[gibosi]

Quote:

I got my 6AU6A tubes, I just need to make a jumper to be able to use them, also need to swap back to the 6AK5 setting.

 
And of course, we are all waiting....

 

[inphu510n]

Seems I hit the age kind of in the middle between you two groups.

I think I'm more in the middle here. I'm in my early 30's.

I've been lazy about trying my new tubes with the amp as I've been more busy lately. I'll get around to creating jumpers some day. I'm really considering just soldering a 26GA wire between the pins to be sure I don't create a poor jumper connection.

 

[Audiofanboy]

I think I'm more in the middle here. I'm in my early 30's.

I've been lazy about trying my new tubes with the amp as I've been more busy lately. I'll get around to creating jumpers some day. I'm really considering just soldering a 26GA wire between the pins to be sure I don't create a poor jumper connection.

Good luck with soldering a wire on tube pins, those crappy oxidized metal pins are a real b**** to solder on... I tried it, failed, cleaned the tube pins thoroughly -had to use sand paper- retried and succeeded -albeit in a soldering shape that would have had trouble fitting into the socket. When I tried it again on real tubes -I tested on dead ones first- I still had trouble getting the solder to hold well.

I found the "pin mod" at the socket level to be not only way easier and flexible, but also just giving a better mechanical connection -the copper strands going down in socket hole end up wrapping around the tube pins along their whole length squeezed between socket hole and pin. So long as the the tubes stands straight, they really can't move and the wire definitely can't go anywhere.

Honestly, if I plug in EF92/91 tubes again, I think I'll just leave the jumpers on the 6ak5 setting and pin mod pins 6+7, as it saves me from flipping the amp around and fiddling inside it, which just can't be that good over the long term...

 

[gibosi]

These showed up in today's mail: GE 6136/6AU6WB, 1960s vintage. There are no date codes on the tubes or the boxes, so the exact year is unknown.
 

 
I had been wanting to try a high quality 6136 and thought these just might fit the bill. The most noticeable difference is the black plates. They are burning in now, but first impressions, these have the classic 6AU6 sound and everything is good.

 

[Audiofanboy]

Quote:

These showed up in today's mail: GE 6136/6AU6WB, 1960s vintage. There are no date codes on the tubes or the boxes, so the exact year is unknown.
 

 
I had been wanting to try a high quality 6136 and thought these just might fit the bill. The most noticeable difference is the black plates. They are burning in now, but first impressions, these have the classic 6AU6 sound and everything is good.

Yeah, definitely curious about how these sound, as they have those "black plates" that I've around on all the premium 6136s from the best years; I only got to try the later -also mil-spec- 6136 etched ones, and was disappointed... I also wonder how these fare compared to the exactly similar looking 5-star GE 6136 -unless they are actually identical- since up to now we've often found differences between military -let alone mil-spec- tubes and others...

 

[gibosi]

A pair of Sylvania 5749/6BA6Ws from the early 1960s arrived yesterday.
 

 
These are remote-cutoff pentodes, as opposed to sharp-cutoff pentodes. Generally, remote-cutoff pentodes are not considered suitable for audio amplifiers. However, I believe this is based on the assumption that they will actually be used as pentodes. When we strap these as triodes, it is hard to predict how they will behave. Since these are really cheap, I thought why not give them a try?
 
I have listened to them for only a short time and been pleasantly surprised at how musical these sound. However, I don't want anyone to think that they should abandon their 8425As for these! LOL But still, a very pleasant surprise. And again, they are really cheap!

 

[ostewart]

My friend just told me the Little Dot MKII+ looks like a coffee machine, haha 

 

[mordy]

Hi All,
 
Today my Tektronix 8425/6AU6 tubes arrived. Pulled out my 6AU6 RCA/BOGEN tubes and put in the new ones. As mentioned by others, I had to re straighten and reposition one of the jumper wires, but now everything makes good contact.
The first impression is the 6AU6 "house sound" of extreme clarity and punch in the bass. In comparison to the RCA tubes, these 4825 GE tubes are sweeter and more extended in the bass and the treble, and less bright in the upper register. I can also turn up the volume control on the LD higher without clipping. (I have it on the 3 o'clock setting.)
 
The heaters are brighter than the RCA's, and I can tell that the tubes are on by looking at them.
 
The sound is absolutely beautiful, even after only 6-7 hours of burn in. Everything sounds better, and I constantly hear new details in the music. At high volume a well recorded tune with kick drum sounds effortless with huge slam, heft and authority in the bass.
 
If you read through the posts about the LD MKIII amp you come across various favorite tubes from various people: Sylvania Gold Pin, Amperex Bugle Boy, Tung Sol etc etc. All these types are available as 6AU6 variants. However, I can't really think of better tubes than these Tektronix tubes.
 
