Sunn Septre Dating

[pocketchange]

My Septre amp tube chart says the power tubes are to be KT-88s. All the other Septres I've seen take 6550s. I also don't have that little slide-switch on the front panel. Anybody know if this is an earlier model of the Septre?

[JoeArthur]

KT-88s can be substituted for 6550s. 6650s were original tubes, KT-88 are not.

Check the markings on all of the transformers/chokes. If they are original they can closely date the amp within something like +/- six months or so.

[Soundmasterg]

Some of the early Sunn amps back then did come specced with Genelex KT88's instead of 6550's. At some point early on they switched to Tung-Sol 6550's because of supply and cost issues with the KT88's. The Dynaco Mk. 3's that the Sunn stuff was based on did come specced with KT88's. My '67 200S that I used to have came with Tung-Sol 6550's new. Either one will work, and the KT88 does have higher ratings, so it is a better tube to use, however modern KT88's probably don't have the same lofty ratings as the NOS ones so they are probably about hte same as using modern 6550's. Personally I really like the sound of the JJ KT88 in the Sunn amps and they hold up well.

You may find a little piece of paper with the assembler signature inside the chassis. There was one on my Sonic 1 and it dated it to 1970 and the signature of the person who assembled it or perhaps the one who inspected it.

[EdBass]

I have a letter sent to all Sunn authorized repair facilities announcing the switch from British KT88's to 6550 tubes manufactured by "GE and other manufacturers", citing the inconsistancy of KT88 supply and the sonic superiority of the 6550 tubes.

I read this to mean unfavorable exchange rates and premium pricing on the Genelex valves.

I don't remember the month exactly, I have the letter with my original schematics at a different home, but I think it's dated September, 1969.
I'll accurately amend this post when I get it in my hands, possibly scan it and post it, it's an interesting piece of Sunn trivia.
Also, I have a bone stock '70 Sceptre and it came with Tung-Sol 6550's.

I would imagine that pocketchange's Sceptre has a tube chart left over from before the switch.

Speaking of Genelex, has anybody tried the new Gold Lions?

[Isaac]

Pocketchange, the absence of the mid boost switch does mean that your is an older model.

[Soundmasterg]

Thats interesting that you have a letter alluding to the "better" sound of the 6550's. I talked to Conrad last night about it before I posted and he said it was strictly a supply and cost issue as to why they changed.

I don't know of anyone who has tried the new Genelex KT88's. I'm a dealer for New Sensor and can sell them if anyone is interested, but no one has asked about them yet, and I haven't tried them either. Most people seem to be happy with the JJ's or the EH KT88's, or even the Winged C's.

[JoeArthur]

Thats interesting that you have a letter alluding to the "better" sound of the 6550's. I talked to Conrad last night about it before I posted and he said it was strictly a supply and cost issue as to why they changed.

I don't know of anyone who has tried the new Genelex KT88's. I'm a dealer for New Sensor and can sell them if anyone is interested, but no one has asked about them yet, and I haven't tried them either. Most people seem to be happy with the JJ's or the EH KT88's, or even the Winged C's.

You really can't compare 6550s and KT-88s ignoring the quality of both tubes "back then" with the quality of both tube types today. And ignore bang for the buck between the tube types.

In the USA back then - no one wanted KT-88s to substitute for 6550s - the 6550 was "king" so to speak. I do agree with Conrad's judgement as it being a supply and cost issue. 6550s were simply  cheaper and easier to obtain.

Outside of the USA at the time it may have been different.

[EdBass]

Thats interesting that you have a letter alluding to the "better" sound of the 6550's. I talked to Conrad last night about it before I posted and he said it was strictly a supply and cost issue as to why they changed.

While I am a big fan of old 6550's, particularly GE's, IMO the original Genelex KT88 is the daddy.

Which is why I added

I read this to mean unfavorable exchange rates and premium pricing on the Genelex valves.

to my post.

I wouldn't expect that any company would announce a product switch by putting in writing that the replacement was not better than the original, but easier and cheaper for them to obtain.

I have price lists that illustrate that Sunn didn't drop the prices for 6550 amps.

I don't know of anyone who has tried the new Genelex KT88's. I'm a dealer for New Sensor and can sell them if anyone is interested, but no one has asked about them yet, and I haven't tried them either.

As a dealer, how could you not check them out and report to your fellow Sunn aficionados?
Send me a matched quad, I guarantee I'll put them in a 2000S and report back. Maybe you can get some business from the testimonial!

Most people seem to be happy with the JJ's or the EH KT88's, or even the Winged C's.

The old tubes are an entirely different animal. The new "Gold Lions" only caught my attention because they put out a great sales pitch, (reverse engineered instead of re-engineered, etc.)

And, they look like old ones!

That 1967 200S must be one rare bird.
Maybe a prototype for the impending '69 switch?

[Spectrum II]

I still have the Sunn stamped KT88's that were in my head when I got it. That was the sound that made me bring it home (a wise move for $200, as I sold my Mesa 400+ for $875)...45 minutes into band practice the amp gave out on me, leading to a re-tube. I saved them 'cause I thought they were neat.

[Isaac]

I have a Sunn Concert PA head that has the original KT88s in it.

[Spectrum II]

Are the Sunn stamped ones Genelex, then?

[Soundmasterg]

Yah the Genelex products as a whole were just a step above everyone else, even back then, but the GE 6550A's were really nice too, as were the Tung-Sols.

I am a dealer for New Sensor and can get any of the Sovtek/EH/Tung-Sol/Mullard/Genelex stuff, but there are so many good brands out there today in 6550/KT88 types that I can't check them all for myself, and since customers haven't asked, I haven't ordered any of the Genelex's. If I tried to stock everything I'd be broke in a hurry, so I only stock the ones that people ask for most often. Rather than resell a bunch of tubes retail, I'm more interested in producing amps and in repairing amps, which is where I concentrate my efforts. That said, the new Tung-Sol stuff is excellent on the whole, and they reverse engineered those, so if they reverse engineered the Genelex stuff too, then I'd guess they are probably excellent too. If you're interested in any of those tube types/brands I listed send me a PM and we can discuss pricing and availability.

When I talked to Conrad, he said the really early stuff used the KT88's and then the switch was made to 6550's, and he figured the change happened around '67. Maybe they made the change first, and then came out with the marketing later? It wouldn't surprise me.....a lot of the decisions back then seemed pretty haphazard looking back on it since I wasn't around back then to see firsthand. My '67 200S was bought from the original owner in the early 90's. He used the amp occasionally in his house until he sold it to me. All the tubes/caps/resistors were original, and the tolex and grillecloth on the head and cabinet were A+ condition. The speakers were the original JBL D140's and in nice shape. I sold it untouched except for replacing the power tubes with some JJ KT88's after having it for 3 years to get an SVT head which I still have. I've since picked up and restored/modified a 1970 Sonic 1 which is a 200S for all intensive purposes. I've got a 1968 2000S head too that I need to restore. One of these days I'm going to make a 2x15 cabinet or two for myself. I've got the JBL's already....

[JoeArthur]

I've since picked up and restored/modified a 1970 Sonic 1 which is a 200S for all intensive purposes.

I must be asleep. I stared at this sentence for the longest time. Then something clicked and I think I got it.  I just want to make sure:

"I've since picked up and restored/modified a 1970 Sonic 1 which is a 200S for all intents and purposes."

This is not a slam on grammar or spelling or none of that - I am just laughing out loud about myself!!

[Soundmasterg]

Yah, thats what I meant Joe.  I guess I failed that chapter in phonics.....