Carvin Rebuild- Project assistance request

[silverfox]

I've posted some samples of how my MTS 3200 sounds vs. how I'd like it to sound. Essentially it is unusable without an amp modeling pedal. I want the sound of a Marshal but don't know how to mod the circuit. Perhaps something as simple as a Tone Stack change will work. In that regard, I would not know where to patch the new stack in or what values to try. I think it needs much more than that however. A master volume on the clean channel may also help but even that won't lead to a nice biting distortion. I've tried that by adding a mixer to the send and return chain which allowed for the maxing of the clean volume then turning down the output through the mixer into the return line.

The Lead channel is dark and muddy and the Reverb and Presence controls produce little change in effect or tone.

The circuit is mounted on a PC board and might have to be completely gutted and converted to point to point??

The other aspect and it's major- I'd like to convert the power amp section to stereo by adding a second power amp. The means to obtain this would be to remove the existing output section and using the parts available and purchasing additional parts- add (2) 35 to 40 watt output sections. Of course the input would be mono, but using an second line from a modeler I would generate the second channel.

The schematic for the Carvin is here: http://www.el34world.com/charts/Schematics/files/carvin/carvin_mts3200.pdf

and the sound bytes are here: http://minus.com/lbycrHD2d4TNLw

Please be advised regarding re tubing the amp, that has already been done with new tubes from Eurotubes.

Regarding the sound bytes- the first two samples are from the Clean channel and the Lead channel. The remaining samples are what I'm trying to get the amp to sound like. The were obtained by using a modeler into a Trace Elliot TVT-9 then plugging into the return line of the Carvin.

I suppose, if anyone is interested, the first step should be to mod the preamp to get a decent tone. Perhaps that would be the end of it all then and there.

Absent this the amp by itself is unusable. Only by plugging a modeler into the power amp, (return line) can I get a decent tone out of the amp.

There is an output switch that allows for selecting 50 (two tubes) or 100 (4 tubes) watts of output power. There are quite a few of the parts already there to build the amp. I should also mention the possibility of mixing 6L6 tubes with the EL34's but I don't know if that can be done or not. Two of each for a tone experiment in the end if this amp gets modded and the output converted to Stereo.

Finally, my experience level with electronics spans tens of years assembling circuits, testing systems etc... starting in 1978 and ending with the demise of the computer industry here in the states. I can read schematics and perform basic amp troubleshooting but nothing like some of the professionals here, which is why I joined. Looking for Mentos.. I mean Mentors...

Best regards,

Silverfox- Rockin out the Wilderness.

[TIMBO]

Hey Silverfox, Anything is possible when its comes to amp building/modding.I have only modded a couple of amps that used a PCB and both were a bitch to work on, so if you were to try and mod some of the circuit to achieve the sound you are looking for,it might take a lot of tweaking hours and PCB tracks are unforgiving when adding and removing parts.I don't know much about this amp as such

OR i think that it has plenty of useable parts to build a Marshall type amp but this also would require a lot of amp building skills.Look in the schem libaray for the marshall schems and compare to what you have and you will be able to see where they are similar. Good luck. 

[tubenit]

I would rip out the PCB board.  

In other words, I'd pretty much gut the amp & rebuild it into something I actually wanted eliminating all the solid state stuff that Carvin crams into their amps.  I'd put in my own turret board & design.

As much of a job as that sounds ......................  I think it may actually be less work and less frustration than trying to modify a PCB board.  

A friend of mine owns a JCM900 Marshall that did not sound very good to him, his band or me. In fact, it had been collecting dust and unusued for some time.    I gutted his amp and built it into a Plexi50w.  He did NOT tell his band that this had been done purposely to see if they would mention a tone difference.  First time that he jammed with them, they commented that his tone was so incredible and much better than previously & asked what he was doing different.

