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Old 25th February 2010, 12:20 PM   #1
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Default JLTi EL34 and KT88 Amplifiers


from JLTi EL34 & KT88 Amps two notable quotes:

"The Plan:
To take a mass-produced OEM type Chinese made amplifier with decent basic performance and reasonable components such as good transformers with good bandwidth. The Chinese can now do that better than anybody else and they can turn these out at a cost we cannot compete. But the sonic performance is generally less than desirable compared to the very best. But we are going to change that.

So rather than compete, take advantage of it. But alas, few are able to do just that. But we are! Some of you may have heard of Vacuum State situated in Switzerland and headed by Allen Wright who used to live here in Sydney. For 33 years I have been a collaborator with Allen and also part of a loosely organised international team doing much leading edge research, much of which is then shared."

I think: The Plan sounds good

“How does one describe the sound?
In many ways it is similar to what might be described as a Single-Ended sound. If that is the kind of sound you are into, then this is the Push-Pull amplifier that will change your mind about P-P amps. It has none of the downsides usually associated with P-P, but far more dynamic and has much greater sonic impact (single-ended has asymmetrical rise time that blunts transients but regular P-P sound less pure and coarse sounding - but this is not the case here).
While only rated 20 Watts per channel, many have commented that it sounds far more powerful than that. When compared with the Audio Research D125, the owner of the AR was surprised to hear it was only 20 Watts as he had expected 60-70 Watts (the AR will soon be on sale on eBay). It is clear that in sound systems that lack genuine dynamics, listeners simply feel the need to turn up the volume to compensate for this lack. Is this is why we see 300 Watt amplifiers in cars and young drivers exposing themselves to hugely loud music?
But dynamics and loudness is not the same thing. Here we have an amplifier that uses technology that enables true dynamics and amazing impact at reasonable and realistic volume without the need to turn the volume up any further. For those limited to late evening low level listening, "this amp is a dream come true" (Mariusz Mugaj, Perth, WA). Only when you have heard this quality does it really become comprehensible. But in reality this ought not to surprise us as the sounds we hear in real life are just like that.
As we walk through the day we don't feel we need to turn up some imaginary volume control, do we? But when we get to a sound system we have this need to turn it up so far that we cannot hear someone right next to us speak? Yet when we go to a concert where acoustic instruments are played, and the sense of full emotional impact is there in abundance, and if our friend next to us starts to talk and he is clearly audible, we realise that the impact of what we hear is not entirely tied to the loudness we perceive. Yes, realistic volume and no more. The music will do the rest for us!
But we have not covered the majestic quality this amplifier has in portraying realistic images and full bodied sound and capturing the beautiful colours of real musical instruments. This is indeed a music lover's amplifier and not a "Hi-Fi" amplifier. The sheer "body" (or solidity of sound) it can produce will stun you, especially, but not uniquely, on voices, the sheer physical presence of Diana Krall (I'm less a Norah Jones fan, but will prove the same point) voice will say much more than any words here.
The top end is extraordinary and unravels much intricate details previously not heard. Most other amplifiers, regardless of cost and whether tube or solid-state, sounds positively coarse. Curiously, while revealing more details in the treble it is also much less bright sounding because it avoids the coarseness and instead replaces it with a remarkable smoothness, silkiness and exquisite air."

I think: (Was going down the path of an 845 SE)
The claims are bold
The price is modest . .

Has anyone here built and evaluated these, or would like to comment on Joe's mods?

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Old 25th February 2010, 12:36 PM   #2
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It is most entertaining to read his website. I think I got my money's worth just out of that. As far as the amplifier is concerned, I'd be hesitant to pay $875 (USD) markup on a $350 amp.

Last edited by Ty_Bower; 25th February 2010 at 12:38 PM.
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Old 25th February 2010, 12:53 PM   #3
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the proposition is that you paying for the R&D (and presumably parts) behind the mods.

(Also, who could build an EL34 or KT88 amp for only $350?)
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Old 25th February 2010, 01:01 PM   #4
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This suggests you are getting an amp worth much more than $350

JLTi EL34 in Hootout!

Mind you, is this the very same amp being old for $A 880/ 990?
And what does the price include, for a complete amp - are their any extras?
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Old 25th February 2010, 03:16 PM   #5
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too bad their amps are just so butt ugly
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Old 25th February 2010, 03:51 PM   #6
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These listening tests run surprisingly professionally:

1) Tests were blind
2) Volume levels (sound pressure to be precise) were calibrated with SPL meter.

Excellent !


Last edited by LinuksGuru; 25th February 2010 at 03:55 PM.
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Old 25th February 2010, 09:52 PM   #7
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SigloOne, I also like gear that looks good. Anyhow, looks are subjective . . to me its ok

The thread was seeking comments on the sound or technical features (thanks LinuksGuru)

To me his clams seem "oversold", but that the amp did win two shoot-outs against several well regarded amps

Re the technical features - I wish I could fully understand the "Super Linear Triode Mode" or the "Linearity Enhancement Module". Any comments on those?
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Old 26th February 2010, 12:02 AM   #8
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Originally Posted by otto88 View Post
SigloOne, I also like gear that looks good. Anyhow, looks are subjective . . to me its ok

The thread was seeking comments on the sound or technical features (thanks LinuksGuru)

To me his clams seem "oversold", but that the amp did win two shoot-outs against several well regarded amps

Re the technical features - I wish I could fully understand the "Super Linear Triode Mode" or the "Linearity Enhancement Module". Any comments on those?
Maybe I should chime in.

