Dennis Had Inspire Amps

[Isaacc7]

Originally Posted by Analog Addict

A text from Dennis a few minutes ago after i asked him the difference between the performance of the 6GK6 and the 6BQ5…

Since the 6GK6 inner structure (lower electrode capacitance) are designed to be used in low power RF driver circuits it reveals a difference in midrange clarity and a lack of that tubby bass found in many of the 6BQ5/EL84 amp signatures. So all in all the 6GK6 tube, audio signature is a refreshing, clean realistic midrange presentation vs the darker tubby EL84 offering. So as I mentioned earlier, I will return your bucket of bolts, 6GK6 amplifier in June or July!!!!

Guess he must like it....


He also said this…

Yep, I’m puttin u on notice .. a mighty Inspire 6GK6’er will be commin soon old man!!!!

Now I gotta convince him to build a 6GK6 PSE…

I also had always heard that the 6bq5 and 6gk6 were equivalents with different pin outs but are there any that are built the same way? Have you been able to compare a 6bq5 and 6gk6 that are physically identical? In other words, is what Dennis is hearing the equivalent of tube rolling? Different 6bq5 tubes sound different from each other, wouldn’t surprise me if an “equivalent” 6kg6 sounds different just cause it’s a different 6bq5. Which 6gk6 do you have in your amp?

I have gone back to trying 6bg6ga tubes in my KT88 Firebottle. There is a world of difference between the 2 different GE models, the RCA, and the Sylvania despite them all being the same tube type. I have a variety of 807 tubes from Sylvania, Mazda, Mullard, and Russian and they all sound different. Add on to those 807 “equivalent” tubes like vt60a and 5b/254m also sounding different and I am convinced that electrical equivalence does not translate to sonic equivalence.

I love tube rolling, it’s like having a bunch of different systems! Why have one stereo system when you could have hundreds lol.

[Analog Addict]

Originally Posted by Isaacc7

I also had always heard that the 6bq5 and 6gk6 were equivalents with different pin outs but are there any that are built the same way? Have you been able to compare a 6bq5 and 6gk6 that are physically identical? In other words, is what Dennis is hearing the equivalent of tube rolling? Different 6bq5 tubes sound different from each other, wouldn’t surprise me if an “equivalent” 6kg6 sounds different just cause it’s a different 6bq5. Which 6gk6 do you have in your amp?

I left my 6GK6 amp with Dennis last week running RCA black plates, which physically look identical to their 6BQ5 counterparts. (See lowest group of four in the picture below)

If you go to the Duncan TDSL (Tube Data Sheet Locator) and compare the two tubes, the only significant differences you will notice are the direct electrode capacitances, especially that of grid 1 to the plate. These are much lower than in the 6BQ5. Dennis said that the 6GK6 was designed to be used in low power radio frequency driver circuits, allowing for potential improved clarity in audio frequencies.

I'll have to ask Dennis how these capacitances affect audio frequency reproduction and see what he says.

Untitled by analog addict, on Flickr


As for the variants, here is my 6GK6 stash, which has been sitting around, unloved for over a decade. If you look carefully, you will see Matsushita, Raytheon, Sylvania, RCA, GE and so on. One thing I haven't come across yet are Phillips/Valvo versions, which I am actively looking for at this time.

[cgn-dt-n]

PAIR 6GK6 Tubes Philips Vacuum Power Output Drake Swan Berning - Used Test NOS

Verkäufer: thetuberoom aus Kanada

PhilipsECG 6GK6 tube (NOS)

Seller: phonocollection aus Deutschland
but only one single

gerade aktuell auf ebay

[Analog Addict]

Originally Posted by cgn-dt-n

PAIR 6GK6 Tubes Philips Vacuum Power Output Drake Swan Berning - Used Test NOS

Verkäufer: thetuberoom aus Kanada

Vielen Dank! Ich habe diese gerade noch gekauft.

