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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 334

post #4996 of 10576
Quote:
Originally Posted by hypnos1 View Post
 

Gibosi : lots more 'bits 'n pieces' but yes, safer for someone not confident in adapter-making land...such a shame.

Was interested by your instruction to tie C3g's pins 3 and 4 together. I routed #4 to LD's #6...can you enlighten me - is it to do with how the LD socket itself is wired? I have had no adverse effects whatsoever....And yes, it appears from the tube data that pins 5 & 7 are linked internally.

 

Yes, it amounts to the same thing. Per my instructions, Grid 2 (pin 4) is strapped to the anode (pin 3) in the socket. Routing Grid 2 (pin 4) directly to LD #6 takes advantage of the fact LD straps LD #6 to LD #5 (anode) internally by default.

post #4997 of 10576
Quote:
Originally Posted by CollectoR13 View Post

Thank you very much guys!
I would like to follow the way gibosi mentioned with c3g...
But what kind of adapter should I buy to plug into the ef95 sockets?
And i would like to keep it as simple as possible, i want a clean look like artsi achieved with his adapter..


And the readymade 6sn7 adapters are unfortunatly not shipping to germany... (and quite expensive lol)


So my main problem is, i dont know which parts to use for what and how i could put them into a clean case..

 

Unfortunately, my solution trades off clean and neat for easy and ugly. But as Hypnos1 suggests, once you have everything working to your satisfaction using "Easy and Ugly," then your next task will be to figure out how to make two "Clean and Neat" adapters, with C3g on top and 6AK5 on the bottom. And as I have absolutely no experience with "Clean and Neat" adapters or C3gs, I cannot help you....

 

Parts for "Easy and Ugly":

 

For the C3gs.

 

You need two 8-pin loctal breadboard sockets like this:

 

http://www.ebay.com/itm/8-pin-loctal-breadboard-prototype-tube-socket-for-DIY-experimenting-NOT-OCTAL-/151163424139?pt=Vintage_Electronics_R2&hash=item23320acd8b

 

To connect the C3g to your Little Dot, you need two 7-pin Vector test sockets like this:

 

http://www.radiodaze.com/product/15450.aspx

 

Since you are in Germany, you may have to find other sources for these items, but the pictures should help you recognize what you are looking for.

 

Cheers,

 

Edit: Changed to reflect Oskari's correction.


Edited by gibosi - 2/12/14 at 4:28pm
post #4998 of 10576
Quote:
Originally Posted by gibosi View Post

 

For the C3gs.

 

If you leave the metal casing on, you need two 8-pin loctal breadboard sockets like this:

 

http://www.ebay.com/itm/8-pin-loctal-breadboard-prototype-tube-socket-for-DIY-experimenting-NOT-OCTAL-/151163424139?pt=Vintage_Electronics_R2&hash=item23320acd8b

 

If you remove the metal casing, you need two eu 8-pin breadboard sockets like this:

 

Why wouldn't the socket above work?

 

 

Nope. That's for rimlock tubes.

post #4999 of 10576
Quote:
Originally Posted by Oskari View Post
 

 

Why wouldn't the socket above work?

 

 

Nope. That's for rimlock tubes.

 

Ah, so the loctal socket works with or without the case.... This makes things a bit simpler.  And as I have no experience with tubes like the C3g, I need others to correct me when I go astray.... Thanks :)

post #5000 of 10576
Thank you guys, i will start searching for parts.
But what about the 6sn7?
There should not be a high risk to use them as power tubes, since the stock ones draw similar current, right?
Does anybody know another readymade adapter?
post #5001 of 10576
Quote:
Originally Posted by CollectoR13 View Post

Thank you guys, i will start searching for parts.
But what about the 6sn7?
There should not be a high risk to use them as power tubes, since the stock ones draw similar current, right?
Does anybody know another readymade adapter?

 

You will need to search for an adapter with 6SN7 on top and 6CG7 on the bottom.

 

It should work fine.... However, since my LD 1+ uses an op amp instead of power tubes, I just do not know.... 

post #5002 of 10576
Ok...
And if I would try the same method like for the c3g, like hypnos adviced, means taking some copper wire of 1mm and manually wiring from every socket to a top socket?
How should I wire from 6n30 to 6sn7?
post #5003 of 10576

Yesterday a small package appeared in my mailbox with a 1952 Brimar 13D1 / CV423. This is a British mil-spec version of the 25SN7 (25V version of the 6SN7), specifically designed for use in aircraft and other high-reliability applications. Interestingly, but probably of no consequence, it has two D-getters. I spent a couple hours with it last night and found it to be a very good sounding tube, very enjoyable.

