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Perhaps we needs a 2A3 forum for the truly loony!That being said, I am getting the urge to make a move. Is anyone aware of single-stage 2A3 kits that could use upgraded components to rival the Moth?
How about a pair of Sun 2A3 stereo amp kits at $850 each? I could start with one, then add the second. Aren't they 2-stage with an interstage transformer? I could use the two channels of each amp to bi-amp each speaker.
Would an active crossover be advisable in such a case to minimize power loss in the crossover? (But then, that would defeat the goal of circuit simplicity!!). What are the issues relating to crossovers and SETs? There have been several comments that high-order crossovers are not the best choice. Is crossover efficiency part of the overall efficiency rating of speakers? If you take a speaker that has a 45Hz bottom limit and cross it over at 70-80Hz to a sub, do you increase the effective efficiency of the speaker? Would a crossover between the amp and preamp that doesn't allow the 2A3 amp to see low frequencies be a good idea?
Also, I am considering a used Melos SHA Gold or Gold Reference preamp. They have active, passive and balanced outputs, which offers a lot of versatility. Although I haven't seen any evidence of serious auditions by Asylum regulars, the SHA Gold does have a good reputation. Plus buying used doesn't involve much financial risk.
Dave
...all's I can say is: if my SE84B is actually only delivering 1W RMS, 2A3's represent a whopping 300% increase in power. Bring it on! I think my speakers could take it, but maybe I should put fuses in-line to protect them?I am sure it's about time for subWatt fever to strike. Maybe one can drive speakers directly with 12AX7's?
Actually, when I was a kid, I remember that one of my father's EV LS15's would pick up a nearby Baltimore AM station (WFBR) without any power or electronics at all. He claimed that the speaker coil was detecting the signal. Possibly that's the ultimate in high-fidelity?
;-)
mrh
:-P
Thorsten:...umm... I thought I was making a little joke. Truth is stranger than fiction!
all the best,
mrh
bob danielak has already done that. Check out his 1626-based amps called the Darlings at the link below. Flat out they're 3/4 W.
Hi there,Why a KIT?
Just build something from scratch. Get a large Aluminum Plate. Get Chassis punches. Get wood for a base and get a suitable metal mesh to close the bottom.
Then simply build the schematic above using only Polypropylen Film Capacitors (you can use a 50uF unit in place of the 100uF Electrolytic Capacitors shown), Allen Bradly Carbon Comp's in Input Stage (measure and match them after a while in the Oven at about 80 degrees celsius), Caddock or Vishay Powerfil Resistors for the 2A3 Cathode Resistors and be done with!
Use Tango Output and mains trannies and whatever your favourite set of NOS 5V4 and 6SL7 is.... that should pretty much shred the Moth unit for sound and still cost no more than a sensible $ 1,000 in Parts, evern if you really go shopping.
I intend to build exactly the same Amp but using a NOS Plessy Oilfilled Powertransformer (massivively over-rated) and Parttridge encapsulated Double C Core output Trannies....
Ciao Thorsten
How about JC Morrison's 6SN7 paralleled DC 2A3? HOt-Rodded Nobu's L-W 2A3?Now we got the 2A3 movement going,...where's the celebration??
regards,
Quest
(the guy who was doomed once he was "sucked" into his L-W 2A3 project...)
....an amplifer with three watts would limit our conversation!....lol....it seems to be a huge topic here as of late!
Some guy had an ugly little custom sports-racer displacing not much more than one liter. I think it was called the "Aardvark." Another driver in the multi-class event had a beautiful "stock" class 1965 Mustang 4.7 liter V8. The Mustang would blast by the Aardvark on the long straight, but after about 1.5 miles of curves, the Aardvark would be in the lead again.Moral of the story: Size, beauty and power don't always guarantee success.
Dave VH
But there are creations of size, power and beauty that can overcome the small and gracefull, be they cars or audio.8 litre McLaren Can-Am nimble dancing brute. That was a series that would have been fun to keep going.
you've put your finger on one of the reasons I like vintage sports car races, especially the ones at Laguna Seca associated with the Pebble Beach Concours d'Elegance.The V8 "ground pounder" sports-racers like you pictured give me goosebumps, even thinking about the sound they make that you could feel as well as hear. They're the "big iron" with the big sound - kind of like the old Mcintosh and Marantz amps of the audio world.
Five years ago, I used to get up early Sunday morning to watch F1 racing live from around the world. I loved it when the announcer would say that it was time to start the race, so the audience should turn up the volume and listen to the start while he kept quiet. And I did - with 300wpc driving the the audio signal. Not the same as live, but damn exciting. Even without mid-range liquidity!
