Another C+ in Venice Italy

[merendina]

Good morning guys! Just opened and pictured my new C+ s/n 126xx 15" long head HG hardwood and I compared to my c+ DRG s/n 139xx. there are some difference on the preamp PCB because first is SP11A and the second one RP11A (reverb). There are also a lots of differences in terms of components like swithces, knobs.


In sound terms 60/100 has less gain than simul(why??!!??) but it is more focused, more articulated, more in your face, more balanced with a tight bass and very harmonic top end.
Presence in simul above 3 is harsh, in 60/100 it's always good

Does the simul have a different preamp layout compared to the 60/100?

Does the reverb circuit cause loss of sound through the signal path?

Is it possible to change OT and convert 60/100 to simul and vice versa?

I would like to know if the sonic differences are concentrated to de OT difference or a preamp layout..

Thanks guys

DRG 139xx

HG 126xx

 

[mark2boogie]

Hi merendina,

If I was you, and without any further help from C+ owners, I would take the time to trace the schematic of the power stage, the presence FB circuit, the phase splitter stage, to check what's different between your 2 amps, at first. Of course, I suppose that your amps are "fully serviced and considered to meet their specs", otherwise the difference in sound would be tied to a difference in condition... I am a MKIIA/B 60/100 owner, so I can't tell you more, unfortunately.

A+!

 

[merendina]

Hi merendina,

If I was you, and without any further help from C+ owners, I would take the time to trace the schematic of the power stage, the presence FB circuit, the phase splitter stage, to check what's different between your 2 amps, at first. Of course, I suppose that your amps are "fully serviced and considered to meet their specs", otherwise the difference in sound would be tied to a difference in condition... I am a MKIIA/B 60/100 owner, so I can't tell you more, unfortunately.

A+!

Merci Mark

I'm more a musician than an amp tech, I was waiting for a Boogiebabies post about the condition. i guess some component in the eq section was changed because sounds weird the yellows.. Looking around i found a post concerning OT substitution..

 

[mark2boogie]

Buona Sera merendina,

If you are not very technically minded, should I say... Stay Wise !

In theory, looking at the schems, the conversion from simul-class to 60/100 is possible, and conversely, but a different output transformer is indeed required in simul-class, along with a reinforced power HV filtering : in simul-class, the screens of the EL34 are connected on the same supply as the plate, and they are much more sensitive to ripple, so the supply need an improved filtering. This would be the same with a triode/pentode switchable connection, which is an alternative to the simul-class but using a standard output transformer.

A+!

 

[Boogiebabies]

David,

I could literally write a novella about what the differences are in these two amps.

The filtering is no different between simul and 60/100. Only on 60W models.

There is a lot going on here, but I will try to get to the point.

The EQ circuit in the HG would need to be put back to stock before you can get an accurate image of what the amp could potentially sound like. 30-50V tantalum would be proper.

The resistors in the early amp are Beyschlag and Dale and the coupling caps are Sprague's comprised of a mixture of 225P and 715P. The 225P's are smooth sounding and the 715P's have a bit more top end. Depending on the mixture Mesa used in the clean and lead sections will determine if you have more sparkle in the clean or more cut in the lead channel. The Beyschlags are pretty consistent throughout the C+ production, but the black Dale plate resistors are only found on early examples of these amps. To my ear, they sound fantastic but different from the later metal film types Mesa used. Lastly, Mesa used larger ceramic disk caps labeled "Mexico" which to my ears are a bit smoother than the later green (Meanie) caps.

