I used VN2222 mosfets in mine. It's what I had on hand, similar ratings... good enough for switching a relay.
In stock at Mouser.
Cinco
I didn’t think the V Fet cases would ship this early but since my cases arrived I figured I should get building.
I just completed my Ship of Theseus amplifier and wanted to post pictures to encourage or inspire others to do the same.
A big thanks to @Mark Johnson for so generously making all these designs freely available to us.
I currently have it running with the Scourge front end as that is the only one I have built so far. I have the boards and parts for a number of the other front ends, which I will build in time. The amp has only been running for a day or two, so I can’t say anything specific other than it sounds fantastic. I was planning to install an LED on the front panel, but seeing how cool it looks glowing from the inside I think I may keep it that way for now.
I have some extra amp and front end boards from my order that I plan to make available before too long for those who are interested in building this but don’t want to order a bunch of extra boards.
I told myself that I didn’t need the Sony version, but after hearing how good this amp sounds I am tempted to pick up some of the parts from the swap meet and build that version too.
I just completed my Ship of Theseus amplifier and wanted to post pictures to encourage or inspire others to do the same.
A big thanks to @Mark Johnson for so generously making all these designs freely available to us.
I currently have it running with the Scourge front end as that is the only one I have built so far. I have the boards and parts for a number of the other front ends, which I will build in time. The amp has only been running for a day or two, so I can’t say anything specific other than it sounds fantastic. I was planning to install an LED on the front panel, but seeing how cool it looks glowing from the inside I think I may keep it that way for now.
I have some extra amp and front end boards from my order that I plan to make available before too long for those who are interested in building this but don’t want to order a bunch of extra boards.
I told myself that I didn’t need the Sony version, but after hearing how good this amp sounds I am tempted to pick up some of the parts from the swap meet and build that version too.
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A very lovely build @DataUnderlord !! Congratulations. It's actually pretty roomy inside when you don't need the aluminum T-bar for mounting TO-3 output transistors.
Good on ya.
Good on ya.
Thanks Mark!
The VFET cases are great to work with, and I am glad the store was able to make them available to the rest of us.
The VFET cases are great to work with, and I am glad the store was able to make them available to the rest of us.
Let me know when you're ready to build and audition a pair KittyHawk front ends. I have a feeling you'll really like those and, by accident, I happened to order too many components for them. So I've got spares. At least, I have them today; they may get purloined to try out a shiny new idea, down the road.
Mark,
Since you are talking about FE cards I actually had 2 questions. With the state of parts shortage I have become quite the hoarder. I have stacked up parts for Aleph J, Aleph 30, and M2X. I already have received one of the VFET chassis as I have 2 pair of the big Tokins, just waiting for Papa's output boards. I have been researching which FE boards to order pcbs and parts for. The easy button is Nimitz since I'll have 5 M2X input boards, Hornet and Bon Homme are also on the list. As they are all transformer based I was trying to pick one of the non transformer based FE to try.
Since you brought up KittyHawk, how does that transconductance FE compare to your original Dreadnaught which is also transconductance based? These where the 2 I was trying to flip a coin on trying.
Second, if you put a Ishikawa card with Toshiba Jfets into a Nimitz how close are you getting to Papa's original FE he sent with lottery VFETs? I was actually looking at the schematic just last night and it seems to this layperson they are pretty close in principle if not in exact execution.
Thanks as always for all the wonderful options you have created for us to play with.
Since you are talking about FE cards I actually had 2 questions. With the state of parts shortage I have become quite the hoarder. I have stacked up parts for Aleph J, Aleph 30, and M2X. I already have received one of the VFET chassis as I have 2 pair of the big Tokins, just waiting for Papa's output boards. I have been researching which FE boards to order pcbs and parts for. The easy button is Nimitz since I'll have 5 M2X input boards, Hornet and Bon Homme are also on the list. As they are all transformer based I was trying to pick one of the non transformer based FE to try.
Since you brought up KittyHawk, how does that transconductance FE compare to your original Dreadnaught which is also transconductance based? These where the 2 I was trying to flip a coin on trying.
