DHT preamps

[Steve M]

I think you are right about it being a simplistic view but good luck with the passion, that's what gets results.

 

 

I like the look of something like this

 

 

 

Well, there's my 'simplistic view' clearly demonstrated. Which preamplifier has more potential, the one above using the exotic DHT tubes and Tango trafos or the one below using smaller standard tubes ??

 

[Bronal]

The Tram is a DIY product.  To be honest it was brought to market too quickly.  A 'commercial' offering would no doubt have been subjected to more stringent UAT before release.  However the mods required are not expensive - Rod Coleman regulators cost me about $60 from memory.  I also had Decky do a bit of rewiring and tweaking of the power supply.

 

As far as it sounding cold is concerned, I can only surmise that this is in contrast to the normal gloopy or glamorous sound of many valve preamps.

 

I bought the Consonance Linear preamp that was advertised this week.  It uses 101Ds.  It will be interesting to hear how that sounds.

[Steve M]

A straight Tram2 is already a good sounding thing, from my experience with it.

 

Does the Consonance use the 101D as an output tube? The Chinese can be a bit trixie, in the Melody 1688 preamp the 101D is used as a driver tube ...not quite what we would want in an ideal situation. Consonance makes good products, btw.

 

 

Steve.

[Bronal]

I have a 1688 as well.  AFAIK, the 101D is used for 'current smoothing' (whatever that means).  IOW, it's some kind of regulator.  The input and driver valves are 6SN7s.

[Guest guru]

Well, there's my 'simplistic view' clearly demonstrated. Which preamplifier has more potential, the one above using the exotic DHT tubes and Tango trafos or the one below using smaller standard tubes ??

 

With one I can count about $4000 in parts visible and the other about $25 in parts visible so I'm unsure what kind of case you would be trying to present with those photos.

[Decky]

....so I'm unsure what kind of case you would be trying to present with those photos.

 

 

A dusty one?

[Steve M]

Hello Guru,

 

Not in disagreeance with you and I understand a good preamp is a good preamp if the circuit is good. Just sayin' that if you chose to use DHT tubes in a preamp, there's a world of exotic tube choices out there 300B, 2A3, 101D, PX4, type 25/26/45/50/71A etc. Mainstream manufacturers stick with the small signal tubes because that is what they are used to working with or that they are simply easier to build (to get right) or are cost effective.

 

Steve.

[Guest guru]

Hello Guru,

 

Not in disagreeance with you and I understand a good preamp is a good preamp if the circuit is good. Just sayin' that if you chose to use DHT tubes in a preamp, there's a world of exotic tube choices out there 300B, 2A3, 101D, PX4, type 25/26/45/50/71A etc. Mainstream manufacturers stick with the small signal tubes because that is what they are used to working with or that they are simply easier to build (to get right) or are cost effective.

 

Steve.

You better hope they never do or the price will go through the roof. I have 22 valves in the system I'm running at the moment, so there is enough sunshine for all to be happy. Cheers.

[thoglette]

o

I'll be receiving one of Mick Maloney's new DHT creations in the next week or so. Some who have heard it say it's sublime. I will report once in situ.

Cheers,

EK

 

You lucky b*****d!  Or patient, at any rate.

 

I'm trying to remember  where I ran into a discussion on DC heated DHTs using a gyrator based circuit to seperate rectification and regulation from the heaters themselves.    

 

Ooo - found it.  On Bartola's site

Edited November 30, 2013 by thoglette

[tuyen]

I think what Decky means is that it doesn't sound like a valve job.  It sounds like itself - I haven't heard another preamp that sounds like it.  I forgot to mention it is extremely fast.

 

PS: if you want to have a lend of mine, let me know.

Quite keen if it isn't too much trouble to get the unit safely to WA and back?

I have a 101d based preamp I can compare it to. Also a 112a/26 pre on the way as well. Fun fun. Let us know how the consonance is?

Cheers!

