Wonder if it would improve with use...... i'll splash out on the Mundorf Supreme's for my next build 
According to russian website it is polystyrene
there are different caps like 71-4 71-7 etc
Mine is 71-4 and it was great on combination with obbligato 10uf with B1- gave best of both worlds
But it is too lean in place of c13
there are different caps like 71-4 71-7 etc
Mine is 71-4 and it was great on combination with obbligato 10uf with B1- gave best of both worlds
But it is too lean in place of c13
Soft start
Hello,
a quick survey: has someone installed a soft start (inrush current limiter) on this amp?
With a single 350VA toroid, I see occasional blow of the fuse.
Regards,
Daniele
Hello,
a quick survey: has someone installed a soft start (inrush current limiter) on this amp?
With a single 350VA toroid, I see occasional blow of the fuse.
Regards,
Daniele
What size fuse are you using? Is it Slo-Blo or fast acting? All the MyRef builds I've done have two transformers so I can't answer from experience.
It's slow-blow 1.6A.
Out of the blown fuses, the inrush current is not good for the transformer and for the rectifier diodes too.
Out of the blown fuses, the inrush current is not good for the transformer and for the rectifier diodes too.
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There are more knowledgeable thread members who might reply, but I have never been able to use lower than 2A SB over the long run. 1.6 gets you up and going but fuses weaken over time. I'm actually using 4A on the betas cause that's all I had on hand.
I just received the 0.1/100V/1% ERO MKP1837 (in record time from Taiwan) and swapped out the Wima MKP4 (green with red epoxy) at C4 on one of my oldest Rev C builds, a Twisted Pear V1.2 board (which has a PRP GP1/4 at R7, a Takman REY25 at R10, a Wima FKI2 at C12 and an LF07 Class-A opamp module). The audible improvement is sonics is fairly remarkable - fuller-bodied mids, better instrument separation and resolution, more air, definition, lower fatigue.
It is a remarkable film/foil capacitor, much better than anything in that size. For V1.2 and V1.3 boards, it's pretty much the best choice that fits comfortably at C4 (the leads have to be bent slightly outwards for the 7.5mm pitch, and it has to be raised about a mm or so to clear pins 1 &2 of the LM3886). For the V1.4 board, the larger 15mm-pitch Wima FKP3 film/foil also fits, but the MKP1837 may still be subjectively better - we'll see.
(I did not try to put these at snubber C5, where I've been using MKS3 for a long time without problems, because there might be ringing if C5 is excessively high-Q. I'll do that experiment later, it doesn't seem necessary or beneficial).
Great news Siva. I was busy the last few days with Salas Folded Phono and didnt get to change the cap. Probably will do it tonight and report back
Installed mkp1837 yesterday and although early to conclude i have to agree with you. Do you think a PPS cap in C5 will ring? I have some RIFA PPS and MKT1822, and thinking of trying them in C5
No idea, go ahead and try it out. I've only tried MKS3, MKS4, Evox MMK, ERO KT1826 (all polyesters) and a few metallized MKPs at C5. There wasn't really any noticeable difference in audible sonics, except that the MKPs seemed to have a slightly higher level of background-hash/noise-floor compared to the MKTs.
I have some Evox SMR or similar, but the pitch is 15mm, IIRC, so it's difficult to fit at C5.
@ Siva,
Other than the blue color versus gray, are these different from the Vishay Roderstein MKP1837 that Mouser sells? I only ask because I have some of the gray ones from Mouser sitting on my bench.
The ones I'm using are blue, with translucent brown epoxy filler. Text says ".1 F 100 ERO 1837 9416", not all on the same line. I'm guessing that it's NOS, manufactured in 16th week of 1994, prior to the merger of Roederstein with Vishay.
The gray ones should be fine if they fit - check if the leads are non-magnetic. The NOS blue ones are fully non-magnetic, like all other blue KP1837s that I've seen before (some have a red-brown opaque epoxy filler).
Can anyone tell me what the minimum input voltage (AC) is for the FE to work properly with a 6 Ohm speaker load? I'm sure this info is around somewhere but i cant find it.
I am using 22VAC transformers with 6ohm speakers in my setup. You may check the lm3886 data sheet to see what is minimum. Iirc 22VAC is recommended for 6ohm. I believe Dario confirmed this way back when.
Thanks. Trouble is that rated transformer voltages with our mains are usually miles out in reality. My current FE amps have 22v rated transformers which (with our mains voltage and a light load) produce around 25v. To me this is a bit too high for use with 6 Ohm speakers.
My mains is steady at 245v and a 50VA 12v transformer outputs aprox 14v.
I also have a 50VA 18v transformer which outputs just over 21v.
RS have 160VA 18v potted transformers which with my mains will probably output around 21v with a light load. They have a good reputation and are a reasonable price, I am seriously tempted to try a couple of them in the near future.
My mains is steady at 245v and a 50VA 12v transformer outputs aprox 14v.
I also have a 50VA 18v transformer which outputs just over 21v.
RS have 160VA 18v potted transformers which with my mains will probably output around 21v with a light load. They have a good reputation and are a reasonable price, I am seriously tempted to try a couple of them in the near future.
Davy Avel Lindberg do a nice range of encapsulated transformer with dual 120V primaries instead of the 115V of other manufacturers.Also they make to order with a short lead time.Chris Hall is the man to contact there.
