BC-610 E Speech Amp

[germanyg]

I would like to replace my speech amp any ideas ?

[N8ETQ]

I would like to replace my speech amp any ideas ?

Hi,

  Any amp should do. I guess there is no way to make a
"Logical" suggestion without just a little more info.

Such As:

   Are you using this with a BC-610-E or later model?

   Do you have other provisions for monitoring Modulator
   current?

   Do you NOT need CW sidetone?

   Do you NOT use Carbon Mics?

 There was a writeup in ER last couple of issues or so
where someone just took an old HiFi stereo RX and made
a speech amp out of it.  The SCR-299, 399 and 499 are
real nice sets when complete. They have all the "Features"
of any Yeacomwood untill you need to QSY.

73 es welcome to the group!

/Dan
   

[germanyg]

I would like to replace my speech amp any ideas ?

Hi,

  Any amp should do. I guess there is no way to make a
"Logical" suggestion without just a little more info.

Such As:

   Are you using this with a BC-610-E or later model?

   Do you have other provisions for monitoring Modulator
   current?

   Do you NOT need CW sidetone?

   Do you NOT use Carbon Mics?

 There was a writeup in ER last couple of issues or so
where someone just took an old HiFi stereo RX and made
a speech amp out of it.  The SCR-299, 399 and 499 are
real nice sets when complete. They have all the "Features"
of any Yeacomwood untill you need to QSY.

73 es welcome to the group!

/Dan
   

Thanks will check ER

[k4kyv]

Anything with a 500/600 ohm balanced audio output should do the job.  I believe the audio level has to be on the order of +18 dB (1dB=6mw). The line input transformer in the 610 feeds the push-pull 2A3 grids directly.

The stock BC-614 can be modified to sound very good.  It is inherently a pretty good unit once you get away from the carbon mic. The stock input transformer might be made to work with a low-Z dynamic or condenser mic if the mic output is high enough.  An "amplified" D-104 should have plenty of output too. Just disconnect the DC voltage intended for the carbon mic.

[WB4AIO]

I would like to replace my speech amp any ideas ?

Years ago, I did this for my BC-610E:

I rack-mounted an old tube-type high fidelity amplifier that used a pair of EL34s in the output stage. I mounted a mod plate current meter and the gain control pot on the front panel. I unbypassed the cathode resistor in the second stage of the hi-fi amp and connected the top of the resistor to an R/C voltage divider tapped off the secondary of the BC-610's modulation transformer for negative feedback. I adjusted the divider for about 10 dB gain reduction.

I fed the 16 ohm tap of the hi-fi amp to a balanced line and then into the 16 ohm tap on a UTC linear standard hi-fi output transformer which I mounted in the 610, the hi-z side of which fed the grids of the 100TH modulators. Across the 16-ohm line I placed a 33 ohm resistor to limit impedance excursions seen by the amp.

Obviously, I didn't use the 2A3 drivers or the associated driver transformer at all.

I used a Heathkit tube-type cathode follower preamp/tone control fed into an AM-864U peak limiter, and the peak limiter drove the input of the hi-fi amp.

Here's a little more info:

http://3950.net/2010/02/the-am-864u-broadcast-limiter/

Maybe this will give you some ideas.

All the best,


Kevin, WB4AIO.