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12-16-03
Q: Recently bought a 1/2 master speed recording of Elton John's Goodbye Yellow Brick Road on vinyl. It was done by direct disk labs and says it needs a dbx decoder in order to get the full potential of the album. Do you know where I can find this decoder, and what it is. It is suppossed to be hooked up between the tape monitor circuit of a receiver or preamplifier, or inserted between the preamp and amplifier in an audio component system. Would greatly appreciate any info.
Thanks,
Ted
A: Hello Ted,
Ahhh...dbx discs. What a great thing they were, until CDs made them obsolete a short time later. Many dbx type II tape noise processors had the vinyl decoder built in as did some of the dynamic processors. Look for a model 228, 224 or 222.
12-16-03
Q: Hi Tech,
It is really nice to have this Q&A page!
Recently I got a Sansui 6060 receiver from ebay and gave it a test drive. In
the first several minutes, it was fine. The only problem was that it had
statics when I adjusted the volume. Then suddently I found that the right
channel has ( very annoying ) noise of pops and cracks, even when the volume
is 0 and no audio input at all. And the volume of the noise didn't change
when I turned the volume knob. The left channel is OK.I did some research via google. Someone said that it might be caused by bad
resistors/caps. I wonder if those are the most common ( possible ) reasons.
Is it possible to be caused by the dusted volume knob? If I want to solve the
problem myself, what can I do then?I appreciate any help. And thanks for your time!
-Andy
Q: Hello Andy,
Could be a bad cap, or even the unlikely bad resistor, but I would suspect a noisy driver transistor. You can try cleaning the controls, switches and relays but I doubt that will solve the problem. Unless you are an experienced tech, there is little you can do yourself.
12-08-03
Q: I am thinking of buying a pioneer sx 1250 from ebay. the seller states that there is no audio both from the speakers and the head phones. Any suggestions regarding the probable cause or can you suggest some questions I should ask the seller to narrow down the problem.Do you know of some places I could send it for repair.
Thanks for your help. PaulA: Hello Paul,
That is a very risky approach to acquiring vintage audio. Unless you are an experienced tech there is nothing you can do yourself. The unit may be missing critical, no longer available parts or may have extensive damage. You can easily spend several hundred dollars on a competent repair. As you are aware, this is a significant piece of equipment. When 160 watts RMS goes bad, much damage can be done. The tuner section is outstanding, but will only perform as well as it's last alignment. If you are serious about acquiring a collectable example of this model you are better off buying it from a dealer that has serviced it and supplies a guarantee.
12-04-03
Q: Hi,
Firstly what a great find on the net! I recently picked up a great condition (physically) Beogram 4002. I was told it was faulty, hence the bargain price. What happens is the little B&O lamp lights on the sensor arm and the arm drives across the surface of the record ... to the center then drives back to the home position. I'm thinking it could be a problem with the sensing, perhaps a switch has gone missing or something?
I wondered whether in your experience you've seen this before and if it can be fixed!
Thanks and look forward to hearing from you.
Best regards
Richard
UKA: Hello Richard,
There are several things that need to happen before the tone arm will descend to the record. A record must be on the platter and be sensed by the secondary arm with the lamp and photo-sensor in it. A common problem with the 4002 is the inability of the tone arm to drop due to the gumming up of the tone arm mechanism. It's possible that the arm tries to drop, but can't because of the gummed up mechanism, and then the linear tracking servo takes over and slowly moves the arm to the end of the record. There are also lamp activated sensors responsible for the absolute positioning of the tone arm for set down point, either 33 or 45, and for end of record. You may have more than one problem. I would verify the ability of the tone arm to drop first.
12-03-03
Q: I have a Kenwood KR-9600 after it plays awhile 15 minutes or so the left channel POPS and quits putting out anything. Bad output pack? Any idea where to find one it's a TA-200W seems to have disappeared off the face of the earth? Found one on e-bay guy wants 125.00.