I do notice that Hi-Fi tube tuner and amplifier manufacturers like Fisher and McIntosh used the 6AU6 tube in their products.

 

[Audiofanboy]

Hi All,

Today my Tektronix 8425/6AU6 tubes arrived. Pulled out my 6AU6 RCA/BOGEN tubes and put in the new ones. As mentioned by others, I had to re straighten and reposition one of the jumper wires, but now everything makes good contact.
The first impression is the 6AU6 "house sound" of extreme clarity and punch in the bass. In comparison to the RCA tubes, these 4825 GE tubes are sweeter and more extended in the bass and the treble, and less bright in the upper register. I can also turn up the volume control on the LD higher without clipping. (I have it on the 3 o'clock setting.)

The heaters are brighter than the RCA's, and I can tell that the tubes are on by looking at them.

The sound is absolutely beautiful, even after only 6-7 hours of burn in. Everything sounds better, and I constantly hear new details in the music. At high volume a well recorded tune with kick drum sounds effortless with huge slam, heft and authority in the bass.

If you read through the posts about the LD MKIII amp you come across various favorite tubes from various people: Sylvania Gold Pin, Amperex Bugle Boy, Tung Sol etc etc. All these types are available as 6AU6 variants. However, I can't really think of better tubes than these Tektronix tubes.

I do notice that Hi-Fi tube tuner and amplifier manufacturers like Fisher and McIntosh used the 6AU6 tube in their products.

Those are some very nice tubes Mordy! Out of curiosity, and since we do need to able to grade all those tube types on an absolute scale, would you say then, in your opinion, that the 8425A are superior -best you've heard- to all the other types you've tried up to now, or just equal in listening pleasure to tube X and Y -what you fill in the blanks is what we're interested in of course lol?

It seems everyone on google or fleebay is looking for the famous Telefunken in the 6AU6 family, which are now -obviously- grossly overpriced. The very close -I'm sure as good- second are supposed to be the Mullard Blackburn UK-made variants of the 6AU6/EF94, although most people keep looking for Amperex Bugle Boys and other very-famous-brands which were made by... Oh wait, Mullard Blackburn... So many tubes, while great are looked down upon because of their non-famous branding, though made in the same factory. Many of the better regarded 6AU6 brand or brandings, including a lot of the Fisher, McIntosh, Eico, Amperex (Phillips Holland "Orange Globe" could be better than the Bugle Boys made by Mullard UK) and I suspect some Telefunken, can all be traced back to that same Mullard factory -itself highly regarded for its 12AX7 and 12AT7 and many more famous-signal-tubes if I recall; all the UK tubes I'd had up to now were from Mitcham or Whyteleafe, Blackburn made tubes are supposed to be great.

So, it's funny you'd mention those typically well regarded brands at this point Mordy since my current goal is to get to try a few of these without paying the prime price. Looking at auctions and ads for different 6AU6, I managed to score some very nice looking Valvo -Philips group like Mullard, see where this is going?- EF94 tubes just below the $8 per tube including shipping cut-off, in their West German military boxes (how unusual is that lol?) made in 1966 by... oh wait... Mullard Blackburn (I know from the tube construction and factory codes despite the labels)! So instead of paying $20x2 for used pulls from old Fisher amps, made by Mullard but labeled Fisher or often two different paired amp brands in the same ad, I got four of these, and they look much better than the crappy used Mullard made 6AU6 all over fleebay -being NOS NIB and all.

As per usual, I'll try and report back when I get them, and compare them especially to the 8425A; it's been a while since I've tried a new UK tube, particularly for the "new" old tubes types, so this should be very interesting!

 

[mordy]

The Tektronix are the best overall I tried - I don't think there is any going back to the 6AJ5 Tung Sol that like the best before these - these are so superior to all the others.
 
Curious what you are going to find out about the Mullard 6AU6 variants. In my quest for the perfect 6AK5 tube I tried many of these variants and did find nice ones but still the US tubes came out on top at the end.
 
I found that patience pays off with E-Bay. If you wait long enough you will find exactly what you want at the right price. The trick is to get a a non greedy seller that does it for a hobby and not for a business. Many times I got more bargains by writing to the seller and asking if he has this or that, or asking for a better price if I bought a couple of more pairs. It also pays to buy lots. Keep what you want and resell the ones you can't use.
 
Re 6AU6 tubes: Personally would be interested in Dutch Amperex and mil spec Sylvanias from the late 60's - early 70's. (I found that the cheap mil spec Sylvania tubes sounded exactly the same as the gold pin ones from the same time, but at a fraction of the price.) Did not have much luck with Raytheon tubes except for a 50's 6AK5 tube that had the internal assembly suspended on the bottom pins with the mica rings not touching the glass - excellent sounding. Then the intriguing Tung Sol with the clear top and getter flash on the side of the tube....
 
