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Old 11th February 2009, 01:33 PM   #1
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Default Is it worth using anything other than DHTs for preamps?

I'm posting this knowing that it's provocative and will get a lot of disagreement, but after yet another preamp build I can't avoid this conclusion. So I'm just being honest here, for better or worse!

I've lost track of all the preamps I've built, but some serious comparative listening with fellow builders over several years seemed to repeatedly show that you got good sound out of the following valves: E80CC, ECC40, 6SN7 and all loctal variations, 6J5 and many variants particularly the 7193/2C22, 6N1P, 6N30 and 12B4. No doubt you can add a few but you get the idea - these come up regularly in designs.

Then 2 years ago I started building preamps with DHTs. The best used 26, 01A, 10Y and 1J6G. The first I tried was the 26 and my jaw just dropped about 150 feet. ALL of these were better than ALL the IDHTs I tried. I did repeated comparative tests and got the same results again and again. Topologies varied - I tried teflon cap output, transformer outputs of several types - about four or five different Lundahls and the Hammond 124b nickel. Choke loading, active anode loads, resistor loading, unbypassed cathodes, cathodes bypassed with polypropylene caps. CCSs of several types.

Doubting my sanity in the face of a flood of Aikidos and 12b4 preamps I built two identical balanced preamps. One used 1J6G into Hammond 124b, CCS under. The other used ECC40. I like this valve and use it in the input of my amp, so after the preamp the signal was going through a ECC40 anyway.

No contest - the 1J6G blew away the ECC40. And in exactly the same way DHTs habitually do - timbre, timbre, timbre. The instrumental timbres were rich, realistic, dynamic, vivid. With the ECC40 they were relatively flat. Detail was similar. After the 1J6G it was painful to go back to the ECC40 - this pre goes back on the bench and will be fitted with DHTs.

Clearly the preamp stage is critical - it establishes the sound that then gets amplified through the chain. Lose something and it's lost.

All my experience over 2 years has shown me that I just can't get that vivid, alive, delicate sound with IDHTs, whatever they offer. I'm a professional musician - I've played all my life in orchestras, small groups, theatres, clubs etc. I know what real instruments sound like, and I get this with DHTs.

I rest my case. I just don't know what else to say. Over to you guys.

andy evans
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Old 11th February 2009, 03:59 PM   #2
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Hi Andy,

Quote:
Is it worth using anything other than DHTs for preamps?
I think it just depends on the objective. F.e, I am an avowing cheapskater - well, mostly. In this regard my objective is to get decent sound from "cheap TV tubes", standard caps, just well engineered circuits, and so on etc, pp.

So far, nobody laught about my stuff when presenting/demonstrating it at audio fairs or meetings like ETF, so there seems not to be much wrong with my personal idea, objective and approach to tube DIY.

Granted, multi-kilo-Euro DHT and fancy iron stuff often enough will beat my stuff soundwise, but often enough I cannot resist a grin about what can be done using tubes for a few cents and two-digit Euro OPTs. But not without quite some research and effort to get there. Well, just my idea of a satisfying hobby - and my idea of "sportsmanship" in tube DIY, so to say.

Again, it just depends on the (personal) objectives. And even within the "same" hobby, there are different views, opinions, even schools.

Quote:
Is it worth using anything other than DHTs for preamps?
Definitely, I would say!

Regards,

Tom Schlangen
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Old 11th February 2009, 04:00 PM   #3
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Hi Andy

I've recently started experimenting with DHTs as preamp tubes.

I'm currently using a 46, feeding a 12B4A driving PX25 DRD power amp
The 46 blows any IDHT preamp I've ever built, into the weeds.

I have a pair of 26s to try, but I love the 46 preamp so much, I can't seem to get around to altering anything at the moment; too busy listening to the thing to tinker.

Steve
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Old 11th February 2009, 04:06 PM   #4
SY is offline SY  United States
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Have you tried comparing output to input?