A: Hello,
Yes, it could be the output pack. The only way to be sure, unfortunately, is to replace it. And, yes, they are no longer available. We recommend against investing in any equipment that uses output ICs vs. discrete transistors. Maybe you can sell the rest of it for parts, like the guy on ebay is doing.
11-21-03
Q: What can you tell me about the Panasonic SL-701c CD-4 turntable?
Would I be able to play my SQ quads and hear the separation?
Are there 4 outputs that go to a receiver or are the outputs stereo and the receiver decodes the signal out to four channels?
I have looked all over the internet and can find no information on this turntable. Can you help?
Thanks.Glen.
A: Hello Glen,
The SL-701 was made between 1974 and 1981, it retailed for $180.00. It is described as a turntable "w/CD-4", which implies that it has the CD-4 decoder built in but I can't say for certain. You will still need a four channel amplifier to reproduce the four channels. The CD-4 decoder will not decode SQ records, they are two different formats. Any turntable with a good cartridge will work with any of the four channel encoding schemes, provided you have the appropriate decoder. All quad records produce two channels of audio which are then decoded into four channels by your quad capable receiver or stand-alone decoder.
11-18-03
Q: Dear Tim,
Having sold my Marantz 115b Tuner and 1090 Integrated Amp (which I wish I still had) about 18 years ago, I now have the time and opportunity to start collecting and enjoying classic audio equipment again. I may be picking up what appears to be a pristine Sansui 5000X receiver, a Pioneer SA 9100 amp and a Pioneer TX 7100 tuner.
Two questions:
First the Sansui. In the mid 70,s, when I was working as an audio technician while going to college, I modified several Sansui 5000 receivers for a problem with blowing drivers and output transistors. The mod was expensive and entailed replacing the two driver boards and output transistors with updated components from Sansui. In the cobwebs of my mind I seem to remember that the 5000 and 5000A were subject to the mod but the 5000X was not prone to the problem. Can you clarify this for me? Also do you know if any of these upgraded boards are still available?
Second, I read on a site called Tuner Info that Bill Ammons builds a small circuit board to improve the filtering and gain in the IF section of older tuners to improve capture and signal rejection but the site gave no further info or contact link for Mr. Ammons. Do you have any knowledge or info on this.
Thanks,
Stan
A: Hello Stan,
I am not familiar with the Sansui mods, but it sounds like something I've heard before. You can forget finding any OEM parts for a unit that old. From the data available, it is unclear which was the last version of the 5000 produced but I would think the /A or X version probably had the upgrades.
As for the Pioneer tuner, let me say this about that. I do not believe in unnecessary modifications to vintage equipment, except in cases such as you previously mentioned. The likelihood of unintentional damage is too great. The TX-7100 is an excellent tuner and once properly aligned will perform to your highest expectations. The subtle increase in performance from a mod such as that may be indiscernible. If you're trying to pick up a signal that is weak, or next to a very strong signal, you can do things such as install an outdoor directional antenna or purchase a tuner with a narrow IF option. Also, without the proper test equipment there is no way to verify any modifications or align the tuner to begin with. This is just not a "do it yourself" item.
Tim
11-13-03
Q: I own a Marantz 2285b. I have built custom speakers with 8" Vifa Drivers Scan-Speak 9300 tweeters & custom x-overs. The sound has been nothing short of breathtakingly beautiful.
So, like a perfect idiot, I tried to make it 'more' beautiful by grabbing a copy of the service manual and by trying to follow the directions here: http://www.tnt-audio.com/clinica/bias_e.html I don't think the directions were flawed, but I think I was. I didn't replace my pots because I felt that the Marantz stuff was of sufficiently high quality...although their old age may make me wrong.
At any rate, I jacked what I believed to be the 'quiescent current' up to around 100 mA by adjusting the amp voltage resistor (pot) to it's max. I marked the original positions first. When I plugged it back in, it was a disaster. -The bass and treble were grossly exaggerated and the mids were hollow and not very present. I ended up discovering that I was taking a reading off the wrong 'emitter' resistor and promptly returned the pots to their original positions. I also tried to adjust the DC offset to 0 for both speakers at first, and have since returned those pots back to their original position (both ~50 mV) as well. No joy -still hollow sounds. Portishead sounds like they're singing through a Pringles can and Pink Floyd sounds like A.M. Radio.
