timola
pfm Member
please explain your merriment.... A bit slow on the uptake here...thanks.
MDAC First Listen (Part 00101010)
- Thread starter jirij
- Start date
- Status
Obi1
Swedish HiFi enthusiast
You might want to check out REL. They do nice subs with high level inputs, as well as low level of course. You can even use them simultaniously if needed.
stellablues
pfm Member
JohnW,
Assuming the new FDAC replaces the front screen of my MDAC, I no longer need to be worried about it wearing out over time, so I can 'downgrade' to v90 without fear?
Assuming the new FDAC replaces the front screen of my MDAC, I no longer need to be worried about it wearing out over time, so I can 'downgrade' to v90 without fear?
stellablues
pfm Member
John, what is the reason for including it within the xlr wiring instead of a second wire for only this purpose. won't this remove the option to use most xlr on the market?
JohnW
pfm member
Because the "main" signal and return feedback signals need to run paralleled to each other so the effects of magnetic field pickup are cancelled - the StarQuad balanced cables are perfect for this application.
http://www.belden.com/blog/broadcastav/How-Starquad-Works.cfm
http://www.canford.co.uk/Starquad-cables
http://www.canare.com/UploadedDocuments/Cat11_p35.pdf
I don't expect many to use the 5W XLR's, but I personally will as I always strive for the best.
In time I hope to be able to source "custom" cables at an affordable price - but that's for later.
http://www.belden.com/blog/broadcastav/How-Starquad-Works.cfm
http://www.canford.co.uk/Starquad-cables
http://www.canare.com/UploadedDocuments/Cat11_p35.pdf
I don't expect many to use the 5W XLR's, but I personally will as I always strive for the best.
In time I hope to be able to source "custom" cables at an affordable price - but that's for later.
JohnW
pfm member
Yes, the purchase of the EMs was a consequence of your recommendation approx. one year ago - many thanks for that, as these are the best speakers I owned to date
I spent a couple of hours this weekend working on computer simulations of the 8200MB design to confirm my suspicions - whoever was responsible for its design lacked some rather basic understanding.
I added 3 components worth maybe US$0.25, optimized component values and changed a few component positions in the circuit which has made dramatic improvements to many important measurement characteristics such as power supply rejection, noise, distortion and resolved the high frequency peaking in the openloop response etc....
Power supply rejection has been improved by over x100 times, HF THD dropped to silly levels, and quite nasty "peaking" at around 2MHz has be tamed.... all for the cost of US$0.25 in components...
Considering the cost of these amps, it upsets me to see such poor design.
I believe they should now will be decent amps - if I can get the tube fitted in the input stage then they will be little jewels!
JohnW
pfm member
As expected the Regen switch mode power supply (SMPS) is a disaster area, I avoid SMPS PSU's because they are nothing but a huge bag of hurt and should not be allowed anywhere near a HiFi system... They can be designed for low noise, but then they become far more expensive and requires a skilled designer.
The SMPS PSU supplied with the ReGen tries to "obscure" its RF output noise by VERY crude spread spectrum in an effort to ease EMC tests. My measurements show the switching frequency hopping around between discrete "spot" frequencies - just so crude.
Forgive me, things like this make me so down as I work so very hard to design a "correct" product then I see devices like this selling... Apparently the Regen guys claim this is a low noise SMPS design - if true, then it only begs the question what Crxp is considered "normal"...
Regen PSU noise measured with a "nothing special" lab linear PSU - note the 8KHz related USB noise currents on the PSU rail.
https://dl.dropboxusercontent.com/u/86116171/Regen Linear PSU Standard PCB.jpg
I added 3 modifications to the Regen PCB to reduce the USB packet noise, otherwise the same as above with the linear PSU:-
https://dl.dropboxusercontent.com/u/86116171/Regen nosie Linear PSU Modifed PCB.jpg
Now the "standard" non-modified Regen PCB with its Switch Mode Power Supply:-
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise.jpg
Note the massive "clumps" of spread spectrum SMPS noise!!! You really don't want these HF noise currents circulating around your HiFi system!
As above with SMPS but with the modifications to the Regen design to reduce the 8KHz USB related packet noise on the PCB, for the most part we are left with the rather nasty SMPS noise:-
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise modifed PCB.jpg
Zoom FFT of the SMPS noise, here you can clearly see the discrete SMPS switching carrier "Bins" as it VERY crudely hops about in an effort to hide itself from the averaging peak sweep detector used during EMC testing. Spread spectrum works well if correctly implemented with a true random carrier - but not here where its clearly just hopping about between a few discrete spot frequencies.
