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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 286

post #4276 of 10500
Quote:
Originally Posted by Audiofanboy View Post
 

Just found out I actually had a multimeter in my house, so I immediately processed to go and measure my LD!

 

But what I discovered kind of scares me lol...

 

My MK IV SE with a Philips E188CC Holland 1960

 

Heater  -  5.82V


Plate (R) - 75.2V    Grid (R) - 2.06V
Plate (L)  - 75.2V    Grid (L)  - 2.09V

 

And that's with a wall line - European - voltage of 222V, on a regular Saturday afternoon, as in, not a weekday in peek time.

 

I have to admit that the heater voltage worries me a little... 5.8V is way below specs. I could assume that the meter I'm using is crap, but the other measurements seem OK and consistent (those triodes are clearly well matched).

 

I measured the heater with the AC setting and the other voltages with the DC setting as per recommendations. What happens if I measure the heater voltage in DC?

 

I guess I'll try this again late at night, when electricity is "better", you know...

My guess is that you have bad multimeter. Battery could be too old? What i see is that all voltages are suspicious low. Try a new battery inside multimeter and does it give then better results.

post #4277 of 10500
Quote:
Originally Posted by Audiofanboy View Post
 

Just found out I actually had a multimeter in my house, so I immediately processed to go and measure my LD!

 

But what I discovered kind of scares me lol...

 

My MK IV SE with a Philips E188CC Holland 1960

 

Heater  -  5.82V


Plate (R) - 75.2V    Grid (R) - 2.06V
Plate (L)  - 75.2V    Grid (L)  - 2.09V

 

And that's with a wall line - European - voltage of 222V, on a regular Saturday afternoon, as in, not a weekday in peek time.

 

I have to admit that the heater voltage worries me a little... 5.8V is way below specs. I could assume that the meter I'm using is crap, but the other measurements seem OK and consistent (those triodes are clearly well matched).

 

I measured the heater with the AC setting and the other voltages with the DC setting as per recommendations. What happens if I measure the heater voltage in DC?

 

I guess I'll try this again late at night, when electricity is "better", you know...

 

I would simply try another tube and see what you get for the heater voltage. That will give you something to compare with as it may be this one tube has much higher current demands than expected.

The other voltages look pretty good for a 6DJ8 type.

post #4278 of 10500
Quote:
Originally Posted by hypnos1 View Post
 

As I continue to revel in what is entering my eardrums, I KNOW there is a modicum of truth in what I have tried to put across...I repeat : this modest Little Wonder (MKIV SE) is another animal entirely to what I started off with, and have no regrets whatsoever in following every step that has been taken up to the present time. I am sure I am not alone in this, by any means...

 

May the force continue...

 

I couldn't have said it any better... I'm still amazed at how much progress has been made on this amp...

 

Quote:
Originally Posted by Artsi View Post
 

My guess is that you have bad multimeter. Battery could be too old? What i see is that all voltages are suspicious low. Try a new battery inside multimeter and does it give then better results.

 

That occurred to me, but all the other measurements seem OK, so...

 

Quote:
Originally Posted by Ctritical Bill View Post
 

 

I would simply try another tube and see what you get for the heater voltage. That will give you something to compare with as it may be this one tube has much higher current demands than expected.

The other voltages look pretty good for a 6DJ8 type.

 

I'll try another tube pretty soon, for now, I'm just trying to go all the way with this E188CC before doing anything else!

 

Another measurement at midnight, local time, is giving me 218V on the wall, which is now fairly low, as it should really be closer to 230V; and a meager 5.62V on the heater, which, provided the multimeter works, really seems weird... I mean, if the heater voltage were a whole volt lower than specs, it would start to affect the sound somewhat, right?

 

Edit: 5 minutes later, I'm measuring, 226V on the wall and 5.84V on the heater. While that's still not perfect, it's a little more consistent with the first measurement. The plate voltage and grid voltage are still 75.5V and 2.08V.


Edited by Audiofanboy - 12/7/13 at 3:24pm
post #4279 of 10500
Quote:
Originally Posted by Audiofanboy View Post

I couldn't have said it any better... I'm still amazed at how much progress has been made on this amp...


That occurred to me, but all the other measurements seem OK, so...


I'll try another tube pretty soon, for now, I'm just trying to go all the way with this E188CC before doing anything else!

