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In Reply to: RE: 7189 Singles and Pairs posted by geezerrocket on December 22, 2015 at 08:22:20
I mix and match input and output tubes. No problem... except for maybe aesthetics. Some ppl like all their tubes matched, even to the brand, vintage, and logos.
BTW... any luck finding good 7189A? For me, like hen's teeth...
8^)
Follow Ups:
7189A's are a little tougher to come by for sure.
If I come across any nice ones I will message you.
Are there any Russian equivalents to the 7189A?
Meat; It's the right thing to do. Romans 14:2
I have purchased from this seller before.....http://www.ebay.com/itm/7189-A-EL84-6BQ5-6n14n-EP-Russian-Mil-spec-7189-A-EL84-6BQ5-matched-quad-/331736844525?hash=item4d3d0e88ed:g:c34AAOSwFnFWEALt
That tube is the same as the current EL84M Sovtek, just older. They are good tubes, but in terms of durability they are no better than the EL84Ms.
Not that I know of, at least.
I don't know if your handy with a soldering iron or not. If so, take a look at this.
Meat; It's the right thing to do. Romans 14:2
Per the link you supplied:
"the 7189 is designed for circuits operating in the 400 volt range. The EL84/6BQ5 is designed for the 300 volt range."
My tube manuals confirm this. But I see LOTS of currently produced guitar amps that use EL84/6BQ5 and run them at 400 volts. In my experience, they seldom arc over internally, but they become microphonic prematurely.
Interesting. Problem is, the 7189A makes more power and can handle higher plate voltages than the 7189. So, the "fix" could only be temporary, in an amp that used the 7189A as OEM.
Fortunately, the Russian 6p14p-ev, AKA EL84M, is a very tough hombre. As it is "the only game in town", units originally set up for the 7189A have to be modified to take the available bottles. Rewire sockets, appropriately, and tweak the biasing to slightly reduce the stress placed on the tubes.
We are LUCKY to have the Saratov made variant. Without it, all sorts of equipment would be scrapped or cannibalized. What an unpleasant thought.
Eli D.
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