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise zoom modifed PCB.jpg
IMO, "off the shelf" SMPS designs have no place in HiFi systems. I've read reports of owners using the SMPS reporting "Brightness" and that's a VERY typical sonic signature of unwanted RF currents being injected into the HiFi system.
This is not aimed at the ReGen specifically, just at "off the shelf" SMPS designs in general. Although I strongly suggest that the Regen should never have been provided with an SMPS as this PSU can have a greater negative impact on a systems performance then the original issues the Regen is trying to resolve.
The SMPS PSU supplied with the ReGen tries to "obscure" its RF output noise by VERY crude spread spectrum in an effort to ease EMC tests. My measurements show the switching frequency hopping around between discrete "spot" frequencies - just so crude.
Forgive me, things like this make me so down as I work so very hard to design a "correct" product then I see devices like this selling... Apparently the Regen guys claim this is a low noise SMPS design - if true, then it only begs the question what Crxp is considered "normal"...
Regen PSU noise measured with a "nothing special" lab linear PSU - note the 8KHz related USB noise currents on the PSU rail.
https://dl.dropboxusercontent.com/u/86116171/Regen Linear PSU Standard PCB.jpg
I added 3 modifications to the Regen PCB to reduce the USB packet noise, otherwise the same as above with the linear PSU:-
https://dl.dropboxusercontent.com/u/86116171/Regen nosie Linear PSU Modifed PCB.jpg
Now the "standard" non-modified Regen PCB with its Switch Mode Power Supply:-
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise.jpg
Note the massive "clumps" of spread spectrum SMPS noise!!! You really don't want these HF noise currents circulating around your HiFi system!
As above with SMPS but with the modifications to the Regen design to reduce the 8KHz USB related packet noise on the PCB, for the most part we are left with the rather nasty SMPS noise:-
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise modifed PCB.jpg
Zoom FFT of the SMPS noise, here you can clearly see the discrete SMPS switching carrier "Bins" as it VERY crudely hops about in an effort to hide itself from the averaging peak sweep detector used during EMC testing. Spread spectrum works well if correctly implemented with a true random carrier - but not here where its clearly just hopping about between a few discrete spot frequencies.
https://dl.dropboxusercontent.com/u/86116171/Regen SMPS noise zoom modifed PCB.jpg
IMO, "off the shelf" SMPS designs have no place in HiFi systems. I've read reports of owners using the SMPS reporting "Brightness" and that's a VERY typical sonic signature of unwanted RF currents being injected into the HiFi system.
This is not aimed at the ReGen specifically, just at "off the shelf" SMPS designs in general. Although I strongly suggest that the Regen should never have been provided with an SMPS as this PSU can have a greater negative impact on a systems performance then the original issues the Regen is trying to resolve.
JohnW
pfm member
Impressive results John after so little cost .
Were the units all in working order , or will you have to test and fix each individual problem for each unit?
They all have the same design issues - and will respond to the same solutions
The Amps are brand new and still sealed, I've only open a single unit...
This pending "Joy" is reserved for later, once I've issued the Detox / FDAC analogue PCB files...
To Tube or not to Tube is the question
JohnW
pfm member
FDAC will have standard 12V trigger outputs as on the CDQ....
Thanks.
Also, do we still have AV bypass?
Thinking out loud, I am trying to visualise how this will fit into myAV system. If FDAC has Dirac, I would want to use that to drive my L&R speakers for max SQ with music ( I will have separate power amps). However I still want to feed my AV amp through it when watching films - it can use the built in audyssey for that. Also my current AV amp only has single ended RCA outs. Will the bypass be just RCA in to RCA out, or will it also be XLR in to XLR out?
JohnW
pfm member
The FDAC has XLR input AV Bypass, you can use a RCA to XLR lead and still use XLR or RCA output to the Amps.
Fab! Problem solved, the amps will be XLR - next question ( a bit rhetorical) do I go for your modified 8200s or Ncore power amps ???????
Oh BTW am I correct to presume the bypass will be passive and not buffered?
JohnW
pfm member
Fab! Problem solved, the amps will be XLR - next question ( a bit rhetorical) do I go for your modified 8200s or Ncore power amps ???????
IIRC your based in Australia? - so better go with the Ncores in case you have a service problem with the modified 8200MB's! its sods law that if ones to go flaky it will be a unit on the otherside of the world - and they are quite heavy...
I'd like to keep these hand modified "Tube" 8200MB's close to home in case of any problems.
- Status