The DRG from the late production is markedly different in metal film resistors, a mix of new green and old Mexican ceramic caps and a mixture of 715P and Mallory PVC type coupling caps. To me, these Mallory PVC's had the most unique voicing of any cap Mesa used. They have a tendency to be bright, clear and unforgiving in a way. Soldano used the same caps in the .022uf version from its inception and has been documented to have a clear and accurate tone with a slight slur to the treble frequencies. The green 120pf cap across the 470K at the lead input always sounded brighter and harsher. The later amps also did not have the 120pf cap off the loop to bleed treble to ground. They were omitted around 12,200. The reverb circuit can and will sound different on almost every C+ you get. The component variation, transformer accuracy and tank accuracy all have effect on the circuit. To me, the truth of the matter is that I have never heard two C+’s that sound identical yet alone ones with different power amp, EQ and reverb options. My final point would be that these amps are unique unto themselves so it makes little sense to me to attempt an arduous search for a Simul OT with no guarantee that it will sound similar to the simul you already have. Add in that the HG has a different circuit board and altered wire dressing and spacing from an RP-11A the intricacies are vast as to the possibilities of why tonal differences exist from amp to amp, not including any debate on output transformers, palladium coated wires, tubes, temperature humidity, bias, speakers, cabs, ignorance and voodoo.


Ed

 

[mark2boogie]

The filtering is no different between simul and 60/100

@Ed : look at my schematic below, on the left side, high voltage supply filtering, you will notice that for simul-class circuit, the head filter caps are doubled and mentioned for "simul only", so there is a difference, at least on paper.

But maybe have you got another version of the MKIIC schem ? Moreover, I never opened a MKIIC to check if it's true, but I remember finding that on MKIIIs that I serviced. The goal is to attenuate ripple to the screens of V8 and V9.

Look at the pic of a MKIIB Simul-Class below : at the right lower side, you can see the 220µF doubling caps underneath the PSU board. So that makes me think that the same improvement was also existing on MKIIC Simul-Class and - possibly - on 60/100W (?).

A+!

 

[Boogiebabies]

@ Mark2.

I have owned six C+'s, five simul and one 60W and I have done cap jobs on 60W and 100W IIB's, IIC+'s and one MK III. The 60W's have only two 220UF caps in the power supply, The 100W and Simul has four and the MK III has two. The K series has eight 220uf's. As for the schematic, I wrote my own due to the inconsistent nature of what Mesa claimed was an accurate schematic. After eight years of research ( I officially retired last year ) you tend to notice differences from amp to amp regarding components, omissions and changes in production. I have been fortunate to own a few of these amps, but more fortunate that I have had hundreds of others to review from this forum, not to mention a few who sent me their amps for blueprinting and repair. If you put the time in to study these amps, you will have your own schematic committed to memory. I spent the majority of the time questioning myself, not waiting for someone else to do all the work just to question them.

 

[mark2boogie]

@Boogiebabies :

I spent the majority of the time questioning myself, not waiting for someone else to do all the work just to question them.

Well, I am not sure to undertand clearly your purpose (sorry - I am French), but I tend to interpret it as a kind of dogmatism, even a lack of modesty... I hope that I am wrong.

Nonetheless, may I humbly suggest you to read my Boogie MKIIA 60/100 Rev Eq and questioning yourself about my way of searching and sharing the useful informations ?

Over.

 

[Boogiebabies]

@Boogiebabies :

I spent the majority of the time questioning myself, not waiting for someone else to do all the work just to question them.

Well, I am not sure to undertand clearly your purpose (sorry - I am French), but I tend to interpret it as a kind of dogmatism, even a lack of modesty... I hope that I am wrong.

Nonetheless, may I humbly suggest you to read my Boogie MKIIA 60/100 Rev Eq and questioning yourself about my way of searching and sharing the useful informations ?

Over.

With anything you do, if you want to know ultimately everything about a subject you must put the work in yourself. Other people may help you along the way, but you still have to make sure the info is correct. No dogmatism, just the truth, I've climbed that mountain already. Now you may have assumed the "ugly american" already, but I have had help from IIC+ owners and helped IIC+ owners in Italy, Sweden, Norway, Germany, Finland, England, Switzerland and France. The only guy who bugged the life out of me was a Spaniard.
I am always willing to help, especially if I can learn something I did not know before.
That is where the fun lies.