My_Ref Fremen Edition - Build thread and tutorial

[davym]

lol, the missis would not have this lot in the middle of the floor.

I tried changing inters and setting it all up in another room, no good.

I even tried a mains filter/surge protector socket block and plugged everything into it, no change.

Funny thing is the lead I used to test them with is not even screened, it's about 14" long with a cheap rca phono plug on one end and a jack plug connected for mono (right channel) on the other. I used it to test the amps one at a time. With the portable player plugged in I get loud hum until I switch the portable on, then silence when nothings playing.

What are the pro audio style isolation devices you mention Bob?

 

[bcmbob]

Hum Eliminator

ART Model has RCA - some info

There may be a DIY version somewhere here on the forum but I haven't looked yet.

 

[davym]

Looks interesting, I wonder what's inside it.

 

[bcmbob]

Check Data Sheet

 

[davym]

Ah, so it's using a transformer for isolation, one of those devices could be exactly what I need.

 

[bcmbob]

Again, search the boards/forums here. There may already be a project example. Andrew is the well traveled explorer at diyAudio - maybe he has seen one in the neighborhood.

 

[davym]

Will do.

 

[madisonears]

Do you have the covers on the enclosures when doing all this hum detection? One of my amps picks up low level hum from the power supply of the nearby subwoofer plate amp if not covered. Telephones can also cause noise if the amps are bare. Who knows what else? I can still hear my furnace motor clicking on, but it is reduced somewhat with the FE regulated supply, and that is line noise, not ground noise.

Peace,
Tom E

 

[rredline]

May be add a loop breaker circuit can fix the humming issue?
Earthing (Grounding) Your Hi-Fi

Just like what what someone did it in this pic...

 

[shoom]

I've been trying to reduce my FE's hum a bit further and have had no luck. Since I connected their power grounds to their chassis, I cant hear it from my chair anymore which is a big improvement. However if I put my head close to my speakers, I can still hear it. Is there anything which can be done to improve this or do I just have to put up with it?

If I short the signal in at the phono sockets to ground, they are almost silent. I just wish I could get them that quiet with something/anything actually plugged into them.

The layout is so simple I just cant see what else I can try, I tried soldering the signal in wires direct to the molex pin's and managed to get one twist in them before they reach the phono socket. That made no difference at all.

Any ideas folks?

EDIT - I almost forgot, there is one thing I can plug into them which does not increase the hum, my portable mp3 player. Anything else causes hum.

Hi Davy

any chance of a photo of the internals of your passive pre?

have you tried connecting just one channel at a time?

seems like a grounding issue to me as you report that connecting up your MP3 (without a ground connection ?) cures the problem.

IMHO it may be better to try to sort out the above before spending cash on extra's which you may not need.

it's going to be something simple so worth having another look at.

 

[nenne]

Lack of bass?

Wondering why you ask, Bob. Yes, I am now using the FE's as mid/high amps only with active xovers to separate bass. When I built my first pair of MyRef's, they drove a pair of B&W 802's full range, and sounded good doing it. But I realized early on that the strength of this little amp was in the upper range, not bass. Perhaps the FE with regulated supply is better? I have not yet heard them full range.

I am building a pair of FE's for my friend who has Eggleston Andra's. Look them up. We will try the FE's full range, but I don't expect outstanding bass performance, even with Mundorf M-Lytic power supply caps. Would like to be proved wrong, however. I suspect we'll end up with some sort of passive bi-amp setup with his Aragon 8008BB on the bottom.

By the way, I have spent a couple months now with a pair of FE's, one built with a Riken, one with a Shinkoh tantalum at R10. This amounts to personal preference for a very minor difference, but I hear sweeter, more musical sound from the Shinkoh's, and more detailed but very slightly sharp sound from the Riken. Is one providing greater accuracy and the other euphonic distortion? I don't care at all. I think this new design tends toward too much detail and requires just a bit of softening, almost too hi-fi SS compared to the tubey charm of the original MyRef. I really like the incredible resolution and layering of musical information, but at times it is close to brightness with a slight sharpness in the highs and upper midrange. Perhaps I will play with the compensation, try the old configuration to see if that brings back the original sweet sound while the FE layout still provides greater resolution.

Peace,
Tom E

I am not an owner of a FE even though I surely would like to and hopefully will. I have a My_Ref C thanks to Mauros efforts and all the work he made into making a wonderful design get to full bloom. I can agree on the impression of lack of bass BUT that changed to jawdropping when the rather new replacement basselements got exchanged for some up to date innovations. If the My_Ref so well performs in that range with the right bass in the box, then there might be nothing of an effort for the Freeman Edition to qualify in. I would suggest that a change in that area might blow your mind too.

Yes I listen to rockmusic, blues, fusion, but totally lacks interest for the discoed variant of stiff almost dead musical expression. Otherwise almost anything that finds it way through the holy smoke hidden in the parts.

