[Nic Rhodes]

There is a very good article on these dissimilar triodes in Vacuum Tube Valley. A gold mine of potential that few have exploited so far.

 

[2359glenn]

  There is a very good article on these dissimilar triodes in Vacuum Tube Valley. A gold mine of potential that few have exploited so far.

The problem is that I never found one that really sounds that good. I tried using a 6DN7 to drive a 300B because a 6SN7 can't
really do it right. But could never got a good one Then I switched to a #10 now use C3g as the driver.

 

[Nic Rhodes]

The 300b tube is never easy to drive which is why many people use 5687 / C3gs / smaller power triodes etc to do it properly. The 6DN7 and other dissimilar tubes have many other uses and have a firm following in small amps / headphone amps though their use originally was driven by tvs. Heathkit I think uses them in the 60s  in ham radio transmitters and more recently Bottlehead S.E.X. kits. I have used them to drive transformers in a RF driven 300B but this is not what I would consider  first for driving a 300b, personally I like 3A/167Ms. Interstingly this is a US only style of valve, the UK and European did virtually non of these prefering ECL type valves (ala ECL83 used in headphone amps here in the UK). The dissimilar triodes I think work really well in the Woo 6 series. The 6SN7GT is a lovely valve, just not one I would use for a 300b amp driving it directly a la Woo.

 

[Skylab]

If you can find them, if you know of a source i would be interested and the last time i saw some they where at least$20.00 each and that was about a month ago .they are hard to find unfortunately

I have lots of the fat bottle 6FD7 I would be happy to sell for $5 per tube plus shipping...anyone wanting some can PM me.

 

[2359glenn]

  The 300b tube is never easy to drive which is why many people use 5687 / C3gs / smaller power triodes etc to do it properly. The 6DN7 and other dissimilar tubes have many other uses and have a firm following in small amps / headphone amps though their use originally was driven by tvs. Heathkit I think uses them in the 60s  in ham radio transmitters and more recently Bottlehead S.E.X. kits. I have used them to drive transformers in a RF driven 300B but this is not what I would consider  first for driving a 300b, personally I like 3A/167Ms. Interstingly this is a US only style of valve, the UK and European did virtually non of these prefering ECL type valves (ala ECL83 used in headphone amps here in the UK). The dissimilar triodes I think work really well in the Woo 6 series. The 6SN7GT is a lovely valve, just not one I would use for a 300b amp driving it directly a la Woo.

Dissimilar triodes were extensively used as vertical oscillator and vertical output in US made TVs
Before Woo started using them they could be had for $1
The biggest use for 6SN7s in US was vertical and horizontal oscillator in older US TVs I even seen 7N7s used for this.
Then switched to the more modern 6CG7/6FQ7 really the same tube just in a 9 pin mini tube 
But 6SN7s were also used in amplifiers as phase inverter and driver for push pull pentodes in high power amps. 

 

[Nic Rhodes]

Yes I know that Glenn,after the Octals came the novals and then the Compactrons. We also had larger bottles, all of which used to go for pennies, nowday post Woo 6s, getting fat bottle 6FD7 is much more difficult for people (take up Skylab kind offer if you need them Mike). The price is also much higher and the available quantity significantly reduced (although some of us stocked up when you could hardly give these things away ). Woo now sell pairs of fat bottle 6FD7 at $52, probably bought at $2. You have to admire that as a business model, build a demand from nothing and have plenty of supply to exploit.

 

[SoundApprentice]

By any chance does anyone have any 7N7 to 6SN7 adapters they aren't using? I'm looking for 1 or a pair. 

 

[musicman59]

  By any chance does anyone have any 7N7 to 6SN7 adapters they aren't using? I'm looking for 1 or a pair. 

Contact Gelnn. He just made a pair for me.

 

[IndieGradoFan]

I've been experiencing a strange issue with my WA22 that I *think* I've narrowed down to my 6SN7 tubes.
 
I've been experiencing sudden drops in volume on the left channel about once per day (avg 6h sessions). Enough of a drop to make the right channel over power left channel. The first few times it happened, it seemed to be correlated with static electricity from dragging the headphone cable over the carpet.
 
On two occasions, the balance was eventually restored by the right channel reducing in volume too -- to the point where I was running the amp about 2 "hours" higher on the volume dial than normal. Most other occasions, the left channel gradually increases in volume over a period of a few minutes -- slow enough that I don't notice it increase in volume and then I'll notice the balance has been restored.
 
