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Help with voltages on a JE Labs 2A3 SE amp?

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I've been building the JE Labs 2A3 SE amp. I have a test circuit complete on breadboards and my voltages aren't quite right.

You can see in the photos what the voltages should be in the square blocks, ignore the voltages I have beside them. I've gone over everything over and over. My resistances are all correct. I've tested the tubes again. Not sure what to do. I know slight changes in the bias can have a lot of affect. Also, this is my first build.

Should I adjust the resistance to get the correct voltage? I'm not sure how it would affect my plate loads and load lines.

Also, when you have direct coupling like this, how would the load lines be done for the second stage. The grid would be 70v , and the plate is at 210v. It's bias is 76v. Would you go by the -6v for your load line. Would the plate be 210v - 76v = 134v. I'm just not sure how that works when direct coupled.

I didn't show in the schematic. The bias voltage on the first stage should be 1.5v , and the second 76v.

Any help is appreciate , Kennyg
 

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I've been building the JE Labs 2A3 SE amp. I have a test circuit complete on breadboards and my voltages aren't quite right.

Should I adjust the resistance to get the correct voltage?

The grid would be 70v , and the plate is at 210v. It's bias is 76v. Would you go by the -6v for your load line. Would the plate be 210v - 76v = 134v.

This is well within expected tolerances for tubes, another tube will differ.

For DC yes, but the AC load line (at the DC bias point) deletes the bypassed resistance.
 
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Well, it's not that simple. I had a large power transformer that I've been wanting to use. It's much larger than needed, but will work fine. It is 375-0-375. As for the schematic. I think the one in my photos is a sun audio. I originally was looking at a JE Labs schematic. There are so many that use the exact same 2 stage 6SN7 setup. For 2A3s, 45s, 300b, ect. Some use 2.5k, 3.5k and 5k Opts. Another thing I'm dealing with is I'm using 5k output transformers. All the 2A3 schematics have 2.5k-3.5k OPT. I had the OPTs, power transformer, two NOS RCA 2A3s, and two RCA red base 5692s. So this is what I'm working with. I've purchased some cheap tubes till I get it close. I'm to the point that all my voltages are good except what I stated at the beginning of the thread. I think I may try my good tubes now. I've had no issues other than the voltage differs.

I'm understanding load lines fairly good except for when directly coupled as I asked earlier. Hopefully someone can help me with that.

Kennyg
 
I have used a 5k transformer with a 2A3.

A problem with using 8 Ohm speakers on the 16 Ohm tap is that you will double the insertion loss of the transformer (loss that is due to the primary DCR and secondary DCR).

Suppose the primary is 5k with a DCR of 250 Ohms, and the secondary is 16 Ohms with a DCR of 0.8 Ohms.
If the load on the 16 Ohm tap is 16 Ohms, the transformer insertion loss will be 1 dB.
If the load on the 16 Ohm tap is 8 Ohms, the transformer insertion loss will be 2 dB.
 
My op transformers only have 8 ohm taps. So that solves that issue. I hooked it up to some speakers and it sounds really good. I think I can get a little more power out of it though. I hooked it up to the scope with a 1vpp tone, and I'm only getting around 11vpp out. One good thing is there is no hum.

Kennyg
 
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