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Deluxe Reverb clone output transformer


 
10/15/2004 6:55 PM
Bob M.
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Deluxe Reverb clone output transformer
I'm looking for a output transformer for my recent DR clone that will give me more more output than the stock transformer and also has better bass response than the original one. Has anyone used one that fits this criteria?  
 
Thanks,  
 
Bob M.
 
10/16/2004 2:19 AM
Wild Bill
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Bob, a Hammond transformer will definitely have a wider frequency range. They're designed for hifi.  
 
As for more output - unfortunately it doesn't work that way. Efficiency is pretty much the same with any transformer. They're just too simple a device. If they did have major efficiency differences we'd have OT's heating up all over the place! It's just physics.  
 
---Wild Bill
 
 
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10/16/2004 2:02 PM
Chris @ CMW amps
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Imho efficiency does differ!  
The way an OT is wound ( simple, interleaved and/or how ) does effect the soundlevel and frequency range/response.  
As example:  
replace a post '69 Marshall 50 Watt OT with one from http://www.ObsoleteElectronics.com and you do certainly get more volume besides a way nicer frequency range and feel.  
 
http://www.MercuryMagnetics.com does make very fine bf DR OTs and using a Celestion G12H30 will also give more/tighter bass and SPL. Ask Paul or Sergio ( if I'm not mistaken ) from MM and they will certainly help you delivering a really nice OT.  
 
Chris
 
10/16/2004 6:16 PM
Wild Bill
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Here we go! :)  
 
Chris, I absolutely agree with you as regards frequency response/range. Where we differ is regarding output power. Lost energy in a transformer becomes heat. I doubt very much if we're talking enough drop in output for the human ear to hear. 3 db is barely detectable - that tranny would be losing 50% of its energy into heat! Might put Mr. Bic's lighters out of business in the music world...  
 
However, we all know that frequency response makes a big difference in hearing perception. Bright amps always sound louder - 5E3's are the obvious example. That's why many amps have a bright switch for lower volumes.  
 
So once again we may be arguing semantics here. When Bob referred to output I understood the term to mean actual watts of energy delivered to the speaker load. If you take it as how it sounds to your ear then we don't have an argument. That's why a 100w vintage Marshall sounds so much louder than a Fender Twin - it's brighter.  
 
I would be very surprised if someone could 'scope out various OT's of the same wattage and find enough differences in energy efficiency to matter in terms of simple power. More likely cheaper OT's fall off so fast in the treble range as to make the amp sound "weaker". If they only pass mids efficiently then they'd get drowned out pretty quickly. An amp needs that upper range. A poor OT would likely lose much more than 3db of highs. With a guitar signal we wouldn't have much waste heat developed - the main energy falls in the midrange. Put a signal generator into the amp at 6-7 Khz and dime the amp for an hour or two and things might indeed get warm.  
 
In retrospect perhaps my response to Bob was too techie. Mea culpa! (But I WOULD have had sex with that woman, to steal a famous quote!)  
 
'Course, if we actually don't have an argument we'll miss out on some fun and won't learn much new... :)  
 
---Wild Bill
 
10/16/2004 6:48 PM
Bob M.
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Wild Bill,  
 
I don't mind techie responses at all but what I'm after here is more 'real world' results than measuring output wattage: If I'm playing a room that I know well and I can now put my amp's volume on 3 instead of 4 and I've got one more number of clean headroom before breakup, it may make the difference if I play that room with this Deluxe Reverb or my Pro Reverb. We all know amps have a 'window' where they speak at their maximum. You can play clean and you can play dirty, you're right on that edge and the amp sounds its best. I'm trying to eek out a little more performance so I can take this amp and play a little larger venue than I've been able up till now and have better success. To me, this is a worthwhile experiment to see if I can get this to work as I envision. But it's not really about the numbers that I'm concerned with in the final analysis although the numbers will predict what's possible, as you've pointed out.  
 
Bob M.
 
10/19/2004 4:32 PM
SpeedRacer
Wild Bill - your point is well taken. I have to toss in some 'real world' research though. Not 'be all end all' by any means, but it was carefully and thoughtfully carried out with no assumptions.. we were just curious! Dave Stork (aka Dr. Distortion) & I did precisely this kind of testing early on in developing the OEI 50W and what we found was very surprising. We compared Simcha's 50W handwound prototype to a stock JCM800 Drake unit and during testing the Drake got quite hot (prolonged full power output testing), the OEI did not. We were able to manage about 45 W @ 5% THD 1kHz with the drake, 65W with Simcha's OT. (using Dave's excellent lab gear.. HP THD analyzer, Tek dual trace scope, etc) Simcha's stayed cold to the touch. I would suspect you'd see much the same difference swapping in a hammond or MM or other Ot where there was more attention paid to various elements of the design. When components are made to a price point, there is always room to outperform them. Whether this is lam quality, wire dia, or whatever I don't know. I do know that in the same amp chassis, same tubes, voltages, etc.. there was a measurable difference. Now 20W is not even 3dB, but where it does seem to be 'audible' is in headroom and available dynamics. The whole amp gets less 'squishy' and more 'punchy'.
 
10/16/2004 6:31 PM
Bob M.
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Thanks guys, for your responses.  
 
I have used Hammond output transformers in past projects and experienced a gain in volume/output as well as, of course, a wider frequency response (increased bass response, ect.). It could be that the transformer replaced wasn't so great to begin with or wasn't working 100% correctly. I'm certainly aware I can't make a 22 watt amp into a 50 watt amp by simply changing one component.  
 
The problem with the Hammond for me is that I'm not sure I want to drill the extra holes in my chassis to accomodate its mounting style and that the size of the Hammond(s) may not work with my cab and speaker placement in my homebrew. They are, of course, a well made, excellent product.  
 
I was hoping to see what other options are out there. I will explore the Mercury Magnetics idea as well.  
 
Gerald Weber (Kendrick Amps) made, at one time, and claimed that his interleaved output transformer would increase the volume/output of a Deluxe Reverb significantly. And, of course, they are priced commensurate to this claim ($$$).  
 
What other tranformers have others used in their Deluxe/Reverb/Princeton/Reverb/2x6V6 clones/original circuits?  
 
Thanks again for your time and experience,  
 
Bob M.
 
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