Refurbished Carver C-1 preamp / wanted to share

[Tripqzon]

For the past month or so I've been spending a lot of my free time working on my C-1 2 channel preamp. I got the itch to refurbish it due to spending time at the Carver forum http://thecarversite.com/. For that I'm extremely thankful. There are a few members there that have answered questions I've had regarding upgrading this unit. I was especially encouraged when reading some of BillD's threads and seeing what he could do with this really decent preamp. RichP's test measurements of Bill's modded unit also gave me that extra nudge I needed to get serious about this project. And I do mean project.

First off, let me start with a little history:

I purchased my C-1 used on Ebay a few years ago (don't remember exactly when) and it was my primary preamp for a couple of years after that. I used it with an NAD 2200PE power amp. I've always liked this preamp because of it's flexibility and numerous inputs. I always thought it sounded good but knew it was capable of being better. I just couldn't see spending money on it because of its age and cheap selling prices on the auction site.

About 3 years ago I purchased an RSP-1 preamp because I had upgraditus and felt that I was missing something. I was right. The RSP-1 had a fuller midrange and just sounded smoother overall. Plus the remote control functionality was a nice bonus.

Anyway, back to the subject of this thread.

I recapped the C-1 a year or so ago. I used Panasonic FC caps throughout and replaced the IC7 with OPA2134's on a Brown Dog adapter. I didn't use bipolar caps in the signal path because at the time I didn't want to question the designer. After all, who knows better than the person that designed the equipment?

Well thanks to BillD I've replaced the caps in the power supply section with Nichicon HE caps and the signal path caps with Nichicon ES's. There was a noticeable improvement in clarity from replacing the polarized Panasonic FC's with the Nichicon ES bipolar's. Now I was hooked. I decided I was going to replace the resistors in the signal path as well. Bill recommended 1% metal film resistors. I replaced those and liked the results. At that point I was like a drug addict going through withdrawal. I had to do more. I made the commitment to replace most if not all the resistors in my C-1 with 1% metal film resistors hoping to reap the benefits of the low noise and tighter tolerance of metal film resistors.

I'm finally to the point, after replacing over 230 resistors and the above mentioned capacitors, where I only have a few straggler resistors to replace, mostly due to my error in ordering parts. I also have a Brown Dog adapter on it's way with OPA2134's mounted on it for the phono stage (IC6), for which I've socketed for quick swap out when it does arrive.

Unfortunately I can't get accurate noise levels because the noise floor of my sound card does not go low enough. I can say though that my sound card displays a noise level of -105dB. So if I'm correct the noise level of the line level inputs must be at least that low. The MM phono input is measurable at -100dB. That's with the RC4136 op amp.


Below are photos of the nearly completed and excellent sounding C-1.

Below are images of the Sonic Holography circuit operation before and after the refurbish. As you can see from the image in the service manual the SH circuit was not functioning properly. There were some definite issues with the timing delay. The following images only show the results of the "Both Channels Driven" tests and "One Channel" Driven tests. The "Undriven Channel" tests were just as good I just had a brain fart and forgot to record them.


The following image is from the service manual.

The following image is the SH circuit before I replaced all the resistors with 1% metal films.

The following image is SH circuit after the 1% metal film upgrade.

 

[Tripqzon]

I finally got the remainder of the 1% metal film resistors installed. Only one carbon film resistor remains. It is in the power supply section across the transformer primary and the center tap of the secondary side. It measures exactly its value so I saw no reason to replace it. I will probably order it when I place an order for another project but for now it remains.

I installed Polystyrene capacitors in place of the ceramic discs in the Phono, Line and Tone sections. I had no tubing small enough to cover the leads on the styrene capacitors so I improvised and used the green covering from tie wraps I had. I just peeled the covering off of a length of tie wrap, cut the number of pieces I needed to length and slid them over the leads of the styrene capacitors. The side of the capacitors closest to the circuit board have no green covering because I used a heat sink on that side while soldering. I didn't want to chance overheating the styrene caps. They can be very easily damaged during soldering if too much heat is applied or you hold the soldering iron on them too long. You can actually melt the shell of these capacitors.

All other capacitors were replaced with Nichicon HE, Nichicon Muse and Panasonic FC series capacitors.

The Brown Dog adapters with OPA2134 op amps have replaced the original RC4136's in the Phono and Line stages. I did not change the green Mylar capacitors because they stay reliable with age and drift is not an issue with them.

All components, with the exception of the two Brown Dog op amp adapters (http://cimarrontechnology.com/) used in the Phono and line stages, are from Mouser Electronics (http://www.mouser.com). Total cost of parts was just under $80.00. The Brown Dog adapters with op amps installed were almost half of that cost. Hence the reason I didn't replace all of the RC4136's.

I also replaced the red "Power" indicator LED with a blue one. I did this for two reasons. 1) So it would fit in better with the Emotiva gear and 2) because I think blue LED's look really cool.

This is what can happen when I have too much time on my hands. It's a good thing I only have one gallbladder. LOL! I used the time off from work after my surgery to tackle this project.

Now I can just kick back and enjoy the fruits of my efforts.

