Vintage Realistic power booster and a theory of operation

[@michaelturner4457]

I remember these things, the ones with ICs in bridge-mode usually had a warning about not commoning the speakers to ground. Otherwise they blow-up.

[@12voltvids]

Thats right, and I was expecting this to be a bridged unit. I even talked about that as I was opening the case. Note that was cut out as I had to eat a little crow when I saw the layout.

[@nathen4021]

@@12voltvids I want to ask. Is it ok if I download my favorite videos of yours soley for my personal viewing? I never intend on posting them anywhere online.

[@superwarp12]

I had one of these, with. Radio shack auto reverse cassette stereo, radio shack speakers in my 1979 Ford Mustang fox body. Those were the days

[@jamessouthworth1699]

When I first got into car audio in the mid-80s the standard setup in my circle was one of these and a pair of house speakers in the backseat. There were no dedicated subwoofers for cars at the time so that was the best sound we could get. All the people that laugh at these old school power boosters you have to remember there wasn't a lot of money in the market. They had to build these things so they were still affordable to the average young person. Most of your adults weren't interested in this and young people didn't have a lot of money to spend on car audio. These power boosters were perfect for what they were intended for. Improving power output while remaining affordable to their target market.

[@12voltvids]

Yes i know. We all had them at one point. And the home speakers in the back seat. That one untill a kid crashed his car and an unsecured speaker flew out if the car and into the car that hit him just missing hitting a baby in the back seat. Then the police started issuing tickets for unsecured home speakers in the back of cars. I put 2 8" woofers in a wood box and secured it in the trunk behind the back seat. They did the job intended.

[@RobertDickens2002]

​@12voltvids how would they even enforce this have a road block checking for speakers 😆

[@TheBudgie29]

I bought a lot of Realistic equipment back In the 70's early 80's, The shop In the UK was called "Tandy". There was a Radio Shack shop In a little Town not far from Me, Open Up to about two years ago, and has Now Gone 2020. I still have some of the Disco Mixers and FX Equipment In Their Box's In the Loft. They did sell these Car Amps. I have a Few of the Catalogues, and It's nice to get them out and look at some of the Weird things that was for sale In there.

[@tableseven8133]

This unit came out in 1987, with the transformers and large output transistors I still wonder if they had the switching power supply but it was not advertised that way. However, the fellow in this video seams to have found a unique 12 volt hook up to power the output transistors and speakers using the transformer. In 1988 they had a 40+40 Watt two channel amp with switching power supply, that used the switching (vibrating) transistors to create a AC power source that was more efficient to get higher volts to the output transistors. In 1990 80+80 Watt two channel amp, then in 1993 a 120 watt 2 channel switching amp with bass crossover that also could be bridged to one channel as well. I have several of the 120 and one of the 80+80. Never had any big problems with them except the bridge switch on one of the 120 amps did not always make a solid connection in bridged mode. they then went to the trunk mount type amps in 1994. 2000 was the end of the booster EQ, and 2001 for the booster style amps at Radio shack. Not long after they stopped carrying car audio equipment. www.radioshackcatalogs.com/catalog_directory.html

[@raymondcourtois67]

That link to the old catalogs is a trip down memory lane.. I used to love flipping through those catalogs.

[@envisionelectronics]

I repaired one of these a while ago. It’s just output transformers and no switching power supply. I also own those other amp you mentioned and they do have switching power supplies and no output transformers.

[@tyronenelson9124]

Car radios back in the days used the common ground for the speaker negative, more modern car radios use differential signalling within the pre and main amplifier to avoid using ground for the speaker negative, basically just to keep any audio processing within the car radio away from ground unless you want to listen to any noises within the electrical system of the car.

[@macgvrs]

I had a decent stereo, a Craig I think, into 6x9s in the back shelf of my car and I added a Realistic booster with EQ, similar to yours. A friend had a very nice Alpine sound system in his Volvo. He was shocked when he listened to my cheap little system because it sounded better than his. He went home and improved the seals around his speakers which did improve his sound. He was one very unhappy guy though because I didn't have anywhere near the money in my system that he did. I was forced to operate on a budget so I did what I could with what I had.