This was one of the first big amp projects I ever did yrs ago.  I think the total cost of rebuild was around $125-150 if I am remembering correctly.  Unfortunately, he wasn't wanting to spring for full sized pots and I was stuck using the PCB pots. Wiring was messy, but the amp sounds great and is quiet at idle.

Here is a picture of that amp:
http://s28.beta.photobucket.com/user/tubenit/media/CPlexi50chassisinteriordescription.jpg.html?sort=3&o=51#/user/tubenit/media/CPlexi50chassisinteriordescription.jpg.html?sort=3&o=51&_suid=135418905940006262767463437295

The best way I can describe the tonal change was from a muted/muddy sound to a very clear harmonically rich overdriven tone.

I heard his band live at a club a few months later after the rebuild.  The other guitarist had both a Mesa Boogie and a Fender Blues Deville that he played thru (depending on which song).   The difference in clarity between the Plexi 50w vs. the Mesa and Fender was astonishing. The Plexi 50w cut thru the mix just fantastic.  I watched the other guitarist continue to turn his amp up to try to hear it more clearly. All it did was make louder mud & the club owner told him to turn it back down.

I think if an amp has a clear (not necessarily clean) tone, that the overdriven tone can cut thru a mix SO much easier than a muted/muddy tone does.  My opinion (FWIW) is that some of the bands I've heard over the years that are too loud, have gotten too loud because the amp tone is not clear enough .................. so they keep turning up the volume.  Ugh!!!

I used to own a Carvin 33 watt amp & found the design to be problematic for what I wanted.

Nice guitar playing, BTW!

With respect, Tubenit

[ac427v]

Nice playing. But yeah, the tone...
I haven't heard the Carvin but I can't believe it sounded like that when new. It may need fixing rather than modding. Measuring the amp voltages and sharing with the forum would allow the folks here to compare to the proper voltages on the schematic and advise on possible repair problems.

But rebuilding from scratch is way more fun. I would be daunted by trying to duplicate all the features/controls of that amp in a turret board build. But if you could simplify your wants it would be fun to stick a Marshall circuit in there.
Craig

[tubenit]

And if you don't want to gut and rebuild the thing, there are some mods on this link that would apply to your amp also. Carvin tends to reproduce things like the clipping diodes and James tone stack in some of their models.

http://hasserl.com/vt50_mods

With respect, Tubenit

[OldHouseScott]

What tubenit said. You need to get in touch with Richard (username on various fora is Hasserl). He has come up with a set of mods that work wonders on the Vintage 50 series of amps. He has also, with somewhat less success (his own words), modded the MTS amps, but at least he has experience and can guide you toward your desired tone.

IMO, the clipping diodes and the bridge-T mid-cut filter are what is holding this amp back. I wouldn't bother trying to convert this amp to dual output, but I believe you can certainly mod it to get it closer to useable. You don't even have to gut it. First, remove those clipping diodes and replace with a resistor. You can change the tone stack to a Marshall style by removing the pots from the PCB, installing regular pots with tabs, and wiring the tone stack right on the pots. Then, remove all of the James tone stack components on the PCB. Move the tone stack to between V2A and the lead channel Volume, change some component values, and you're pretty close to a SLO/Recto topology. Or look at the Legacy lead channel for inspiration.

Hope that gives you some food for thought.

[Willabe]

The best way I can describe the tonal change was from a muted/muddy sound to a very clear harmonically rich overdriven tone.

I heard his band live at a club a few months later after the rebuild.  The other guitarist had both a Mesa Boogie and a Fender Blues Deville that he played thru (depending on which song).   The difference in clarity between the Plexi 50w vs. the Mesa and Fender was astonishing. The Plexi 50w cut thru the mix just fantastic.  I watched the other guitarist continue to turn his amp up to try to hear it more clearly. All it did was make louder mud & the club owner told him to turn it back down.

