I learn something new every day.  I'll pull the tubes and take a look one of these days.

LR wrote:
"Sorry if I stepped on your d**k there and got you all bent out of shape"!

No need for sorry. I had that coming ~ touche'.

Very interesting info and appreciated.

The bias window is enjoyable Arch. Thank goodness, they sound nothing like KT66's or my KT88's. Interesting though, the innards might be KT88 stuffed in the smaller envelope. Cool, if so. .....all about the sound and they are special in the ZMA. IMO.

I look forward to hearing the 7581A's with my ZMA 25th. Also, Archie, was it you whom mentioned with your 25th, KT88's are running the power trannies cooler too? Subjectively, to hand touch. I don't believe you said you measured the temp. If bypass is bringing 88's more in congruence .....all for that!
J of A, have you noticed this? I would like to not be reticent about the KT88's and really enjoy them. However, if I never put KT88's in my ZMA again. I can be happy with the other three quads I roll and will find a fourth quad I bet.

Hi Arch, Timeline on the Rach' bypassed would be next Sept/Oct for order. Right now the ZMA 25th'd and its enjoyment. ZBIT in February too, coming.
Plus, Steve's Power Conditioner 10 Amp.

Good news on the 7581A's running cooler. Should bode well when I get the 88's in. Yes, the high bias of the A's like a 88 could be 88 in there. The 88's like the 66's though, stay in a tight margin bias, as where the 7581A's have a beautiful swing Bias I love to utilize.
Even if the 88's don't run cooler trannies... still will use for 4 to 6 hour sessions. All day on my other quads of course.

LR, look forward to reading.

I'm suffering. My ZMA has been gone 8 days. I usually get a great Saturday morning and Sunday session in. Well, you guys suffered 3 to 4 weeks...so must I.

Hey Guys,
Sorry for the late reply..  been one of those weeks.

Yes, based on my random observations using my IR thermometer, I do believe my trannies are in the ballpark of 5 degrees F cooler after power supply mods.

Still have my Phillips ECG N.O.S. tubes in play and digging them tremendously. Even found a single for sale on Ebay to replace the one tube gone bad in one of the quads I purchased.  So, now I have a full backup set again.

LR, I can’t speak to the GE’s but this Phillips set of 7027A’s are my favorite tubes I have rolled thus far. I have not tried the 7581A’s though, to compare.  It seems there may be some similarities in SQ between the 7027As and 7581As based on Stones and Archie’s observations. The 1 and 6 pins of the 7581A’s and 7027A’s are unused, but unlike the 7581A’s, those pins on the 7027A’s are tied to the screen and control grids - therefore acting as heat sinks for improved heat dissipation.

How about some old Brimar KT8C tubes for the ZMA?

I got 12, randomly grabbed 4 and put them in the Mystery amp, and they were within 5% of each other!

Archie,

These tubes LR pictured look like variations on British KT66 and Brimar 807s, Brimar 807s looking like some Russian 807s. When you read up on them, this makes some sense. Here is one explanation of the KT8C http://www.r-type.org/exhib/aab0080.htm

Yes, what Will posted.  These set is supposedly the very last of the KT8C done to Milspec for the British Navy. The note that the seller found in the box of them said they are direct replacement for the Ceramic versions and to bias like KT66. They are ruggedized with ceramic standoffs in the structure and (obviously) the classic curvy "coke bottle" shape vs the larger KT66 shape. Milspec typically requires smaller, ruggedized versions of our audiophile tubes that bias up lower and are pre-matched in batches so once the equipment is biased, the radio tech can just swap out tubes quickly and get back to work.

I'm typically really skeptical of tubes that are "milspec" unless they come in large batches and are re-matched. So I was very pleasantly surprised when I grabbed four from the 12 I picked up and they were so closely matched I hardly had to tweak the ZMA. Usually I'm balancing each pair (on the ZMA) for 2-3 minutes as they warm up and tweaking the overall bias. With these, they warmed right up, settled, and were all within a half-space of each other on the gauges. I sat there gawking for a minute waiting for something to change, then laughed and went to listening.