Dave
Don't worry about the MC8 goosebumps, I still remember mine at first hearing the beast live. Vintage race of course. Several other McLarens, Chaps and Coyote also running.Still the feeling you get when you can't really see the mark coming, but it is coming down full song on a 3500 ft straight away after a moderate high speed entrance turn, heading towards an 70 degree left hander:
ground shaking low notes with a hi-RPM overtone, burnt orange blurr, shutdown, full brake, downshift, swoosh, gutteral growl open throttle, upshift, gone but still rumbling.Ballerina moves, with a Rugger scrum heart.
:)
Dave, you are correct about the Sun being a two stage amp that's IT coupled. And with two you could do passive vertical bi-amping or horizontal active bi-amping. And I believe thay have level controls on the inputs.Using an active crossover is a good way to go (well, I would say that since I'm using one). The effective power of the amp increases around 20-30% by getting all those passive components out of the way. And it's the passive Xover components that play hob with the impedance curve. But you want to make sure you have a good active Xover circuit that provides an good approximation of unity gain. It's a question of where you want to compromise to a point. Yes, the active is additional circuitry, but a design like the one on Steve Bench's web page is a pretty simple circuit, that when done with quality parts and a good seperate PS won't compromise the sound. I built mine with a passive pre on the front and ladder attenuators on the outputs for level matching (but I am using two different amps).
Another way that has been discussed at length on the Joe-Net is to install an RC filter at the amp's input. This would be minimal extra circuitry, but you would have to be certain tha amp's input sensitivity is up to it. An additional possible down side here is you will have to keep it a simple first or second order filter (most likely first, so you need to know if the combination of drivers will be happy with this), whereas with the active unit you could go third or fourth order with no real penalty.
Anechoic efficiency is an inherent property of the driver and it's motor structure. "In-room" efficiency as it's sometimes called is affected by a variety of variables.
If you are going to do a cutoff at say 70-80HZ to a sub, consider the Paraglows along with the Suns. You're going to take what's hardest for a 2A3 away (deep bass), and the Paraglows would let you use a pair of monoblocks (always a good idea IMHO). And yet another way to go (albeit more expensive) is to do the Sun or Paraglow SE on top and the Sun PP2A3 on the bottom.
What speakers are you contemplating and what will you power a sub with? Oh, if you think this is loony, Doc used to offer to put together a kit on a custom order basis for his parafeed 45s. 1600 mW is true lunacy;-).
Also check out:1. http://www.hare.net.au/~rode/bi-amp.htm
For an excellent explanation on why biamping is more advantageous than passive crossovers. Most importantly for tube amps, active crossovers appear to obviate the requirement for a flat impedance curve in speakers, most notably in the bass region. The downside is that you need more amps. But that's OK because we like amps. The more amps the better!
1. http://members.tripod.com/XSSpl/Audio/Sound.htm
For basic info on passive crossovers in general. I used this info to rewire my speakers to defeat the passive low pass on the woofer and to convert the bandpass on the midrange to a low pass filter. I left the tweeter hi pass as most of the power is apparently sucked up by the bass crossover and the hi pass filter also provides protection for the tweeter.
2. http://www.marchandelec.com/
These guys have apparently high quality crossovers available as kits or preassembled, including tube crossovers. I just ordered the XM-9 kit. Hopefully, the unit will give high quality output without distorting the signal. I'm rationallizing the use of the SS unit as there's already a lot of sand in my CD player that I use as my sole input source. Vinyl enthusiasts would certainly want to use a tube crossover as to not contaminate the sound with silicone ;-) While I'm waiting for the active unit, I'm using a passive crossover that I slapped together with polyester caps and metal film resistors. It consists of a simple 2-way 1st order RC crossover and works surprisingly well. The signal is very clean. Just for kicks, I also tried out a Radio Shack active crossover for car stereos as well as a DBX pro-audio crossover. These did impart some high frequency glare but overall resulted in a huge improvement in the speed and clarity of the bass response and immediacy and clarity in the mids/highs. This glare effect may be due to cheap op amps in these units. One advantage of the Marchand units is the ability to tweak various components. Of course, the most tweakable option would be to build a SS or tube crossover from scratch. Unfortunately, I don't really have the time or $$$ to devote to this route. Overall, the effect of bi-amping is not subtle. Certainly much more apparent than the very subtle effects of changing speaker cables or biwiring.
In the end, I think it is still a compromise as all high performance audio engineering is. The downstream complexity of the passive crossovers in the speakers have been relegated upstream to a less intrusive location. It seems that a lesser compromise that others have taken is to use high-efficiency full range horns. But, this option requires expensive drivers and large-complex cabinets. Although I've yet to hear such a set-up I'm sure it is wonderful.
Comments are welcome.
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