I've experienced this with different rectifiers (Sophia 274B, Brimar 5Z4GY), different power tubes (TS7236, Chatham 2399), and different headphone cables. The only constants are my LCD-X and Sophia 6SN7s. I haven't experienced the problem with the LCD-Xs on my Mjolnir.
 
Finally, I swapped the Sophia 6SN7s and today the problem occurred again, though this time it was the right channel. I quickly powered off the amp and replaced the Sophias with CV181 BTs and the right channel was now *louder* than the left. Swapped CV181s again and the right channel was still louder. I then powered off the WA22 for a few minutes, powered it back on, with the CV181s still, and I've had no issues since.
 
The Sophia 6SN7s have a few hundred hours on them. Same with the CV181s.
 
My current theory is that one of the Sophias was going bad and that the imbalance I heard after switching to the CV181s was due to some residual charge in a biasing capacitor. Plausible?

 

[SoundEngineer]

I am sorry to just jump in the discussion and change a subject.  But there is this burning question that I need help.
 
I have Little Dot MK VI+ and it can use 6sn7 and 6sl7 as driver.  I really want to use C3G as driver.  Is there an adapter or some way to accomplish this?  Is this even possible?
 
Any help would be appreciated.

 

[gibosi]

  I am sorry to just jump in the discussion and change a subject.  But there is this burning question that I need help.
 
I have Little Dot MK VI+ and it can use 6sn7 and 6sl7 as driver.  I really want to use C3G as driver.  Is there an adapter or some way to accomplish this?  Is this even possible?
 
Any help would be appreciated.

 
Yes, it is possible. But to do so requires a custom adapter to connect two C3gs into one 6SL7 socket. This adapter must accomplish two functions. First, since the C3g is a pentode, it will have to convert the C3Gs into triodes. And second, the adapter will have to reroute the cathode, grid and plate of each CG3 to the appropriate pins in the 6SL7 socket as well as the heaters.
 
As an example, it might look similar to this 6J5 to 6SN7 adapter, but with loctal sockets on top, instead of octal.
 
http://www.ebay.com/itm/1x-6J5-6J5-to-6SN7-Vacuum-tube-adapter-socket-converter-02-/301539001598?
 
If you are not up to building one of these yourself, you might want to contact one of the eBay vendors who build various adapters and ask if they would be willing to build one for you. In response to just such a request, at least two different vendors have built C3g to 6AK5 adapters for the Little Dot 1+. II, III and IV.
 
Cheers!
 
Edit: I have no idea how a C3G will sound in a circuit designed around the 6SL7. So if you decide to give this a try, please let us know how it turned out.

 

[SoundEngineer]

   
Yes, it is possible. But to do so requires a custom adapter to connect two C3gs into one 6SL7 socket. This adapter must accomplish two functions. First, since the C3g is a pentode, it will have to convert the C3Gs into triodes. And second, the adapter will have to reroute the cathode, grid and plate of each CG3 to the appropriate pins in the 6SL7 socket as well as the heaters.
 
As an example, it might look similar to this 6J5 to 6SN7 adapter, but with loctal sockets on top, instead of octal.
 
http://www.ebay.com/itm/1x-6J5-6J5-to-6SN7-Vacuum-tube-adapter-socket-converter-02-/301539001598?
 
If you are not up to building one of these yourself, you might want to contact one of the eBay vendors who build various adapters and ask if they would be willing to build one for you. In response to just such a request, at least two different vendors have built C3g to 6AK5 adapters for the Little Dot 1+. II, III and IV.
 
Cheers!
 
Edit: I have no idea how a C3G will sound in a circuit designed around the 6SL7. So if you decide to give this a try, please let us know how it turned out.

gibosi,
 
Thank you so much for letting me know what direction I need to be heading.  I will definitely either build or buy the adapter to try C3g on 6SN7 or 6SL7 circuit design and let you know how it sounds.
 
My hope is that C3g S will blow away all the 6sn7 and 6sl7 tubes.  I am looking for the "END GAME" tube and I think C3g might be it.
 
I will let you know.  May be I can let your hear the differences instead of telling you what my subjective impressions are.
 
