RPS,

Thanks for the detailed information on parts and their part numbers. This will help me greatly as I decide how to proceed with the updates. After 42 years, I think a refresh is in order.

I'm humbled by your very generous offer to provide me with some great music to evaluate with the C9 in my system and room. This sounds like a great opportunity!
I'd be more than willing to review the music/sound and post the results here. I'm not exactly the best reviewer or writer but I think it would be fun and hopefully provide some insight to others who may be curious about the C9.
I will reach out after the holidays for sure. Thanks much!

Even though I can't set up my listening environment as the manual describes, I agree with you that one needs to try all the options on the C9 to hear what is best for their situation. With a reasonable amount of room treatment and a little work to tweak what you can with the room setup, I was able to achieve a really nice expansive soundstage that sounds very natural. It took the Decware sound to the next level. On some tracks it's a small improvement, but on others it's very obvious and very realistic. It just takes time to set the switches, listen for a while (hours/days/etc.) and then change the settings and rinse and repeat. It will be obvious at some point.

I'm also with you in the fact that it didn't take me long to hear the difference the C9 made. It was pretty much immediate, just like in your case. Maybe it's the treatment or the work I had already put in to get the speakers just right, but whatever it was, it was pretty obvious from the get-go. I'm just glad I was able to get a very big improvement even though my speaker placement couldn't be changed. (I wasn't expecting that since the manual stated multiple times 'to follow the speaker setup and listening seat exactly'.) Granted, I'm not getting the true 3D spatial sound, but I'm very, very pleased with the sound I'm getting.

Thanks for the link to the Carver video. It was humorous, cheesy, and insightful at the same time.

I too will be interested to see where this journey leads for you, JB, and I as well as any others who choose to hear what the C9 can do for their listening enjoyment.

JB,

Thanks for the pictures of the inside of your particular unit. Very interesting to see the differences in the layout.


Here's wishing you, JB, all the Decware family as well as the forumites a very Merry Christmas, New Year, and holiday season. Enjoy it y'all.

 It occurred to me that I could add a bit more information about the rebuild. Specifically, what drew me into this whole idea were the original RCA jacks used for the unit. Since they are recessed, it can be difficult to use just any interconnects. They must have skinny barrels or else they don't fit into the RCA jack. I didn't like that at all, and looked inside to see what could be done. It took a lot of experimentation to find RCA jacks that mount to the chassis and not the circuit board  itself. I ended up using Manley Labs RCA jacks and have done it that way for years. Well, since we are now inside the unit, it is a good time to take a look at the electrolytic capacitors seeing how they are 30+ years old. There are a total of 10, and it doesn't cost that much to just replace them with new and probably better caps. Of course that led to other stuff, namely the power supply. I realize that it is only needs to be tiny, but I was into replacing two of the 4136 chips with military models which happen to draw more current. FWIW, the 4136 Texas Instrument chips (there are 5) used in this unit have an unusual pinout, making the use of an adapter for other chips such as the 2134 which is a more modern version of quad amp. Yup, tried this out, with the help of a 'Brown Dog' adapter with pre-mounted with SMD chips from yes, the company named Brown Dog. This will set you back about $35 per chip replacement. Is it worth it? Not so much in my opinion, so I went with trying to find a better 4136 chip, and that is when I discovered the metal jacketed military chip that usually runs about $20 per chip if you can find them. I only have two left at this time. They sound slightly better than the originals, but hell, we are racing cars here so every little bit helps.
I have replaced numerous other components, but will tell you that each one in its own is not likely to make any difference either. From what I have gathered, replacing those two transistors is of little value since they don't amplify but just pass the signal through upon turn on just to eliminate the turn on thump.
I have tried just about anything that you can imagine, including using a battery power supply to using a separate power supply, to well, name it. Really. In the end this is where I have ended up. Like I said in the first post a rebuild of an existing unit sent to me runs around $125, and if I get the right price on eBay for a used unit, $250 is the selling price. As expected these units have become popular, and for a while people out there were selling them as reworked/tested/rebuilt/improved. This usually meant that the little red light cam on when plugged in and nothing more. If they did show the inside, I was immediately able to tell if they were ever taken apart or not. Maybe I will give up that secret later, depending on the interest of these units, and yes, they are truly worth having in a system. Many other brands have attempted in various ways to replicate this audio illusion and I have listened to a number of them. This unit by far and away the best.

