Home |
Search |
Today's Posts |
#1
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
In a previous post ("tuner repair problems") I outlined some steps that I
had taken to repair a Sansui T-80 AM/FM tuner. In particular I replaced all of the electrolytic capacitors. This seems to have fixed the unwanted behaviors. However, quite by accident (rec'd the wrong part from DigiKey) I replaced the series output cap with a much smaller value cap. The cap in question was spec'ed at 0.15uF. There was actually a 0.22uF in there when I started, and the cap I inadvertently put in was 0.0015uF. It sounded bad. Tinny. Not much volume. I understand that this cap in conjunction with my pre-amp's input impedence makes up a high-pass filter. Frequencies below 3.5KHz would have been attenuated with this tiny cap, hence my tinny sound. Well, I put the 0.22uF caps back in while I waited for the correct 0.15uF caps. The sound improved dramatically. I measured the input imepdence of my amp at 30.2K. As an aside, I also calculated it from the schematic and it should have been about 44K. Anyways, using the measured impedance, I should be using a 0.26uF filter cap if I want to roll off at 20Hz. Hmm, wonder what would happen if I stuck in a 1uF cap (the next higher-size cap I happened to have in my inventory). Wow. What a difference! The bass is tight and defined INDEPENDENT of volume. Not only do I not need to use the loudness button on my preamp at low volume, I can't use it without it generating more bass than I want! This has made such a huge difference to the sound of this tuner that whereas before I was thinking of replacing it, now I definitely will keep it. Is there any downside (potential harm) to what I've done? I have a subsonic filter (15Hz) on my amp which I have switched on to avoid any subsonic damage to my speakers (shouldn't matter if sound below human hearing is filtered out, right?). The 0.15uF cap in the design spec would start my bass roll-off at 35Hz. Wouldn't it make sense to size the filter cap in each component to jive with the pre-amp's impedence? You'd almost think manufacturers would put in some jumpers and a few ten-cent caps so you could adjust it to suit. Dave |
#2
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
In article ifCTf.4051$J43.2587@edtnps90, "Dave" wrote:
In a previous post ("tuner repair problems") I outlined some steps that I had taken to repair a Sansui T-80 AM/FM tuner. In particular I replaced all of the electrolytic capacitors. This seems to have fixed the unwanted behaviors. However, quite by accident (rec'd the wrong part from DigiKey) I replaced the series output cap with a much smaller value cap. The cap in question was spec'ed at 0.15uF. There was actually a 0.22uF in there when I started, and the cap I inadvertently put in was 0.0015uF. It sounded bad. Tinny. Not much volume. I understand that this cap in conjunction with my pre-amp's input impedence makes up a high-pass filter. Frequencies below 3.5KHz would have been attenuated with this tiny cap, hence my tinny sound. Well, I put the 0.22uF caps back in while I waited for the correct 0.15uF caps. The sound improved dramatically. I measured the input imepdence of my amp at 30.2K. As an aside, I also calculated it from the schematic and it should have been about 44K. Anyways, using the measured impedance, I should be using a 0.26uF filter cap if I want to roll off at 20Hz. Hmm, wonder what would happen if I stuck in a 1uF cap (the next higher-size cap I happened to have in my inventory). Wow. What a difference! The bass is tight and defined INDEPENDENT of volume. Not only do I not need to use the loudness button on my preamp at low volume, I can't use it without it generating more bass than I want! This has made such a huge difference to the sound of this tuner that whereas before I was thinking of replacing it, now I definitely will keep it. Is there any downside (potential harm) to what I've done? I have a subsonic filter (15Hz) on my amp which I have switched on to avoid any subsonic damage to my speakers (shouldn't matter if sound below human hearing is filtered out, right?). The 0.15uF cap in the design spec would start my bass roll-off at 35Hz. Wouldn't it make sense to size the filter cap in each component to jive with the pre-amp's impedence? You'd almost think manufacturers would put in some jumpers and a few ten-cent caps so you could adjust it to suit. It might seem a bit strange to be working on an inexpensive tuner to such a degree. Most mods to tuners involve getting more sensitivity and more selectivity. Perhaps there are things to be learned. It seemed to me a long time ago, that FM had rolloffs, or perhaps it was TV sound. 50 Hz rings a bell. Today, there is plenty or too much bass. Many brodcasters are using 3 band compression, and many songs have way too much low bass compared to listening to it direct from disk. greg |
#3
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
"GregS" wrote in message ... In article ifCTf.4051$J43.2587@edtnps90, "Dave" wrote: It might seem a bit strange to be working on an inexpensive tuner to such a degree. Most mods to tuners involve getting more sensitivity and more selectivity. Perhaps there are things to be learned. It seemed to me a long time ago, that FM had rolloffs, or perhaps it was TV sound. 50 Hz rings a bell. Today, there is plenty or too much bass. Many brodcasters are using 3 band compression, and many songs have way too much low bass compared to listening to it direct from disk. I bought the tuner so I could screw around with it with the aim of learning about the various mods without risking destroying an expensive piece of hardware. The tuner cost me $15 and so far I've got about $30 in it. Since I got this tuner, I have felt that it lacks bass response as compared to disk. Now it doesn't. I live in a mountainous region distant from major cities. It is a radio signal wasteland, so I am not really concerned about DX'ing/sensitivity. My cable provider kindly provides me with an fm feed; the stations are nicely spaced out over the dial, so I am not too worried about multipath or selectivity. I listen to a variety of radio stations via cable feed and the quality of sound varies immensely from station to station. I don't know why but I'd guess that, like everything else, quality FM signal costs money (to generate and to reproduce) and how good does Britney Spears need to sound played on a portable player through cheap headphones or through your average car stereo. Here in Canada, CBC-2 sounds fantastic. The local stations tend to sound better than the ones I pull off the cable feed. Does anyone know what is the effect of fm transmission via cable tv feed? How is the signal provided to the cable company and what do they do with it from there? Thanks for the replies. |
