I wasn't talking about you, you're open minded.
edit_____
btw, plate modulation isn't a requirement and is actually dirty :laugh:
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Hi-Fidelity / Lo-Finance
- Thread starter kaosfm
- Start date
I wasn't talking about you, you're open minded.
edit_____
btw, plate modulation isn't a requirement and is actually dirty :laugh:
Cobra 29LTD with the TA7222AP audio chip
Receive:
Change C33 and C40 to 2.2uF non-polarized electrolytic
More highs?: remove C204 (some year ranges don't have this cap)
Transmit:
Change C69 to a .001uF disc
Change C68 to a 1uF Tantalum (some radio's already have a 1uF in them)
Change C37 to a .068uF mylar (or parallel a second .033uF mylar with the existing one)
New 2010/2011 Cobra 29LTD (TDA2003 audio chip)
Receive:
Remove C170
Change C33 and C40 to 2.2uF non-polarized electrolytics
Transmit:
Change C68 to a 1.5uF tantalum with the + side towards the right side of the radio.
Change C69 and C125 to .001uF disc
Change C37 and C43 to .1uF mylar
I did this mod on my 29lx and the receive is awesome. Crystal clear with less static sound. If you can't find non polarized electrolytics you can do what I did which is take two 4.7uf and tie the neg leads togeather and use the pos leads for through hole. Two 4.7uf caps in this fashion gives you 2.4uf give or take. The only part I didnt do was remove c170 which I can not find in the lx. But transmit has gotten great reports compared to the stock setup. I also did the irf 520 mosfet mod which gives the lx roughly 30 watts pep. Hell of a nice radio.
Cobra 25LTD Classic (TA7222AP)
Receive:
Change C32 (front center of PC board) to a 2.2uF mylar or NP electrolytic
Change C54 and C56 to 2.2uF NP electrolytic
Change C67 to a 1000uF 25 volt electrolytic
more highs? Change C151 to a .001uF disc or mylar
Transmit:
Change C90 to a 1.5uF 16-50 volt tantalum observe polarity.
Change C96 to a .001uF disc or mylar
Change C89 to a .033uF (333) green mylar
From Goldfinger:
I almost always use a mylar or polypropylene for C32. The signal levels are low there so using a high fidelity cap is a noticeable upgrade.
C54 and C56 are in a higher level area of the chain so the small/handy radial lead non-polar's are fine.
All mylar's is also fine if you can squeeze them in!
Receive:
Change C33 and C40 to 2.2uF non-polarized electrolytic
More highs?: remove C204 (some year ranges don't have this cap)
Transmit:
Change C69 to a .001uF disc
Change C68 to a 1uF Tantalum (some radio's already have a 1uF in them)
Change C37 to a .068uF mylar (or parallel a second .033uF mylar with the existing one)
New 2010/2011 Cobra 29LTD (TDA2003 audio chip)
Receive:
Remove C170
Change C33 and C40 to 2.2uF non-polarized electrolytics
Transmit:
Change C68 to a 1.5uF tantalum with the + side towards the right side of the radio.
Change C69 and C125 to .001uF disc
Change C37 and C43 to .1uF mylar
I did this mod on my 29lx and the receive is awesome. Crystal clear with less static sound. If you can't find non polarized electrolytics you can do what I did which is take two 4.7uf and tie the neg leads togeather and use the pos leads for through hole. Two 4.7uf caps in this fashion gives you 2.4uf give or take. The only part I didnt do was remove c170 which I can not find in the lx. But transmit has gotten great reports compared to the stock setup. I also did the irf 520 mosfet mod which gives the lx roughly 30 watts pep. Hell of a nice radio.
Cobra 25LTD Classic (TA7222AP)
Receive:
Change C32 (front center of PC board) to a 2.2uF mylar or NP electrolytic
Change C54 and C56 to 2.2uF NP electrolytic
Change C67 to a 1000uF 25 volt electrolytic
more highs? Change C151 to a .001uF disc or mylar
Transmit:
Change C90 to a 1.5uF 16-50 volt tantalum observe polarity.
Change C96 to a .001uF disc or mylar
Change C89 to a .033uF (333) green mylar
From Goldfinger:
I almost always use a mylar or polypropylene for C32. The signal levels are low there so using a high fidelity cap is a noticeable upgrade.
C54 and C56 are in a higher level area of the chain so the small/handy radial lead non-polar's are fine.
All mylar's is also fine if you can squeeze them in!
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The dates on the TDA2003 audio amp is actually wrong. I just bought a 2008 29ltd for $30 that has the TDA2003 chip.
It was one of those "untested, for parts" auctions and the thing was 100% factory, lol, never been touched.
