Just sharing my 26 experience last night...

[arnoldc]

I am a lucky bastard

My friend asked me to pick a pair of 26 from this-



I was like a confused jackass Tung-sol, RCA, Silverline, National Union, Cunningham, Songbird... he only has six pairs globe 26 including this blue Arcturus...



So I exercised some delicadeza and settled for these, even though I was holding already a pair of 1930's globe Cunningham UX-326



ST bottle Arcturus with red labels

Heck he even gave me the preamp where to plug them tubes!

The preamp uses LED bias (with current feed) and current regulated filament supply. Silent!

Talk about Christmas in July

I was able to hear the blue Arcturus, which has the best sonics, followed by the globe UX-226 and Arcturus ST bottle, then by the Tung-sol ST bottle.

Wow, what a DHT experience!

[andyjevans]

Did you find the high treble slightly rolled off? That's been my only problem with the 26 - otherwise it has gorgeous mids.

[arnoldc]

@andyjevans, in the system we tested last night and in my system now, no.

in my system, the Arcturus ST has very good balance, while it's true that it has excellent mids (which the Arcturus blue globe betters) the highs and lows are amazing. The highs have plenty to offer, micro-details galore, without sounding tizzy, very smooth detail sound. The bass is very articulate and detailed, AND this tube has got speed and dynamics, both macro and micro... which I think the globes I heard (26, 226, 326) are noticeably slower and mellower.

[Gluca]

Is it transformer coupled to the output?

[Zen Mod]

Originally posted by arnoldc
I am a lucky bastard

.......................

they're ugly!

[andyjevans]

I have a 3 stage all DHT amp under construction for a friend, and we did some tube rolling in the driver stage (outputs are 2a3) . The 26 globes were particularly nice, better than the 26 ST and the 112A. Particularly noticeable on voice and piano. The globe 26 is a very fine tube if you like the warm sound - it is quite fat and euphonic, compared to say a 30. In fact, 30 works nice on the input to this amp to give some balance.

[arnoldc]

Originally posted by Gluca
Is it transformer coupled to the output?

No they're not. In fact, the preamp uses cheap Auricaps (because my friend is also the distributor here)

Originally posted by Zen Mod


they're ugly!

Very ugly indeed!

Originally posted by andyjevans
I have a 3 stage all DHT amp under construction for a friend, and we did some tube rolling in the driver stage (outputs are 2a3) . The 26 globes were particularly nice, better than the 26 ST and the 112A. Particularly noticeable on voice and piano. The globe 26 is a very fine tube if you like the warm sound - it is quite fat and euphonic, compared to say a 30. In fact, 30 works nice on the input to this amp to give some balance.

I want to make an all DHT amp too. With a preamp, I am hoping I will survive with just a single DHT input, and DHT power. Maybe a 10Y and 45.

Globe or ST is a matter of preference, and synergy with the rest of the gears.

[kevinkr]

I have both globe and st type 26 from the like of CECO, Sylvania, RCA/Cunningham and several others. These do duty in my transformer coupled 26 pre-amp. It's survived 7 yrs now with just an ongoing series of improvements, and it is still my reference.

I think I like the CECO globes the best overall for casual listening, warmest presentation, clean extended highs and good bass. The current tubes are nos/nib Sylvanias and I think these are the best overall compromise.

My transformers (UTC HA-113) have permalloy cores and excellent high frequency extension. The problem with choke and capacitor coupled pre-amps using this tube is the fairly high RP (>8K) means that low capacitance cables are a must along with an amplifier input stage with modest amounts of miller capacitance.

The one mistake I made was to include the power supply on the chassis, this results in unavoidable hum pickup in the transformers. I have got it down to quite a low level, but considering that all of my power amplifiers have noise floors that are lower still it is the dominant noise source.

12's, 26's, 27's (idht) and 30's are all quite prone to electrostatic pick up so I made little, and rather ugly copper foil shields to go around them, grounded to the chassis - depending on potentials on adjoining component chassis (and me) this can result in a reduction of hum and buzz of about 10dB or so. (Makes a BIG difference.)

[arnoldc]

Hi Kevin, honestly I was surprised how my friend achieved no noise in his preamp. I remember him enjoying his prototype even with hum. We used to joke around and say the hum is the soundstage He was also suffering from microphinics and had to wrap his tubes with aluminum foil. He was using AC then, and was really stubborn in sticking to AC even though I've been trying to convince him to go current regulation (DC).

Then he came up with these (he made 6 of these, the black one)


By arnoldc, shot with K750i at 2007-07-10

Filament supply is now current regulated with LT1085.

I was stumped! There's no noise exhibited like before, in fact it was so silent, no microphonics too, even if we tube rolled different brands. Maybe he got lucky, and so do we!

ps.

re: Reference. I have to admit that my 407A and 12B4 pre might be gathering dust soon...

[Audio_idiot]

Hi Arnoldc,
Could you share the filament circuit?

Thousand Thanks