4krow,

Thanks for all the details and information regarding the C9. Very informative and nice pics as well. I am considering getting my unit refreshed and updated, especially the RCA's. This is very intriguing.

Don't get too excited about the first photo with rack handles. I am still trying to convince the guy who makes these new front panels with handles to make more of them. And of course, they aren't cheap at nearly $100 extra, but you have to admit they are pretty (and accurate logo and lettering too).
You will notice that I didn't change out the transformer in that unit either. It was enough cost to my customer that he chose the front panel but not a new transformer. These days, I am not so flexible and so a new transformer is automatic with the rebuild price.

Donnie I found these which I think attempt with some success to explain the device:

https://www.highfidelityreview.com/carver-c9.html

http://www.magneticmadness.com/2017/02/carver-c-9-sonic-hologram-generator.html

Donnie,

My understanding is that the Carver C9 attempts to eliminate or minimize inter-aural crosstalk. It tries to prevent your left ear from hearing sounds from the right speaker that it shouldn't be hearing and vice versa. It basically sends an additional signal (along with the left speaker's normal signal) to cancel out sounds from the right speaker that would confuse the brain. I think like an inverted phase of that signal. I don't understand the technical details, but it does more than just that and there are delay considerations as well. It does not add echo or anything like that, in fact, it's what it takes away (inter-aural crosstalk) in terms of correcting what stereo should actually sound like. It tries to restore the reality in live and real-life music and sounds. Normal stereo can sound really good but the C9 brings it more into true perspective. When your left ear hears an instrument from the left speaker, it is also potentially hearing it from the right speaker as well (depending on the recording) but a few milliseconds later. This confuses the brain a little but the C9 will counter that particular signal and allow you to hear it in the proper context. You still get the phantom center channel (when it's there) and it also allows you to hear the various instruments/voices coming from the various locations while still maintaining proper reverberation as it moves through the room. It brings the instruments into focus in their own space and creates an even more convincingly wide soundstage. I hope I'm making sense here, so someone please correct me if I'm wrong or I'm missing important information.

The thing is, if you read the manual, it highlights the fact that you MUST follow the setup exactly or you won't benefit from the full effect that the C9 has to offer. It wants you to pull the speakers out and close together (maybe no more than 5' apart center cone to center cone) with precise distance to the listener, etc. Doing this is supposed to give you a fantastic 3D sound stage in all its glory. (if it's in the recording.... Classical music doesn't lend itself so much to this though)

Because of my room and setup, I am unable to conform to the 'correct' arrangement described in the manual. I am however able to get a great effect from the C9 regardless. (to my surprise actually) I thought without the ability to setup the speakers and listening chair just so, I would not benefit much from the C9. I couldn't have been more wrong. I don't get the 3D sound all around me, or things behind me, or sounds circling around my head, but I get a very realistic and expansive soundstage. It brings the great Decware sound to the next level for me. I don't know if others would get the same results without moving their speakers or putting in at least some modest room treatment, but if you have your room as good as it can sound in stereo, then I'm willing to bet you would benefit to a good degree with the C9. Maybe it's my unique room, acoustics, setup, I don't know, but I'm really liking what I'm hearing.

I hope this helps and doesn't confuse anyone.

4krow,

Please take a look on page 5 starting at reply #239. It attempts to show the circumvented fuse, the iffy soldering to the spare receptacle, and the current state of the transformer. Reply #241 shows the full board (albeit at a distance). If you would like more or different pictures just let me know.