Without further ado, the photos of the completed C-1.


FULL INTERNAL NUDY

PHONO and LINE sections

SONIC HOLOGRAPHY section

POWER SUPPLY, HEADPHONE, and TONE sections

CURRENT SETUP (my apologies for the noisy system photo. Can't seem to get the lighting correct today)

 

[Fasterdamnit]

Nice work!!

:thmbsp:

I love hot rodding good audio gear. It is not expensive and the results are very satisfying.

How did you decide which cap series to put in which place?

 

[Tripqzon]

I chose based on information I read here on AK and other forums. I'm really not well versed on all the benefits of different capacitor series. I trust the folks that do this stuff on a regular basis and go with their recommendations. Sorry I can't be more helpful than that.

 

[BinaryMike]

Just wondering... Why were all those polyester chiclet caps left in place?

 

[Tripqzon]

I was told and also read that mylars are very stable and don't have a tendency to drift with age. Is there a reason I should be replacing them?

 

[DCinDC]

I would replace the green mylars. They are just kinda crappy. Take it to the nth level and replace all those making it really nice!

I love doing what you've done here. The only problem is that at resale, no one will pay for your skill or time.

:thumbs:

 

[djnagle]

I have a C6 that I have been thinking of referbing. Watching this with interest.

 

[Tripqzon]

I would replace the green mylars. They are just kinda crappy. Take it to the nth level and replace all those making it really nice!

I love doing what you've done here. The only problem is that at resale, no one will pay for your skill or time.

:thumbs:

Can you please explain what you mean by the mylars being crappy?

I understand what you mean about resale value. That is not really an issue for me as I don't plan to sell this preamp. It is very versatile and has all the feature I want in a preamp.

 

[jazzman53]

Fantastic job, Tripqzon :thmbsp:

Modding gets in your blood, doesn't it? I recapped my C1 a while back too. But reading your thread makes me want to open the old girl up and do some more mods. A C1 is built like a tank and it's a solid performer too, in my book.

One thing to be mindful of whenever replacing the cover after servicing a C1 is that the cover screws can cut into the sheet metal and drop metal shavings onto the mother board and/or into the pots and cause a short. RichP over at the CarverSite pointed this out to me when I did my recap. It's a good idea to put a dab of petroleum jelly on the screws to trap any metal particles that might otherwise fall onto the board.

Good show!

 

[Tripqzon]

Good tip jazzman. I also saw that post by RichP. A good thing for anyone working on a C-1 to be mindful of.

By the way, I believe the speakers you're standing next to are home brew? Is that correct. Fantastic job on those by the way. I would never have the nerve to tackle something like that. I tip my hat to you.

 

[Tripqzon]

I have a C6 that I have been thinking of referbing. Watching this with interest.

Let me just say that all the work and time I put into it was worth it. I've been listening to the C-1 every day since doing the refurb and I'm really enjoying it.

 

[jazzman53]

By the way, I believe the speakers you're standing next to are home brew?

Yes, those are home brewed hybrid electrostats. The signature under my user name links to my ESL website, which gives a full description of those speakers along with a ton of information, photos, etc... on building DIY ESL's.

 

[Tripqzon]

I will definitely check that out. :thmbsp:

 

[DCinDC]

Can you please explain what you mean by the mylars being crappy?

I'm just thinking you went to the trouble to replace the resistors, I'd put some nice films in there in place of those greenies. I buy those in bulk to fix things, but not improve them.

great job on it!

 

[Tripqzon]

Thanks for the kind words.

I did consider replacing the mylars and I still may in the future. It could be something to do this winter when I'm sitting around the house. I'm not real crazy about the way they look, sitting crooked and such. It would really top off the refurb to have some nice films in there that actually sit straight on the board.

 

[JBL GUY]

Great job!

Thanks for the run down and the pictures.

 

[Bobby1970]

For the past month or so I've been spending a lot of my free time working on my C-1 2 channel preamp. I got the itch to refurbish it due to spending time at the Carver forum http://thecarversite.com/. For that I'm extremely thankful. There are a few members there that have answered questions I've had regarding upgrading this unit. I was especially encouraged when reading some of BillD's threads and seeing what he could do with this really decent preamp. RichP's test measurements of Bill's modded unit also gave me that extra nudge I needed to get serious about this project. And I do mean project.

First off, let me start with a little history:

I purchased my C-1 used on Ebay a few years ago (don't remember exactly when) and it was my primary preamp for a couple of years after that. I used it with an NAD 2200PE power amp. I've always liked this preamp because of it's flexibility and numerous inputs. I always thought it sounded good but knew it was capable of being better. I just couldn't see spending money on it because of its age and cheap selling prices on the auction site.

About 3 years ago I purchased an RSP-1 preamp because I had upgraditus and felt that I was missing something. I was right. The RSP-1 had a fuller midrange and just sounded smoother overall. Plus the remote control functionality was a nice bonus.

Anyway, back to the subject of this thread.

I recapped the C-1 a year or so ago. I used Panasonic FC caps throughout and replaced the IC7 with OPA2134's on a Brown Dog adapter. I didn't use bipolar caps in the signal path because at the time I didn't want to question the designer. After all, who knows better than the person that designed the equipment?

