I'd be happy to check your tube for you. I have a calibrated Hickok 533 mutual conductance tester, and plenty of Inspire designs to do a real world test. I'lll send you my snail mail addy in a PM and we'll get you squared away...:thumbsup:

Awesome, thanks!

Great activity in the last week.
Tube rolling in Pre.
New finding: the CJ5 reacts much more strongly to different tubes than the 2030.
With the CJ5 it is possible to change the sound in different ways in all directions and to find a perfect result for the respective set up.
The 2030 hardly rules on the different tubes. Only subtle changes can be heard.
Phillips' 509 and a one pair Cunningham 301s seem to have a problem. They sound softer, with beautiful voices, but lack control and contour in the bass range.
I think they are at almost the end of their lifespan.
71 and 171 should actually be the same tubes in different designs, but the stage with the Ken Rad 71a is a little smaller and she plays with less volume. Neither of them are my favorites.
The other pair of Cunningham 301 and the 01A of Sylvania and Silvertone play at the same level, here is almost no difference to be heard. For me the best tubes in the Pre.
Cunningham's 112 plays very similar in size of the room and resolution, but timbres are slightly golden. slightly warmer, but not exaggerated. Very nice with voices and acoustic instruments.
The best alternative for me.
With the 0A3 I could not see any difference between Sylvania, the mil. version and the Orion GT.
In the case of rectification, the size of the room changed slightly. GE and Mullard very close to each other in terms of timbre and size of the image.
The EML makes the room slightly larger and airier, but without changing the size of instruments and voices. The instruments are all in the right place. Women's voices have the right volume that suits the body, and do not appear artificially enlarged. The control in the bass range is the same as with the other two rectifier tubes.

https://live.staticflickr.com/65535/...9e36761b_k.jpgIMG_20220924_122246 by cgn- dt-n, auf Flickr

https://live.staticflickr.com/65535/...c917a972_k.jpgIMG_20220924_122252 by cgn- dt-n, auf Flickr

I’ve got another great budget combo featuring the GE 6bg6ga. The brown base Sylvania 6sl7wgt gives back the top end that the much more expensive round plate tungsol 6/12sn7 lacked. The Tungsol does give a satisfyingly thick sound, this particular 6sl7 has a more balanced sound overall. The Sylvania tube is pretty easy to get for around $30. It is a pretty smooth sounding 6sl7 IMO. Some of them can get overly bright and glare but this particular combo is great.

I may have found my ideal tube combo
 

I have been cycling tons of tubes through my KT88 Firebottle, had a whole thread about some of my adventures. One output tube that I kept coming back to is the Cossor 807.

https://www.isaharr.com/wp-content/u.../IMG_0451.jpeg

https://www.isaharr.com/wp-content/u.../IMG_0453.jpeg

I have seen them labeled as GEC and Cossor, as 807, ATS25, and VT60. I have also seen them with a brown base instead of the ceramic.

In my system they are consistently the most open, spacious, and enjoyable of all the tubes I have tried. I have 807 tubes from Sylvania, Fivre, Mullard, Mazda, and Firenti. All of them sound good with the right combination off tubes but the Cossor always shine through for me. The accuracy of timbres and revealing quality is addictive. I use a 5u4gt rectifier either an RCA or Electro Harmonix, I can't tell any difference between them.

The input tube has a dramatic impact of course. My go to inout tube is the 14n7 clear glass. It has a very similar character to the Cossor tubes. The combo doesn't have any weaknesses tonally. Highs, mids, lows, are all where I want them. I believe the 14n7 isn't just the 12v version of their similar looking 7n7 or regular 6sn7. It sounds deeper and clearer than the other Sylvanias. I'm pretty sure it is the 12v version of the sought after metal base 6sn7w. I don't have one to compare sonically but they look the same to me, down to the copper support rod.

If I want to warm things up I can use the grey glass 14n7 or the MOV CV1102.

I never thought I'd say this but I think I'm done tube rolling with this amp! It sounds so so good! Ironically, I actually have another amp coming next month. This one isn't made by Dennis, had Thomas at Ultrasonic Studios make an amp to my demented specs. It is a push pull amp designed specifically around tube rolling. I'm going to keep my KT88 Firebottle as my single ended amp. have a feeling that the push pull simply won't sound the same. I have talked to Dennis about the possibility of another amp in the future but we will see...

Anyway, I'll keep checking in here to talk about these wonderful amps but don't be surprised if I become scarce next month when my new toy comes in lol.

FYI, if anyone is interested in trying the Cossor 807, the best prices I have found have been from Vintage Electronics https://www.vintage-electronics.co.u...alve-tube-nos/

Not affiliated of course but the prices on ebay were making me scratch my head. Know they were available at a more reasonable price. Still pretty good deal IMO, especially considering what new tubes and popular NOS go for.

Edit: Forgot the price, 45 Pounds.

Update:

Many thanks to Analog Addict for confirming my 5AR4 was DOA. The eBay seller has agreed to refund, so basically no harm done.

I finally got the next tube type on my list to test—the Gold Lion KT77 (New production). It does look pretty and at first blush, I seem to get both power/dynamics as well as transparency. Does anyone know the break-in time for this new production tube?

[IMG]https://live.staticflickr.com/65535/...689aaaf0d3.jpgGold Lion KT77, Sophia 274b, Sylvania GTB by Tube Dad, on Flickr[/IMG]

[IMG]https://live.staticflickr.com/65535/...a2515d1a16.jpgKT77 in the Dark by Tube Dad, on Flickr[/IMG]

I have heard plenty of good things about those tubes. Haven't tried them myself. I do really like their KT66. I'm not a big believer in long burn in times. My audio memory simply isn't good enough to reliably remember "the sound" from weeks ago. I do seem to recall that after a few days I thought they stopped changing. No idea how many hours that was.

Yea, that’s why I pulled the trigger—ton’s of good reviews as one of the best new production Gold Lion tubes out there. Upscale Audio (where I got it from) is recommending a 100 hr burn in based on feedback they have received from their customers. I have also heard at least 50 on one site. Seems like par for the course.

One idiotic thing I did is when I removed the RCA 807’s from their adapter, I forgot to first detach the top plate cover and with the force I applied, the top cap snapped the top plate cover right off. I can plop it back on but not sure if it’s safe to put it back on in the amp.

Oh man that sucks. I have 3 807 tubes with problem caps. 2 are loose and one came off completely. I'll glue the loose ones back on, that should be fine. The problem is that the wire coming out of the top of the tube is actually soldered. If the cap comes off that tells me that the solder joint was broken as well. I'm not sure if the remaining wire is long enough to resolder. My Cossor tubes are about $50 a piece so maybe worth trying to save but I'm not motivated enough to try right now. Not sure I would bother for less expensive tubes.