Dennis Had Inspire Amps

[Analog Addict]

A sample of the new schwag that will soon be included with every Inspire purchase. OK I got the sample because the logo was printed crooked, but once the final run is done, one will be included with every Inspire purchase.

Stand apart from all the Luddites! Show the Philistines surrounding you that you know the true meaning of audio bliss!!!



Untitled by analog addict, on Flickr

[FloridaBoy]

Stand apart from all the Luddites! Show the Philistines surrounding you that you know the true meaning of audio bliss!!!



Let the Philistines eat their sand amps.

[Analog Addict]

Well, would anyone be surprised if I said there was another goodie coming out of the Inspire Toy Shop? Talk about hot off the press, Dennis just texted me, Straitwire and Bear City about a new development on the KT 88 SEP Fire Bottle amp.

Here's the text....

"Fellas, have a look at a really great new feature of the Inspire KT88 SEP. I call it the Current Matcher/Tester. Simply plug in the 1/4” three circuit jack and hook the green lead to negative and the red (right channel) or white (left channel) to the positive of your DVM meter and measure the plate current of each individual output tube. Great when matching up various tube rolling tubes. Simply divide the DC voltage shown on the meter by 360 (auto bias resistance value) and this is the plate current.

Example with the KT88 … 21.06 divided by 360= .0585 = 58 ma. Plate current.

Do the same with the KT170’s … 23.56 divided by 360= .065 … 65 ma. Plate current. Some other measurements … 6V6 14V, 6F6G 15V, 6L6 17V.

Now no guessing if you have matching tubes or if one has a defective tube.
Dennis"

Untitled by analog addict, on Flickr


Untitled by analog addict, on Flickr


Untitled by analog addict, on Flickr


Of course, that being said, you do need to know what plate current is and what the appropriate values of plate current are for each type of tube, but I would expect most of you crazed Inspirophiles out there should be able to figger out where to find this info...

You heard it here first.....

[Leew]

Does it work with one socket? Do you switch tubes to check both?

Scratch that I actually read it instead of looking at pictures.

PS. Any word on the phono pre?

Thanks,
Lee

[straitwire]

Hey Leew, I'm still waiting on chassis for the phono preamp.
Everything costs more and takes longer to get these days.

[Isaacc7]

What is the impact of mismatched tubes in single ended amps? Could they be far enough out to cause one side to be louder than the other? If so, wouldn’t a balance control fix that?

[Analog Addict]

If I remember correctly, if it's one tube per channel, essentially none, except for differing tube life times. If it's a parallel single ended amp with more than one tube per channel it depends on how each channel is set up.

If a cathode bias scheme is used and each tube has it's own filament transformer, than same as the single tube per channel set up.

If multiple tubes are running on one filament transformer, then mismatched tubes will generally wear at unequal rates.

This is my experience and (limited) conceptual understanding.

[FloridaBoy]

Originally Posted by Isaacc7

What is the impact of mismatched tubes in single ended amps? Could they be far enough out to cause one side to be louder than the other? If so, wouldn’t a balance control fix that?

The answer is buried in this thread. As I recall, in a two power tube Inspire amp, the auto-biasing precludes the necessity of precise power tube matching. A good strong pair is all you need.

[Isaacc7]

Lots of good info's buried in this thread. Hope more folks post different topics in this forum instead of adding to this one thread.

So two people have echoed what I have heard before. With the Firebottle KT88 it doesn't sound like matching is all that important.

[Kris0603]

Life with my KT88 SEP goes on, and i finally got some adapters for some 5933WA tubes and promptly slotted them in. Works great.

(Please ignore the dust, and that the internal construction differs)