[@zx8401ztv]

Radio shack made a lot of very decent products, that booster looks very nicely made :-D. The mirrored pcb layout looks really neat, the track side looks like a work of art. No sloppy engineering like a lot of cheap china rubbish. The thing is it's still alive all these years later, I wonder how much modern junk we have now will last that long. Not much :-(

[@12voltvids]

None!

[@mickspencer4171]

That's a blast from the past,I had that exact one.

[@andydelle4509]

"Not 5 watts of audio, 5 watts of distortion" LOL! I also wonder if those transformers are gapped as there is a considerable amount of DC always going through the primarys.

[@DeadKoby]

Very interesting. I find it easy enough to fill a room with only 5wpc..... providing speakers are efficient enough. Car speakers are generally pretty inefficient, so I get the reasoning.

[@johncoops6897]

Car speakers back in the 1970's were over 90 db/1W...often closer to 100! You could get painfully loud audio from 4 speakers and a BTL (bridged) car amp, which provide about 12W RMS (like this booster).

[@dave141163]

Going by the date code on the back of the unit, It was made in 1977 and IC's were not in common use in power amps of that period and Hong Kong was the maker of stuff back then. In the 80's it was Korea and Taiwan.

[@brianleeper5737]

See the top right corner of page 64 of the 1987 Radio Shack catalog. This unit was made in 1987, not 1977. It also sold for $79.95 back then.

[@pliedtka]

Oh my, remember this kind! Not to many decks had Line Out. To have something like Dolby, one needed to drop a few hundreds. Nice tape decks would have CD changer controler and even remote control. Even the hi-end decks were limited to 20W max at 10% THD. Then classD came and power went twice fold or more. Still people would cook them if protection system was not designed adequately. I remember my friend fried his big Earthquake amp in 90s, this thing could deliver over 300W per ch for two ch driven simultaneously - a lot juice for the time with lots of transistors in power supply and amp section to be changed. Now I see some Class D sub amps with 5kW and more. Then twice the power is only 3dB increase, so better is to find loudspeakers with good bass response and 90dB/W and up efficiency. Please remember that in order to obtain lower bass (lower resonance freq of cone-voice coil-suspension) the moving part will have to be heavier and efficiency will drop. That's why small subs have low efficiency, and to get decent power handling the voice coil will be heavier and efficiency will drop further more (the power handling is not very useful parameter when it comes to how to judge loudspeakers quality). Also heavier assembly needs stiffer suspension - never ending cycle of pros and cons. Just for reference 50W is 17dBW, 100W - 20dBW, 200W - 23dBW, .... 1000W - 30dBW. And keep the Loudness button in OFF position - usually lowers distortions, unless someone likes boomy Bose style sound.

[@waltschannel7465]

I had a Sanyo unit that was similar. Played well for a while, then blew up. Took it back to the store, and the store owner allowed me to apply that purchase to a more robust Sanyo amp. The second amp had line level input but my car deck (also Sanyo) did not have line out. It was such a total pain to fit that deck in the dash of my 1965 TBird that I did not want to upgrade it. Had that setup until I sold the car. I bought that setup in 1980.

[@spankyham9607]

As I have gotten older, I have preferred to put back into my old cars ( 70's and 80's ) the factory deck, because I find they have stronger tuners, and with some help of amplification, they can sound very well. Modern blue teeth to FM transmitters solves the problem of modern compatibility, albeit not perfect but good enough for me. Certainly these downsides of this era of amp are not something that would be cared about in a car setting and would be more then sufficient unless you are trying to 2-Pac your car with subs, obviously then it would be quite lacking. I like the mechanical nature of the past. No settings to lose when the battery is changed and no memory or very little to draw on the battery. Even factory radios of the time, didn't draw as much stand by power as modern radios because they were much simpler. Having a dead battery every 2 weeks because of the radio draw will make you rethink your priorities. So yes, these are somewhat valuable if working.

[@12voltvids]

Well i never worry about a dead battery I just plug my car it.

