SE design questions before I start my project

[wicked1]

Hello,
Quick intro - I got interested in electronics by building an analog modular synthesizer. I had to learn a lot of electrical engineering to complete that beast (well it will never be complete! That's the problem w/ modulars..).
I rescued an old 50's magnatone amp out of the garbage a couple of months ago, and repaired it. After seeing how simple the circuit is, I quickly became obsessed w/ the idea of building a tube hifi amp for my home. I've done a LOT of reading over the past couple of months now, and am unfortunately past the point of knowing what I want to do and back to being thoroughly confused. (I'm sure you've all been here... learning about things on the internet is a difficult task w/ all the conflicting opinions, and the realization that 1/2 of what you're reading is 15 years old, and the other half is new).
So, I know this question has been answered but I've got to ask again to see what current opinions are.



I'm building a single sided 2a3 amp. (don't need a lot of power)
The 2001 schematic at Angela got me started, and was going to be the basis of my project.
Now I'm sort of confused about the input stage, and of course about the output.

Input possibilities are the basic single tube dual triode. (easy)
or
A srpp design like the kismet3 (He seems very excited about it, but I read posts in this forum dismissing the idea, saying it's better to stick to something like the Angela schematic)
Then I'm also wondering if I need a preamp. I'd like the input to have enough gain that I will not. I'll (sadly) mostly be playing digital music from a high end music production sound card. I do have good turntables, but the truth is, most of my music is on the computer now days. The point to that is that I guess the sound card could be considered a "pre amp". (let me know if im on the right track in thinking that)

Output... I'm just wondering what people currently think about going w/ a parallel feed output (like the parafeed magnaquest, EXO) or a more conventional s.e. transformer (lets say the other magnaquest DS or Hammond, james, etc, etc.)
So.. that's not meant to be a comparison of transformers, but a comparison of output topologies.

I'll also mention that since I am using digital music, I wouldn't mind the amp adding a little color to the music.
My music interests are all over the place from classical to classic rock to indy to electronic of all kinds.
My existing amp is an early 90's digital tuner/amp combo, so I'd imagine anything will be better than it!

Well. Thanks for any advice. I thought I knew what I was going to build, but I can't seem to get past all the conflicting and possibly outdated info at this point.

[Miles Prower]

Originally posted by wicked1
After seeing how simple the circuit is, I quickly became obsessed w/ the idea of building a tube hifi amp for my home.

See? That's what you get for hanging around here.

Input possibilities are the basic single tube dual triode. (easy)
or
A srpp design like the kismet3 (He seems very excited about it, but I read posts in this forum dismissing the idea, saying it's better to stick to something like the Angela schematic)

I would stick with "simple" here. I don't like the SRPP since this topology is balanced for the one specific load impedance where the source and sink currents are equal. Otherwise, it goes out of balance and the distortion rises. If you're operating it for the voltage gain, it might be OK. (In that case, a mu-stage would be better anyway.)

Then I'm also wondering if I need a preamp. I'd like the input to have enough gain that I will not. I'll (sadly) mostly be playing digital music from a high end music production sound card. I do have good turntables, but the truth is, most of my music is on the computer now days. The point to that is that I guess the sound card could be considered a "pre amp". (let me know if im on the right track in thinking that)

Better to design for an input sensitivity ~1.0Vrms. Most CD players, tape decks, sound cards, will run that nicely. Use an outboard preamp for the turntable.

Output... I'm just wondering what people currently think about going w/ a parallel feed output (like the parafeed magnaquest, EXO) or a more conventional s.e. transformer (lets say the other magnaquest DS or Hammond, james, etc, etc.)
So.. that's not meant to be a comparison of transformers, but a comparison of output topologies.

It's all good. The most important thing here is component quality, especially if there is no gNFB. When it comes to output "iron", this is not the place for cost-cutting if you want the best sonics.

[Brion55]

Just curious, what kind of modular synth did you build? I worked for PAIA electronics many years ago - they made modular synth kits back then. Have thought about bulding a small Minimoog type synth to play around with.

[SHiFTY]

The 2001 edition schematic with 6SL7 cathode follower sounds pretty good. I have built that, the 6SL7 SRPP version, a single triode driver, and a 6SN7 cascade (300B driver).

Of all of these, I preferred the 2001 edition- better bass andmore power output...

[JandG]

I just did the JE Labs 45, simple version. I used James 6123 for OT & entire project exceded all expectations. It beats my 300B PP amp in superior sonics. I would go the 6123 route if were you also, they are a wonderfull sounding OT for about $ 225.00 for the pair. Only thing I changed was the use of PPcaps, aka Solen's in PS & that was it.All op-points were spot on 1st go around & has been playing music every since. Extremely low hum on 99db speakers. I can see you selling all your non tube amps in near future........

[truenorth]

Well. Thanks for any advice. I thought I knew what I was going to build, but I can't seem to get past all the conflicting and possibly outdated info at this point.

I'm in a similar situation as you, although, I have narrowed my driver (300B), power (5U4G), and OPT(James)... Now, I'm struggling with input stage. My current thought is to start with Angela/Walton circuit and expand into Aikido using 6SN7s... or should I just go with Aikido.

Thouhghts?

[wicked1]

Originally posted by Brion55
Just curious, what kind of modular synth did you build? I worked for PAIA electronics many years ago - they made modular synth kits back then. Have thought about bulding a small Minimoog type synth to play around with.

It all started w/ a Paia kit! then it grew and grew from there. I learned a lot from that point and eventually started making my own circuits and PCB's. Here's a link to my website about it. The site is incomplete and outdated (it's grown a lot since I made it) but you can get the idea.
www.sdiy.org/wicked1

Originally posted by JandG
I just did the JE Labs 45, simple version. I used James 6123 for OT & entire project exceded all expectations. It beats my 300B PP amp in superior sonics. I would go the 6123 route if were you also, they are a wonderfull sounding OT for about $ 225.00 for the pair. Only thing I changed was the use of PPcaps, aka Solen's in PS & that was it.All op-points were spot on 1st go around & has been playing music every since. Extremely low hum on 99db speakers. I can see you selling all your non tube amps in near future........

Where'd you get the James? The 123 isn't listed on euphonia, and neither them, or a couple of places in Asia have replied to my emails over the past couple of weeks.

Thanks everyone!!!! I almost expected to get flamed for asking those questions!

I'd still like to hear a little more about parallel feed vs standard S.E. output if there is more to it. I'd probably go between the James 6123, hammond 1600 series(not the best, but seems to be a really good value.. especially since no one seems to want to sell me a James), or the magnaquest parafeeds. If the parafeeds don't make that much of a difference, I guess I'll avoid them, as that way I can stick to the Angela schematic for my first build.

thanks again

[JandG]

I think Euphonia is out of stock & awaiting the 6123 re-stock. E-mail them to see when they will arrive. I would ride it out if only a few weeks out, & source your other parts for build.

[wicked1]

THL in Taiwan finally just got back to me. Their price was only slightly less than what Euphonia is asking (but there is a note on euphonia's website saying they might have to increase prices). I sent Euphonia another email direct this time, instead of using the web form. Hopefully that will get to them.

[kmtang]

Hey,

I have built a 45 SE tube amp with LL1620AM OPT. It sounds extremely good indeed.

I would highly recommend you would spend some more money in the OPT which will be worth for your investment.

The Lundahl Amorphous C-core provides very wide bandwidth from low to high. The music is just breathing out from the speakers.

I just tested my 45 amp with B&W801 Speakers. Wowhhhh..


JOhnny