tube lab

We take a more in depth look at what is becoming a very popular tube.
Link to our online store: valvesnmore.com/
Link to Mellow Tone Kits: valvesnmore.com/?page_id=13253

[@sopasadena1499]

Informative video. Are 6bq7 or 6bz7 tubes acceptable or good substitutes for the 6dj8?

[@tubelab194]

We have a lot of the 6bq7/6bz7 (maybe 1k) and hope to use them one day in a Kit Amp. Yes they are close electrically to the 6dj8 and most likely will work. What we found is they test inconsistantly, in our case we have so many matching up pairs wouldn't be a problem, but if you only have 10 or 12, there's little chance you'll find a close matched pair. Also Caution the 6bq7 has a lower max plate voltage of 300v vs 330v for the 6dj8. Given that we currently have in stock NOS NIB (new old stock, new in box) mil spec Sylvania 6922 (premium 6dj8) it would make more sense to use the best tube and they're currently on Sale!

[@iampuzzleman282]

Any videos where you explain what goes on inside the glass enclosure of the tube?

[@tubelab194]

Absolutely, scattered over the years and as well on our other channel "mellow tone kits", whenever we're explaining how a circuit works. There also some excellent historical videos made by companies like RCA. To find those just google "how a vacuum tube operates". Once you've seen one, they're all exactly the same. In fact all tubes basically operate the same way with only variations on the original technology.

[@sopasadena1499]

Really get a lot out of your tube videos and the musical selections when present are great. I have a Freya N preamp and confirm that Holland made ecc88 tubes sound best IMO. What are your favorite 6cg7 tubes as less expensive substitutes?

[@tubelab194]

I like all the 6cg7 and their close cousin 6gu7, but my fav is RCA clear top and Japan made versions. We have a good customer who is a dedicated audiophile and she just bought 4 spare Japan 6cg7's to make sure she never runs out!

[@sopasadena1499]

Interestingly I just picked up a single Realistic Japan 6cg7 and it sounds wonderful as good or better than the RCA clear tops. Looking for another nos one but that may be tough

[@leonardo.rafael]

@tubelab194 do you know the 7 pin GZ81 rectifier of the 1950’s please ? It was used in small amps and radios.

[@tubelab194]

No not at all, in fact we can't even find a data sheet. Why are you wasting your time with this rectifier. Even if it exists it's not common. Focus on more commonly available rectifiers.

[@frankgeeraerts6243]

7 pin rectidiers ..........you can maybe substitute for a 6X4...check voltages and pin out ! I never saw a GZ81...? Maybe you ment an EZ81/6CA4 ? ( nine pin used commonly in many radios and amplifiers .)