It also looks like the 4 large yellow caps have been replaced at some point, but I don't know for sure. Looking at the latest schematic for the latest Rev (F) it shows that two caps should be 16V and two should be 25V. It looks like all 4 of those yellow caps are 16V. Maybe it's because my unit (#606) being part of the original builds only called for 16V. Just wanted to point that out in case it matters.

As of 1400hrs eastern time today(1/4/25), there are THREE Carver C9 units for sale on Ebay at a very good price.

For anyone wanting one, this is a great opportunity to snag one.   One unit under $150.00!

 People, for what these units do for your music, this unit is valued much higher than a ridiculously low price like that. I would gladly pay upwards of $1000 or more for a new unit like this to have something this good in my system. (IT IS ABSOLUTELY WORTH IT!)

If you don't understand why, then perhaps you need to do your homework, or better yet, get one and find out instantly why.

It won't be long before the resurgence of the C9 popularity drastically increases the price due to demand. It is already happening. Get one now while they are still cheap, and still available.

Just the messenger here, you will thank me later.





WAIT...now there are only TWO units for sale on Ebay.   I just bought another unit for only $149.00

This unit is newer than the one I already have. Very good condition and in great working order. It looks untouched and factory original.

Hurry...two left....maybe??

Thanks for the info 4krow.  I could not find the link, can you provide a link or the search term you used?

Go to Black Ice Audio. Sorry Music Direct doesn't carry it anymore. Second photo is of the remote controlled C-9.

This is a subject that i could discuss all day long. In fact, it does remind me of a site that is focused just on the C-9 itself and many recordings that are perfect for it. Give me some time to remember the name of that site. As it happened, I got to rebuild a unit for the 'top guy' of the site and found humbling in its own way, and pride as well to have been asked.
It is true. The C-9 unit uses cross cancelation, a bit of delay, and a slight bit of frequency EQ. As to the amount used depends on the buttons depressed/selected. Maybe we will go more into that at a later time.
I am thinking that it was around 1985 before I ever heard a C-9, and like many out there, was hooked from that moment on (at least when a recording called for its enhancement). It was Bob Carver's best selling product ever, and even wins by an edge over the units that had it built in. I cannot give a good reason why but hearing is believing. The C-9 is top dog.

Of course you mean Carver as in Bob, and not Carter as in Jimmy. A little humor, yet they were both buzz words back in the day.
Pioneer made a Spec 1 power amp that I had, which was an introduction to great sound. Bose? Nah, I went for Kits by Speaker Lab in Washington state after Boing took a dive. built their corner horns. Didn't think ahead about moving back then.
Reconsidering the doppler effect as you use it, gives some merit for Wikipedia after all.
The transformer in the C-9 is probably 150-200 ma. I upped the transformer to a 400 ma size and it barely fits. I think that split bobbin design would be an interesting go for not transferring RFI by way of its design, whereas the toroid designs are prone to that as I understand it.
Some supplies are being delivered this week for my inventory to be complete for yet another rebuild. This time of year is tricky though with holidays adding to backloaded suppliers.

Now that I just finished spending my afternoon shoveling a foot deep of heavy snow from my 40 ft driveway, and the sidewalk in front of my house, I can actually get on here and reply.  My joints are enduring a bit of pain now as a result. At my age, this is not the thing I want to spend my day doing. I will bear through it, as my mind always gets me through the tough spots. I still think that I am 30 years old physically! I think I will relocate back south...LOL   This is why they make Crown Royal....and that just may come in handy tonight.




So anyway,


Of course you mean Carver as in Bob, and not Carter as in Jimmy. A little humor, yet they were both buzz words back in the day.

Well, maybe JB actually thought Jimmy created the C9?



