I was asked to suggest a voltage regulator for the First Watt (Pass DIY) B1 buffer. One thing led to another and the next thing I'd sketched up a circuit board for the buffer as well as the regulator.

It's like a B-board, but with the JFET buffer instead of the diamond buffer, and with a single supply and, hence, the coupling caps front and back. Since it's using JFETs for the buffer I used a JFET for the pass device in the regulator, too.

Full credit to Nelson Pass for his design.

Eagle files do not show 2SK170 because the package is not in Eagle. All transistors 2SK170 or equivalent. Zener is 18-22V DO35 or DO41 i.e. Vishay BZX85. V++ is 5-15 V above whatever you select the Zener reference to be.

This is a followup of sorts to the X-reg, though there is nothing original about the circuit this time around.

It's just a Zener voltage regulator with a series pass transistor. I lifted this particular configuration from the Pionner C-21 preamplifier and re-tuned it for op amp applications. My main interest here is trying to make a small and convenient board layout.

I've used this circuit block already in the Sapphire amp and come away impressed.

The output is about 1 V less than the Zener voltage, and the input voltage should be about 3-6 V above the Zener reference voltage. I'm working here with 17 V unregulated supply and 12 V Zeners, but the values can be reconfigured easily enough for any output from 4-24 V

This is a low current circuit. If you are just powering a few op amps, no heatsinks are needed. Above 25 mA small heatsinks are a good idea. The circuit is not designed for output currents above 100 mA.

Found this today: DC Coupled Amplifiers for Audio from an 11 year old web page by one Knut Harald Nygaard.

I've taken some minor liberties with the circuit, shown in the second, color image below. Replaced the current sources with resistors and moved the output buffer out of the feedback loop.

Note the resultant double symmetry of the dual-diamond buffer topology, highlighted in blue.

So,I've been pondering this for a while,and I'm going to finally build it.

Basic idea- Fairly simple Push-Pull amplifier,that will deliver ~50Wpc,Using common/available tubes.
I decided to go with the 'usual' octals,since they are all a similar basing/pinout(7ac?).
This leaves us open to use 6L6,EL34,6550,KTxx,etc. for output tubes.
We'll have to have a -Vg1 supply with a wide voltage range to cover the needs of all those tubes,shouldn't be a problem.

The power transformer is a big 1kva/500W beast,used in the Tektronix 545A. (P/N 120-120)
Pete Millett was kind enough to post some data on this transformer,and a few others here:
Tek power transformers

The output transformers are rated ~100W,they came from a pair of old RCA MI-12188A amps.
They are ~3.5-4.0K (p-p) primary impedance.
There is some information on these amplifiers/transformers here:
The Shrine of the Ancient and Most Excellent RCA MI-12188A Power Amplifier...

Just finished fine tuning my First Watt F5 clone.

I built it about a year ago out of parts that I had on hand back then, including a power supply reused from another project. The resulting sound was rather disappointing. Now I spent time matching transistors and tuning the feedback network. The amplifier now is very close to the performance described in the original service manual.

I am listening to F5 (the music is Tchaikovsky performed by Wiener Philharmoniker and von Karajan) and realizing that it is so good that if this was my first amplifier, I might not be interested in building anything else.

I am a lucky man!

I´ve got two NOS TDA1541A double crown DAC´s from a friend





He bought the last from Philips a long time ago...


Just now i swapped them on my Red Baron modules...



What could i say.... They will never leaving the DAC modules again !!!

After reading so much over this amp, i will start a new project for my Hornspeaker

Let´s see if the F5 can play in the same league as my 300B mono´s




The parts




Schaffner FN 2070 - 3A multistage EMI Filter





Antek AS-4218 - 400VA transformer





SST03 Softstart module from Sjostrom Audio
Design without extra transformer




RFB03 rectifier bridge from Sjostrom Audio



with IXYS DPG 60 C 200 HB HiPerFRED diodes

...

On the occasion of selling the 100th and last VSPS Stereo Kit, it's time to consider what direction(s) RJM Audio will take over the next little while.

A. A minor revision of the stereo VSPS board is planned. Just a point release to address feedback I received over the last couple of years. Point release on current boards (Phonoclone 3, VSPS 300, Sapphire) expected when I deplete existing stock and have to re-order.

B. Since my circuit designs are essentially modular (the voltage regulation of the Sapphire headphone amp could be used with the Phonoclone, the output stage of the Sapphire could be detached and used on the output buffer on the VSPS...) I'm going to work on bringing that vision to a concrete reality by developing "swap-in swap-out" circuit boards... like those toys where you can change out the head, body and legs of a character to make many variations.

1. X-reg board
2. Zener reg board
3. basic op amp gain block board
4. VSPS and

...

Biggest changeover in many years.

Denon DP-2000, DA-307, DL-103 turntable/tonearm/cartridge
Phonoclone 3 with 160 VA Plitron power supply
47 Labs "Treasure" model 0247 preamplifier
47 Labs "Treasure" model 0347 amplifier
Onkyo D-605SR speakers
Cables by oyaide, mostly.
(photo: Pentax K10D, Pentax FA 31mm F1.8 AL Limited)

Denon DL-A100

Transparent DL-103 for Denon's 100th anniversary.