2a3 / 45 amp build opinions

[MechE98]

I've been doing a serious amount of research on SET 2a3 and 45 amps, specifically the Rankin 2a3 Baby Ongaku and 45 Bugle. It seems those that have built them have no complaints with either design. I had put together a parts list and was going to start buying parts to build a 45 Bugle based on user feedback when I discovered the Brook 12a, and a few notes around the web from a few clone builders.

I would appreciate your thoughts and comments, as well as any personal build and listening experience on these amps. I know the topologies differ between the Brook and Rankin 2a3, and it's not apples to apples. I would be running any of the above with rebuilt Heresy I's with Crites tweeters and updated crossovers.

Thanks for your opinions

 

[TerryO]

I've been doing a serious amount of research on SET 2a3 and 45 amps, specifically the Rankin 2a3 Baby Ongaku and 45 Bugle. It seems those that have built them have no complaints with either design. I had put together a parts list and was going to start buying parts to build a 45 Bugle based on user feedback when I discovered the Brook 12a, and a few notes around the web from a few clone builders.

I would appreciate your thoughts and comments, as well as any personal build and listening experience on these amps. I know the topologies differ between the Brook and Rankin 2a3, and it's not apples to apples. I would be running any of the above with rebuilt Heresy I's with Crites tweeters and updated crossovers.

Thanks for your opinions

Using those speakers, I believe that an amp based on a 45 Triode would be an unsatisfactory combination. For that matter, I'm not even sure that a 2A3 would be enough in an average or larger room, but I may be mistaken. Both tubes can produce some very nice sound with the right speakers, but I'm just not sure if yours are the right ones.

Best Regards,
TerryO

 

[jaymanaa]

Using those speakers, I believe that an amp based on a 45 Triode would be an unsatisfactory combination. For that matter, I'm not even sure that a 2A3 would be enough in an average or larger room, but I may be mistaken. Both tubes can produce some very nice sound with the right speakers, but I'm just not sure if yours are the right ones.

Best Regards,
TerryO

Wow, is there a huge difference between the 1s and the 2s? My Heresy 2s get plenty loud on my 2 watt 2A3 amp.:scratch2:

 

[battradio]

I'm using a simplified version of the Brook 12A , with PP 6B4's , a 6B4 is a 6 volt 2A3 for the most part . The output transformers really make a difference with triodes so get the best ones you can and with 8 watts it will hold it own with most speakers and rooms .

 

[TerryO]

Wow, is there a huge difference between the 1s and the 2s? My Heresy 2s get plenty loud on my 2 watt 2A3 amp.:scratch2:

It appears that my ignorance (or old age) is showing. If they are efficient enough, then all is good. The 2a3's and 45's are great sounding tubes (so is the 10 if you can ever find a pair) but you're very close to nearfield or horn territory at that point. I suppose you might be tempted to cheat a little, like this example:

It's a 45 SET Input Stage driving a Class A SS Output Stage, for approximately 17 or 18 watts output.

Best Regards,
TerryO

 

[GAryB]

Rankin 2A3

I've used the Rankin / Baby Ongaku 2A3 with Reference 3A mm de capo i speakers, which are rated at an efficiency of 92db/W, so I think the amp should do very well with the Klipsch Heresy. The Klipsch is definitely higher sensitivty, so they'd be idling compared to my speakers. My room is modest in size, but I don't get the sense that I'm running out of steam with the 2A3 running single ended.
---Gary

 

[TerryO]

I've used the Rankin / Baby Ongaku 2A3 with Reference 3A mm de capo i speakers, which are rated at an efficiency of 92db/W, so I think the amp should do very well with the Klipsch Heresy. The Klipsch is definitely higher sensitivty, so they'd be idling compared to my speakers. My room is modest in size, but I don't get the sense that I'm running out of steam with the 2A3 running single ended.
---Gary

About 10 years back we had to borrow a pair of Doc Bottlehead's 2A3 amps for the room at VSAC, when our amp developed a problem. The Adire 10.2 speakers were rated 94 dB/W/M and we had a real problem getting enough volume out of them in that Hotel Room. On a loud passage, you could tell the amps were straining.

YMMV,
TerryO

 

[jaymanaa]

The circuit in this one is somewhat complex and influenced by Asian Hi Fi. I typically run RCA JAN 2A3s and HP 6DJ8s up front. I can run it direct coupled for a couple watts, or Mosfet coupled for around 3.

 

[mhardy6647]

Triple-digit sensitivity is certainly better with SE 2A3.
I thought my Paramours did fine with a pair of 1974-era Klipsch Cornwalls (ca. 98 dB sensitive @ 1 watt @ 1 meter), FWIW.
Currently using Altec Duplexes (ca. 102 dB) with the JE/Angela "Simple 2A3" and the combination's dandy - relative to my ears and tastes - in a ca. 24 x 26 foot room.
I'd opine (with some empirical experience, but not too much) that 100+ dB is pretty much essential for an SE 45 amp.

It does depend on the benign-ness of the load (i.e., the impedance curve of the speakers), the room size, and the type of music (not to mention how loud) one prefers.

 

[Billfort]

I'll agree with Mr. Hardy here. I use 100db efficient speakers in a somewhat regular sized room and go back and forth from 45 to 2A3 - as recently as last night. I love 45s, but they are just not quite enough for me on these speakers - 2A3 is more like it, especially if you expect decent dynamics and bass and listen to a wide range of music.

