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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 335

post #5011 of 10499
Quote:
Originally Posted by gibosi View Post
 

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 :)

 

It should also be noted that removing the bottom part with the spigot is a bad idea. With no spigot, the tube can be inserted eight different ways, only one of which is correct. The spigot also protects the evacuation tip.

post #5012 of 10499
Quote:
Originally Posted by gibosi View Post
 

 

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.....

 

Yes gibosi, the C3g is one VERY special pentode!  And certainly streets ahead of any triode I personally have tried...

 

As to trying both G2 and G3 tied to the anode, I may just be able to give it a go - in my first adapters I ran the strap wire externally, so I can instead link down to the anode at the socket - promise me all will be well!! Actually, I am only prepared to give it a try because I was fortunate enough to get a pair of C3gSs for no more than I paid for plain C3gs - couldn't resist! So it's back to adapter construction...at least I feel much more confident with that now...

Will keep you informed...

post #5013 of 10499
Quote:
Originally Posted by mab1376 View Post
 

 

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

 

As per my previous post, I have been lucky enough to get a pair of Siemens C3gSs - for under $70 the PAIR. So I look forward to comparing them with the 'plain' ones. But as they look such well-made tubes, I doubt there will be much difference... the main reason anyway was to have some in reserve - I do not want to take any chances with these babies!

JAC are pricey - I'm sure more tubes will trickle onto ebay. And as for the Telefunkens...NO WAY!!

post #5014 of 10499
Quote:
Originally Posted by Oskari View Post
 

 

It should also be noted that removing the bottom part with the spigot is a bad idea. With no spigot, the tube can be inserted eight different ways, only one of which is correct. The spigot also protects the evacuation tip.


Yes Oskari - GREAT care is needed, and certainly not for the faint-hearted! There is in fact a slightly raised 'marker' on the underside of the glass, which indicates the 1-8 demarcation (but you need fairly good eyes!). The protruding tip can also induce mild panic, so all in all it is far safer to leave the bottom on. In my case, I wanted to use minimal space for neatness in the adapter, and as I was using bare silver wire didn't want that metal spigot in the way! Needless to say, I took things VERY carefully and VERY slowly, checking things twice and thrice. So it can be done, but...

 

Thanks for pointing out possible pitfalls to anyone interested.

post #5015 of 10499
Quote:
Originally Posted by hypnos1 View Post
 

There is in fact a slightly raised 'marker' on the underside of the glass, which indicates the 1-8 demarcation (but you need fairly good eyes!).

 

It's quite a brilliant design that 'marker' being a spigot in itself for the socket that is the bottom metal part of the tube.

post #5016 of 10499
Quote:
Originally Posted by Oskari View Post
 

 

It should also be noted that removing the bottom part with the spigot is a bad idea. With no spigot, the tube can be inserted eight different ways, only one of which is correct. The spigot also protects the evacuation tip.

 

If... I get a pair of these, I would like to remove the top metal cap, but is it possible to easily do so without disturbing the metal base?

post #5017 of 10499
Quote:
Originally Posted by hypnos1 View Post
 

As to trying both G2 and G3 tied to the anode, I may just be able to give it a go - in my first adapters I ran the strap wire externally, so I can instead link down to the anode at the socket - promise me all will be well!! Actually, I am only prepared to give it a try because I was fortunate enough to get a pair of C3gSs for no more than I paid for plain C3gs - couldn't resist! So it's back to adapter construction...at least I feel much more confident with that now...

Will keep you informed...

 

Well, I have tied G2 and G3 to the anode on lots of pentodes with absolutely no problems, so it SHOULD be fine. lol :)

 

The published curves for the C3g strapped as a triode were generated using one or the other of these strappings, so one would think that somewhere there is some fine print indicating precisely how this was done. My gut feeling is that it does make a difference and they were most likely strapped identically to yours, Grid 3 to the cathode and Grid 2 to the anode, as this seems to be the most common strapping. On the other hand, it should be an interesting exercise to compare the two strappings to see if there is a difference.

post #5018 of 10499

Hypnos1,

 

Does this look right for the c3g to 6ak5 adapter pinout, i made it one to one to make it more readable.

