My first SE 2A3 amp, impressions

I got one of Bricktop's builds and he says hey measured 5WPC and I got to believe it.
Sounds like more then that to me but I am using some vintage speakers in a home brew cabinet with moderen caps.

That's good enough for me. Look at the plate structure of the tubes in this amp. They are probably closer to a 300B than an RCA 2A3 as far as dissipation goes. That's why I suggested making sure of voltages and current if going to old stock tubes. I wouldn't be surprised if the B+ isn't up around 4 bills, and if these new tubes will take it, why not. The only reason I'm not running 2A3s upstairs is because of power limitations. I like my music loud. :smoke:
 
That is a Beautifull Amp!

Wondering how much power is enough?
When I connected my Audio Output meters, I was surprised how little power it took to drive my Pro-22 Monitors with just 87 db/w sensitivity. Much of the time there in the 2w range and sounded really good. 5 wpc with more effiecient speakers (90 db/w) might be enough for many of us and would make about 91 db in room. Most speakers in the 87 db/w range require about 20 wpc for 94 db in room. For each 3 db increase in sensitivity, power requirements are half.

This is based on no Tone/EQ or loudness on. Some SS Amps like NAD and HC have much more headroom than others, making their 50 wpc sound like 100 wpc.
 
Last edited:
That thing is beautiful, love the paint, congrats!

Thanks!

I almost asked for the black version but almost everything else I own is black, even most of my tee shirts lol!

Will be interesting to see what's inside. :scratch2: Don't know if I'll be able to wait till tomorrow. :D
 
Here's the underskirt shot. Boards as I suspected at this price range, which is OK. Bias pots that are accessible from above which is nice. Also nice is that the coupling caps are easily changed out. They are .22uF at 630Vs, I have .33uF 1000V silver/oil Mundorfs which should be great. Also am thinking of adding in a bit more PS filtering but am not sure where it would work best, before or after the choke :scratch2: For that I have some 35uF 600V CDE polys. :thmbsp:

attachment.php
 

Attachments

  • SE 2A3 amp #3.jpg
    SE 2A3 amp #3.jpg
    139.5 KB · Views: 709
My Chinese Dared 2a3c claims an inflated 8 wpc but 3.5 I believe is the norm for most 2a3 SET amps. The 2a3c Shuguang tubes that came standard in the Dared are my favorites and I use them in my Paramours. I've also tried RCA and Sovteks.

Both my 2a3 SET amps have fixed bias.
 
Also am thinking of adding in a bit more PS filtering but am not sure where it would work best, before or after the choke :scratch2:

If there's a cap before the choke, changing it to a larger value is probably not a good idea, unless you intend to use a different type of rectifier tube. Increasing capacitance after the choke can also put stress on the rectifier. If you want to upgrade the existing caps, stick with the stock values unless you can accurately model the existing power supply.

jeff
 
If there's a cap before the choke, changing it to a larger value is probably not a good idea, unless you intend to use a different type of rectifier tube. Increasing capacitance after the choke can also put stress on the rectifier. If you want to upgrade the existing caps, stick with the stock values unless you can accurately model the existing power supply.

jeff

Yep. I think that around 60uF is max after many tube rectifiers. I was planning on using a 35uF poly I have a few of made by CDE. They are high quality caps. I've found that a poly after a tube rectifier can smooth things out nicely :yes:
 
Last edited:
I don't see a lot of capacitance in there...or a choke. Looks like two electrolytic capacitors near the rectifier... probably 50uf range.

More pics perhaps? Is there a choke? Schematic? :)
 
Nice. You've got lots of real estate under there to add some nice poly film capacitance.
 
I don't see a lot of capacitance in there...or a choke. Looks like two electrolytic capacitors near the rectifier... probably 50uf range.

More pics perhaps? Is there a choke? Schematic? :)

Choke's up top, rage. :)
 
Hey Lar, looks like it might not be too difficult for you to remove one of those transformer covers. I've always been curious... would you be willing to scratch that itch for me? :scratch2:
 
Hey Lar, looks like it might not be too difficult for you to remove one of those transformer covers. I've always been curious... would you be willing to scratch that itch for me? :scratch2:

Crossed my mind as well Nate :D

When turning the amp over for the nudie picture I happened to tap one of the tranny pots and discovered they are not true potted trannies but tranny covers. Still with the weight of this thing the iron is fairly substantial. The covers do look nice as well :yes:
 
Just wondering where the best place would be to add some extra capacitance in the PS before or after the choke? Only going to add 35uf but it will be poly capacitance.
 
To be on the safe side, after the choke. What is in the amp now? Is it CLC, and why exactly do you want to add C to the PS? Is it noisy?

jeff
 
To be on the safe side, after the choke. What is in the amp now? Is it CLC, and why exactly do you want to add C to the PS? Is it noisy?

jeff

I don't have the schematic but since there are two PS lytic caps and the choke it is likely CLC.

It's actually quite quiet but not totally quiet. There is a very slight background sound that has a cycle to it. Can't hear it when music is playing and it isn't increased when the volume is increased. I figure that a little poly filtering would clean it right up. :scratch2:
 
Just wondering where the best place would be to add some extra capacitance in the PS before or after the choke? Only going to add 35uf but it will be poly capacitance.

Yes after the choke, also if you had one or got one then say like an 1-2uf poly
cap paralleled onto the cap in front of the choke would be a good place as well.
 
Back
Top Bottom