 

Also in this series, there is the 13D2, which is essentially identical to a 6SN7.

 

And there is a 9-pin miniature 13D3 (premium version 6158 / CV4068). This appears to be very similar to the 6CG7 / 6FQ7, except for the pin-out. The 13D3 has the same pin-out as a 12AU7, and therefore, can be configured to run with either 6.3 or 12.6 heaters. However, if configured to run with 6.3V heaters, it draws 600ma, so either way, an external heater PS would still be necessary to use these in our Little Dots.

 

13D1,13D2,13D3 Datasheet

 

post #5004 of 10576
Quote:
Originally Posted by CollectoR13 View Post

Ok...
And if I would try the same method like for the c3g, like hypnos adviced, means taking some copper wire of 1mm and manually wiring from every socket to a top socket?
How should I wire from 6n30 to 6sn7?

 

The 6N30 has the same pin-out as the 6CG7, and therefore, my previous suggestion still holds: 

 

You will need to search for an adapter with 6SN7 on top and 6CG7 or 6DJ8 or 6N1 on the bottom. All these tubes, 6N30, 6N1, 6CG7 6DJ8 have the same pin-out. This is a common adapter and you should have no trouble finding one. I use one of these adapters to run 6SN7 tubes in my 9-pin breadboard socket.

 


Edited by gibosi - 2/13/14 at 8:23am
post #5005 of 10576
Quote:
Originally Posted by gibosi View Post
 

 

Unfortunately, I suspect that many of us, myself included, are a bit daunted by the task of building a proper set of adapters, plus the cost of a pair of C3gs. Perhaps you should consider starting a cottage industry? Perhaps "C3gLD" would be a good name? lol :)

 

For sure, I can't help but wonder how these compare to the E80CC....

 

gibosi...I think your statement - 'Perhaps "C3gLD" would be a good name?' - is actually FAR more apt than you may have realised...let me explain :

 

This afternoon, having done some research on 'pentode v triode', several lightbulbs have suddenly burst into the ol' grey matter.

With contrasting opinions regarding triode-strapped pentodes, it would appear to all come down (fairly obviously, really...) to how the amp is optimised - including their relative merits/deficiencies compared to 'true' triodes. As the LD was designed to use pentodes in this way (and not triodes per se), this would explain why the C3g has been accepted so gleefully - I believe it to be the proverbial 'prodigal son'...in other words, the tube that should have been in the LD - at least the later, more expensive, models - from the off. This would have taken them to a level far beyond the competition, I am sure. AND saved us all an immense journey in time, effort and money (although it has been a wonderful journey in many respects).

So, in reality, it seems we may have been going round in circles to some degree - we HAVE been making incremental improvements, but mostly because the WRONG pentodes were chosen in the first place!!! Obviously things are built to a price point, but I am sure that with bulk-buying and NO need for any (material) alteration to the unit, the extra price premium could have been minimal...

Ah well, I suppose this is easy to say with hindsight - but I still feel that perhaps further research at the outset may have had the LD team hit on a winner to beat all comers, anywhere near the price level.

 

Rant over... At least I can now enjoy my "LDMKIV C3g"

 

Cheers everyone.

post #5006 of 10576

Hi,

 

What is the difference between a 6SN7 tube and a

 

6BX7 and a 31BX7 tube?

 

6DN7 tube?

 

6BL7 tube?

 

Can these tubes be used in the LD with an external PS?

post #5007 of 10576
Quote:
Originally Posted by hypnos1 View Post
 

This afternoon, having done some research on 'pentode v triode', several lightbulbs have suddenly burst into the ol' grey matter.

With contrasting opinions regarding triode-strapped pentodes, it would appear to all come down (fairly obviously, really...) to how the amp is optimised - including their relative merits/deficiencies compared to 'true' triodes. As the LD was designed to use pentodes in this way (and not triodes per se), this would explain why the C3g has been accepted so gleefully - I believe it to be the proverbial 'prodigal son'...in other words, the tube that should have been in the LD - at least the later, more expensive, models - from the off. This would have taken them to a level far beyond the competition, I am sure. AND saved us all an immense journey in time, effort and money (although it has been a wonderful journey in many respects).

So, in reality, it seems we may have been going round in circles to some degree - we HAVE been making incremental improvements, but mostly because the WRONG pentodes were chosen in the first place!!! Obviously things are built to a price point, but I am sure that with bulk-buying and NO need for any (material) alteration to the unit, the extra price premium could have been minimal...