[tuyen]

There does not seem to be a plethora of DHT preamps available commercially that are even close to affordable. The Tram2 seems to be a popular affordable kit until you realize that to get it to perform you need to spend well over double of the price of the kit to get the heaters quiet. I saw a Melody unit sell on Ebay last week that used I think it was 6SN7's and a 101D. I looked at reviews for this unit that said it was dead quite. Then I saw the price tag when they were selling new....gulp nearly 4K.

Tuyen, do you have some links for current available units?

None that I know of that is new and less than 3-4k onwards. If you built a nice one yourself, I think could get it down to maybe 2-3k just for parts?

2nd hand used market on the other hand..

[tuyen]

We are dealing here with subjective perceptions of the sound so I have to be very careful. I mean: open, transparent, clear, without any perceived rolled-off "sweetness"  or "(un)natural timber" (whatever that means?). Whether it  is accurate and precise - most likely - never measured it, and that would be the only way to determine that quality. In addition it sound powerful and creates a beautiful 3D sound stage that exceeds the size of my room. Now I can see ZB preparing itself to say how that is the consequence of excessive 2nd order distortion and it is artificial and not real - but hey - what is "real " in this world.

 

Do you think that is air that you breathe now?

Nice! Yeah that's what I've noticed with the DHT based preamps I've heard so far too. Some bit tonally different from each other. But the overall huge 3d soundstage is present.

I haven't yet heard a 'standard' 8/9-pin tube pre do this yet, let alone any solid state preamp. Have you?

[tuyen]

Not to say that the 8/9-pin pre designs (or S)S are no good. I've often just found them not to sound as 'open', but maybe have a more 'focused' sound?

[Bronal]

Not to say that the 8/9-pin pre designs (or S)S are no good. I've often just found them not to sound as 'open', but maybe have a more 'focused' sound?

 

That would be my conclusion as well on the basis of my limited experience.  My 1688 is a beautiful preamp but a lot darker than the Tram  I can tell you one thing though - the Tram is wide open.  I'll PM you about getting it to you.

[Decky]

Alan if you have limited experience than mine is non-existent (or at least statistically insignificant) 

[Bronal]

Alan if you have limited experience than mine is non-existent (or at least statistically insignificant) 

 

Yes, but I don't have your analytical abilities...

[Sir Rab of Everest]

The Tram2 is very responsive to parts substitutions, so in general each sounds different. In stock form, they already sound very good, but upgrades take it to another level.

 

As it happens, some of us here in Melbourne had planned a three way Tram2 shootout last Saturday, but one of us got a tummy bug and we cancelled.

 

Two of the trams have EML 45s and the other has TJ Full Music 2A3 SE carbon plates. There are other component differences, but all 3 of us have the Rod Coleman regulator boards and various upgraded caps.

 

I have already done a quick comparison of the 2A3 tram vs my 45 Tram. Although mine was possibly better in some ways, the 2A3 tram let through more detail, which i found i missed when i went back to my tram.

There was not agreement as to which sounded better. I assume the difference was mainly due to the 45 vs 2A3 differences, but I am planning at some stage to do a swap in my own tram - sadly this is not a quick changeover, as it involves some soldering!

Edited December 2, 2013 by rab

[thoglette]

I have already done a quick comparison of the 2A3 tram vs my 45 Tram. Although mine was possibly better in some ways, the 2A3 tram let through more detail, which i found i missed when i went back to my tram.

 

45 should clean the 2A3's clock as widely reported - it's a much more linear device.   But as you say, that's presuming all other things are equal.  And there's a lot of other components (especially capacitors) in that circuit,

[ehtcom]

The Tram2 is very responsive to parts substitutions, so in general each sounds different. In stock form, they already sound very good, but upgrades take it to another level.

 

As it happens, some of us here in Melbourne had planned a three way Tram2 shootout last Saturday, but one of us got a tummy bug and we cancelled.

 

Two of the trams have EML 45s and the other has TJ Full Music 2A3 SE carbon plates. There are other component differences, but all 3 of us have the Rod Coleman regulator boards and various upgraded caps.