I have also tried the approach of setting the idle current to 30 mV (as per the directions in the service manual) and I have also verified that I'm measuring across the correct posts as indicated in pictures and by number in the service manual. Still no happiness. While the bass and treble sound somewhat less distorted, the mids won't come out of the Pringles can. I feel almost as bad as somebody who's put diesel in their Ferrari and can't get it to work right on high-octane anymore. In other words I have the sinking feeling that the whole amp was in some magical state of equilibrium as the components aged and my ,er, 'tweaking' has destroyed it.
Are there components that I may have damaged when trying to crank the pots to get more current to the tranistors? No smoking or bad smells, but the heat sinks did get quite warm to the touch before I backed off. I'm willing to take the amp circuit board out and replace every single component, if necessary. I plan on starting with new pots that allow for finer tuning.
Please Help...if not for my sake, at least for the sake of something beatiful like the Marantz.
A: Hello Matt,
Interesting. I read the article that you referred to and it seems right on the money. However, my philosophy is to avoid surgery, especially when not performed by a surgeon, whenever possible. I am skeptical that a change in bias would cause such a drastic change in audio performance, unless you lost the bias altogether. I suspect something else is going on. Audio is actually science, not magic. At this point I would search for some empirical evidence that something is wrong. By that I mean bench test the amp for power, distortion and frequency response.
11-07-03
Q: OK! I have a real pickle here. I'm a dj. I have 2 technics 1210s hooked up to a vestax mixer and an old kenwood integrated amp pushing a pair of new klipsch 8" 2 ways. I have all of this placed on an industrial wire shelving unit in my garage. The spekers are placed on the top shelf firing down at me. When I turn the gain up on my mixer and the needle is resting on the record (not playing) the speaker's woofers begin to flutter. The higher the gain, the worse the flutter. It doesn't flutter unless the needle is on the record. However, the fluttering stops when I take the speakers off of the shelf and place them somewhere else. If there is even a small corner of the speaker touching the shelf they begin to flutter and stop immediately when I take the off again. What is causing this and how can I keep it to where I can continue to use my speakers on the shelf. Please help me. Thanks.
A: Hello Chad,
You have a bad case of acoustic feedback. If the Kenwood has a "low" or "subsonic" filter, turn it on. If it does not, go to your local hifi shop and see what they have for outboard subsonic filters.
10-28-03
Q: Hi,
I have a pair of Sansui SP-X6700 speakers.
Cosmetically they look fine and are in quite nice condition. Drivers
are all clean with no apparant problems.However when I hook them up they sound terrible. I tried my Sansui
771, a Yamaha CR-600 and a new Kenwood receiver with the same
results.They sound like a little speaker in a tin can. Weak and with no
depth. Both speakers are performing the same. I can't believe that this
model would sound this poorly. I have a pair of 5500x and 2700A and
they sound amazing.I don't think any of the 5 speakers are blown, but I haven't yet
checked them individually.Could the crossovers be fried? Are there parts within the crossovers
that can go bad?How would a person go about trouble shooting something like this.
I need to decide if they are repairable or if they need to be parted
out.Do you guys have any thoughts?
Thanks!
Wade
A: Hello Wade,
If the speakers have been rebuilt and other than stock drivers were used that could cause the sound to change dramatically. Same goes for the crossover. Inspect the drivers and crossover and see if you can tell if they're original.
10-26-03
Q: Hi Tim,
I'm a student at Penn State University with a love of well built 70's audio gear. In our current collection of receivers we've a got Kenwood KR-9600, and Pioneer's SX-750, SX-980, and SX-1250.
The SX-1250 is currently our workhorse, and has never dissapointed at parties...