I think if an amp has a clear (not necessarily clean) tone, that the overdriven tone can cut thru a mix SO much easier than a muted/muddy tone does.  My opinion (FWIW) is that some of the bands I've heard over the years that are too loud, have gotten too loud because the amp tone is not clear enough .................. so they keep turning up the volume.  Ugh!!!

I think what tubenits saying is right on the money.

It can be said for tone controls on amps too. Need a little more chime/ring on the high end so you turn up the treble and all you get is harsh, nasty, ear cutting noise. Same for bass need a little more/fuller bottom end? So you turn up the bass and all you get is mud.


                Brad      

[silverfox]

Okay, this is a good start. Several options. The tone stack mod sounds interesting and I've seen the diode removal option on other posts. If I were to begin surgery at some point on the tone stack, can I count on reasonable assistance when it comes to determining the "changing of some components" in regards to inserting a new tone stack. The last thing I want is to end up with an: I told you not to take it apart, from my people, read spouse, if I can't finish the amp mod or it's all quiet on the Western Oregon Front.

As for the Plexi 50, ultimately I like this option but may end up experimenting on the patient first with the tone stack mod. I could use the experience and have been considering reentering the work force as an amp builder so the Plexi option may be a final solution.

I did a quick check for some Plexi 50 sound clips and was overwhelmed by the available clips but couldn't find any Plexi 50's. Are there any quick links to the Plexi to give me a sample of what it would sound like?

Lots of questions- If I did build a Plexi, would I be able to use any of the existing parts from the Carvin besides the Tubes? I would not be able to calculate the new resistor and cap values to use in modding the existing power supply components but would like the opportunity to try with assistance.

Tubenit- The Plexi you built in the photo shoot, was it a modded version or by the schematic available here? If it was modded is there a copy of your schematic available?

Basically my tastes range from Jazz, Blues, to Heavy Metal- Mostly Heavy Metal so I wonder if the Plexi can get a clean sound too. Most likely answerable by the clips.

Thanks for the responses,

Dreaming of a harmonic Christmas 

[jerrydyer]

I bid on one of those hoping to do what tubenit said.. gut and just use the chassis and trannies. im looking for a preamp to do that too if anyone comes across one.
Im going to build a hot rodded marshall into a preamp but it will include the PI.

[tubenit]

The Plexi you built in the photo shoot, was it a modded version or by the schematic available here? If it was modded is there a copy of your schematic available?

I took Doug's Plexi 50w and did the "add reverb to Western circuit" and then simply put a toggle on the V1a cathode to switch between three cap settings.  That's pretty much it.

Doug has lots of stuff including schematic, layout and Plexi 50w boards.  Look in the Hoffman Library of Information.

Later, I changed the reverb to the one tube reverb with the insertion prior to the LTPI.

Why don't you try the mods first. 

IF those don't do it for you then you can do a Plexi 50w.  Here is an idea paralleled V1 for 30% more gain with no increase in floor noise & one tube reverb. Just an idea .......... I don't have an agenda for you.

Sluckey also has a great idea for a Plexi 50w with two channels that I liked. It may be on his website?

With respect, Tubenit

[tubenit]

OR ........... IF you are really wanting quite a bit of gain and you can handle a more complicated build,  you could do a Marshall with an overdrive section.

With respect, Tubenit

[William_G]

