[Acapella11]

Quote:

 
I'm trying to like the 2-7 setting -I really am- but I can't... I keep trying, it gives different results for each tubes, and it makes somewhat sense to "neutralize" grid 3 by cathode strapping, but it always turns out to sound worse than the two other setting -or just the basic unstrapped setting-

 

I have listened to Telefunken EH900S (E91H), EH90, Siemens EH90, EK90 and Amperex E91H and to be fair, these results do not superimpose with mine. In every case 2/7 is a viable option depending on favour. Specifically for the E91H tubes because they are very focused but they are also not exactly engaging. The 2/7-strap yields more treble bias and make them sound more interesting. For my Siemens EK90 (not authentic probably, with black bottom) the 2/7 sounds between 1/7 and unstrapped, which can sound very nice actually. I agree that unstrapped sounds very good. It also does on these Siemens.

 

Quote:

so I think I'll stop burning up my tubes sockets with that mod, at least until a few people encourage me to try again.

1-7 strap, though losing in favor for some tube type like the 6BE6, still sound great on some 6BY6 tubes imo; the strapped 5915 are very very good!

 

My purpose is not to encourage you. Do what you please as you are listening to your setup and I am listening to mine. If you don't like it on yours but I like it on mine, I wouldn't just switch and you wouldn't neither.

 

Btw original Siemens EK90 are kind of impossible to get, which makes it for most people impossible to follow this conversation. However, I encourage to buy the non-original ones also. Mine are good.

 

[gibosi]

Quote:

Btw original Siemens EK90 are kind of impossible to get, which makes it for most people impossible to follow this conversation. However, I encourage to buy the non-original ones also. Mine are good.

 
The picture for the following listing isn't all that good, but would you guess these Siemens EK90 are the same as yours? They appear to have saucer getters and sharp, pointed plated pins....
 
http://www.ebay.com/itm/1-Stuck-EK90-Siemens-Rohre-Neu-nos-/261193494785?pt=DE_TV_Video_Audio_Elektronenr%C3%83%C2%B6hren_Valves&hash=item3cd0587101

 

[Acapella11]

Quote:

Originally Posted by gibosi /img/forum/go_quote.gif
 
The picture for the following listing isn't all that good, but would you guess these Siemens EK90 are the same as yours? They appear to have saucer getters and sharp, pointed plated pins....
 
http://www.ebay.com/itm/1-Stuck-EK90-Siemens-Rohre-Neu-nos-/261193494785?pt=DE_TV_Video_Audio_Elektronenr%C3%83%C2%B6hren_Valves&hash=item3cd0587101

 
They are not because mine have a black bottom and no logo. Mine also came in a white box, which has on the following text:
5960-12-124-5244
Elektronenroehre
EK90
1EA
4/78
D/8502/82106
Siemens AG Muenchen 80
 
The fact that there is no German "ö" but "oe" instead points further to not one of the regular German productions.
 
The one one the picture looks "more original", if there is a gradient, than mine. Unfortunately it is only 1.

 

[gibosi]

Quote:

 
 

OK, it must be that these tubes sound different even though they are from the same manufacturer. I just received my Telefunken EH900S (gold pins as well) made in Ulm. They have written "Made in Germany" on them. And what no one said so far - these are "bass monsters". More detailed descriptions have to wait. They sound initially great, interesting house sound - yes. =D

 

The tubes slowly clear up. This needs a later update.

 

With respect to the 2/7-strap: Every system sounds different and likes also vary. If you don't like it, it's fine, you are not obliged to use it. At least for one tube (posted earlier) I can confirm it is definitely the best of the straps in my ears.

 

 
I just put my Telefunken EH900S in to burn, and yes, they are "bass monsters"!
 
Mine do not have gold pins, but otherwise, they look the same, "Made in Germany" printed on the glass with a diamond impressed between the pins. Moreover, the boxes are the same style as are AFB's.
 
A few words regarding my current thinking about these heptodes. With the pentodes and triodes we have trialed in the past, we simply put them in and listened. But with the heptodes, every tube is now essentially THREE tubes. (Well actually FOUR, but I think no one tests them in the EF92 setting anymore.)
 
In my experience trying to compare more than two, or at most three, tubes can be stressful to the point of being a rather painful ordeal. For example, my head hurts just thinking of MIKELAP comparing FIVE different triodes! But with heptodes, comparing only two tubes is actually more like comparing SIX tubes!
 
