Silicon ChipRetro Round-Up: Nostalgic Radio Is Back! - March 2014 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Cruise ships are technical marvels
  4. Feature: Digital Cameras Come of Age by Barrie Smith
  5. Feature: Retro Round-Up: Nostalgic Radio Is Back! by Kevin Poulter
  6. Subscriptions
  7. Project: Arduino-Based GSM Remote Monitoring Station by Nicholas Vinen
  8. Project: Precision 10V DC Reference For Checking DMMs by Jim Rowe
  9. Review: Cadex C7400ER-C Battery Analyser by Nicholas Vinen
  10. Project: Burp Charger For NiMH & Nicad Batteries by John Clarke
  11. Product Showcase
  12. Project: 230V/10A Speed Controller For Universal Motors, Pt.2 by John Clarke
  13. Book Store
  14. Feature: A Look Back At Ferrite Core Memory: Bits You Can See by Brian Armstrong
  15. Vintage Radio: The 1956 Sony Gendis TR-72 transistor radio by Dr Hugo Holden
  16. Order Form
  17. Notes & Errata
  18. Market Centre
  19. Advertising Index
  20. Outer Back Cover

This is only a preview of the March 2014 issue of Silicon Chip.

You can view 46 of the 112 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Items relevant to "Arduino-Based GSM Remote Monitoring Station":
  • Arduino software for the GPRS Remote Monitoring Station (Free)
  • Arduino GPRS Remote Monitoring panel artwork (PDF download) (Free)
Items relevant to "Precision 10V DC Reference For Checking DMMs":
  • Precision 10V DC Reference Mk2 PCB [04104141] (AUD $5.00)
  • Precision 10V DC Reference Mk2 PCB pattern (PDF download) [04104141] (Free)
  • Precision 10V DC Reference Mk2 panel artwork (PDF download) (Free)
Items relevant to "Burp Charger For NiMH & Nicad Batteries":
  • NiMH/Nicad Burp Charger PCB [14103141] (AUD $15.00)
  • PIC16F88-I/P programmed for the NiMH/Nicad Burp Charger [1410314A.HEX] (Programmed Microcontroller, AUD $15.00)
  • Complementary pair of logic-level Mosfets (CSD18534KCS/SPP15P10PL-H) (Component, AUD $7.50)
  • Firmware (ASM and HEX) files for the NiMH/Nicad Burp Charger [1410314A.HEX] (Software, Free)
  • NiMH/Nicad Burp Charger PCB pattern (PDF download) [14103141] (Free)
  • NiMH/Nicad Burp Charger panel artwork (PDF download) (Free)
Items relevant to "230V/10A Speed Controller For Universal Motors, Pt.2":
  • 230V/10A Universal Motor Speed Controller PCB [10102141] (AUD $10.00)
  • 230V/10A Universal Motor Speed Controller prototype PCB [10102141] (AUD $2.50)
  • PIC16F88-I/P programmed for the 230V/10A Universal Motor Speed Controller [1010214A.HEX] (Programmed Microcontroller, AUD $15.00)
  • Parts for the 10A 230VAC Universal Motor Speed Controller (Component, AUD $45.00)
  • Firmware (ASM and HEX) files for the 230V/10A Universal Motor Speed Controller [1010214A.HEX] (Software, Free)
  • 10A/230VAC Universal Motor Speed Controller PCB pattern (PDF download) [10102141] (Free)
  • 10A/230VAC Universal Motor Speed Controller panel artwork (PDF download) (Free)
Articles in this series:
  • 230V/10A Speed Controller For Universal Motors, Pt.1 (February 2014)
  • 230V/10A Speed Controller For Universal Motors, Pt.1 (February 2014)
  • 230V/10A Speed Controller For Universal Motors, Pt.2 (March 2014)
  • 230V/10A Speed Controller For Universal Motors, Pt.2 (March 2014)

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Nostalgic Radio is back! Retro Rou Enjoy Golden Oldies with modern reliability Retro radios have that style reminiscent of bygone days when we enjoyed the family “wireless” in the kitchen or loungeroom. Now we can enjoy the bygone features knowing the new radio has a warranty and should last for years. Modern retro receivers vary in size, case design, sound fidelity and build quality, so this comparison is a guide. The sound quality is not hi-fi but most listeners are happy to relax with the news, talkback or old tunes reproduced in a “mellow” tone. S even “retro” radios are reviewed in detail here and to remind us there’s still life in some vintage radios, a few old-timers are mentioned. Perhaps the ideal for a true vintage-look radio for daily use is to take the approach used in the Mini Entertainment Centre (last month) but use an old-style cabinet. However, the D-I-Y approach may well miss out on the latest developments, such as DAB+, unless you use a radio receiver offering this facility. Even manufacturers of some “retro” sets seem reluctant to include DAB+, probably because of increased cost. 18  Silicon Chip All the ratings in the comparison chart are largely subjective. In most cases the tiny loudspeakers being used immediately limit the possible sound quality and volume. Most of these radios were purchased; only a few were provided as review samples. DAB+ Where available (and that’s