"Super Linear Triode Mode" has also been called "Virtual Triode Mode." I don't claim to be the originator but simply doing my own version. I was first made familiar with it by Bill Perkins (Pearl Audio) and exchanged emails - also used by Eddie Vaughan. Not always universally accepted as better or sometimes it works for the better, other times not liked.

The "Linearity Enhancement Module" came about with discussions with Menno Vanderveen (Menno van der Veen) and also of Plitron Transformers. We met up in 2006 and suggested to him an idea and it went from there. The idea is simple enough and part of the discussion "Modern tube amplifier design?" ( Modern tube amplifier designs?)

Basically the transformer's Permeability is related to its voltage across the Primary winding. Output transformers do not have constant linearity across the whole dynamic range. Indeed as the voltage collapses so does the Primary's inductance. Now I don't claim to be a transformer expert in the league of Menno, but my suggestion was to use the upper octave bandwidth and simply keep the transformer busy at all time. It comes down to picking the right frequency and the right level. It is apparent that the constant ticling of the Primary, that a step-down portion will appear across the secondary and that will go straight through the High-Pass Filter to the Tweeter (or the voice coil of a full-range). The maths showed that a tickling frequency of 10V p/p at least one octave above audio bandwidth and a typical transforer step-down of 20:1 or higher, that the Tweeter would be highly unlikely to have to dissipate more that 10mW and typically under 5mW.

What the LEM does in the larger scheme of things is making Virtual Triode Mode more constsistent. Whereas VTO was hit and miss, it has been found that VTO always, and that has been the experience so far, works when LEM does its magic. They are very much compatico entities. I do not suggest using the LEM unless VTO is already used. It sounds too smooth. Likewise VTO can be quite the opposite, but then the LEM adds the refinement and low level resolution to balance the VTO.

Back to VTO: The Anode/Primary Z interface forms a high pass filter, what the VTO does is keep that Z lower and a more constant Z under dynamic conditions. That HPF is dynamically modulated and is thus not a constant frequency. I have posted Menno lecture on this subject in the past and was downloadable for a week. I believe that VTO also pushes the output transformer's limitations, which are then heard. While the Anode/Primary Z is kept more constant, it does not stop the permeability drop (slide really). It looks like it opens the window more and we hear the lack of Permeability/Linearity more readily. Now what the LEM does becomes highly desirable.

BTW, one of the great advantages of SETs is the gap used in the output transformer gives you extra Permeability for free. Now we can get it back [I]and more[I] in Push-Pull amps. Nice.

Re value-for-money issues: These are the best value amplifiers I know of. Mostly word of mouth rather than the website (but then they do go to the website to read more) is the key to the success of these amps. As for R&D, that aspect as well as other related business activities, and I reckon that barely 25% of the time I actually hold a soldering iron in my hand. Perhaps that keeps things in perspective. Maybe to be more blunt: I gotta eat!

I don't think I've oversold anything!


The "Elsinore Project" DIY Speaker System " & DIY "Trans-Amp" - 40 Watt Transconductance Amp
Soon: High Frequency Bias in Tube OPT - "Don't take anything I say as an affirmation but as a question."

Last edited by Joe Rasmussen; 26th February 2010 at 12:07 AM.
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Old 26th February 2010, 07:21 AM   #9
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the site mentions
"Projected Price is based on $990 plus projected cost of import"
- so that's the price of the mods? What is the likely price of the amp, if by sea mail from HK to Australia? What do they weigh?

What are the differences - sonic and otherwise - between the two versions?

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Old 26th February 2010, 08:09 AM   #10
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Smile Transformer issues

After re-building about 50 Macs and having my paws in most other Vintage gear, I know that the old builders of amps had a lot of tricks when making the output transformers, a lot of which is lost now.

I replaced the out transformer in a Citation 6550 amp for a customer with a very quality one, and the sound was very different than the other channel.

We founf that the original Citation transformers were wound so they changed characteristics when going from low to high power. They had a shifting curve that a new transformer does not have.

I also had a small pile of 90-A Fisher amps, that I was dumb enough to sell when thinking I was going to be a Rock Star,

They had four EL34s, two biased higher, massive out trans, that shifted curves from low to high power, three feedback loops, and some pretty trick driver stuff also.

I modded a Chinese EL34 stereo amp for a customer about five years ago, can't remember the brand, chrome chassis, and I found the new circuit was beyond the transformers.

I don't think anyone can beat older Fisher, Citation and other trannies, partly because a lot of the secrets of their designs are long gone.

The bottom line is really the transformers
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