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OT - The more iron better the better?


 
6/4/1999 12:19 AM
Bob K.
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OT - The more iron better the better?
I have a BFPR. I replaced the OT with a DR OT. The amp works just fine...sounds great. I just came across an old amp (non-guitar) that is running 2 6V6's with a powered by a 5Y3GT. The OT on this thing has 2,4,8,and 16 ohm taps and is easily twice the size and weight of the DR OT I have in the PR right now. I wouldn't mind having the various taps for different speaker combinations. Can I use this OT? Is it worth the effort (not really that much) to put it in the PR? Will I gain/lose some tone? And opinions?  
 
Thanks,  
 
Bob
 
6/4/1999 7:36 AM
BOB ISAACSON
Bob,  
I would suggest that you first try "tacking" in the transformer leads to your amp circuitry  
first and give it a listen check to see how the amp performs. Most p-p 6v6 circuits require around 7-8k on the primary. The extra iron will probably aid in the low-end response,and let you push the outputs harder without overheating the transformer. The downside would be mounting the damn thing on the PR chassis, so it doesn't hit the speaker basket.  
Good Luck,  
Bob.
 
6/4/1999 7:49 AM
Doc
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You can certainly use the oversized transformer for your princeton reverb, if your primary goal is to have greater flexibility when connecting various speakers.  
 
The old transformer may have been in a p-p 6V6 circuit that was running in class A, and was also expected to faithfully reproduce bass frequencies in recorded music. The PR combo is for guitar, and really doesn't need to accomodate frequencies below 80hz. So it's output transformer can be much smaller than a hifi amp's. Also, the PR circuit is designed to run in class AB1, which conducts less continuous current through the OT's windings. That's another reason the PR trans can be smaller and still function properly.  
 
If you hang around here long enough, you won't be able to resist building your own amp. That old transformer might be just the ticket for a great sounding 15 watt amp, using p-p 6V6s (tweed Deluxe circuit) or p-p EL84s (matchless spitfire or vox berkeley type). You could even build it as a head design, and sit it on top of various speaker cabinets depending on the desired sound & application, a sort of mini-marshall.  
 
If you would prefer to install the bigger OT in your princeton, it won't degrade the amp's tone, but I doubt you'll notice any improvement in the stock circuit over the replacement deluxe reverb transformer now installed.  
 
...just my $.02
 
6/4/1999 8:22 AM
R.G.
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There is no way to tell ahead of time whether the change will please you, but it is likely to change the tone a bit.  
 
Historically, many first versions of tube amps were introduced with hifi output transformers and later cost-reduced with special designs. These early ones have very good reputations, so I would suspect a possible improvement, subject to something else limiting response, of course.  
 
I weigh in with Bob and Doc - try it. It's likely to be very reliable in this application.
 
6/4/1999 10:12 AM
Bob K.
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Thanks for the info!
Thanks to all. I think I will try it, jumpering it in the circuit before dealing with a possible problem mounting it. But I am really drawn towards leaving my amp just the way it is....I like it just fine....and using this old amp to launch me on my amp building career. I guess it's about that time.  
 
Thanks again.  
 
Bob
 
6/4/1999 4:01 PM
Richie
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Just be sure to disconnect the other transformer.[Richie]
 
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