Transformers and Power Converters From Avel Lindberg, Inc.
Transformers and Power Converters From Avel Lindberg, Inc.
Compensation values experimentation just completed. These are my impresssions from careful listening to my system. All testing was done with Caddock MK132's at R10, as the Rikens masked too much detail to be considered accurate. All comments relate to high and midrange frequencies; bass was not evaluated. All parts were soldered in place; no sockets were used. Only one component value was changed in one amplifier at a time, and listening notes were made comparing the changed amp to the previous best version. I used high fidelity mono and stereo recordings with a variety of instruments and vocals, sometimes listening right in front of a speaker, sometimes in normal seating position 12 or so feet away. All listening was done after equipment had played for a few hours, and all sessions were over the course of two days or more to allow for atmospheric and psychological variances. Tests were sighted, but I have no preference for any particular combination to be better than another, so there is NO bias.
Initial values C10 33pF C34 27pF, known as alternate comp: excessively bright and mechanical with plenty of details but no coherence. Could not enjoy listening to music due to sharpness of mids. Cymbals are pure sizzle with no ringing tone. Vocals distorted with sibilance, mechanical.
C10 33pF, C34 22pF: somewhat less bright but still a definite sharp edge. Good detail and depth, more coherent, but not much like real music. Cymbals ting but not much ring. Vocals were distorted with sibilance.
C10 27pF, C34 22pF: less bright but still a slightly sharp edge. Somewhat more musical, but not at all coherent, a sort of roughness to the sound. Possibly a step back from 33/22. Cymbals unclear. Vocals were difficult to understand.
C10 33pF, C34 15pF: brightness gone, no sharp edge, very good depth of image, coherent and smooth, very musical, slight emphasis on mids but excellent detail to highs. Cymbals ting sharply and then ring "deeply" with gradual decay. Vocals were realistically present, eminently intelligible.
C10 27pF, C34 15pF: dull, lifeless highs, but decent depth and musical sound. Too laid back. Cymbals all ring with little ting. Sounds like Riken back in circuit. Vocals were muffled.
C10 27pF, C34 18pF: better detail and good depth with exciting sax and string sound, but a strange squeaky resonance to trumpet and piano. A few upper mid notes were considerably louder than most. Cymbals seem realistic, slightly more ring than ting. Vocals were unusually highlighted at times.
C10 33pF, C34 18pF: slightly bright, decent depth, but somewhat peaky upper mids, aggressive trumpet, bit too much snap on snare drum. Cymbals very prominent with more ting than ring. Vocals clear, but clarinet could be squeaky on certain notes.
I am tired of taking amps apart and swapping parts. A testament to the quality of the boards is that only one pad lifted from all this desoldering. I am satisfied that 33/15 is the best combination I heard with MK132's at R10. It has truthful midrange timbre and high frequency clarity, very good depth of image, and a pleasing overall realism. It seems to be similar to the Rev C comp, with slightly better presence of vocals and details of highs, but I did not make a direct comparison. It sounds better the longer one listens to it, unlike any of the others, which became irritating during longer sessions.
I am interested to learn anyone else's impressions.
Peace,
Tom E
Initial values C10 33pF C34 27pF, known as alternate comp: excessively bright and mechanical with plenty of details but no coherence. Could not enjoy listening to music due to sharpness of mids. Cymbals are pure sizzle with no ringing tone. Vocals distorted with sibilance, mechanical.
C10 33pF, C34 22pF: somewhat less bright but still a definite sharp edge. Good detail and depth, more coherent, but not much like real music. Cymbals ting but not much ring. Vocals were distorted with sibilance.
C10 27pF, C34 22pF: less bright but still a slightly sharp edge. Somewhat more musical, but not at all coherent, a sort of roughness to the sound. Possibly a step back from 33/22. Cymbals unclear. Vocals were difficult to understand.
C10 33pF, C34 15pF: brightness gone, no sharp edge, very good depth of image, coherent and smooth, very musical, slight emphasis on mids but excellent detail to highs. Cymbals ting sharply and then ring "deeply" with gradual decay. Vocals were realistically present, eminently intelligible.
C10 27pF, C34 15pF: dull, lifeless highs, but decent depth and musical sound. Too laid back. Cymbals all ring with little ting. Sounds like Riken back in circuit. Vocals were muffled.
C10 27pF, C34 18pF: better detail and good depth with exciting sax and string sound, but a strange squeaky resonance to trumpet and piano. A few upper mid notes were considerably louder than most. Cymbals seem realistic, slightly more ring than ting. Vocals were unusually highlighted at times.
C10 33pF, C34 18pF: slightly bright, decent depth, but somewhat peaky upper mids, aggressive trumpet, bit too much snap on snare drum. Cymbals very prominent with more ting than ring. Vocals clear, but clarinet could be squeaky on certain notes.
I am tired of taking amps apart and swapping parts. A testament to the quality of the boards is that only one pad lifted from all this desoldering. I am satisfied that 33/15 is the best combination I heard with MK132's at R10. It has truthful midrange timbre and high frequency clarity, very good depth of image, and a pleasing overall realism. It seems to be similar to the Rev C comp, with slightly better presence of vocals and details of highs, but I did not make a direct comparison. It sounds better the longer one listens to it, unlike any of the others, which became irritating during longer sessions.
I am interested to learn anyone else's impressions.
Peace,
Tom E