Back to the Tektronix - I am amazed how loud I can play without being listening fatigued (speakers only). The bass is loud and very powerful, but not booming or bloated - just tuneful and detailed. Could it be that the RCA sound stage is a little wider?
 
However, I am perfectly satisfied with what I have now. I am listening to the music or the equipment?.......
 

 

[Battlescarze]

Its always the equipment, no two instruments sound identical...there is always some variant...even in modern mass production.
 
When you find yourself just listening to the music without thinking about the equipment I would say "you are there"!!

 

[mordy]

"Marvelling at the sound listening to the music!"
 

 

[Audiofanboy]

The Tektronix are the best overall I tried - I don't think there is any going back to the 6AJ5 Tung Sol that like the best before these - these are so superior to all the others.

Curious what you are going to find out about the Mullard 6AU6 variants. In my quest for the perfect 6AK5 tube I tried many of these variants and did find nice ones but still the US tubes came out on top at the end.

I found that patience pays off with E-Bay. If you wait long enough you will find exactly what you want at the right price. The trick is to get a a non greedy seller that does it for a hobby and not for a business. Many times I got more bargains by writing to the seller and asking if he has this or that, or asking for a better price if I bought a couple of more pairs. It also pays to buy lots. Keep what you want and resell the ones you can't use.

Re 6AU6 tubes: Personally would be interested in Dutch Amperex and mil spec Sylvanias from the late 60's - early 70's. (I found that the cheap mil spec Sylvania tubes sounded exactly the same as the gold pin ones from the same time, but at a fraction of the price.) Did not have much luck with Raytheon tubes except for a 50's 6AK5 tube that had the internal assembly suspended on the bottom pins with the mica rings not touching the glass - excellent sounding. Then the intriguing Tung Sol with the clear top and getter flash on the side of the tube....

Back to the Tektronix - I am amazed how loud I can play without being listening fatigued (speakers only). The bass is loud and very powerful, but not booming or bloated - just tuneful and detailed. Could it be that the RCA sound stage is a little wider?

However, I am perfectly satisfied with what I have now. I am listening to the music or the equipment?.......

 

The Tung Sol 6AJ5 was a very nice tube with a guaranteed pleasant listen, but like many 6AK5-ish tubes, I had ultimately found it lacked the absolute details and was a bit soft on the attack. Again, after testing so many other tube types, I just can't see a single reason to go back to the 6AK5 family... This was already somewhat the case for me after spending time with the CV4015, and even moreso a few months later with the GEC CV4014, but some of these new tube types just blow the amp away! I am done with the 6AK5s -otherwise very nice for a trouble free basic headamp- apart from the occasional thrill of testing one or two amusing ones I might get by buying lots, like the earliest Tung Sols with the side getter flash, but that's it for me...

Never did find any redeeming value in the Raytheon tubes I tested, and those with the floating structure -apart from being 6AK5s I said I wouldn't buy anymore lol- are just too rare and/or expensive to be worth it now -and some people reported them to be sibilant, which I just can't live with.

On 6AU6 tubes, you can actually get Amperex "orange globe" ones made by Philips Holland for an "acceptable price", however that would usually fall above the $8 per tube psychological limit. And there many kinds of Amperex, some made by GE, the Bugle Boys made in the UK... The 6AU6 tubes aren't that obscure apparently, and many have been searched for for a decade or more on the web already... I've read nice thing about the Sylvania 6AU6 on like... one google link, which is better than nothing. When you can't find much information about something on google, it means you've gone pretty far in a specific domain or hobby lol...

 

[mordy]

There is always more information on Google; you just have to be creative where to look. To find more out about the 6AU6 tubes, I would explore people who write about guitar amps and people who build DIY radio/amp projects.
 
The next logical step is to write to David ZheZhe and ask him to design the Little Dot MkIIIi AFB edition with built in switches for the 6AU6 tubes. A little toggle switch on the front or the back panel would be a nice touch (no more dealing with pesky jumpers).
 

 

[mab1376]

I personally really like the Raytheon 6GX6, I gave it a few days of use before my GEC CV4014's came in.

To me its like the smoothness of the 6AJ5 combined with the clarity of the M8161, I have been using the CV4014s more due to the high gain which sounds very good with metal and industrial, but for more mellow music like the black keys for instance I prefer the 6GX6.

Unfortunately I haven't had the time or inclination to test the 6AU6A tubes yet.

There is always more information on Google; you just have to be creative where to look. To find more out about the 6AU6 tubes, I would explore people who write about guitar amps and people who build DIY radio/amp projects.

The next logical step is to write to David ZheZhe and ask him to design the Little Dot MkIIIi AFB edition with built in switches for the 6AU6 tubes. A little toggle switch on the front or the back panel would be a nice touch (no more dealing with pesky jumpers).

If anyone figures out a easy elegant solution to not have to use jumpers anymore that would be fantastic!

I hate those things!