The trend is to use the 148 because the modulation transformer in the 29 is a bottleneck. But I'm not buying a SSB radio to run AM, so I built the darlington* like the 148 to replace the transformer in a 29, but I didn't like it. I find the transformer passes enough audio to sound good with some cap changes and audio processing.
I said this in another post, but some guys are passing lows so low that it's almost gone the other way from quality audio to a competition. It's not as hard to listen to as the "super trucker", but it leaves me looking for the bass knob.
*that's a Rev Bow mod
It was one of those "untested, for parts" auctions and the thing was 100% factory, lol, never been touched.
The trend is to use the 148 because the modulation transformer in the 29 is a bottleneck. But I'm not buying a SSB radio to run AM, so I built the darlington* like the 148 to replace the transformer in a 29, but I didn't like it. I find the transformer passes enough audio to sound good with some cap changes and audio processing.
I said this in another post, but some guys are passing lows so low that it's almost gone the other way from quality audio to a competition. It's not as hard to listen to as the "super trucker", but it leaves me looking for the bass knob.
*that's a Rev Bow mod
Dirty? How so? Used to run 1 Kw carrier plate modulated to 120% positive peak modulation with about 1% THD as read on a Hewlett-Packard distortion analyzer. Transmitter was a Gates BC1-G however. Frequency was 1350 KHz.
I'm just jerking your chain. I wish I was apart of those old glory days, but fet technology was already taking over when I bought my first radio.
edit___
1kw carrier? That's illegal as hell!
Thanks for all of the prompt replies to the thread thus far. I'm under no illusions about the fact that hardware bottlenecks are in play with this setup. I realize true broadcast grade audio is a pipe dream with this radio. However, there is certainly a significant room for improvement from stock. It's really about maximizing the potential of the original hardware with the main objective of increasing punch and speech intelligibility on dx contacts, both ssb and am. The setup is certainly meeting, if not exceeding those requirements.
One thing I take issue with is the stand many are taking that the hardware audio bandwidth limits are so black and white. I'm not necessarily sold on the idea that the audio filtering in the radio is truly the impenetrable brick wall many claim it to be. If that was indeed the case, I shouldn't be able to detect eq changes that fall outside of the 300-3000hz passband, but I most certainly can. For adjustments at 100, 200 and 6400 hz, I push the eq up right before the point of distortion. The audio improvements are appreciable despite their being outside of the 300-3000hz range.
I think I will go ahead and capture some a/b comparison recordings so that I can look at the audio bandwidth onscreen. I'm eager to find out! I will be sure to share my findings on this thread.
One thing I take issue with is the stand many are taking that the hardware audio bandwidth limits are so black and white. I'm not necessarily sold on the idea that the audio filtering in the radio is truly the impenetrable brick wall many claim it to be. If that was indeed the case, I shouldn't be able to detect eq changes that fall outside of the 300-3000hz passband, but I most certainly can. For adjustments at 100, 200 and 6400 hz, I push the eq up right before the point of distortion. The audio improvements are appreciable despite their being outside of the 300-3000hz range.
I think I will go ahead and capture some a/b comparison recordings so that I can look at the audio bandwidth onscreen. I'm eager to find out! I will be sure to share my findings on this thread.
I figured you were yanking my chain.:tongue: As for legality, take another look at the frequency I was talking about using. 1350 KHz LOL The Gates BC1-G is an old tube type AM broadcast band transmitter used at CKAD transmitter site. Good thing I didn't mention the Nautel 22 Kw FM transmitter. :laugh:
I think you will find that the 300-3000 Hz range is more like 150-4000 or 5000 Hz in those radios. They do not have the tight IF filtering like amateur radios have.
Alright folks...got some updates for you all!
I was really inspired by the various comments and was compelled to hook up the receiver (25LTD Classic) output into the line-in jack of my laptop and take some actual measurements of the audio spectrum in real-time under varying scenarios.
Scenario #1: White Noise
This provides a good baseline of the frequency response of the receiver simply as it picks up white noise from the squelch being all the way open. As you can see, the bulk of the spectrum appears between 119 Hz (marker #1) and 8052 Hz (marker #2). This nice broad response helps explain why I'm able to detect even minute changes to the EQ between 100 Hz and 6800 Hz.
Scenario #2: Unprocessed SRA198 Noise Cancelling Mic
This provides a good depiction of how the radio performs with no processing whatsoever and a stock noise-cancelling mic. You can see that the 2950dx certainly is capable of pushing audio well beyond the pass-band limits of 300-3000 Hz. However, it is certainly more of a "peaky" look in the middle with a more pronounced roll-off on the outer edges.