Anyhow, during a routine cleaning of the 1250 today, I took off the backplate and noticed what appeard to be a splatter of electrolytic fluid beneath 3 of the 4 main power supply caps. (22,000mfd, 80V). 3 of the caps show small perforations on the underside, with a small amount of corrosion. However, there doesn't appear to be any recent leakage.
So, the question is, should I replace the caps now or not? The 1250 frequently gets played hard, but certainly nowhere near the rated 160W RMS, as our main speakers top out at 80W. I only opened it up to clean the switch contacts -- there had been no signs of power inadequacy or degredation in sound quality.
Pioneer stocks the caps at a Whopping 79.34/each, so a set of 4 caps would rival what I paid for the used receiver! Replacements could also be substituted (Panasonic makes a screw thread 80V 22,000mft can-type electrolytic) -- but I'd rather stick with the original components.
Do you recommend replacement? Or should I just continue to use it, as power hasn't been a problem. If replacement is the name of the game, can you recommend a parts supplier?
Thanks for any help in advance,
AlexA: Hello Alex,
It is common for large capacitors to "vent". You can see the vent on the bottom of the cap, it looks like a small "X". At some point in it's life your SX-1250 probably got hot and that's what caused the venting. The caps may be fine, the only way to tell is to test them. You can measure the AC ripple across each of the caps and if it's consistent, and if you don't have any problems such as a constant hum, they're probably fine. You could just replace them all arbitrarily, but I tend to avoid unnecessary surgeries.
Tim
10-03-03
Q: Could you describe 'loop antennas'. I have several decent stereo receivers and they all come with a loop of wire that connects to the back for AM reception. Why don't they use built in antennas such as ferite rod types ? I recently purchased a Sansui R303 receiver and the AM loop was missing. Without it there was no AM reception. I connected a coil of wire; one end to 'antenna' and one end to 'ground' and got feeble reception. When I disconnected the 'ground' connection the reception was very good. I don't understand why a cheap table radio has a built in antenna and gets good AM reception while a relatively expensive receiver has only a coil of wire. As you can guess I am not a radio engineer, but can appreciate general design explanations. Thanks, NS, Hillsborough NJ
A: Hello NS,
The wavelength of the AM signal is very long, hundreds of feet. Both the ferrite rod and the loop type contain long lengths of wire arranged as to approximate an antenna of great length. In my experience, one works about as well as the other. Then there is the difference in the radios themselves. Some AM tuners are going to be better than others just as a matter of design. Expensive receivers often have less than perfect AM sections, most people buy them for FM and vinyl, while the table radio has only one purpose. If you want to make a good AM antenna, you will need a long length of wire. Run it up to and across your roof.
09-28-03
Q: Hello, "tech"!
I have a pressing question referring to my vintage Sansui RA 500 spring reverb. First, one of the channels on my reverb unit doesn't work and not being a technician myself I'd like to know where to look to narrow down the problem. It's been this way since 1995 when I acquired the unit from my Dad and though he was able to fix the lamp fuses (question #2 to come), he was not able to correct the blown channel. For technical reference it is the left channel that is blown. I get sound through both channels but only the right channel has the reverb effect. If this is a "fix-it-yourself" type problem any leads or suggestions will be greatly appreciated. Now for question #2 - The lamp fuses in my unit just don't seem to last. 1 - Is this normal? Could it be traced to the problem of the blown side? And 2 - More importantly, Why can't I seem to find anybody with any knowledge of these machines??? Radio Shack knows nothing about these things and they were the ones selling them in the '70s. They know nothing about lamp fuses and all the hi-fi outlets in my area (Madison, WI) claim to know nothing about the RA 500 or the lamp fuses! OK - Question #2 is a bit rhetorical, can you give me part #s of these lamp fuses and somewhere that still has them available? Actually, I have the original owner's manual and schematic sheet with these part #s but nobody seems to be able to find anything on these mysterious lamp fuses. Please help me!!! I want to get this thing running tip top again, it's just way too cool to have collecting dust! Fortunately I also have a Pioneer unit from the same time frame - I can't think of the prefix number but it's a 202 with the green display - and this one works tip top and actually sounds a little bit warmer than the RA 500 but just doesn't look as cool (lame, I know but hey...), I like the rainbow effect of the RA 500. OK, I just did some really quick research, it's an SR 202. But anyway, if you can help, PLEASE DO! Thank you VERY MUCH! - JesseA: Hello Jesse,
Check and clean the controls on the RA-500, sounds like the one that enables the reverb effect may be dirty. Check the connections on the reverb spring unit, and if necessary, swap the channels to further diagnose the problem. Most of the folks working at Radio Shack weren't alive when your Sansui was built, and if they were they went on to better things. They do the best they can. As for the fuse lamp, we have many types available. See if you can get any numbers off of one of the old ones.