I write this to emphasize that it is going to take much more time than usual to sort through all these heptodes. I personally have 8 pairs of 6BE6, 5 pairs of 6BY6, and 4 pairs of 6CS6. Let's see..... 17 tubes times 3 different strappings.... 51 possibilities?  I find this to be simply overwhelming!!  And I suspect that I simply won't bother testing every possible strapping for every tube... 
 
In the end, we may not be able to reach a consensus regarding which strapping is best for each tube. But eventually, I think we will arrive at some consensus regarding which tubes are even worth the bother to explore multiple strappings. And I believe that alone will be a significant accomplishment.... 

 

[gibosi]

Quote:

They are not because mine have a black bottom and no logo. 
 
The one one the picture looks "more original", if there is a gradient, than mine. Unfortunately it is only 1.

 
I was hoping these were like yours as these are the only Siemens EK90 that I have been able to find. However, as much as I would like to know how they sound, I think I already have way too many heptodes, so I hope someone else will grab a pair of these and tell us how they sound.
 
Edit: Oh, you are right.... only one tube available...

 

[mordy]

Found another Siemens EK90 tube for sale. Could be that the seller has more than one. This one, as well as the other one above, are listed as "make offer" as well. Based on the pictures they look very similar.
 
And based on my experience with EBay, if you have patience, more "impossible to find tubes" will turn up for sale.
 
 
http://www.ebay.com/itm/EK-90-Siemens-Neu-aus-altem-Bestand-OVP-EK-90-Siemens-NOS-own-box-/230854435741?pt=DE_TV_Video_Audio_Elektronenr%C3%B6hren_Valves&hash=item35bfff239d
 

 

[mab1376]

The "Haltmens" sound great on the HD650 with the 7-1, since they're so dark it brightens them up wonderfully.

 

[gibosi]

Quote:

 
They are not because mine have a black bottom and no logo. Mine also came in a white box, which has on the following text:

 
Black bottom...  Maybe these (not including the logo/printing) look like yours? 
 
http://www.ebay.com/itm/6BE6-CV453-EK90-miniature-heptode-electron-tube-valve-/390260740216?hash=item5add5a5078

 

[zedmeco]

EK90 Röhre tubes (6BE6) Siemens. Hi, I have two pairs of these tubes that I bought some time ago but they do not seem to work with my little dot mk3, baically they hum! if anyone is interested in them I would be happy to trade them for any interesting ef95 tubes or something that will work on my machine. straight swop! let me know. z

 

[gibosi]

Quote:

EK90 Röhre tubes (6BE6) Siemens. Hi, I have two pairs of these tubes that I bought some time ago but they do not seem to work with my little dot mk3, baically they hum! if anyone is interested in them I would be happy to trade them for any interesting ef95 tubes or something that will work on my machine. straight swop! let me know. z

 
Would you take a picture of your tubes and post it here? Or perhaps you could point us to the vendor's listing? Not all Siemens EK90s are the same and it would be very helpful to know exactly what you have....

 

[MIKELAP]

Missed my order of Siemens Rohre EH90 yesterday but meanwhile the G.E. have about 12 hours on them and to be honest they started out similar to the 20 hours Hit Ray's but now the sound is muffled with more burnin will see what happens                                                                                                           .

 

[Audiofanboy]

OK, I have to confess I've been having a bit of a problem with my heptodes lately... They all sound good... And it makes testing and comparing them very difficult. Add the three -I'm still trying to figure out a practical way to use the fourth one- strapping settings and you've got a bit of a headache ahead of you... I feel like I'm 3 feet deep in "heptode cases" to test!
 
Anyway, for once, instead of doing long burn-in periods -both electrical and brain burn-in- for each tubes, I tried to kind of "blitz compare" a few of my newest ones (the ones for which I didn't have a solid brain impression and conclusion for like the 5915); normally this wouldn't work since the tubes aren't exactly burnt-in, but it kind of does since many of those latest tubes have either had the level of detail and "musical glory" I seek right from the get go, or basically have not; burn-in just mixing things up a little (bass tightening, etc...).
 