[@DazzaDirect]

@12voltvids #12voltvids thankyou for creating and uploading this video, i think its amazing when you create thes type of videos and dive in depth as to how products actually work , i find it fascinating and it is especially even more interesting when its with older tech as it quite often is far more easy for me (a novice and others hopefully) to be able to grasp and digest what is actually happening throughout the entire device. i am now thinking , 1. As this device has the common ground (which as you said was not as common as most required an individual negative for ground for each channel) does this mean in effect the other type were creating a sort of higher floating ground to in effect make a split rail. 2. did the other more common type use transformers too. 3. did the other types have a negative grounded chasis or not , i think i heard you kind of say they didnt. 4. were the other types also class B or A/B or were they only class A. 5. i also wonder what happens if you were to connect both trainistors to two seperate channels on a scope would they be phase inverted Once again i would like to say a real heart felt big thankyou for this amazing videos, i cant describe the feeling i have when some of the theory i have been trying to learn about transistors suddenly seems to make more sense i suppose it could be akin to a door opening or a light bulb switching on, have a great day ;-]

[@dwindeyer]

If you separate the amplifier from the LLC/EQ section of this, this type of device is still available today, typically to connect power amps to stock head units where replacing an integrated head unit/hvac is too much of a hassle. They even have profiling software to counteract the custom audio tuning done by the car manufacturer.

[@gavincurtis]

These weren’t too terrible as an affordable alternative to the more expensive inverter based power supply types of amplifier in the day. Sold a lot of the 40+40 and 80+80 amplifiers when I worked at radio shack.. Problem is keeping them cool for longest life. THD at maximum output? We don’t talk about that...lol. Tweeter popper if you push these beyond their intended limitations, which when operated within range of reasonable expectations, is a very good sounding booster. These boosters filled a niche until class D amplifier and FET switch mode inverter technology became affordable. Love these videos..the memories they bring back. Sorry if I repeated what was said in the video. These boosters bring back lots of memories. :)

[@12voltvids]

This served me well in my first old car. Got this when I was probably 18. Took it out when I upgraded to something better. Looking through old boxes stuck in storage locker.

[@gavincurtis]

@@12voltvids my father had a really nice top of the line Alpine alpine head unit and infinity speakers in his truck from a high-end car stereo dealer that he did tax accounting for. In turn, he got to pick out a really nice system as payment. Awesome head unit, but only 4 watts per channel. I installed one of these boosters in the truck everybody is like NO! Realistic with your dad’s alpine setup? Then I turned it on...best sounding stereo system in the entire high school parking lot :). What a day of joy. So many fond memories of that system, I still have the old Alpine head unit.

[@jrossman4703]

I love seeing old stuff like that 👍

[@hestheMaster]

The heat sinks really should be outside of the chassis. The design keeps the heat muffled inside but that's how they did things back then. They must get really hot. Wonderful showing this Dave and like your explanation of how it all works.

[@12voltvids]

It does get smoking hot.

[@FluxCondenser]

These things were often installed under the dash on the passenger side. I wonder how many people had their legs burned.

[@12voltvids]

@@FluxCondenser they didn't get that hot. The heat sink was inside the case the hit air exits the top and up under the dash.

[@FluxCondenser]

12voltvids Ah, so the outer case must do a good job insulating the heat if it gets as hot as you say. Having the heat sinks exposed to the outside would have helped cool things better and not doing so probably led to the high numbers of failures reported with these boosters. They may have made the trade-off to protect people from the high heat given that the typical way these were mounted made it more likely for there to be skin contact.

[@12voltvids]

@@FluxCondenser Well back when these were around cars were a little bigger so your legs wouldn't be anywhere near the unit. You want to talk hot, try riding a Harley in stop and go traffic on a hot day. The engine about 450' right between your legs.

[@rogerchurch3804]

thats very surprising i just knew it had dual ics ! transistors! with a step up transformers on each channel led meters nice i remember i had had old alpine booster amp it played realy good through house speakers your realy knowledgeable explaining how this one works helps thanks !