09-22-03
Q: Hello Tim,
I have a TEAC A-770 3 Head cassette deck. My problem is with the dolby circut. I turn dolby on and my volume level in the right channel decreases just enough to be noticable. You can even see the slight drop in the VU meter. Is there an adjustment for this or must some board work be done?Thanks Tim,
J.D.
A: Hello J.D.,
First, make sure the switch that controls the Dolby function is not dirty. Could be one channel is getting Dolby and the other isn't. If that's not the problem, then it could be that the Dolby circuit is out of alignment or the head is bad. If the head is worn and the frequency response is poor then the Dolby will not track correctly. Ideally, you should go through a complete alignment of the machine.
Tim
09-10-03
Q: Hi.
I just discovered this website, and it's awesome. I am quite competent with electronics, and am interested in knowing if it is possible to alter the tone controls on my pioneer SX 550 to more useful and musical frequencies. I had been using an old Onkyo tx2000 for years, and I liked how the tone controls were voiced on that unit much better. On the 550 the bass gets really muddy, and the treble control seems voiced way to high. The cymbals in jazz music seem to just get hissy, whereas I would like to have them be more chimey (is that a word?) I have a ten band eq and I cannot seem to get good sound with it. I am not a huge fan of the pioneer receivers, but i cant yet afford my dream Marantz 2270. Is there an easy way to lower the ranges of both of these controls? I think the bass control would just have to be narrowed around 60 HZ to sound good to me, and perhaps the treble around 10K? maybe even a little lower? any info would be great. This receiver has plenty of power for me, probably 20 watts or so per channel, I havent done much research on it yet having gotten it a few days ago. The Onkyos FM quit and I wanted something different, and this was given to me for free, so I cant complain about the price. Thanks a lot. - - - AaronA: Hello Aaron,
I suppose anything is possible. You would have to change the RC time constant of the tone controls, swapping out various resistors and capacitors. Sounds like too much work to me. I would concentrate on finding an outboard device to replace the tone controls. A 1/3 octave EQ or perhaps the preamp section from another receiver with tone controls you like.
Tim
08-31-03
Q: Hello,
I have an older Harmon Kardon reciever (430). When I turn it on there is a crackle sound that comes from the speakerwhen I move the volume knob. After 20 seconds or so it goes away, If I wait 20 or so seconds before moving the volume knob it will not make the sound. I have been told the caps are warming up and don't worry about it. Could you provide some input on this please. Thank You for your time
Best Regards
MikeA: Hello Mike,
Well, the caps are charging up, not warming up. There are small capacitors in line with the audio in the control section. Until the caps charge there is a small amount of DC on the controls, which is what you hear when you move the control. Just wait the 20 seconds if the noise is a bother.
05-18-03
Q: Hello,
I have a couple of questions that hopefully you can answer for me ............
What exactly is Fm De-Emphasis? and What is the correct setting in the USA?
I have a Pioneer TX-9500 AM/FM vintage tuner which has the Fm De-Emphasis switch on the back panel and would like to know whether to set it for 25, or 75 micro secs.........or does it really matter?!?! The 25ms setting seems to highlight the audio in the higher frequencies. The 75 ms setting seems to work opposite regarding the audio. Any info would greatly be appreciated. Thanks!
