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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 284

post #4246 of 10575
Quote:
Originally Posted by mordy View Post
 

Would like to measure the voltages using the Vectors. My wall outlet voltage is 122V. Does this mean that the values will be skewed upwards?

 

If I were to measure the voltages of a dual triode octal tube, am I to measure only on one Vector adapter? Which pins to measure on the 12AX7 adapter that I use with an additional adapter for octal tubes?

 

Since your wall voltage is 122, like mine, your heater voltage might be high, around 6.7, like mine. On the other hand, you have a LD III, whereas, I have an LD 1+, so different transformers....

 

Again, I prefer to take all measurements on the Vectors. In this way, it doesn't matter whether you are running a 6DJ8, 12AX7 or 6SL7.

 

To measure heater voltage, set meter to AC and measure across pins 3 and 4 on the Vector that is supplying the 9-pin adapter.

 

To measure Plate voltage, set meter to DC and measure across pin 5 and ground on each Vector. So you would have two readings, for the right triode and for the left.

 

To measure Grid voltage, set meter to DC and measure across pin 2 and ground on each Vector. Again, two readings, one for each triode.

 

Substitute your tube, amp and readings, and post like so:

 

A 1960 Heerlen, Holland E188CC running in an LD 1+:
 
Heater  -  6.7v


Plate (R) - 81.5    Grid (R) - 3.1
Plate (L)  - 81.5    Grid (L)  - 3.1

post #4247 of 10575

A small package arrived today with a 1961 Philips Miniwatt 6922/E88CC (7L6 Delta1K3). I am curious to see how it compares with a 1960 7308/E188CC from the same factory....

 

post #4248 of 10575
Quote:
Originally Posted by gibosi View Post
 

A small package arrived today with a 1961 Philips Miniwatt 6922/E88CC (7L6 Delta1K3). I am curious to see how it compares with a 1960 7308/E188CC from the same factory....

 

By all means, don't hesitate to write a long review of this tube, especially compared to the E188CC - which also deserves a full review of its own! I only have 15 hours on my E188CC, but I expect I'll be able to give pretty decent impressions by the end of the weekend.

 

It's interesting how in 1961, the Heerlen factory was already on its 7th batch (change code) of E88CC, but only on its 3rd batch of E188CC. The fact that it took Philips those first batches or revisions of the premium E88CC, and four whole years, to come up with the even more premium and low noise E188CC does make me think that there just has to be a difference between how the two types sound, at least for the early batches.

 

I mean, I just can't imagine that it would have taken the company this long to just make an new-yet-inferior tube grade, especially considering the demand for low noise double triodes for communication/long distance transmission and other critical applications in those days. A good - as in from a good manufacturer - E188CC should be "better" than an equivalent E88CC made in the same time frame in the same factory. Maybe less musical, fun or whatnot, but logically less noisy, letting details stand out better in a blacker background; in theory of course.

 

Even after a few hours, I could tell my early E188CC tube had a level of detail in the treble and mids that just screamed realism, probably moreso than my early Amperex US 6922, and I'm pretty that's because of the black noiseless background (bass still needs a bit of burn-in to assess its quality).

 

There must have been a true need for a low noise version of those tubes, since before - and even after - the E188CC was made, many companies were asking for special quality E88CC types for their own use and made to their own specs, like the CCa type in Germany. Interestingly, companies like the German Post kept buying and using the CCa type, forever based on the noisier E88CC, when most other European companies that used special quality E88CC tubes switched to E188CC when they could - or so I've read.

 

My pair of Philips E188CC actually has some faded "E.D.F." ink stamps on the box, which was - and is still is - the French Electric company, meaning that they were already using the E188CC in some applications less than a year after the first batch.

post #4249 of 10575
Quote:
Originally Posted by gibosi View Post
 

 

I have three of these gold pin/grid Tesla E88CC, but I forgot to mark the one that has already been burned in for 20 hours!!  (>_<)  I guess I am going to have to start all over again! lol :)

 

And thank you so much for posting this! My wallet is feeling much better now that I am no longer feeling the urge to get a TFK ECC88!  :) 

 

Oh dear, G, where do you find the time to carry out all these different tube-testings? You definitely have a different clock to mine, that's all I can say!..Good luck, anyway...

 

Just one thing I must point out about these Tesla E88CCs - they are definitely NOT 'warm' tubes! So an already bright system would probably not be a good candidate for these otherwise marvellous babies...

 

Slightly off-topic, but after posting a comment on a review of the HD650 methinks I opened up a can of worms - viz a comment from someone stating 'not to waste time and money on the Little Dot', but go for a Bottlehead Crack instead. Obviously I had to investigate and found what might be an interesting project for the winter months (although I can't help feeling somewhat of a traitor!) - ie a self-build amp that looks amazingly good for the money, and would be fascinating to compare with the beloved MKIV SE now it has reached such heights. However, being a Stateside concern would mean high shipping and dreaded VAT robbery...so it's probably a non-starter. Has anyone here come across this supposed beauty? (Not in the looks department though, as far as I'm concerned - power, signal inputs and headphone socket on the TOP of the unit? Crazy, man! Mind you, it wouldn't take too much modifying to remedy that nonsense I'm sure...Plus I could use the pure silver wire that I have found does wonders wherever it goes...this time MY wallet is shaking with dread - perhaps VAT will be my saviour!!...


