Tube Testers

[KindaFuzzy]

I've got an old Stark 9-66 which is pretty good for transconductance readings, and then if I have to match power tubes, I do it in a working amp, and standardize the current readings against the readings on tubes from the tube store.

[martin manning]

Looked at the Tube IMP, and the detailed review from Audio Xpress. Per the description, it is similar to the S Bench design, but is limited to 200V and 10 mA. Currently priced at $615. Seems like a high price for a tester that is limited to the more popular noval preamp tubes.

[selloutrr]

I have used the MaxiMatcher power tube tester and the VTV Dual Triode Characterizer, as they called it, for years. Sadly the VTV is no longer made. Neither are exactly cheap, but both are reliable.

The VTV is no longer made? Ouch. I have one and it is quite indespensible.

Really? I was under the impression they improved the power supply and where going to start making them with the new power supply standard.

I'm sure you can still get one .. money talks.

[David Root]

I could be wrong on that---I haven't checked their website lately, as I already have one, and their NOS tube prices are wishful thinking as far as I'm concerned!

[martin manning]

Looks like VTV is out of business. Owner C Kittleson passed away in February of this year, and the fire went out, it seems.

[selloutrr]

Sad

[Ian444]

Ian, the S bench gm/mu tester (see http://greygum.net/sbench/sbench101/) is similar to what you are describing, but it has an adjustable DC supply for the filament voltage, a constant current supply for the cathode, and it lets the grid float. Dynamic parameter gm is measured at constant plate voltage, mu at constant current, and you calculate ra as the ratio of those two. Any operating point (up to 300V and 50 mA) can be dialed in as you suggest, and the static grid voltage compared to the data sheet. I'm guessing with all new parts ~$200 to construct a nice one.

I have looked into the Steve Bench tester a year or two ago, I remember it as looking like a really great piece of gear. If that's the way you want to go, it would be an excellent piece of test equipment. Doesn't look too difficult to build. I say go for it!

The limit of 300V plate voltage, I don't know if that is a worry or not.

[martin manning]

I have looked into the Steve Bench tester a year or two ago, I remember it as looking like a really great piece of gear. If that's the way you want to go, it would be an excellent piece of test equipment. Doesn't look too difficult to build. I say go for it!

The limit of 300V plate voltage, I don't know if that is a worry or not.

250V is pretty much a standard reference voltage on power tube data sheets, so I don't think that is problem. Yea, it does seem like a very good option compared to the alternatives, old or new.