 

cg3   6ak5
     
1   3
2   7
3   5
4   6
5   2
6   1
7   7
8   4

 

Also does the c3g use the same socket at the 6SL7 (octal?)

post #5019 of 10499
Quote:
Originally Posted by mab1376 View Post
 

Hypnos1,

 

Does this look right for the c3g to 6ak5 adapter pinout, i made it one to one to make it more readable.

 

cg3   6ak5
     
1   3
2   7
3   5
4   6
5   2
6   1
7   7
8   4

 

Also does the c3g use the same socket at the 6SL7 (octal?)

 

Yes, if you are going to make a "clean and neat" adapter similar to that of Hypnos1, this pin translation is the way to go. But no, an octal socket will not work. You want to use a LOCTAL socket.

post #5020 of 10499
Quote:
Originally Posted by gibosi View Post
 

 

Yes, if you are going to make a "clean and neat" adapter similar to that of Hypnos1, this pin translation is the way to go. But no, an octal socket will not work. You want to use a LOCTAL socket.

OK thanks.

 

Also i was looking for a PSU while my regulator board is on its way, i found one that outputs 12v at 500ma, is that sufficient or should i find something that outputs around 1amp?

post #5021 of 10499
Quote:
Originally Posted by mab1376 View Post
 

OK thanks.

 

Also i was looking for a PSU while my regulator board is on its way, i found one that outputs 12v at 500ma, is that sufficient or should i find something that outputs around 1amp?

 

My recommendation is at least 15V, as this gives you the option of running 12V tubes.

 

Using the adapter you found, Power (watts) = Volts X Amps. So 12 x .5 = 6 watts. So to determine that available amps for 6.3 tubes:  6 watts / 6.3V = .95 amp, which is quite adequate. But again, I would recommend at least 15V. Mine puts out 30V which allows me to run 25V tubes. :)

 

However, here's is a nice 16V adapter:

 

http://www.ebay.com/itm/IBM-AC-Adapter-08K8204-100-240V-1-5A-0-9A-16V-4-5A-/141192619642?pt=LH_DefaultDomain_0&hash=item20dfbc667a

post #5022 of 10499

Hi Everyone,

 

I've haven't viewed this thread for a very long time (the most recent and best tube I have for my MKIII is a pair of Yugo 6hm5 tubes) and I've spent the last few weeks trying to play catch-up. Not being the most technically gifted hamster on the wheel, I must confess to being at least partly baffled by recent developments. Money is very tight at the moment and I'm thinking of trying one of the new Octals and making an adapter. With this in mind I have a few questions I'm hoping someone might be willing to answer:

 

1. For an adapter, can I make a cheap one using metal pins from here:

http://www.ebay.com/itm/35pcs-IN-8-IN-12-IN-18-NIXIE-VFD-TUBE-PINS-VALVE-SOCKET-TO-PCB-UNIVERSAL-PIN-/121254898319?pt=Vintage_Electronics_R2&hash=item1c3b5aea8f

 

 

and then wiring them to a cheap Octal socket such as:

http://www.ebay.ie/itm/8-Pin-Gilard-Bakelite-Octal-Audio-Amplifier-Tube-Socket-/270649677461?pt=UK_Sound_Vision_Other&hash=item3f03fa5695

 

2. I am willing to do a little soldering and assuming I have made such an adapter correctly (I'd be very grateful if someone could point me in the direction of a wiring diagram?) can I bypass the need for an external power supply and use an 6sn7 tube and still see a marked upgrade from the Yugo 6hm5 tubes? If that is correct, what would be a good quality cheap 6sn7 tube be? Is this a good one:

http://www.ebay.com/itm/Tung-Sol-6SN7-GT-Tall-black-Plates-bottom-getter-Tested-/141170484884?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item20de6aa694

 

I will be feeding my MKII with a  LD DACII and for headphones using a pair of Byerdynamic t90s. The cans are bright so I guess I'm looking to tame siblence while retaining clarity etc.

 

Any help would be gratefully received as I'm trying to decide if I should stick or twist with regards to the 6hm5 tubes.

 

Thank you :)


Edited by samtheman - 2/14/14 at 3:44am
post #5023 of 10499
Quote:
Originally Posted by gibosi View Post
 

 

My recommendation is at least 15V, as this gives you the option of running 12V tubes.

