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10Y, 26, 27 and 45: relative microphonics

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I used all in preamp.
What i meant that i tried the power tubes in preamp segment and i find them not at all microphonic
SOrry was a rush response

My 26 and 27 are both balloon. UX226 and UX227. THe 227 i have is mesh.

Before this technique i could talk to my 26 and ith will respond thru the speakers. Also what happens the sound has a rush and echo feeling due to the mechanical feedback applied to the 26 as the sound is hitting the glass like a microphone.
Don't worry about 45 or 10y this are not that hard to get right

Cheers
nIcholas
 
Rick
Apologies if i confuse you
26,45,10y are dht

27,37,57,76 are old skool dht

the rest 9 pins and 7 pins

If possible avoid the 9 and 7 pins
Go for either 26 or 27. 45 and 10y not worth the effort. But you gain bragging right. 10y get the thrioated fillament like vt25 or 801a. this has very sparkling highs but no enough bass energy and mids. vt25a like western e's ceramic base is good balance but can't come close to the 26.
26 is a pain in the **** to make it work. 27 is not to far away in sound but easy to work with. Not popular as the voltage is 2.5volts. It sounds better than 37,57 or 76 because the fillament current is 1.8a. 26 sounds better than 01a because fillament current is bigger. Moral of the story is to go for high fillament dht as they sound more fuller

Cheers
nIcholas
 
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I use the 26 in my dht based transformer coupled pre-amplifier design which you can find on my site. It has been through several iterations and has improved considerably. It is silent and microphony is quite tolerable now as well. My approach was to make the chassis heavy and rigid, the tubes are not isolated mechanically from it, however I think mechanically isolating the sockets on elastomeric bushings on a separate subchassis is an excellent idea.

The 26 is extremely microphonic as are the 12A and 01A - all of which I can recommend in pre-amplifier duty if you can deal with the microphonics, and noise pick up issues.

Although not pretty electrostatic shields around 26/01/12 type tubes helps a lot with stray fields. I used copper foil for mine.

I recommend you read my article if you are thinking about building any sort of DHT based pre-amplifier.

I also like the 27 IDHT triode as well. Have designed several circuits using this for others. Watch out for the cathode insulation issues in early ones. I have both mesh plate globes and solid plate st types, both sound quite good.
 
26 sounds better than 01a because fillament current is bigger. Moral of the story is to go for high fillament dht as they sound more fuller

I don`t agree here

1-I used both 26 (4 different brands) and 01a (3 different brands) in the same preamp with same system. And the best is the 01a by a good margin. The 26 is way too much focused on voice, you miss both extreme (but they are there)

the 01a is more detailled, have mores sparkle and doesn`t emphasis on voice.


2- most on the people and I will say that a 45 sound better than a 2a3 even if the heater current of a 45 is smaller that the one on the 2a3.
I`m not sure that the more heater current, better the tube.

It may work sometime. the 26 vs the 112A (same tube with different heater current). The 26 sound more open and dynamic.
 
I’ve just read Kevin’s excellent article “DIY a 26 DHT Preamp” http://www.kta-hifi.net/projects/pre_page/26DHTPre/26dht.html.
The attention to detail, discussion of options, numerous warnings etc etc (and similar comments made elsewhere) give me the very strong inclination to do this design.

I know an excellent local tube dealer who has no 26 tubes, but 10y tubes. Would much be involved in adapting Kevin’s design for a 26 or 01, to a 10Y?

I think the most relevant characteristics are:

Tube Filament Plate Resistance MU Bias Ip
26, 1.5 V @1.05 A, 8000 Ù, 8, - 9.0 V, 7 mA
01, 5.0 V @0.25 A, 8000 Ù, 8.5, -9.0 V, 3 mA
10Y, 7.5 V @1.25 A, 5000-6000 Ù, 8, ?, 18 ma

Gain aside, how close are 26 and 10Y sonically?


Has anyone had the same experience as Nicholas:

“10y . . Very sparkling highs but not enough bass energy and mids”

Thanks
 
Gain aside, how close are 26 and 10Y sonically?

I used 112A, 26, 01a, 10Y and 801A in my dht preamp (as weel as other iht but they were not as good)

the 112 sound a little closed compared to the 26. You don' t have hum issue but overall sound is not that great

26 is a good performer but miss a little spark. I don' t like overall character, too much emphasis on voice.

10Y, very good performer. Big sparkle and way cleaner sound. The only thing is that the bass seem to miss. The preamp measureed well above 26 spec but we miss a little something on bass. (F3 was 16Hz from memory)

801a (most expensive), nearly as good as the 10Y (same tube with bigger plate dissipation) but just a little less clean.

The best result I had with 10Y/801a were with a small EQ (between input and the grid) that boost the bass area by about 1.6Db.

01a, very good, a solid bass, somewhat less clean as the 10Y but better bass. Sparkle is good, better than the 112A or the 26

It' s hard to choose between 01a and 10Y so I made a switch in my preamp to use both and switch in less than 30seconds.

But I can say that 80% of the time, the 01a is playing
I keep 10Y for classic guitar, violin concerto or opera where no real bass is involved



Sadly, I couldn' t try 71A, 45 or even 2a3 in preamp position for direct comparaison since I' m running out of gain:(


Regards
 
Kevin

The primary aim of your 26 DHT Preamp was to accurately assess the virtues of direct heated triodes in small signal applications, and you were very happy with the results.

On reflection it seems somewhat more complicated than it needs to be (eg 30 parts). Also therefore more expensive to acquire all the parts (I started looking last night).

Any comment on simply using a cathode resistor and bypass capacitor? And to help minimise hum, a TentLabs DC Filament “Directly Heated Tubes Supply” www.triodedick.com/tentlabs/Triode Dick heater UK.pdf

Cheers
 
Just a tip if you're building a DHT pre; don't do as I did and mount spring switches and rotary switches or other switch-based components on the chassi of the DHT. I use 12A in my HF/pre-amplifier, a brother of the 26 but with battery friendly filaments, and they make incredible microphonics when you flick a spring switch mounted on the chassiplate where they are mounted.. I have to lirk them not to make Bubba Microphonic.

Unless you choose to use a potmeter without steps, I'd say keep the pre passive stage outside the DHT's chassi (that is, if you can drive the cables to the DHT passively - short cables or TVC.) or use for example more wood in the construction, to dampen it better.. Just remember you *will* hear any vibrations unless dampened.

And ofcourse the most important lesson in DHT: keep the filaments clean!!! (Either very well regulated with current reg and $$$ of black gates or simply a SLA battery with a dedicated charger, per tube)

I should add that ofcourse the flick vibration issue doesn't affect sound while listening and not flicking around on anything. And the boings and dongs do sound interresting in it's own way but in case you doubt, it is annoying. very. I'm not listening with very loud & deep bass but I would certainly expect it to be a mechanic feedback problem with DHTs in driver tasks. As indicated earlier in the thread by someone else, DHTs as output tubes are one thing, it is something quite else if the microphonics from the DHT are amplified n times. DHT microphonics can be minimized but not eliminated I think unless you have the DHT amplifier in a separate room perhaps...
 
hmm thought I should add that my chassis is all aluminum and very prone to vibrations (with the amp off, you can even hear the alu plate vibrate when flicking the switches). Dunno how it'll work in a better chassis and with weaker springs in the switches.. This is a 12A/71A integrated and my first DHT amp, so my DHT experience is limited.
 
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