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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 458

post #6856 of 7547

Hi All,

 

What is this?

 

 

This is my long awaited dream - to have a Little Dot MK9. Well, not exactly, but this is is a Little Dot MkIII v.MK9 or M9 (pronounced Maiin) for short. {I know, two ii's is in style.}

 

What we have here is a modded MKIII with the tube complement of a Little Dot  MK9 - two RCA 6080 tubes and a Russian 6H9C - also known as 6N9S/6N9P and equivalent of 6SL7.

 

Finally got my 15A voltage regulator and hooked it up to my 430W 15A PC PS. The whining noise I heard before at very high volume levels thankfully disappeared. The 6080 tubes run very hot, and if you are not careful you could sustain a burn on your fingers if you touch them. Have my 4" fan running (top right in picture) and the transformer housing reads about 85F or so; not too hot.

 

At first I tried a pair of Sylvania 6080 tubes as power tubes (and another Sylvania 6SL7 as driver)  but found them to be too sibilant. With the present set up with the two 1960 RCAs and a 1981 Russian driver I was pleasantly surprised at the sound - really nice and sweet and very musical. I guess that the LD amp designer Sword Yung did the tube rolling for me this time...(The LD MK9 uses a Chinese 6N9P tube)

 

As mentioned, the 6080s need external power, but the 6H9C only draws 0.3A so it is plug and play with an adapter.

 

As I am listening I am getting more excited about the sound - it really sounds very good!

 

Just added up the cost of all the pieces needed to make this work, including the tubes: 7 adapters, breadboard, voltage regulator, PS, 3 tubes. It comes out to around $130.  A new MK9 is $518.

 

http://www.ebay.com/itm/Little-Dot-MK-9-Vacuum-Tube-Amplifier-/201073365088?pt=Vintage_Electronics_R2&hash=item2ed0e81060

 

 

One piece is missing: The protective circuit to be able to use the M9 with a Direct Coupled (DC) amplifier. (Maybe TD can weigh in on that topic.)

 

Happy tinkering and tube rolling!

post #6857 of 7547
Quote:
Originally Posted by 8bitBarry View Post
 

Thats excellent. I have a few pairs of ECC83's I could use now, so I will have to get some converters. 

 

I had a really good tread through your posts and others, to have a look at the C3G's info but I can't find any sound description for these valves. Can you give me any idea of what to expect before buying? Sorry if I have missed something but there's quite a few pages now... (* I started around page 400 where the search feature lead me)

 

Many thanks in advance. I am learning an awful lot from this thread.

 

Hi 8bit.

 

So you're seriously interested in the C3g?...Such a shame you don't have the MKIII or IV (perhaps for Christmas?!), as you could then experience that driver's absolute magic when combined with the 6AS7G power tubes - and spend even more money, lol!

However, I think I can safely say that there is no better driver for our LDs than the C3g (especially if you can grab a bargain lot that (rarely!) comes along), apart from perhaps the sub-miniatures that gibosi and mordy have been enjoying. Although they are much cheaper than the C3gs, as you will have seen, they require quite a bit of "playing around" with. If you can stretch the pennies, the C3g route is much easier, with the C3g to 6AK5 adapter available on ebay.

Good luck, whatever you decide to do, and feel free to ask for any assistance, if needed.

 

Cheers,

CJ

 

Quote:
Originally Posted by MIKELAP View Post
 

Ive had the Woo Audio2 for a while now and when i compare my mk3 with either 6DJ8 OR 6SL7 tubes that i generally use with the amp the Littledot is still very very listenable and i dont use the tubes you guys are using now .compare to the Woo with more bass and warmer sounding the Littledot is a bit thin sounding but like i said very listenable.                                                                                                                                                                                                                      

 

 

Ah, mikelap...there you have it. If you had the C3g(S) in the driver seat, feeding the Chathams in your MKIII, I am certain you would find the LD much closer to your Woo, lol! :wink_face:. (Especially if you upgraded those caps!!).

post #6858 of 7547
Hey mordy!

I gave up on the protective circuit, I sent the builder my address a couple of months back and I am not going to hound him anymore... It's been almost a year and it looks like he is just plainly not interested or just way too busy for a one off item...

beerchug.gif
post #6859 of 7547

Hi I've got a pair of Thomson 6080s installed now, with a 6SN7.  They sound good and hopefully will improve with breaking in.

 

I was pretty shocked how much current the 6080s pull when I was near stock, ie over 150mA total for amp compared to 50mA or so with 6n6ps.  The increased current draw also meant the 6SN7 got moved out of the operating point I was at as well, from 5.5mA/115v to 3.5mA/95v, cos of the B+ changing from 220v to around 160v.  I ended up reducing the power resistors (the 2 180s) to a 60 and a 110, to try and get the B+ a bit higher, ending up at 193v (+ the 6SN7 being at a better operating point again). 

