On the subject of audio quality; Back in the 80's, I had a Realistic TM800B which I modified (I replaced the entire analogue output stage, including an active MPX filter). I was living in South Africa at the time, and some of the transmissions were exceptionally good quality. I think I still have some off air recordings somewhere.
Moving on a few years and now living in the UK - the only decent FM transmissions are from the BBC, and even those can vary according to time of day / DJ on duty (presumably due to different studios?). I remember during Covid, Ken Bruce was broadcasting from his home studio, and the spoken voice quality was noticeably poor - the music was no different, as I guess he was triggering playback directly from the studio.
With regard to DAB (UK); This was a hugely missed opportunity to provide quality transmissions. In the race to adopt DAB the UK initially adopted DAB (not DAB+) which meant the full quality could never be realised - however I remember in the early 2000's some DAB transmissions were actually ok in terms of audio quality, but sadly as the multplexes filled up with stations, the quality fell off a cliff, with many transmitting at 32k (mono) rates. DAB+ has done little to improve things, as the multiplexes are still overcrowded. Quantity over quality.
Sadly, the same thing has happened with digital television. We have a paucity of free public channels on HD, the rest are SD and most are heavily pixelated or simply just very noisy. I guess this is all down to cost (greed!) unfortunately.
Putting a Radio Shack tuner into the upper echelon of FM tuners:
Copyright ©2001-2022 Tuner Information Center. Permission is hereby granted to quote our text so long as proper credit is given.
Realistic TM-1001
Our contributor Paul Baptista chimes in with mods to an inexpensive and underrated tuner: "My first eBay experience was the purchase of a Realistic TM-1001 tuner. Why this tuner? I was looking for an analog tuner that I could afford that had the following features: signal-strength meter, multipath meter, wide and narrow bandwidth settings and, of course, analog tuning dial. The only one that popped up was this model. I used the unit with the skinny 300-ohm dipole nailed to the frame of the window. I was finally getting decent FM stereo reception and enjoying some surprisingly good sound quality from a few FM stations that don't modify the music signal too much before they transmit it. But itchy fingers I have, so soon I began thinking about which mods I could do with my soldering iron and voltmeter. RF/IF and filter mods are out of the question without the tools and knowledge. My first obstacle was finding the service manual or schematic for this model. I searched high and wide and finally found a generous soul on the Internet who had painstakingly redrawn the schematic a few years ago and sent me a copy of the file. (I do mean redrawn, in the sense of creating capacitors and resistors from multiple line segments in a drawing tool, since he didn't have access to a schematic capture tool that had a pre-drawn resistor or cap or diode.)
Here is a list of all the modifications I executed. The impact to the sound is described at the end. Many thanks to the
FMtuners group and to the TIC web site (I mean the folks of course) for ideas, suggestions, advice and pointers.
1. Inserted rubber grommets between the AC power transformer and the metal chassis.
2. Replaced skinny two-prong power cord with a generic three-conductor power cord. Each conductor is 18 AWG. The third conductor was connected to the chassis at the ground point of R851 near the AC plug.
3. Completely removed the small PCB #0063C that contained the parts for the variable output jacks, R352, R531, VR351a and VR351b, and the two shiny metal RCA jacks and a potentiometer. The output is now fixed level only and is pickoff from stubs at point 46 and point 45 via coax cable using the center conductor of two runs of 22AWG RG-59/U coax. Two new gold plated RCA jacks are panel mounted but isolated from the panel. The RCA jack grounds are tied together and then grounded to the circuit ground at stub #54 via a 22AWG insulated wire.
4. Disconnected the 75-ohm antenna skinny wire input from the circuit since currently I only have a 300-ohm antenna. Soon I'll do the reverse and remove the 300-ohm input from the circuit and move to 75-ohm input instead. Once I get an antenna that allows this. I'll install an F-connector in the hole in the panel left empty by removing the variable output pot (see mod #3 above).
5. Replaced the four hard plastic feet with four soft rubber feet. Made the feet myself from soft rubber discs. Used the original mounting screws.