increasing all the time) Digital Radio (DAB+) reception is certainly noise-free but in many cases, the sound appears to lack tone in the small loudspeakers, compared to that from the FM stations. siliconchip.com.au Retro Radios, Mantels and Portables Brand Model AM SW DAB+ AC or Audio Audio Audio Volume Audio Tone Retro Overall Street DC in out Output Level Quality Control Rating Rating Price Bush TR82  (LW)  AC/DC - Line 2W 8 7  10 Tesslor R601  - - AC RCA Line 4-5 W 9 8 - 10 Crosley Ranchero  - - AC 3.5mm - 1W 8 7 - 9 Roberts Revival - -  AC/DC AUX Line 1W 7 7 - 9 MagicBox Astor - -  AC/DC - - .7W 6 6 - 8 Nostalgic CR-065   - AC L/R line L/R 3+3W 9 6 - 8 Bush Heritage - -  AC AUX - 10+10W 10 10 7x EQ! 8 9 $90 6 $195 7 $99 8 $279 7 $89 7 $199 10 $246 Not tested but worth considering Roberts Vintage - -  AC/DC* 3.5mm Line 1W ** AVES Classic - -  AC/DC - - 2.5W ** AVES Tango - -  AC/DC - - 2.5+2.5W ** ** - 8 ** - 7 ** - 7 ** $229 ** $99 ** $129 Notes!! 1 The highlighted Bush Heritage features contributed to the highest rating. This was the only radio that replayed DAB+ in with good sound. 2 The audio quality compares “apples with apples” and not to much larger hi-fi systems. 3 Prices are the best average at the time of printing. Some radios are occasionally on special up to $100 cheaper. Example: we purchased the Heritage at $179. 4 The Tesslor will get a score of 9 or 10 when technical issues are solved. An earlier model was finished in very attractive high-gloss. 5 The MagicBox is a great lightweight fun portable and the only small radio reviewed here. 6 The Nostalgic Radio would be better without the CD player, as it may not last, plus wiring standards could be improved. It would be good to try quality speakers too. 7 * Roberts Vintage model will operate on AC, alkaline or rechargeable batteries. 8 ** Not tested. undup By Kevin Poulter AM reception should always be included in receivers, to cover areas where DAB+ cannot be received. Sadly, as our comparison chart shows, AM is fitted to only about half the retro radios in the survey. CD Players Some of the units have CD players. Personally, I have major reservations about these, as it has been my experience that CD players in low-cost equipment often fail prematurely and then typically cannot be repaired. While many readers may not agree with me, I cannot see the point in including a CD player in a “retro” radio and believe they would be better off without them. This quick reference table shows all models included in this mini-survey. All offer FM reception but less than half have AM and only seven offer DAB+. Only the Bush TR82 has all three – with LW thrown in for good measure (not really usable in Australia!). None have provision for an external speaker, although all include a 3.5mm headphone socket. About half have a line output socket, which could also be used to drive an external amplifier and speakers for significantly improved sound. Individual reviews of each of these (except for the last three) begin overleaf. You’ll find more detailed information, suppliers links, DAB+ information, etc, at www.aaa1.biz/SC/retro.html console sets than mantel radios. In preparing this article, we compared retro radios to some larger portable vintage radios. Some had more fullbodied sound, like the ghetto-blaster below, however none were even close to the sound quality and features of the Bush Heritage. However, because of the low prices asked for these, they may well be a better option than a “retro”. Vintage Many readers prefer the “real thing” and would prefer to restore vintage radios, usually of the valve genre. Typical valve radios had a larger speaker and the overall sound quality, particularly in the bass, is better. This applies more to siliconchip.com.au Post-60s solid state radios are an option too. All these were available at $50 or less at HRSA (Historical Radio Society of Australia) sales or Op Shops. The near mint-condition GhettoBlaster on the right came from an Op Shop for just $15. March 2014  19 Crosley CR3022A Ranchero The Crosley Ranchero AM/FM radio (above) looks like an old-style car radio installed in a mantel radio cabinet. The Australian model is only available in black and the USA version only available in red. Compare this to the original 1950s “PYE” set (AM only) shown below and you can see where the styling ideas came from. Other brands offered similar designs. 