Edited by hypnos1 - 12/6/13 at 8:22am
post #4250 of 10575
Quote:
Originally Posted by hypnos1 View Post
 

 

Oh dear, G, where do you find the time to carry out all these different tube-testings? You definitely have a different clock to mine, that's all I can say!..Good luck, anyway...

 

Just one thing I must point out about these Tesla E88CCs - they are definitely NOT 'warm' tubes! So an already bright system would probably not be a good candidate for these otherwise marvellous babies...

 

Slightly off-topic, but after posting a comment on a review of the HD650 methinks I opened up a can of worms - viz a comment from someone stating 'not to waste time and money on the Little Dot', but go for a Bottlehead Crack instead. Obviously I had to investigate and found what might be an interesting project for the winter months (although I can't help feeling somewhat of a traitor!) - ie a self-build amp that looks amazingly good for the money, and would be fascinating to compare with the beloved MKIV SE now it has reached such heights. However, being a Stateside concern would mean high shipping and dreaded VAT robbery...so it's probably a non-starter. Has anyone here come across this supposed beauty? (Not in the looks department though, as far as I'm concerned - power, signal inputs and headphone socket on the TOP of the unit? Crazy, man! Mind you, it wouldn't take too much modifying to remedy that nonsense I'm sure...

 

I was very curious about the Crack back when I had a HD650, but looking at the performance I'm getting now with the 6N30P-DR + premium 6DJ8 tubes on my MK IV SE, I have to wonder if a well tubed Crack would be better or just different.

 

Bear in mind it's quite different from the LDs; I believe the first stage is a cathode follower for instance feeding a different breed of power tube(s), and the whole amp really only works well with high impedance headphones. So no mucking around with a second pair of lower impedance headphones without keeping a different amp.

 

Basically, the Crack is fun to build, fairly powerful with high-Z cans, excellent sounding with good tubes, even moreso with the Speedball CCS upgrade, but not particularly versatile, and not particularly cheap once you factor everything in (parts, CCS upgrade, good tubes, factory build fee for the less DIY inclined). I keep seeing very good deals for Crack units in the classifieds here though.

 

The LD MK III & IV are fairly powerful with high-Z cans (less so than the Crack), excellent sounding with good tubes (though using the best driver tubes is still a bit of a mess lol), pretty versatile all in all (more than you would think at first glance, as it actually works pretty well with low-Z cans), and "dirt cheap" to "not to bad of a deal" depending on which amp you buy, tubes used, etc...

 

I would have no more use for the Crack with my orthos, so I'll probably never compare it to my MK IV, but was always curious about that in my Senn days. I do recall reading that the LDs really did hold their ground compared to the Crack though. I guess it's just a matter of tubes after that...

post #4251 of 10575
Quote:
Originally Posted by hypnos1 View Post
 

Slightly off-topic, but after posting a comment on a review of the HD650 methinks I opened up a can of worms - viz a comment from someone stating 'not to waste time and money on the Little Dot', but go for a Bottlehead Crack instead. Obviously I had to investigate and found what might be an interesting project for the winter months (although I can't help feeling somewhat of a traitor!) - ie a self-build amp that looks amazingly good for the money, and would be fascinating to compare with the beloved MKIV SE now it has reached such heights. However, being a Stateside concern would mean high shipping and dreaded VAT robbery...so it's probably a non-starter. Has anyone here come across this supposed beauty? (Not in the looks department though, as far as I'm concerned - power, signal inputs and headphone socket on the TOP of the unit? Crazy, man! Mind you, it wouldn't take too much modifying to remedy that nonsense I'm sure...Plus I could use the pure silver wire that I have found does wonders wherever it goes...this time MY wallet is shaking with dread - perhaps VAT will be my saviour!!...

 

I bumped into a Bottlehead Crack at a recent meetup and noticed that it was running a 12AU7. I offered to loan the owner my three 5751s to try out, but he told me that the 12AX7, and even the 5751, had way too much gain, and wouldn't work. So... if you were to purchase and build one of these amps, tube rolling options would seem to be very limited. Given that, I will take my LD with 6DJ8, 12AX7, 6SL7 and 2C51 every time. :)

post #4252 of 10575

Hi Gibosi,

 

Here are the measurements of a National Union double triode 6SL7GT from the 40-50's running in a LD MKIII through a 12AX7 adapter: (Measured with an inexpensive Sears digital multi tester)

 

Voltage 122.8

 

Heater 6.3 V

 

Plate R 148 V

Plate L  152 V

 

Grid R 1.34 V

Grid L  1.26 V

 

Would like to hear comments what these measurements mean, especially if they have an effect on the longevity of the tube and the amp, if at all.

