Mesa Boogie Transformers: Questions and History

[tbonesullivan]

With the upcoming Mark IIC+ "reissue" being released, I'm seeing the old questions pop up about the mythical power transformers used in the Mark IIC+ amplifiers and some of the early Mark III, I believe part number 162318, which was available in the 100 and 105 versions. These were supposedly not able to be made anymore due to either materials used in the construction, or techniques used, or maybe some "deep magic" or whatever. These were all built by Woodward-Schumacher, or later I think just "Schumacher", EIA Code 606, which also supplied Fender at the time. Since many of the early Mesa designs were pretty much modified Fender amps, they pretty much used the same exact transformers, and it wasn't until the higher wattage amps that they needed to have Schumacher make them specifically for Mesa. From what I heard Mesa stopped using them as a supplier when they moved production to Mexico at some points in the 1990s?

Then they switched suppliers to Magnetic Components (EIA 166) and Marvel Electronics (EIA 989), who were in reality the same company. They then decided to close in Oct 2020, and Mesa is now back with Schumacher, which I would assume to be made in Mexico? Or did they somehow convince them to re-open manufacturing in the US?

Anyway, I've heard a lot of strange things out there, and was just wondering what exactly was so special about those Mark IIC+ power transformers?

I haven't even looked into the output transformers, as it seems people almost don't care about those, especially when compared to the power transformers.

 

[scotticus]

I wonder if Mesa thought they were all that special at the time. The owner's manual states that if the transformer blows, to swap in a Fender Twin transformer

 

[Jeffw5555]

All the chatter about power transformers is a load of nonsense. They could easily replace the 105, but won’t. The 105 puts out too high of voltage for today’s crappy Chinese and Russian tubes.

Besides output voltage, the only other parameter that affects sound is the voltage vs current curve, AKA sag. Again, this could be replicated quite easily.

 

[VisaL]

All the chatter about power transformers is a load of nonsense. They could easily replace the 105, but won’t. The 105 puts out too high of voltage for today’s crappy Chinese and Russian tubes.

Besides output voltage, the only other parameter that affects sound is the voltage vs current curve, AKA sag. Again, this could be replicated quite easily.

Isnt it quite likely that under normal load, these wont sag in any meaningful way i.e. those provide enough current for the circuit? My export mkiii tranny puts out similar voltage to those magical ones. If the x105 would be mandatory for the magical 2c+ goodness, none of the export models would have that magic. And funnily enough, mkiii transformers did not have the magic, until those were used for the early rectos, they those very the magic incredient of the dual rectifiers. As if.

Usually it’s the output tranny that amp collectors are more concerned.

 

[Filamentary]

In my limited understanding, it’s the output transformer that is coveted (and which you are describing), which makes sense as it mediates the relationship between the power amp and speaker.

I’m not aware of there being any particular magic in the power transformer. If I’m wrong about that I’d be glad to be educated.

 

[tbonesullivan]

In my limited understanding, it’s the output transformer that is coveted (and which you are describing), which makes sense as it mediates the relationship between the power amp and speaker.

I’m not aware of there being any particular magic in the power transformer. If I’m wrong about that I’d be glad to be educated.

It seems for the most part that the Power transformer is what people obsess over. They want the 105 or the Export, not the 100. And people go gaga over the early Mark III's that have Mark IIC+ power transformers, just like they go nuts over the early Mark IVs that had the Mark III power transformers. I've seen some go for quite a bit on the secondary market. Seems like very few people care about the Boogie output transformers, as they are just, transformers.

 

[Jeffw5555]

Isnt it quite likely that under normal load, these wont sag in any meaningful way i.e. those provide enough current for the circuit? My export mkiii tranny puts out similar voltage to those magical ones. If the x105 would be mandatory for the magical 2c+ goodness, none of the export models would have that magic. And funnily enough, mkiii transformers did not have the magic, until those were used for the early rectos, they those very the magic incredient of the dual rectifiers. As if.

Usually it’s the output tranny that amp collectors are more concerned.

There isn't any magic associated with power transformers. It is simply a case of mistaken correlation , that is, "my IIC+ has the 105 transformer, and it sounds great, therefore the 105 is responsible". It isn't, at least from the "magic" or "unobtanium" sorts of myths surrounding them. Again, Mesa (or anyone else) can easily replicate the 105, there isnt anything special about them that makes them special. It is simply that they put out too high of voltage for today's crappy tubes. Remember, back when the 105 was used, they were using USA made tubes that could withstand the higher voltage. It is the tubes that are "unobtanium", not the transformers!