So, here are a few conclusions after this (and, again, take my -and others- comments about strapping settings with a grain of salt, since the gear you have seems to have a pretty heavy influence on which setting you'll eventually settle for; at least that's the only pattern I can discern for now regarding strapping heptodes) and also a few thoughts after browsing Google way too much at night:
 
- The IBM 1680 (1950, made by RCA for IBM, basically a 6BE6 with grid 3 like a 6BY6, so for all intents and purposes a computer rated RCA 6BY6 prototype) I got have a very special, lovely and addictive -foot tapping- sound that is unlike anything I've heard from a heptode yet. Think heptode detail with pentode musicality; yeah, that sounds nice, doesn't it? You can get these on ebay in the US for about $3 a tube if you negotiate; honestly, if you live in the US, get a pair! Anyway, I've only used these for 3 hours, and the bass was still all flabby, but they made for an extremely pleasant listen! They sound more relaxed and realistic unstrapped than 1-7 strapped -on my gear and to my ears- btw; they immediately showed quite a treble bias, like a slip of every frequency towards treble, when strapped.
 
- My two kind of Haltmens (CV453 labeled and 6BE6 labeled) sound very similar, and I believe the slight differences I'm hearing are your basic placebo effect and expectation bias; that and one pair being more burnt-in than the other. Both pairs sound quite glorious, with the top-tier level of detail we've come to expect from heptodes, musical realism and focus.
 
- Or so I thought, but testing some unburnt-in Telefunken EK90, I have to admit that the Haltmens have some serious competition. Basically, the Telefunken seem to be at least on the same level in terms of detail, focus and realism, but have harder hitting bass and even better treble; trade-off seems to be that they are just a bit more forward and maybe treble biased -unstrapped and unburnt-in- but not as forward as my Tele EH900S, which were too forward imho. I'll actually give these a proper burn-in now, but I could swear they render more detail than the Siemens... Anyone else have both to compare?
 
- Thoughts: from google tube literature, we'd assessed that grid 3 on 6BE6/EK90 has remote-cutoff curves (meaning that, despite being the actual "control grid" in the tube -unlike the oscillator grid 1 we've been using as a signal grid- we shouldn't use it in our triode-strapped preamp gain stage application as a signal grid), which is why I won't even bother 1-7 strapping it to grid 1 in those tubes anymore, since it doesn't make sense and doesn't sound the best. Basically, grid 1 and grid 3 on those tubes have different characteristics and are meant for different applications; we've ended up using a non-control sharp-cutoff grid for another application than it was intended for; we didn't have a choice and it works fine, so great, let's keep doing that.
 
- 6BY6 tubes, on the other hand, are switching tubes, with two actual control grids, both of which have sharp-cutoff characteristics (and similar gain/mu, to the best I understand and have read). Both grids can, logically, be used as signal grids -grid 3 would be the one that is actually meant to have a negative voltage bias, like grid 1 in pentodes or triodes though- and we've been using grid 1 for that because it's easier. Working out a way to neutralize grid 1 are using grid 3 as the signal grid, as I've suggested before, would make perfect sense, but may not be worth the extra trouble, since we can't prove that one of the two grids would work better, as they are quite similar. So using grid 1 is fine here too. Actually, any setting seems fine for 6BY6 tubes, both in theory and in practice.
 
- Enter 6CS6/EH90 tubes. These have traits from both the above tubes: they're meant for some kind of TV application and not as switching or logic tubes, but both grids are control grids with sharp-cutoff curves. But, unlike a 6BY6, the two grids have very different gain/mu, with grid 3 having about three times the mu of grid 1 (high mu isn't necessary for good function, but is a good thing as far as I'm concerned; my only issue with all our heptodes so far is that they have a very low mu, and therefore low volume). Basically, grid 3 has better characteristics as a "virtual triode" signal grid for a hi-fi preamp than grid 1 does. So, for 6CS6/EH90, neutralizing grid 1 (strap to cathode) and using grid 3 as the signal grid (tying it somehow to socket hole 1) would make more sense than just using grid 1. No, it's not necessary, but it just seems like a better way of using the tubes, that I'm very seriously trying to figure out an easy way to test, short of an adapter. Strapping grids 1 and 3 together could work fine (anyone try it actually?), but I have no idea how tying two grids with different gain characteristics will behave; I don't think it can't sound bad, I just don't know.
 