Many thanks to Dario who have taken the My_Ref to a new and expanding level. All this hard and humble work for developed design seems to have payed off in a lot of happy and satisfied builders. So I have been reading this thread in envy. Still a lot precocious to fiddle with my working ones, it is standard components gathered on the boards, why risk? Surely I am no pro and My_Ref c was my first homebuilt ampli. Spending 900 sek on each 6,5 inch bass (twice as expencive from the original) was worth the satisfaction and everlasting experience of eargasms. There are surely greater levels to achieve If your demand is above this, then an upgrade to a more adaptive and cooperative element would end all questioning. Well, if you "Would like to be proved wrong, however". I thought I had to except a lack of bass and compensate for that blaming the construction. What comes out of this small boards and the speakers enclosure is not what expected. I am sure Mauro understood that too and so here I am totally blown away by releasing my mind from the selftorture and do what a man 's got to do.. It may look cheap but I am convinced that there is gain built in this. My_Ref released it's magic when it could. FE would do so too if you let it's potential loose.

All gratitude to Mauro for making an innovative design into a little miracle wonderful in music and to Dario to withhold the torch in the same manner. Thanks to all of You who blends this thread to a brighter light always a reading worth the time. The thunder you may hear is the music...

All the best Sven

 

[davym]

Hi Tom, yup covers are on. I am wondering if it has something to do with how close the transformers are to the front pannels though. Also the bolt together kit enclosures might be insulating some pannels so not forming a complete screen.

rredline, i cant get your attachment to open. Can you give me values for the components needed for the ground loop breaker?

shoom, i get the hum when it's just the DCB1 connected so i'm not sure it's the passive unit. The passive is a fully enclosed extrusion with just the front and back pannel removable so not easy to take pictures of the internals. It is now just two inputs, all rca grounds are bussed, the inputs are single wired to the toggle selector switch with a wire to the pot. The pot then feeds the output rca's from the wiper out. There is also a fixed line out branched off the pots feed. There are no resistors or other components used. It is about as simple as i can make it.

I'm going to mess about with it all some more today but i dont really know what else i can do with it. It could be because the sources (DAC & Phono stage) are double insulated and the rest is not. If so theres not much i can do about it. Even the CD player with i no longer use is double insulated

 

[bcmbob]

....Even the CD player with i no longer use is double insulated

Did you try a simple wire (jumper) to/between the cases - or cases to an active ground?

 

[davym]

I tried a wire between the cases of the DCB1 and the FE's. And between the passive pre and the DCB1. No good or it actually made things worse in the case of the later. I have not tried connecting the cases to an outdoors earth spike, I don't have out of them.

I just tried only connecting the DAC to the FE's, nothing else in circuit bar the speakers, still got the hum! tried moving the DAC away from the amps, no difference.

I might have to work on the DCB1 a bit more because it's the only thing which makes the hum worse. Even so I cant hear it from my chair, I have to put my head to the speakers to hear it. It may be that I just have to accept what I have, after all it sounds dam good when playing music.

Brit company REGA have issues with their new version of the Brio integrated amp. Folks say they can hear the hum it puts out through their speakers, when sitting in their chairs, at least I don't have that issue since I connected the boards PGND to chassis earth.

 

[lehmanhill]

Davy,

I don't have any specific ideas for you and I'm sure you already know the information in this article, but I keep a copy of the article around for reference because I forget stuff. Anyway, Doug Self is always an interesting read, so if you haven't seen it, here is Self's article on ground loops and hum.

Ground Loops

I hope the link works.

Jac

 

[bcmbob]

I just tried only connecting the DAC to the FE's, nothing else in circuit bar the speakers..........

I may be going in circles - but, last week I was checking for efficiency with a discrete amp. There I could connect a self contained CD/DVD player directly to the power amp 2 V line output RCA connectors. I did the same with the FEs, but with a bare pot between for safety - not knowing what the higher FEs gain would produce. Do you have unit for that trial?

(excuse ugly bare walls - new coat of paint and some audio room treatments in progress)

 

[davym]

Thanks Jac, the link works fine, i'll have a read through the article, I've just been reading another similar article re grounding. One thing I noticed is that most of these diagrams show the rca phono socket barrels connected to the chassis. I left mine floating although I did try connecting the ones on my passive preamp to it's enclosure, that made no difference.

Hi Bob, I did have an issue with a pin on the rotary selector switch of my passive preamp, I've since changed that to a 2 pole 2 way toggle switch and that sorted that issue. When just using the passive preamp between source and FE's, It doesn't add any more noise but it doesn't cure it either.

I might try making up some pseudo balanced interconnects, I have some twin and screen mic cable knocking about, that might be worth a try. Also I might buy some Belden 8241F coax for inters at some point to reduce shield resistance which should reduce noise.

Conventional logic dictates that if turning the volume up does not increase noise/hum levels then the issue must be after the control. That points to the amps themselves being the culprit. However shorting the amps signal inputs makes them almost completely silent, just the faintest noise left which I have to strain to hear even with my ear hard against the drivers.

My main speakers are very sensitive, that's one reason why I like them so much. When I use my cheap Sony bookshelf speakers for testing, I get near silence.
It could be I just have to accept things as they are which is not so bad, best sounding amps I have ever heard.

My current reading material - http://web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

 

[bcmbob]

No, I meant did you try a completely separate self-contained source like a CD player with RCA line outs. Just it and the FEs.

 

[davym]

Yes, my CD player and My DAC. I tried both on their own at different times. I get the same low level hum when just my CD player is plugged in as I do with just my DAC.

Anything mains powered and plugged into the FE's causes this low hum.

 

[damuffin]

Do you have any light dimmers in your home? They are great for producing hum in your mains. I have 105db/w compression drivers hooked up to the FE's and they don't make any detectable noise unless I have a dimmer on. Also check your input polarity's.