[@brianwood5220]

Great video. Educational every time. Thanks

[@douglashoff95]

I think about the first what could be considered audiophile grade would be the Pioneer AD304. Used a dc-dc converter power supply and gave an honest 20 wpc. I had two of these in my 1974 Datsun (one for the front speakers and one for the rear) Deck was a Pioneer KP4000 in-dash cassette/am-fm. Boy did that sound great! Tapes were made on my Nakamichi 1000 deck. Later came the Concord HPL350 with 20 wpc and Dolby built in which I had in a 1978 Camaro. This used a bridged design with 8 output (discrete) transistors.

[@12voltvids]

I had the audiovox 60wpc amp and it was a true 60 that could be bridged to 120 mono. Ussd a dc-dc converter. Got that one in 1980 i believe.

[@brancarr1]

Nike, "Just Boost It"

[@lewiskhan9825]

nice old school booster

[@fmw63]

Wow! I still have one of these, and it still works!

[@xaenon]

I had a 'basic' model that RS sold, no EQ, just '40W/channel' or so it claimed. What a piece of junk it was. Oh, it would get 'loud', all right.... but it sounded like sh** at anything above 1/4 volume. While ultimately it could go louder overall than the basic stereo, without the booster I could turn the stereo up louder without all the distortion. We went through the installation for weeks - dedicated high-current line to the battery, made sure the speakers were all able to handle the power, no errant grounds anywhere.... we never could get it to work. Even exchanged it thinking it was a factory defect. Nope. The replacement was just as bad. Gave up and decided it wasn't worth the hassle.

[@markpirateuk]

Looks identical to the one I had in my car back in the day to boost my cassette player, they did bump up the power, but the background noise was also boosted!

[@alexispieltin9379]

Once upon a time, Japan and Hongkong were the factory of the world for low end consumer electronics. China (PRC) changed that. These boosters are certainly made with the best technology available then, for the money, as bridged power IC were already available. This one is surprising in the use of a technology inherited of vacuum tube push pull output transformer. Many of these boosters typically used the radio remote control for electric antenna as the On/Off command, but as many car radio did not provide that option, you had to wire it to a switched +12 or an optional remote switch. This one with it's high constant current could have drained many car batteries in a few hours. This one had some graphic equalizer and display, so it was supposed to remain at hands and under visual supervision... I remember when first real high power amps finally went on the market. With their high voltage inverters, they made the wattage literally explode, coming from 6/12W classic radios and 15/30 watts boosters to 100W and more, with an unexpected audio quality and healthy low consumption. Of course, these mostly discrete power amps were somewhat enormous (and expensive!) with bulky radiators (and fans), more than half of their innards were devoted to the high voltage inverters, including coils, driving transformers... It was the MOSFET transistor and Schottky Rectifier diodes feast! With the new class of digital IC power amps, the miniaturization is now operating in these audio car radios, and a 4x50W real output is a standard integrated output!

[@SlinkyStoney]

I saw a booster here that have a bigger transformer and using 2n3055 transistors on both side powered from a car battery. The difference is the output transformer does not have a secondary winding, the center tap is connected to positive supply and the other 2 connections from the transformer is connected to the emitter of the 2n3055, collector is connected to the negative supply and the base is connected to a smaller transformer. It's kinda heavy and it says it could do 150w driven from an214 ic.

[@pliedtka]

I opened one of the JBL cheap car amps - they made better ones 40yrs ago. But generally most car amps were built to survive the heat not to sound good. I bet if someone would put the 3886 IC modules into a box with decent switching car power supply the thing would better than many car amps. Imagine a real separate hi-end home amp, even something like Parasound, Bryston, NAD inside car amp - it would be all car audio reviewers favorite amp.

[@strugglingparodox5709]

All of the old booster amps I've come across, we're just 20 watts per channel. This was the only model I found that was considered a higher output, and utilizing extra circuitry to get more power.

[@12voltvids]

Right. The 20 watt used 2 10 watt ic amplifier chips driven out of phase one for the + lead and the other for - speaker lead. BTL output.

[@michaelturner4457]

I very much doubt this thing is even 30W per channel, probably more like 10-12W per channel. Can see at 20:33 the current draw at maximum is 2.79A at 14V, which gives a total power consumption of 34.5W. Knowing Rat Shack/Tandy it's probably stated as "60Watts PMPO" or something, and not RMS per channel.

