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Interest in balanced line receiver boards

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alexcp

alexcp

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Joined 2009
hifiocean.com
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#1
UPDATE: This GB is now closed. The boards were manufactured and are being shipped to the participants.

Earlier this year, I created a thread about a balanced line receiver board:
balanced line receiver photo small.png
Since there have been some questions on the availability of these boards. I am starting this group buy to see if there is enough interest to warrant a manufacturing run.

What it is
  • One 68x28mm (approx. 2.7x1.1in) all-through-hole board implements one channel of high performance balanced line receiver.
  • The use case for this board and its theory of operation are discussed at some length in the main thread.
Features and benefits
  • Low distortion. The board allows using modern opamps (e.g. the LM4562) and has much better distortion performance, both measurably and audibly, compared to most integrated balanced line receivers (e.g. THAT1200 series).
  • DC blocking. The board includes an active DC blocking filter, making any coupling capacitors unnecessary.
  • Choice of balanced or ground sensing output. The output can be configured as balanced or as remote ground sensing.
    • The balanced output option is useful if your downstream device has a balanced input. (Note that balanced means equal hot and cold output impedances. Only the hot wire is actively driven, so you won't be able to drive two amplifiers BTL fashion).
    • The ground sensing option is useful for downstream amplifiers with single ended inputs. Configured for ground sensing, this board corrects for the difference between its own ground and that of the downstream amplifier, making sure that the latter sees the correct signal at its input. The details are discussed in the beginning of the above mentioned thread.
  • Choice of gain. The default gain is 0dB (unity), however, the gain is set by discrete resistors, and any reasonable gain can be chosen.
  • Good CMRR even at higher frequencies thanks to an advanced PCB layout. Typical CMRR is better than 50dB with 1% resistors and better than 70dB with 0.1% resistors.
Pricing
  • Will depend on the level of interest, starting with $5 for one board (one board = one channel, two are needed for stereo) plus shipping. Should the total number of boards exceed 50, the price will go down.
  • Shipping is flat $5 for the continental U.S. (USPS Ground Advantage) and $15 elsewhere (USPS First Class International Package). Should you want to buy something else from me, I of course can combine shipping.
Build and other technical details
  • The schematic and the board outline are published in the main thread.
  • The board uses compact axial metal film resistors, such as Vishay CMF50/RN50 or SFR16S, Yageo MFR12, KOA Speer MFS, etc.
  • Other components are very ordinary and allow broad substitution. Since the board is through-hole, one can socket the opamps and try opamp rolling.
  • Full BOM and assembly instructions will be provided.
If interested in purchasing any of these boards, please reply to this thread. Copy this sentence along with everything below into your post and add your own line as follows:

(1) Your name here on diyAudio -- (2) number of board, pieces -- (3) Country to ship the board(s) to.

Try to preserve formatting.

Running List for Subscription :

alexcp -- 2 -- US

This group buy will close on Saturday, September 30. Be sure to sign up before then.
 
Last edited:
#8
How much gain could be set before noise and distortion rise appreciably? Also, would it be practicable to have a potentiometer or stepped attenuator "remotely" control the gain on multiple boards at the same time, i.e. to produce a multi-channel volume control?
 
#10
454Casull said:
How much gain could be set before noise and distortion rise appreciably?
Click to expand...
How much gain would you need, and what is the intended application? The board is designed to handle line level signals. If you want to amplify low level signals as in a phono stage, you'd better add gain to the first stage.
454Casull said:
"remotely" control the gain on multiple boards at the same time, i.e. to produce a multi-channel volume control
Click to expand...
While this board is just a balanced line receiver with no provision for volume controls, my other boards do have built-in volume control.
 
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