BTW, I was thinking about working on a little project.  I am not sure if someone else already has done this...if so please let me know.  I am trying to create a library of 6sn7 tube sound samples with different power tube combinations.  Like a comparison chart with frequency response and music sounds from the tubes.  I don't have too many of 6sn7s right now but I am building my collection slowly.  I am planning to use my MK VI+ balanced preamp output to a balanced recording device with lossless format 24bit 96kHz.  I will play a same music with different tubes so the listener can hear the difference between the tubes.
Something like this but with 6sn7 tubes instead of headphones:
 
https://www.youtube.com/watch?v=6XSbtDgMxEY
skip to 1:47
 
I am very new to tube amps (just got into it around 4 months ago). I was buying tubes based on what people say and how good it is.There are not too many places where I can demo tubes for me.  But if you can hear the differences like dynamics, warmth/bright/dark,details, and high/mid/low frequency response of a tube it can give someone some sort of idea/hint of what to expect from a particular tube that he/she might be interested.  Right now I own Full Music 6sn7 "B" grade, Psvane cv181-tii "A" grade, russian 6h9c (stock tube for MK VI+), and tung-sol 6sn7gt.  I bought all these tubes without listening to them.  All four tubes are very different and Psvane cv181 is the most dynamic and Full Music is the most detailed of all four.  And you can totally tell the difference between the tubes with the music I recorded between all four tubes.  I have been making my own CD by playing my favorite music through the MK VI+ and rerecord the sound refined by the driver tubes then burn the audio CD so i can listen in my car just to listen and compare the different characteristics of the tubes.  I am just doing this out of curiosity and help people who are new to tubes like me. So it's not going to be professional quality like Sonicsense.com who are doing it to help their business.
 
So if I succeed in getting C3g to work with 6sn7/6sl7 circuitry...I will upload the samples for you so you can be the judge instead of just wonder if it really sounds as good as or bad as my subjective impression says.

 

[Xcalibur255]

In a circuit that wasn't designed for the C3g it's anybody's guess what kind of results you are going to get.  The tube might end up with less than ideal biasing.  Properly driven the C3g is as close to "soundless" as a driver as I have heard in terms of coloration or deviation from neutral.  It has little in the way of a signature you could describe with words like "warm" or such.  What it will do is make more obvious the coloration of any tubes downstream from it, for better or worse.

 

[SoundEngineer]

  In a circuit that wasn't designed for the C3g it's anybody's guess what kind of results you are going to get.  The tube might end up with less than ideal biasing.  Properly driven the C3g is as close to "soundless" as a driver as I have heard in terms of coloration or deviation from neutral.  It has little in the way of a signature you could describe with words like "warm" or such.  What it will do is make more obvious the coloration of any tubes downstream from it, for better or worse.

Thank you so much for clearing this up about the C3g's characteristic.  So hypothetically if you had a hybrid tube amp (tube preamp and solid state power output) with C3g properly driven...it would just sound like a SS amp with good preamp, right?  Basically it will be "soundless" or add any tube color so you will be listening to the sound that is closest to how it was originally recorded, right?

 

[gibosi]

  Thank you so much for clearing this up about the C3g's characteristic.  So hypothetically if you had a hybrid tube amp (tube preamp and solid state power output) with C3g properly driven...it would just sound like a SS amp with good preamp, right?  Basically it will be "soundless" or add any tube color so you will be listening to the sound that is closest to how it was originally recorded, right?

 
I have a hybrid tube amp, the Little Dot 1+, which allows rolling of op-amps. To my ears, at least, there is a significant difference in the sound of SS op-amps. Aside from differences in tonality, some with more more bass and warmth and some with more air, they also differ in terms of wetness and dryness as well as liquidity and grain.
 
Further, using various pin-adapters, I run both C3gs and 6SN7s in the 1+. It is likely that neither of these tubes is biased properly given the amp was designed to use triode-strapped 6AK5s. And of course there are other variables, such as sources, headphones, ears and brains. Given these qualifications, in my system, the C3g is not better than a Sylvania 6SN7W, for example, it is just different. The best I can say is that given my ears and gear and mood I might prefer one or the other. And I am not sure I believe that there is such a thing as an "END GAME" tube, at least for me.
 
Even if one has an amp that can bias both the C3G and the 6SN7 properly, it is likely that one might prefer the C3G with one combination of rectifier, powertubes and headphones, and a 6SN7 with another combination. Fortunately, soon I will be able to test this a bit further as I am expecting the delivery of a just such an amp in the coming weeks.