[Rico613]

 
Quote: Eddie Current

Eddie Current introduces the EC-445, a powerful, vacuum-tube headphone-speaker amplifier delivering the natural and lively sound of transformers and balanced listening. The 445 offers a superb sound stage for both headphones and speakers, rivaling dedicated high-end amplifiers with its performance.
 
Specifications:
      -- Single ended, or balanced headphone drive.
      -- Three input selector switch.
      -- 100K high quality volume control.
      -- One pair speaker outputs.
      -- 4-foot detachable umbilical cord.
      -- Hand wired point to point signal circuit.
      -- Vacuum tube rectified power supplies.
-- Inter-stage coupled 6C45pi driver.
      -- Power bandwidth 15-50kHz.
      -- High frequency AC on output tube heaters.
      -- Recommended headphone load 8 ohms or higher.
      -- Power into 8 ohms 3 Watts.
      -- Power bandwidth driving Sen 600’s -.5dB 10Hz to 40kHz Wide band noise less than 250uV 
      -- Tubes included: two 6C45pi and two 6D22S tubes.
-- Dimensions: 12x 14 x 9”  19 lbs.

 

Here is what has transpired so far: 
 
http://www.head-fi.org/t/407413/eddie-current-balancing-act/1335#post_10544542

 

[northshore]

Similar in theory if not topology to the new EC phone/speaker amps, my ZDT with the PSS transformers uses 6c33c (indirectly heated?) tubes for 6 watts per channel. I checked with Craig some time back to see if significant changes warranted upgrading my amp. Since then, the 4-45 and 2A3 Mk4 have come out and his answer would probably be different.
 
Ideally both will be in SF for the July meet for a brief audition.  Other than the obvious – different tubes matched with purpose built transformers – do the topology differences that exist between the three amps also translate into characteristic sound signatures?    

 

[brink]

Anyone who knows if the current batch is all spoken for? This seems like a nice upgrade alongside with the Elektra I have on order..

 

[SleepyOne]

Apart from the obvious sound differences of 45 and 2A3 (both being SET instead of OTL), the topology of 4-45 and 2A3 mk4 got to different to your ZDT as they have interstate transformers, 2 drivers tubes, high frequency heater and a different power supply. I maybe wrong but transformers (brand) seem different between 4-45 and 2A3 mk4. Hopefully you will be able to see them in SF. Probably best to email Craig to re: topology differences between the 3 amps.

 

[northshore]

They're all SET, though the ZD is OTL where the ZDT, 4-45, and 2A3 Mk4 are all OPT. I also owned the OTL DM-2 prototype before the production ZD, then the ZDT. Sound improved each time, but there is a very different sound signature between the OTL and OPT amps. 
 
Also, the 6c33c's are indirectly heated as opposed to DHT 45/2A3, and that's the last acronym for now. I'm not sure how the high frequency heater translates between the two heater designs. I'm wondering if there will be a different sound signature with the new amps, and if so is it based on topology and why.
 
Don't want to bug Craig. If he is in SF I'll check then and while he explains the intricacies of circuit design and other considerations way over my head will hopefully just nod to seemingly to understand what he is saying.  

 

[SleepyOne]

High frequency heater has a lot to do with EC BA's 3D. As those amps have interstate transformers (not the OPTs) so don't have coupling caps.

 

[purrin]

 
Also, the 6c33c's are indirectly heated as opposed to DHT 45/2A3, and that's the last acronym for now. I'm not sure how the high frequency heater translates between the two heater designs. I'm wondering if there will be a different sound signature with the new amps, and if so is it based on topology and why.

