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Conference napalm::guitar

Title:GUITARnotes - Where Every Note has Emotion
Notice:Discussion of the finer stringed instruments
Moderator:KDX200::COOPER
Created:Thu Aug 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3280
Total number of notes:61432

373.0. "Re-Tubing an Amp: What's The Scoop?" by BUSY::JMINVILLE () Fri Oct 23 1987 14:03

	I'm looking for information on re-tubing my Fender Twin Reverb.
	What types of tubes are available?  What type of "sound" do they
	give?  How much should I expect to spend?  And, can I do it myself?

	My "Twin" has (2) Fender 12" speakers, uses 200 Watts, and outputs
	120 Watts.  The tube diagram on the inside shows the following.  I
	don't know what is actually in it now.

	Can I get tubes that will give:

	1.  More output (volume);

	2.  A warm, clean, full sound?  (I play Rhythm Guitar).


   ^	   ^	   ^	   ^	   ^	   ^	   ^	   ^	   ^	   ^
  / \     / \     / \     / \     / \     / \     / \     / \     / \     / \
 /   \   /   \   /   \   /   \   |   |   |   |   |   |   |   |   |   |   |   |
|       |     | |     | |     |  |   |   |   |   |   |   |   |   |   |   |   |
|     | |     | |     | |     |  |   |   |   |   |   |   |   |   |   |   |   |
|     | |     | |     | |     |  -----   -----   -----   -----   -----   -----
|     | |     | |     | |     |   |||     |||     |||     |||     |||     |||
|     | |     | |     | |     | 
------- ------- ------- -------    
  |||     |||     |||     |||    

 6L6GC   6L6GC   6L6GC   6L6GC   12AT7   12AX7A  7025    12AT7   7025    7025

			--  Joe Minville
			    BUSY::JMINVILLE.
T.RTitleUserPersonal
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373.1Maybe another amp?VIDEO::BUSENBARKFri Oct 23 1987 15:5626
	More volume out of a twin? Replaceing tubes would not increase
nor could it increase volume. If you haven't replaced your tubes for
years,you might hear some difference with new tubes. To increase volume
or output of your amp you would have to consider improving your power supply
capabilities this could be either costly and/or destructive.
	I've always considered Twins of haveing a clean sound.(sometimes
too clean) If you want to try to get a warmer sound out of it you could
try three things. 1. Replace the 2nd 7025 in from the left of your diagram with
a 12ax7. This is your second channel(vibrato)preamp tube. The gain and tone
characteristics of the 12ax7 is less than the 7025. Not a significant difference
but some... 2. Replace your power tubes with Groove Tubes 6l6's,these are rated
in a S for Soft category or H for Hard category from 1 to 10. 10 being a clean
sound to 1 for a distorted sound. This is expensive as the Power tubes could
run you around $100 3. Replace your 6l6's with El 34's which would involve some
resistor changes in the power amp section of the twin. These are what use to 
be stock in older Marshall's. And are found in new Marshalls today from what 
I've heard. This is not a recommended job for anyone as there are potential high
voltages floating around in a tube amp after you power it down and let it sit.
	This will increase your dynamic range and give you a warmer sound. Power
tube replacement is worth doing by yourself,but I'd have your bias checked if 
you do. The above three suggestions are from the least cost to the most....
	There other twin owners here who have had some experiance with some
of these suggestions.......

							Rick

373.2MESA tubes tooFLOWER::JASNIEWSKIFri Oct 23 1987 16:176
    
    	MESA Engineering makes tubes that seem pertty decent too...You
    can replace the 6L6s with 6550s, I believe.
    
    	Joe
    
373.3Groovy Twin !!MORRIS::JACQUESMon Oct 26 1987 11:2635
    	First of all note 309 talks all about tubes.
    
    	I have a Fender twin reverb that I just finished retubing. Since
    I hadn't retubed it in about 5 years I decided to change all 10
    tubes. I ended up buying Groove tubes all around. I purchased my
    twin new in 1979. I think my tube arrangment is the same as yours.
    Anyways, a complete set of groove tubes for my twin cost about $150.oo
    A quartet of 6L6GC's alone cost $80.oo. The 6 other tubes are $12.oo
    each. I believe Mesa tubes will cost just as much, but Groove tubes
    offer you a choice of ratings. I had planned to buy a rather soft
    tube to get some distorsion out of it, but salesmen in 2 different
    stores didn't recommend soft tubes in a twin since it is a push-
    pull amp. I wanted it to sound at least a little bit warmer, so
    I bought #4 hard power tubes. I do notice a warmer sound, and a
    lot more clarity and sustain. I checked with a repairmen about
    having the biasing checked. He said it is a good idea to check it,
    but not always needed. He said that worse case, if the biasing is
    off the power tubes would glow cherry red. I plan to have mine
    checked out and have the pots cleaned anyways.   
                                                                    
    	I priced a set of groove tubes at Mr C's in Marlboro, and they
    wanted $175.oo for the complete set. It would have takin him a few
    days to order them too. I hate to admit it but I ended up buying them
    from Wurlitzers. They had them in stock and the price was right.
                                                          
    
    	Good luck. Get ready to spend some money for good tubes.
    	
    		
    						Mark Jacques