Scratch built 45/2A3 SET amp
- Thread starter Billfort
- Start date
Billfort
Addicted Member
Yes, I did all the design work in CAD, punched the stainless on a CNC turret press and had some parts brake-formed at work.
Still using this amp as my primary but as a 2A3 and with different coupling caps (AudioNote copper foil in oils). As much as I love the 45, 2A3 is more like it power-wise in the new room.
I've been incredibly busy at work so big scratch-built projects have really ground to a halt - if I have any time for hobbies now, I warm up the tubes, pour myself a scotch and put on some music.
I have been designing a pre-amp with separate PS case and a convertible top plate so I can try different circuits but I have made more progress on some 300B monoblocks. I wanted to try a pretty different layout with these to better isolate the AC and PS section from the amp stage while providing some flexibility for experimenting - the driver/power tube section is on replaceable plates so I can try 1 and 2 tube driver circuits (picture attached). I've got as far as completing punching of the stainless steel pieces and assembling the driver plates but finding time on a brake-press and in the wood shop has been a huge challenge, maybe when the weather gets a little warmer and work calms down a bit.
Still using this amp as my primary but as a 2A3 and with different coupling caps (AudioNote copper foil in oils). As much as I love the 45, 2A3 is more like it power-wise in the new room.
I've been incredibly busy at work so big scratch-built projects have really ground to a halt - if I have any time for hobbies now, I warm up the tubes, pour myself a scotch and put on some music.
I have been designing a pre-amp with separate PS case and a convertible top plate so I can try different circuits but I have made more progress on some 300B monoblocks. I wanted to try a pretty different layout with these to better isolate the AC and PS section from the amp stage while providing some flexibility for experimenting - the driver/power tube section is on replaceable plates so I can try 1 and 2 tube driver circuits (picture attached). I've got as far as completing punching of the stainless steel pieces and assembling the driver plates but finding time on a brake-press and in the wood shop has been a huge challenge, maybe when the weather gets a little warmer and work calms down a bit.
Attachments
Kegger
R.I.P. 1/12/1966 - 6/1/2017
Very nice! That is one sweet way to do up the chassis, mine are hack jobs as
I have no cash nor the tools for a nice layout like you are able to do, congrats.
I went the other way and started using spice simulation for the circuits while
concentrating on learning the inner workings of spice and the area of building
a better performing circuit. Figure since I didn't have cash I would start learning.
If you have anything anytime you'd like to "spice up" shoot it to me and I'll do em
up and ship them back to you. Makes the final circuit design much easier/faster to
achieve, as spice gets me pretty dam close and tweak for taste basically from there.
Anyways maybe sometime (when we both get time, if that would ever happen)
we could collaborate on a project together, I've been working push pull, you've
been working set maybe put 2 heads together and come up with something cool.
Sometime down the road I've got a pair of citation V outputs that they have no UL taps
so I've been toying with the idea of a larger push pull triode amp with them, well maybe.
See yu at the fest! You gettin a room?
I have no cash nor the tools for a nice layout like you are able to do, congrats.
I went the other way and started using spice simulation for the circuits while
concentrating on learning the inner workings of spice and the area of building
a better performing circuit. Figure since I didn't have cash I would start learning.
If you have anything anytime you'd like to "spice up" shoot it to me and I'll do em
up and ship them back to you. Makes the final circuit design much easier/faster to
achieve, as spice gets me pretty dam close and tweak for taste basically from there.
Anyways maybe sometime (when we both get time, if that would ever happen)
we could collaborate on a project together, I've been working push pull, you've
been working set maybe put 2 heads together and come up with something cool.
Sometime down the road I've got a pair of citation V outputs that they have no UL taps
so I've been toying with the idea of a larger push pull triode amp with them, well maybe.
See yu at the fest! You gettin a room?
BillEpstein
Active Member
Teflon tube sockets
Too late now 'cause you already cut the holes but DIYhifisupply has really nice teflons for $19 apiece. Grip really well and have plenty of material to go up and through an 1/8" top plate. I used'm in my 45 amp. The UX-4's are undersized so you have to build with them in mind. The novals and octals are standard size.
Too late now 'cause you already cut the holes but DIYhifisupply has really nice teflons for $19 apiece. Grip really well and have plenty of material to go up and through an 1/8" top plate. I used'm in my 45 amp. The UX-4's are undersized so you have to build with them in mind. The novals and octals are standard size.
soundmotor
super modified
Billfort said:
I finally spied this thread.
Wow!