1950s “PYE” set (AM only). Styled like a number of brands in the 50s including the Australian PYE, this design is reminiscent of a car radio installed in a mantel case. The receiver is AM/FM with a MDF case in superb glossy black piano-finish. In USA red is the only choice on the Crosley website. With clean, compact lines, the authentic look is retained by placing the AM/FM/Aux-in switch on the back panel. A minor point, the raised “pointer” on the function knob did not line up with the function it was set on. The FM wire aerial needed fully extending in our metro area, it then received a wide range of stations well. Sound quality is good compared to others and if you like the style, it will look appealing on the shelf. MP3 players and the like can be connected via a 3.5mm input socket and a headphone socket is provided. Typical of all the sets in this roundup, sound quality using a good pair of headphones is significantly better than using the tiny internal speakers. Size: 333 x 180 x 135mm (w x d x h) Pros: Good design and sound, external aerial socket. Cons: None. Source: iWorld (see links at finish of this article). Price: $99.95 Overall Rating: 8 out of 10 20  Silicon Chip Nostalgic Music System, Model CR-065 The Nostalgic Radio is very similar to European Philips and other euro brands in the early 1950s. Built in a timber case, it’s larger than all other mantel radios in this roundup. Features include AM/FM with two shortwave bands, CD player, MP3/USB port and SD/MMC card port. The biggest unit by far, it has two speakers in a larger “speaker box” for more full-bodied sound and in stereo, to boot. There’s no brand on this unit; the title comes from the instruction book. On opening the well-packed radio I found the CD player was not working. The supplier said this was highly unusual and rather than paying expensive freight to return it, he offered a discount. The CD mechanism is direct drive, with no belt, so the fault could range from an open circuit motor to the electronics or connections. Regardless, I won’t miss a lower quality CD player that’s bound to have a short operating life, like many a CD player in small systems. On this set, you need to use the controls gently, as they are not rugged. The outer rings of the main knobs are not tone or other Maybe the Nostalgic is a little too retro: it certainly doesn’t follow modern wiring techniques! For example, the yellow LT AC wires are not twisted, the white FM wire easily drapes over 240VAC power leads and the full-wave rectifier diodes are close to audio circuits. The speaker leads are also not twisted or clipped to a specific path and the speakers are unlabelled. siliconchip.com.au function, just decorative and the large volume knob is mounted on a very small pot. Also,the piano-key switches are connected via levers to light-duty switches. The Chinese English in the manual is ‘different’, however you get the gist of it. For example “Do not wet hands touch the power cord.” “During to use CD/USB/SD card, the occasional silly machine or confusion...” “to save power and security, for a long time do not use this product, please ensure that the full power interruption.” The latter translates to: “If you are not using the unit for a while, disconnect it from the mains, as only the low voltage DC is switched.” My advice is to use a switched power board and always turn off the mains after use. It also mentions a cassette player, which the unit does not have. Designed by new-generation technicians who were not exposed to tried and proven techniques, the quality, wiring and placement of circuit boards could be improved. For example, the FM antenna wire drapes over the mains leads or power transformer and the transformer secondary power leads are not twisted, while the bridge rectifier is close to the audio section. However the radio is an interesting mantel and if you like the appearance, it may suit you. FM reception is improved by extending the telescopic aerial on the back panel and the FM tuning has a feature where the dial illumination changes to blue when tuned to a station. After reading a USB or SD card with MP3 music, the controls resemble a CD player, with fast forward, program, repeat and more. “AUX in” will suit many portable music devices and there’s also 3.5mm line out and headphone out sockets. Size: 510 x 290 x 340mm (w x d x h) Pros: Large cabinet enables two speakers and big sound. Many features. Cons: Electronics could be better built. The piano-keys and volume control are not durable. Source: eBay - warehouse_seventeen, or direct - see our links page. Price: About $200 Overall Rating: 7 out of 10 Roberts Revival Model RD-60, DAB+/FM “Feel the quality” is a term that fits well with this medium-size portable. It looks good, styled closely to an early 1960s transistor radio but with modern DAB+ and FM. If you like the distinction of magnificently crafted ‘retro leather’ covering over a styled MDF case, with gold