Second, if you put a Ishikawa card with Toshiba Jfets into a Nimitz how close are you getting to Papa's original FE he sent with lottery VFETs? I was actually looking at the schematic just last night and it seems to this layperson they are pretty close in principle if not in exact execution.
Thanks as always for all the wonderful options you have created for us to play with.
Edit to above, I'm an idiot (or shouldn't post hastily while at work). While Dreadnaught and Kitty Hawk are both transconductance FE, Kitty Hawk still uses the Edcor. So, I guess my question should really be Dreadnaught, Marauder, or Lexington to get a taste of the non-Edcor FE boards.
That’s funny that you mention Kitty Hawk--I was just looking at that one. I recently built the IPS6 for my M2X, and it is by far the best sounding daughter card in my system, so I started looking through your new front end cards to see which one looked the most like IPS6 and came across Kitty Hawk. I know they aren’t the same circuit, but I can see many design similarities that make me think it could produce similar sonic results.
If you have boards or parts for Kitty Hawk you are willing to part with, I would love to build them and share my impressions here.
If you have boards or parts for Kitty Hawk you are willing to part with, I would love to build them and share my impressions here.
Possible substitution for ZTX857 in Lexington Boost circuit ?
Hi Mark, I have trouble sourcing a pair of ZTX857 that are used as part of the cap multiplier at the output of the JBOOST2 voltage booster in the Lexington cards. I would either have to buy from some eBay sellers or would incur tremendous shipping charges from the distributors that still seem to have a few.
So, would there be the possibility to substitute the ZTX857 with some other Zetex transistors ? Per their data sheet they seem to have two defining features: a) high voltage, and b) “very low saturation voltage”. I don’t know how important the latter is at this position. Could I substitute, with no or little performance hit, with ZTX851 (C-E voltage limit probably marginal at start-up), or with ZTX457 or even ZTX696B (these don’t have the low saturation voltage).
I know that in your BOM you called for a Zetex at this position, but don’t know enough to assess the specific requirements. Even a second TTC004B in this position doesn’t look too dissimilar from its parameters, other than the saturation voltage.
Thanks in advance for a pointer,
best regards, Claas
Hi Mark, I have trouble sourcing a pair of ZTX857 that are used as part of the cap multiplier at the output of the JBOOST2 voltage booster in the Lexington cards. I would either have to buy from some eBay sellers or would incur tremendous shipping charges from the distributors that still seem to have a few.
So, would there be the possibility to substitute the ZTX857 with some other Zetex transistors ? Per their data sheet they seem to have two defining features: a) high voltage, and b) “very low saturation voltage”. I don’t know how important the latter is at this position. Could I substitute, with no or little performance hit, with ZTX851 (C-E voltage limit probably marginal at start-up), or with ZTX457 or even ZTX696B (these don’t have the low saturation voltage).
I know that in your BOM you called for a Zetex at this position, but don’t know enough to assess the specific requirements. Even a second TTC004B in this position doesn’t look too dissimilar from its parameters, other than the saturation voltage.
Thanks in advance for a pointer,
best regards, Claas
So, I also grabbed some of the 2SJ18s. Had only planned to build the Tokin OS when available but couldn't pass up trying this OS with some real Sony VFETs. I already have the VFET chassis from the preorder so now its time to commit to some FE boards and place an order with the pcb fabs. Already have decided to do Nimitz, Hornet, and Bon Homme Richard. Real question is which of the transformerless FE boards to try. I have tried the search function and their seem to be some people that have done both Dreadnaught and Marauder. Haven't seen any comments comparing one to the other. Haven't seen any comment about Lexington yet. Anyone out there that built Marauder or Dreadnaught see something in Lexington that has them itching to give it a try? My bias for no good reason is to try Marauder based on the fact the store has boards and parts ready, and there seems to be the most comments about Marauder. But I am open to persuasion toward the others.