Hi Silverfox, I own a Carvin Vintage 50 that I did the hasserl mod 2 on. The amp had a pretty good clean channel, but the overdrive channel was really bad sounding before the mod. The removing of the clipping diodes alone makes a big difference in the sound. You said you retubed the amp, but didn't say what tubes you installed. Here is a what a customer from Dougstubes had to say.
"I have to say you are a tube GOD! I have been playing a variety of amps live for more than 15 years and trying to get the much searched for sound that all guitarist dream of. Anyways to make a long story somewhat shortened I recently purchased a Carvin MTS 3200 head that I play through a 4x12 cabinet. I had purchased that setup because I had heard great reviews on it, I wasn't exactly impressed with Carvins factory setup with stock 5881's, it wasn't bad but it wasn't great, the better sound was on the clean side. I then had it rebiased for EL34's and put a set of electro harmonics on the power amp side it was an improvement BUT after our consultation I took your word and ordered a set of matched Ruby's EL34BSTR's for the power amp side and a combination that goes like this... on the preamp side V1-JJecc803s, V2-Tung Sol reissue 12AX7, V3-9th Generation 12AX7c, V4 and please take my word on this everyone its night and day tone in the reverb slot a NOS Mullard CV4024, and finally in V5 a balanced EH. Doug I think my Mesa, Marshall and Fender are going to collect allot of dust, with my 3200 amp I have it all. I know for a fact it would do any guitar, regardless of brand and or pick-up configuration justice. For example I played my custom Les Paul as well as my American Strat and even played an Ibanez through this amp. They all got sweet harmonic overtones at the tale of each note on the dirty side ( with no added effects peddles) and the clean side was absolutely the thick smooth cream on the cake!! Doug once again thanks man!!!"
The tubes I installed in my vintage 50 made a big difference, compared to the stock tubes! The hasserl web sit has a lot of info on how to make the mods, just read up. Carvin amps are all very simular on the inside, with numbers on the boards that match the schematic. Also email Richard Hasserl he may have the parts to help you out and the know how.

William_G

[tubenit]

Jazz, Blues, to Heavy Metal- Mostly Heavy Metal

Unless you are playing in large outdoor arenas .................. I'd make the amp 50w which is still incredible LOUD.

The fact that you like heavy metal is another reason I'd drop two power tubes down to 50w. It will give you a better chance to crank the amp up and actually be able to use it.

And I would definitely do the mods first prior to a major rebuild.

With respect, Tubenit

[PRR]

I'm not going to judge the clips on my wheezy PC speakers.

The Clean channel looks unremarkable *except* C26 R20 R21 form a severe treble-boost. Looks like an ear-burner. Snip one end of C26 and see if that's better.

Actually the Clean tone controls are significantly un-flat. The combination of 1Meg pots and a 100K volume loading them is IMHO unfortunate. Here's a couple different R and C values for a more-flat centered tone still with significant boost-cut for different tones.

The Lead channel goes on and on and might want a complete re-thinking. The diode clipper is fed by an inky-dinky cap. Bass goes from small to none as signal level rises.

The Power amp looks good except a LOT of NFB. I wonder if R43 could be 2.2K instead of 22K.

At this point I have to wonder. Is it worth turning a Thunderbird into a Buick? Lot of hard thinking, lot of try-and-see, with no certain happiness in reasonable time. I'd be inclined to sell it to someone who might favor its tone. OTOH if you suspect it has become "sick", then it has to be brought back to as-new tone or sold way below nominal worth. And it isn't a popular brand, and is too big to ship. So I dunno.

[silverfox]

Not familiar enough yet with how to indicate I've read all the posted threads. In any event, thanks everyone for all the information you've provided. I've tried other forums and this is what I needed; suggestions and pictures.

As for the re-tube that was done: It was the standard offered from Eurotubes. In regards to the magnitude of the signal- 50 watts is more than enough. I don't play in a band and my only audience are the family members. Perhaps on a loud day I might hit 12 to 15 watts- Then strangely they seem to scatter. I'm thinking the usual is likely around 8 watts. But you never know, I might get discovered and then I'll need 150 watts of dual power amp output with separate tone and effects loops to get that multi amp style sound- (there's actually a guy building an amp with multiple power amp outputs based on the theory, most of the pros play through multiple amp outputs).

Briefly, I played about everyday in the late 70's, got stuck in a Pentatonic rut and after my rig got stolen basically quit until I ended up winning a little pot from the lottery 5 years ago. Since then I've gone through several amps on the ritualistic tone quest and well, here I am on the pathway to Tonevana.