Scenario #3: Processed w/ Mixer/Compressor/EQ & Pyle Dynamic Mic
Now this is impressive. The bass response picks up dramatically, the outer fringes of the highs are boosted reasonably and the overall response in-between has risen in amplitude and flattened out somewhat; certainly less "peaky" than the prior screen capture with no processing involved. Is it truly "Hi-Fi" broadcast grade AM with 10 Khz bandwidth? Well no, not quite. However, it is certainly far better than the oft-cited "300-3000 Hz" figure that is thrown around frequently. The only down-side is that I can't perform this type of analysis for SSB signals. I don't have a second SSB transceiver to check the receive on. I can only assume that some of these improvements will translate over to SSB mode based purely on reciprocity and positive feedback reports from other operators.
Now if someone really wants to go "all-in" with this Hi-Fi thing, they'll need to find a way to add a C-QUAM AM stereo modulator to their setups! The signals would still be compatible with all of the mono-audio transceivers out there. I doubt it would ever happen, but I would sure as hell love to see someone try! Add-in a 25 Hz pilot tone and we're half way there...
I was really inspired by the various comments and was compelled to hook up the receiver (25LTD Classic) output into the line-in jack of my laptop and take some actual measurements of the audio spectrum in real-time under varying scenarios.
Scenario #1: White Noise
This provides a good baseline of the frequency response of the receiver simply as it picks up white noise from the squelch being all the way open. As you can see, the bulk of the spectrum appears between 119 Hz (marker #1) and 8052 Hz (marker #2). This nice broad response helps explain why I'm able to detect even minute changes to the EQ between 100 Hz and 6800 Hz.
Scenario #2: Unprocessed SRA198 Noise Cancelling Mic
This provides a good depiction of how the radio performs with no processing whatsoever and a stock noise-cancelling mic. You can see that the 2950dx certainly is capable of pushing audio well beyond the pass-band limits of 300-3000 Hz. However, it is certainly more of a "peaky" look in the middle with a more pronounced roll-off on the outer edges.
Scenario #3: Processed w/ Mixer/Compressor/EQ & Pyle Dynamic Mic
Now this is impressive. The bass response picks up dramatically, the outer fringes of the highs are boosted reasonably and the overall response in-between has risen in amplitude and flattened out somewhat; certainly less "peaky" than the prior screen capture with no processing involved. Is it truly "Hi-Fi" broadcast grade AM with 10 Khz bandwidth? Well no, not quite. However, it is certainly far better than the oft-cited "300-3000 Hz" figure that is thrown around frequently. The only down-side is that I can't perform this type of analysis for SSB signals. I don't have a second SSB transceiver to check the receive on. I can only assume that some of these improvements will translate over to SSB mode based purely on reciprocity and positive feedback reports from other operators.
Now if someone really wants to go "all-in" with this Hi-Fi thing, they'll need to find a way to add a C-QUAM AM stereo modulator to their setups! The signals would still be compatible with all of the mono-audio transceivers out there. I doubt it would ever happen, but I would sure as hell love to see someone try! Add-in a 25 Hz pilot tone and we're half way there...
i have nothing to add.i just read thru this thread and feel if you had good results and are happy thats what matters.
i been tossing these same ideas past couple months,and almost ordered a heil mic and another cheapo but decided against it.
i just orered the w2ihy 8 band equalizer myself after aprox 5,000 good things ive read about it.
hopefully it will do what i want,,im easy tho.i have a newer 2995dx now and with the night eagle mic it does more than i expected from it..
i just need some bass to get the tinnyness out on ssb so i figured i will have this eq for the rest of my life and i like buying things from "the lil guy " made in the U.S. of A..
TIME WILL TELL,i got 2 amplified d104,s 1 newer board and one older,and 1 for my d201 tram,non amplified,,a sedelta echo master plus classic" a couple radio shack mics that sound great"dynamic"..and a old cobra ca72 dynamic/ceramic compression styl in good shape inside..and 2 electrets from a 900 mhz bellsouth cordless phone,all to try when the w2ihy eq gets here..just for the fun of it..
i will start a thread so the bashing can continue<More audio>
i been tossing these same ideas past couple months,and almost ordered a heil mic and another cheapo but decided against it.
i just orered the w2ihy 8 band equalizer myself after aprox 5,000 good things ive read about it.
hopefully it will do what i want,,im easy tho.i have a newer 2995dx now and with the night eagle mic it does more than i expected from it..
i just need some bass to get the tinnyness out on ssb so i figured i will have this eq for the rest of my life and i like buying things from "the lil guy " made in the U.S. of A..
TIME WILL TELL,i got 2 amplified d104,s 1 newer board and one older,and 1 for my d201 tram,non amplified,,a sedelta echo master plus classic" a couple radio shack mics that sound great"dynamic"..and a old cobra ca72 dynamic/ceramic compression styl in good shape inside..and 2 electrets from a 900 mhz bellsouth cordless phone,all to try when the w2ihy eq gets here..just for the fun of it..
i will start a thread so the bashing can continue<More audio>
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