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OEI output transformer, EL34 or 5881? which has a better sound?

9/24/2000 2:21 AM
OEI output transformer, EL34 or 5881? which has a better sound?
I wanted to ask about the OT you sell. Can you use 5881s with as good results is sound as if you used the EL34s on the OT? I have been considering a OEI ot for my SLO clone but I have to use the 5881s in the amp I want to install the OEI in as the PT in the amp cant handle the heater current of EL34s and I dont have any more room to install an additional filiment trannie in the amp.  
Thanks and Cheers...  
9/24/2000 4:56 PM

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9/24/2000 11:47 PM
Dave K

Not Speedracer,but I do have an OEI tranny in a prototype amp.The 5881/6L6 will work great with this OT,I'm jumping back and forth between Svetlana EL 34's and 6L6's,can't decide which I like better.  
The OEI has a nice response in the top end,warmth and presence without harshness.  
Sounds incredible with high gain circuits!  
Joe,any idea when the 100 watt version will be ready?  
Dave K
9/25/2000 2:41 AM

Hey Guys.. sorry I missed this one!  
I didn't test at all w/6L6 types bc basically we spent all our time trying to nail the EL34 tone!:)  
I have read of at least one Ampager who reported using the Czech 6L6 with great results. I don't think the 3k4 load is a big problem for them as long as you're not pushing max diss at idle. Basically, the "napkin math" on the load value is that as you reduce it, the plate has a tougher time (increased current) while the screen has an easier time. So if the plate structure of the tube has time to cool (duty cycle) then you're in good shape. Most tubes seem to buy the farm when their screens short to something..  
re: 100W OT. It's in prototype. I'm hoping to go into production before the end of the year, but sometimes it's harder to get the things sounding right quickly than other times.  
If we get lucky it will be ready sooner. :)  
In any case, we won't make it until it's right.
9/25/2000 2:32 PM
Peter S

Hi Guys,  
I've used the Tesla 6L6GC and also Phillips 6L6WGB with the OEI OT. I biased them at about 50% max dissipation at idle. No problems encoutered. The transformer actually runs even cooler than it does with EL-34's because the 6L6's just won't draw as much current as an EL-34(given the same circuit). Both types of 6L6GC's perform perfectly well with the 3.4K load with no signs of stress. They sound a bit rounder, with a little more coloration at clean settings, but at full tilt the 6L6's don't lose as much high end as the EL-34s do. The 34's have when driven hard have a little more midrange honk and less high fizziness in the distortion sound.  
9/30/2000 7:32 PM
Bryan James

What about the other way around? could you run EL34's on a 50W OT that was made for 6l6's?? or well you be pulling more then the PT can handle?  
Bryan James
10/1/2000 1:20 AM
Steve A.

... or well you be pulling more then the PT can handle?  
    EL34's will draw a lot more heater current than 6L6's; you can compare the actual heater voltage using EL34's vs the 6L6's and if there is a "significant" voltage drop when using the EL34's you better pull them out... I guess if it drops from 6.3vac to less than 6.0vac you better get professional advice.  
    This is assuming that your PT is from an old amp and you have no idea what the actual specs are.  
Steve Ahola  
P.S. I have a hunch that a nice OT (like Speed's) will sound better even when mismatched than a lousy OT with the impedances matching perfectly... ;)
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