• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

One more 4P1L SE

Jump to Latest
#782
H.Michi said:
Well, I have built this amp on experimental for attaining maximum output within minimal clipping level under stable color of the plate surface.

BTW, the MJ magazine on April issue, Mr. Katsu Nagashima contributed an interesting article about 4P1L tube. He looked into the inside of the tube (one fabricated in Soviet era) and found that there are two getter rings at the top and lots of getter flashed. He assumed to be the top getter is from Barium oxidize getter (due to whitening), however the side getter might be from Magnesium　oxidize (stable native color).
Additionally he found the plate was supposedly coated with Zirconium.
He concluded this 4P1L was designed and made on non cost conscious basis but for ultimate reliability.
Click to expand...

Hi Hiro, interesting analysis.

I only hope that prices will not go sky high right now!😀

Cheers
 
#783
andyjevans said:
As for OPTs, I've been searching for the best choices. At present I'm using a LL1660/80mA which is pretty good but I'm open to other ideas. Options could include James 6123HS, Daburu DA-35X, Silk S-330F, Softone RW-20, Hashimoto H-20-3.5, Monolith Etude 1, Tamura F-7002. Basically 3k to 3.5k, 80mA gap, about 3 kilos weight and 20 watts to get decent bass - whatever you'd use for a 300b. The smaller 1.6 kilo 12 watts types probably also sound good but with lighter bass. I don't know the US transformer makers, I'm in Europe.
Click to expand...
Perhaps not the most appropriate place for this but I'm trying to make-up my mind between James 6123HS (currently 'on sale' for $285/pair shipped to Europe) and Softone RW-20 ($262/pair shipped) for a PSE 4P1L or 6e5p amp (or some other triode(d) tube requiring Za of 2.5-3K for 5-10W output).
Softone did come out well in ETF tests but it's actually a 1.5 kilo transformer so perhaps needs to be compared to the smaller ones from James and Silk rather than the 3.2 kilo 6123HS (their own test with 300B shows 7W at 30hz, 5W at 25hz, and 3W at 20hz while James 'scored' 5W at 20Hz even in the somewhat biased measurements done by Silk makers)
Has anyone had a chance to hear Softone RW-20 alongside some of the EI-core 20W transformers from Andy's list that are in the same price range?
 
#785
From what I can see LL1664 is some 30% more expensive (and that's not including shipping) and also the least versatile (single primary and single secondary). The question is whether it would sound 30% better than James and Softone.
 
#786
dovla said:
From what I can see LL1664 is some 30% more expensive (and that's not including shipping) and also the least versatile (single primary and single secondary). The question is whether it would sound 30% better than James and Softone.
Click to expand...

That versatility, in particular different primary loads, comes to a price: losses. In small power amp low loss is important in order to maximize the effective power you get. The Lundahl is without a doubt the best at low frequency, having quite good inductance, and this is usually overlooked in valve amps, attributing the lack of bass quality to the damping factor rather than distortion.
For me the Softone is quite limited having poor inductance. For the other things it looks good but to avoid high distortion I would use high pass filters upstream the circuit so that the output stage will not produce too much power and thus distortion below 40-50 Hz. The fact that your speakers might not be able to reproduce very low frequencies, say below 40Hz, is not relevant as you will get all the harmonics that represent the nasty stuff.
 
#788
LL1664/100ma with 17H then looks similar to Transcendar 3k/8 10W with 20H inductance, a pair of which cost the same as a single Lundahl so there's another contender at the same price (shipped) as the Softone.
Quite strange that in ETF shootout some of the transformers with the best scores overall didn't make it as far as the Softone (LL1664 AM was even 'knocked-out' in the first round)

European Triode Festival - ETF2009 Shootout
http://forums.melaudia.net/attachment.php?aid=1228

Now I'm even more undecided 🙁
 
Last edited:
#789
dovla said:
LL1664/100ma with 17H then looks similar to Transcendar 3k/8 10W with 20H inductance, a pair of which cost the same as a single Lundahl so there's another contender at the same price (shipped) as the Softone.
Click to expand...

There is price to pay for that as well and it is again power loss. 300R primary DC resistance is very high. The Lundahl achieves 17H/100mA with less than 150R. Nothing comes for free....
 
#791
If someone is interested, Transcendar 5k:8 (10W) SE transmission curve (EMU0404 + 700R):
 

Attachments

  • Transcendar 700R gen. (5Hz-100kHz)_web.jpg
    Transcendar 700R gen. (5Hz-100kHz)_web.jpg
    122.8 KB · Views: 850
#798
2SK170 etc are JFETs, and have low breakdown voltages, lower than the 52V negative supply, not to mention the swing from the cathode-follower. These would not be suitable.

You may be able to use a different MOS device, but please compare the threshold voltage Vgs(th) before substituting - L suffixed parts usually have low value for this, the turn-ON voltage threshold.
 
#799
I know that Michael Koster tried this before with a 6L6 and liked the sound of it. Has anyone tried this on 4P1L? It looks like 3W can be extract from the 4P1L in pentode mode with an interesting harmonic profile. It may prove to be difficult to balance in real life given DC coupling.

Just a quick simulation and idea to see what ideas may spark 🙂

Cheers
Ale
 

Attachments

  • 4P1L schade feedback SE .png
    4P1L schade feedback SE .png
    31.7 KB · Views: 568
  • 4P1L schade feedback THD.png
    4P1L schade feedback THD.png
    19.1 KB · Views: 550
You must log in or register to reply here.
Top Bottom