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2a3 / 45 amp build opinions

mhardy6647 said:
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/
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Yes, all of those factors are very important. I wouldn't doubt that you've seen one my rants over the years about the importance of the "character" of the "impedance curve" to know that we certainly agree!
:thmbsp:

I have a friend that designed a small, rather modest speaker a few years ago that is quite nice with it's small woofer and really smooth impedance curve. It sounded nice in his system, but not particularly remarkable in any way. I also built a pair, after he tricked me by giving me a pair of the woofers! Anyhow, I took them to an all tube meet in Canada and everyone thought they were great...and they were! My friend recently built a tube amp and the little speaker has resumed it's place of honor. He has several speakers that sound better on his home theater amp, but none of which sounds nearly as nice with his tube amp.

Best Regards,
Terry
 
Motor Run Caps In Power Supply

Update: After much decision, I decided to clone the Brook 12a. I have just about all the parts less one filter cap I forgot to order. All I need is a single section 40 mfd cap. I found several offerings for 40 + 40 caps, which I could use a single section, but no / few single section at the required voltage - except Polypropylene / oil motor run caps. I've done a fair amount of research on these, specifically the modern offerings from CDE, ASC and others. As far as I can tell, there really is no downside to using motor runs vs. electrolytic caps other than the space they will occupy on the chassis.

This would be the first cap after a 5U4 rectifier, so I would be filtering a 120 hz ripple. All the motor runs are rated at 50/60 hz, however and I've read there is no issue from users with the higher frequency. Can someone explain what the effect of the higher frequency is on the cap? Do other specifications change in response? If you are running these in your amp currently I would appreciate comments as well - Thanks
 
I think they would be impractical as high-capacity reservoirs after the filter and serve no advantage before. Used as audio bypass in a sort-of "ultra-path" application makes sense.
 
MechE98 said:
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
Click to expand...

I have built the 2A3 Baby Ongaku with caable to run with 45 tube. It sings very good with Klipsch speaker. Myself, I like the 45 over the 2A3. Build it, you will not regret for doing that.

Going here
http://m.youtube.com/?reload=7&rdm=y3p6250q#/results?q=baby ongaku&sm=1

You can preview video clips that I made for Baby Ongaku SET . Good luck with your build!


Binh
 
I have Heresy I speakers being driven by a 2A3 SET homebrew amp driven by 6SL7's in an SRPP setup. I don't use a preamp...just a passive 100K volume control. Volume is more than ample with sources that have normal line level output but some of the modern stuff I plug in (like phones and LCD TV's) don't quite have enough gain to drive sound to loud levels. I don't mind because I usually use the system for normal background listening but if I was watching a movie with some dynamic stuff to it, there would be disappointment.
 
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