 

I also got an 8A power regulator, which I'm using with a laptop supply, but it seems like I have to redo the voltage setting every time I start it.  Just wondered if anyone else has found that or whether mine might be faulty?  Thanks.

post #6860 of 7547

Hi,

 

More tube rolling - using two select 1960 RCA 6080s as power tubes with an octal driver. First I tried a Russian 6N9C  (6SL7 ) with good results. Then I tried a 12SL7 GE tube from 1954 that had done duty as a power tube.  It was OK but lacking the wow factor.

 

Then I went back to the MK9 recipe and tried a Sylvania 6SL7WGT from August 1966 with beige base. Wow! Beautiful, expansive sound, very musical. Had to compare it with the miniature wunderkind, the Raytheon 6832. Very nice sound, detailed, more bass than the Sylvania 6SL7WGT but more analytical - perfect for AFB (where are you? Lost in Japan?)

 

So there we are: The old quandry - musical or analytical? Both these tubes sound excellent in this environment - we have to see how it shakes out; which one will I prefer? At this stage I don't know; both these tubes are great with the 6080s.

 

Originally I thought that the RCA 6AS7 tubes would sound better, but for me the 6080s have a fuller sound. Maybe the bargain samples I have from 1965 and 1974 aren't the best ($4 and $5 incl shipping; paid $11 for 7 6080 tubes incl shipping which goes to show that Coke sells). Both Coke bottles have identical construction except that one has black plates and one gray plates.

 

Hi lemonjelly,

 

I found that the the voltage fluctuates all the time, but the changes are very minor. I might set the voltage at 6.3V and later it would read 6.27V or 6.31V. I had a situation where the voltage fluctuated much more and determined that the PS was defective and discarded it. Perhaps this is your situation.

 

It is important IMHO to measure the voltage at the tube pins or tube socket with the tube in place since it may drop more than 1/2V depending on the tube - the more power the tube draws, the bigger the difference.

post #6861 of 7547

Hmmm mine is a bit different... I wouldn't mind if the voltage was just changing a bit, but it jumps around at less than a volt when first turned on (+LED blinks on the regulator) until I rebias it .  I'm wondering if it might be cos the tubes probably pull more power initially so maybe it's overloading the regulator/PSU (it has 2 6080s in parallel on it).  I do have another PSU that I could try at some point.  Kinda done for a while with messing around so I'll just suffer the hassle rather than change stuff again.  It def stays stable once it's changed to 6.3v so not sure really.  Maybe I'll try a 5.7v or so bias and see if it keeps working after turning off/on (if it's pulling too much at 6.3v at startup maybe it would be OK at a lower voltage).

 

Anyway I'll definitely reread some bits of this thread and pick a few tubes to roll, fantastic info here !

post #6862 of 7547

From what I seen on the blog a tube may draw perhaps twice the current (or more) at start up so it may very well be what you think. If the voltage is stable once warmed up I wouldn't worry. However, when I switched to a more powerful PS the sound improved with a better bottom end.

 

I usually listen through speakers, and at start up there usually is some loud noise or static. In order to spare my ears and speakers, I shut off the speakers until I see the spikes on a LED meter on my receiver that indicates the wattage used. After 30 seconds or I can safely turn on the speakers. What I am seeing on the LEDs is probably the warm up surge.

post #6863 of 7547

Mordy,

 

Since you have those big honking heater power supplies for your output tubes, I really think you should upgrade to some tubes that can better use all the power, perhaps a pair of 6336A or 6528. These draw 5A each. :)

 

http://www.radiomuseum.org/tubes/tube_6336a.html

 

http://www.radiomuseum.org/tubes/tube_6528.html

post #6864 of 7547

Hi G,

 

My PS definitively is not honking, but nice and quiet LOL I do have my sights set on the 5A tubes, but so far only found them at the lowest prices of $25 - 35 each. First plan is to snag some 5998 Chatham tubes, but right now slim pickings. Actually was going to buy from the the guy Nic told us about, but he sold the last five before I could work it out with him.

 

What do you say about the 7236 tube? Both the 5998 and 7236 draw 2.4A.

 

Meanwhile I am trying to find out the best driver tube combination for my two Carlson-Stromberg 6080s.

post #6865 of 7547
Quote:
Originally Posted by mordy View Post
 

My PS definitively is not honking, but nice and quiet LOL I do have my sights set on the 5A tubes, but so far only found them at the lowest prices of $25 - 35 each. First plan is to snag some 5998 Chatham tubes, but right now slim pickings. Actually was going to buy from the the guy Nic told us about, but he sold the last five before I could work it out with him.

 

What do you say about the 7236 tube? Both the 5998 and 7236 draw 2.4A.

 

Meanwhile I am trying to find out the best driver tube combination for my two Carlson-Stromberg 6080s.

 

Unfortunately, 6336's and 6528's are likely the least expensive of the bunch, at $25 - 35 each. Both the Sylvania and Tung-Sol/Chatham 7236's have gotten good reviews, but the cheapest I have seen them is about $35. And the cheapest I have seen 5998 is about $80. So if you can get any of these for your standard price, you will be doing very good indeed! :)

post #6866 of 7547

Further proof of early onset dementia, I fear!....

