[barbazz]

Keeping up with the testing of some "are you sure it will not burn your house" tubes. This time, some Philips ECH83, made in Heerlen in the second week of March 1965. I was not expecting too much, to be honest. They are Triode-Heptodes who not only share the heater but also the cathode... Even worse, the cathode pin is also connected to grid 5 of the heptode. So, I've decided to try the triode and, if that didn't work, then strap the heptode into a triode. Hit the power button, and...

...these are some of the better tubes I've tested lately!!! Powerful bass, well-defined highs, and a huge sound stage. Great stuff!

 

[jsk ksj]

Is that the bomb Keanu Reeve's defused in Speed ?

 

[barbazz]

Is that the bomb Keanu Reeve's defused in Speed ?

LOL

Something along those lines. But I didn't use a red wire. There's always a red wire in those movies

"Need your help to defuse this bomb"
"Just cut the red wire"
"There's no red wire"
"What you mean, there's no r.."
Kaboom

 

[jsk ksj]

 

[RaynFox]

As an experiment about 45 minutes ago I powered up my MKIII with 6EM7 output (power) tubes on 6SN7 adapters. 6EM7 have two dissimilar triodes under the same glass, one low mu and the other higher, and it draws .925 Ah. It didn't explode, hasn't overheated and sounds good and has ample power. It tentatively confirms we can successfully run at least some dissimilar triodes as power tubes. There's some push-pull in the circuitry, and I don't know if that eventually could be a problem for the tubes or Little Dot. While I'm not experienced with reading schematics, it looks like the little dot mkIII might use triode #1 and triode #2 in the same order in both channels. It sounds good non-matched with one RCA and one Raytheon. I look forward to listening to a cosmetic pair. The 6EM7's are frontrun by Western Electric 409A driver tubes deployed in EF91/92 mode. I find the Western Electric has a nice midrange and I feel it probably sounds better than a variety of $2-$3 per tube Soviet 6J2P(-ev) tall and short bottle pairs I have auditioned. The 409A, 6J2P, 6AS6, and 5725 are probably all sensible equivalents.

You really got me wanting to order and try 6EM7 tubes. Are they fine in 6SN7 adapters or is it not good after some time?

 

[Cognomen]

You really got me wanting to order and try 6EM7 tubes. Are they fine in 6SN7 adapters or is it not good after some time?

All of the following tubes are plug and play in 6SN7 adapters. The 6EM7 draws .925Ah. The 6EA7 and 6GL7 seem to have been substitutes for televisions but draw 1.05Amps. My MKIII transformer is rated for 1.25Amps (v2 and later; the first version is probably lower). I regard 1.05 amps as getting up there in the event the quality control for manufacturing the transformer means it might actually handle less than 1.25 Amps. I have been listening to 1.05 Ah 6EA7 and 6GL7 for about 50 hours with no problems or noticeable increased heat. I have 6EA7 with only that printed on them. My 6EM7's all have 6EA7 printed on them. And I have a pair of Amperex with 6EA7, 6GL7, and 6EM7 printed on them. I like the sound of these tubes and regard the few I have listened to as sounding different than lower priced 6SN7 perhaps especially in terms of a bit more/better bass but perhaps slightly less euphonics above that. I have not heard highly esteemed and expensive 6SN7's though. I do not have good enough hearing to become a very good musician and am not as detailed and exacting as audiophiles. The thing I can have in common is unfortunately verbosity.

 

[RaynFox]

All of the following tubes are plug and play in 6SN7 adapters. The 6EM7 draws .925Ah. The 6EA7 and 6GL7 seem to have been substitutes for televisions but draw 1.05Amps. My MKIII transformer is rated for 1.25Amps (v2 and later; the first version is probably lower). I regard 1.05 amps as getting up there in the event the quality control for manufacturing the transformer means it might actually handle less than 1.25 Amps. I have been listening to 1.05 Ah 6EA7 and 6GL7 for about 50 hours with no problems or noticeable increased heat. I have 6EA7 with only that printed on them. My 6EM7's all have 6EA7 printed on them. And I have a pair of Amperex with 6EA7, 6GL7, and 6EM7 printed on them. I like the sound of these tubes and regard the few I have listened to as sounding different than lower priced 6SN7 perhaps especially in terms of a bit more/better bass but perhaps slightly less euphonics above that. I have not heard highly esteemed and expensive 6SN7's though. I do not have good enough hearing to become a very good musician and am not as detailed and exacting as audiophiles. The thing I can have in common is unfortunately verbosity.

Thank you for the reply! Do you personally think, that a pair of RCA 6EM7 could be a good experiment for €50 ? Right now I'm using PSVANE 6SN7 and I'm really curious, but €50 is a lot, still could be a pretty nice experiment - I'd like to know your personal opinion though.