[@m.k.8158]

a lot of older auto sound gear was rated in Peak output, instead of RMS, which resulted in highly inflated output figures.

[@giammyzanna]

This model has a line level input too but it should be possible to convert a standard high input only to also have a line in right?

[@bones007able]

I had one from RS.. only must have been a different model, mine had a analog meter to show the power output

[@bassblaster505]

My dad used to talk about those boosters I always wondered how they worked. The transforms remind me of output transformers on tube amps. You think you could make another video doing a power test on the scope? I have a couple car radios from the mid 80s in my closet and you only get like 4W. I have a mid 80s Honda civic radio made by alpine and it was HIGH POWER 6W. Oh how times have changed

[@12voltvids]

Yes they work similar to how tube amps used the output except the tube amp was the opposite. Voltage to current. The tube side high impidence the speaker low. The output transformer was a center tapped primary. This has separate primary winding for each output.

[@AlbertAGhazaleh]

Wonder if CB booster use the same concept? Being there was one used house current and dc current

[@douglashoff95]

A company named Tenna sold a pair of amplified 6x9 speakers called "mind blower" which used the same technique to achieve a "60 watt" output. High distortion, definitely not an audiophile product.

[@12voltvids]

No car audio back in the day was. Not until they started using smps to get the voltage up.

[@sficlassic]

I had one. Thing was a piece go junk. For the same price I bought a power inverter and put my home system in the back seat.

[@gavincurtis]

No way one of those boosters could keep up with what you had. You outsmarted them all.

[@SDS-1]

OMG!!!!!!!!!!!!! I love these!!!!!!!!!! Nobody makes these at all😥😥😦😧

[@SDS-1]

@@danielknepper6884 yea too much $$

[@Felix2417425]

Another solution could be like this: center tap of primary connected directly to +12V, and ends of primary winding going to collectors of NPN pair transistors, emitters to ground. Of course, phase-split driver circuit is needed it that case. Good thing is that then quiescent currents cancels each other in primary, so there is no DC magnetization of transformer core. This push-pull topology is often used in PA amplifiers with 70V output transformers.

[@12voltvids]

Yes that would also work however I believe they went with this design as if allowed the 2 outputs to operate as a more of a class A design to reduce distortion.

[@southernsoundpulse]

Wonderful video! I got a small realistic eq/ booster and I was searching how this thing works

[@burkhardboer5524]

Das weckt Erinnerungen! Tolles Teil. Danke !!! lg

[@chadcurrent1645]

I have an audiovox booster equalizer with similar layout to your realistic booster. It has two sets of transistors also connected to transformers. It has wiring diagram on the back and when connected land off the speakers work as normally bypassed. When I power it on, the light goes on but all sound almost disappears. I'm wondering what would be the best way to troubleshoot it? I'm guessing that I need to check for voltage on the transistor input and bias voltage to tell it to output the 12v? I'm fairly new to all this and figured these old things might be easier before jumping into class AB amps.

[@ВалераПетренчук-з1н]

Получается в режиме простоя даже когда она выключена, эта штука будет потреблять 0.6А?

[@jasonthejawman5442]

Love you're video's you expalne it so well wisdom is knowledge this is my favorite channel📺📺

[@PeterMilanovski]

This video could have been longer and I would have watched it to the end! I could be mistaken but I might have the same one, I purchased an older pioneer and I believe that the other one is exactly like your one from eBay a few years ago! I don't remember if I had a look around inside but the transformer coupled output stage is fascinating! I'm tempted to dig out the ones I have and see if I actually have the same one! Those transformers should theoretically give it a nice sound all the way up to just into clipping like a vacuum tube amplifier! I paid a fair amount for my one and I was okay with that because I grew up with these things and I wanted to have one so that I can get that all important question, what is that grandpa? I'm not a grandparent yet but I'm planning on being the best that I can be. I see how my parents are with my kids so I'm really looking forward to it. I have all sorts of vintage Electronics so I have plenty of things to amaze them with! My son should really be into digital stuff for his age but instead he has a turntable with his own record collection, VCR's with plenty VHS tapes, cassette decks with compact cassettes, DAT machines and so on! He loves spending time recording music one track at a time! Yeah it's slower and harder than digital but he has much more appreciation for the technology and all that touchey feely goodness that digital removed from Electronics... Thanks for posting this video, I really enjoyed it. Now where did I put my equaliser....

