ArmchairPhilosopher
Headphoneus Supremus
Seriously, this thread should come with an "Adult Content" warning… 
L0rdGwyn's DIY Audio
- Thread starter L0rdGwyn
- Start date
Took a little longer than I thought, but it always does. The 2A3 amp is done.
The final build with RCA 5687 and RCA 2A3.
The amp has excellent measurements. Distortion is very low.
1mW into 32ohm 0.036% THD
1mW into 120ohm 0.0066% THD
1mW into 300ohm 0.020% THD
1W into 32ohm 0.36% THD
1W into 120ohm 0.35%
1W into 300ohm 0.21%
Bandwidth is excellent as well.
Listening for the first time, this may be the most transparent amp I have made or heard. Amazingly clear and dynamic with the AC, huge soundstage. Probably the most impressive thing I've noticed so far: given its detail, clarity, and precise imaging, you can listen at very low volumes and not feel you are missing any of the detail. Oh and it's dead silent on high impedance setting
The final build with RCA 5687 and RCA 2A3.
The amp has excellent measurements. Distortion is very low.
1mW into 32ohm 0.036% THD
1mW into 120ohm 0.0066% THD
1mW into 300ohm 0.020% THD
1W into 32ohm 0.36% THD
1W into 120ohm 0.35%
1W into 300ohm 0.21%
Bandwidth is excellent as well.
Listening for the first time, this may be the most transparent amp I have made or heard. Amazingly clear and dynamic with the AC, huge soundstage. Probably the most impressive thing I've noticed so far: given its detail, clarity, and precise imaging, you can listen at very low volumes and not feel you are missing any of the detail. Oh and it's dead silent on high impedance setting
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ArmchairPhilosopher
Headphoneus Supremus
Very nice.
Sorry if this has been asked and answered before, but…
What's your measurement setup? I don't think I recognize the graphs from any software I'm familiar with…
Sorry if this has been asked and answered before, but…
What's your measurement setup? I don't think I recognize the graphs from any software I'm familiar with…
MOTU M4 DAC output > DUT > adjustable dummy load > Linear Audio Autoranger > MOTU M4 ADC input > REW (Room EQ Wizard) Software
ArmchairPhilosopher
Headphoneus Supremus
Ah, gotcha. Are you reasonably happy with that setup?
I've been using a Focusrite Scarlett 8i6 and Arta. Not exactly all that thrilled with Arta, though. Feature-rich, but quite finicky to use. Maybe I'll give REW a shot at some point.
Thanks!
Yeah I am! The MOTU M4 has some quirks though, at some point I plan to upgrade to a better DAC / ADC. I've used Arta in the past, but REW has much more functionality, a bit of a higher learning curve though.
Listening to the Caldera now on the medium impedance setting, the sound is superb, it doesn't get much better than this. And I'm using a fairly mediocre pair of 5687, hard to think of the sound getting any larger than it is, but I know for a fact it will grow with a pair of NOS E182CC.
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Well, my HY69 chassis is on the way, going to be back-to-back endgame amp builds! Probably will get started on that one next weekend.
Switched from RCA 5687 to RCA 7044. Listening with the HD650, up there with the best I have heard it.
heliosphann
Headphoneus Supremus
Keenan, is the tube placement a design choice or necessary for the circuit design? Not used to seeing the power tubes tucked away like that.
Layouts start to get a lot more complicated when you're using interstage transformers since they're big and prone to noise pickup. Ideally you get them as far away as possible from the mains transformers, which is the reason they're positioned at the front of the amp. The power tubes being where they are is simply because the interstage transformers need to be at the front. Some interstage are small enough to fit inside the chassis, but not the case here.
I prefer E182CC to 5687 tooListening to the Caldera now on the medium impedance setting, the sound is superb, it doesn't get much better than this. And I'm using a fairly mediocre pair of 5687, hard to think of the sound getting any larger than it is, but I know for a fact it will get grow with a pair of NOS E182CC.
Looks as if the 2A3 picks up 'noise' from the Clarity cap.Switched from RCA 5687 to RCA 7044. Listening with the HD650, up there with the best I have heard it.
whirlwind
Headphoneus Supremus
This is very cool Keenan. What a behemoth!Took a little longer than I thought, but it always does. The 2A3 amp is done.
Here is the circuit.
And the final build with RCA 5687 and RCA 2A3.
The amp has excellent measurements. Distortion is very low.
1mW into 32ohm 0.036% THD
1mW into 120ohm 0.0066% THD
1mW into 300ohm 0.020% THD
1W into 32ohm 0.36% THD
1W into 120ohm 0.35%
1W into 300ohm 0.21%
Bandwidth is excellent as well.
Listening for the first time, this may be the most transparent amp I have made or heard. Amazingly clear and dynamic with the AC, huge soundstage. Probably the most impressive thing I've noticed so far: given its detail, clarity, and precise imaging, you can listen at very low volumes and not feel you are missing any of the detail. Oh and it's dead silent on high impedance setting
Zach is going to have a lot of fun with this.
How much does it weigh?
Thanks! Good question, I don't have a scale in my house so I can't be certain, maybe 30-40 lbs?
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