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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 407

post #6091 of 10502
Quote:
Originally Posted by i luvmusic 2 View Post
 

 Finally i received my 12A regulator last night and started using it with my desktop power supply(12V-15A)and 6AS7 power tubes for Ld MK III and i noticed a fire hazard.Cable 4feet 18awg stranded is not enough to supply 7V-6.2A(as per my crappy multi meter).The cable it gets very soft and hot it nearly  burnt on me luckily i  noticed the burning smell  and when i grabbed it man it's that hot then i replaced it with 16awg and it's fine now.The 12A regulator it gets really hot as well so my guess is i'am screwed for the other two 7.5A regulator that i ordered it looks like i can't used just one of those 7A regulator to supply 6AS7 Power tubes and 6SN7 driver tube.

 

Correction the cable i've used is actually 20awg speaker wires not 18awg.

post #6092 of 10502
The 12AX7 adapter is just great! Thanks to @gibosi for the solderless design. There's a noticeable improvement in weight and clarity over the 6AK5 family. Running a NOS GE 5751 triple mica that just sounds great. Got a Telefunken 12AX7 that's distorting a bit in the low end so it's benched for now.

post #6093 of 10502

Hi Joe Doe,

 

Now when you are almost there having a Vector set up and a breadboard my humble suggestion is to buy an adapter  6SN7 to 12AX7. With this adapter octal tubes are simply plug and play. You will also need a voltage regulator and an external power supply.and you have to connect the two heater wires to the voltage regulator. It is well worth the the effort.

 

http://www.ebay.com/itm/NEW-DC-DC-Step-Down-Power-Module-4V-38V-to-1-25V-36V-5A-Voltmeter-Adjustable-/251525539037?pt=LH_DefaultDomain_0&hash=item3a901724dd

 

http://www.ebay.com/itm/1pc-6SN7-6SL7-TO-12AU7-12AX7-6-3v-filament-tube-adapter-/200952599533?pt=US_Home_Audio_Amplifiers_Preamps&hash=item2ec9b553ed

 

An old laptop power supply or similar will work fine. With the voltage regulator you can adjust the voltage from 6.3V to around 18V if your PS puts out 20V. Then you can shop for oddball 8V or 12V tubes that may be cheaper than the 6.3V equivalents.

post #6094 of 10502
Quote:
Originally Posted by mordy View Post
 

Hi Joe Doe,

 

Now when you are almost there having a Vector set up and a breadboard my humble suggestion is to buy an adapter  6SN7 to 12AX7. With this adapter octal tubes are simply plug and play. You will also need a voltage regulator and an external power supply.and you have to connect the two heater wires to the voltage regulator. It is well worth the the effort.

 

http://www.ebay.com/itm/NEW-DC-DC-Step-Down-Power-Module-4V-38V-to-1-25V-36V-5A-Voltmeter-Adjustable-/251525539037?pt=LH_DefaultDomain_0&hash=item3a901724dd

 

http://www.ebay.com/itm/1pc-6SN7-6SL7-TO-12AU7-12AX7-6-3v-filament-tube-adapter-/200952599533?pt=US_Home_Audio_Amplifiers_Preamps&hash=item2ec9b553ed

 

An old laptop power supply or similar will work fine. With the voltage regulator you can adjust the voltage from 6.3V to around 18V if your PS puts out 20V. Then you can shop for oddball 8V or 12V tubes that may be cheaper than the 6.3V equivalents.

Thanks for the suggestion mordy. I will certainly look into this upgrade after I get some more time with my current set up. It's crazy how versatile this little amp can be for tube rollers!

post #6095 of 10502
Quote:
Originally Posted by JoeDoe View Post

The 12AX7 adapter is just great! Thanks to @gibosi for the solderless design. There's a noticeable improvement in weight and clarity over the 6AK5 family. Running a NOS GE 5751 triple mica that just sounds great. Got a Telefunken 12AX7 that's distorting a bit in the low end so it's benched for now.

