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AMP-4

Joseph K7CBR #81460 Mr. Rob... Can you please remind me what the low frequency attenuation was for your AMP-4? Thanks! Joseph On Wednesday, January 1, 2025 at 12:59:27 PM EST, Rob Sherwood via groups.io <rob@...> wrote: My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz.? Personal choice.? Rob, NC0B > On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote: > > ?
Rob Sherwood All Messages By This Member #81467 开云体育 Hi Joseph, ? Initially I duplicated the low frequency roll-off of the stock amp, but later changed the input roll-off to be minimal.? I see a typo in the attached schematic. The output coupling electrolytic C1 should say 330 uF not us.? That is likely the dominant cause of low frequency roll-off. ?The 330 uF could be increased to 470 uF or even 1000 uF, but I don’t know whether an MS-4 speaker would produce any additional low frequency audio.? Headphones would be a different matter.? I doubt there is any need to increase C2 in the feedback circuit, but I have never experimented with trying to extend the low end.? ? I happen to use Icom SP-20 speakers on all my rigs, and while it reproduces 150 Hz quite well, it is really falling off at 100 Hz. ? Rob, NC0B ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of Joseph K7CBR via groups.io Sent: Wednesday, January 01, 2025 11:32 AM To: [email protected] Subject: [DRAKE-RADIO] AMP-4 ? Mr. Rob... Can you please remind me what the low frequency attenuation was for your AMP-4? Thanks! ? Joseph ? On Wednesday, January 1, 2025 at 12:59:27 PM EST, Rob Sherwood via groups.io <rob@...> wrote: ? ? My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz.? Personal choice.? Rob, NC0B > On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote: > > ? AMP_4 ver P.pdf AMP_4 ver P.pdf
Joseph K7CBR #81476 Thank you for that info! You are 100% right about the MS-4 in stock form (its fidelity is pitiful though). I am more of an SWL type person, which is what motivated me to make changes to the MS-4. A less efficient speaker (larger voice coil and magnet) yet with a much better low, mid, and high range response, coupled with about 11 watts RMS of power, and changes to the cabinet making it masquerade as more of a tuned enclosure really made a drastic difference. Incidentally, the MS-4 easily goes below 100Hz now, and at times if I tune across some "hifi" hams, they are so overcompensating for the lack of response in everyone else's system, it makes my R4C about jump off the speaker with low frequency rumble. That is NOT a criticism of the hifi guys at all, just an empirical observation. Some of them sound like wide FM using the C-line, as those changes coupled with Frank's 2.8 filter really get it done. If you have any solid ideas for changes in the noise blanker for the R4C I would listen. Its OK yet still is very limited. CHEERS! Joseph On Wednesday, January 1, 2025 at 03:36:36 PM EST, Rob Sherwood via groups.io <rob@...> wrote: Hi Joseph, ? Initially I duplicated the low frequency roll-off of the stock amp, but later changed the input roll-off to be minimal.? I see a typo in the attached schematic. The output coupling electrolytic C1 should say 330 uF not us.? That is likely the dominant cause of low frequency roll-off. ?The 330 uF could be increased to 470 uF or even 1000 uF, but I don’t know whether an MS-4 speaker would produce any additional low frequency audio.? Headphones would be a different matter.? I doubt there is any need to increase C2 in the feedback circuit, but I have never experimented with trying to extend the low end.? ? I happen to use Icom SP-20 speakers on all my rigs, and while it reproduces 150 Hz quite well, it is really falling off at 100 Hz. ? Rob, NC0B ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of Joseph K7CBR via groups.io Sent: Wednesday, January 01, 2025 11:32 AM To: [email protected] Subject: [DRAKE-RADIO] AMP-4 ? Mr. Rob... Can you please remind me what the low frequency attenuation was for your AMP-4? Thanks! ? Joseph ? On Wednesday, January 1, 2025 at 12:59:27 PM EST, Rob Sherwood via groups.io <rob@...> wrote: ? ? My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz.? Personal choice.? Rob, NC0B > On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote: > > ?

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