highlights and even a gold-plated telescopic aerial, this radio should be on your wish-list. Unfortunately there’s no AM. Now claimed to have 120 hours of battery life on 4 x D size cells, this radio comes in red and cream (limited stock), though most will choose red. The Revival features rotary tuning and volume controls, RDS station name display, a stereo line out socket, and headphone socket – which delivers excellent sound. Like all portables, DAB+ sound could have more bass and midrange. The sound output is quoted as 1 watt, which appears correct and unlike others, it does not increase distortion excessively near full volume. Interestingly, the speaker has a plastic port to help improve sound quality. The port seemed to work best when the rear cover was open for battery access! siliconchip.com.au Roberts Revival DAB+/FM radios are available in red or the rarer cream colour below. Beautifully made, this equates to a little heavy – and more expensive ($279 RRP). The goldplated telescopic aerial is the best-looking you will ever see. If you like the style and don’t need AM, Roberts is highly recommended. Other features include: station name / multi preset mode, one-touch instant access to favourite stations, FM RDS station name display, easy-to-read 16 x 2 line LCD readout, amber display backlight, stereo line-in socket for iPod / MP3 playback, stereo line-out, stereo headphone socket, AC adaptor included. Size: 260 x 130 x 160mm (w x d x h) Pros: Style, quality, features, stereo line out. Cons: No AM, fairly expensive. Source: Harvey Norman, The Good Guys and Retravision.  Price: $279 RRP; $216 at Big W on-line Overall Rating: 8 out of 10 Also consider: Roberts Vintage (not tested but similar to the Revival) The Vintage beautifully blends ‘retro leather’ cloth finish and wooden effect side panels with modern DAB+/FM technologies. You can enjoy limited station presets and a favourite station button. Features: up to 80 hours battery life, built-in batter charger – ideal for standard (C size) rechargeable batteries, FM station name display, rotary tuning and volume controls, station name /multi-preset mode, one-touch instant access to favourite station, USB socket for software upgrades, aux-in for iPod / MP3 playback, headphone socket, battery or mains operation via AC adaptor (included). Pros: Style, quality, features, battery charger built-in. Cons: No AM, fairly expensive. Price: $229 RRP; $189 at Appliances on-line (see links for more) Overall Rating: 8 out of 10 March 2014  21 MagicBox “Astor” FM/DAB+ The MagicBox “Astor” FM/DAB+ is amazingly light, with a chrome and pastel appearance. Great for teenagers to older people who like to listen to music or talkback, without needing generous bass or treble. A fun, lightweight, attractive, colourful portable, great for personal or mobile use, like picnics. Good volume in a very portable radio, with excellent quality on headphones too. A telescopic aerial ensures top reception on FM, plus DAB+ areas. A host of discreet buttons enable station scan, set favourites, info/ menu and the Astor can store your best 9 DAB+ and 9 FM stations. Power choices are four AA cells or the supplied mains plug-pack. Size: 225 x 680 x 150mm (w x d x h) Pros: Colourful, fun look, super-lightweight, clear sound, many function buttons. Cons: None. Source: Selected Harvey Norman stores. Price: $89 RRP Overall Rating: 8 out of 10 Bush TR82DAB - DAB+/ FM/AM/LW Bush TR82 AM/FM/MW/DAB+ is a near-identical copy of their 1959 model. Priced about $85-$99, this large lightweight radio has a larger speaker and is great value. You’ll love the style of this near perfect reproduction of the iconic 1959 Bush TR82 transistor radio, with classic style by Ogle Design. This Bush model was reviewed in SILICON CHIP, September 2013. Taller and bigger than most transistor radios, it delivers. The inclusion of AM (MW) is excellent, as many AM stations are top of radio ratings around Australia and DAB+ is not yet received in many areas outside of the capital cities. Most of all, the price blows away other DAB+ receiver brands with tiny speakers. DAB+ tuning, plus buttons for presets and the LCD readout are inconspicuous on the top panel. The ten station presets are a great feature, however when used only on mains, they disappear after power is disconnected. Installing batteries overcomes this, though it would be even better Too late for the roundup – but worth a look: Two other contenders came in as we completed the roundup. The Roberts Vintage model is about $229, with builtin battery charger, DAB+ / FM, Aux in for iPod / MP3 playback, battery or mains via the included AC adaptor. 