 

Having bought a spare Chatham 6AS7G a while back (not the same one as my recent hiccough!), and as it looked almost new and (supposedly) tested for this and that, I didn't bother to try it in the amp straight away. Yesterday I finally decided to give it a go and yes, you've got it....:eek:...horrid distortion! So I clean the pins - although they looked like new...no change. Then it's into the other socket (blaming my homemade adapter first off)...just the same... :(...then :angry_face:. Totally unlistenable! And even more anger - at myself - for not checking it straight away (hence dementia, lol!). I ALWAYS used to...Have emailed the vendor, but I don't hold out too much hope, being the increasingly cynical old b***er that I am! Still, we live in hope...

 

So, folks, the moral of the tale is : ALWAYS CHECK YOUR TUBES THE MINUTE YOU GET 'EM! But then, y'all always do, don't you?

Am also now even more peeved that that $15 Chatham seller didn't post to the UK!!

 

One positive note did come out of the whole saga, however : while checking that the rogue tube didn't wreck my beloved LD (and have me guiltily pondering the la Figaro 339 - how could I?!), I popped  the 6N30P-DR in the right channel on a whim. And...interesting...At first the sound seemed a bit fuller, with a shade more bass...hmmm...But within less than a minute, I had to stop - couldn't stand it any longer. Even with the TS Chatham in the left channel, the wonderful detailed, airy, holographic sound that I have come to love was totally absent. I know it's rather silly to be judging two dissimilar tubes in bed together, but it did reinforce (if it were needed!) the magical qualities brought to the table by the Chatham 6AS7Gs. The sound is just in another league altogether - especially when partnered with the C3gS......still miffed about the duff tube, though!

post #6867 of 7547

To those of you whom are owners of it-- how do you guys fancy your Little Dot 1+s?

post #6868 of 7547
Quote:
Originally Posted by hypnos1 View Post

Hi 8bit.

So you're seriously interested in the C3g?...Such a shame you don't have the MKIII or IV (perhaps for Christmas?!), as you could then experience that driver's absolute magic when combined with the 6AS7G power tubes - and spend even more money, lol!
However, I think I can safely say that there is no better driver for our LDs than the C3g (especially if you can grab a bargain lot that (rarely!) comes along), apart from perhaps the sub-miniatures that gibosi and mordy have been enjoying. Although they are much cheaper than the C3gs, as you will have seen, they require quite a bit of "playing around" with. If you can stretch the pennies, the C3g route is much easier, with the C3g to 6AK5 adapter available on ebay.
Good luck, whatever you decide to do, and feel free to ask for any assistance, if needed.

Cheers,
CJ

Quote:
Originally Posted by hypnos1 View Post

Hi 8bit.

So you're seriously interested in the C3g?...Such a shame you don't have the MKIII or IV (perhaps for Christmas?!), as you could then experience that driver's absolute magic when combined with the 6AS7G power tubes - and spend even more money, lol!
However, I think I can safely say that there is no better driver for our LDs than the C3g (especially if you can grab a bargain lot that (rarely!) comes along), apart from perhaps the sub-miniatures that gibosi and mordy have been enjoying. Although they are much cheaper than the C3gs, as you will have seen, they require quite a bit of "playing around" with. If you can stretch the pennies, the C3g route is much easier, with the C3g to 6AK5 adapter available on ebay.
Good luck, whatever you decide to do, and feel free to ask for any assistance, if needed.

Cheers,
CJ


Ah, mikelap...there you have it. If you had the C3g(S) in the driver seat, feeding the Chathams in your MKIII, I am certain you would find the LD much closer to your Woo, lol! wink_face.gif . (Especially if you upgraded those caps!!).

Many thanks for the advice and ideas. I'm very captivated my LD 1+ so I would happily invest in another LD system like the mk4. I'm a valve head, I see mileage in this smily_headphones1.gif
I crossed into this from vintage guitar amps, so it's great to explore the similar experiences in hifi. The LD systems give fabulous value and give me immense enjoyment so I can see myself investing.

The 6AS7G you mention - are there any brands you recommend over others?

Do you see any benefit of the C3GS over the C3G? I read earlier it wasn't very beneficial, but thought I would ask again.

Thanks CJ
post #6869 of 7547

I love my F@#^ed up LD 1+:biggrin: See........

 

 

 

 

 

 

This last picture i called it BIGFATUGLYDOT 1++:atsmile: I forgot more +++++.


Edited by i luvmusic 2 - 7/15/14 at 5:26pm
post #6870 of 7547
Quote:
Originally Posted by Frankzappa92 View Post
 

To those of you whom are owners of it-- how do you guys fancy your Little Dot 1+s?

 

If you want to be able to use low-impedance headphones and IEM's, the 1+ is the best choice. It can use precisely the same driver tubes as the II, III and IV, plus 408A's. Further, in the same way that owners of the other LD's can roll power tubes, owners of the 1+ can roll op amps. On the other hand, if you have high-impedance phones, I believe the LD III strikes a very good balance between quality and cost, and would be a better choice.

 

Cheers

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