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5F1 Champ


 
10/9/2005 10:31 AM
Keith
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5F1 Champ
I have just finished a 5F1 design and it sounds great. I like the sound of the 6V6 tube in SE configuration. But I couldn't help but plug in a 6L6 tube to see what it sounded like too. The sound is definitely different and seems to be almost twice as loud. Is there any risk in leaving the 6L6 running in the 5F1 circuit? I noticed that the B+ dropped a ittle but I assume thats because of the 6L6 pulling more from the supply. Also is the 5Y3 going to be enough to handle the 6L6 or should I bump up to a 5U4?  
This is my second tube amp build from scratch, the first was of course the 5E3. I'm hooked now! My next project is going to be a 50 watt head design with a 4 x 12 cabinet.  
 
 
Thanks -  
Keith
 
10/9/2005 11:48 AM
steve
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Is there any risk in leaving the 6L6 running in the 5F1 circuit?  
 
It depends, what power transformer did you use? What output transformer did you use?  
 
If the PT isn't up to supplying the amount of current required in a Class A circuit like the 5F1, worst case is that it could burn out. You need to calculate how much current the 6L6 is drawing in the circuit and compare it to the specs of your PT.  
 
Along the same lines, if you push too much unbalanced DC through the primary and the OT is not up to it, it can burn out. Some of the 5F1 OT replacements I've seen are tiny, I'd be hesitant to use one with a 6L6, personally.  
 
Also is the 5Y3 going to be enough to handle the 6L6 or should I bump up to a 5U4?  
 
According to the data sheets a 5Y3 can handle up to 125mA of current, so you're probably okay. It drops 60v at 125mA, so if you do bump up your amp to a 5U4 your plate voltage will most likely go up as the 5U4 drops 44v at 225mA. Be aware that the 5U4 draws 3A from the 5v filament, make sure your PT is up to that. You could try a 5V4 which is rated for 175mA and drops 25v at that current draw, so you B+ will go even higher.  
 
This is my second tube amp build from scratch, the first was of course the 5E3. I'm hooked now! My next project is going to be a 50 watt head design with a 4 x 12 cabinet.  
 
It is addictive :)  
 
HTH,  
 
Steve
 
10/12/2005 10:45 AM
Keith
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Hey Steve -  
I am using a Weber 022772 which has the capablitity to drive the 6L6 at 100mA. My B+ is 348V on the plate and 296 on the grid. You are correct about the output transformer, I used a Triode Electronics TF103 which is only good for 40mA - yuck. I guess for this amp I just have to stick with the 6V6 tube.  
This gives me an excuse to build another amp though!
 
10/12/2005 12:19 PM
Bruce /Mission Amps
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Hold on.  
Pop over to WeberVST and get one of the new $28.00, 15 Watt SE OTs Ted and I came up with!!  
It is rated at around 100ma.  
You'll be very happy with it.  
 
https://weberspeakerscom.secure.powweb.com/store/se15sch.jpg  
 
Bruce
 
10/12/2005 12:40 PM
Steve A.
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Bruce said:  
 
Pop over to WeberVST and get one of the new $28.00, 15 Watt SE OTs Ted and I came up with!!  
 
 
    So is that one of the Chinese ones without the UL listing that will burn your house down? Just kidding! (There was that guy who was "stalking" Ted going from forum to forum and proclaiming the dangers of these transformers. Or was that just the PT's? BTW I assume that the PT's are thermally protected with some sort of internal fuse... true?)  
 
Steve Ahola
 
10/12/2005 1:34 PM
Bruce /Mission Amps
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Yeah that's a guy that Ted and I know who seams to have a personal problem with Weber right now.  
 
This W15SE OT is a slightly heavy duty version of a 15w Hammond 125ESE... but at a reduced cost, not tone or quality.  
I've run it through the wringer with excellent results.  
 
I don't know of any PT with an internal fuse Steve. ;)  
 
Hey, did you get a chance to put the tone/vol mod in your "vintage" MA 5E3?  
Don't forget to unmod all the stuff we did to it years ago as you'll find most of those tweaks unecessary now.  
 
Bruce
 
10/12/2005 1:58 PM
steve
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Bruce,  
 
Concerning that Weber OT:  
 
This W15SE OT is a slightly heavy duty version of a 15w Hammond 125ESE... but at a reduced cost, not tone or quality.  
 
Is the frequency response the same as the Hammond 125SE series, i.e. "100 Hz. - 15 Khz (+/- 1db max. - ref. 1 Khz"? (copied from Hammond's site)  
 
The reason I'm asking is that I found these OTs online, referenced in one of the audiophile BBS pages I read:  
 
http://www.edcorusa.com/classx/tube_output/xse/xse.htm  
 
Specifically this one:  
 
http://www.edcorusa.com/classx/tube_output/xse/xse15-2.htm  
 
Frequency response 70 Hz. to 18 kHz. 5KΩ:8Ω, 15 watts, has a 40% screen tap for UL operation.  
 
About $18.00  
 
[Weber's OT]  
I've run it through the wringer with excellent results.  
 
I bet you did :) I feel for the poor little bugger ;)  
 
steve
 
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