 

Using the adapter you found, Power (watts) = Volts X Amps. So 12 x .5 = 6 watts. So to determine that available amps for 6.3 tubes:  6 watts / 6.3V = .95 amp, which is quite adequate. But again, I would recommend at least 15V. Mine puts out 30V which allows me to run 25V tubes. :)

 

However, here's is a nice 16V adapter:

 

http://www.ebay.com/itm/IBM-AC-Adapter-08K8204-100-240V-1-5A-0-9A-16V-4-5A-/141192619642?pt=LH_DefaultDomain_0&hash=item20dfbc667a

 

I have a Nintendo Wii adapter that outputs 12v at 3.7amp

 

that wouldn't hurt the voltage regulator board would it?

post #5024 of 10499
Quote:
Originally Posted by mab1376 View Post
 

 

I have a Nintendo Wii adapter that outputs 12v at 3.7amp

 

that wouldn't hurt the voltage regulator board would it?

 

It wouldn't hurt it at all. The tube is going to draw only what it needs. So even though the adapter can deliver about 7 amps into 6.3V, a 6SN7, for example, is going to draw only 600 milliamps.

 

Perhaps too far out of the box, but something to think about....  C3m tubes are easier to find than C3gs, probably because they have 20V heaters, instead of 6.3V. So you could purchase two 24V adapters, two voltage regulators and two C3ms....    :)

post #5025 of 10499
Quote:
Originally Posted by samtheman View Post
 

I've haven't viewed this thread for a very long time (the most recent and best tube I have for my MKIII is a pair of Yugo 6hm5 tubes) and I've spent the last few weeks trying to play catch-up. Not being the most technically gifted hamster on the wheel, I must confess to being at least partly baffled by recent developments. Money is very tight at the moment and I'm thinking of trying one of the new Octals and making an adapter. With this in mind I have a few questions I'm hoping someone might be willing to answer:

 

1. For an adapter, can I make a cheap one using metal pins from here:

http://www.ebay.com/itm/35pcs-IN-8-IN-12-IN-18-NIXIE-VFD-TUBE-PINS-VALVE-SOCKET-TO-PCB-UNIVERSAL-PIN-/121254898319?pt=Vintage_Electronics_R2&hash=item1c3b5aea8f

 

 

and then wiring them to a cheap Octal socket such as:

http://www.ebay.ie/itm/8-Pin-Gilard-Bakelite-Octal-Audio-Amplifier-Tube-Socket-/270649677461?pt=UK_Sound_Vision_Other&hash=item3f03fa5695

 

 

If you just want metal pins, these might be better:

 

http://www.ebay.com/itm/100pc-gold-plated-tube-pin-you-DIY-Tube-adapter-15-1mm-free-shipping-/200977094414?pt=US_Home_Audio_Amplifiers_Preamps&hash=item2ecb2b170e

 

And you are going to need some kind of a base to hold the pins. Some have glued the pins into these:

 

http://www.ebay.com/itm/British-Mullard-Tube-Pin-Straightners-NEW-OLD-STOCK-For-RCA-Telefunken-Brimar-/130832123892?pt=Vintage_Electronics_R2&hash=item1e7633c7f4

 

Quote:

 

Originally Posted by samtheman View Post
 

2. I am willing to do a little soldering and assuming I have made such an adapter correctly (I'd be very grateful if someone could point me in the direction of a wiring diagram?) can I bypass the need for an external power supply and use an 6sn7 tube and still see a marked upgrade from the Yugo 6hm5 tubes? If that is correct, what would be a good quality cheap 6sn7 tube be? Is this a good one:

http://www.ebay.com/itm/Tung-Sol-6SN7-GT-Tall-black-Plates-bottom-getter-Tested-/141170484884?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item20de6aa694

 

 

We believe that the Little Dot is designed to deliver no more than 500 milliamps per driver tube. The 6SN7 draws 600 milliamps. So I cannot in good conscience recommend that you skip the external power supply. By exceeding the design limits of the LD, you could very well be looking at smoke and fire....

 

The Tung Sol you are looking at is a very nice tube and that is a great price. However, I have no experience with the Byerdynamic t90, so I can't say if it would be a good match

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