 
The 2A3mk4 and 4-45 will sound quite different (but still have the EC house sound) from the ZDT:
 

• Different output transformers. In particular, the 4-45 OPT is quite different from the rest because it has trick tertiary winding which is used for a small amount of feedback.
• Interstage transformers instead of a cap. A faster less constipated sound. More resolving.
• Different tubes. 45, 2A3, 6c33c all sound quite different. The 45 and 6c33c tubes have a consistent sound. But within the 2A3 family, there is a huge variety of sounds depending upon manufacturer and model.
• HF filament heater on 4-45 and 2A3mk4. More openness, deeper stage. DHT (45 and 2A3) will by itself provide a more impressive stage, but the HF heater takes it to another level.
• Parallelled output tubes. Better center stage, stable imaging, image precison, layering, separation. More current / power at low Z loads. Drives orthos much better than BA, older EC models.
• Stiffer power supply. There's been a lot of recent PS work which has now been integrated with the latest amps. Better quality tighter bass.

 

[bmichels]

Very exciting amp this 4-45 ! I'm happy I placed an order for the next batch

 

[Hun7er]

Which EC has the most thicker and relaxed sound ?

 

[purrin]

The current 2A3mk2

 

[SleepyOne]

Add in a pair of tuber/ romantic sounding 2A3

 

[northshore]

   
The 2A3mk4 and 4-45 will sound quite different (but still have the EC house sound) from the ZDT:
 

• Different output transformers. In particular, the 4-45 OPT is quite different from the rest because it has trick tertiary winding which is used for a small amount of feedback.
• Interstage transformers instead of a cap. A faster less constipated sound. More resolving.
• Different tubes. 45, 2A3, 6c33c all sound quite different. The 45 and 6c33c tubes have a consistent sound. But within the 2A3 family, there is a huge variety of sounds depending upon manufacturer and model.
• HF filament heater on 4-45 and 2A3mk4. More openness, deeper stage. DHT (45 and 2A3) will by itself provide a more impressive stage, but the HF heater takes it to another level.
• Parallelled output tubes. Better center stage, stable imaging, image precison, layering, separation. More current / power at low Z loads. Drives orthos much better than BA, older EC models.
• Stiffer power supply. There's been a lot of recent PS work which has now been integrated with the latest amps. Better quality tighter bass.

I’m biased to the EC house sound, very nice to have new phone/speaker amps to consider. The Jeff Korneff 45’s are highly acclaimed, but can't bet against EC. Also can’t pigeon hole Craig into stereotypical tube sound using the 2A3 or 45 or 6c33c, so still really have to listen to them to hear what he's done. Just replaced the 6c33c's, the idea of consistency in driver tubes is a valid benefit.
 
What I still like about the ZDT is the nuanced, complex sound Craig gets with a simple SET circuit. No negative feedback, and at 6 watts the 6c33c tubes are run very conservatively limiting distortion. He got an unbelievable frequency range with the custom PSS trannies. I guess Jack is now only doing transformers for his own amps, so onward and upward.
 
I actually thought the ZDT would use interstage coupling, but it seems some tubes like them and some don’t. Also, many hold that capacitors actually have the less congested sound and adhere to the simpler is better school of thought. They can be rolled like tubes, those new Jupiter copper caps might be good candidates. Sure much less expensive than good interstage transformers which helps explain the $4,500. 
 
Paralleled output tubes as well as interstage transformers both have potential for quality bass. When paralleling output tubes the power supply has to double output. As you say, that stiffer supply should also contribute to better bass. That would be a big plus with low Z speakers, the ZDT already does a great job with orthos and no doubt both the paralleled amps do as well.
 
Wonder why the 45’s are putting out 2 watts instead of 3? That 33% difference might help with speaker selection. I finally found a wide range speaker with really great detail and without a bright rising response in the Alpair 12P. Though at 92db sensitivity 6 watts is barely enough so even at 3 watts would have to go another way. 
 
Informative post, thanks.

 

[Hun7er]

  The current 2A3mk2

 
Okay. It is also the darker and warmer ?

 

[SleepyOne]

Doubt it will be too dark or excessively warm, not really EC sound. The level will probably dependent on 2A3 used. I have no idea what the new drivers tubes sound like. 

 

[bmichels]

Someone might be interested in this TSAKIRIDIS Tube tester displayed at the Munich's HIGH-END Show : 
 

 
And those TAKATSUKI tube TA-300B :