Beautiful work.
Billfort
Addicted Member
Thanks soundmotor; it was a pretty satisfying build and I learned a lot with this one.
I noticed those Teflon sockets Bill and might try them down the road. I have some really well built old stock sockets to use on the 300B build but they are easy enough to change - I've started mounting all the tubes on rubber mounted sub-assembly plates and different sizes are just a few minutes away on the turret press.
Thanks for the offer to do up some circuit sims kegger - I will be taking you up on that. I'd like to look at the 300B amp and a few pre-amp circuits in particular. I've been sticking to circuits I've heard and liked so far but want to experiment a little with PS design and try a bunch of things for the pre-amp.
A collaboration project might be something I'd consider so lets talk at the fest but I did a 'group build' project once before with mixed results for me - I wasn't too comfortable with the 'designed my committee' approach.
I thought about a fest room but I'd want to bring most everything as my system is really all about how all the bits go together and my equipment doesn't travel well. I'd need something like a cube van and then there is the major hassle of the border. I think I'm pretty much resigned to the fact that if someone wants to hear my crap it means a trip to Toronto.
I noticed those Teflon sockets Bill and might try them down the road. I have some really well built old stock sockets to use on the 300B build but they are easy enough to change - I've started mounting all the tubes on rubber mounted sub-assembly plates and different sizes are just a few minutes away on the turret press.
Thanks for the offer to do up some circuit sims kegger - I will be taking you up on that. I'd like to look at the 300B amp and a few pre-amp circuits in particular. I've been sticking to circuits I've heard and liked so far but want to experiment a little with PS design and try a bunch of things for the pre-amp.
A collaboration project might be something I'd consider so lets talk at the fest but I did a 'group build' project once before with mixed results for me - I wasn't too comfortable with the 'designed my committee' approach.
I thought about a fest room but I'd want to bring most everything as my system is really all about how all the bits go together and my equipment doesn't travel well. I'd need something like a cube van and then there is the major hassle of the border. I think I'm pretty much resigned to the fact that if someone wants to hear my crap it means a trip to Toronto.
dnewma04
The Healer
I recently had a Tubelab SimpleSE board and a pair of 45s land in my lap, it will be interesting to build something ultra low powered to make things really inconvenient on myself. My original search was for substitutes for the 417A, as they don't appear to be tubes that fly under the radar like they did 5 years ago. C3M is a loctal pentode, if i am remember correctly, I've read a little about it in my loctal searches. I am almost considering using some sort of sharp cutoff pentode strapped as a triode in place of the 417A.
BTW, the curves of the C3M look nice as a pentode or triode strapped.
BTW, the curves of the C3M look nice as a pentode or triode strapped.
Billfort
Addicted Member
If you have the speakers to let them shine (and that's a VERY big 'if'), it doesn't get any better than the 45 IMHO. If I ever get a pair built that is >103db efficient with a smooth impedance curve and that works in a regular size listening room, I'll plug the 45s in and use this amp that way real quick.
Don't see it happening anytime soon though.
The reason I mention the C3M is that I've heard it a few times driving a 300B and it's probably the best I ever heard the 300B tube (in an amp using Electra-Print outputs and some original WE 300Bs). So far, I prefer the 2A3 to most 300B amps but that C3M>300B with E-P iron, I just have to get a pair downstairs for an extended listen because a 7wpc 300B amp is probably better suited to the Altecs I use.
2A3 is going to be a pretty hard thing to better for me though, I do like it.
Don't see it happening anytime soon though.
The reason I mention the C3M is that I've heard it a few times driving a 300B and it's probably the best I ever heard the 300B tube (in an amp using Electra-Print outputs and some original WE 300Bs). So far, I prefer the 2A3 to most 300B amps but that C3M>300B with E-P iron, I just have to get a pair downstairs for an extended listen because a 7wpc 300B amp is probably better suited to the Altecs I use.
2A3 is going to be a pretty hard thing to better for me though, I do like it.
Tell us more about your new project.
Redboy
a few good watts
Hey Bill, I saw you mention in another thread that you just brought this amp back into play, and thought it deserved a revival of sorts. It's one of the nicest DIY efforts here and more people ought to see it...
Have you made any changes or updates to it recently?
EDIT: ...and ya know, some of us would really love to see a Billfort thread in the Member's Systems forum...
Have you made any changes or updates to it recently?
EDIT: ...and ya know, some of us would really love to see a Billfort thread in the Member's Systems forum...