More difficult question, is there any set input impedance for the Front End boards? Why do I ask, I run a PL XP22 preamp balanced from source to amp with a 5M balanced run. 6L6 has previous suggested the best way to convert balanced to SE input signals at the amplifier level is to use a input transformer. When I was on the phone with the nice people at Cinemag ordering transformers for SissySIT they suggest their 15/15B for this problem.
https://cinemag.biz/line_input/PDF/CMLI-15-15B.pdf
Talking to them further and sharing the schematics for M2X and Sissy SIT they suggested changing out the Resistor tied across the SE input and ground from a 100K to 18K as the SE secondary of their transformer performs best loaded to 18K.
Snipets of M2X and SISSY input
The schematics on the VFET/Ship of Theseus FE boards seem to be much more variable and this newb can not get a good grasp on what is defining the input impedance.
Nimitz, guessing input R 330K?
Is the input R on Hornet and Marauder really 1 Meg? Seems like if it is there must be a good reason. If so, will I get in trouble switching for a 18K resistor?
More difficult question, is there any set input impedance for the Front End boards? Why do I ask, I run a PL XP22 preamp balanced from source to amp with a 5M balanced run. 6L6 has previous suggested the best way to convert balanced to SE input signals at the amplifier level is to use a input transformer. When I was on the phone with the nice people at Cinemag ordering transformers for SissySIT they suggest their 15/15B for this problem.
https://cinemag.biz/line_input/PDF/CMLI-15-15B.pdf
Talking to them further and sharing the schematics for M2X and Sissy SIT they suggested changing out the Resistor tied across the SE input and ground from a 100K to 18K as the SE secondary of their transformer performs best loaded to 18K.
Snipets of M2X and SISSY input
The schematics on the VFET/Ship of Theseus FE boards seem to be much more variable and this newb can not get a good grasp on what is defining the input impedance.
Nimitz, guessing input R 330K?
Is the input R on Hornet and Marauder really 1 Meg? Seems like if it is there must be a good reason. If so, will I get in trouble switching for a 18K resistor?
for first two pics, it is 100K, value of resistor, and there is nothin resistiove after
for rest of pics, no, I meed to see full sch to give you specific explanation
in these cases, circled resistor is just bleeder, Rin defined with lower values inside,after coupling cap
for rest of pics, no, I meed to see full sch to give you specific explanation
in these cases, circled resistor is just bleeder, Rin defined with lower values inside,after coupling cap
If I may shed my little light: 
The 100K just for DC reference, or 300K/1M is there to bleed the input capacitor in the last three instances; it is transparent in so far it is not loading the preceding stage.
The moment the preceding stage is a transformer (because that is what will happen if you have a bal-SE transformer #15), then that needs proper loading, i.e. 10K or often even a zobel. That of course will also load the output transformer of the preamp, but I expect that to be up to that task. It will not load the further input buffers.
The 100K just for DC reference, or 300K/1M is there to bleed the input capacitor in the last three instances; it is transparent in so far it is not loading the preceding stage.
The moment the preceding stage is a transformer (because that is what will happen if you have a bal-SE transformer #15), then that needs proper loading, i.e. 10K or often even a zobel. That of course will also load the output transformer of the preamp, but I expect that to be up to that task. It will not load the further input buffers.
in case I wanted to try vfet 3 (both 2sk60 and 2sj18) without the front-end, what load would the input transformer see? I need an input transformer as I use a pre with 100ohm balanced outputs ( and high voltage output )
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Excellent, math homework. Should also help me grasp the circuits better.
Will have to big into the M2X input boards and apply the same logic.
Will have to big into the M2X input boards and apply the same logic.
Be sure to read the application notes by Bill Whitlock, on the Jensen Transformers website. They talk about the Jensen philosophy (or call it stiff necked orthodoxy if you wish), for choosing the optimum loading network / Zobel network across the transformer secondary. But of course D.I.Y. means do it your way -- not necessarily Bill Whitlock's way.
You'll see that the Front Ends with an output transformer, use a secondary termination with one R and one C ... unlike the attached figure below.
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You'll see that the Front Ends with an output transformer, use a secondary termination with one R and one C ... unlike the attached figure below.
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