Actually, I consider 2A3 borderline on 100db eff. speakers and 300Bs at 6w are probably more like it, but I can't get by how good 2A3s sound.

Just my experience.

 

[jaymanaa]

I'll agree with Mr. Hardy here. I use 100db efficient speakers in a somewhat regular sized room and go back and forth from 45 to 2A3 - as recently as last night. I love 45s, but they are just not quite enough for me on these speakers - 2A3 is more like it, especially if you expect decent dynamics and bass and listen to a wide range of music.

Actually, I consider 2A3 borderline on 100db eff. speakers and 300Bs at 6w are probably more like it, but I can't get by how good 2A3s sound.

Just my experience.

and here in lies the whole problem in a nutshell. My 2A3 amp was built with female voice is mind. If you notice it has two sets of inputs. One is normal, and the other is to have a high pass network for a multiple amp situation. My ST70 has a low pas set of inputs. Just planning for the future when I really get some time to build a system.

 

[MechE98]

Thanks everyone for your responses, some great information presented here. I have a pair of RF-82's as well which I had thought were slightly more efficient than the Heresy's, but I confirmed a spec of 98 dB w/m, about the same as the Heresy. I believe both of the impedance curves on these are very similar and relatively flat, but I realize there may be better options. If needed, I can make room for the right speakers to get the best out of the SET designs. I can build from scratch if that's what's needed, looking for a few winter projects as it is :yes:

This setup will most likely be used for a mix of Jazz and classical - Miles Davis - Diana Krall, etc. Room is small and I don't really crank the volume. Rebuilt MC-250 is always available for more demanding genres

Thanks

 

[MechE98]

Anyone have any experience building or listening to the Lessard Seth or Horus designs on the Magnequest site?
Thanks

 

[TerryO]

Triple-digit sensitivity is certainly better with SE 2A3.
I thought my Paramours did fine with a pair of 1974-era Klipsch Cornwalls (ca. 98 dB sensitive @ 1 watt @ 1 meter), FWIW.
Currently using Altec Duplexes (ca. 102 dB) with the JE/Angela "Simple 2A3" and the combination's dandy - relative to my ears and tastes - in a ca. 24 x 26 foot room.
I'd opine (with some empirical experience, but not too much) that 100+ dB is pretty much essential for an SE 45 amp.

It does depend on the benign-ness of the load (i.e., the impedance curve of the speakers), the room size, and the type of music (not to mention how loud) one prefers.

I agree completely.

Sometimes, I just can't believe the equiptment combinations some people come up with. I always thought that I was missing something, or at least until I actually heard a few of those systems in person....it was...well, "unreal." I find that my opinion is in line with yours...it should be 100dB+ speakers to complement a 45 SET amplifier. With the correct pairing, you'll have magic!

Best Regards,
TerryO

 

[TerryO]

and here in lies the whole problem in a nutshell. My 2A3 amp was built with female voice is mind. If you notice it has two sets of inputs. One is normal, and the other is to have a high pass network for a multiple amp situation. My ST70 has a low pas set of inputs. Just planning for the future when I really get some time to build a system.

That's a great idea, not a necessarily cheap one, but it certainly could offer real sonic advantages! I think since Doc Bottlehead tri-amped his speakers with nine 2A3 SET amps (per channel) at the last VSAC, I've become a bit less of a purist.
BTW: All the amps to the right of Dan (Doc Bottlehead) are for the speaker shown in the picture. Another nine amps, for the other channel aren't shown.

In case you're interested, each of the four (bottom) woofers is powered by a separate amplifier. The RAAL ribbon had it's own amplifier and the mid-range used four amplifiers to match the sensitivity of the system. The Bottlehead Room was quite large, so all that power was necessary. Playing Dan's "Tape Project" tapes, the sound was just excellent!


Best Regards,
TerryO

 

[Billfort]

What did he use for crossovers Terry?

 

[TerryO]

What did he use for crossovers Terry?

He used an electronic crossover that was built in-house, but I don't know the particulars. The whole system was so stunning that it was overpowering! The final electronic work was actually completed just an hour or so before the event started and it sounded pretty darn good.

After the event, Dan sold every single amplifier in the system, just so he wouldn't have to pack them up to take home!

Best Regards,
TerryO

 

[jaymanaa]

I did 6 monos once with JBL 7' folded bass horns, altec 500 horn mids, and emilar horn 800s for the **** I can't hear. I used a Berhinger 3 channel EQ with horn comp. etc..... Everyone that heard it, liked the settings at a different place.

 

[Gary Kaufman]

I built a 45 amp a few years ago based on Gordon's 45 Bugle. It has remained one of my favorite amps. With a few changes it will run 45,46, 2A3 or 300B's

http://www.the-planet.org/Ragtop.html

I currently have it paired with Mitshubishi diatone P610's (around 90db/1w/1m) and even with 45's it's quite satisfactory in a large room given appropriate choices of music.

- Gary

 

[mhardy6647]

Single driver, no XO (and a flat, benign impedance curve) helps level the playing field considerably when it comes to amplifier power vs. loudspeaker sensitivity, methinks.

FWIW, the first time I heard those 610s was with an earlier Gary Kaufman 45 amp... a long, long time ago now:

http://www.enjoythemusic.com/bostonbash99/