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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 379

post #5671 of 7354

Just wanted to follow up with the 6HM5 sylvania tubes. I found out that they are truly NOS tubes. And that crispy sibilance is normal with never before used tubes. They are really impressing me. So much effortless power and dynamism. They are superior to the Mullard 8083's in almost every way except for Musicality. I will still use the 6HM5 as my primary to go to tubes. Is there anything else that is more musical I should try. For my Little Dot + hybrid. Preferably tubes that are plug and play. I like Smooth highs and deep tight bass. Colored musical tubes where my preferences lie.

post #5672 of 7354

You have the Sylvania 6HM5 and as I haven't heard them, I can't say for sure how other tubes compare. But since 6HM5 are cheap, you might want to try the other tall-bottle types, GE and Yugoslavia EI.

 

The 6DT6 (set your amp to EF92) is worth trying. I found the RCA and Tung Sol to be very good. And I believe that others liked the Sylvania.

 

Again, these will all likely be NOS, and as you have noticed, you will need to burn them in.

post #5673 of 7354
Quote:
Originally Posted by gibosi View Post
 

 

I am not completely surprised as the Sylvanias are not as balanced as your Psvanes appear to be. As I find this tube to be somewhat dry and bass deficient, I can imagine that it would pair very well with a warm, bassy gray-glass RCA. But it appears that your C3s have better synergy with a more balanced output tube.

 

Yo gibosi...that 'dryness' is surely what is killing the C3gS magic. The delicious reverb and decay, especially on bass drum/piano/acoustic string notes, is just not being delivered by the Sylvanias (and yet the VT-231s are normally supposed to be so good at nearly everything, no?). And this alone methinks would have a very negative effect on the wonderful, spacious soundstage...the slightly more emphasis on mids, though sometimes very attractive, also contributes towards this effect I am sure - why is there always a trade-off with all the things we love?! Something to do with "you can't have your cake and eat it?...Life's a b***h, ain't it?...

Ah well, mustn't be greedy I suppose. All I can say is I have been EXTREMELY lucky to find the Psvanes matching the C3gSs so brilliantly - perhaps it's their developers' clever remit to combine the qualities of both the CV181 and  6SN7. Whatever, they are proving to be way beyond what I (and I am sure many others) was expecting from Far Eastern tube makers...

post #5674 of 7354
Quote:
Originally Posted by hypnos1 View Post
 

 

Yo gibosi...that 'dryness' is surely what is killing the C3gS magic. The delicious reverb and decay, especially on bass drum/piano/acoustic string notes, is just not being delivered by the Sylvanias (and yet the VT-231s are normally supposed to be so good at nearly everything, no?). And this alone methinks would have a very negative effect on the wonderful, spacious soundstage...the slightly more emphasis on mids, though sometimes very attractive, also contributes towards this effect I am sure - why is there always a trade-off with all the things we love?! Something to do with "you can't have your cake and eat it?...Life's a b***h, ain't it?...

Ah well, mustn't be greedy I suppose. All I can say is I have been EXTREMELY lucky to find the Psvanes matching the C3gSs so brilliantly - perhaps it's their developers' clever remit to combine the qualities of both the CV181 and  6SN7. Whatever, they are proving to be way beyond what I (and I am sure many others) was expecting from Far Eastern tube makers...

 

Hey Hypnos1,

 

How do i get the black metal shields off of the c3gs'?

post #5675 of 7354
Quote:
Originally Posted by mab1376 View Post
 

 

Hey Hypnos1,

 

How do i get the black metal shields off of the c3gs'?


Am off to bed now, mab, but tomorrow I will take some photos of the procedure - they do look much prettier with them off!!

 

Cheers.

post #5676 of 7354
Quote:
Originally Posted by gibosi View Post
 

You have the Sylvania 6HM5 and as I haven't heard them, I can't say for sure how other tubes compare. But since 6HM5 are cheap, you might want to try the other tall-bottle types, GE and Yugoslavia EI.