[@12voltvids]

I was pleasantly surprised when I opened it and saw the 2 output transformers. This one might be one to do a deep dive on if I can locate a full schematic for it. You are correct with the distortion more closely resembling a tube amp when it clips and all that other magic that happens in the audio output transformer.

[@PeterMilanovski]

@@12voltvids I'm sure that the output transformer circuit design was there way of increasing the output power of a solid state amplifier as opposed to fitting a noisy dynamo to get the required voltage in older vacuum tube car radio's way back when! I know that when the transistors were first being used in the early solid state amplifiers, engineer's were still using transformers on the outputs because they were so used to using them in vacuum tube designs. Apparently those early solid state Amplifiers also sound amazing but I have never heard one due to them being extremely rare! While transformers are expensive in comparison to capacitors, over the long run, if a capacitor coupled output amplifier had it's capacitors fail, it took your speakers with them adding to the cost! While transformers on the other hand are initially expensive, would never require replacement of it or the speakers it's driving! Kinda cheaper in the long run! More up time to enjoy that beautiful transformery sound LoL. On another note, I wonder what the impedance is on both sides of those output transformers?

[@12voltvids]

@@PeterMilanovski Correct. Before car audio went with the smps / dc-dc converter / chopper design the voltage was limited to 12 volts. By using a dual primary transformer as in this setup you effectively give yourself 24 volts to play with. How, well if we refer to the diagram one winding is run directly to the 12 volt rail, with the transistor between the other side of the winding and ground. The other winding, which is 180' out of phase with the first is wound between ground and the collector of the transistor with the emitter going to the B+ rail. On the positive half of the audio signal, one transistor conducts and applies a positive voltage through the transformer resulting in a "North" magnetic field being created. When the audio waveform goes to the negative side, the other transistor goes into conduction. Remember that the other primary is connected to B+ and the other end of it is going to the collector of the negative transistor collector which has it's emitter grounded, so as the transistor goes into conduction it will pull the voltage down on the transformer winding introducing a "south" magnetic field in the core. When there is no sound both transistors are slightly driven on, so there will be a little current in the primary, but since one primary will be producing a north field, and the other a south field, the 2 will cancel each other out. The secondary has many more turns of wire so a higher voltage lower current is output. What might be an interesting experiment to do on camera is to see how much open coil voltage will be produced in the secondary. Of course that is always hazardous to the transformer, because these high voltages of they get too high can arc through the insulation and blow the transformer.

[@PeterMilanovski]

@@12voltvids that would be a great experiment! But instead of doing it at the rated voltage, you can get away with it at a lower voltage from your bench lab power supply! Then with simple mathematics you can just double the figure for example if you only fed 6.5 volts in to get the proper rated output voltage. Also, it would great to put on a 4 ohm dummy load and measure the output voltage of a 1khz input signal to work out it's actual power output before clipping and maybe just into clipping as well because it's transformer coupled and it should technically still sound very good so that we can see how close the output power printed on the face of the unit comes to actual measured values! Maybe the advertised output rating is for 4 speakers being driven? Which probably means that the output of each channel are paralleld and bring the output impedance down to 2 ohm's... Usually vacuum tube amplifiers have separate taps on the transformer output for different impedance speakers, I wonder what effect it has on it's output and transformers? Hmmm there's a lot more to this graphic equaliser booster than what meets the eye! Well if you do decide to do a follow up video, I will be watching with anticipation... It's almost like taking a peek into the minds of the people who were working to design something that would perform to the budget that they had to work to.. I love this kind of stuff, some people just don't understand how much can be learned from a product, even if it was not as good as what they had. This unit actually had some pretty good engineering put into it. They could have used a transformer to step up the voltage in the power supply like every other car amplifier on the market today but instead chose to go with the transformer at the output stage, that way, they can consume more current through the transistors to get the higher output levels. I get what they were thinking, the transformer at the power supply stage would need high frequency switching which can induce noise like distributer wine (remember that abomination lol), while at the output stage, they are only dealing with AF Signal.. much quieter. Kind smart if you think about it. You can even replace the power amplifier with something more modern and still keep the output transformers if you really wanted to. But I like it as it is 👌.

