Update in Sept 2014

August 10th, 2014

UPDATE: 27th Sept, 2014

My website shared to another domain (game related for my son) was attacked by Malware and thus my account was deactivated by the host for few days.  Finally I get all affected files removed and purchase Delicated IP in order to reactivate the account. I hope it will not happen again!  Sorry for all the iconvenience and please enjoy browsing here again.


Hi, I continue to sell the Toshiba J74BL and K170BL match pairs.  Price is as in the STORE page.

I am relocating my lab from HK to Singapore and I think it will take another month to settle down everything.  Thus shall be able to offer more Toshiba power transistors for F5T use in NNNN & PPPP matched.  Stay tune.

(New) – Shipment has arrived on 18 Aug, 2014.  Total 64 boxes and will take me some time to unpack and set up my lab again.  Will update more later.


Spencer Cheung

F5T Pre-amp + FDA-2A AD1955 DAC in one box

May 11th, 2014

This is a pre-amp plus a FDA-2A in one box.  It was built in year 2012.  I use a old Yamaha DA8X box to house eveythings insides.  See the pdf files at bottom for details.


FDA-2A with USB, Optical and AES digital input.  Push button for digital input selection at the front panel.

DAC direct output is available in RCA sockets.

F5T Pre-amp:

Alps volume control from DAC output and note that there is no other analogy input for the preamp.

The pre-amp is based on Nelson Pass F5T power amp design and striped down to only one pair mosfet and lower bias current at about 200mA.  Supplier voltage is at about +/-23V with a small transformer.  Power mosfet is using Toshiba J200 / K1529 pair and casing is acted as the heatsink of power mosfet.

A headphone jack is connected in parallel with the pre-amp RCA sockets.  It can drive most headphones due to sufficient high bias of the power mosfets.


Details refer to this pdf file: F5T-Pre_DAC



Sale for this month (May 2014)

April 21st, 2014

During last week, I manage to have a short trip back HK for few days.  Thus I have limited time to sort out the kits for sales.  Here is what I can offer at this moment.

1. F5T kit A or B in the list.  Total 1 kit A OR kit B is available.  Note the jfets and mosfet are with updated prices.


Link of kit: http://www.fetaudio.com/archives/1725


2. FDA-2A AD1955-WM8805 DAC kit is only available for 2 sets.  HKD$1550 each.

Links: http://www.fetaudio.com/archives/1666


3. Toshiba K1530 / J201 pairs (not match).  This single pairs is good for bulding a mini F5T as a headphone driver.  Offer price is same as old price at HK$100 a pair.  Shipping and paypal fee are additional.


4. Toshiba Jfets K170BL and J74BL is still available and price refer to below announcement.


That is all for this moment. Thank you.

Sales Announcement Update

February 15th, 2013

Date: Revised on 23rd Mar 2014

Toshiba 2SJ74BL and 2SK170BL match pair for sales: (NEW PRICES from 1st Nov, 2013)

  1. 2sk170BL/J74BL match pair HK$120/pair (Pair = K170 x 1pc  and J74 x 1 pc)  (about US$16). Idss 6.4 to 9mA only.
  2. 2SJ74BL : HK$160/pair (about US$22 – 2 pcs) or HK$320/quad (about US$44 – 4 pcs). Idss 6.4 to 11mA.
  3. 2SK170BL match quad : HK$100 (about US$13 – 4 pcs). Idss 6.4 to 9mA only.
  4. Note that Idss of K170 at 10mA and above is basically not available.  If found, the price is HKD$100 each.
  5. Unmatch will be same price as match above.  Only BL grade of above jfets are available.


Shipping is HK$35 (US$4.5) to worldwide by registered airmail and paypal fee 5.5% (4.5% for purchase amount >= HK$500). All matched within 0.2mA Idss @ 10Vdc.  Maximum match is 4 pcs K170 and 4 pcs J74 with same idss match together in one group.  Note that the temperature at measurement is about 28 to 30 degC in Singapore.

There is further delay for the sales of other kits and parts.  Tentatively it will be by 2nd half of 2014.

Thank you for all the support.

Toshiba 2SJ74BL measurement

January 3rd, 2013

Many diyers have been buying some fake 2SJ74 from China sources or even from US source and thus some of them ask me for the measurement curve of this genuine Toshiba part.  Here is the file which you can enlarge to see the curve and estimated Yfs (gain) of the part.  The jfet selected is at about 10.8mA Idss (top curve).  The setting of Tek 577 is highlighted for easy reference but you can zoom in the pdf to see actual setting of equipment.


Note that the part is laser marked as it is new part production in 2008, probably the last production batch in Japan.  For ink mark, those are very old part that I have sold before – 2SJ74V.


You may notice that I have increased the price from 2013 because there are not too many stock left for sales.

J74 measurement