Billfort
Addicted Member
Hey Nate, thanks for the compliment. Yes, just put this amp back in my system and realized again that I really ought to stop taking it out.
I just love 2A3s and it's funny, when I messed with 300Bs I just couldn't leave them alone and was constantly changing something but this amp, aside from coupling cap changes, hasn't changed at all since I bypassed the level pots shortly after I built it. With 417As as drivers I don't even get to mess with tube rolling too much; WE drivers, Mullard GZ37 slow start rectifier that I just love and some RCA 2A3s to sometimes swap in for Shuguang 2A3c and I'm happy.
Yes, do have to put together a thread on my system...someday...
I just love 2A3s and it's funny, when I messed with 300Bs I just couldn't leave them alone and was constantly changing something but this amp, aside from coupling cap changes, hasn't changed at all since I bypassed the level pots shortly after I built it. With 417As as drivers I don't even get to mess with tube rolling too much; WE drivers, Mullard GZ37 slow start rectifier that I just love and some RCA 2A3s to sometimes swap in for Shuguang 2A3c and I'm happy.
Yes, do have to put together a thread on my system...someday...
goldleaf
Super Member
Hey Nate, thanks for the compliment. Yes, just put this amp back in my system and realized again that I really ought to stop taking it out.
I just love 2A3s and it's funny, when I messed with 300Bs I just couldn't leave them alone and was constantly changing something but this amp, aside from coupling cap changes, hasn't changed at all since I bypassed the level pots shortly after I built it. With 417As as drivers I don't even get to mess with tube rolling too much; WE drivers, Mullard GZ37 slow start rectifier that I just love and some RCA 2A3s to sometimes swap in for Shuguang 2A3c and I'm happy.
Yes, do have to put together a thread on my system...someday...
Thanks for reviving this thread Nate. I wasn't around then and this is definitely a nice example of a fine amp.
Bill, would you change anything now?
Is there a schematic of the amp somewhere?
Billfort
Addicted Member
Can’t find my old schematic, I should re-draw it sometime, it’s a very simple circuit.
If doing it again, I wouldn’t include the level pots (even less is more) as they were intended to work in conjunction with passive line-level filters in front of this amp, driving the horns on my Altec 604s. I built 2 of these chassis to do the bi-amping thing but found I like the Markwart passive crossover enough with this simple 2A3 circuit that I never bothered – traded the second one away to a friend.
I’ve thought about other driver tubes, maybe direct coupled, possibly splitting the PS after the rectifier, maybe oil PS caps – but then all that would be a different amp in a different chassis, and this one just works for me as-is. I hope to try some new stuff with the bones of my 300B adventures but this amp will remain as my ‘target’ because it’s a very comfortable yardstick.
One thing this amp taught me (along with several 300B builds) is that a novice tube hacker can turn out a nice sounding 2A3, but getting a 300B to the same level is a LOT harder. This amp is why I always say that if you want to mess with this low power SET stuff, start with the speakers and aim very high (efficiency wise) – 2A3 is hard to beat.
If doing it again, I wouldn’t include the level pots (even less is more
) as they were intended to work in conjunction with passive line-level filters in front of this amp, driving the horns on my Altec 604s. I built 2 of these chassis to do the bi-amping thing but found I like the Markwart passive crossover enough with this simple 2A3 circuit that I never bothered – traded the second one away to a friend.I’ve thought about other driver tubes, maybe direct coupled, possibly splitting the PS after the rectifier, maybe oil PS caps – but then all that would be a different amp in a different chassis, and this one just works for me as-is. I hope to try some new stuff with the bones of my 300B adventures but this amp will remain as my ‘target’ because it’s a very comfortable yardstick.
One thing this amp taught me (along with several 300B builds) is that a novice tube hacker can turn out a nice sounding 2A3, but getting a 300B to the same level is a LOT harder. This amp is why I always say that if you want to mess with this low power SET stuff, start with the speakers and aim very high (efficiency wise) – 2A3 is hard to beat.
Hi 'Billfort',
I am a Dutch newbee and I am aslo planning to build an amp with a 417a and the 45.
I can buid and solder the stuff butt I am still learning to calculate on tubes.
Is it posibele you send me your schematic so I can copy your skills into my new amp?
Kind regrads form Holland
I am a Dutch newbee and I am aslo planning to build an amp with a 417a and the 45.
I can buid and solder the stuff butt I am still learning to calculate on tubes.
Is it posibele you send me your schematic so I can copy your skills into my new amp?
Kind regrads form Holland