 

The 6DT6 (set your amp to EF92) is worth trying. I found the RCA and Tung Sol to be very good. And I believe that others liked the Sylvania.

 

Again, these will all likely be NOS, and as you have noticed, you will need to burn them in.

Gibosi, What do you think about the Amperex 6BY6 tubes? They are heptodes. Is there any specific sonic characteristics that seperate the Heptodes from the Triodes?

post #5677 of 7354
Quote:
Originally Posted by hypnos1 View Post
 

 

Yo gibosi...that 'dryness' is surely what is killing the C3gS magic. The delicious reverb and decay, especially on bass drum/piano/acoustic string notes, is just not being delivered by the Sylvanias (and yet the VT-231s are normally supposed to be so good at nearly everything, no?).

 

 

From what I have read, "VT-231" is nothing more than an inventory number used by the US Navy during WWII. All you can really infer from this designation is they were produced in the 1940's in support of the war. Evidently, they are identical to 6SN7GTs made during the 1940's for civilian use.

 

My impression is the Sylvania VT-231 is prized by those who combine more than one 6SN7 together to counterbalance deficiencies in each to achieve a desired sonic signature. But as your C3gs are very linear, and likely have no significant deficiencies, I believe they require an output tube with more balance than the Sylvania. If you are still interested in trying old-stock 6SN7, I would suggest a pair of Raytheon VT-231. There are two versions, and the one with 2 free support posts and flat plates seems to be preferred over the other. Or a pair of Tung Sol "Mouse Ears." In my experience, both of these have pretty good balance.

post #5678 of 7354
Quote:
Originally Posted by henree View Post
 

Gibosi, What do you think about the Amperex 6BY6 tubes? They are heptodes. Is there any specific sonic characteristics that seperate the Heptodes from the Triodes?

 

First, you should realize that in order to use pentodes and heptodes in the LD, it is necessary to convert them into triodes. The LD does this on the circuit board for EF91, 92 and 95. The problem with heptodes is there are two more grids to deal with. It is certainly possible to run 6BY6, 6BE6 and 6CS6 heptodes in our Little Dots, and in fact a number of us, including myself have done this. The easiest way is to run them in the EF92 mode.

 

In my experience, with very few exceptions, such as the C3gs, the only advantage to converting pentodes and heptodes into triodes is cost. These tubes are typically very cheap. The downside is that in the conversion process, linearity decreases and distortion increases. That said, it is completely harmless and as cheap as they are, why not? :)

post #5679 of 7354

And I should add, one of the reasons the 6HM5 sounds better than the Mullard 8083 is the 6HM5 is a true triode. Prior to running double triodes, the only tube I found that was better than the 6HM5 is another true triode, tubes in the 6AV6 / 6AT6 / 6AQ6 family. These three tubes differ only slightly, and in our LDs, they are essentially identical. Again, these are true triodes. However, there are also two diodes in the same bottle. So we cut off the diodes, pins 5 and 6, and now we have true triodes that run perfectly wonderful in the EF92 mode.

 

Food for thought.... :)

post #5680 of 7354
Quote:
Originally Posted by hypnos1 View Post
 


Am off to bed now, mab, but tomorrow I will take some photos of the procedure - they do look much prettier with them off!!

 

Cheers.

Thanks, I appreciate it!

post #5681 of 7354
Quote:
Originally Posted by gibosi View Post
 

 

First, you should realize that in order to use pentodes and heptodes in the LD, it is necessary to convert them into triodes. The LD does this on the circuit board for EF91, 92 and 95. The problem with heptodes is there are two more grids to deal with. It is certainly possible to run 6BY6, 6BE6 and 6CS6 heptodes in our Little Dots, and in fact a number of us, including myself have done this. The easiest way is to run them in the EF92 mode.