6. Cleaned out tuning cap, lubricated tuning knob axial and dial cord spindles.
7. Cleaned and polished the aluminium faceplate.
8. Cleaned and polished the walnut veneer exterior.
9. Cleaned the plexiglass display window on both sides and the background frequency numbers and polished the frequency pointer.
10. Taped around the lamps that light up the signal-strength and multipath meters to focus all light to the meters to prevent light from being scattered into the main display window.
11. Changed C223 (22 µF/25V) to a 47 µF Black Gate Std radial.
12. Changed C303 (10 µF/25V) to a 22 µF Black Gate Std radial. C303 and C223 are back to back between pin 2 of LA3350 and pin 6 of HA1137.
13. Changed C316 (0.1 µF/50V) to Solen Fast Cap PPE Series 0.47 µF, physically hard to fit an axial cap here but I managed.
14. Changed C317 (0.1 µF/50V), same as C316. C315 & C316 sit just after the low-pass filters and just before the output transistors.
15. Changed C320 (1 µF/50V) to Solen Fast Cap PPE Series, 1 µF, again an axial of this size is tricky but workable with care.
16. Changed C321 (1 µF/50V), same as C320. C320 & C321 are the last caps before the output jacks.
17. Changed C305 (1 µF/50V) to Solen Fast Cap PPE Series, 1 µF. Here this cap is next to impossible to fit. Good luck! Be creative or find a small cap.
18. Changed C306 (1 µF/50V). Same as C305. C305 & C306 are just before the low pass filters.
19. Changed the bypass cap in the MPX area C302 (1 µF/50v) to a Nichicon Low Impedance Alum Electrolytic 47 µF/63V and further bypassed it with a 0.1 µF/63V Vishay MKT 1826 Series Metallized Polyester Film cap. The Vishay is a tiny flat square cap so it fit on the underside of the PCB.
20. Changed C422 (47 µF/16V) to Nichicon Low Impedance Alum Electrolytic 470 µF/63V.
21. Changed the power supply cap C802 (1000 µF/25V) to Nichicon Low Impedance Alum Electrolytic 2200 µF/63V.
22. Changed the power supply cap C803 (220 µF/25V) to Nichicon Low Impedance Alum Electrolytic 470 µF/63V.
23. Regarding the power supply cap C810 (47 µF/16V) - note that on the schematic C810 and C811 are actually the reverse of what is in the tuner (human error on the schematic diagram). I replaced it with Nichicon Low Impedance Alum Electrolytic 100 µF/63V.
24. The power supply cap C811 (220 µF/16V), see note in #23. Replaced with Nichicon Low Impedance Alum Electrolytic 470 µF/63V.
That's it for now. I would love to get it RF/IF aligned and maybe pop in narrower filters in narrow mode, but I would like get someone in the Montreal area to do it to avoid the shipping costs. I don't want this 4-gang tuner's cost to climb much higher.
What is the result of all this? First off, it provided several hours of relaxing leisure activities... a great hobby especially during the winter months. Second, the unit's total cost is now around $140 CAD, so it's still under $100 USD. And third, much better sound quality. Since I didn't listen to the unit after each mod, I can't say which mods had most impact or less impact. What I can say is this: using the same antenna setup and the unit in the same position, the FM stereo image is wider now. It seems to go beyond the physical position of my loudspeakers. Human voices sound more natural and less "through a tunnel" or nasal. The bass is deeper, or at least more present. The midrange is very enjoyable. Overall it sounds much better - a "night and day" type of difference. Now I can only imagine what it would sound like using an outdoor FM antenna and after a proper RF/IF alignment.
Note: wife-to-be [now wife - Editor] acceptance factor, I quote: "It sounds very good. You will buy something modern, right? A black unit? That wooden box just doesn't look like it is a serious home stereo system for someone who likes audio as much as you do." If only she knew that the valve amp project I'm preparing is going to bring more wood chassis onto the rack and remove the machined aluminium amp that is there now....