On the way. $24 shipped with tax from Canada. When was the last time someone bought a pair of similar 6BQ5s for this price?

[Isaacc7]

Originally Posted by Analog Addict

I left my 6GK6 amp with Dennis last week running RCA black plates, which physically look identical to their 6BQ5 counterparts. (See lowest group of four in the picture below)

If you go to the Duncan TDSL (Tube Data Sheet Locator) and compare the two tubes, the only significant differences you will notice are the direct electrode capacitances, especially that of grid 1 to the plate. These are much lower than in the 6BQ5. Dennis said that the 6GK6 was designed to be used in low power radio frequency driver circuits, allowing for potential improved clarity in audio frequencies.

I'll have to ask Dennis how these capacitances affect audio frequency reproduction and see what he says.

Untitled by analog addict, on Flickr


As for the variants, here is my 6GK6 stash, which has been sitting around, unloved for over a decade. If you look carefully, you will see Matsushita, Raytheon, Sylvania, RCA, GE and so on. One thing I haven't come across yet are Phillips/Valvo versions, which I am actively looking for at this time.

My GE 16gk6 look like yours. I don’t see any that look the same as the Mullard (sometimes labeled GE) or Telefunken el84. Cool to know your RCAs look the same. Of course some important stuff could be hidden from view I guess. I’ve always wondered how much the shape of the plate affects the sound. I have some GEC e3375 which aside from the top cap are dead ringers for the GEC kt77. I’m never going to be able to afford actual, original KT77 but I’d love to compare them. Apparently the e3375 biases like the el38, not the el34 so there is something different.

[Analog Addict]

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

[Showme]

Allan and as they say “the rest is history”. Congrats on what must be a nice amp.

[Analog Addict]

Originally Posted by Showme

Allan and as they say “the rest is history”. Congrats on what must be a nice amp.

Thanks! I have a very good teacher...

Hopefully we can soon share the experience with the world at large...

[Isaacc7]

Originally Posted by Analog Addict

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

I've had a similar experience with my Firebottle. I recently had a push pull amp made for me. It's an amazing amp, one of the best I've heard. Compared to my Firebottle it is more open, more detailed, has better bass, and a deeper soundstage. And yet...

There is something special about the KT88 Firebottle. It's hard to put my finger on it but there seems to be magic in that amp. It is far less fussy and far easier to get great sound out of it. The PP amp requires just the right tube combo and settings to be all it can be whereas the Firebottle usually sounds very good with whatever I put in it. I'm picky of course so I still roll tubes

I'm glad to have both of these amps. I consider myself an audio hobbyist as well as a music lover. The PP amp is better suited for looking into the mix and picking up the particulars of a performance/instrument/performer. I think the Firebottle allows me to sink into the music easier. Add tube rolling to the equation and I have a vast number of flavors I can dial in.

[Isaacc7]

As I mentioned earlier, I had a PP amp made for me and my, uh, unorthodox wants in an amp. Tomas at Ultrasonic Studios made a beautiful, fantastic sounding amp for me all the while catering to my audiophile whims.

I had pitched Dennis on the idea of making me an amp like the one I have now for lower wattage tubes but with features like using external heater supplies, combo 6j5/6n7 inputs, etc. Unsurprisingly he turned me down. He isn't a boutique manufacturer, he's an auteur following his own mad scientist methods. No biggie, I'll just get Tomas to make it for me. Alas, he passed away in February. All of us in the Ultrasonic Studios forum are still in shock at his passing. He was only 40! What a tragic loss...

And this brings me to the reason I'm posting all this stuff about another builder and company. I regret not thanking Tomas for how he enriched my life and how his creation continues to bring me joy. Dennis, I want you to know you have made the world a better place by making all of our lives more enjoyable. Even small pebbles make ripples and the decades you have spent making music lovers happy means there are an almost never ending waves of positivity because of your efforts.

Anyway, enough maudlin sentiment. Stay tuned for more tube rolling adventures from me