Wednesday, June 20, 2018
It uses SIT (Static Induction Transistor). SIT characteristics is quite close to vacuum tube Triode. Based on many user's feedback online is that SIT sounds quite close to Triodes!
SIT, THF-51S, 2SK180, 2SK180ES and such are very high power devices with PD of ~400-1KW. Say we take 15% as efficiency of class A amplification, we can easily get 60W - 150W out of SIT! This is definitely more economical and simpler than to draw 50W out of a 212 tube.
It would be quite interesting and ear opening to try out such designs.
J&K Audio Design
Monday, June 11, 2018
The answer(s) to why transformer / autoformer based volume control is better than resistive volume pots, is quite complex, as there are many factors to it. But, one that stands out, that many may not be aware of, is the Miller capacitance + volume pot effect, that caused the amplifier bandwidth to be reduced significantly when used with a resistive attenuator, or resistive volume pot. This is especially significant if a high value volume pot is used, such as 100K-250K pot.
Everyone knows about Miller capacitance, and why grid stoppers are required, right? But, is he aware that volume pot is part of grid stopper too?
The resistance from the pot has the same effect as a grid stopper (The resistance, starting from input of source, to the volume pot viper section, is part of the grid stopper!), creating a RC low pass filter with the input capacitance of the tube connecting to the volume pot. This RC low pass filter will attenuate any content above the cut-off frequency.
The cut-off will be worsen by higher gain tube as the Miller capacitance is multiplied by the gain, in simple calculation sense, a good example, will be 12AX7. (Could it be the same reason where some prefers lower gain tubes in their amplifier instead of a high gain ones?)
Take 12AX7 as an example, the Cin (Miller capacitance) will be ~200pf, give a take a few or tens of pf.
Say, with 100K Ohm resistive volume pot, the setting now is at mid point of 50K, indicating that there's a 50K+ "effective grid stopper" connected to 12AX7. Ignore the actual grid-stopper connected for the moment. With that, the resultant cut-off shall be:
f cut-off = 1 / (2 * pi * Rg * C) = 1 / (2*3.142*50,000*200pf) = 16kHz (!!!)
That's a freaking 16kHz low pass RC filter in the amplifier without one even realizing it. That is sad...
That's why a lot of folks prefer TVC or AVC versus resistive volume pot. That's why most people will say that the realism is better, the highs are airier and with more body once they migrated to TVC or AVC. Once they tried TVC or AVC, they will never go back to resistive volume pot.
Till then. Go figure.
J&K Audio Design
Still, we will find some short intervals between here and there to publish a few pictures or posts on our Facebook page. For those that have not followed us there, or liked our Facebook page, it is time to do so now to keep yourself updated on the latest development, and have some real time interactions there.
It will be fun. See you there!
J&K Audio Design
Saturday, April 21, 2018
We REALLY hesitated on introducing a fully built transformer volume control due to the amount of manual labor required to solder the TVC to the step-switch. One unit of fully built stereo Transformer Volume Control takes 5-8 hours to solder!
Due to the overwhelming response from readers asking for a fully built TVC as not many are trained on soldering and building audio kits, we are introducing this, for a limited time, for a limited quantity, for batches order only so that we can keep the quality in control.
Also, we think that Transformer Volume Control is something that an audiophile must own as the improvement in sound is just substantial over the price paid (very high cost / performance ratio), we are doing a limited time promotion on standard configuration standard TVC to keep the cost of making them down.
Standard standalone 24-step TVC - U$590/pair (RM-2350) (special batch order price only)
* 24-step, potted with turrets
* Hi-B core only (others - will be normal price)
* Primary 600 Ohm, secondary: 600 Ohm
Note: It will be built in a batch of >=5 sets. You can order 5 sets or more, or wait for 5 sets to be accumulated before build starts. If you order >=5 sets, you can customize it slightly, please email for details.
Fully built stereo unit - U$990/unit (RM-3950) (special batch order price only)
* built with standard 24-step TVC above
* full aluminum chassis
* 24 step attenuator switch
* double-screw chassis
* input grounded, or output grounded, or floating (need to ground at chassis)
* single set of stereo input and stereo output
Note: It will be built in a batch of >=5 sets. You can order 5 sets or more, or wait for 5 sets to be accumulated before build starts. If you order >=5 sets, you can customize the parts used (some at extra cost), please email for details.
Sample fully built TVC is as follow:
* outlook and materials may change depending on parts availability
|TVC - fully built|
|23 step TVC only (shown is 33-step as sample only)|
|Silver Plated OFC wiring|
|33-step version shown as sample only|
|Made in Taiwan 24-step switch|
What's the difference between this and the custom made version? Custom made (more expensive) version offers superior cores - NanoCrystalline (aka Finemet), Permalloy and Amorphous, and is customisable (different primary/secondary impedance, different step-up/down ratios, configurable and etc), different grade of wires, solder, and etc. Sound quality wise, custom made version is a grade higher too (that justifies the price!).
Still, this standard version is excellent sounding - with extended frequency range, solid vocals/body and clarity! The difference between TVC and resistive stepped attenuator is easily differentiated even by non-audiophiles! You owe yourself to own it, trust us!
Till then, grab hold of this opportunity to get yourself a fully built TVC, or a raw Transformer Volume Control, for your long awaited birthday present, Christmas present, 1st draw pay gift to yourself, wedding anniversary present, and(or whatever reasons you can cook up)!
While it lasts... don't regret after promotion is over, or before we regret it.
J&K Audio Design
Thursday, March 29, 2018
Saturday, March 10, 2018
For those that are unaware of the previous article, please visit:
Here goes revision 1 of our proposed ED8000 tube amplifier design. There are tonnes of methods to build ED8000 tube amplifier. Below ED8000 tube amplifier schematic is just one of them, a simple one in fact. It needs only 1pc of 5687 to drive both Left and Right channels, with the use of 1:2 step-up input transformer to provide sufficient gain to drive ED8000 tube to full power.
P/S: circuit has not been tested yet, further fine tuning may be required.
Or, use interstage transformer! With interstage transformer, ED8000 grid leak resistor can be removed, together with the coupling capacitor, which is an even more elegant and better sounding design. Of course, interstage transformer comes with a slightly heftier price tag.
All the components for the ED8000 single ended tube amplifier schematic are carefully calculated for the best effects and are not simply plugged from the sky. If you copy the design, please do not change the values of the components used. If you change it, and it does not sound good, blame yourself! LOL.
The B+ can be slightly tuned by adding a small capacitor of 0.1U - 0.68U after 5U4 rectifier tube rectifier. This converts the choke-input rectification to pseudo capacitor-input, and raise the B+ slightly.
If you build it and like it, let us know! If you need the irons, let us know too! If you see errors in the design, let us know. It was designed in a matter of minutes.
J&K Audio Design
Level 0: link 1
Level 3: depends on type, size and complexity. Email us for details.
Power-trans: link 1
* 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.