There's a well-known designer for whom I have the greatest respect who believes (not unreasonably) that much of the attractive "vivid" quality of DHT comes from the mechanical resonance of the cathode. That's OK, but it is an addition and signal processing, so should be recognized as such. Which means that there is certainly a reason to use another technology- if you want the electronics to not add "niceness" to the sound but merely to amplify.
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Old 11th February 2009, 04:26 PM   #5
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A few points here:

1) Economy. Parts for a 1J6G preamp are pretty basic and all cheap. 1J6G is about a 5 dollar part, the Hammond 124b is about 20 dollars, but you can use cap output - Russian teflons were a dollar each last time I bought. Add the usual cases, resistors, caps and things and I don't think this is an issue.

2) Haven't tried a 46 in a preamp - it's a lovely tube! Thanks for the tip. Haven't tried 49 either. I have both.

3) Euphonics and "added realism". Well, I'm not an EE so comparative measurements may be a bit difficult. I build circuits to sound good, so my ears are the arbitor of what stays and goes.

But the thing is this - I'm a psychologist in my day job (play music at nights) so I'm pretty sceptical about comparative tests, and I do regularly have to weigh up evidence and determine what validity to give to one thing or another. So this isn't an airhead post about "don't know much about it but I know what I like" if you see what I mean.

So my line of reasoning is:
"If this is added realism and vividness, then by what fortuitous accident does it get closer to the timbre of acoustic instruments than IDHTs do?". I 'm not excluding this but it seems far fetched. It's not even as if it's like using Velvia for color photos to get extra vividness through colour saturation. Though it is a LOT like using Kodachrome 25 with Leica glass. It's exactly that crystalline fresh reproduction.

Do you see my difficulty with this line of reasoning? I'm not saying it's wrong - it's certainly interesting. Maybe there are other factors at work here?

andy
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Old 11th February 2009, 04:57 PM   #6
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Search original Soviet 6N30P-DR, 1970 - 1980.

Together with TAMURA A4714 it is a tube gives unique sounding (it is necessary to choose without a microphone effect). I had to compare with preamp on 10, 26, E81L, E55L, C3m, E280F, many other tubes (with matching transformers for internal resistance the tube).
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Old 11th February 2009, 05:01 PM   #7
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Hello there!

This is exactly the kind of reply that is useful - you say you compared the 6N30 with 10 and 26 and preferred the 6N30. A lot of people simply have never used DHTs, and it's the comparison that I'm interested in.

In what ways did you prefer the sound of the 6N30?

thanks!

andy
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Old 11th February 2009, 05:02 PM   #8
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Quote:
Though it is a LOT like using Kodachrome 25 with Leica glass.
I prefer Zeiss, but then again both hobbies are about doing what you like. You only need to satisfy your preferences, and budget. Remember the original Kodachrome advertising stated that Kodachrome delivers pleasing color rendition, not accurate color rendition. Worked well for Kodak.

I haven't finished a DHT preamp yet. In fact I didn't finish any amplifier last year. A little over a year ago I was experimenting with a line stage. I need a little gain and the ability to drive several amplifiers at once. This way I can leave them all hooked up and just turn on the one that I want to hear. I tried several tubes and circuits nearly settling on a 12B4. Then I tried an 01A with a mosfet follower. I must admit that it sounded nice and had just the right amount of gain. I do have some 1J6's and 46's maybe I'll try them.

Nothing got finished, and I was trying to sort out the phono stage when all progress stopped. My current phono stage uses an opamp.
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Old 11th February 2009, 05:08 PM   #9
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Andy,
I have to agree with you, nothing sounds better than a DHT. I'm also a musician, play cello and nothind can beat a DHT. I'm running VERY rare CX-340, CCS and parafeed OTPs. I tried all the others, 01, 26, 1H4, 1H5, 1J6, 10, 45, 801, 811, etc. The CX-340 really sing with the right PS and parts. For years I ran it with a Lambda Tube regulator and all kinds of LC networks, CCS etc. It really improved with the Salas HV shunt reg. (yes I know, sand is BAD), but now it really sings! Now it has the timbre, speed and depth that are so critical when you are a musician. I tried the Janus Tube shunt reg, but the Salas blows it away. It sould work great with the 1J6. I will not put sand or IDHTs in the signal path.
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Old 11th February 2009, 05:17 PM   #10
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Quote:
Originally posted by andyjevans


In what ways did you prefer the sound of the 6N30?


I suspect the "DR" makes a real difference.
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