Another measurement at midnight, local time, is giving me 218V on the wall, which is now fairly low, as it should really be closer to 230V; and a meager 5.62V on the heater, which, provided the multimeter works, really seems weird... I mean, if the heater voltage were a whole volt lower than specs, it would start to affect the sound somewhat, right?

Edit: 5 minutes later, I'm measuring, 226V on the wall and 5.84V on the heater. While that's still not perfect, it's a little more consistent with the first measurement. The plate voltage and grid voltage are still 75.5V and 2.08V.
Looks like it is time to purchase a Power Conditioner... "Wallet Don't Fail Me Now" biggrin.gif
post #4280 of 10500

Just got in a few new tubes. Based on Artsi's recommendation I got a Saratov factory Voskhod 6N9S octal tube from the 60's. Just measured it:

 

Voltage: 121V

 

Heater 6.2V

 

Right plate: 151.2V   Left plate:  152.8V

 

Right grid:   1.22 V    Left grid:    1.25V

 

Initial impression: Sounds good and similar to the National Union but a more mellow mid range.

post #4281 of 10500

Hi Nic Rhodes and Hypnos1 and others,

 

Read with interest the comments that the forum has moved into expensive tubes and more advanced modifications, leaving only a small group of people actively participating. IMHO there are many more people out there that follow the thread with great interest but don't post for whatever reason.

 

Being far from knowledgeable in electronics, I have managed to more or less hang on and I have been able to try many of the new tube types that can be used in the LD amps. I find it very intimidating to put together adapters and read about high voltage dangers. But, there is no doubt that having heard tubes from the families of 6DJ8, 12AX7 and 6SL7 Octal tubes there is little that compels me going back to the old favorites.

 

Now, about the comment of pricing ourselves out of the inexpensive tubes I do not agree. True, it gets harder to get bargains, but they are out there. Patience and communication with sellers will pay off. I have this self imposed limit of $8/tube (sometimes broken). I feel that one of the things we could do is to look for good inexpensive alternatives to the 6922, 7308, E88CC, E188CC, 6SLGTY tubes etc etc.

 

Here are some recent buys (all prices include shipping - sometimes you have to buy several tubes to get a better deal):

 

Amperex 6DJ8 1975 A frame Tektronix certified: $5

 

National Union 6SL7GT 1940-50: $8

 

Saratov Voskhod 6N9S 60's: $3.25

 

Voskhod 6N23P 1974: $3.25

 

Thanks to Gibosi I have cobbled together breadboard adapters that don't use soldering (almost). I really enjoy the sound I get out of the LD MKIII and have tremendous listening pleasure even if I did not yet buy the real expensive tubes.

 

The other day a single Telefunken E88C/6DJ8 1968 gold pin went for around $120. The bidding started on 99c and I thought that I had a chance LOL....
 

 

post #4282 of 10500

"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?"

 

 

Very frankly, I am not convinced that things are all that different now. Searching eBay for 6AK5, I see a large number of pairs going for as much as $50, and even as much as $89.  And since one double triode is the equivalent of a pair of LD compatible pentodes, then how can paying $50 to $89 for one double triode be considered all that different? 

 

But of course, not everyone is willing to spend $50 for a pair of 6AK5s and by the same token, not everyone is willing to spend that amount for one double triode. And if one wants/needs to stay on a tight budget, it can be done. There are cheap deals to be had, both in the world of 6AK5s and the world of double triodes. No one has to spend $50 to get great sound.

 

Now I admire Mordy tremendously for his discipline and success in extending his self-imposed limit of $8 a tube to double triodes, but I think a strong case can be made that one double triode should be counted as two tubes, and thus, a limit of $16 for a double triode is not unreasonable. And for $16 a tube, there are many very good double triodes to be had.

 

So to my way of thinking nothing has really changed..... Except for the fact that the sound we are getting out of our LDs now is better than ever. :)


Edited by gibosi - 12/7/13 at 8:31pm
post #4283 of 10500
Quote:
Originally Posted by gibosi View Post
 

"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?"

 

 

Very frankly, I am not convinced that things are all that different now. Searching eBay for 6AK5, I see a large number of pairs going for as much as $50, and even as much as $89.  And since one double triode is the equivalent of a pair of LD compatible pentodes, then how can paying $50 to $89 for one double triode be considered all that different? 