Well thanks to BillD I've replaced the caps in the power supply section with Nichicon HE caps and the signal path caps with Nichicon ES's. There was a noticeable improvement in clarity from replacing the polarized Panasonic FC's with the Nichicon ES bipolar's. Now I was hooked. I decided I was going to replace the resistors in the signal path as well. Bill recommended 1% metal film resistors. I replaced those and liked the results. At that point I was like a drug addict going through withdrawal. I had to do more. I made the commitment to replace most if not all the resistors in my C-1 with 1% metal film resistors hoping to reap the benefits of the low noise and tighter tolerance of metal film resistors.

I'm finally to the point, after replacing over 230 resistors and the above mentioned capacitors, where I only have a few straggler resistors to replace, mostly due to my error in ordering parts. I also have a Brown Dog adapter on it's way with OPA2134's mounted on it for the phono stage (IC6), for which I've socketed for quick swap out when it does arrive.

Unfortunately I can't get accurate noise levels because the noise floor of my sound card does not go low enough. I can say though that my sound card displays a noise level of -105dB. So if I'm correct the noise level of the line level inputs must be at least that low. The MM phono input is measurable at -100dB. That's with the RC4136 op amp.


Below are photos of the nearly completed and excellent sounding C-1.

Below are images of the Sonic Holography circuit operation before and after the refurbish. As you can see from the image in the service manual the SH circuit was not functioning properly. There were some definite issues with the timing delay. The following images only show the results of the "Both Channels Driven" tests and "One Channel" Driven tests. The "Undriven Channel" tests were just as good I just had a brain fart and forgot to record them.


The following image is from the service manual.

The following image is the SH circuit before I replaced all the resistors with 1% metal films.

The following image is SH circuit after the 1% metal film upgrade.

 

[Bobby1970]

Greetings Tripqzon, i have read your Carver C1 restoration project and i loved it so much how the way you spend time restoring the product. I am 48 years old living in the Philippines

I finally got the remainder of the 1% metal film resistors installed. Only one carbon film resistor remains. It is in the power supply section across the transformer primary and the center tap of the secondary side. It measures exactly its value so I saw no reason to replace it. I will probably order it when I place an order for another project but for now it remains.

I installed Polystyrene capacitors in place of the ceramic discs in the Phono, Line and Tone sections. I had no tubing small enough to cover the leads on the styrene capacitors so I improvised and used the green covering from tie wraps I had. I just peeled the covering off of a length of tie wrap, cut the number of pieces I needed to length and slid them over the leads of the styrene capacitors. The side of the capacitors closest to the circuit board have no green covering because I used a heat sink on that side while soldering. I didn't want to chance overheating the styrene caps. They can be very easily damaged during soldering if too much heat is applied or you hold the soldering iron on them too long. You can actually melt the shell of these capacitors.

All other capacitors were replaced with Nichicon HE, Nichicon Muse and Panasonic FC series capacitors.

The Brown Dog adapters with OPA2134 op amps have replaced the original RC4136's in the Phono and Line stages. I did not change the green Mylar capacitors because they stay reliable with age and drift is not an issue with them.

All components, with the exception of the two Brown Dog op amp adapters (http://cimarrontechnology.com/) used in the Phono and line stages, are from Mouser Electronics (http://www.mouser.com). Total cost of parts was just under $80.00. The Brown Dog adapters with op amps installed were almost half of that cost. Hence the reason I didn't replace all of the RC4136's.

I also replaced the red "Power" indicator LED with a blue one. I did this for two reasons. 1) So it would fit in better with the Emotiva gear and 2) because I think blue LED's look really cool.

This is what can happen when I have too much time on my hands. It's a good thing I only have one gallbladder. LOL! I used the time off from work after my surgery to tackle this project.

Now I can just kick back and enjoy the fruits of my efforts.

Without further ado, the photos of the completed C-1.


FULL INTERNAL NUDY

PHONO and LINE sections

SONIC HOLOGRAPHY section

POWER SUPPLY, HEADPHONE, and TONE sections

CURRENT SETUP (my apologies for the noisy system photo. Can't seem to get the lighting correct today)

Greetings Tripqzon, I have read your page regarding this C1 project and I really appreciated all the efforts you put into it. I am 48 years living in the Philippines and the reason I am writing is that I want to ask if you have a list of all the parts you used for the project. I still go to work and I want to slowly purchase every parts involved and solder them inside. I also have a M1.5t that I would like to work on in the future ( should my budget allow me ). Thanking you in advance - Bobby

 

[Tripqzon]

Greetings Tripqzon, i have read your Carver C1 restoration project and i loved it so much how the way you spend time restoring the product. I am 48 years old living in the Philippines

Thanks Bobby1970. I am still enjoying this C-1 very much. I was hot to get a Pioneer C-21 for a long time but the prices for a clean unit are, imo, ridiculous. I honestly don't think my old, 54 year old ear, would hear enough of a difference to warrant the purchase. Younger ears would probably hear it, especially the phono stage, which is one of the high points of the C-21. I rarely play vinyl anymore.