Drake 2A enhancements

[Ed WA4NJY]

I have been using a Drake 2A along with the Valiant II for AM.  The more I use it, the more I like it on AM.  A bit restricted at 4.8kc but with an 8 inch speaker, not bad. Noise limiter is a big help.

How much benefit would there be in tapping the detector and feeding a somewhat hi-fi external audio amp?

Any input on other mods would be appreciated. 

Thanks,
Ed WA4NJY
Bradenton, Fl

[W3GMS]

Hi Ed,

I have used your proposal for many years with good success.  Keep in mind, you can't get something for nothing however.  I would suggest going in one stage and pulling off your audio across the AF gain control.  Use the ground side and the top side.  Some detectors don't like additional loading on them so this buffer approach works well.  The limitations on the Drake 2A on AM will be the limited IF bandwidth.  As you mentioned its 4.8 KHz so that will limit your high frequency response of your audio system.  Normally I like to listen to AM with either a 6 or 8 KHz IF bandwidth.  What you can do with your external audio amp is do some audio "tilting" of the response curve which you can't do now.  You may actually notice an improvement by cutting some low end out of overly "bassy" signals.  That will give the overall impression that the received signals has more articulation or more highs when it actually doesn't.  So you can in essence play with the ratios of the audio distribution and often times come up with something that is more pleasing to the ear. 

Have fun! 

Joe, W3GMS   

[Ed WA4NJY]

Thanks, Joe. As of now I am using the 2A into a MS-7 speaker and it really does surprisingly well with the noisy conditions, etc.  When the bands are quieter, the fidelity of the external amp should be fun.


73,
Ed

[WQ9E]

I am not sure the 2-A will ever rank in the high fidelity AM class because I believe Drake was focused more upon CW/SSB.   This was the followup to the 1-A which didn't even have a separate AM detector.  The 2-A widens its bandwidth by somewhat "crippling" the passband tuner/filter.   The result, at least according to a fellow collector who swept his after alignment, was a fairly irregular frequency response in the wide position.

I have a 2-A and 2-B and the 2-B, which has a narrower wide position (3.6 Khz)  but uses all of the passband filter sections instead of switching  2 out like the 2-A, has a much smoother sound on AM to me. 

[KM1H]

All around the 2B is superior, the A model didnt last very long due to owner complaints.

Carl

[AB2EZ]

When I had a 2B in the shack (and I think this will work the same with a 2A) I did the following. You might find this to be a fun thing to try:

1. I picked up the 455kHz output from the Q-multiplier socket on the back.
2. I ran this through an LM386 -type op amp, and then through a tiny 455kHz center frequency. 10kHz wide (3dB points). 4-pole crystal filter; which I purchased new for around $10.00. The crystal filter was needed to remove strong, out-of-band local oscillator signals that exist at the Q-multiplier output of the receiver. The op-amp was set up to present a 1000 ohm output impedance to match the specified input impedance of the crystal filter.
3. The output of the crystal filter was put through a second LM386 -type op-amp to provide a signal that could easily drive a 50 ohm load. The second op-amp was set up to present a 1000 ohm input impedance to match the specified output impedance of the crystal filter.
4. You can use that output to drive an AM demodulator of your choice (e.g, a 1N34 diode and a capacitor). I used it to drive a Soft Rock-type board in combination with my computer [21st century adjustable digital filters, AM and synchronous AM, spectral display, etc. in combination with a 1950's Drake 2A receiver]

All of the parts in 2 and 3, above will fit on a tiny prototyping board

It worked great. I still have the interface board containing the parts in 2 and 3, above.

Stu

[W3GMS]

All good suggestions but keep in mind some guys just want somewhat of improvement over the small built in speaker with its associated audio amp.  

Ed, hook up your external amp and if it fills the need your looking for then your done!  If not then you may want to explore some of the other choices .  

Joe, W3GMS

[W4AAB]

The Drake 2-A came out in 1960( the 1-A came out in 1958). I liked the 2-A because it had 4.8 kHz bandwidth on wide, as opposed to the 3.6 kHz of the 2-B. I ahted to trade mine, but had too many receivers.