22  Silicon Chip The AVES Classic DAB/FM Radio retails in Australia for $99 RRP. Features include: Alarm, snooze and sleep Timer, 2.5W RMS, AC Adaptor for mains, or 4 x 4C cells. siliconchip.com.au if the memories were flash type, or if there was a memory battery. The station search resembles “seek” on a car radio and is excellent. There are so many DAB+ controls and features, reading the handbook on the web is a good idea. Reception AM and FM stations are received well. Numerous DAB+ stations can be received in most state capital cities and suburbs, Bush says “if no DAB+ signal is found in your area . . . relocate your radio”! So be sure DAB+ can be received in your area before purchase, if DAB+ is a major purchase decision. A great test of DAB+: I tuned an AM station and placed the Bush near a noisy computer power supply, resulting in overwhelming noise and zero AM reception. Switching to the same station in DAB+ produced clean, noise-free sound! Incidentally, DAB+ has a 7 seconds delay compared to the same AM station. And the winner is: Bush Heritage DAB+/FM/ Bluetooth Radio Great sound Overall the modern Bush sound and tone is better than large transistor radios of bygone days and the best sound of all the portables we tested. Not hi-fi, but pleasant and room-filling volume, with a useful tone control. The headphone out and line-out are also handy features. The fixed level line-out is stereo, via a 3.5mm socket. Tested on a hi-fi system, it performed well, as it did using good headphones via the headphone output. Case and batteries The case is sturdy, with a strong handle - very important, as many similar vintage transistor radio handles have broken over the years. Unfortunately thereare no instructions on how to remove the rear cover to install the C size batteries. The small stickers which give a clue won’t stay in place forever and are easily hidden by the handle. Most would expect to undo the main screw on the rear with a five cent piece, then prise the cover off. However that would damage it. The method is to press hard on the two stickers, whilst pushing toward the base, so the rear cover slides off. Tip: Use rechargeable batteries, as all batteries leak, despite claims to the contrary, yet we haven’t seen a good brand rechargeable battery leak. It’s best to turn off the radio at the mains when not in use, as it has the mains on full-time and the on-off only switches the low voltage. Overall highly recommended. Features DAB+/FM/AM/LW, 2 watts RMS output, tone control, LCD display, DAB+ Auto Tune, headphone out, line out, telescopic antenna, Dimensions: 35cm L x 28 H x 10.5cm deep (with aerial). Size: 360 x 110 x 235mm (w x d x h) Pros: Style, quality, features, AM included, tone control, outstanding value, line out, 2W RMS. Cons: Rear cover tricky to remove, the FM aerial retaining clip may break – a common problem in vintage radios too. Price: $99 - occasionally less. Overall Rating: 9 out of 10 Bush Heritage mantel model is based on a 1958 radio and packs a punch. Bluetooth is excellent and the Heritage is priced at $269. It’s the only radio tested that has excellent tone on DAB+, the EQ tone-settings ensure the sound is far and away better than all others here – clearly the winner in this round-up. The extra features we would like are AM, plus loudspeaker out, then this radio would rock a room even more. A redesign of the 1958 traditional high-end radio, the Heritage is easily the winner of our line-up for sound quality and features. Brought up to date with Digital Radio and Bluetooth Wireless Audio Streaming, this radio will be a hit with modern-tech /Retro lovers. High Quality Sound Bush claims 10 watts RMS stereo, suffice to say the sound is ample for living rooms, with more bass than all other compact radios. The Heritage also qualifies as the only radio tested that has great tone on DAB+. Features: Large LCD Display, metal grille with wood finish surround, AC power (only), even the soft rubber feet are a nice touch. DRC (Dynamic Range Control) enables setting compression of stations to eliminate the differences in sound level between radio stations. A stand-out feature is the EQ settings which are absolutely brilliant. The sound is so full of tone, you’ll rarely need the EQ though. The manual is the best and well worth a read, as there are many more features than mentioned here (see our links). Size: 320 x 150 x 170mm (w x d x h) Pros: Style, quality, excellent tone, EQ, features, understated looks with easy to use controls, Cons: quite expensive (but worth it!). Suggested improvements: Speaker output sockets. Source: JB Hifi, Dick Smith, Harvey Norman and The Good Guys. Price: $249. Overall Rating: 10 out of 10 