Greetings from Texas,
gilbertA: Hello Gilbert,
FM broadcasting employs a procedure known as "emphasis" which boosts the high frequencies of the audio during transmission. All receivers must compensate for this by employing the opposite frequency response characteristic known as "de-emphasis". Different countries use different frequency schemes, the U.S. uses 75uS (75 micro-second) de-emphasis. To maintain correct frequency response your tuner needs to be set for 75uS.
05-16-03
Q: Hi Tim,
Thanks once again for your time. I'm thinking of boosting power in my system. I have a vintage Pioneer system w/ reverb,processor,eq,2 tape decks all going to a SX-1250. Could I add an amp after the receiver to boost power? Also, am I right in thinking an integrated amp is a pre-amp and an amp built into one?
I really appreciate the time you take in answering all my, what must seem like dumb, questions.
Sincerely,
LouA: Hello Lou,
You need more than 160 watts per channel? What for? Yes, you can use the SX-1250's pre-out connections to drive another amplifier. But, what you cannot do is try to bridge the 1250's speaker outputs with another amplifier's outputs.
Tim
05-02-03
Q: Hello Tim,
I have a teac X-1000R with DBX-I Now My question is if I were to make a recording using DBX-I could I play this recording back on another deck that is hooked up to a stand alone DBX-II decoder/encoder? In short is DBX-I compadible With DBX-II? (I appreciate all the advice you have given me in the past!)
Thanks,
J.D.A: Hello JD,
I am a big fan of DBX noise reduction and have used both type I and type II extensively. They are not compatible. Type II was designed for use with tape machines with poor high frequency response, or poor high frequency stability, such as low end consumer cassette decks. Type I is the pro version. The way the companders sense high frequency content is different between the two, and the two types will not track correctly between each other.
Tim
04-29-03
Q: Hi Tim,
I have recently obtained via ebay a pristine Technics RS-M68 cassette deck. It is gorgeous and I think it weighs more than my car. Despite her beauty, she doesn't work very well. These are the symptoms:
With Tape Out:
* Motor operates in both directions when Play lever is pressed
* Motor does not operate in either direction when either rewind or FF is
pressedWith Tape In:
* Motor plays only to the left (Reverse) side. There seems to be an output on the meter, but none when hooked up to a speaker
* Motor does not rewind or fast forward\I used to be electronically adept, however it has been awhile. Can you give me some sense of direction? I do not mind putting in the time as the deck only cost me $10 (yes, really).
Thanks for any help,
George
A: Hello George,
You may have bitten off more than you can chew. The tape transport has problems. They could be bad motors, worn and hardened belts and rollers, gummed up pivot points, or most likely a combination of all of the above. If you get the transport working, then you will have to deal with any electronic and alignment problems. BTW, this is a cassette deck and does not contain any amplification. You won't hear anything with it hooked directly to a speaker.
Tim
04-01-03
Q: Tim,
I happened upon a Sansui G-9700 while bartering with a guy for machine shop services. It's quite a unit (power & weight)...that I have no real home use for. I am however into "bumpin alittle bass" nowandagain..LOL.
Is it possible(or feasible) to adapt this 600 watt sweety to an auto environment?? I understand that it is a DC amp, so am I correct in assuming that all I need to do is power up after the transformers? Basically, bypassing them altogether?? BTW..I am just a machinist, not a ET..either way, am I on the right track?Thanks
MikeA: Hello Mike,
You have a car big enough to fit this thing? Bypassing the power transformer won't work. There are many different types of DC required by this unit that a car electrical system cannot provide. For example, the power amplifier needs plus and minus 50 VDC or so. You could, however, use a power converter to convert the car's 12 VDC into 120 VAC. Just make sure you get a big one.
Tim
03-29-03
Q: Hi Tim
Can you tell how to measure the power output of a receiver? Do you need a special equipment or can be measured with an ohmmeter?
