If you don't need gain, why not use the 26 instead of the first tube in your amp? Gyrator is good, plate chokes are good for 1:1 gain with a good cap e.g. Russian teflon FT-2. If you really want a step-down transformer preamp, I'd use an 01A. But I don't see what you would gain by adding a stage.
Hi Hificat,
....my opinion is that all depends what is your source and what your load for this pre.For last 12 months I play with few Dht tubes like 26,71a,112a,01a and 45 triodes.I have both Ales gyrators and Lundahl LL1660 transformers and also Tango 20K:600 output transformers.For me the gyrator from Ale are superb in all areas and if you want more precise sound with more precise bass section and more faster sound the gyrators are way to go.With gyrator, you become more gain and also lower output impedance with tubes like 01a and 26 with have pretty high anode resistance.On other hand with transformer on output for me the sound is more natural and musical.Not so fast,not the best dynamic bass response but the all tube magic is there.The output impedance depends on tube used.With 71a and 112a you will become lower impedance output like with 26 or 01a.But it depends on load,if you have tube power amp than this is no problem.You must try both option if you have time and chance.I do that and I must thanks Ale Moglia,Andy Evans,Rod Colleman(which regulator I use) and Kevin Carter(Lundahl expert) for all help,and now I can for sure say that DHT sound in preamps is something uniq no Idht tube come even close to this sound and I have so many tubes in past in my system.I have now two pre amps one with Ale gyrator with 26 triode and 300b power amps and second with 71a and Tango trans and class D power amps from Anaview.So I have see that all depends on all components in the system.
....my opinion is that all depends what is your source and what your load for this pre.For last 12 months I play with few Dht tubes like 26,71a,112a,01a and 45 triodes.I have both Ales gyrators and Lundahl LL1660 transformers and also Tango 20K:600 output transformers.For me the gyrator from Ale are superb in all areas and if you want more precise sound with more precise bass section and more faster sound the gyrators are way to go.With gyrator, you become more gain and also lower output impedance with tubes like 01a and 26 with have pretty high anode resistance.On other hand with transformer on output for me the sound is more natural and musical.Not so fast,not the best dynamic bass response but the all tube magic is there.The output impedance depends on tube used.With 71a and 112a you will become lower impedance output like with 26 or 01a.But it depends on load,if you have tube power amp than this is no problem.You must try both option if you have time and chance.I do that and I must thanks Ale Moglia,Andy Evans,Rod Colleman(which regulator I use) and Kevin Carter(Lundahl expert) for all help,and now I can for sure say that DHT sound in preamps is something uniq no Idht tube come even close to this sound and I have so many tubes in past in my system.I have now two pre amps one with Ale gyrator with 26 triode and 300b power amps and second with 71a and Tango trans and class D power amps from Anaview.So I have see that all depends on all components in the system.
First tube on my power amp is 6sl7 with mu=70, and is part of slight nfb. My power amp have 110k input but I do really belive line stage improve SQ - with denser tone and better dynamics. I was trying simple cathode follower, gomes stage supertotem, cdda like with/without ccs and now want try DHT. Do not know why, but ccda sound better than simple cathode follower, but need to set-up exact operation point in triodes.
....there is no direct and correct answer.You must try like I say.It all depends on how you will complete the Dht pre.Which Bias option you choose,what psu.what output an so on.But in all configurations that I have try the Dht tubes have always sound better like some ecc8x tubes or 6snx tubes an other double triodes.
...yes I have few boards from Ale.Two pair completed by Ale and two pairs completed by me with some parts like Shinkoh,Amtrans,Audio note tantalum resistor,V cap teflon and so on.The best version of gyrator from Ale with almost all shinkoh resistor and amtrans resistor with V cap teflon on board,is for me till now the best CCS/gyrator that I have try.The parts have influence on the sound of course.But it depends how much you would spend on this.And on other hand the gyrator with exotic parts will always be cheaper than some good pair of transformers and the sound is truly superb.And the low output impedance is a good bonus.So with tubes that have high internal resistance I always use gyrator.
It is monster amp with chain of gain-tube - ltp tube with tube ccs - 8x PP el34. I will keep it: not to change first stage.