Can't remember much of anything else worthwhile that he did other than the Habitat For Humanity project....but that is another story. I began my military service at the same time Jimmy went out the door. You could not buy a real job back in 1979 and 1980. I had no choice but to enlist. Either that or become homeless.   F*** THAT!  The military created a path to my future, and I am a better man for it.   So thanks Jimmy...rest in peace. Every time that I listen with the C9, I will be thinking of you.



Alright, no more ragging on JB, he has been having a hard time with all of that work he is doing.  Get 'r done  JB.



The kits includes a core wound with the primary wire and insulation. A manual is included with all the info needed to add magnet wire for custom secondaries.

Thanks JB.  This won't be necessary since 4krow was generous enough to share information about the C9 upgrades including a good source for the transformer which has a very low price. Since he has strong experience with the C9 circuit, and he knows what works well, I am going to go with his choice and see how it goes. I can always change it later if desired.

Thanks for that info Greg.


I am very pleased that 4krow has joined in here as he is a valuable source of information and help.  I hope that he gets more business due to this thread. I also hope that he can influence others just how good this unit is, and how crucial it is in a system.

I did note that someone bought the second of the three C9's on Ebay, the one from NYC.  Just wondering if it was a member here?

That last unit is an early model with the rack mount notches like the one mrchipster bought.  Seems to still be there for sale.

I now have two of the late model units, my current being a '86 model, and the one I just bought, most likely a '87 model due to the much higher serial number.  One will always be in the system while the other is undergoing upgrades, and repopulating of the board components. I need to strip down one of these circuit boards anyway to perform some backwards engineering.  It will be rebuilt with all new components, much higher quality than original.

I do have a quandary concerning upgrades to the switches.

Greg, perhaps you could shed some light on this. I know that this mod has been done before, and I would like to do the same with my new build.

I do not like the limited output of the push switches. It makes so much more sense to have stepped attenuation for precise control for each of the controls (injection ratio and aperture). By tracing the circuits for each mode under the 3 key push switches, I assume that a DPDT 6 pin (ON_ON) toggle switch would work for basic switch upgrades.  Please inform as that being correct based upon your experience.


But, it will take rotary stepped attenuation in order to accomplish the task as I want to engineer it for flexible fine tuning.

What is your take on making this happen?  Could you shed some light as to making this work?  It would help to know a part that works well for this, and of course, having a diagram as to the wiring for a C9 installation.

If this becomes too complex, I will just remain with a chassis mount push switch, again thinking that a DPDT (ON_ON) 6 pin toggle switch would work for this.  Please inform if this is incorrect.

*Note:  I am not just rebuilding a current C9. I am building a new design which has a different component layout. This will either be point to point, or built onto a PCB.  My plan is to integrate this circuit along with a new DAC circuit inside of the same chassis. The original C9 layout is only for reference.

I noticed that you installed two of the resistors with high grade 1 percent metal types. Obviously, you have found this upgrade to be audibly beneficial. By any chance, are these two resistors for R121 & R122?  Those are the ones located near the HOLOGRAM INPUT switch.

What improvement did you hear from this?  I am going to use all 1 and 2 percent resistors for my build anyway. I am using mostly Vishay metal film for mine.

Because OSCON (Sanyo/Panasonic) type electrolytic capacitors have a good reputation for sound quality in DAC circuits, I am thinking about using these in the power supply.  Have you tried other capacitance variations with this circuit, and if so, what do you recommend? Your choice of transformer replacement seems to be a viable one, so that seems to be the option to use. The cost of toroid types are very expensive, so have to wonder if they are worth it for this application?

Also, do the Vishay high speed rectifiers actually make a noticeable difference with this circuit over the standard ones used originally? I see that they claim to have less "bleed-back" in the reverse direction, which is something that makes good sense as to the outcome, but these are for very high frequency applications where this type is required.  I don't see that being much of a need for this unit, but they are much better than stock, so might as well upgrade with them.  They are cheap and readily available at Mouser, so it would be foolish not to use them.  Just wondering if this actually makes a noticeable difference audibly.

