UV101
15-05-2010, 11:12
Hi Guys,
I thought I’d share my latest round of mods here!
I've had my Restek Fantasy MKI amp for a few years now and knowing its about 13ish, I’ve been thinking about recapping it and changing a few opamp and having a general poke about. I struggled with Restek and although they've emailed me just about piece of paperwork on the unit they produced, no schematic was forthcoming!
The design is very good. Fully dual mono power sections running from separate 100VA transformers, recs and caps (10,000uF per rail). This was my 1st upgrade! I swapped out the tired Philips LL caps for replacement F&T of equivalent value. I then added the same again off board bring the total smoother capacity to 20,000uF per rail (a whopping 80,000uF in total). There are a handful of similar Philips local decoupling caps around the power stage ranging from 220uF to 470uF. These were swapped for similar value Panasonic FMs with the exception of the main op device caps, here I changed from 2x470uF to 1x470uF and 1x1000uF.
There is an opamp in the beginning of the power stage. This was originally a BB604. I had previously tried to swap out for single Burson discrete opamps but the amp wouldn’t come out of protect mode. I would love to know why but without the diagram...... I swapped this for LME49710HA decoupled with Nichicon ( I may swap to Rubycon ZA’s) I’ve also swapped the input DC blocking set up here from a 22uF elco bypassed with a 1uF MKP to a WIMA 22uF MKS2-XL cap. Both the signal and signal ground are decoupled. I guess this is for complete isolation.
The preamp section is pretty basic (it looks like the £ went into the power stage!!!). It consisted of an opamp buffer into an opamp gain stage followed by a Blue Alps volume control and finally another opamp gain stage. I had previously changed the standard BB 2604’s for LME49720HA’s decoupled with Rubycon ZA’s. I wasn’t convinced the pre section was particularly good even with the different opamps. I’ve now recapped the LM317/337 regs supplying the pre section and have some Avondale tracking regs boards on the way to try here (Thanks Chrism/Les) and I may run separate TX and PSU when I build them. I’ve now swapped out the LME’s for Burson discrete opamps and bypassed the buffer stage. These discrete opamps are expensive but well worth the money (it’s also what I use for I/V on my TDA cdp).
The results are unbelievable! This amp was already punchy and dynamic now it’s off the scale! The components have been in for about 50hrs now and as such should be starting to burn in nicely. I would now describe the amp as massively dynamic. It was quite a forward maybe harsh sound before but this has subsided without loss of detail. It sounds very capable easily the best amp I’ve ever owned!
The cost of the caps totalled approx. £80, the 2 LME49710HA £26 and the Burson £90. I hadn’t initially planned to upgrade to Burson so the cap swap wasn’t going to be that expensive! In the end, it was no cheap upgrade but considering the gains, I consider it to be well worth it.
I would definitely recommend a cap refresh to anyone with 10+ year old amp. Those low ESR F&T caps (10,000uF/63v) are excellent value for money @ £7 each. The Panasonic FM caps are also great value for the elcos in the amp stage itself!
I still need to fit the Bursons properly and get it all back together here's the pics cos I know we all like pics!!!! :lol:
Before
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/before.jpg
in the middle!
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/during.jpg
After :):)
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Final.jpg
output stage with FM's
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Outputstage.jpg
More FM's
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/FMdecouple.jpg
F&T Smoothers
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/FTsmoother.jpg
More F&T Smoothers - all 80,000uF!!!
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/80000uFFT.jpg
Bursons up close
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Brusons.jpg
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Bursons2.jpg
Cheers!!!
I thought I’d share my latest round of mods here!
I've had my Restek Fantasy MKI amp for a few years now and knowing its about 13ish, I’ve been thinking about recapping it and changing a few opamp and having a general poke about. I struggled with Restek and although they've emailed me just about piece of paperwork on the unit they produced, no schematic was forthcoming!
The design is very good. Fully dual mono power sections running from separate 100VA transformers, recs and caps (10,000uF per rail). This was my 1st upgrade! I swapped out the tired Philips LL caps for replacement F&T of equivalent value. I then added the same again off board bring the total smoother capacity to 20,000uF per rail (a whopping 80,000uF in total). There are a handful of similar Philips local decoupling caps around the power stage ranging from 220uF to 470uF. These were swapped for similar value Panasonic FMs with the exception of the main op device caps, here I changed from 2x470uF to 1x470uF and 1x1000uF.
There is an opamp in the beginning of the power stage. This was originally a BB604. I had previously tried to swap out for single Burson discrete opamps but the amp wouldn’t come out of protect mode. I would love to know why but without the diagram...... I swapped this for LME49710HA decoupled with Nichicon ( I may swap to Rubycon ZA’s) I’ve also swapped the input DC blocking set up here from a 22uF elco bypassed with a 1uF MKP to a WIMA 22uF MKS2-XL cap. Both the signal and signal ground are decoupled. I guess this is for complete isolation.
The preamp section is pretty basic (it looks like the £ went into the power stage!!!). It consisted of an opamp buffer into an opamp gain stage followed by a Blue Alps volume control and finally another opamp gain stage. I had previously changed the standard BB 2604’s for LME49720HA’s decoupled with Rubycon ZA’s. I wasn’t convinced the pre section was particularly good even with the different opamps. I’ve now recapped the LM317/337 regs supplying the pre section and have some Avondale tracking regs boards on the way to try here (Thanks Chrism/Les) and I may run separate TX and PSU when I build them. I’ve now swapped out the LME’s for Burson discrete opamps and bypassed the buffer stage. These discrete opamps are expensive but well worth the money (it’s also what I use for I/V on my TDA cdp).
The results are unbelievable! This amp was already punchy and dynamic now it’s off the scale! The components have been in for about 50hrs now and as such should be starting to burn in nicely. I would now describe the amp as massively dynamic. It was quite a forward maybe harsh sound before but this has subsided without loss of detail. It sounds very capable easily the best amp I’ve ever owned!
The cost of the caps totalled approx. £80, the 2 LME49710HA £26 and the Burson £90. I hadn’t initially planned to upgrade to Burson so the cap swap wasn’t going to be that expensive! In the end, it was no cheap upgrade but considering the gains, I consider it to be well worth it.
I would definitely recommend a cap refresh to anyone with 10+ year old amp. Those low ESR F&T caps (10,000uF/63v) are excellent value for money @ £7 each. The Panasonic FM caps are also great value for the elcos in the amp stage itself!
I still need to fit the Bursons properly and get it all back together here's the pics cos I know we all like pics!!!! :lol:
Before
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/before.jpg
in the middle!
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/during.jpg
After :):)
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Final.jpg
output stage with FM's
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Outputstage.jpg
More FM's
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/FMdecouple.jpg
F&T Smoothers
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/FTsmoother.jpg
More F&T Smoothers - all 80,000uF!!!
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/80000uFFT.jpg
Bursons up close
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Brusons.jpg
http://i497.photobucket.com/albums/rr332/Trunky1812/RESTEK%20FANTASY/Bursons2.jpg
Cheers!!!