carvin mts3200 - resurrection and mods.

[DummyLoad]

acquired a carvin mts3200 off CL for 125bux. said a pre-amp tube was bad, however, when working but the clean channel was decent. i figured at the very least i had a carcass for a twin-reverb frankenamp with EL34s. that sealed the deal. the transformers in this amp were wound by woodward-schumcher so that was an added plus.


had an open 100k plate R on V2A and 100K plate R on V3A was frying bacon. i don't like the heater starved DC for V1 & V2. jumpers installed for R29 & R30 helped some. 
one of the speakers had the fiberboard for the fast-ons separated from the basket - the rivet head broke off. bolted it back on. 


testing amp - lead channel - UGH!! nasti, nasti, nasti! one of the worst i've ever heard. ever. URL searches for this amp substantiate that. clean channel is very much pleasing and the reverb is decent. reverb is a spin of a one tube plan driving a 9G series tank (8K input) with RC coupling CC driver. see schematic.


mods: see pics in link. basically, we get rid of the deplorable zener clipping ckt and graft in carvin "legacy series" coupling scheme between V1A and V2B: see attached schematics.


remove R11, C14, D1-D4,C15
see pic to remove C14-D3 trace.


replace:
R11 .0022uF 400V
C14 becomes jump points.
D4 - 1M 1/4W
D3 - 470K 1/4W + 470pF <--- note that both components will fit in place if zener IF you select the correct parts. 
D1 - .0047uF 200V
D2 - 68K 1/4W


--pete

EDIT: C15 swapped from 10uF to 1uF. --pete

[DummyLoad]

full schematics. mts3200 + legacy for comparison.


top of board (component side) shot.


--pete

[silverfox]

Mine's still in the grave but, I've recently decided to build a stereo power amp based on my recently completed amp project. I never really got enthused about the Carvin series. Perhaps the Steve Via version is a good amp but for HM, they just don't seem to get it. I believe the transformers are of very good quality but the biggest problem is going to be getting some one to buy it after you mod it. Will the reputation, (speaking of tone), will the rep follow it and make it hard to get full value from it. Lots of good quality parts to be had....

silverfox.

[DummyLoad]

Mine's still in the grave but, I've recently decided to build a stereo power amp based on my recently completed amp project. I never really got enthused about the Carvin series. Perhaps the Steve Via version is a good amp but for HM, they just don't seem to get it. I believe the transformers are of very good quality but the biggest problem is going to be getting some one to buy it after you mod it. Will the reputation, (speaking of tone), will the rep follow it and make it hard to get full value from it. Lots of good quality parts to be had....

silverfox.

flipped mine for 400bux this afternoon. the clean channel is very respectable, and the lead channel no now also respectable with the mods above.


new owner loves it.


maybe build yours into a super reverb for the clean channel and turn the lead channel into a 2204 without the MV: move MV to PPIMV.


--pete

[silverfox]

Congratulations! I actually did download the mods you posted when I first saw them. There weren’t many mods when I looked in the past and they didn't seem to change the tone or gain much. Sounds like yours is an improvement on what's out there.  Flipping a project like that so fast can really make up for some other more labour intensive experiences from the past. What would you compare the tone of the higher gain channel to, if any? I will say the clean channel was respectable. The Carvin project for me was what first brought me to this Forum. Fortunately it didn't work out and the end result was several years of ongoing learning and construction journey. Oh yeah, and perhaps about a thousand bucks worth of parts inventory.

silverfox.

[DummyLoad]

man, i can't describe tone to you, it's pointless. does it sound like a 2202/04? not really, no CF. it does sound good though. some clips were made by the man who bought it, but have yet to receive them. when i do, i'll upload them to my dropbox.


--pete

[DummyLoad]

some clips here.

https://www.dropbox.com/sh/gr3qxjagznwc000/AAAO5rVtdmAxll92JxOZPfb0a?dl=0

--pete

[DummyLoad]

why the thread ressurection? i bought a head version (ugly red tolex - bleh!) of this amp yesterday with a kaput reverb and no reverb tank. the 8K (4GB type) tanks are hard to find. carvin is closing shop, so no luck there. TAD in germany has them for 32 euros plus 27 euros to ship. ugh! no! 60 bux for a tank is pretty steep. it's a single tube reverb so i thought i'd experiment. i have a type 9FB tank and pulled up tube CAD for some quick circuit profiles. comparing the 12AX7 to 12AT7 the drive output into 2k load with a 12AT7 wasn't too terrible, so 12AT7 and 9F tank it is...and voila! lush reverb again. to summarize: install 12AT7 in V4 and 9FB31C tank and your reverb returns.

the zener clip elimination mod works on rev. H PCB as well with the exception of the DC fusing resistors R29 and R30, as they are not present on rev. H board. plate resistors R19 (V2.A) and R42 (V3.A) should be replaced with 1W resistors. on this one the 1/2 W parts were discolored from overheating - in all fairness to carvin, this amp has been gigged for 10+ years. in the combo i had, one was open the other was noisy so they seem to be problematic for this circuit.     

--pete

[PRR]

> carvin is closing shop

Oh no!  https://www.facebook.com/carvinaudio/ 

(Technically closing factory, shop is over-busy just now, but we know where this is going....)

[DummyLoad]

> carvin is closing shop

(Technically closing factory, shop is over-busy just now, but we know where this is going....)

some conglomerate in china will buy the name and flood the market with crappy, chinese made carvin branded equipment.


--pete