#4
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
In article buDTf.4120$J43.1177@edtnps90, "Dave" wrote:
"GregS" wrote in message ... In article ifCTf.4051$J43.2587@edtnps90, "Dave" wrote: It might seem a bit strange to be working on an inexpensive tuner to such a degree. Most mods to tuners involve getting more sensitivity and more selectivity. Perhaps there are things to be learned. It seemed to me a long time ago, that FM had rolloffs, or perhaps it was TV sound. 50 Hz rings a bell. Today, there is plenty or too much bass. Many brodcasters are using 3 band compression, and many songs have way too much low bass compared to listening to it direct from disk. I bought the tuner so I could screw around with it with the aim of learning about the various mods without risking destroying an expensive piece of hardware. The tuner cost me $15 and so far I've got about $30 in it. Since I got this tuner, I have felt that it lacks bass response as compared to disk. Now it doesn't. I live in a mountainous region distant from major cities. It is a radio signal wasteland, so I am not really concerned about DX'ing/sensitivity. My cable provider kindly provides me with an fm feed; the stations are nicely spaced out over the dial, so I am not too worried about multipath or selectivity. I listen to a variety of radio stations via cable feed and the quality of sound varies immensely from station to station. I don't know why but I'd guess that, like everything else, quality FM signal costs money (to generate and to reproduce) and how good does Britney Spears need to sound played on a portable player through cheap headphones or through your average car stereo. Here in Canada, CBC-2 sounds fantastic. The local stations tend to sound better than the ones I pull off the cable feed. Does anyone know what is the effect of fm transmission via cable tv feed? How is the signal provided to the cable company and what do they do with it from there? I used to get FM cable stations, but they were basically identical to the over the air broadcast frequencies. Cable suffers from extra noise which is generated through the whole system, so during full quieting of your FM receiver, thee might still be some extra noise present, which was not part of the orginal broadcast. greg |
#5
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
On Mon, 20 Mar 2006 18:11:26 GMT, "Dave"
wrote: Hmm, wonder what would happen if I stuck in a 1uF cap (the next higher-size cap I happened to have in my inventory). Wow. What a difference! The bass is tight and defined INDEPENDENT of volume. Not only do I not need to use the loudness button on my preamp at low volume, I can't use it without it generating more bass than I want! This has made such a huge difference to the sound of this tuner that whereas before I was thinking of replacing it, now I definitely will keep it. Sounds like you've just cut treble. Which will sound like a "loudness" curve at low levels. If this suits your speakers/room/ears, fine. If you tire of it, you know what to do. |
#6
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
In ifCTf.4051$J43.2587@edtnps90, on 03/20/06
at 06:11 PM, "Dave" said: [ ... ] Is there any downside (potential harm) to what I've done? I have a subsonic filter (15Hz) on my amp which I have switched on to avoid any subsonic damage to my speakers (shouldn't matter if sound below human hearing is filtered out, right?). The 0.15uF cap in the design spec would start my bass roll-off at 35Hz. Wouldn't it make sense to size the filter cap in each component to jive with the pre-amp's impedence? You'd almost think manufacturers would put in some jumpers and a few ten-cent caps so you could adjust it to suit. No physical harm. I'm surprised that the response changes so dramatically. Mostly, I don't expect much from the stations below 50Hz. Are you sure that the capacitor doesn't interact with the de-emphesis? Anyway, it is personal preference. In normal decoupling situations increasing the capacitor beyong a certain point is of little value. Other than some phase shift, the audible consequence from moving the lower cutoff from 10Hz to 5Hz is minimal. As far as FM over cable is concerned, they will usually demodulate and modulate the station at the cable front end. This process could be very flawed -- or not. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#7
Posted to rec.audio.tech
|
|||
|
|||
tuner capacitor question
"Barry Mann" wrote in message .. . In ifCTf.4051$J43.2587@edtnps90, on 03/20/06 at 06:11 PM, "Dave" said: I'm surprised that the response changes so dramatically. Mostly, I don't expect much from the stations below 50Hz. Are you sure that the capacitor doesn't interact with the de-emphesis? Anyway, it is personal preference. In normal decoupling situations increasing the capacitor beyong a certain point is of little value. Other than some phase shift, the audible consequence from moving the lower cutoff from 10Hz to 5Hz is minimal. Yes, I was really surprised too. This cap is not involved in de-emphesis in any way, it is after the output of the MPX demodulator. Changing the cap lowered my roll-off from 35 Hz to 5Hz, and I cut off the lower half of this range with my subsonic filter later on anyway. So I really should only be gaining from 15 to 35Hz which everyone seems to agree is lacking in most FM signal sources. But the SOUND... it's really night and day. As it's part of a high-pass filter, I definitely haven't cut any treble as another poster has speculated. Sometimes you just get lucky. Dave |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
FS: Highly Recommended Pioneer F-9 Tuner | Marketplace | |||
Technics ST-8600 tuner - meaning of the jacks | Tech | |||
Newbie with ST-8600 Tuner | General | |||
Interested in high-performance tube-based AM tuner designs | Vacuum Tubes | |||
AM Tube Tuner Kit -- candidate models from yesteryear? | Vacuum Tubes |