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The phrase “Modyfikowany wzmacniacz JLH PCB by Jerzy Gołaszewski” most likely refers to the project “Modyfikowany wzmacniacz JLH” published in Elektronika dla Wszystkich, issue 8/2010, starting around page 15, authored by Jerzy Gołaszewski. The same issue listing confirms this project separately from AVT2950, which was the following project, “Sterownik kamery OKO” — so AVT2950 is not the JLH amplifier kit number. (zanotowane.pl)
I do not see reliable public evidence that Gerber/PCB production files for this exact Gołaszewski JLH amplifier are officially available online. The indexed material points to the magazine article and scanned references, not to an official standalone PCB package. The project is a modified version of the classic John Linsley Hood 1969 Class-A amplifier, with approximately 30 V single-supply operation, about 2 A quiescent current per channel, and reported output power around 12 W into 8 Ω under those conditions. (zanotowane.pl)
The original JLH 1969 amplifier is a minimalist single-ended / quasi-complementary Class-A power amplifier. It became popular because it uses very few active devices, has a simple feedback structure, and gives a characteristic “smooth” Class-A sound when built correctly.
The Gołaszewski version is not just a direct copy of the 1969 circuit. From the available indexed article text, it appears to be a modernized discrete-transistor implementation with:
In practice, this is a hot-running, inefficient but sonically attractive Class-A amplifier. At 30 V and 2 A, each channel dissipates roughly:
\[ P{DC} = V{CC} \cdot I_Q = 30\,\text{V} \cdot 2\,\text{A} = 60\,\text{W} \]
This is the idle power per channel, before considering transformer and regulator losses. A stereo amplifier can therefore dissipate well over 120 W continuously.
Approximate operating assumptions for the Gołaszewski-style JLH:
| Parameter | Typical value / comment |
|---|---|
| Topology | Discrete BJT Class-A JLH-derived amplifier |
| Supply | Single supply, about +30 V DC |
| Quiescent current | Around 2 A per channel |
| Output power | Around 12 W / 8 Ω; lower into 4 Ω depending on current limit |
| Output coupling | Large electrolytic capacitor, often bypassed by film capacitor |
| Speaker load | Preferably 8 Ω |
| Heat dissipation | Very high; large heatsinks mandatory |
| PSU requirement | Low-ripple, preferably stabilized or actively filtered |
The source snippet indicates that due to relatively modest negative feedback, the amplifier does not strongly suppress supply ripple, so a clean supply is important. A regulated or active-filtered supply is therefore recommended. (zanotowane.pl)
If you are looking specifically for the PCB, the most important point is this:
So if someone labels a board as “AVT2950 JLH”, that is probably a misidentification. The JLH board may have been printed in the article, but I would not assume that AVT2950 is the amplifier PCB.
Because PCB artwork from a magazine article is copyrighted, I should not reproduce the copper layout here. However, if you have a scan/photo of the board or schematic, I can help you:
The currently indexed sources show that Jerzy Gołaszewski is also the author of the book “Wzmacniacze audio. Poradnik konstruktora”, published by BTC, which covers amplifier construction, audio components, measurements, power supplies, loudspeaker protection, and practical amplifier projects. (kamami.pl)
For the exact “Modyfikowany wzmacniacz JLH” article, the clearest indexed match is Elektronika dla Wszystkich 8/2010. The Cyfronika issue listing marks that issue as unavailable and lists the JLH project separately from AVT2950. (cyfronika.com.pl)
Modern DIY practice for this kind of amplifier usually improves the original concept by using:
A JLH amplifier has much less supply rejection than a modern op-amp-like power amplifier with differential input stage and high open-loop gain. Therefore, ripple on the supply rail can appear as hum at the output.
For one channel at about 2 A, a simple bridge rectifier plus capacitor supply may need very large capacitance. The approximate ripple is:
\[ \Delta V \approx \frac{I}{2fC} \]
For 50 Hz mains, full-wave rectification gives 100 Hz ripple. With \(I = 2\,\text{A}\) and \(C = 10\,000\,\mu\text{F}\):
\[ \Delta V \approx \frac{2}{100 \cdot 0.01} = 2\,\text{V}_{pp} \]
That is too much for a low-PSRR Class-A audio amplifier unless additional filtering or regulation is used.
A practical PSU should use one of the following:
At 30 V and 2 A, each channel idles at about 60 W. If two output devices share this power, each may dissipate roughly 25–35 W depending on topology and signal condition.
Recommended heatsink target:
\[ R_{\theta SA} \leq 0.5\,^\circ\text{C/W per channel} \]
Preferably lower if the case has poor ventilation.
Practical temperature targets:
Do not build this amplifier in a closed small enclosure without ventilation.
For a newly assembled board:
\[ V{OUT,DC} \approx \frac{V{CC}}{2} \]
For current measurement, if there is a known emitter resistor:
\[ I = \frac{U_R}{R_E} \]
Example:
\[ R_E = 0.22\,\Omega,\quad U_R = 440\,\text{mV} \]
\[ I = \frac{0.44}{0.22} = 2\,\text{A} \]
If you want to build or restore this PCB, check the following first:
For a JLH amplifier PCB, good layout is critical:
A speaker protection relay is strongly recommended, especially because single-supply capacitor-coupled Class-A amplifiers can produce turn-on/turn-off transients.
Use:
The project you mention is almost certainly Jerzy Gołaszewski’s modified JLH Class-A amplifier from Elektronika dla Wszystkich 8/2010. It is a single-supply, hot-running Class-A design around 30 V / 2 A per channel, capable of roughly 12 W into 8 Ω, requiring an excellent power supply and substantial heatsinking. The exact PCB files are not clearly available as official public Gerbers; if you have the board or article scan, I can help verify the schematic, component values, startup procedure, and safe bias settings.