 

Welcome to the LD Double Triode club! :)

 

I thought the 5751's were very good tubes, especially the GE and Sylvania. And there are many more very good double triodes you might want to try. But for now, enjoyl :)

post #6096 of 10502
Quote:
Originally Posted by MIKELAP View Post
 

                                                                                                                                                                                                                                                                                                                                                               CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), default quality

 

Might need more than that! :wink_face:

 

Hey mikelap.

 

Looks like I must have sold my soul to the Devil...'cos not only do the 6as7s work in the IV SE, but even with just 1 in the right channel and the Psvane in the left the result is downright mind-boggling! The difference already sounds very similar to what you hinted at coming from your Woo...further info below...I still cannot believe that what I jokingly (with forlorn hope) tossed in the air re using them in our LDs has actually come into being - and beyond my wildest expectations. The Woo will have to wait a good while now lol!

 

 

Quote:
Originally Posted by TrollDragon View Post
 

This is my MK IV board, the SE should be the same except for upgraded capacitors and jacks.

The two resistors circled in red are the 150Ω cathode resistors that Artsi spoke of, these resistors are 1 Watt. The two White Square resistors on the right edge of the board are 5 Watt sized just for reference.

 

If running the 6AS7's as power tubes with the 1W resistors draws too much current, the most that would likely happen is you would just burn out those two resistors. The heat / flame generated when these resistors burn would cause much stress to the two caps on either side. If it doesn't cause any trouble to the circuit board underneath as well.

 

This is a 1/4 Watt resistor with too much power through it, the bigger the wattage the better the burn. :)

 

So What Do?

 

New resistors come with long legs, you could put 5 Watt or 10 Watt resistors in place of these 1 Watt's for a few dollars each. Bend the legs and the resistor would have to be mounted in the air a little as it would not fit in the other resistors space.

 

Then the resistors would not burn out, the transformer would... :wink_face:

 

I have to thank you once more TD for showing me the target resistors...despite a nasty crick in my neck after hours of peering inside the unit with temp probe in hand, fortunately it looks like once again the LD (MKIV SE at least) heaps surprise upon surprise. With the outside temp of said target being 56/57C after 1 hour and just 59C after 4 hours' continuous play, I think all should be OK, yes? - WELL below max operating temp, I believe...so hopefully no nasty surprises in store;) 

 

I can only hope other models are similarly forgiving...

 

 

And so now, guys, an update on this most unexpected development :

 

After a good many hours of my favourite test tracks, and much to my disbelief, my initial comments only just touched the surface.

The dynamic sound and extra upper bass and lower mids did not come at the expense of anything else whatsoever...on the contrary, there's even more detail across the entire spectrum. It would appear that no matter what part of the system is changed/upgraded, the C3gs maintain a perfect balance in all respects, and just keep on delivering more and more. Coupled with the 6AS7G (and still only in the right channel, with the Psvane in the left), at first it's almost as though there's too much detail, but when you hear it with pinpoint precision and placement, the end result is truly mind-blowing. This gives true holographic imaging and soundstage. Again, this doesn't come with a heavy price-tag...vocals (especially female) stay nicely, and intimately placed - not lost somewhere in the 3D stage!

There is increased tonal range, both vocally and instrumentally, and a particular quality of reproduction that I have never properly noticed before, exemplified by, of all means, a tambourine in an old ELO track - ie you could hear the shake running around its rim like a musical ferris wheel (moving VERY fast, mind you!)...amazing...

Bass had even more depth - not heavy-metal heavy - but with exquisite detail. And as for treble...sweet, delicate (especially with percussion), detailed and with delicious decay hardly does it justice.

 

Anyway, that's just a taster of what the 6AS7G has delivered...had better get back to the "roller widow" before I'm in  the dog-house!.

 

Will update again when I've finished the adapter for magical tube #2...

 

Cheers for now.