I have transistor amp too with nearly 100W.
After ill finish dht pre i will borrow friends dht amp with al1 tubes, which i really like in his system.
I do preffer big but never harsh or unnatural sound.
Cx112a with 5k being lower than 26 is still rather high output impadence?
I agree with Andy.Some 01a pre with Ale gyrator and filament bias is hard to beat.The 01a tube have unique sound which is superb,full of transparency and emotion.If you decide to go with 26 because you have at home this,than you can try the same configuration and maybe the Sic filament bias also which I preffer.Look by Ale(bartola) in internet for some good schematics.
Also, don't rule out LC coupled output. This will give you the denser tone you are looking for. I slightly prefer this to transformer output, personally, but my amps present a higher impedance load to the preamp than yours.
(One can just use the primary of the output transformer for choke load. It's easy to swap between LC and transformer coupled.)
Ale's Hybrid Mu Followers are great. Ultra detailed with amazing frequency response.
LC and transformer output are a bit more, ummmm, "romantic" sounding.
Even RC coupling with both the 26 and 01A sounds really good, if one's amps are high enough impedance and low capacitance interconnects are used.
They all have something to recommend them.
If it is any help this is my experience (my ears, my room, my system) with the three regarding the 26:
-Gyrators: Super clean, ultra detailed, amazing frequency extension, very close, intimate connection with the performance. More gain.
-LC coupled: Excellent tone (denser than with gyrators), very smooth response, very detailed in a very naturally flowing way.
-Transformer coupled (lundahl ll2745): Very natural musical flow, smooth and extended treble, but a bit dry in the bass and overall lacks some sense of closeness and detail in comparison. Lower gain. Still highly enjoyable, however.
-RC coupled is very much like LC coupled, but can be slightly more rolled off in the treble depending on what you have the preamp connected to down stream.
As audioradio says, try them out in your system. Not only for system synergy, but it depends a lot on what you are hoping to achieve. (We all hear a little differently, have slightly different aesthetic desires, etc.)
Just build your preamp so it is easy to work on.
(One can just use the primary of the output transformer for choke load. It's easy to swap between LC and transformer coupled.)
Ale's Hybrid Mu Followers are great. Ultra detailed with amazing frequency response.
LC and transformer output are a bit more, ummmm, "romantic" sounding.
Even RC coupling with both the 26 and 01A sounds really good, if one's amps are high enough impedance and low capacitance interconnects are used.
They all have something to recommend them.
If it is any help this is my experience (my ears, my room, my system) with the three regarding the 26:
-Gyrators: Super clean, ultra detailed, amazing frequency extension, very close, intimate connection with the performance. More gain.
-LC coupled: Excellent tone (denser than with gyrators), very smooth response, very detailed in a very naturally flowing way.
-Transformer coupled (lundahl ll2745): Very natural musical flow, smooth and extended treble, but a bit dry in the bass and overall lacks some sense of closeness and detail in comparison. Lower gain. Still highly enjoyable, however.
-RC coupled is very much like LC coupled, but can be slightly more rolled off in the treble depending on what you have the preamp connected to down stream.
As audioradio says, try them out in your system. Not only for system synergy, but it depends a lot on what you are hoping to achieve. (We all hear a little differently, have slightly different aesthetic desires, etc.)
Just build your preamp so it is easy to work on.
8mA gapped version can be special ordered. They are perfectly happy to do it.
The 10mA version is 130H according to the data sheet.
Gapped for 8mA the ll2745/1160 are roughly 180 henries according to Per Lundahl.
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Hi Hificat,
A DHT preamp with Ale's Hybrid Mu Followers on the anode will not sound like a solid state preamp. It will sound like something you have never heard before.
You will not be disappointed. They sound very natural, I think. Though, they are less "candle-lit" than the other options. More like switching a lamp on.
There are also a couple of options if you try his boards. You can take the output from the Source Out and use them as a Mu-follower, or you could take the output directly off the anode of the DHT and use the boards as a CCS with convenient on-board voltage adjustment. These two will sound slightly different.
Regards,
John