 

I have already done a quick comparison of the 2A3 tram vs my 45 Tram. Although mine was possibly better in some ways, the 2A3 tram let through more detail, which i found i missed when i went back to my tram.

There was not agreement as to which sounded better. I assume the difference was mainly due to the 45 vs 2A3 differences, but I am planning at some stage to do a swap in my own tram - sadly this is not a quick changeover, as it involves some soldering!

 

Whils the new production 45's (and 2A3's) are very nice, i still prefer the old stock RCA Radiotron globe 45's.

 

 

Cheers, Earle.

[Once was an audiophile]

Whils the new production 45's (and 2A3's) are very nice, i still prefer the old stock RCA Radiotron globe 45's.

 

 

Cheers, Earle.

Your just teasing people now earle 

 

[Lansche plasma guy]

Thsnkd for the interesting topic Tuyen! :-)

The Tram II is great stock.

The first outing of mine was a gathering at Duc's place perhaps 2 years ago now.

There were something like 20 hifi tragics there (a term of endearment).

When we put the Tram in the system our jaws collectively hit the floor. It was like a totally different system.

You know when somethings good. And a game changer. Suddenly a room full of sudiophiles get huge grins on theyre fsces. Everyone looks at each other nd starts talking to each other. Then like junkies everyone is asking what is it? And a million other wuestions whilst looking at the thing like an anorexic at a chocolate bar.

Wechanged from my ST 45 tubes to various globe 245s which was a big step up.

The pre is wonderful stock but is taken to altogether higher level once some serious mods are done.

My experience has been that the Emission labs globe solid plate 45s are the best for this unit. I thought they were much better thsn all of the next best 45 Globes including a variety of near NOS RCA Radiotrons.

The Coleman regulators do not come with a power supply which is almost the entire cost of thst particular mod (assuming you want a decent power supply for it of course).

Almost all the parts save the transformers, chassis and sockets have been replaced in mine.

The silver wire csme out. All the resistors came out. The caps almost all came out. A very large copper heat sink was fitted. Temperature controlled fans were aso fitted. Etc etc.

This Tram (most of the work has subsequently been done to Rabs pre also) sounds a great deal better than the stock unit.

Its an incredible pre with staggering dynamics, soundstaging and tone. Its the most direct sounding acrive pre ive heard but with much better weight, dynamics and push than the passives ive heard.

Its not perfect. Its problems are reliability and operating quirks.

Its failings if your not careful can be in the way of noise floor and or hum luckilly absent from mine.

They are very unreliable stock with the main issue being overheating. Mine has lots of vent holes drilled in it along with fans and a much larger heatsink of copper.

It has the most frustrsting volume control ever devised. It was put in becausg it sounds amazing allegedly and is shared by the Audio Research reference pre etc but its the slowest volume control on earth. Thst tennis elbow you may have had when you were fit before becoming an audiophile and spending sll those hours indoors will most likely definitely re-surface using this thing.

Whats with the LEDs??? Brighter than the sun but wthout the benefits.

The chassis is damned small for all us tweakers out there. Its already jam packed and once you start doing thr mods described very quickly run into some serious space issues.

Aside from the above annoyances its the first pre thats not made me dream of no pre. It seems to enhance all the systems ive heard it in.

I would love to hear the Coincident and others of its ilk. They may be better again??

The Tram ii and im assuming the other dht pre's certainly have that special something thst adds helps create magic for many systems making you forget your listening to reproduced music snd creating deeply satisfying experiences that nourish the soul.

LPG.

[Sir Rab of Everest]

It has the most frustrsting volume control ever devised. It was put in becausg it sounds amazing allegedly and is shared by the Audio Research reference pre etc but its the slowest volume control on earth. Thst tennis elbow you may have had when you were fit before becoming an audiophile and spending sll those hours indoors will most likely definitely re-surface using this thing.

Whats with the LEDs??? Brighter than the sun but wthout the benefits.

 

I never use my volume control directly: i didn't even put the knobs on! I just use my logitech universal remote.

 

.. and my blue LEDs are now nice and dim since the relevant resistors were changed! 