Anyway, any guidance you can provide me on this would be helpful and much appreciated.

I do have a mystery for a couple of resistor values in relation to the pins on one of the IC's. I can't identify them in the circuit schematic. I will have to crop that section and show you the two mystery values sometime later.

 Just wondering if you can identify these values and solve this mystery.  Other than that, the schematic is easy to follow, just very hard to see some of the layout due to poor print quality.  I could locate these on the CB, but I don't want to mess with the current C9 in my system now. It would be easier if someone like yourself could identify these resistors and confirm the actual values. Not many people would know this unless you service these units.

If you think that you can identify these, please let me know, and I will show you the locations in question.  

Otherwise, I will have to identify them on the actual board, and determine the values there by the value markings.  It really seems strange that these two are so unclear. Either they were forgotten in the schematic drawing, or perhaps a change was made. I need to figure this out. There does seem to be some disagreement between the parts list values, and what the schematic shows. Seems someone made an error here, or perhaps not.

If you are not comfortable divulging this information, I understand. Thought I would ask since you are the expert on rebuilding the C9.

Thanks for your help.

And BTW: Since you ragged on JB about Carter, you left out the "E" in Boeing.......just messing with you. But I thought it was funny what you said. I assume you meant Boeing?

As for the "Doppler" reference, I think that needs to be avoided, as to not confuse people anymore on how this circuit works. It is complex enough for making people understand exactly what it really is, so let's stick with Bob's white papers on this technology. This would be helpful for this thread.

Thanks.







As for the last post,

Ok, so I remembered the FB Carver Sonic Holography group, started by John Smallwood. The best thing about this site/group is that they know pretty well what recording really respond to the C-9 unit.



Sure, as I myself have learned through experience many (about 90 percent of my library) very interesting sound tracks which make this unit noteworthy to say the least.  The discs that I sent mrchipster are going to be very enlightening to him as to just how much these recordings come into play using the C9. It will be very interesting to hear his thoughts about these.

Thanks for posting that information.

I will gladly share any information about the C-9 and my experience with it. You all couldn't be more welcome for showing such interest in a product that got swept under the rug due to the advent of the Home Theater rage.
As a lot of you have already done, going to the Carver Site will give free downloads for the owners and service manual. That is just the tip of the iceberg folks. There are many pages of information about the circuit, one notable 'upgrade' was called the RichP modification. It is a little tongue in cheek since it was suggested that Rich was adopting the C-9 to HIS particular system and not for all the world to emulate. It does back off the bass a bit and change one of the high frequency filter points. In this line of thinking, it could noted that Carver himself (not Jimmy or Billy) made a slight change to the first rack mounted unit concerning delay IIRC, in which the second unit circuit incorporated.
Let me review the last post with the questions and points and get back with an answer.
FWIW, I was the one who bought the C-9 on eBay for $145 + 10 for shipping. I will be working on it sometime next week, but AFTER the rebuilding of yet another unit. One at a time. And the beat goes on. Are you sure that they shouldn't be called 'Boing?'