Ah well, I suppose this is easy to say with hindsight - but I still feel that perhaps further research at the outset may have had the LD team hit on a winner to beat all comers, anywhere near the price level.

 

Rant over... At least I can now enjoy my "LDMKIV C3g"

 

Cheers everyone.

 

Perhaps... But the major problem with strapping pentodes into triodes is that linearity is typically lost. And this is the feature that makes the C3g so attractive. Unlike most pentodes, a strapped C3g retains its linearity. It is just as linear used as a triode as it is a pentode. And in fact, the Cg3, triode strapped, is as linear as a "real very good triode" (http://www.jacmusic.com/techcorner/ARTICLES/English-neu/Portraits/C3g/C3g-C3m-info.html). So I am inclined to think that, electrically, the difference between using a "real very good triode" and a C3g in our LDs is negligible.

 

Regarding strapping the C3g, we have decided to use one of two common configurations, Grid 3 to the cathode and Grid 2 to the anode. However, another common configuration straps both G2 and G3 to the anode, as the EF91/92. You might remember that with many pentodes and heptodes, selecting one or the other of these strappings significantly changed the sound. Does anyone know if there is a "recommended" triode strapping configuration for the C3g? Absent that information, one of the advantages of my "easy and ugly" configuration is that it would be very simple to try both of these strappings to see if there is a difference....

 

Anyway.......  just some stuff that have been going around in my head.....

post #5008 of 10576
Quote:
Originally Posted by mordy View Post
 

Hi,

 

What is the difference between a 6SN7 tube and a

 

6BX7 and a 31BX7 tube?

 

6DN7 tube?

 

6BL7 tube?

 

Can these tubes be used in the LD with an external PS?

 

These might be OK, but they all draw some serious heater current: The 6BX7 / 6BL7 / 31BX7 heaters draw 1.5 amps and the 6DN7 heaters draw .9 amps. Personally, I think these are more like power tubes than drivers.....

post #5009 of 10576
Quote:
Originally Posted by hypnos1 View Post
 

 

gibosi...I think your statement - 'Perhaps "C3gLD" would be a good name?' - is actually FAR more apt than you may have realised...let me explain :

 

This afternoon, having done some research on 'pentode v triode', several lightbulbs have suddenly burst into the ol' grey matter.

With contrasting opinions regarding triode-strapped pentodes, it would appear to all come down (fairly obviously, really...) to how the amp is optimised - including their relative merits/deficiencies compared to 'true' triodes. As the LD was designed to use pentodes in this way (and not triodes per se), this would explain why the C3g has been accepted so gleefully - I believe it to be the proverbial 'prodigal son'...in other words, the tube that should have been in the LD - at least the later, more expensive, models - from the off. This would have taken them to a level far beyond the competition, I am sure. AND saved us all an immense journey in time, effort and money (although it has been a wonderful journey in many respects).

So, in reality, it seems we may have been going round in circles to some degree - we HAVE been making incremental improvements, but mostly because the WRONG pentodes were chosen in the first place!!! Obviously things are built to a price point, but I am sure that with bulk-buying and NO need for any (material) alteration to the unit, the extra price premium could have been minimal...

Ah well, I suppose this is easy to say with hindsight - but I still feel that perhaps further research at the outset may have had the LD team hit on a winner to beat all comers, anywhere near the price level.

 

Rant over... At least I can now enjoy my "LDMKIV C3g"

 

Cheers everyone.

 

Did you test the cg3 vs the cg3s?

 

also what is the price you paid if you don't mind me asking, they don't seem to have a price posted anywhere.

 

-edit-

 

i found the price list, looks like $40.86 each form JAC music or $66.01 each for the c3gs for the Siemens, Telefunken are absolutely ridiculous pricing!

 

(That's after a quick currency conversion from the euro using google, based on their "Export" price)

 

http://www.jacmusic.com/html/order/jacmusic-pricelist.PDF


Edited by mab1376 - 2/13/14 at 10:54am
post #5010 of 10576
Quote:
Originally Posted by gibosi View Post
 

 

These might be OK, but they all draw some serious heater current: The 6BX7 / 6BL7 / 31BX7 heaters draw 1.5 amps and the 6DN7 heaters draw .9 amps. Personally, I think these are more like power tubes than drivers.....

 

I have an amp that uses six 6BL7s as output tubes.

Wonderful low end.

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