[tuyen]

No problemos Bryan

Well I have only briefly heard Steve's tram2 in stock form a while ago on my system. Sounded good, but it was bit too noisy. I think I still preferred the old silvaweld swc-1000r (we 417a tube) pre I had back then. As you mentioned, the volume controller was quite frustrating to use!

The CSLS is excellent pre as well. Works well in my system. Really quiet, dynamic, resolute and open. Biggest 3d soundstage I have been able to hear from my system. Has a very 'direct' type of presentation. Not to say it is faultless though. The cheap vvolume switching mechanism gives me the sads as well. Going to do some component changes to it to see what happens. Hehe

I also have a Tubelover 112a/type 26/ux-226/cx-326 DHT preamp that is on the way too. Has rod Coleman regs, duelunds, black gates, etc.  Interested to see how that goes.  Plan to use it on the JBL system.

Bronal mentioned earlier in this thread that theree is a possibility of sending me me his tram2 which I believe is slightly modded with coleman regs and EML45, so might be a little DHT pre gtg coming up in WA if members are interested. May have access to Tasso's very nicely tricked up mingda 300b DHT pre as well.

Edited December 2, 2013 by tuyen

[Red MacKay]

G'Day Guys,

 

 

I am new here to SNA, but some of you out there will know me...

 

I'll own up, I have a DHT pre!  It's diy using a 10Y and a 2.8:1 I/Ts made by Russell Spokes.  I tried a pair of Lundahl trannies that the guys on the LHF forums rave about, but they completely lacked the "magic" of Russell's big double C core trannies.  The design and inspiration for the pre, I stole loosely from a really early Andy Evans circuit over five years ago.  ...The wheels turn slowly here.

 

So how does it sound?  Awesome!  But I'm still working on it.  Coleman regs are fitted, a LCLC B+ supply using a Parmeko trannie, seperate rectifier trannie for the 5R4, Lundahl and Garnder chokes  and a Coleman designed heater supply using Panasonic FMs, stacked film caps etc. It's still a bit noisey and I have some work to do on that.  But then everything is noisey in my home, I think I have an issue with house wiring more than the pre!

 

I have had much pain getting it to sound right though.  Well that was up until I threw away all the audio boutique caps and installed a humble $4 NCC KMH from my junk box, into the B+.  Now I was finally in the ball park!  So forget your Mundorf Silver and oils, Obbligattos etc, they just did not work for me.  I also have a 40uF ASC oil paralleled to the KMH and a 0.22uF stolen from My Cary SET as a bypass on the 20uF Plessey first cap.

 

The other tipping point for me was just last week.  Bruce told me to load up with a few more uFs on the cathode bypass and so I did.  The 25v BG 1000uF was huge improvement over what I had till then and at last I had bass and lower mids, along with a beautiful clarity that has always been there, but now was shining through.  But then with Mohan in my ear, I finally capitulated on Friday and replaced the BGs with some paralleled up 16v SEPC OSCONS.

 

Hooley dooley!!!  The difference is astonishing.  My tired old HPDs have no right to sound as good as they do right now.  The speed, clarity, bass attack and utter natural beauty with which the music is presented, is just breath taking.

 

The only thing I am missing, is the holographic thing.  This pre does not image very well and never has.  Darn!  I simply do not know why. Being really critical, it is a touch sibilant too.  If anyone has any tips, please shoot them my way.

 

But even with its faults, this DHT is a thing of beauty to listen to.  I just can't listen to a 'normal' pre anymore, DHTs will spoil you and turn you into a snob.  It's totally true!

 

The build quality of my 10Y has not been compromised, but it's not pretty and sits on two chassis.  I will rebuild it into a nice 2 piece case later on.

 

So who else runs a DHT pre out there?  I have heard Bryan's Tram II and it is pretty good.

 

 

Cheers, Red.

[gamve]

Hey Red,

Good to hear your squeezing more out of the pre. No Imaging, who cares? Get the tone first, the rest will follow

Cheers

G