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Hammond Transformers for 5E3 Project


 
1/10/2003 2:56 PM
Ed Hammond Transformers for 5E3 Project
I was going to use a 272DX (300v 120Ma) until I built a 5F2A using the 270DX (275v 90Ma) & wound up with 360 volts on 1 6L6 using a 5Y3 rectifier (I thought I might have to use a 5AR4 to get the voltage that high).  
 
So now I think I should stick with the 275 volts & the 270EX (120mA) should be sufficient given Hammonds conservative ratings.  
 
Anyone with a second opinion or additional considerations would be appreciated.  
 
Also, I was going to use the Hammond 125E (80mA 15watts) unless someone can suggest a better 1600 series alternative.  
 
Thanks.
 
2/24/2003 4:03 PM
wayne
email

Hvae you tried the Hammond PT yet? I'm on the fence as well, I just finished the board (hoffman) and was gonna use a Bogen PT that measures 318-0-318 w/no 5v winding and use SS, maybe feeding a 6v rectifier as a pass tube for sag. But I really want this thing to stay near true values and was considering using a Hammond 27??? and 5y recto. Have you had any luck yet?  
 
Thanks  
wayne
 
 
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2/24/2003 6:14 PM
Ed
Wayne-  
Yes, I built the 5E3 with a 270EX & 125E Hammonds.  
Works fine, sounds great.  
The only change I needed to make from the original schematic was to bump the cathode resistor up to 300 Ohms, which gave me ~21.5 cathode volts.  
Other readings are 367 plate volts, & 310 screen volts.  
I also added a Triode switch & 1K 3 Watt screen grid resistors on pin 4 of the power tube sockets (I would recommend 470 Ohm if you won't be adding a triode switch).  
Being new to this, I can't give you sonic comparisons to the other transformers out there, but to my ears, they sound great!  
When I'm a little more sophisticated with this stuff, I'll build using the top rated transformers & see if I can hear the difference.
 
2/24/2003 9:24 PM
WAYNE
email
Nice
Thanks man, think I'm gonna give the bogen pt a shot w/diode rectification,as that I have it on hand. If I dont like the lack of compression/sag I'll go the 270ex/5y route. Yes, like you I havnt been playing or tweaking circuits long enuff to tell odd even harmonics, sonic nuances and such, this may be a real good project to see the diff between SS and tube recto.  
 
Good job bro  
wayne
 
2/25/2003 1:50 AM
Ed
I also just built a SE 6L6 amp with 2 12AX7's.  
For that, I used the 270DAX, which is 260-0-260, 90 mA & no 5 volt- I used diode rectifiers.  
Worked well.  
I'm still tweaking the gain level, I'm going to add a feedback circuit & see if I get the sound I'm looking for.  
-Ed
 
2/25/2003 5:26 AM
wayne
email
Thought of 6v recto?
Not that you need one, but i heard that when using Non 5v PT's you can still get that tube sag by using 6v rectos. I just happen to have one a ez81, seems kind of a redundant quirky mod, but heard it sounds better than SS, who knows, maybe I'll try it w/the bogen pt.  
 
Whats your SE 6L6 circuit? Iv'e got an electar 10 (single 6l6/12ax/SS) and was looking to drop in another ax for better gain/tone stack, any ideas? Blows me away, I replaced the micro OT w/a hammond 125D and run a 12" celestion silver and the thing cranks.  
 
wayne
 
2/25/2003 4:29 AM
Ed
I got the DAX with the sole purpose of using a diode rectifier.  
My SE is loosely based on a high gain preamp from the Torres book, but after rebuilding the preamp completely once over & swapping about 50 parts in & out of the circuit, I don't think anyone would recognize it.  
I got the gain under control without the feedback circuit.  
Now, you can get a decent amount of clean, a good overdrive sound at low to moderate volumes, but when cranked, it still has a real raunchy side.  
I wound up with more of a pre-gain / post gain volume setup, as opposed to a volume & master volume.  
It's pretty cool because adjusting the mix gives you different drive sounds.  
The 1st volume gives you more of a Fender sound, the 2nd more of a Marshall sound.  
If you add another gain stage to your Tube 10, I can tell you right now, you'll have to change all the caps & resistors in there to get the gain under control.  
I've got .001 coupling caps (1 of them is actually 500 pF), and only 1 cathode cap- 1 uF & switchable).  
Two of the gain stages have 2.2M resistors in series to further suppress the gain & I also added a .001 cap in parallel with the B+ resistor on the 1st gain stage to get the screaming to stop at full volume (I might drop that to 500 pF & see if it's sufficient- a little too little high end at low volumes).  
Even with all that, the gain is outrageous (in a good way).  
-Ed
 
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