I don't have a ZROCK, I tend to be a purest and go as direct as possible, so I'm XLR out of my DirectStream directly into the ZMA XLR. The DAC is at 100% and I use the attenuation on the ZMA which is typically at 85% all the time, though with these tubes I lowered it a couple times during my listening session! LOL

I do have some Milspec CV124 which are the earlier versions of these tubes that are much more like the 807 tube. These KT8C sound similar, but BIGGER. I'm listening to the CV124 as I type this in fact.

Later this week I'll have different adapters in hand, and I'll be trying out some 6BG6GA, some of which are supposed to have the same guts as the 7581A that Jeff likes.

Speaking of, here is a tip for those of you looking to try out the Phillips ECG but can't find nor afford the 7581A - look closely as these.

https://www.ebay.com/itm/Lot-of-Eight-Heavy-Duty-JAN-6L6WGB-Tubes-By-Philips-USA...

These are the Phillips ECG 7581A guts stuffed into a smaller "ruggedized" envelope and relabeled as 6L6WGB for military use. I was told by some old timers that they might not get the full 35watts of dissipation due to smaller envelope, but they are basically the same tube as the 7581A. The link posted above is a rare find someone should jump on!

The tubes burning currently are GE Blackplate 6BG6GA on 6L6 adapters.

This was like finding a nice smooth set of $250 GE Blackplates. Although this quad is poorly matched. I have 8 more to go through and might need to mix and match them for better balance. If the ZMA didn't have the bias balance and gauges, these would be difficult to use. But hey, GE blackplates for the cost of a nice dinner, cool!

NORM! Help!

Talk me out of some Mazda's & Amperex by noon 12/20. Brent's shuttin' down till the 14th of the new year!
http://www.audiotubes.com/

No doubt, I'm guilty, I did start you down this rabbit hole, didn't I?!

I'm going to hold off for now. I need to figure my budget after the new year. I have a couple Decware products on the build sheet, I need to factor in. However, I think I'm going to grab a matched pair of 6N5P's from Steve next month........... .

You too Norm, have a great Holiday!

If I did not buy/tweak with another thing.....I'm very happy with my Decware/Kimber Select/Acoustic Zen Adagio/System of bliss! The glass is more than half full.

7581A's are wonderful. In Ron's honor/tribute tonight, I have my Gold Lion cryogenic KT88's in. Absolutely magnificent with the ZMA mod's. Subjectively running cooler~no worries.

Shout out to Will. Thanks for getting me off the Pangea once again, from the wall to my P3. My Kimber PK 10 Palladian from wall to P3 is spot on with no thickness in the low end with my ZMA mod's topping off the cadence speed with dead nuts PRaT. I do not regen my ZMA, it runs off the HC outlet of my P3 with an XLO Pro Series Hubbell to ZMA. I do regen my Transport and ZDSD to perfection.

To top things off, I tried to dethrone my KS6063 again. Well, once again it didn't happen. Other Speaker cables have smear that the 6063 eliminates by design. .....nough said.

Actually that last pic is after Mods. I guess Steve didn't go over it with the paintbrush duster, and I haven't in a while. With all the projects/construction going on, this place is always dusty (shrug).

Still haven't settled on tubes yet - currently using KT8 output with some mix of input. the KT8 are the real stars.

Joe,
The tubes that Steve provides are generally new production tubes or plentiful tubes that have not been out of production too long, tubes he can obtain and resupply, and tubes that owners can find easily and for the most part cheaply. (In more recent models such as the ZROCK2 and the 25th Anniversary Zen Amp Steve has provided carefully selected new old stock input tubes that really work well in the units, a bit of an anomaly or a new trend with Decware).

