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Tuesday, January 12, 2016

Supercharger Amplifier

  • Have you ever felt that you are lacking of power in your amplifier?
  • Have you got stuck because your existing amplifier has nostalgic value?
  • Have you thought of upgrading but still like the tone of your current amplifier? 
  • Have you imagined that what would happen if you have a couple of Watts more? 
  • Have you ever liked a speaker so much but it is too difficult to drive for your existing amplifier that you liked so much too? 
  • Have you imagined what a supercharged 45, 2A3, 50, 300B, or any low power direct heated tube would sound like?
Now here lies the answer! 

We have heard of pre-amplifier, power amplifier, integrated amplifier, and various amplifiers. Supercharger amplifier is a rare term, isn't it? 

This is not something new but it is not that common in tube amplifier world. A supercharger amplifier is THE power amplifier for integrated and power amplifiers -> power power amplifier? LOL... That would be funny, right? Therefore, supercharger amplifier or turbo amplifier will be a better term to use.

What it does is to boost the power of the existing amplifier by manifolds! What one needs to do is to connect the speaker output of the current / existing amplifier (yes, the speaker output to the supercharger amplifier, and the outputs of the supercharger amplifier are connected to the speakers. The picture above shows how it is connected. Simple isn't it? 

Some might ask, why can't I take a high power amplifier in the market, and connect it in such a way? Well, unless it is designed to work this way (like Musical Fidelity 550K Supercharger), most amplifiers aren't destined to work this way. The powered output from the existing amplifier would have overloaded the input stage of the high power amplifier and fried the amplifier. Also, there would be redundancy in the amplifier since the high power amplifier would have their own pre/driver stage to properly drive the power stage into full power. We would miss all the goodies (tonality, character, and etc) that the existing power amplifier would bring too. 

What we need is a supercharger amplifier that does not have the pre/driver stage, that could make full use of the goodies brought over from the existing high quality amplifier - direct drive, with honest transfer of the characteristics from the source lower power amplifier to the supercharger amplifier! In order to do so, the best possible way would be to introduce a high inter-power-stage transformer with a high step up factor to produce the signal drive required by the supercharger amplifier with a direct power stage. 

One might ask, can I connect an ordinary output transformer in reverse to do so? Yes, you can! It will work, but not optimally! The gain might not be right. The design of the output transformer is not suited for power to voltage conversion too. Ordinary output transformer converts high impedance to low impedance as a means of power transfer. The inter-power-stage (IPS in short) transformer is for voltage amplification. 

The secondary reflected to primary distributed capacitance will affect/change the distributed capacitance and the inductive resonance of the transformer. As output transformer secondary is always low impedance, the resonance will be attenuated by the load (therefore output transformer secondary must always be connected to a load). 

For IPS, the secondary of the transformer is always appeared to be open or at high impedance due to being connected to tube grid and grid leak resistor. With that, the resonance is fully reflected to the primary. This will have negative impact on the operation of the amplifier and therefore is not recommended to use ordinary output transformer as IPS. Of course there is a way to design an output transformer that can work as an IPS but this is something of a compromise and is not recommended. 

Some others might ask, can I use an ordinary step-up transformer to do the job? Yes, you can, if the step-up transformer is designed for this task - if it is with sufficient core size to handle the high signal level, and with heavier gauge cables to handle the current.



Above is a famous direct coupled Loftin White 2A3 amplifier. Needless to say, it is a great sounding amplifier. The only drawback is the limited output power to drive common speakers. What we can do here is to use a supercharger amplifier to boost the output power to a decent 40W-50W level, such as using the famous 212 tubes, be it NOS, or from new manufacturers. The supercharger amplifier is designed with very minimum components, and therefore it posses the least character or coloration of its' own, and is much cheaper & simpler to manufacture too. Of course, other power tubes like 211, 845, 833 and such can be used too with great results.

Where can we get these IPT (inter-power-stage) transformers to build/design the Supercharger Amplifier? Good new is, J&K has it, and we are offering it as our Level 2 and Level 3 custom made models for IPT. Sorry, we cannot do it at Level 0 or Level 1 for now due to the complexity involved, and the effort we spent to develop these IPT. Here are the prices in matched pair, rated at 10W power handling.

Level 2 IPT - U$590 (for driving 211, 212 and less demanding tubes)
Level 2 IPT - U$790 (for driving 845, 833 and high demanding tubes)
Level 3 IPT (1:5 step-up) - U$1090 
Level 3 IPT (1:10 step-up) - U$1490
Level 3 IPT (1:20 step-up) - U$2290 

Now isn't this a GREAT news?  

For those that wants a fully built system, please email us for more details and quotation. 

One warning for the users though - remember this rule - garbage in, garbage out. All the shortcomings or all the greatness of the existing amplifier will be amplified manifolds with such design topology.

J&K Audio Design
1/12/2016

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.  
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Level 3: depends on type, size and complexity. Email us for details.

Iso-trans: link 1, link 2

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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