OVERLEAF: A more in-depth look at one of the more unusual receivers in this roundup, a four valve hybrid from Tesslor. For those who love the “valve sound” this may bring back some fond memories. It’s strictly AM/FM only (it doesn’t offer DAB+) but it does have one throwback from yesteryear: a “magic eye” tuning indicator! siliconchip.com.au March 2014  23 The Tesslor R601 Valve Radio The only valve retro radio tested, the Tesslor R601 is a hybrid, designed and built in China. Intentionally looking very similar to the AWA Radiolette 500M of 1946-1947, it’s in a very sturdy Bakelite-look case. This impressive exterior is actually very thick moulded MDF, likely to survive at least as long as Bakelite. The radio’s solid-state section is the RF/IF circuit. First stages of audio are a 6F2 Triode/Pentode with the pentode acting as the first stage, then two 6P1 valves in the push-pull output, plus a 6E2 magic eye. Sturdy case With a true “old-style” look, it’s very strong and well finished. It closely resembles a deep burgundy, almost black Bakelite finish. Some owners complain of a strong varnish smell when the new case is heated by the valves, which should diminish in time. Features The LED dial lights illuminate brightly, without melting the station-dial, as often happens in vintage radios with hot incandescent globes. Reception is AM/FM and there’s line-in for external audio devices like a turntable (not RIAA corrected but adjusting the tone, or an LC compensation network in series will suffice). Or connect CD and portable music players like iPod via the portable music player’s speaker out socket. One of the best features is the vernier dial tuning, so the tuning knob is geared to rotate further than the main shaft for fine and accurate tuning adjustment.   AM and FM reception with the built-in internal aerials is very good in a suburban location, or add the supplied external aerials for near-DX reception. Tip: you need to switch the int/ext aerial changeover switch on the rear panel. There’s a small amount of frequency drift in the solid-state tuner after a while, possibly due to the internal heat. The Tesslor R601 four-valve AM/FM hybrid in an MDF cabinet, stained and varnished to look exactly like Bakelite. Note the AWA-style design and the illuminated tuning dial, superbly illuminated by cool-running LEDs, an outstanding feature. But the cool running is countered by the valves, which heat the radio excessively – the air temperature at the rear vent is 65°C! The magic eye tuning indicator is unfortunately swamped in good signal areas. This year the larger Stereo Tesslor R601S AM/FM Radio with Bluetooth 3.0 streaming should be available. and a dual bass/treble pot would be a great inclusion. Headphone output Headphones connect to the rear 3.5mm socket. Fortunately most owners won’t use this feature, as the sound has highly suppressed treble – all bass, most likely due to a large resistor in series with the low impedance speaker line. An audio-filtering LC network in series, or a reversed mini speaker transformer would greatly improve headphone performance. Also the radio’s output appears to be switched between the speaker and headphones though the small 3.5mm socket contacts, normal in a small radio, but not great for 5 to 7 watts RMS. Size: 300 x 180 x 200mm (w x d x h) Pros: Nostalgic sturdy AWA style case, well presented mellow sound on old tunes, higher than average receiver performance, excellent dial - bright, clear and cool, vernier tuning, good value, line audio in and out. Cons: Runs too hot, sibilants, distortion, speaker quality. Source: Only available on the web www. giftsngadgets.com.au Price: About $195.00 The Australian price is less than overseas and it arrived well-packed. It was excellent to find the valves held in place with springloaded top clips. SC Overall Rating: 7 out of 10 Technical Claimed output is 7W into 4 ohms, however the speaker in the unit tested was 8 ohms. Despite the push-pull output, it appears to be nearer to 4-5W RMS, with more than 10% distortion on higher volumes. The speaker was stamped 5 watts, which inevitably means 5W peak, so considering the output volume and clarity is highly dependent on the speaker, it would be interesting to try different speakers to find the best match. You could try an L-C negative feedback tool 24  Silicon Chip Inside the Tesslor, (left) showing three of the four valves - the fourth is the magic eye. Note the valves are surrounded by a plastic “cage” to retain and direct the valve’s heat in this small area. The right photo shows the solid-state RF/IF board behind the front tuning dial and the 8 ohm speaker. A quality build. siliconchip.com.au