The truth is that the Decware amplifier topologies are so well thought out and laid out and implemented with such quality wire and parts that the nature of a tube is truly revealed, and as a result these amps can be tailored to suit one's taste or room or source material by tube-rolling. It's certainly not neccessary but it can certainly be educational and fun and lead to some fantastic sound. Some of us who have really been into our Decware components for years have gravitated towards tube-rolling and a few have insisted on not tube-rolling.

It's a testament to the quality of these amps that many tube-roll and discover the many possible sounds these machines can usher into our listening worlds.

I'm going to try the Pucks Norm, thanks. My last experience with the 28lb each Vibrapods x 3 under each speaker worked very well.

I played around with polarity with my speaker's the last couple of days. I swear when in the mood for some Rock; it's better or just different moving the driver's in reverse excursion.

Now, back to normal polarity and enjoying my NOS Tungsram 6922 input tubes today with my Gold Lion Cryo KT88's. THE NOS Telefunken's for inverter's. Yes, the Mod's are excellent and I'm running 3 out of 4 mod's/sans Nich'es.

I am interested in what folks are using as preferred tube compliments for the 25th Anniversary modified Zen Mystery Amps. I realize there are only a few modified units out there right now, with many still "burning in".

I will be sending in for the "full monty" modification once Steve gets the new Nichicon capacitors and wanted to stock up on some additional tube sets during the wait.

So what's your favorite combination of:

Output (Power) Tubes -
Phase Inverter Tubes -
Input Tubes -
Voltage Regulator Tubes -

Thanks in advance for joining in the conversation. I currently use 6N5P triple mica inverter & input tubes, Sylvania JAN OA3 voltage regulator tubes. On the output power tube front, using New Sensor Gold Lion KT66 and more recently enjoying Tung-sol 7581A tubes. Wondering about picking up a quad of Gold Lion KT88's to take for a spin.

HK

I put my 6P3S-Es back in and I have to say, they really are my favorite.  I also just bought a new quad from an ebay seller.  I don't have them yet but they were a real bargain.  Here's the link if anyone want to try these tubes and not spend much money - or get a backup quad(s).

https://www.ebay.com/itm/MATCHED-QUAD-6P3S-E-6-3-E-5881-6L6GC-TUBE-ROHRE-VALVE-R...

I learned to like those too. Sold my Torii Mk III this last week so I have a few sets of these that I'll probably post for sale soon as I no longer have an amp using the big bottles (I've fallen HARD again for the sweet petite tubes the Zen amps use!)

Thanks Norm. Interesting that the PS Audio P15 and power cord made such a beneficial contribution. I directly plug a top of the line Furutech PC (ZenWave Audio) into a Furutech GTX receptacle at this point. Happy listening to your system.

HK

Hey guys, I finally put in my 7027a’s into my 25 Anniversary ZMA biased at 60ma and they are now my favorite tube. The dynamic range and clarity seems to be tad greater than the 7581’s.

https://www.vivatubes.com/new-current-matched-quad-4-jj-electronic-7027a-7027-va...

Norm

Looks like a quad of 7027a's are in my future😊. Tung-sol or JJ's? I recall the JJ's seem to have quality/reliablilty issues. I think TAD also makes a heavy duty 7027a tube.

HK

Quote:


The 7027A's have, and continue to reign supreme in my system.  Mine are the NOS Jan Phillips.  Pricey, but worth every penny.  Can't speak to the other new production iterations as I have not had them in my system but it seems they are carrying the torch quite well!

Ordered: 7027A's Tung-Sol.

I'm sticking with the T-Sol family with these = hardy.  JJ's scare me/only have read horror stories about them and some little positives.

Yes, that was Norm. I've been dragging my feet about them for some time.
FedEx ground.....I should have them by Thursday or Friday and put a good seasoning start on them.

Have T-Sol 7581A's in with Tungsram inputs. I love these inputs because they are the 180 of my Mullard's and Ediswan's. When I want that...I got it. Sweet and extended they are. The price of these went up too since I got mine. So it is....half dozen of one and 6 of the other.
https://www.upscaleaudio.com/collections/preamp-tubes/products/tungsram-6922?var...