Before I offer information here, I want to be clear about something. I am a builder, not an engineer. I have to rely on others to compile information and then try it for myself. In some cases, I have made my own changes that resulted in a sound that I still stand behind, but that may be the exception.
How far someone may want to go with a complete rebuild, meaning change out every single part on the board including switches, go ahead. I have done that too, and found no viable reason to do it again. Did it sound better? probably, in some sort of minuscule way. Ok, so here is a list of what i have info about the last posted questions:
1) Look inside of the chassis to get a quality assurance date. Then you have a good idea when the unit was actually built.
2) DPDT will work fine for switches. just make sure to get a quality switch with maybe silver contacts.
3) An attenuator may work, but I really can't say for sure. I applaud the idea but have never done so myself.
4) Contact 'jeffs' at the Carver Site for the best information about building your own unit. After all, he has already made 6 of them.
5) SF4007 diodes are the replacement that I chose for the rectifying bridge because they are a higher quality and faster diode. Now this won't matter so much with 4136 chips but it may if you decide to use 2134 chips instead. in the end, I see no reason not to use them.
6) .1 uf bypass caps are there for RFI reduction. These days, I wouldn't think of not using them.
7) Do these things ADD UP to better sound? Not each individually but in concert together, I think that the units sound a little better, but certainly not worse. After all, since you are in there, I see nothing wrong with replacing parts with higher tolerance parts in order to 'tighten up' the circuit.
8) Schematics, parts diagrams, part lists and much more are available for anyone at the Carver Site.
No doubt, you will see parts that don't add up in some units and I just stick with the schematics/parts list. You will find the component location diagram to be indispensable for unknown or uncertain values and of course the circuit board tells all.

RPS,

I enjoyed reading this latest post today. You have the right spirit. Sure enough, the C-9 is just simple enough for me not to get very worried about even if something were to 'pop'. I will take in a non working C-9 sometimes and the fix is usually like needing a new transformer, or capacitor gone bad. It is actually rare that these have trouble.
Now on the other hand, the sometimes comes a unit that makes me wince, having been 'upgraded' all to hell. Nasty solder joints, 8 amp diodes (Really!) Traces being 'fixed' in the ugliest possible way, and even a couple of parts missing! I guess if you do something long enough, you are bound to have stories. I have made a few mistakes of my own, ending up with me staring at the circuit board until either I see it or I don't and get the meter out.
Yes, Bob did have plans in 2023 of remaking the C-9 and invited suggestions from members of the site. Frankly, I did not agree with ideas adding more circuitry and other odds and ends. The only thing that I suggested was a variable amount of SH using a volume control or some such. Well, that whole process just kind of died.
I admit, I am not much of a joiner myself, but it was the best way for me to start gathering information back in 2011? or something. I forget.
I am so glad that you found clearer schematics and such. What a pain it can be to try and read blotches. At this point, I have made laminated sheets for reference. Every so often I check to see which was a diode or something goes, even though I am 'sure'.
You might try to avoid using those new switches that are pushbutton types. I have had too much bad luck with even the German ones. When there is a popping that seems to be switch related, it can also be something else anyway. In the big picture, it is likely that the pop you hear is tiny and does not occur when actual  listening to music takes places, so keep that in mind. A good toggle switch is the way to go I think if you are building your own. Remote control relays are the top of the heap for being able to switch from the listening position, but that kind of stuff has to be spelled out pretty cleanly for a guy like me.
What chassis have you considered/ There are a mountain of choices... most of them , meh.

Alright, here is the very well explained block diagram that shows precisely how the C9 holography circuit works using inter-aural signal cancellation through means of time delay, signal inversion, and EQ tailoring to get the corrected output within your stereo speakers as you should be hearing them.








Here is a better defined image of the CB layout. Detail is a bit more clear.









And here is a better image of the circuit schematic. It is the main circuit only. Power supply not shown.

This image shows section IC4 OPAMP point to point wiring connections. This is not 100 percent verified. Verification required before use.

I am still working on the remainder of the layout. I will post them when finished.


In the meantime, you might find the technology behind Bob's ALS line source speakers interesting. He took the C9 concept and applied it directly into the speaker design itself. He gives a very interesting lecture on how these work.




Here are some images of those speakers. If I could afford them, they would be mine!















Yes, those planar drivers look familiar. Been available at Parts Express for many years. In case you don't know, Bob designed those drivers and gave the rights to HiVi in China exclusively after three years of producing them for the speakers you see here. That was the trade off to keep Bob from paying out $100,000 up front for tooling costs just to get started. They are sold as Dayton Drivers, but made by HiVi.   I have a bunch of these new in the box.