[@thefunkiest1660]

Back in the days i use to make boosters using 2n3055 & mj2955 transistors

[@int53185]

Blast from the past. I had one in my Firebird. Sadly it got ripped off.

[@rkvt]

Hi 12voltvids -- love your videos. I have a quick question: Where's a good place for an amateur to pick up the small capacitors that are needed for desk/box fans (oscillating for the desk one). I can find caps online but all are bigger (in size not capacity) for the place they need to go in the fan. Do you have a favorite source? Great work!!!

[@hestheMaster]

Ever see Dave's take on replacing a box fan capacitor. Try kzbin.info/www/bejne/pYnUaqlrgdCMas0.

[@obieewon]

I had one sounded great when I used my house speakers

[@apolinarmartinez5723]

Its the same configuration of Clarion EQB300, I have the service manual with schematics, if you need a copy please let me know, regards

[@giorgostexnikos6976]

amazing video.thenks for the lessons.

[@killcar5nbike2]

Such an odd way of doing it. All the 100v line amps I've worked on either use 2x N type in push pull on the collector with the transformer CT going to Vcc (like a tube amp), or have emitter followers to Vcc with transformer CT to 0V and a transformer driving the bases out of phase.

[@12voltvids]

Yes an unusual way to do it. Audiovox also did it like this in their early stuff.

[@phillanassa759]

@@12voltvids I had an Audiovox that could have been this things cousin. Bought it with head unit and speakers in the Navy Exchange on board ship. We needed something to spend money on while at sea, stuff for your car back in port was always cool, or a stereo for the home, cameras, drum sets cheap and good. Lots of that Vietnam-era gear came home from Army/Navy Exchanges all over the Far East and Europe too!! We were so spoiled!

[@GeorgeGeorge-xj2bc]

The total power of these amplifiers included and the power losses that were much higher than the real power to the speaker but commercially every amplifier was advertizing with large gold letters as a 50 watt rated or more.Beautiful years for technicians that could make easily a lot of money from selling and repairing of new commercial products.

[@pliedtka]

Imaginary power handling specs - most common in car stereo world, boom boxes and HT world. Sony AVR receiver, or something similar, with 7x100W @0.01THD stickers - sure in the wildest wet dreams.

[@gboy64]

You wouldn't know the model number for that eq would, want to look it up to see if anybody still sell them.

[@12voltvids]

No i don't sorry.

[@toneyisaiah408]

Sir, What's the next project that you are doing?

[@jorgepavon9096]

Nike de favor pregunto tendras el canal derecho de audio con el disipador

[@неболтай-в2о]

What is your opinion on a dual mono Sansui au-719 beast?

[@pliedtka]

Not a bad amp, hard to get the replacement parts. Interesting circuit - what I remember from faith memory.

[@markanderson350]

What does the capacitor do? Looks like cheap and dirty power to me. What power out did you measure?

[@johnhermanson5249]

in the mid-70s I tried one called "Sound Exploder" and gave up after the second one. Sounded like absolute crap, unusable. Store owner claimed I hooked them up wrong, but wiring was so simple, I know everything was done right.

[@zulumax1]

I forgot how bad these power boosters really were. 10% distortion at rated power I believe. Inductor output, ewe! The first really quality car stereo I had was a Pioneer super tuner III with the under seat GM40 power amp which ran an umbilical cable to the head unit.

[@12voltvids]

Oh they were bad.

[@eddys.3524]

You, of course, also could switch your phone into silent mode when recording a video.

[@12voltvids]

The problem with that is I forget to turn it off silent mode and have missed important messages. Viberating mode is no good because I never feel it when it goes off in my pocket. I turned my work phone to silent during a meeting, and forgot to switch it back for 2 days. The boss was pretty pissed when he was trying to get hold of me and my phone was going to voicemail Of course I wasn't getting those notifications either.

[@eddys.3524]

@@12voltvids that indeed remains a problem...