 

In case you missed the pic first time round :

 


Edited by hypnos1 - 5/11/14 at 12:42pm
post #6097 of 10502

Hi hypnos1,

 

When trying the RCA 6AS7G as a driver, I found that the RCA/GE 6080 tubes were more to my liking. Perhaps you want to try a 6080 as well since they can be found very inexpensive.


Edited by mordy - 5/11/14 at 1:05pm
post #6098 of 10502

Hi,

 

Finally got the guts to cobble together an all sub miniature set up consisting of three Raytheon 1957 JAN-6832 tubes. No external PS is needed. I opted for a solderless solution for the power tubes and used two 9 pin socket extenders with small pieces of solid copper 18 gauge insulated wire to wedge the long leads into the pin sockets. It is a delicate job for fumbly fingers but doable.

The little red dynamite charges are the eight little push pins made of the copper wire to keep the leads in place.

Here is the experimental set up (euphemism for inability to make it look elegant) - notice the flying driver tube:

 

Hey, it works, no hum unless I crank up the volume too high. The sound is good with the bass going very low. However, the slam and impact in the bass could be be better - hopefully it will improve with burn in. But it does not look pretty - let's try a night view:

 

Looks better, but here is a real pretty picture from last week - spring is finally here!

 

 

Happy tube rolling!

post #6099 of 10502
Quote:
Originally Posted by mordy View Post

 

Finally got the guts to cobble together an all sub miniature set up consisting of three Raytheon 1957 JAN-6832 tubes. No external PS is needed. I opted for a solderless solution for the power tubes and used two 9 pin socket extenders with small pieces of solid copper 18 gauge insulated wire to wedge the long leads into the pin sockets. It is a delicate job for fumbly fingers but doable.

 

Hey, it works, no hum unless I crank up the volume too high. The sound is good with the bass going very low. However, the slam and impact in the bass could be be better - hopefully it will improve with burn in. But it does not look pretty - let's try a night view:

 

As with the 6DJ8's, I just don't think these little sub-miniatures can move enough current to function as power tubes.... But as you haven't had time to burn them in yet, I just might be wrong...   :)

post #6100 of 10502
Quote:
Originally Posted by mordy View Post
 

Hi hypnos1,

 

When trying the RCA 6AS7G as a driver, I found that the RCA/GE 6080 tubes were more to my liking. Perhaps you want to try a 6080 as well since they can be found very inexpensive.

 

Hi mordy.

 

Now that it looks like the 6AS7/6080 family are options for the powers, (yet) another quandary appears...having already spent a fortune on tubes, there's now this family to explore - "she who must be obeyed" is not sounding too happy!! I must admit I too am beginning to think enough is enough. This time, I really do think I have pushed the humble LD to its absolute limits. From stock to what I am hearing now is just way beyond belief, lol. I am of the firm belief that only the uber expensive "coke bottle" 5998 and equivalents would deliver more. And that is definitely NOT an option - for me, anyways. Plus, the law of diminishing returns would surely apply here, given my new level of sound!

 

Re the 6080 that you prefer, you mentioned that it had more bass than the 6AS7, but with a shade less detail? As I am now getting all the depth of bass I would ever want, I much prefer to have the extra detail...especially as this is an area where the C3gS excels bar none. And from a good few researches, the nod seems generally to go to the 6AS7G. Thanks for your interest though, mordy.

So it looks (once again!) as though I can now rest on my laurels and begin to hear anew all my favourite music as I have never heard it before, and at least without having spent thousands of pounds/dollars :k701smile:.

 

BFN and happy (continued!) rolling

post #6101 of 10502
Quote:
Originally Posted by hypnos1 View Post

 

Is there a company that makes tube adapters such as you have made for your LD? as I am not the most skilful when it comes to DIY projects. I also wouldn't even know what components to buy if I were to undertake making the adapters myself. If there isnt a company that makes them a run through of how you made them would be much appreciated :)


Edited by sgbwill2 - 5/12/14 at 6:50am
post #6102 of 10502
Quote:
Originally Posted by sgbwill2 View Post
 

Is there a company that makes tube adapters such as you have made for your LD? as I am not the most skilful when it comes to DIY projects. I also wouldn't even know what components to buy if I were to undertake making the adapters myself. If there isnt a company that makes them a run through of how you made them would be much appreciated :)

 

Hi sgbwill2.