 

The tube sounds very nice, and I have run it several days straight in the amp. The amp does not get hot or even warm at all; the tube feels slightly warm to the touch, but you can touch it without any discomfort.

post #4253 of 10575
Quote:
Originally Posted by mordy View Post

 

Here are the measurements of a National Union double triode 6SL7GT from the 40-50's running in a LD MKIII through a 12AX7 adapter: (Measured with an inexpensive Sears digital multi tester)

 

Voltage 122.8

 

Heater 6.3 V

 

Plate R 148 V

Plate L  152 V

 

Grid R 1.34 V

Grid L  1.26 V

 

Would like to hear comments what these measurements mean, especially if they have an effect on the longevity of the tube and the amp, if at all.

 

I will have to leave it to others to comment on what these measurements actually "mean". But what I find interesting is that with the same mains voltage, 122.8, the LD III provides 6.3 volts to the heaters, while my LD 1+ provides 6.7 volts!

post #4254 of 10575
Quote:
Originally Posted by hypnos1 View Post
 

 

Oh dear, G, where do you find the time to carry out all these different tube-testings? You definitely have a different clock to mine, that's all I can say!..Good luck, anyway...

 

Just one thing I must point out about these Tesla E88CCs - they are definitely NOT 'warm' tubes! So an already bright system would probably not be a good candidate for these otherwise marvellous babies...

 

Slightly off-topic, but after posting a comment on a review of the HD650 methinks I opened up a can of worms - viz a comment from someone stating 'not to waste time and money on the Little Dot', but go for a Bottlehead Crack instead. Obviously I had to investigate and found what might be an interesting project for the winter months (although I can't help feeling somewhat of a traitor!) - ie a self-build amp that looks amazingly good for the money, and would be fascinating to compare with the beloved MKIV SE now it has reached such heights. However, being a Stateside concern would mean high shipping and dreaded VAT robbery...so it's probably a non-starter. Has anyone here come across this supposed beauty? (Not in the looks department though, as far as I'm concerned - power, signal inputs and headphone socket on the TOP of the unit? Crazy, man! Mind you, it wouldn't take too much modifying to remedy that nonsense I'm sure...Plus I could use the pure silver wire that I have found does wonders wherever it goes...this time MY wallet is shaking with dread - perhaps VAT will be my saviour!!...

http://www.canuckaudiomart.com/details/649095164-bottlehead_crack_otl_amp_kit_w_speedball_upon_arrival_accepts_btc/

post #4255 of 10575

Nice!

The guy even accepts BitCoin's... I wish I had been mining those a long time ago.

post #4256 of 10575
Quote:
Originally Posted by hypnos1 View Post
 

 

Oh dear, G, where do you find the time to carry out all these different tube-testings? You definitely have a different clock to mine, that's all I can say!..Good luck, anyway...

 

Oh, I wish I had a clock which could allow me to run in double time! lol  And to make things worse, it seems that these recent tubes are so good that when I sit down with the intention to do some critical listening, I often get so enthralled with what I am hearing that I stop listening to the "tube" and just "surrender" to the music. So while I do hope to be able to eventually test and review all these wonderful tubes, my progress is appallingly slow...

 

So while revisiting the Tesla E88CC is definitely on my To-Do list, I have no idea when I will actually get to it... 

 

And soon I will have a Western Electric 396A to add to the mix!!

 

Too many wonderful tubes!! What a nice problem to have! lol :)

post #4257 of 10575

That is in fact a terrible dilemma to have gibosi!

 

You know that if you are ever overwhelmed by all the tubes you need to check, feel free to fire some of them this way and I can listen to them for you. :D 

post #4258 of 10575

To those that understand the significance of relative plate and grid voltage values: 

 

I have three 1975 Voskhods, so I thought it might be interesting to measure them, and perhaps, these measurements could help me choose the one that has the best-matched triodes.

 

Voskhod #1

 

Plate (R)   85.3    Grid (R)   2.7
Plate (L)   85.6    Grid (L)   2.9

 

Voskhod #2

 

Plate (R)   88.9    Grid (R)   2.6
Plate (L)   88.9    Grid (L)   2.4

 

Voskhod #3

 

Plate (R)   85.2    Grid (R)   2.9
Plate (L)   85.2    Grid (L)   2.2

 

Number 2 seems to be the "best", but perhaps the differences in the others are too small to be significant?

post #4259 of 10575

The Crack is never designed to be a tube rollers amp, The LD 3 and 4s are. The choice of sticking with a 12AU7 for the Crack is the right call. It is  what is designed to work with and VERY well with speedball (rolling is just poor here, just look at Doc posts). The LD is a fun amp that we can have fun to roll all sorts of cheap tubes in. This recent move to the ' more normal tubes' of other amps use routinely is rather missing the essence of the LD inho. I have shed loads of 5751s, '88s' etc but I also have other amps that use these tubes very much better. The '88' ain't a bad roll with difficulty but just because you can roll a tube doesn't make it a good operating point for the tube in the LD and there are far too many other tubes being talked about now that are just way off the mark (12AX7s?!)....For me the essence of the LD was the tube rolling for all, we are now moving into area where it is an area of just 6 (of us). Have we lost what was fun for these LD?

post #4260 of 10575
+1 to that and well put.

Chasing down $5 Heptodes was a lot of fun. Seeking out a single tube less than $50 has taken a little of the sparkle out of it all.

But do "Roll On" by all means!
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