MDAC First Listen (Part 00101010)
- Thread starter jirij
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+1 on that, Peter. I was just thinking the same thing. Thanks, John.
JohnW
pfm member
JohnW
pfm member
They do need their top end to be less head shattering tho
Yes - in standard form the they can take your head off from 3 Meters away!
There are two basic design errors + the horrid Opamp that will lead to treble brightness with a solid state design! all easy to fix
+ I'd like to have alittle fun.I'll need to set up my system for the Detox and FDAC analogue board "first listen", once the PCB design files have been issued I can spend a couple of days on these amps...
I know what I'd really like to do....
if space allows!
JohnW
pfm member
John as previously discussed , I would also be interested in a pair of modded 8200mb to tie me over and to use in a surround setup afterwards .... But only if there is time between your busy schedule
Phil, I checked my scraps of paper I call records and you have x3 8200MB's reserved... I must pass this information onto Renata!
JohnW
pfm member
OK - I feel really bad about the MPWR - please don't tell me I sold you the MPWR when you already had the ESL ElectroMotions?
I'll keep a pair reserved for you - I need to complete the DETOX and FDAC Analogue PCB first (by Mid October) then I'll work on the 8200MB's - if I can squeeze in my "crazy" idea then they will be PERFECT for your ESL's (as the VFET amps are silly money!)
JohnW
pfm member
Phil,
OK, a pair reserved for you, you should consider having the Vishay Bulk foils fitted
(Bulk foils fitted "at cost")...As I mentioned in earlier Emails, I'll play with the amps once I've completed DETOX and FDAC analogue board - I'd like to use a Miniature tube in the front end circuit but need to figure how to provide the heater supply rail.
With the circuit corrections, Tube front end (if possible), remove the cheap Opamp + True balanced input stage then they will be more then decent
Atleast something I can use before the VFETs come online...I need to turn these units back into cash as I will soon need to pay the tooling costs for the VFET chassis and prototypes etc.
JohnW
pfm member
Yes, sorry the PFM inbox only has 50 spaces, and it fills very quickly...
Renata's just emailing you my EMail address - but these 8200MB's are only 230V units
This sounds very promising, thank you
And no, don't worry - at the time, I bought your S-MPWR, I owned a pair of Totem Arros. I really loved that combo!! But then I gave the ElectroMotions a trial and even though they do not have the perfectly matching amp/s yet, I'm very happy with how they perform!
Kind regards
Malyq
JohnW
pfm member
This sounds very promising, thank you
But then I gave the ElectroMotions a trial and even though they do not have the perfectly matching amp/s yet, I'm very happy with how they perform!
Kind regards
Malyq
Yes I remember now
gosh I could not believe I would have sold you the MPWR even when so heavily modified to drive a pair of ElectroMotions!The ElectroMotions are a really really nice speaker, I'd happily have a pair for myself! I purchased a set from the US a while back, but then the shipper realised the shipping costs to the Czech Rep. he backed out of the deal!
I managed to buy a used pair of Accustats (about the same size as the ElectroMotions - but they are not as nice looking and I have no idea how they sound - but I'll try the modified MB's on these first (It be a great if I could add the miniature tube in the MB front end, this would work very well with the RF generated by digital products)
Keen to get the Detox and FDAC PCB issued so I can play with the amps - I'm so looking forward to listening to a high quality system once again...
JohnW
pfm member
OK, I keep you in mind (theres a couple of pallets of the amps in the basement, so there's quite a few
), I first need to clear out the DETOX PCB etc. before I work on the amps - I'd really like to add the tube if possible.. 
ti33er
pfm Member
Hi John
The above is true about an early batch of 8200MB that went out with faulty transistors, unfortunately.
I would be interested in a black pair if you could do these mods and beef up the transformer/capacitors too? Caps would be easy as I could source some 15000uF that may fit and send; larger transformer it's possible IAG still have some of the 650 from Tag spares?
If it's too much faff I may just wait/hold out in case you make some pseudo VFET amps later like you thought about doing triodes,
as an afterthought with the current dumping stage from VFET?
Thanks
The above is true about an early batch of 8200MB that went out with faulty transistors, unfortunately.
I would be interested in a black pair if you could do these mods and beef up the transformer/capacitors too? Caps would be easy as I could source some 15000uF that may fit and send; larger transformer it's possible IAG still have some of the 650 from Tag spares?
If it's too much faff I may just wait/hold out in case you make some pseudo VFET amps later like you thought about doing triodes,
as an afterthought with the current dumping stage from VFET?
