DIY Audio Projects Forum

Years ago (1970's),

Just a fun post its a shame someone doesn't make these modules..
Classic quasi complementary output stage
Note in the simulation additional resistors in the emitters of the power transistors. (0.22 ohms) stability improvement.
I used TIP41a in the 70's YMMV. Input cap is 2.2uF.
Note the output capacitor between the speaker and amp module. It has been suggested to increase the value of the capacitor as shown on the back of the box for the module.
A company called Bi-pak made modules (pic)
As an early audio (phool) I bought a couple of these and connected them to some speakers and a record deck.
It was a pretty good experience you just bolted them to a heat sink even the chassis was good enough.
So after trawling the net and with lots of help the circuit was identified from an Ebay sale (pic)
Here is the circuit for any intrepid builders.
Mooly did a simulation as well, the THD was a shock this is what I was listening to at age 15.

I thought it might be interesting for guys here, I have posted the same info in other places.
Special thanks to Biggles and Mooly.

Regards
M. Gregg

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What is the sound of one hand clapping?

Wasn't that the workhorse of a very early Sansui?

Hrm, must pour through service manual collection....

*append*

Yup! That top schematic is basically a Sansui 1000x with one extra gain stage

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-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design

Well regardless of how it sounds distortion levels are very low. I like bipolar out put compared to FETs. Should sound good.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp

That's very interesting, I remember it sounding very good in the 70's.
I even made a stereo version on one PCB that an electronics company I was doing a course with from work offered to make it for me from a drawing of the board I provided. The transistors were ZTX versions but as they are not available the circuit diagram shows components available now. I lost the circuit over the years and curiosity got the best of me because I couldn't find any information on the web. So I traced it out using a photo from an Ebay sale and found someone on the internet who had one in the shed and they checked the component values.
I used it with a NAB tap pre I built for a cassette deck I bought from monolith magnetics. I built the bar driver boards from practical wireless magazine using discrete components a few years later they bought out a bar driver chip.

I thought about a possible rebuild but there are to many other things to do.

The Pics are the images off Ebay that I found and used to trace the circuit. A bit of reverse engineering
I though it might be interesting to someone. I think current dumping was the craze at the time in Audiophile circles.

Regards
M. Gregg

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What is the sound of one hand clapping?

Hi, I've seen it as well. As I recall one problem with it was if there was any sort of failure on the load side it could wipe out the entire amp. I seem to remember having to replace nearly all the transistors in one.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:

• PoddWatt: 5751 / EL84 Push-Pull DIY Tube Amplifier Project
• OddBlocks: KT88 Push-Pull DIY Tube Amplifiers (Mono Blocks)
• ForeWatt: ECC802S (12AU7 / ECC82) DIY Tube Preamplifier Project
• GrooveWatt: Tube (Valve) RIAA Phono Preamplifier Project

We call that the "Firefracker Syndrome" in the shop - 9090DB's are prime examples... outputs go *pop* and everything follows *bangitty, bang, bang, bang!* to the input!

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design

Hi I ran these modules for 5 years never had a problem.
I just used single rail PSU with an output capacitor.

I was intending to do a build but it sort of got waylaid it would probably be along the lines of the Kraken just for fun (Pic)
I would probably use TIP41A outputs. I must admit I liked the Ferranti ZTX packages they seemed like a ceramic material.

Regards
M. Gregg

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What is the sound of one hand clapping?