 

Good to see new blood interested in what we have been discovering over these past many months...hopefully you have the time - and patience! - to look back over all the guys' work...you should find it quite interesting and informative.

As for my own set-up, if you're interested in the C3gs as drivers you are in luck..happydiy998 on ebay.com supplies C3g to 6AK5 adapters for $29.50 each...pricey, but I wouldn't recommend you even try going DIY if you don't have much experience in this area...too many possible pitfalls, believe you me!! The power tubes are 1 Psvane CV181 - TII, which is basically the same as a 6SN7 and 1 6AS7G. Again, you can get adapters for the 6SN7 - ebay.com, 6SN7 to 6CG7 for about $19.90 each. These and the drivers are then plug and play. With the MKIV SE it is simply a question of removing all the brass bits, then the adapters fit snugly into the LDs sockets. Other models that have rings atop the sockets need socket extenders also...if this applies to you, let us know and some of the other guys I am sure will chip in and advise you...

As for the 6AS7G as power tube, I can only vouch for how it suits the MKIV SE, but again I'm sure others here with more knowledge than myself may have additional input. This tube family can again be used with the 6SN7 to 6CG7 adapter...BUT THEY REQUIRE A SEPARATE POWER SUPPLY FOR THE HEATERS! Pins 4 and 5 on the 6CG7 section MUST NOT enter the LD. If you are interested in going this route, there is plenty of info going back a good few pages that I suggest you read VERY carefully, and post any doubts you may have. There's a wonderful bunch of very helpful guys in this thread.

 

Hopefully this has given you a bit more info to be getting on with...let us all know how you get on.

 

Cheers for now...supper calls!

post #6103 of 10502

Thanks for the reply. I think I will be getting myself some c3gs for my LD MKIII soon as they sound incredible from how you and some others have been describing them. The 6AS7G's also sound promising though the thought of having to solder on external heaters is putting me off :D Have you tried them without the external heaters? I guess they would overheat quickly thats why you soldered them on in the first place but not having to solder them on would save me a lot of hassle.As for the 7 pin extenders hopefully I can remove the brass rings on my LD though I have yet to check if its possible. The psvane's might be the way I will have to go though they are very pricey so a standard 6SN7 might have to do.


Edited by sgbwill2 - 5/12/14 at 2:49pm
post #6104 of 10502
Quote:
Originally Posted by sgbwill2 View Post
 

...............The 6AS7G's also sound promising though the thought of having to solder on external heaters is putting me off :D Have you tried them without the external heaters? I guess they would overheat quickly thats why you soldered them on in the first place but not having to solder them on would save me a lot of hassle.As for the 7 pin extenders hopefully I can remove the brass rings on my LD though I have yet to check if its possible. The psvane's might be the way I will have to go though they are very pricey so a standard 6SN7 might have to do.

 

Two 6AS7's draw 5 amps. The LD can provide, at most, 2.5 amps. If one was to try them without an external heater power supply, I can't see anything good happening. But I can easily imagine smoke and flames....

 

While I have never heard a psvane, it is worth noting that some believe them to be very good while others believe that many old-stock 6SN7's are better. Given that old-stock 6SN7's can often be had for not much money, my advice is to start cheap, and then, if you are not satisfied, move up to more expensive tubes.

 

I suggest that you check out the Reference 6SN7 thread to help you decide which ones you would like to try.

 

http://www.head-fi.org/t/117677/the-reference-6sn7-thread

post #6105 of 10502
I realize this may be the wrong thread for this, but I've decided to sell my 1+. If anyone is interested PM me referencing this post and I'll cut you a deal.
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