 

[Moak]

[size=18.0pt]4. POWER TUBES[/size]

4.1 Overview

The power tubes reviewed in this guide only applies to the current production Mk series amps. Unlike their impressive flexibility with signal tubes, most current production Little Dot amps can only accept 6N6/6H6P power tubes with the exception of the MkIV which can accept the 6H30Pi (for clarification refer to this chart). It is important for the longevity and performance of your amp that the power tubes you use are matched pairs, otherwise it is common for power tubes and other components in the amp to fail pre-maturely due to badly matched tubes. I have had several power tubes fail within 100 hours of use due to matching issues.

Is it necessary to replace power tubes? Is it enough to just use good driver tubes? I am currently using the MKII with stock tubes (power tubes 6N6/driver tubes 6J1).

 

[mordy]

Is it necessary to replace power tubes? Is it enough to just use good driver tubes? I am currently using the MKII with stock tubes (power tubes 6N6/driver tubes 6J1).

In the Little Dot tube amps the conventional wisdom was that power tubes account for some 15% of the sound. If you want to try different sound signatures you get much better results with changing the driver tubes.
As for longevity, vacuum tubes last a very long time - years.
There are other tube amps with a different construction where you roll the power tubes for different sound signatures.

 

[Moak]

In the Little Dot tube amps the conventional wisdom was that power tubes account for some 15% of the sound. If you want to try different sound signatures you get much better results with changing the driver tubes.
As for longevity, vacuum tubes last a very .

Thanks for the info.
Does it make sense to replace the original 6N6 tubes with 6N6P or better 6N6P gold grid or is that unnecessary?
Today I bought Voshkod 6ZH1P-EV for the standard 6J1 driver tubes.

 

[mordy]

Thanks for the info.
Does it make sense to replace the original 6N6 tubes with 6N6P or better 6N6P gold grid or is that unnecessary?
Today I bought 6ZH1P-EV for the standard 6J1 driver tubes.

The best 6N6 tubes have a DR suffix but are very pricey. A cheaper variant that sounds a little better than the standard 6N6 tubes has an IR suffix.
However, if you bought very inexpensive 6SN7 tubes and the necessary adapters you get much better sound.
The above applies to Little Dot MKIII - I don't have experience with MKII but others may be able to tell you if it works well in the MKII.
GE invented the gold grid in the tubes but did not make it a selling point - don't know if those minute quantities of gold affect the sound.

 

[Moak]

Could it be that 6N6 (chinese) and 6N6P (russian) are the same tubes and that the 6N6P is no upgrade to the 6N6 ?

 

[Moak]

Ok, I answer myself: It looks like they are the same tubes (see screenshot). Maybe the quality of the Russian tubes is a little better...
Does anyone have other experiences?

 

[triod750]

I like the Philips E182CC in adapter as a better replacement to 6N6P. Or the 5687 which can be used in that same adapter. For input tubes both 6J5 and 6C5 work very well, also in adapters. There the metal versions are very good value for money. I have used these in my Little Dot MKIVSE with splendid result.

 

[Cognomen]

Thank you for the reply! Do you personally think, that a pair of RCA 6EM7 could be a good experiment for €50 ? Right now I'm using PSVANE 6SN7 and I'm really curious, but €50 is a lot, still could be a pretty nice experiment - I'd like to know your personal opinion though.

It's a US television tube that's inexpensive in the US but perhaps not so abundant in Europe. If one looks around online, one can probably buy cosmetic pairs of 6EA7 or 6EM7 or 6GL7 for 10 to 17 pounds here including shipping. I don't know about vendors willingness here to ship to you. After I took out the Gamma-Tron 6EA7 (perhaps made by Heintz-Kaufman US??? but not ...mann Germany), I installed Westinghouse 6SN7GTB tall bottle halo getters. The Westi may have better bass but not quite as good treble but it's splitting hairs for me and my opinion might change with different music. If wanted I can post a list of dissimilar triodes that draw between .5Ah and 1.05Ah, perhaps some are better priced but there's the likelihood of needing adapters. There may be European species that were for European tv's and some might be on my list. At this time I'm not sure whether the average low to medium cost pair of 6SN7s or $12 to maximum $25 per pair 6EA7/6EM7/6GL7s sound the best to me, but the 6EA7/6EM7/6GL7 are much less expensive. So far I haven't joined the bandwagon of the highest-priced 6SN7's, not sure about the hype and whether or not it's worth it for an amp that wasn't explicitly designed to make 6SN7 sound as good as possible. I lucked out and got some used 6EM7 singles and a couple dozen non-hyped 6SN7 singles cheap and occasionally find and buy a cosmetic match on eBay. I've read elsewhere, using different equipment, that some people prefer the dissimilar double triode 6DR7, which requires adapters, to the 6EM7. The 6DR7 and 6EA7 have similar amplification for each unit. I suppose 6DR7's would work well but it would be an experiment. Some ultra-snazzy Leben amps use 6CS7 dissimilar triodes, adapters needed for us. The 6CS7 dissimilar triodes are rather close when it comes to amplification factor. They seem close to a 6SN7 in just that regard.