Thanks
AdamA: Hello Adam,
You must have a passive load, i.e. large 8 ohm resistors, to operate the amp into while testing. You could then measure the voltage across the resistors and calculate the power using Ohm's Law. However, you would have no indication of distortion or clipping. The correct method requires quite a few pieces of equipment, including a distortion analyzer and oscilloscope. Go here: http://www.classicaudio.com/forsale/bench.html
Tim
03-01-03
Q: I have a Sherwood S-7900A receiver. I plays well, but I'm having one problem. When I power on the unit and begin to increase the volume, the sound is scratchy. I thought it was a dirty control at first, but as I exercise the control, the scratchy noise decreases and disappears in about 12-15 seconds. It acts the same way each time I power on the unit. If I power on the unit and wait 15 seconds with no volume, then when I turn up the volume, there is no noise. The scratchy noise is at the same level of volume no mater where the volume control is being exercised. Basically, the noise does not increase as the volume increases. Cleaning the control did not help. Could you give me some guidance.
Thanks,
John
A: Hello John,
The coupling capacitors between the various stages in your receiver need to charge up when the unit is first turned on. While they are charging there is a small amount of DC on the volume control, that's what you're hearing. This is probably normal, but it could be the caps are getting old. You could try replacing them, but if it were me I would just wait for the 15 seconds before adjusting the volume. If the caps were truly bad, you would notice a significant degradation of the sound quality.
02-26-03
Q: My question relates to finding a good match between amplifer power and speaker power requirements. About 25 years ago, I had an audio salesman tell me that he recommended that folks buy speakers that were capable of handling 25 more watts per channel than the amp. For example: 100 watt per channel amp you buy speakers capable of handling 125 watts per channel. Or 50 watt per channel amp buy speakers capable of handling 75 watts per channel. He said this was a way to keep from encountering over or under powering of your speakers. Is this a good way to find a match for speakers and amplifer? Was his advice some you would follow? Also, could you please explain how folks blow holes in their speaker cones by turning up the volume too loud? I am sure those of us out looking for vintage equipment would appreciate any advice to try and find a good match for our stereo systems. Thanks, Tim for your advice and explanation on this subject.
A: Hello,
Assuming you don't care about duplicating the sound level of a Grateful Dead concert, you can pretty much do what you want. Very inefficient speakers require more power than very efficient speakers. Most speaker damage is caused by having too small an amplifier rather than too big. An underpowered amp will go into clipping, creating square waves and destroying voice coils. You need to know the efficiency of the speaker you are considering. Since older amplifiers did not have much power, older speakers were very efficient. I have seen newer speakers eat up a 500 watt McIntosh amplifier very quickly. Power ratings of speakers are maximums which you should try not to exceed continuously. Besides, by the time you reach that maximum level you are almost at the Grateful Dead concert level and most people don't listen at that volume.
Tim
02-23-03
Q: Hi Tim,
I just bought a Marantz 2225 receiver that is in good condition except i notice a problem I've encountered on other older receivers before. I can only turn the volume control to about 9-10 o'clock before it becomes too loud and distorted. From the 0 position to about 9 o'clock, it seems to get way too much power/loudness too quickly, and this is only a 25 watts/ch i have connected to speakers that will take 200 watts/ch. Does this indicate a certain problem with the pot, or amp, or something else? I've seen this problem before in an old Technics receiver.. where you can barely turn the volume up, before it seems like it's playing at full volume with distortion.. can you give me an idea on how to fix or how to diagnose? Thanks, Greg in Chapel Hill, NC
A: Hello Greg,
If you are using an external source, such as a cassette deck, turn down the output. If not, then the unit may or may not have a problem. You need to find out if it is running out of gas too quickly. To do this you will have to measure the output power and distortion.
Tim
02-20-03
Q: Hi Tim,
Well I've a situation that I bet you've heard about many times. I have this Pioneer SX-939 and when it's turned up to the noon position the protection circuit trips. At the point of the trip it is loud and clear with no distortion. So I tried the same thing with the speakers off and it still trips.Is this normal? Is this something that a tech could adjust? Is a part needed? What Could you tell me?
