FAQ
TL;DR: Use a Class 2 Bluetooth audio module (range typically exceeds 20 m) and inject at the radio’s pre‑amp; “what you need is a Bluetooth Class 2 module with Audio capability.” [Elektroda, Mark Harrington, post #21666074]
Why it matters:** This FAQ helps hobbyists add Bluetooth to 1940s tube radios safely while preserving reversibility and sound quality.
Quick Facts
- Power: Module needs approx. 4.5–5 V DC; many CSR BlueCore5 boards include on‑board codec. [Elektroda, Mark Harrington, post #21666074]
- Profiles: A2DP/AVRCP with SBC, MP3, AAC, aptX supported on suggested module. [Elektroda, Mark Harrington, post #21666074]
- Typical range: Class 2 radio “exceeds 20 m”; internal or external antenna options vary by board. [Elektroda, Mark Harrington, post #21666074]
- Input safety: Add a 10 µF, 50 V DC coupling capacitor and shielded leads to reduce hum. [Elektroda, Mark Harrington, post #21666082]
- Shock hazard: Verify chassis-to-Bluetooth ground with a DVM on ≥250 V range before connecting. [Elektroda, Mark Harrington, post #21666086]
Can I add Bluetooth to a 1940s tube radio without ruining it?
Yes. Treat the radio as a collectible and make changes reversible. Add Bluetooth as an auxiliary input and avoid cutting original parts. An expert advised professional, reversible installation for vintage sets to protect value and safety. [Elektroda, Earl Albin, post #21666075]
Where do I inject the Bluetooth audio signal?
Identify the audio pre‑amp tube stage from the schematic and feed the Bluetooth line‑level there. Old sets often include a pasted schematic; otherwise, find one online and list the tubes to locate the pre‑amp. This avoids disturbing RF sections. [Elektroda, Earl Albin, post #21666073]
Which Bluetooth audio module is recommended for this project?
Builders in the thread favored the KC Wirefree KC6112 as “the best of the lot” for A2DP/AVRCP use. It offers suitable profiles and integrates well when powered correctly and shielded. Choose modules that match these capabilities. [Elektroda, Mark Harrington, post #21666091]
What supply voltage does the module need?
Use approx. 4.5–5 V DC as specified for the recommended CSR BlueCore5‑based boards. Provide a clean, well‑decoupled supply to prevent noise. Avoid taking power from unisolated points inside hot‑chassis sets. [Elektroda, Mark Harrington, post #21666074]
How do I use the SW/MW band switch as an input selector?
Wire the switch to select radio front end or the Bluetooth input. Add shielding and a DC‑blocking coupling capacitor on the Bluetooth line to minimize hum when switching. Label positions clearly for safe operation. [Elektroda, Mark Harrington, post #21666082]
Is Bluetooth audio quality good enough on a tube radio?
Expect limits. Vintage radios lack flat 20 Hz–20 kHz response, and lossy codecs can reduce fidelity. As one expert put it, “these old radio/audio devices don’t have a flat 20HZ to 20KHz frequency response.” Use it for convenience, not hi‑fi benchmarks. [Elektroda, Earl Albin, post #21666081]
What range should I expect from a Class 2 Bluetooth receiver?
Typical Class 2 implementations on the cited module exceed 20 m under favorable conditions. Enclosures, placement, and antennas affect real‑world reach. Maintain clear line‑of‑sight when possible to reduce dropouts. [Elektroda, Mark Harrington, post #21666074]
How do I reduce 60 Hz hum and noise after adding Bluetooth?
Shield the Bluetooth board and leads, use a proper ground reference, and insert a 10 µF, 50 V coupling capacitor at the input. Keep audio wiring short and away from mains paths to reject hum in older sets. [Elektroda, Mark Harrington, post #21666082]
What safety checks must I perform before first power‑up?
Measure chassis to Bluetooth ground potential with a DVM set to at least 250 V. Confirm isolation and absence of half‑mains conditions before connecting. Skipping this can cause shocks or a destructive arc. [Elektroda, Mark Harrington, post #21666086]
Do I really need the schematic and tube list?
Yes. Start with the schematic to locate the audio pre‑amp and volume control. Document the tube lineup to confirm stages. This prevents damage to irreplaceable parts and guides a clean, reversible input path. [Elektroda, Earl Albin, post #21666073]
Quick 3‑step: how do I add Bluetooth input cleanly?
- Mount the Bluetooth board and shield its enclosure and leads.
- Add a switch to choose radio or external input via the band switch path.
- Insert a 10 µF, 50 V coupling capacitor to the pre‑amp input, then test.
[Elektroda, Mark Harrington, post #21666082]
What are A2DP and AVRCP in plain English?
A2DP is the profile that streams stereo audio with codecs like SBC, MP3, AAC, and aptX. AVRCP enables play/pause and track controls between your phone and the module. The suggested module supports both profiles. [Elektroda, Mark Harrington, post #21666074]
Any edge cases I should know before streaming?
Hot‑chassis or leaky capacitors can place the radio at hazardous potential. A miswired ground can produce a loud bang, sparks, or injury. Verify isolation and voltages first to avoid failure on power‑up. [Elektroda, Mark Harrington, post #21666086]
Can the band‑switch mod be undone later?
Yes. Use existing switch poles and add wiring that you can remove without drilling the cabinet. Experts recommend reversible work to preserve collector value and future restoration options. [Elektroda, Earl Albin, post #21666075]
Where can I source the modules mentioned?
The thread cites KC Wirefree as a helpful supplier for A2DP/AVRCP modules. Contact the vendor for the KC6112 or similar boards and firmware support before you buy. [Elektroda, Mark Harrington, post #21666086]
My set label says 230 V, 60 W—anything special to note?
That rating reflects the OP’s radio. If you’re in a 120 V region, you’ll need appropriate step‑up transformation and safe isolation. Confirm mains configuration before powering any added electronics. [Elektroda, Callum Cattle, post #21666072]
