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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 206

post #3076 of 10486
Quote:
Originally Posted by TrollDragon View Post

You will have to remove the jumpers to switch it into EF95 mode or cut off pin 7 on the 6DT6A but that would not be a good choice.

Find some long tweezers or a pair of hemostat's and pull the jumpers off.

Then PM me your mailing address and I'll mail you some long jumpers that are easier to get a hold of.


beerchug.gif
thanks for the offer but I've decided to just use 6/7 ef95. I live in Malaysia so shipping expensive
post #3077 of 10486
Quote:
Originally Posted by gibosi View Post
 

Made in Great Britain GE 6HM5/6HA5 followup:

 

GE Made in Great Britain by GE. Date unknown.

 

 

GE Made in Great Britain by Mullard/Blackburn, 1970 (B0F1)

 

 

First, both of these are excellent tubes on par with my recent favorites, GE 6AV6, Raytheon 6BE6W and Tung Sol 6DT6, with punchy bass with good articulation and detail, crystal clear and clean highs, and a wide and deep stage. The primary difference between the two GEs is warmth. As one might predict, the Blackburn-made GEs add just a bit of warmth to the upper bass and mid range. Interestingly, the difference in warmth between these two GEs is quite subtle and not as noticeable as between the Mullard/Blackburn and GE 6AV6.

 

Those of you who have been thinking about trying some triodes, but feeling a bit squeamish about the need to amputate and mutilate perfectly good tubes lol, I encourage you to get a pair of these GE 6HM5/6HA5. They require no strapping or mutilation of any kind. Simply set up the LD for EF95 tubes, plug them in and play.

 

Also, I have seen Sylvania 6HM5/6HA5 on eBay that appear to have the same internal construction as the GE-made tubes. And further, I recommend you avoid the short, squat 6HM5/6HA5 tubes.

 

Recommended.

 

Bought a pair of this cheap tubes.

 

Seller write "with Philips/Mullard tube codes".

I'm not sure, but seems have the same construction of GE Made in Great Britain by Mullard/Blackburn of Gibosi.

 

Can be the same ?

 

http://www.ebay.it/itm/300879467071?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

post #3078 of 10486
Quote:
Originally Posted by Iron58p View Post
 

Bought a pair of this cheap tubes.

 

Seller write "with Philips/Mullard tube codes".

I'm not sure, but seems have the same construction of GE Made in Great Britain by Mullard/Blackburn of Gibosi.

 

Can be the same ?

 

http://www.ebay.it/itm/300879467071?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

 

Yes, I saw those. They have the same plates, getter splash and Mullard tube codes, so I am pretty sure they are the same.

post #3079 of 10486
Quote:
Originally Posted by Audiofanboy View Post
 

Anybody else interested in joining me in double triode land lol?

 

Now, I just need to solve the floating triode issue (ground the heated yet unused triode)...

Yes I would, but I'd have to gather the parts...

 

More information given to me  from I <3 Tube Amps:

Quote:
 I suggest measuring the plate voltage. If it is higher than 3/4 of B+ then it suggests the existing passives are a better match to the two sections in parallel than one on its own.

Measure the plate & B+ voltages and see, then you could just parallel the triodes in the adapter socket without changing anything on the board.

:beerchug:

post #3080 of 10486

Planning to try to DIY socket savers for 7 pins anywhere I can start at? I can't seem to find any 7 pin socket savers after searching on google.

post #3081 of 10486
Quote:
Originally Posted by TrollDragon View Post
 

Yes I would, but I'd have to gather the parts...

 

More information given to me  from I <3 Tube Amps:

Measure the plate & B+ voltages and see, then you could just parallel the triodes in the adapter socket without changing anything on the board.

:beerchug:

 

Ach so.

 

I'm not even sure I would know how to measure those voltages though... At least no safely lol.

 

I'm pretty sure the board would be more suited for using just one triode, as it has a cathode bias with the exact value mentioned in the ECC88 datasheets. Not to mention that paralleled ECC88 sections could go up to 60mA of plate current, instead of ~10mA values usually... Gain would still be low to medium however.

 

I need someone with more skills (and tools) than me to test this lol!

post #3082 of 10486
Quote:
Originally Posted by Audiofanboy View Post
 

 

Ach so.

 

I'm not even sure I would know how to measure those voltages though... At least no safely lol.

 

I'm pretty sure the board would be more suited for using just one triode, as it has a cathode bias with the exact value mentioned in the ECC88 datasheets. Not to mention that paralleled ECC88 sections could go up to 60mA of plate current, instead of ~10mA values usually... Gain would still be low to medium however.

 

I need someone with more skills (and tools) than me to test this lol!

 

The best thing then would be to just let the other triode float unless is caused hum, then a ground would be needed. The ones with a center tapped heater would be better as well IMHO as the other triode would stay cold.

:beerchug:
post #3083 of 10486
Quote:
Originally Posted by TrollDragon View Post
 

 

The best thing then would be to just let the other triode float unless is caused hum, then a ground would be needed. The ones with a center tapped heater would be better as well IMHO as the other triode would stay cold.

