Hi all, I wrote in about a month or so back looking for any information on the Eidetic GB-1b power amplifier, I know Greg Ball seems to be out of the mainstream action at the moment (unless I'm quite wrong!), but I could really do with a full circuit diagram and voltage adjustment info if possible. I have picked up an amp recently that has very high DC on both outputs .. well, I consider 300mV+ on the LC very high and a bit less on the RC. Looks like one of the output trannies has got a bit hot on the board (LC). I will probably replace all caps on the boards, one or two look like they've taken a bit of a beating over the years, the mains switch has been replaced with an el cheap job that's too small for the cutout and I have no idea whether the plug on the back is pulled out for 1-2 ohms and left in for 6-8 ohms or what. No instructions for adjusting DC or bias and those I'd really like if possible.
Anyone got any ideas please? Any help from previous owners would be much appreciated! Thank you.
Anyone got any ideas please? Any help from previous owners would be much appreciated! Thank you.
Hi,
Are you Sydney based? If so, I have a working Eidetic power and pre-amp (still regularly used) that you could take photos of and measure relevant voltages, etc - provided it doesn't damage my much loved amp.
I'll also look for any documentation that might still be in the box (if I can find the box).
Send me a DM for contact info.
Are you Sydney based? If so, I have a working Eidetic power and pre-amp (still regularly used) that you could take photos of and measure relevant voltages, etc - provided it doesn't damage my much loved amp.
I'll also look for any documentation that might still be in the box (if I can find the box).
Send me a DM for contact info.
BTW, here's a link to comments about the design considerations by the designer Greg Ball when he was around here: https://www.diyaudio.com/forums/solid-state/67151-eidetic-amplifierguru.html#post757534
Some good info, but no detailed schematic in case you are still looking for that.
Some good info, but no detailed schematic in case you are still looking for that.
Photos of Eidetic GB2b power amplifier
Finally was able to take my Eidetic GB2b power amp out of its cabinet and take some photos of its internals.
Photos cover external Front & Rear externally, and internally the Power Supply, Ohm Plug, Power Amp module and MOSFETS (two exposed). There are lots of components on the underside of the power amp module - and I'm not able or willing to dismantle these modules further.
Finally was able to take my Eidetic GB2b power amp out of its cabinet and take some photos of its internals.
Photos cover external Front & Rear externally, and internally the Power Supply, Ohm Plug, Power Amp module and MOSFETS (two exposed). There are lots of components on the underside of the power amp module - and I'm not able or willing to dismantle these modules further.
Attachments
Thanks for the pics, ranu, almost identical to my GB-1b, although I have upgrade the big caps alongside the mosfets to 100v Elna Silmic IIs and the input caps are now Silmic IIs as well. I also put a gold pin socket for the input IC and replaced all dodgy looking links on the boards with pure silver ones. I'm wondering if I can put OPA627s as the input ICs on the GB-1b? Or even drop in Sparkos Labs SS3602, or a Burson Vivid V6. Too much? Is there anything I might need to alter to run such upgraded opamps?
PS I am on the search to buy a GB-1a preamp to match the amplifier! Do you know of anyone around Sydney or elsewhere that might have one? I am also considering upgrading the power supply caps with higher end Nichicons, IF I can find the KG Gold versions.
Well, you learn something new every day 
Were they a later series of designs than the GB series? Still Mosfets? I'm very impressed with my refreshed GB1b, though struggling to find room for a soft start board, which it could do with. Fangin' to find a matching preamp. His design ethic to have such a pure midrange to reproduce pianos correctly (as one example) really paid off and my GB1b sounds just that, pure without being etched. Using an Elekit valve preamp and a pair of Sansui's TOTL 1968 SP300 speakers (36kg each and recapped) with horn mids and top end, was a revelatory joy. Such communication! Although the SP300's are well over 100dB efficiency, the 150W GB1b took control of those highly electrically damped 12" drivers and made them sing. I've since sold the high spec'd Elekit and am now on the hunt for the GB1a. Or 2a, although I have no idea of any extra benefits of it over the 1a if there are some.
Were they a later series of designs than the GB series? Still Mosfets? I'm very impressed with my refreshed GB1b, though struggling to find room for a soft start board, which it could do with. Fangin' to find a matching preamp. His design ethic to have such a pure midrange to reproduce pianos correctly (as one example) really paid off and my GB1b sounds just that, pure without being etched. Using an Elekit valve preamp and a pair of Sansui's TOTL 1968 SP300 speakers (36kg each and recapped) with horn mids and top end, was a revelatory joy. Such communication! Although the SP300's are well over 100dB efficiency, the 150W GB1b took control of those highly electrically damped 12" drivers and made them sing. I've since sold the high spec'd Elekit and am now on the hunt for the GB1a. Or 2a, although I have no idea of any extra benefits of it over the 1a if there are some.