 

[bandit2013]

In some respects, both power and output transformers have an impact on sound characteristics. Running the higher plate voltages of the 105 I would think the OT would also be able to work in that higher voltage range. However, the transformers do have an effect on the sound characteristics you hear. It does not make the distortion characteristic better or worse. Over the past decades since the IIC+ came out, sure there have been regulations on transformer efficiencies and what not. Mesa could have easily had the transformers built to spec and still meet the efficiency requirements. They did it with the JP2C and now the Mark VII. You have to consider other factors that took place as part of a business decision to consolidate some transformers to be used in other products. Also consider the fact that Mesa spent many years redefining the Mark characteristics to the point it no longer represented the original designs. The Mark V90 being the furthest deviation of them all. Mostly due to tunning changes of the circuits to favor change in speakers intended for the combo amps. I personally do not like the MC90 speaker, but it is ok I suppose. Mark IVB and Mark V were not very compatible with the EVM12L speaker, they sounded sterile, unlike the Mark III which was my first amp to expose me to the power of the EVM12L Black Shadow, to me that was the pinnacle of excellence. Just so you know, the Mark VII and JP2C work rather well with the EV speaker, and equally well with the 60W-V30 in the 212 or 412 cabs. Mesa did spend some money on retooling the transformers for the JP2C and that design looks to have been carried over to the Mark VII but may be different in some respects. I did not look at the transformer part numbers. My JP2C does not have the Schumacker transformers. I believe both Mark VII are. Considering many of the comparison videos between the JP2C and the Mark VII to some IIC+ amps of the past, the apple does not fall far from the tree and are respectively close. The exception is the lack of a variable volume 1 control that adds gain the to the second gain stage following the tone stack. All of the other Marks (V, JP2C, and Mark VII) have some fixed resistors in place of the potentiometer. However, the pull pots on the JP2C and perhaps the CH2-CH3 may have some tweaks to that part of the circuit to change the gain characteristics. I do not have the schematics, so I am only speculating on that. the JP2C CH3 is similar to the IV mode on CH3 of the Mark VII. Different gain characteristics but not that much different. I assume if the same transformers are used with the IIC+ reissue, but with the same topography of the IIC+ preamp with all of the pulls and same controls, I expect it to deliver the goods on par with the 1980 relics of the past but much lower in cost to the buyer by $10k to $20K less. So, when the amp finally bites the dust and becomes a paper weight, how much did it cost you? At least the reissue has hope of resurrection from the dead since it probably does not use components like LDRs that became obsolete since 2010 which was the cut-off date for their use due to cadmium content in the photo resistor element. The Vactec Vactrol was also used in some industrial equipment. The company that continued its production changed names from Vactec to Perkin Elmer. I looked up the Perkin Elmer data sheets and they were marked with Vactrol Vactek. Here is the reference I had found doing a search. Radwell had these parts categorized as a bearing so they were never purged from inventory. They are not bearings but the VTL5C1. Not sure if they still exist as this may be an old reference. Here it is anyways for your references. That low-cost part now costs around $12. May help with that $20K paper weight when the critical one's fail. I would contact this vendor if the parts are legit before buying. This could just be an old listing and they are sold out.

https://www.radwell.com/Buy/PERKIN ELMER/PERKIN ELMER/VTL5C1

 

[FedWar]

In some respects, both power and output transformers have an impact on sound characteristics. Running the higher plate voltages of the 105 I would think the OT would also be able to work in that higher voltage range. However, the transformers do have an effect on the sound characteristics you hear. It does not make the distortion characteristic better or worse. Over the past decades since the IIC+ came out, sure there have been regulations on transformer efficiencies and what not. Mesa could have easily had the transformers built to spec and still meet the efficiency requirements. They did it with the JP2C and now the Mark VII. You have to consider other factors that took place as part of a business decision to consolidate some transformers to be used in other products. Also consider the fact that Mesa spent many years redefining the Mark characteristics to the point it no longer represented the original designs. The Mark V90 being the furthest deviation of them all. Mostly due to tunning changes of the circuits to favor change in speakers intended for the combo amps. I personally do not like the MC90 speaker, but it is ok I suppose. Mark IVB and Mark V were not very compatible with the EVM12L speaker, they sounded sterile, unlike the Mark III which was my first amp to expose me to the power of the EVM12L Black Shadow, to me that was the pinnacle of excellence. Just so you know, the Mark VII and JP2C work rather well with the EV speaker, and equally well with the 60W-V30 in the 212 or 412 cabs. Mesa did spend some money on retooling the transformers for the JP2C and that design looks to have been carried over to the Mark VII but may be different in some respects. I did not look at the transformer part numbers. My JP2C does not have the Schumacker transformers. I believe both Mark VII are. Considering many of the comparison videos between the JP2C and the Mark VII to some IIC+ amps of the past, the apple does not fall far from the tree and are respectively close. The exception is the lack of a variable volume 1 control that adds gain the to the second gain stage following the tone stack. All of the other Marks (V, JP2C, and Mark VII) have some fixed resistors in place of the potentiometer. However, the pull pots on the JP2C and perhaps the CH2-CH3 may have some tweaks to that part of the circuit to change the gain characteristics. I do not have the schematics, so I am only speculating on that. the JP2C CH3 is similar to the IV mode on CH3 of the Mark VII. Different gain characteristics but not that much different. I assume if the same transformers are used with the IIC+ reissue, but with the same topography of the IIC+ preamp with all of the pulls and same controls, I expect it to deliver the goods on par with the 1980 relics of the past but much lower in cost to the buyer by $10k to $20K less. So, when the amp finally bites the dust and becomes a paper weight, how much did it cost you? At least the reissue has hope of resurrection from the dead since it probably does not use components like LDRs that became obsolete since 2010 which was the cut-off date for their use due to cadmium content in the photo resistor element. The Vactec Vactrol was also used in some industrial equipment. The company that continued its production changed names from Vactec to Perkin Elmer. I looked up the Perkin Elmer data sheets and they were marked with Vactrol Vactek. Here is the reference I had found doing a search. Radwell had these parts categorized as a bearing so they were never purged from inventory. They are not bearings but the VTL5C1. Not sure if they still exist as this may be an old reference. Here it is anyways for your references. That low-cost part now costs around $12. May help with that $20K paper weight when the critical one's fail. I would contact this vendor if the parts are legit before buying. This could just be an old listing and they are sold out.

