Attached is the document detailing the DIY Sony VFET OS2 output stages.
These are revisions of the previous efforts for the N channel 2SK82 and P channel 2SJ28 design but intended to accommodate people who have those VFET or other Sony VFET transistors, notably 2SK60 and 2SJ18 or even other power Fets in TO-3 packages, including Mosfets.
The biggest differences are in the current sources. Where the originals used constant current sources, for the P channel design we have a mu follower and for the N channel a novel variation. Both of these are constant current for DC, but can be adjusted to supply a percentage of the output current in support of the smaller VFET chips.
The diyAudio store will be making its announcement shortly with an initial stock of both output stage kits, which are compatible with original and new kits for front ends and power supply filters, especially Mark Johnson's efforts. I have been asked to assure you that there will be plenty to go around, no problems, and even if you don't have the VFETs you will be able to make Mosfet versions for TO-3 and also TO-247 plastic packages, so don't fret. Also the ever benevolent 6L6 has agreed to do build guides.
So here we go. Stay in line, no crowding....
These are revisions of the previous efforts for the N channel 2SK82 and P channel 2SJ28 design but intended to accommodate people who have those VFET or other Sony VFET transistors, notably 2SK60 and 2SJ18 or even other power Fets in TO-3 packages, including Mosfets.
The biggest differences are in the current sources. Where the originals used constant current sources, for the P channel design we have a mu follower and for the N channel a novel variation. Both of these are constant current for DC, but can be adjusted to supply a percentage of the output current in support of the smaller VFET chips.
The diyAudio store will be making its announcement shortly with an initial stock of both output stage kits, which are compatible with original and new kits for front ends and power supply filters, especially Mark Johnson's efforts. I have been asked to assure you that there will be plenty to go around, no problems, and even if you don't have the VFETs you will be able to make Mosfet versions for TO-3 and also TO-247 plastic packages, so don't fret. Also the ever benevolent 6L6 has agreed to do build guides.
So here we go. Stay in line, no crowding....
Sir Nelson Pass,
I am melting. Your generosity has no bounds. Thank you so very much!
Best,
Anano.
I am melting. Your generosity has no bounds. Thank you so very much!
Best,
Anano.
The Switch Mode Power Supply which Nelson has chosen for the VFET amplifier family, is the Mean Well GST160A36-R7B. It is sold by lots of electronics distributor houses, such as Mouser and DigiKey, and is also available from the diyAudio Store (sales link). Since it's a Switch Mode power supply, builders almost always choose to install a noise-removing filter between the supply and the amplifier.
One possibility is to install a PAIR of the PO89ZB filter boards sold in the Store (here). One board per channel, which lets you stay comfortably and safely below the 3 ampere max current spec of the filter. Each channel draws less than 2 amperes, and 2 is certainly smaller than the 3 ampere max spec.
Another possibility is to install a single THESEUS-PSFILT board, from the mechanically and electrically compatible Ship Of Theseus project. THESEUS-PSFILT contains two SMPS filters on a single PCB, one for Left and the other for Right, providing additional channel isolation and separation. THESEUS-PSFILT also includes a fancy turn-on / turn-off "thump" suppression relay, similar to (but more elaborate than) the Nchannel VFET amp's filter, sold last year by lottery. Here are the schematics and PCB manufacturing Gerber files for the PSFILT: (link)
There are also a dozen Front End cards -- four in the Store, and bunches more in the Theseus project -- but I suspect builders of OS2 may be drawn to the one called "Pequod" because that is the simplest circuit, with the fewest parts and the lowest total parts cost. It is the cheapest option even though you have to buy Edcor transformers either from the factory in New Mexico USA, or from Don-Audio in Europe (Germany).
One possibility is to install a PAIR of the PO89ZB filter boards sold in the Store (here). One board per channel, which lets you stay comfortably and safely below the 3 ampere max current spec of the filter. Each channel draws less than 2 amperes, and 2 is certainly smaller than the 3 ampere max spec.
Another possibility is to install a single THESEUS-PSFILT board, from the mechanically and electrically compatible Ship Of Theseus project. THESEUS-PSFILT contains two SMPS filters on a single PCB, one for Left and the other for Right, providing additional channel isolation and separation. THESEUS-PSFILT also includes a fancy turn-on / turn-off "thump" suppression relay, similar to (but more elaborate than) the Nchannel VFET amp's filter, sold last year by lottery. Here are the schematics and PCB manufacturing Gerber files for the PSFILT: (link)
There are also a dozen Front End cards -- four in the Store, and bunches more in the Theseus project -- but I suspect builders of OS2 may be drawn to the one called "Pequod" because that is the simplest circuit, with the fewest parts and the lowest total parts cost. It is the cheapest option even though you have to buy Edcor transformers either from the factory in New Mexico USA, or from Don-Audio in Europe (Germany).
As always, I am looking forward to seeing so many incredible amplifiers in the hands of the builders!
I am also interested in trying some of the Mark Johnson input stages… there are so many to choose from it’s an embarrassment of riches. What a wonderful place this is! 🙂 🙂 🙂
I am also interested in trying some of the Mark Johnson input stages… there are so many to choose from it’s an embarrassment of riches. What a wonderful place this is! 🙂 🙂 🙂
Thank you so much Nelson, My wife likes and is intrigue by your DIY VFET push pull. She's always using it more frequent than me.
Need to watch the store before these kits quickly rans outs.
Need to watch the store before these kits quickly rans outs.
I love the trick of changing the apparent load on the VFET. So many things to learn.
