[JTbbb]

Here is how mine arrived!?

I wonder if those prices + vat were the prices in 1975/6? Would work out somewhere around £70 in today’s money!

 

[triod750]

This pair sold for £275 the other day. Bought new almost 50 years ago and never used. A lot of money for a pair of old tubes...

 

[Isaacc7]

Another reminder that tubes can sound very different depending on how they are run and used in an amp. I have been listening to some Sylvania 6bg6ga tubes in triode mode. These are the ones that have the guts of a 7027a in them. While running them in triode I was getting a rounded, sweet sound. Flipped the switch to ultralinear and it sounds like a completely different tube. I am now getting a much more open, cleaner sound with much more detail. That has resulted in a much deeper soundstage and the ability to hear things like the bodies of acoustic instruments resonating not just the sound of the strings vibrating. Same settings for b+ and bias. It’s like having two completely different tubes.

I haven’t seen any headphone amps that use ultralinear. I’m guessing the reason is that you wouldn’t really be able to roll different output types very well unless you could also make voltage adjustments. Still, it might be worth the limitation for sound like this. You could still roll input tubes probably. A 6l6gc in ultralinear sounds mighty fine and there are a bunch of different versions of it.

 

[Designsfx]

What exactly does “ultra linear” do in this case?

 

[Isaacc7]

What exactly does “ultra linear” do in this case?

Ultralinear is a kind of feedback that uses a special tap on the output transformer to dynamically adjust screen voltage in relation to the signal. Like all kinds of negative feedback it reduces distortions. In an ideal world it would give you the low distortion and output impedance of triode mode but maintain all the power of pentode mode. In reality the results can vary. If you run a tube in pentode mode the anode and grid have completely different voltage signals. In triode mode they are tied together so they share the load. Ultralinear is between those two with a percentage going to the screen. https://en.wikipedia.org/wiki/Ultra-linear

What I inevitably notice going to ultralinear is a general clearing up of the sound. More detail that leads to better depth and a cleaner sound. What I prefer changes from day to day lol.

 

[Designsfx]

Without totally derailing the thread does your amp provide multiple tap points in order to optimize the type of tube you’re using or just one?

 

[Isaacc7]

Without totally derailing the thread does your amp provide multiple tap points in order to optimize the type of tube you’re using or just one?

I can either run the tube in triode or ultralinear and either 4 or 8 ohm outputs. In addition I can adjust the b+ and bias as well. Pretty sure the transformers are set to 40% for the ultralinear tap.

 

[Isaacc7]

Have spent the last week using both the cv4062 and n78 tubes in my single ended pentode amp. They use the same adapters but I can’t get a good feel for how different they are by looking at the spec sheets. In any case, using a MOV b36 driver I found the cv4062 to be very clear but lightweight sounding. I had a little better bass with some other input tubes but they all had an upper midrange glare. It was kind of exciting sounding with metal stringed instruments but it did get on my nerves eventually.

The N78 is a much better fit in my system. Using the same B36 it gives a much more well rounded sound. It has most of the clarity that he cv4062 but without the glare plus bass. According the to spec sheet the n78 can handle more voltage than the cv4062. I’ll be interested to hear what these tubes sound like in my push pull amp. I have quite a bit of flexibility with operating points with that amp so hopefully I can dial them in.

 

[UntilThen]

It's been a week now since I have been using the GEC 807 ATS25. Where EL34 midrange sound a bit scooped, 807 like 6L6 midrange is front and centre. This tube sounds as good as my other vintage tubes, if not better. One of the best texture in the game. A very caressing and relaxing tone. So impressed I am with it, I've ordered the VT60 version as well. Just to see if they sound the same.

Using it with GEC A2900 driver here.

 

[Isaacc7]

It's been a week now since I have been using the GEC 807 ATS25. Where EL34 midrange sound a bit scooped, 807 like 6L6 midrange is front and centre. This tube sounds as good as my other vintage tubes, if not better. One of the best texture in the game. A very caressing and relaxing tone. So impressed I am with it, I've ordered the VT60 version as well. Just to see if they sound the same.

Using it with GEC A2900 driver here.

The VT60 don’t sound like any other 807 I have. The vt60 sounds noticeably more open and detailed in both of my amps. It can be an unforgiving tube although paradoxically they seem to work very well with another super detailed and open tube, the c3m. Different amps, different circuits, etc. but the vt60 is one of my favorite tubes.

 

[UntilThen]

The VT60 don’t sound like any other 807 I have. The vt60 sounds noticeably more open and detailed in both of my amps. It can be an unforgiving tube although paradoxically they seem to work very well with another super detailed and open tube, the c3m. Different amps, different circuits, etc. but the vt60 is one of my favorite tubes.

And I'm about to find out if the VT60 sound like the ATS25. @crakers7 as well. 2 pairs of ears.

 

[Isaacc7]

And I'm about to find out if the VT60 sound like the ATS25. @crakers7 as well. 2 pairs of ears.

The vt60 has a really different plate structure, haven’t seen any other tubes like it. I have the Mullard brown base 807, Mazda 807, 5b/254m, some Russian 807, and even the RCA 6bg6ga. All of them have a family resemblance. The VT60 is a different world even though I’m biasing them the same MA-wise. Have you seen this article from The Valve Museum?

http://www.r-type.org/addtext/add029.htm

If you follow the links they are rather dismissive of the construction that I always see in ATS25. Then again they also say that the vt60 doesn’t match up to the American 807. I’m sure that at audio frequencies they’re both really good.

 

[UntilThen]

I’m sure that at audio frequencies they’re both really good.

The only way to find out is with my ears and I don't take much notice of that article because the ATS25 sounds superb. Much better than the Radiotron and Sylvania and the russian 807.

I've also bought these small size 807. Waiting for the adapters to arrive.

 

[UntilThen]

How is this not beautiful. Those glasses are thick, much thicker than most tubes. One of the most robust beam tetrode I've held in my hands.

 

[Isaacc7]

The only way to find out is with my ears and I don't take much notice of that article because the ATS25 sounds superb. Much better than the Radiotron and Sylvania and the russian 807.

I've also bought these small size 807. Waiting for the adapters to arrive.

Huh, I don’t know what the difference is between the 5b/254a and the 5b/254m. I’ve never seen the 254a before and I’m having trouble finding info on it. The 254m is one of my favorite tubes.