 

In my experience, with very few exceptions, such as the C3gs, the only advantage to converting pentodes and heptodes into triodes is cost. These tubes are typically very cheap. The downside is that in the conversion process, linearity decreases and distortion increases. That said, it is completely harmless and as cheap as they are, why not? :)

Thanks for the info. Generally speaking would the 6BY6 be a step down from the Sylvania 6HM5 tubes I have right now? The 6BY6 don't need to be altered other than changing the jumpers correct? I don't mind my music being colored. I just want a  very musical presentation first. 

post #5682 of 7354

Ummm... Again, as I said above, prior to running double triodes, the 6HM5 and 6AV6 were the best tubes I tried. So in my opinion, the 6BY6 would be a step down....

 

But hey! Heptodes are cheap! Have some fun! Buy a bunch and see what YOU think! :)

 

And in fact, you can safely run these tubes in either the EF95 or EF92 setting. (We also tried strapping them in a couple of different ways, which resulted in a total of 4 different triode-conversion configurations.) So try both EF95 and EF92 and you will be able to hear for yourself what different triode-conversion configurations do to the sound. And you will be able to judge for yourself how these converted triodes compare to the Sylvania 6HM5, a true triode.

 

Cheers

post #5683 of 7354
Quote:
Originally Posted by mab1376 View Post
 

 

Hey Hypnos1,

 

How do i get the black metal shields off of the c3gs'?

 

Right then mab, here we go...don't want to sound like Mother, but please take VERY careful note of the pointers...would hate for anything to go amiss with these little treasures:

 

1. The bottom outer rim of the canister is folded (fairly soft metal) over the metal protective tube base. So, using a pair of small (preferably) pliers, gradually and gently prise that rim away, as per photo #1 - you don't need to pull it too far away :

 

 

At this point you can see clearly the different-shaped cut-out for orientating the base to tube (church window as opposed to round)...

 

 

2. You may well have to gently 'wiggle' the metal base and/or adjust the prised rim to lift out said base. NOTE : there are 3 washers - over pins 2,5, and7 (not exactly sure why...perhaps something to do with heat transference?). They might possibly come adrift as you remove the base...

The protruding "locator" on the side of the central metal cylinder corresponds to the mid-point between pins 1 and 8.

This mid-point is marked on the glass bottom by a tiny pimple, located at the 6 o'clock position in photo #2 - the pins running clockwise from #1(to the left of mid-point as you look from below)...

 

 

Note the 'church window' of the metal base sits over pin #6 - (I'm sure 2, seated either side of the 'mid-point' would have been much less confusing lol!).

 

3. You now have 2 options, of course...#1: pop it straight into the adapter, which would need EXTREME care - you would have to clearly mark that mid-point on the side of the tube, to ensure correct location with the indent on the adapter. Also, that protruding glass tube seal looks rather vulnerable - probably no trouble when pushing the tube in (still with care..), but potentially a problem if having to waggle hard to pull it out!

Option 2 is much safer, of course : glue the base back on...as there's a small gap between metal and the glass, something like a 2-part rapid-setting clear resin/adhesive applied to the inside rim of the metal base should do the trick...or whatever your preference is, mab. And don't forget those 3 washers!

Just make DOUBLY sure of the positioning - church window to same, and protruding metal 'locator' to glass 'pimple' - and all will be well...

 

If ever you should have a problem with a base - eg (not that it would happen, I'm sure!) : the base comes unstuck, and then gets damaged prising it out of the adapter (aren't I a cheerful chappie?!) - have no fear, I've a couple of spare ones you could have.

 

Hopefully, mab, this is all the info you'll need. So I shall wish you all the best with the project - it certainly is worth the (minimal) effort to reveal the beauty hidden within!

Any problems/questions, just post or PM me...

 

 

Cheers...and remember the 30-50hrs burn-in needed!!


Edited by hypnos1 - 3/31/14 at 4:59am
post #5684 of 7354

Just wondering - what is the purpose of the metal covers for the tube?

 

Does the C3m tube require a different voltage? Seems it is less expensive than the Cg3.

post #5685 of 7354

c3m uses 20v heaters. c3g is typical 6.3v.

 

I read somewhere that the purpose is to keep the heat in but I'm not certain, I would think its to shield from EMI as well.

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