For those who haven't seen it yet, diyAudio's own Scott Wurcer has measured an Edcor PC600-15K as used in the First Watt M2, and built a SPICE simulation model that fits his measurements. So, if anybody was planning to put M2 into LTSPICE, your task just got a little easier.
The model for 6X gain {as Nelson Pass used in the M2} is on the left; Scott also modeled another way of connecting the Edcor transformer (that nobody has yet built into an amplifier) with 11X gain, on the right.
Here is the post: LINK
Questions? Scott is the guy most likely to know the answers.
The model for 6X gain {as Nelson Pass used in the M2} is on the left; Scott also modeled another way of connecting the Edcor transformer (that nobody has yet built into an amplifier) with 11X gain, on the right.
Here is the post: LINK
Questions? Scott is the guy most likely to know the answers.
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I have similar situation with my M2 and active preamplifier.
Sometimes with efficient drivers gain structure is too much dB.
After connection to passive preamplifier autoformer volume control I was nicely surprised
by totaly silencious noise free = quiet background.
M2 jfet buffer stage is passive preamp friedly , simple potentiometer for start of experimentation can do the job.
Light depended volume control and all AVC or steps attenuators are interesting to explore .
M2 it's noticable sensible to quality of all passive components , cap's ,
no polarised bypass cap's , resistors, source resistors, and psu quality.
Congratulation Kbergsson Your audio system have lot's of potential and possibilitys 🙂
Thanks!
The PSU is a simple CLC with Hammond 159ZJ chokes instead of the resistors on the Tea-Bag PSU PCB.
Mains trafos is 600VA 2x20v, capacitors is 47000uf 35v each - choosen as they where the biggest snap-in i could find. I chose doing chokes because I found out I had the space and I was going for overkill anyway.. 🙄
Just finished m2, still on the carpet, no box, had to adjust r6 to zero offset on the output. Sounds great from the start.
Thanks Soundhappy 🙂 Ill try the M2 with my Slagle autoformer passive. Re. component quality, I used teabags bom almost 100%. What pussles me though is that I get excactly the same noise from both channels and the only thing common for both channels, is the enclosure, 230V powercable and on-off swich. There are separate fuses, then everything is separate until separate cl60s connect to housing earth. Could it be dirt from the powersupply? Should I try to add a 10uF Wima ( happen to have 4 big 400v ) across the second caps in the CRC? Supply is 47000uF cap, 0R1, 47000uF cap, with a 2.2k bleeder across first cap, 2.5mm^2 wires all the way to the pcbs.
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My M2 clone has a separate PSU (smps) enclosure. It is the quietest amp I have built yet.
I don't necessarily credit the smps (although I am leading to SMPS more and more), but the proximity to the amp's boards is the problem IMHO. EMI is pretty tough to deal with. In my case, it would be RFI! (but I can't hear RF, too old I guess 🙂 )
The other day I switched to the Aleph 5 clone for a change. That lasted a few minutes. The M2 really is a special amp for me.
I don't necessarily credit the smps (although I am leading to SMPS more and more), but the proximity to the amp's boards is the problem IMHO. EMI is pretty tough to deal with. In my case, it would be RFI! (but I can't hear RF, too old I guess 🙂 )
The other day I switched to the Aleph 5 clone for a change. That lasted a few minutes. The M2 really is a special amp for me.
My point was that in my opinion, getting the PSU out of the amp might be the best upgrade you can do.
I'm using two Vicor 300w 24v flatpacs in series. Currently have 1000uf per rail on each amp board. might experiment further. I've used these PSUs with 30,000uf and they start fine.
http://www.vicorpower.com/documents/datasheets/ds_flatpac.pdf
I'm using two Vicor 300w 24v flatpacs in series. Currently have 1000uf per rail on each amp board. might experiment further. I've used these PSUs with 30,000uf and they start fine.
http://www.vicorpower.com/documents/datasheets/ds_flatpac.pdf
Ok, so when you say in series, does that mean like the attached drawing, so that you get +24V DC, zero (0) and -24V DC?
That where my initial thoughts, i.e. separate the powesupply from the amp. I might still do 4 chassis monoblocks i.e separate supply per block. SMPS is also interesting. As the amps are for me commercial and cost saving production issues dont count at all.
is it noise as noise ........ I mean - pinkish/whitish/FM-ish/whatever noise , or it is hum (lower in frequency , more or less dense buzz ) ?
whatever it is , you can make one test , but you need silence in room and eyes closed while doing it , with ear(s) near speaker
if there is magnetically induced problem , in very moment when you flick power switch off , it goes away
if there is ground loop/current routes arrangement problem , when you flick power switch off , problem stays while caps are capable to deliver some current ,which happens fast but longer duration than previous one
if there is noise pinkish/whitish/FM-ish problem, when you flick power switch off , problem stays while caps are capable to deliver some current , and that lasts as long caps are having even tiniest smidge of juice to power actual circuit , and it's certainly longer than two previous cases
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Thanks ZM ill test this evening when Im back home. Regarding offset,
I adjusted with input open ( got to ca 1mv my instruments are not that precise). Should I adjust with inputs shorted?
I adjusted with input open ( got to ca 1mv my instruments are not that precise). Should I adjust with inputs shorted?
as long you're in 50mV range , in temp equilibrium , you're good
you're good even with more , but that's just in case of speaking to someone having 3W speakers , sensitive to Sparrow's fart , 3 blocks far away
🙂
I'm generally always setting amp's general conditionals with input shorted , out free ...... then signal and load for operational settings
you're good even with more , but that's just in case of speaking to someone having 3W speakers , sensitive to Sparrow's fart , 3 blocks far away
🙂
I'm generally always setting amp's general conditionals with input shorted , out free ...... then signal and load for operational settings
The hum goes away immediately as I switch off.
I still find it interesting that the magnitude/level of the hum is equal in both channels.
Im using a screened inexpensive mic cable for input wiring. Ill try som cat5/6 twisted pairs in stead.
I still find it interesting that the magnitude/level of the hum is equal in both channels.
Im using a screened inexpensive mic cable for input wiring. Ill try som cat5/6 twisted pairs in stead.
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Before you change things at random. Try shorting a couple of strategic places in the signal path to ground before turning on - to see if the hum goes away.
Input at pcb and then output of the transformer will tell you much 🙂
Input at pcb and then output of the transformer will tell you much 🙂
yup
if you ground positive side of Silmic and hum is gone , you're in trouble - Donut spilling too much on Edcor
try rotating a Donut .... and if that not helps , you're in trouble ..... double
if you ground positive side of Silmic and hum is gone , you're in trouble - Donut spilling too much on Edcor
try rotating a Donut .... and if that not helps , you're in trouble ..... double
Thanks Twst I will try, although is easier said than done as there is not much space.
@ZM saw your mail later, Ill test. But isnt it puzzling that I get the same level from both channels of a double mono? I.e. If its the edcors they are getting the same dose. I think Ill start by starting one channel at a time by pulling one fuse at a time.
@ZM saw your mail later, Ill test. But isnt it puzzling that I get the same level from both channels of a double mono? I.e. If its the edcors they are getting the same dose. I think Ill start by starting one channel at a time by pulling one fuse at a time.
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You could try getting a probe, little lead or something to one of the solder lug near the transformer marked C2 -should be a couple of them for optional capacitors on Tea Bag boards. Right next to the transformer. Should do the trick 🙂