Thanks
JohnW
pfm member
I don't believe that the 8200MB's transformers where ever rated at 650VA as a 650VA transformer is just to large to fit within the existing chassis - atleast the IAG 8200MB chassis, I cannot say what went before.
https://dl.dropboxusercontent.com/u/86116171/MB1.JPG
https://dl.dropboxusercontent.com/u/86116171/MB3.JPG
As you can see from the above picture, its impossible to ft a transformer within the case - and anyway the 8200MB in there current form are not power limited
The modifications are to improve the sound quality by correcting the rather fundamental design issues with the amps - the target is to keep the 8200MB's very impressive Bass performance but resolving the designs terrible Treble brightness.
Current dumping etc. is a step to far with these units - although I'd like to explore to possibility to add a tube to the front-end if I can find away to power the tubes heater.
They will modified for Balanced operation only, no single-end input. The planned modification will convert the design to a true balanced input stage whose gain is optimised for use with the MDAC / FDAC.
https://dl.dropboxusercontent.com/u/86116171/MB1.JPG
https://dl.dropboxusercontent.com/u/86116171/MB3.JPG
As you can see from the above picture, its impossible to ft a transformer within the case - and anyway the 8200MB in there current form are not power limited
The modifications are to improve the sound quality by correcting the rather fundamental design issues with the amps - the target is to keep the 8200MB's very impressive Bass performance but resolving the designs terrible Treble brightness.
Current dumping etc. is a step to far with these units - although I'd like to explore to possibility to add a tube to the front-end if I can find away to power the tubes heater.
They will modified for Balanced operation only, no single-end input. The planned modification will convert the design to a true balanced input stage whose gain is optimised for use with the MDAC / FDAC.
ti33er
pfm Member
Hi John
Thanks for the reply and really not trying to tell porky-pies, nor necessarily upset you.
It's bizarre but I was certain it was a 650VA in the 250MR Tag McLaren modules!? - Ricardo still has these and hopefully, if he has the inclination to open his TMA mono to verify?
https://www.avforums.com/threads/th...-same-as-the-tag-mclaren-250mr.1411129/page-2
See Post #42 as an example - Kevin had sourced an original 650VA Transformer and sent to our French friend a few years ago...
"I dismantle a 250MR. I measured the diameter of the conductors of the transformer primary. They are larger than those of 8200MB. The show features 8200MB 380VA and 650VA those of the 250MR."
I saw someone else even managed to retro-fit 800VA transformers into his 250X2R, but I can't find that old thread now that I look?
Cest la vie...if AUDIOLAB have changed the case in such a way, it is what it is now.
Your mods sound very promising nonetheless and on my shortlist ...I would love VFET but its just a stretch too far - around £1K-2K I could muster up in the future, but I would like to buy right this time (running with Monitor Audio PL200 which are £5250 speakers so deserve something slightly exotic)
Best regards
Paul
Thanks for the reply and really not trying to tell porky-pies, nor necessarily upset you.
It's bizarre but I was certain it was a 650VA in the 250MR Tag McLaren modules!? - Ricardo still has these and hopefully, if he has the inclination to open his TMA mono to verify?
https://www.avforums.com/threads/th...-same-as-the-tag-mclaren-250mr.1411129/page-2
See Post #42 as an example - Kevin had sourced an original 650VA Transformer and sent to our French friend a few years ago...
"I dismantle a 250MR. I measured the diameter of the conductors of the transformer primary. They are larger than those of 8200MB. The show features 8200MB 380VA and 650VA those of the 250MR."
I saw someone else even managed to retro-fit 800VA transformers into his 250X2R, but I can't find that old thread now that I look?
Cest la vie...if AUDIOLAB have changed the case in such a way, it is what it is now.
Your mods sound very promising nonetheless and on my shortlist ...I would love VFET but its just a stretch too far - around £1K-2K I could muster up in the future, but I would like to buy right this time (running with Monitor Audio PL200 which are £5250 speakers so deserve something slightly exotic)
Best regards
Paul
Phil,
OK, a pair reserved for you, you should consider having the Vishay Bulk foils fitted
As I mentioned in earlier Emails, I'll play with the amps once I've completed DETOX and FDAC analogue board - I'd like to use a Miniature tube in the front end circuit but need to figure how to provide the heater supply rail.
With the circuit corrections, Tube front end (if possible), remove the cheap Opamp + True balanced input stage then they will be more then decent
I need to turn these units back into cash as I will soon need to pay the tooling costs for the VFET chassis and prototypes etc.
Happy to do so John. Any idea what the 'at cost' cost is likely to be?
Yes, sorry the PFM inbox only has 50 spaces, and it fills very quickly...
Renata's just emailing you my EMail address - but these 8200MB's are only 230V units
Got it! Tnx
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