[@giammyzanna]

I have one from marantz. I modified it to accept a line level input but the output is quite distorted, don't know why

[@johnb5519]

So would that be speaker blowing power when it goes into clipping?

[@12voltvids]

No because the transformer will remove the sharp edges that blow the speakers. So these may not be the best sounding but they are relatively safe to speakers.

[@ВалераПетренчук-з1н]

Здравствуйте у меня что то похожее, покажите как правильно его подключить по проводам!

[@keithking1985]

my brother had the very same booster in an old Opal Cadet car,

[@SSSwilliams]

That is super cool👌

[@cosmocramer1004]

I like the details thanks

[@RobertDickens2002]

Ive never understood why they got away from something like this maybe theres a lot i don't understand but it just seems like such a waste to have interal amp running and not even using it.

[@basilsaverimuttu682]

My Aunty had one them in her old car!!!

[@ford1546]

funny that you show such a small amplifier and explain how it works. i have always liked such small hifi components whit ewualizer and Is it true that the sound goes in through those transformers? Will not the sound quality get worse? I am thinking of noise filter with transformer that is for rca. They always change the sound!

[@johncoops6897]

No, it isn't true that the sound goes in through those transformers. If you watch and listen to the video, he explains how it works.

[@SeanBZA]

Looks like the bias is a really poor arrangement, no bias temperature compensation, as the bias current decreases as the heatsinks cool down. Really odd design for sure, but I guess they just wanted to keep the size of that coupling capacitor down, as you would normally use that style of transformer as an autotransformer to allow the drive stage to have a 0.5R load and have a voltage step up in the transformer to drive the 4R speaker load. That though would need at least 10 000uF to get impedance low enough for the lower notes. Here the capacitor just has to handle the mid range better, though I would guess the distortion would bepretty high, probably around 10% all the way from low to just before clipping, but in the typical car with a lot of ambient noise not too noticeable. I used one of those boosters for years as PC amplifier, though that had the regular 4 power amplifier arrangement as a bridge arrangement, using 2 stereo SIL Sanken IC's to do the actual amplification. Had to replace the coupling and power supply capacitors, as they had failed, previous owner obviously connected power in reverse, blowing the protection diode, though the IC chips miraculously survived, must have actually wired in a fuse, then flipped it on auction. I paid dirt cheap for it though, under $3 IIRC, with some cheap speakers as well. Worked well enough for PC sound use, and ran from the 12V PSU rail as well, though I added an extra LC filter, as the built in one was pretty much useless.

[@GBOAF216]

I’ve still got one in its box, bought it way back when for my first car..... never fitted it.

[@tenmillionvolts]

Worth at least 80 bucks then. Word your advert right and the idiots will pay.

[@mcramp20]

Thank goodness not a Roadmaster POJ.

[@WApnj]

Dude.. your hands are all swelled up. are you OK?

[@Skibike69]

I have schematic and original owners manual for this unit

[@Skibike69]

I drove a pair of 6x9 3-way speakers and a DVC 8" sub with passive crossover coils using this booster in my 1984 Olds Delta 88 and got very decent sound for the time and for my very limited budget

[@Skibike69]

I still own this booster

[@SachinPatil-xz2wf]

Model 12-1955

[@SachinPatil-xz2wf]

Service Manuel

[@SachinPatil-xz2wf]

Model no

[@Skibike69]

12-1959

[@mickblackmore290]

Why don't you turn the volume down when testing so your not competing with it? Just way to loud. Really like your videos but sometimes.....

[@12voltvids]

Volume is not up, but the mic is sensitive.

[@johncarlotorrelino7064]

I need to GP-870ii

[@lukewebb96]

Just bought 2 for 10 bucks

[@jorgepavon9096]

Nike y tambien el diagrama

[@cecilmayers3429]

I wont sell mine 😊

[@rogerchurch3804]

a half amp draw on this amp dont play your music too much on this start your car fire bird battery charge lol!!

[@SachinPatil-xz2wf]

Model no sir

[@Skibike69]

12-1959

[@SachinPatil-xz2wf]

Service Manuel PDF

[@coldfinger459sub0]

I had one of them as a teenager.

[@jdmccorful]

Interesting lesson.