Dennis Had Inspire Amps

[FloridaBoy]

Originally Posted by Bombadil

On my Inspire EL84, it is my perception that when using a 5V4GA the sound is a bit edgier. As in a bit too edgy. Smoother with the stock 274B or a vintage 5U4G.

That rectifier may be too much for the EL84.

[Rosco65]

Originally Posted by FloridaBoy

That rectifier may be too much for the EL84.

I agree - a 5Y3 may be a better choice.

[Analog Addict]

Or better yet, what they're going to wind up as?

[Analog Addict]

EDITED/duplicate post

[Analog Addict]

Speaking of tube rolling, I had an afternoon off last week, so I went over to the shop with a bag full of vinyl and a bag full of old toobs.







Also did a little measuring on the bench, but that's a story for when I have more time.....



Also saw this lying around on the assembly bench....

[Bombadil]

Originally Posted by FloridaBoy

That rectifier may be too much for the EL84.

Wouldn't a 5U4G or 274B (this is the stock tube) drive the EL84 harder than a 5V4GA? Dennis told me that using a 5V4GA was fine. The only power tube I can use in this amp is the EL84.

[FloridaBoy]

Originally Posted by Bombadil

Wouldn't a 5U4G or 274B (this is the stock tube) drive the EL84 harder than a 5V4GA? Dennis told me that using a 5V4GA was fine. The only power tube I can use in this amp is the EL84.

Tube Type DC mA PIV FIL AMPS Max ACV DCV DCV DROP

5AR4 / GZ-34 250 1500 1.9 450 415 10
5V4-GA 175 1400 2 375 400 25
GZ37 350 1000 2.8 450 388 37
5U4-GA 250 1550 3 450 381 44
5U4-G 225 1550 3 450 381 44
5U4-GB 275 1550 3 450 375 50
5Y3-G/GA 125 1400 2 350 365 60
5R4GYB 250 3100 2 900 362 63
5R4G/GY/GYA 250 3100 2 750 358 67

The last number on the table is the voltage drop. Smaller numbers drive the tube harder. You can use the 5V4GA but it apparently is not driving the EL84's in the sweet spot. I quit trying to analyze the circuit and just use the tubes that sound best.

BTW, do you ride a Bombadil? I have a Bleriot and ordered a Chevoit frameset.

[BearCityUSA]

Originally Posted by Analog Addict

Or better yet, what they're going to wind up as?

Oh Oh Oh!... I know! Pick me! Pick me!

I have dibs on one of these PSE chassis already.

[Bombadil]

Originally Posted by FloridaBoy

Tube Type DC mA PIV FIL AMPS Max ACV DCV DCV DROP

5AR4 / GZ-34 250 1500 1.9 450 415 10
5V4-GA 175 1400 2 375 400 25
GZ37 350 1000 2.8 450 388 37
5U4-GA 250 1550 3 450 381 44
5U4-G 225 1550 3 450 381 44
5U4-GB 275 1550 3 450 375 50
5Y3-G/GA 125 1400 2 350 365 60
5R4GYB 250 3100 2 900 362 63
5R4G/GY/GYA 250 3100 2 750 358 67

The last number on the table is the voltage drop. Smaller numbers drive the tube harder. You can use the 5V4GA but it apparently is not driving the EL84's in the sweet spot. I quit trying to analyze the circuit and just use the tubes that sound best.

BTW, do you ride a Bombadil? I have a Bleriot and ordered a Chevoit frameset.

I thought the first number in your table, the max DC output current, was the primary factor in how hard the output tubes are driven. The stock 274B is 225, the 5V4GA is 175, and the 5Y3GT is 125. Then the voltage drop is the sag in those volts when the rectifier is driven hard, i.e. how much voltage can be drawn on peak demands. So if one subtracts the sag, the 274B drops 44 volts to a max of 181 on peaks, the 5V4GA is 150, and the 5Y3GT is just 65.

Now, I'm no expert on such things and I could be wrong. If the above is true, then the 274B should always be able to deliver more voltage than a 5V4GA. And the 5AR4/GZ34 is highly desired by those wanting to get max power out of the output tubes, as it can deliver up to 250V with a sag of just 10V, thus it is almost linear in its output.

[Bombadil]

Originally Posted by FloridaBoy

BTW, do you ride a Bombadil? I have a Bleriot and ordered a Chevoit frameset.

No, I don't. I wouldn't mind having one. That frame is made here in Wisconsin, I've toured the small factory where it, and a few other Rivendell frames, is made. I think they discontinued that massive Bombadil frame set. I like more relaxed frames now, so I'd probably go with a Clem Smith Jr., but I mostly ride recumbents now. Have a RANS Stratus steel frame which I like a lot.