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Questions about tubes and gear that glows. FAQ

Ah ! the famous "Six busy Sevens" !

Capt. Z.,

Actually, I don't know the 6BZ7 or 6BQ7A types. As I've had to deal with some new types recently, I checked into the duncanamps tube data page on Triode Electronics:

http://tdsl.duncanamps.com/show.php?des=6BZ7

- and learned almost nothing except the pinout appears the same, but the Va of the 6922 is 90 while the 6BZ7 is 150. It appears the 6BZ7 and 6BQ7A are not listed as direct substitutes for 6DJ7- (perhaps you mean 6DJ8) or 6922. The two types seem electrically different in some ways,..

On Ebay there are a pile for sale at very modest prices:,

http://search.ebay.com/search/search.dll?from=R40&satitle=6bz7

-so if it works electrically in your headphone amp- and good ones were made, it might be interesting -these are $4 tubes rather than the $35 you might spend for a good 6922.

I bought a McIntosh MR67 recently and it has some types not used very often so I could buy NOS Telefunken, Mullard or Amperex for very reasonable prices- thanks to their not being commonly used. When a Telefunken anything is $10 NOS in the box- it's very comforting in one way- and disconcerting to learn that there will never be anymore of that type made! Even though I may not keep the MR67, I already have at least 2 NOS of any type that isn't made any longer.

I'm always a bit nervous about types and substitutions- I've never heard of the 6BZ7 as a substitute for 6922- and over the 20+ years I've been fussing with the 6DJ8 family, I've heard of people looking for any alternative that will allow them to use something else- preferably less expensive- 7DJ8s, PCC88s had a fad, and people often ask if the 6FQ7 will go.

The preamp tube fad now seems to be the 5751 substitute for 12AX7.

I would make sure- ask the maker - what tubes the preamp can use. Some kinds of gear- and their makers- seem to be more flexible than others for substitutions.

Cheers,

Bambi B


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