 

But of course, not everyone is willing to spend $50 for a pair of 6AK5s and by the same token, not everyone is willing to spend that amount for one double triode. And if one wants/needs to stay on a tight budget, it can be done. There are cheap deals to be had, both in the world of 6AK5s and the world of double triodes. No one has to spend $50 to get great sound.

 

Now I admire Mordy tremendously for his discipline and success in extending his self-imposed limit of $8 a tube to double triodes, but I think a strong case can be made that one double triode should be counted as two tubes, and thus, a limit of $16 for a double triode is not unreasonable. And for $16 a tube, there are many very good double triodes to be had.

 

So to my way of thinking nothing has really changed..... Except for the fact that the sound we are getting out of our LDs now is better than ever. :)

+1

post #4284 of 10500

Hmm, some interesting points have been raised here.

 

While, I agree that it may look like only a handful of people are actively following up on each and every new trend - read tube type - I also believe that at least a few times more people are just lurking around here are still pretty much trying every new things that's brought up here. This is one of the rare threads I'm active on for example; but for two, maybe three threads I often post on, there's a lot more I always follow and never make myself know in - a.k.a. lurking.

 

Anyway, price-wise, many of these premium, no - or barely any - compromise double triodes, especially the 6922/E88CC & 7308/E188CC, can be found without even looking that hard - basically camping 10 ebay listings for a week - and for very decent prices. Granted, not $8*2=$16, but you can easily get single European Philips E88CC or E188CC for $30-50, or a single Bugle Boy or whatnot - less premium - for $20-30.

 

So, yeah, compared to where the thread started off from - people paying $35 for a pair of "matched" Voskhods from Yen Audio (scandalous in its own right) - I think we've definitely moved in the right direction. At least in terms of sound quality, even though price-wise we haven't ramped up that much all in all - if anything the heptode period was closer to being the exception in terms of price paid per tube!

 

This being said, we've also come to a point where I highly doubt many new and improved whole tube families will pop up out of nowhere, so we can finally dissociate the "game" of tube rolling from the "end" of tube rolling, which is supposed to be getting the best sound out of one's amp. Nothing forbids people from going back to previous tube types and testing new ideas on them just for the heck of it; or finding more oddball tube types for fun, even knowing that it probably won't be to get them the best sound ever.

 

Even I have a few ideas I never managed, or had time to, put together before "we, the people"; wait no... That's not right... "We, the handful" leaped in the double triode abyss. Here's a few ideas I had a few months ago, cheap and interesting ideas :

 

- Using a good ol' pentode - the examples I'd read about used a 6AU6 type - with the screen grid (g2) as the anode, and the actual anode grounded. I know this should work in theory, since it's used in some applications. People over on the LaFigaro 339 thread have used and loved this exact technique in their amp in the driver position, where a I-forget-which-pentode-type is triode strapped in this way. I never got a chance to try this on a LD before, since it used to be difficult to "invert" pins at the socket level, and since there was no place I knew of to easily tie a pin to the ground. Now, with the Vectors, virtually anything is possible, and we've confirmed that the front right screw is an easy path to the ground, so one could just link a wire between the anode pins to this screw and ground the anodes. Then, the screen grids could be rewired with the Vectors to their respective anode pins at the socket level. Just an idea... Should work so long as there's no more than 0.5W of dissipation on the screen grid; and even if there is, it'd still be interesting to try.

 

- The 6GK5 tube: VHF single triode, frame grid construction - like all the cool kids, and the 6DJ8, you know. This is the point where I'd stopped at just before using double triodes, so I never got a chance to try this tube type. It would need some degree of pins rewiring, but nothing out of this world if one tries hard enough. It's cheap, has pretty good characteristics, a frame grid, and is very linear. I have no idea how it is supposed to be biased since I don't recall we'd been talking about such things back a few months ago... Anyway, just an - cheap - idea.

 

And on a totally separate note, two other recent ideas, or more like questions actually, that occurred to me yesterday when taking measurements of my amp.

 

An easy one first, now that we know for sure that that front right screw leads to ground, couldn't we tie the pin 9 shield of 6DJ8 tubes to this screw instead of tying it to the right triode cathode?