At this point, I'll start with some of the Mods suggested and go from there. December is the time frame that has been set aside for this project now that learning how to rebuild the front end of an F-150 has run it's course.

I'll post the results upon completion.

Best regards- Silverfox

[m3moser]

Sorry to weigh in late on this discussion.  I actually today received a Carvin 3200 chassis that a customer wants me to convert over to a 1959 Marshall circuit complete with 4 inputs, a 50/100 switch option and install a mini switch to change the tonestack values for the various era Plexi amps.  I have just taken out all the pcb boards and will not reuse anything in the amp except the power and output transformers.
   What I noticed right away was how low the power supply B+ filtering was.  In a typical Marshall 100 watt amp, you have some pretty major power filter caps which I am sure contribute to the overall sound of the circuit.  In this amp there were 6 22uf/500v power supply caps- way less than any other 100 watt amp I have seen recently. And there is no choke either.
   I will be moving the transformers around a bit, adding a choke and repositioning the preamp tube sockets so I can use a turret board traditional wiring setup.  I have done the same with the Peavey Windsor 100 watt amps to great success this way as well.  I hope the output transformer sounds good when its all done- it looks up to the task.  The good thing is that there is lots of room inside the chassis to move everything around and get a good layout.  But you do need a drill press to open up the holes in this rather heavy steel chassis.

[silverfox]

Coincidentally today driving home from the grocer, I began to wonder if anyone had ever built the equivalent of an Analog Modeling Amp by assembling several tone stacks and putting them into a selector switch assembly of sorts? I'm new to amp building and design.

This led to the question of: How substantial is the tone stack in determining the final tone quality of an amp? My thinking is the whole of, tube biasing, bypass capacitors, and tube type and the output components are obviously what makes the amp what it is.

So what or what components are most responsible in contributing to the tonal makeup that distinguishes an amp as a Mesa or Fender, ect..

My approach now in performing the mods will be to get one going and then construct some others to substitute into the circuit and see what it sounds like. In addition I may add the gain tube mode. Together with switches perhaps the outcome will be some sort of Analog Modeling Amp.

What is the name of the electronic device or circuit that was used in the 70's for television channel changing? Variactor? Is it wandering onto the path of heresy to raise the topic of active filtering for a tone stack? Is this what ultimately begins the degradation process in tube amp design: Active filters and variactors sorts of new fangle deviations?


Sincerely,

Silverfox

[smackoj]

hey m3moser; good to see you back on the board.....how about some pics of the build?

I just wonder when you describe the power filtering on the Carvin if maybe they decided to call it 100 watts because, should I say it, it makes the amp more sellable?  Sorry Carvin Co., but it's not a new thing to bump up the output specs. to get more sales.

Love to see some pics Mark, of the Peavey Windsor rebuild too.

adios, Jack D      

[m3moser]

I have started a build log of this conversion.  I finally had to break down and make a Facebook page for my amp builds but at least its easy to add new builds as I finish them- not that every build is worthy of a lot of pictures but its an easy way for customers to see the progress if I am actually on the ball enough to keep the camera by the bench.  Anyways, here are the latest progress pictures.

http://www.facebook.com/media/set/?set=a.369602379798574.87890.237868412971972&type=1

I hope the link takes you to the Frugal Amps Facebook stuff.  There are some shots of the Peavey Windsor conversion I did as well there.

[smackoj]

nice stuff on your page......like to hear one of those Carvin's or Peatown's.....looks like they'll get real loud

bandito     

[m3moser]

100 watts is very loud...not really all that much more than 50 watts but a bit louder and allows the player to adhere to the rule of rock guitar playing:

If you can't play good, play loud!   

[smackoj]

Maybe it all goes back to pre historic times when tribes fought one another? If a man knew he was gonna have to fight to survive, the smart one's brought the biggest club they could find. Makes sense because getting caught behind a bush with your tiger skin around your ankles and only a berry bush twig in your hand was a good way to get your hair parted and part of your skull knocked off.....ouch!