https://www.radwell.com/Buy/PERKIN ELMER/PERKIN ELMER/VTL5C1

About ldrs i heard that the some Chinese companies are bringing these back.
Furthermpre I know for a fact that here in the eu 33 workshop has a way to make them, should any of those fail.

 

[bandit2013]

From what I see in the data sheets, the Xvive 5C1-R is not equivalent to the Vactek Vactrol VTL5C1. The Chinese part is only suitable for a 60V AC/DC, the original part VTL5C1 has a Cell voltage of 100V AC/DC. As for the turn on characteristics and associated resistance not sure if they are equivalent. Just comparing the 10mA LED current, the resistance characteristics do not match.

I am not all that familiar with the LDR device or its use in the circuit, other than a switch of sorts. What effects will the response time have and at applied LED current, what will the resistance be? Also the Xvive did not mention what the cell capacitance is. Vactek has a 5pF capacitance. That itself may have leakage but is that only when the cell is excited by light or when it is in the dark current phase?

I did a search for the parts as I was curious about them in an attempt to help out a friend who may need them. Thought this would be a possible resource if they have the parts in inventory for those looking for the actual part and not a substitute. the old data sheet I looked for with the Palmer Elmer name still had the Vactek Vactrol branding on their data sheets. Similar to the one you can find through Farnell.

I no longer have any amps that make use of the LDRs Most of my Mesa amps were made after 2012.

 

[rarebitusa]

WRT original LDRs @Jay Omega chimed in on that topic with this post when I asked about the Xvive 5C1-R

Vactrol LDR Replacement

 

[RayBarbeeMusic]

About ldrs i heard that the some Chinese companies are bringing these back.
Furthermpre I know for a fact that here in the eu 33 workshop has a way to make them, should any of those fail.

They are not the same and are not substitutes. Same part number, different characteristics. Had to beg Mike B for some not long ago because there is no functional modern equivalent.

 

[Jay Omega]

They are not the same and are not substitutes. Same part number, different characteristics. Had to beg Mike B for some not long ago because there is no functional modern equivalent.

I found an acceptable replacement but the most recent quote was $11.50 ea for the min quantity of 1,000. I’ll be using relays once my supply of NOS is gone

 

[FedWar]

I found an acceptable replacement but the most recent quote was $11.50 ea for the min quantity of 1,000. I’ll be using relays once my supply of NOS is gone

care to share the builder / model?

 

[Jay Omega]

care to share the builder / model?

Advanced Photonix makes an NSL-37V5C1 which is a good substitute for the VTL5C1 in the stock IIC+ circuit. I tested in terms of forward voltage, on resistance, and state transition time. It does have a CdS cell like the original Vactecs so it does not meet RoHS.

The Advanced Photonix NSL-32SR2 is a good substitute for the VTL5C4 in the C+

 

[tbonesullivan]

Well, this certainly has turned into an interesting discussion. As I have a few Mesas from the 1990s, I definitely should look into the future availability of some of the components in them. I mean, aside from Axial capacitors. I'm unfortunately not familiar enough with the internals of my amps to know which would be affected by problems with LDRS and/or Vactrols. Most of the amps I have were made in the 2000s and 2010s, with the Mark V combo being the most recent, from 2022.

 

[rarebitusa]

I'm unfortunately not familiar enough with the internals of my amps to know which would be affected by problems with LDRS and/or Vactrols.

One typical usage on the IICs and IIIs they are utilized as control devices for the push/pull and footswitch functions. This is from the II-C manual

 

[FedWar]

LDRs were used as circuit switcher instead of relays.