 

A more difficult question now : how hard would it be to make and use a battery-powered supply for the driver heaters (a 6.3V 0.5-1A DC power supply) and could it bring somekind of an improvement to the way the driver tubes function (less hum or noise, better and more stable current supply...)? I can't imagine it would be hard to make, I'm more curious about what it would change. I'm pretty sure I've read examples of people preferring a DC battery power supply to an AC transformer power supply for heating their tubes...

 

Anyway, I'm sure there are many things we can still work on to improve the sound of our LD amps, without spending $100 a week on new tubes... And that's my point: no one needs to spend that much on tubes if they're tube rolling for fun in the first place!

post #4285 of 10500
Quote:
Originally Posted by TrollDragon View Post


Looks like it is time to purchase a Power Conditioner... "Wallet Don't Fail Me Now" biggrin.gif

 

Fortunately, Xmas is coming :veryevil: !

post #4286 of 10500

A bit off topic...

 

I do not own a CD player and on the rare occasions that I want to play a CD, I just use the computer's built-in unit, which is not so good I am told. So I have been thinking about getting a simple CD player with optical out, but most of what I am seeing are jukebox and/or SACD players and are rather expensive. It occurs to me that I can pick up a Blu-ray player with optical out for not much money, and I also notice that these players typically support SACD, in addition to CD.

 

Comments? Suggestions?

 

Thanks! :)

post #4287 of 10500

Hi Gibosi,

 

Oppo is a brand that has a very good reputation. This model appears to have an optical output but not Blue Ray:

 

http://www.ebay.com/itm/Oppo-DV-981HD-DVD-Player-SACD-DVD-Audio-CD-PAL-DivX-1080p-upconversion-HDMI-/271339296646?pt=DVD_Players_Recorders&hash=item3f2d151786

 

Expect to pay around $80 + shipping. You can go to the right column next to the listing and click on completed listings to see what people paid recently for this item.

 

Some people in the Hi Fi world claim that the Sony Playstation 1 (earliest model) has excellent sound for CDs - could be found for $25 or less but no extra features.

post #4288 of 10500

More measurements:

 

I bought a 1960s octal 6H9S, but I now see that the date is 0481. However, the seller included a second octal tube for free. It looks very much the same as the first one except for OTK1 printed on the base, otherwise there are no markings at all. Maybe this tube looks older, or it was just the dust on the base. When listening to this 6H9S tube it sounded better than the first one.

The measurements are slightly different compared to the first one:

 

122 V

 

Heater 6.2V

 

Plate R: 152.9V    Plate L:  154.6V

 

Grid R: 1.18V       Grid L: 1.22V

 

The next tube is an August 1974 Voskhod 6N23P tube (6DJ8 family):

 

121.6V

 

Heater 6.2V

 

Plate R 102.8V        Plate L: 97.0V

 

Grid R:  2.67V         Grid L:   2.76V   (Note: The plate and grid voltages fluctuate a little; the same as the AC house voltage.)

 

First impression of the Voskhod 6N23P is that it is punchy and forward with good detail. Even though I bought is as used it could be that it needs more time to be comfortable in it's new home. Remember the 120 hr burn in of the old Voskhods?

 

Wish I understood what the measurements indicate, and how to translate them into how something sounds. Based on my Hi Fi experience over a few years, measurements do not necessarily correspond to how something sounds.

post #4289 of 10500

Ok here is something very strange... Is there a special setup for measurements?

 

The JAN Sylvania 5751 from '79

 

Line Voltage - 120VAC

Filament  - 6.2 VAC

 

Plate 1 - 145 VDC

Grid 1 - 0 VDC

Cathode 1 - 1 VDC

 

Plate 2 - 144 VDC

Grid 2 - 0 VDC

Cathode 2 - 0.99 VDC

 

All these are measured from ground except the filament?

There is no measurable Grid voltage at all for some reason.

post #4290 of 10500
Quote:
Originally Posted by TrollDragon View Post
 

Ok here is something very strange... Is there a special setup for measurements?

 

All these are measured from ground except the filament?

There is no measurable Grid voltage at all for some reason.

 

According to Ctritical Bill, when the tube is idle, the grid is 0 volts, but measuring the cathode voltage when the tube is idle amounts to the same thing.

 

http://www.head-fi.org/t/563884/little-dot-tube-amps-vacuum-tube-rolling-guide/4200#post_10034489

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