:beerchug:

 

What about Oskari's suggestion of using only one dual triode tube, installed in one socket, and connecting the second triode to a socket saver plugged into the other socket? This would leave only the shield floating.

 
post #3084 of 10486
Quote:
Originally Posted by gibosi View Post
 

 

What about Oskari's suggestion of using only one dual triode tube, installed in one socket, and connecting the second triode to a socket saver plugged into the other socket? This would leave only the shield floating.

 

 

Very true; that was actually my original idea and starting point with that floating 12AT7 tube (but at that time, I was just in a hurry to get my concept tested). But then, I got to think about how a one-tube solution would look. And invariably, a single tube for both channels solution would always be somewhere on the ugly-weird continuum (UWC for short).

 

Basically, it would either look weird (one tube in one socket, other socket empty), or ugly (tube floating in between sockets or on a large adapter between sockets).

 

Still, if someone wants to give it a try, I say go for it. It's actually pretty easy to adapt these tubes, once you get the pin layout in your head!

post #3085 of 10486
Quote:
Originally Posted by TrollDragon View Post
 

 

The best thing then would be to just let the other triode float unless is caused hum, then a ground would be needed. The ones with a center tapped heater would be better as well IMHO as the other triode would stay cold.

:beerchug:

 

Definitely a better idea over the long term (and you get that free NOS triode after a few years when the first one weakens, not a leftover "poisoned" triode). I'll actually give that a whirl when I'm done with this ECC88 test.

 

Besides, that one 12Ax7 tube I tested, even plugged with lengths of Schiity aluminum cables, actually sounded pretty good. And these tubes could be interesting to use in parallel too. A 12AX7 has very high mu but low gm, so a paralleled 12AX7 would still have the same mu, but -supposedly- more gm and less noise (but more "Miller capacitance" or something, don't ask, I'm doing my best here).

 

Again, lads, let's get this stuff tested! A few different shops -in the US- that sell fairly cheap adapters/testers have been mentioned in this thread. All this stuff requires is a pair of adapters (or a DIY adapter made with a chopped up tube base) and some tubes.

post #3086 of 10486
Quote:
Originally Posted by gibosi View Post
 

 

What about Oskari's suggestion of using only one dual triode tube, installed in one socket, and connecting the second triode to a socket saver plugged into the other socket? This would leave only the shield floating.

 

 

If it could be made nicely it would be great but unsymmetrical... I can see a big pile O'Ugly with a wire jumping across.

 

I'd rather see an adapter rig where those with a MK II or MK III could plug it right in and those of us with a a MK IV just have to loosen the rings and spin them to the side for installation. 

B7G plugs on the bottom, B9A socket in the middle on a circuit board that runs across both plugs.

Could be covered in shrink tube, left open etc... many options!

:beerchug:

post #3087 of 10486
Quote:
Originally Posted by Audiofanboy View Post
 

 

Definitely a better idea over the long term (and you get that free NOS triode after a few years when the first one weakens, not a leftover "poisoned" triode). I'll actually give that a whirl when I'm done with this ECC88 test.

 

Besides, that one 12Ax7 tube I tested, even plugged with lengths of Schiity aluminum cables, actually sounded pretty good. And these tubes could be interesting to use in parallel too. A 12AX7 has very high mu but low gm, so a paralleled 12AX7 would still have the same mu, but -supposedly- more gm and less noise (but more "Miller capacitance" or something, don't ask, I'm doing my best here).

 

Again, lads, let's get this stuff tested! A few different shops -in the US- that sell fairly cheap adapters/testers have been mentioned in this thread. All this stuff requires is a pair of adapters (or a DIY adapter made with a chopped up tube base) and some tubes.

If you used the left triode on the left side and the right triode on the right, one could just switch the tubes side for side to implement the free NOS triode's... :D

:beerchug: 

post #3088 of 10486
Quote:
Originally Posted by Audiofanboy View Post
 

 

Very true; that was actually my original idea and starting point with that floating 12AT7 tube (but at that time, I was just in a hurry to get my concept tested). But then, I got to think about how a one-tube solution would look. And invariably, a single tube for both channels solution would always be somewhere on the ugly-weird continuum (UWC for short).

 

Basically, it would either look weird (one tube in one socket, other socket empty), or ugly (tube floating in between sockets or on a large adapter between sockets).

 

Still, if someone wants to give it a try, I say go for it. It's actually pretty easy to adapt these tubes, once you get the pin layout in your head!

 

Yes, any one-tube implementation is going to have a rather high UWC factor. Very true. lol

 
However, a major benefit to using only one tube is cost. The first time I searched for 6DJ8/ECC88 tubes on eBay was a real case of sticker shock. So it occurs to me that it would be a lot easier on the wallet to audition tubes as singles to determine winners and losers. And then, if reducing the UWC factor is a priority, I could proceed to purchase a few nice pairs. On the other hand, a high UWC factor may actually end up being a source of pride. :)
post #3089 of 10486

Personally my preference is sound and not aesthetics. However, sine some people seem to be concerned about the aesthetics, why not cover the wires and adapters with a ventilated tube cage?

 

Below is an example to give a conceptual idea, but there are obviously numerous different ideas that could apply.

 

 

http://diyaudioprojects.com/Schematics/images/Dynaco-ST35-Tube-Amplifier-Kit-cage.jpg 

post #3090 of 10486
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