Those who have been following my post will know that i am trying to build a tube amp for almost 2 years now but could never finalize any design. I had even thought of re-building my current 300B SET amplifier with better parts and a new chassis, but gave away the thought because it was getting pretty expensive and moreover having the same 3 stage capacitor coupled ckt with boutique components may not be a very high change from what i am currently hearing. I scanned many designs over the past two years and with tubes like 2A3, EL34, 45, 203D, 00B and the like but never could finalize anything. I later decided to go with the 'Directly Coupled' type of tube amplifier and came across the Loftin White schematic but did not pursue that further. Some time later FM @yogibear shared with me a EL34 SET DC design which had potential, but even that could not materalize.
Earlier this year, i thought of buying a readymade amplifier and came across a Japanese brand by the name "Softone" who made some 300B tube which was a hybrid design with direct coupling. This was a reasonably priced setup ($850/- + shipping + CD) but by the time i could decide the C-19 issue started and the rest is history. I also thought of getting their EL34 or KT88 class A push-pull design which was also very nice and hybrid design, but again there was a increase in CD and related c-19 shipping issue which put the plan in the back seat.
In my search, i came across a gentleman by the name of Jeff Medwin, who usually comment about various designs in forums and i got in touch with him through a PM and we started discussing about various possibilities. This was in around mid April and after many discussion i had finalized his design around last month.
What i was using till now - 300B, SET, DHT, DC heated filament, 3 stages (pre-driver + driver + output) with capacitor coupling stages.
Power supply - SS diodes with C-L-C filtering, output stage is EI audio transformer, power supply transformer is EI. If you have read my earlier amplifier modification post, i have made many modifications to this amplifier with changes in all resistors, capacitors, driver and input tubes, wires etc. The only components that are still probably retained are the power and output transformers, the volume control and the Chassis.
What i wanted in my new amplifier is - IDH ( indirectly heating) AC heating type, only 2 stage of amplification (driver + output), Directly coupled sections. Power supply uses the LES(low energy storage) type of design with L-C-L-C filtering. The LES is a proprietary design of Dennis Fraker (Jeff Medwin's mentor) of serious stereo fame who have pioneered this design almost 3 decades ago. If you search other international forums you might find this design very very controversial and gets all the bad name of being a very poor design. But Jeff handles all the bad press with wit and confidence. Most FMs who claim the poor design have neither used or heard his amplifier and come to conclusion which is quite normal in this hobby. That's when i decided to build this particular amplifier and discover what the "fuss" is about his power supply that gets trolled so much. The discussion in the forum gets so nasty to the extend that Jeff has been "Banned" in atleast 3 forums which i know of. But again who cares if you have many followers and admirers of your design. Anyways.
Jeff is also helping me source some critical components at a very attractive price which i probably could not have sourced at that price and i thank him for that for the effort. I had ordered some components directly from mouser.in which i have received early this week. If all my supplies arrive on time without the c-19 posted risk, almost 90% of the components should be received before end of this month, after which i shall plan to assemble. The output transformers will be procured from "Softone" which is a R-core type. The EMS Japan currently don't ship to India/ US and 83 other countries and this is not going to change soon. I am borrowing a Delta audio output transformer from FM @Beast_of_burden in the interim period for my testing. The power transformers are ordered from Silchar Transformers (a big thankyou to FM @sadik for helping me with this).
I have made a rough design of the chassis which i will be building with teak wood + brass sheets. Chassis parts have been ordered from theaudiocrafts.com. The entire amplifier will take around 4 to 6 months to complete and am expecting the mono-blocks to be ready by Jan-2021 to be fully ready and functional if all turns out well.
Thanks for looking.
This is what i received 30% of components from mouser.com earlier this week.
Earlier this year, i thought of buying a readymade amplifier and came across a Japanese brand by the name "Softone" who made some 300B tube which was a hybrid design with direct coupling. This was a reasonably priced setup ($850/- + shipping + CD) but by the time i could decide the C-19 issue started and the rest is history. I also thought of getting their EL34 or KT88 class A push-pull design which was also very nice and hybrid design, but again there was a increase in CD and related c-19 shipping issue which put the plan in the back seat.
In my search, i came across a gentleman by the name of Jeff Medwin, who usually comment about various designs in forums and i got in touch with him through a PM and we started discussing about various possibilities. This was in around mid April and after many discussion i had finalized his design around last month.
What i was using till now - 300B, SET, DHT, DC heated filament, 3 stages (pre-driver + driver + output) with capacitor coupling stages.
Power supply - SS diodes with C-L-C filtering, output stage is EI audio transformer, power supply transformer is EI. If you have read my earlier amplifier modification post, i have made many modifications to this amplifier with changes in all resistors, capacitors, driver and input tubes, wires etc. The only components that are still probably retained are the power and output transformers, the volume control and the Chassis.
What i wanted in my new amplifier is - IDH ( indirectly heating) AC heating type, only 2 stage of amplification (driver + output), Directly coupled sections. Power supply uses the LES(low energy storage) type of design with L-C-L-C filtering. The LES is a proprietary design of Dennis Fraker (Jeff Medwin's mentor) of serious stereo fame who have pioneered this design almost 3 decades ago. If you search other international forums you might find this design very very controversial and gets all the bad name of being a very poor design. But Jeff handles all the bad press with wit and confidence. Most FMs who claim the poor design have neither used or heard his amplifier and come to conclusion which is quite normal in this hobby. That's when i decided to build this particular amplifier and discover what the "fuss" is about his power supply that gets trolled so much. The discussion in the forum gets so nasty to the extend that Jeff has been "Banned" in atleast 3 forums which i know of. But again who cares if you have many followers and admirers of your design. Anyways.
Jeff is also helping me source some critical components at a very attractive price which i probably could not have sourced at that price and i thank him for that for the effort. I had ordered some components directly from mouser.in which i have received early this week. If all my supplies arrive on time without the c-19 posted risk, almost 90% of the components should be received before end of this month, after which i shall plan to assemble. The output transformers will be procured from "Softone" which is a R-core type. The EMS Japan currently don't ship to India/ US and 83 other countries and this is not going to change soon. I am borrowing a Delta audio output transformer from FM @Beast_of_burden in the interim period for my testing. The power transformers are ordered from Silchar Transformers (a big thankyou to FM @sadik for helping me with this).
I have made a rough design of the chassis which i will be building with teak wood + brass sheets. Chassis parts have been ordered from theaudiocrafts.com. The entire amplifier will take around 4 to 6 months to complete and am expecting the mono-blocks to be ready by Jan-2021 to be fully ready and functional if all turns out well.
Thanks for looking.
This is what i received 30% of components from mouser.com earlier this week.
