edgar_allan_poe Posted February 22, 2008 Posted February 22, 2008 My favorite tube, the 7581A, is getting damn near impossible to find and I was wondering if there was a suitable replacement. I saw this at The Tube Store and was wondering if this was true...Here's an interesting side note: the JAN-Philips 6L6WGB tube has the identical internal construction as the Philips 7581A tube (the industrial version of the 6L6GC tube). The difference between these two tubes is only the size of the glass bottle. Although you may not get a 7581A's 35 watts out of the 6L6WGB, you can certainly get 30 watts without any problems. These are super durable tubes made for the US military in the mid '80's. Their specs are not the same as earlier 5881 and 6L6WGB specs from the 1960's. So to get to the point, the JAN-Philips 6L6WGB tube will work perfectly in any amp requiring a 6L6GC tube. Do not worry about plate voltages over 400V with this puppy.If it is, I will probably snag a few quads and call it a day...somehow I have a feeling this is BS.
Mr Fuzzy Posted February 22, 2008 Posted February 22, 2008 7027A will work as an option. They are a 6L6 variant.The socket pins 1 and 8 should not be connected in order to use the 7027A.5881 are an option too
AdmiralB Posted February 22, 2008 Posted February 22, 2008 I saw this at The Tube Store and was wondering if this was true..."It depends".The internals *are* indentical. Realize that by 1980 or so (probably even earlier), the writing was on the wall for tube production. While there was still lots of equipment out there that called for 'older spec' tubes, the manufacturers figured (probably a lot earlier, but definitely by the '80s) that there was no reason to make many different versions of a tube, when they could build the 'top end' spec and just label them appropriately.That's why there are no differences between 12AX7s and 7025s, by the latter days. They build them all to the 7025 spec and marked them (and priced them) accordingly.Likewise, pretty much any USA 6BQ5 by 1980 was really a 7189A (at least, those from companies that made 7189s), so treat them accordingly.In this specific instance, the 6L6WGB/5881 spec is a little different - a 6L6GC is electrically 100% compatible, but it's a different form factor. So Sylvania (later Philips ECG) just bottled the GC guts (which were also 7581A guts) in the small bottle.They do sound different, and probably can't run as hot - due to the heat transfer characteristics of the smaller envelope - but they can handle the same operating parameters.FWIW I have some Sylvania JAN 5881s from 1980, and they are identical to the later '80s Philips WGBs, with the exception of a grid cooling fin on top of the top mica. So there might be some other minor detail differences.Unless you turn your amp up to power tube-clipping volumes, I doubt you'd hear much of a difference between WGBs and 7581As. In something like a Marshall or a Bassman, the difference is more pronounced.FWIW, I find that the J/J 6L6 sounds a lot like the 7581A, albeit at a much lower lifespan (and cost).7027A will work as an option. They are a 6L6 variant.The socket pins 1 and 8 should not be connected in order to use the 7027A.This is not exactly true. For use with 7027s, pins 1 and 6 can't be connected to *anything*. Which renders the amp incapable of also using EL34s.Since 7027s are more expensive than just about any 6L6, I don't see much sense in going down that path.5881 are an option too"Real" 5881s will handle the voltages in his amp, but they'll need to be biased differently since they aren't 30W tubes. And they'll sound different.
edgar_allan_poe Posted February 22, 2008 Author Posted February 22, 2008 Thanks Admiral...The amp I will be putting these into is my Fargen Bordeaux. I have several quads of 7581As that I am reserving for my Roadking. I will get the WGBs for around $125 a quad and just rebias my Fargen.
JohnnyB Posted February 22, 2008 Posted February 22, 2008 My experience with Philips JAN NOS tubes is limited to the 12AX7WA, but it is very positive--great build quality, great, musical, liquid sound.
edgar_allan_poe Posted February 22, 2008 Author Posted February 22, 2008 Yeah...I have had them before. I am just wondering how close these will be to the 7581A in the tone department. I love the headroom and the walloping low end that the 7581A delivers. I realize that the headroom will be significantly diminished with the WGB but I am hoping that they have the same sonic characteristics.I have a few quads of NOS Tung-Sols but I am not sure if I want to use them yet.
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