Thanks Tim,
J.D.
A: Hello J.D.,
The protect circuit will activate if you drive the amp into distortion with or without a load. It could be that you have some very low frequency noise, or a high frequency oscillation or one channel clipping prematurely that is tripping the protect circuit. Any of which may be inaudible. Have the amp bench tested for noise, distortion, power, etc.
Tim
02-11-03
Q: Hello,
I recently re-capped---retubed --replaced the power cord (with a polarized plug) and added an in line fuse to an RCA X-551. (all amercian five tube)
This radio had been dead for many years. I've always wanted to learn how to fix my tube radios.
The radio generally is playing great now. Tone is full and rich..and plenty of volume.....but how much hum is normal? The hum I have moves up and down with the volume.
Why on one strong (50000 watt local station) the signal (680 on the dial) is the that sgnal reception so weak compared to other stations? And why would the radio at various times of the day-- pick up faint signals from other stations.
Should I re-clean the tunning capacitor? I don't remember if I cleaned it very well. Would that cause the signal problems described?
Am I expecting too much out of the radio? I would be grateful for some advice. For me this was a big step.
Thank You.
BarryA: Hello Barry,
Sounds like you did fine. You probably should perform a rudimentary alignment on the tuner which is fairly easy for AM. I cannot advise you on the procedure, but you should be able to find some information out there somewhere. The hum you mention could be a reception problem, or a problem in the power supply. Measure the AC ripple in all of the supplies and make sure it is OK. The reception anomalies you mention may be normal. Just because you're tuned to a 50kW station does not mean you're located in the strongest part of the signal. Most AM stations, especially the 50kW variety, employ directional antenna systems. You could be located near, or in, one of the signal 'nulls'. AM radio wave propagation is subject to a phenomena known as 'skywave'. Basically, at different times of the day the signal will bounce off of the ionosphere with different degrees of intensity, so you will pick up different signals at different times. The effect is most prominent at night.
02-08-03
Q: I recently inherited a Sansui SE-8X 10-band equalizer in mint condition (really--it had been stored for years, was in the original Sansui box and included the owner's manual). My receiver is a Kenwood KR-9600, which has bass, mid-range and treble controls of its own, but their effect is minimal. I have heard/read that inserting an external equalizer in a system can change (ruin?) the sound; that it is just one more electronic device between you and the sound. True? There must be a good reason you don't see 10-band equalizers except in pawnshops anymore, yet the concept seems like a good one. Your thoughts from a technical perspective?
A: Hello,
Most 'purists' don't even use the tone controls, never mind an equalizer. EQs are generally used to solve problems, either with poor rooms or speakers. I use an EQ in my system to smooth out a pair of Klipsch LaScalas. For best results, use a tape monitor loop to install the EQ in your system.
01-16-03
Q:
I have a Pioneer RT-707 that was recently renewed and seems to work fine. I am under the impression that it is auto reverse. How does that work?
Thanks for your help.
Charles
A: Hello Charles,
The supply side tape guide has a split in it. This is the first tape guide as the tape enters the head block in the forward direction. It is actually a switch which is activated by a piece of foil adhered to the tape. If you short the two halves of the guide, the unit should reverse.
01-10-03
Q:
I have a used, vintage Allison 6 speaker system. That's the 11" square speaker with the woofer on top and a tweeter radiating from one side. I assume the speakers are 8 ohm units. Somebody in the past has pushed the soft dome tweeters in on both speakers. I can order replacement tweeters for this speaker from Allison Acoustics. I have also found another source of Allison tweeters with the same diameter for half the price of the Allison replacements, but they are 4 ohm. What would happen if I were to use the 4 ohm tweeters instead of the 8 ohm tweeters to save some money? Would the sound be destorted or harm my amp? Thank you for any help.
A: Hello,
You should not change the impedances of the drivers. The crossover is designed to work with a certain impedance. If you change it, the speaker will not sound the same. If all that is wrong is the dust covers on the tweeters are pushed in, take a piece of masking tape and pop it back out.
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