I have not used a My_Ref built this way in a while. The latest boards are designed for lower noise. The designer upgraded the design to an Evolution model around 2006.
One trick I used on this vintage design was to solder some 22 ufd 50v caps right to the power pins of the LM3886. Used FC or other low impedance caps.
With layout the leads can be as short as 0.5 cm.
Also added a 47 nfd stacked film cap with a sub 1 ohm resistor across each the main filter caps.
This each life and jump to the amplifier. The small value caps on the chip bring the biggest improvement.
The original designer was not a fan of fancy parts. He believed design, operating points, layout, and measurements were more important than expensive parts.
He changed his mind on power supply. Replaced the zener based low voltage reg to a proper current sourced supply and the single standard bridge rectifier with better quality rectifiers. Guess he could hear and measure the improvement.
Also installed a limiter and servo to control offset voltage.
But your amp can be improved as it is. There is a new Group Buy. The measured performance is much improved over the 1.05.
I just finished the new one. Dead silent on my 106 dB efficient horns. And blasting dynamics. Too good. Helped identify an issue with the power supply used on my dac.
I'm sorry to hear that you feel that way. I wonder what happened? So many people have had success with this design.
The My_Ref FE's that I have built are certainly not dull and lifeless. In fact, I built an Impasse pre (voltage stage) + Pass F4, just to see what everyone was talking about. The Impasse/F4 is a nice amp, but my 2012 My_Ref FE is easily its equal.
A side note, I found it interesting that we spend money on signal path components in the My_Ref, but not so much on heatsinks and transformers. With the tube amps I have built, the money is about the same, but the money goes to transformers, tubes, and sometimes input jFETs. With the Class A, the jFETs are still there and also transformers, but more money goes to heat sinks.
Anyway, I'm sorry you had a bad experience.
One other thought. What speaker load are you driving? The output stage is a current pump. It has high impedance for a solid state amp.
Also it requires some hefty source. I used much larger input coupling caps. Like 1 ufd. I used several tube preamps and found large output coupling caps on the preamp helped bass extension.
With a 100K input impedance the 0.22 ufd coupling cap should be fine. I liked 1 ufd better.
Also it requires some hefty source. I used much larger input coupling caps. Like 1 ufd. I used several tube preamps and found large output coupling caps on the preamp helped bass extension.
With a 100K input impedance the 0.22 ufd coupling cap should be fine. I liked 1 ufd better.
I have 8ohm 3way, I know it would be nice to buy the latest PBC only to find there is a new and better Vers around the corner, but its sound is very unremarkable, I can put any Gainclone type amps and (I know its not the same design), but they sound more lively and have midrange clarity with punch. Is it just my taste I am 55yrs old and like music to sound real not compacted or compressed maybe high expectations, anyway just my experience, I never bought into the buy exotic parts, but with the help of people on this forum I did get to the stage where I was trying a few different resistors and caps which helped a lot but not enough, spent too much time on this, and when I add up the cost it doesn't add up to good value, just my opinion, but it was none the less it was enjoyable in the beginning. In the spirit of DIY don't be swayed by my opinions for anyone who is interested in this amp, I have high respect for the vast knowledge of the people who provide us the opportunity to get the most out of audio.
Hi Peter,
I thought you were happy after swapping the Caddocks...
According my archive your boards should be rev. 1.20 from 6th GB (March 2015).
Newer boards (from 1.5 upwards) sounds more neutral and natural but older versions never sounded lifeless and dull....
Can you post a picture of your build so to have a precise idea of the parts mix you're using now?
Did you try the amp with other speakers? I remember that yours, maybe, had something peculiar.
Because the amp should not need to be pumped at near max volume to get a decent output volume, there is a problem.
One possible answer could be a too low sensitivity, or a wrong preamp/volume pot choice.
Any info on your setup could help tracing the problem,
Could you give a link to speakers specs?
I'm happy you want to try newer boards but I would also like to first fix any problem that you could have also with newer boards.
You're welcome.
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Please don't think we never listened to other gainclones before my_ref FE. If we are trying to uphold My_ref FE is because it goes much further than other gainclones - and this is confirmed by many other hifi aficionados i know that listened to this amp after proper modding.
Surely gainclones tend to have very clear and live mids. But i'd say "thin", in most cases. Not to talk about "boxy" soundstage, weak tridimensional imaging, general cold and uninvolving sound. All these shortcoming do not belong to My_ref FE, rather it's surprisingly strong in those areas.
You say compacted and compressed? I don't agree, but maybe i understand your expectations are not higher, they're simply different: you are looking for a gainclone, instead you found an amp that is more on a good tube/discrete amp sound level. Standard My_ref FE can sound like music output is a bit "lazy", somewhat hard to get out, a bit shy compared to some class D or mosfet amps for example - that's the result of its harmonious character. But that's something you can easily overcome using the following mods.
The "exotic parts" way is a bit expensive (but not so much, to be honest), but results are stunning; the problem is you have to carry it on to a reasonable end to reach satisfaction above other amps of higher cost. You bought expensive exotic components and you're half way in this road, so now don't waste all you have done at a few steps away from the goal.
Start using current version of the boards, i use 1.5 boards with great satisfaction but i know 1.2 v. was clearly worse. If you really want to blow away any "compressed" or "chained" residue in its sound and make it a super sounding amp, then you can try the following:
1) Use all Dario suggested audiophile upgrades (here: Fremen Edition - Google Drive), including Mundorf AG, Z-foils where required, Mundorf Supremes (or, even better, Audyn True Coppers) coupling caps, AMCH (no C30 - see point 3). No Cerafines, see point 5
2) More, put Z-foils in R5, R6, R8 and R9 too
3) Put 1nF (or 2 x 500pF) Sovcor CY15 glass caps in C30
4) Use Hexfred diodes instead of MUR820 - or Cree SIC if you would trade a little more warmth for a little more neutrality (we're talking about tiny differences, though).
5) Follow Joseph K directions in posts 3085, 3086 and 3096 about replacing LM318 with OPA827, including eliminating C9. Use proper care, but you shouldn't face great problems - i didn't...
6) Put this resistors in R3 using heatsink and bluetak or some other dampening material to make them firm onboard: Isabellenhutte Precision metal film resistor, 0.33 Ω (R33), 3 W, TK +-50 PBH-R330-F1-1.0 | Burklin Elektronik
7) Be sure to use 2 transformers of adequate power, more than 180VA each are mandatory for toroids, more than 130VA each for R-cores
8) Avoid pots or attenuators if you can - just plain power amp
9) Use a good preamp (no cheapos, preferably tube based or hybrid).
N.B.: for real max SQ, none of the abovementioned mods should be ignored, not even one, as they're mutually connected. Points 8 and 9 can be skipped if strictly needed, but only if point 5 is completed and using a very good quality attenuator, like DACTs, Khozmos or Valabs at least). First 5 points are the most imperative. Cost should not be too high, given you say you completed point 1 already, isn't it? Maybe you have completed some other points, too...
By doing the abovementioned, you'll reach dynamics, transparency, imaging, separation, contrast, timbre that are way above standard my_ref and make it comparable to commercial amps of much higher cost (without being "thin" as most gainclones are).
My My_ref FE, after these mods, is clearly superior to my S-AKSA amp and comparable to my 6C33C OTL monoblocks, even better in some parameters. Just try to believe.
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