Anyway, sorry for long babble, but I still think we need to make sense of how and why our different types of heptodes behave the way they do, if we actually want to eventually understand what we're doing here (up to now, we've just slapped some tubes in our amps, just expecting them to work; we're reaching the limits of that system with heptodes imo; and as some have pointed out, we just can't test dozens of tubes with two or three different settings every time...).

 

[Acapella11]

Hi Gibosi and everyone else of course,
 
OK, I have made it to use my camera, finally. Here comes a little picture galore to update you guys with the new tubes I have in my inventory.
 
Siemens EK90 (6BE6): black bottom, no logo, saucer getter, 4 extended square holes at bottom and top front at back of tube, 02/78
These should be the of the same type as hypnos1 has. They were from here but are not listed anymore.

 
Siemens EH90 (6CS6): halo getter, 4 extended square holes at bottom and top front at back of tube, 06/78

 
Telefunken EH900S (6BY6, special quality): gold pins, diamond logo, six extended rectangular holes, of which 4 top and bottom on front and back plus two additional ones almost front and back in the center, "Made in Germany" label, Ulm 24/01/66 or 76

 
Telefunken EH90 (6CS6): diamond logo, "Made in Germany" label, same holes as the EH900s above, Ulm 26/06/66 or 76

 
From these tubes, at the moment (considering burn etc.), I prefer the Siemens EK90 but obviously the general level is high. The Amperex E91H (2/7-strap) comes close (but) with a different signature.
 
I have saved the Russian 6A2P pictures and a surprise for later.

 

[gibosi]

Quote:

- The IBM 1680 (1950, made by RCA for IBM, basically a 6BE6 with grid 3 like a 6BY6, so for all intents and purposes a computer rated RCA 6BY6 prototype) I got have a very special, lovely and addictive -foot tapping- sound that is unlike anything I've heard from a heptode yet. Think heptode detail with pentode musicality; yeah, that sounds nice, doesn't it? You can get these on ebay in the US for about $3 a tube if you negotiate; honestly, if you live in the US, get a pair! Anyway, I've only used these for 3 hours, and the bass was still all flabby, but they made for an extremely pleasant listen! They sound more relaxed and realistic unstrapped than 1-7 strapped -on my gear and to my ears- btw; they immediately showed quite a treble bias, like a slip of every frequency towards treble, when strapped.

 
As these RCA-made (1950) IBM 1680 are an early 6BY6 prototype, it seemed very appropriate to compare them to the RCA 5915/6BY6 (1963) I have on hand. While I expected them to share the same RCA house sound, I was quite surprised to discover that these two tubes are virtually indistinguishable, at least to my ears on my gear. As cheap as these are, I agree with AFB, you need to get a pair of these! Even if you already have a pair of RCA 6BY6, you should still get a pair! You will have a little bit of tube history in your hands: a prototype of the RCA 6BY6... and they sound good!  
 

 
- Or so I thought, but testing some unburnt-in Telefunken EK90, I have to admit that the Haltmens have some serious competition. Basically, the Telefunken seem to be at least on the same level in terms of detail, focus and realism, but have harder hitting bass and even better treble; trade-off seems to be that they are just a bit more forward and maybe treble biased -unstrapped and unburnt-in- but not as forward as my Tele EH900S, which were too forward imho. I'll actually give these a proper burn-in now, but I could swear they render more detail than the Siemens... Anyone else have both to compare?

 
Yes, I have a pair of both of these tubes. (It seems I have a pair of almost everything.. lol)  I gave a cursory review of both of these tubes on page 105, along with the Brimar CV4012 and Philips/Amperex 6687/E91H. I haven't spent much time with the Telefunken EK90s since then, so I plugged them in this evening, and am listening to them as I write. At that time, I felt that they were a bit too forward for my taste, but it seems that over the course of the past 20 pages, my ears have come to appreciate a more forward and treble biased tonality. (Listening to 6AV6/EBC91 triodes probably had something to do with this! lol) Anyway, I like what I am hearing and plan to spend more time with them.

 

[bruce108]

On the Telefunken EK90s. At first, mine were not so much treble-forward as bass-light and overall a bit thin-sounding, if refined and musical (EF95). But after 40-50 hrs they became a dramatically different tube, excellent bass in quantity and quality and well-balanced through the FR. Here's the thing: they warm up more slowly than any of my other tubes, taking an hour or so to reach their optimum. Any technical reason for this?