Mark IIC+ question

R

Ryan990

Active member
There's a C+ floating around for sale and I'm considering taking the plunge, however, I've been down the 2C to 2C+ upgrade rabbit hole and I wanted to ask those here who have experience with the various transformer versions. What are your thoughts on the 101xpt vs 105pt debate? This one has the 101xpt and the rp11a board. It was a 2C HRG that was upgraded to a 2C+ DRG.

Is the difference really that noticeable? I'm willing to wager that with my uncultured ear pallet I probably wouldn't hear much of a difference. Thanks!
 
The difference is not as big as the internets would have you believe. In fact, the amp-to-amp variances on aging components is going to be bigger than another 60pv on the transformer. They're both big iron.

I had a HRG one time that came with a 100 & happened to have a black stripe with a 105 on hand at the same time, so I swapped them & re-did the bias resistor (because yes the extra voltage changed the bias considerably). TBH, I thought the amp sounded better before I swapped but it was too much work to want to swap it back. So now there's a black stripe floating around somewhere with a PT100.

The rule with vintage amps is- while they are all good, some are better than others- and if it's not broke don't fix it.

The X101 runs roughly the same PV as the 100 does- both mid 400s. This means you can use any power tube you want. The 105 runs a touch over 500 +/- PV so with those & the Coliseums you're more limited on what 6L6 you can use- this is also important to consider.

Personally If it has the RP11 preamp, I could care less which PT it has.

All that being said, with IIC+ it's hard to be picky when one comes up for sale. However if you are, I would suggest that the biggest variable to consider is which of the 4 power sections you would prefer. While S, H & K are all A/B pentode, D runs the Class A slots in triode so it's softer & more liquid than the others. Personally I prefer that for leads however I prefer straight pentode for aggressive metal rhythms. To each his own here.
 
GJgo said:
The difference is not as big as the internets would have you believe. In fact, the amp-to-amp variances on aging components is going to be bigger than another 60pv on the transformer. They're both big iron.

I had a HRG one time that came with a 100 & happened to have a black stripe with a 105 on hand at the same time, so I swapped them & re-did the bias resistor (because yes the extra voltage changed the bias considerably). TBH, I thought the amp sounded better before I swapped but it was too much work to want to swap it back. So now there's a black stripe floating around somewhere with a PT100.

The rule with vintage amps is- while they are all good, some are better than others- and if it's not broke don't fix it.

The X101 runs roughly the same PV as the 100 does- both mid 400s. This means you can use any power tube you want. The 105 runs a touch over 500 +/- PV so with those & the Coliseums you're more limited on what 6L6 you can use- this is also important to consider.

Personally If it has the RP11 preamp, I could care less which PT it has.

All that being said, with IIC+ it's hard to be picky when one comes up for sale. However if you are, I would suggest that the biggest variable to consider is which of the 4 power sections you would prefer. While S, H & K are all A/B pentode, D runs the Class A slots in triode so it's softer & more liquid than the others. Personally I prefer that for leads however I prefer straight pentode for aggressive metal rhythms. To each his own here.
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Thanks for the helpful information!
 
GJgo said:
The difference is not as big as the internets would have you believe. In fact, the amp-to-amp variances on aging components is going to be bigger than another 60pv on the transformer. They're both big iron.

I had a HRG one time that came with a 100 & happened to have a black stripe with a 105 on hand at the same time, so I swapped them & re-did the bias resistor (because yes the extra voltage changed the bias considerably). TBH, I thought the amp sounded better before I swapped but it was too much work to want to swap it back. So now there's a black stripe floating around somewhere with a PT100.

The rule with vintage amps is- while they are all good, some are better than others- and if it's not broke don't fix it.

The X101 runs roughly the same PV as the 100 does- both mid 400s. This means you can use any power tube you want. The 105 runs a touch over 500 +/- PV so with those & the Coliseums you're more limited on what 6L6 you can use- this is also important to consider.

Personally If it has the RP11 preamp, I could care less which PT it has.

All that being said, with IIC+ it's hard to be picky when one comes up for sale. However if you are, I would suggest that the biggest variable to consider is which of the 4 power sections you would prefer. While S, H & K are all A/B pentode, D runs the Class A slots in triode so it's softer & more liquid than the others. Personally I prefer that for leads however I prefer straight pentode for aggressive metal rhythms. To each his own here.
Click to expand...
How much of a difference is there between the RP10 and RP11 boards?
 
I believe the differences are all in the individual components and not in the design. At this age some just sound a little better than others.

Personally I'd put more value in ones that have been serviced by Mike B. in recent history and less importance on the parts mix. I've sent him 15+ old Marks to service, and he's found & corrected issues with every single one.
 
GJgo said:
I believe the differences are all in the individual components and not in the design. At this age some just sound a little better than others.

Personally I'd put more value in ones that have been serviced by Mike B. in recent history and less importance on the parts mix. I've sent him 15+ old Marks to service, and he's found & corrected issues with every single one.
Click to expand...
There's one for sale semi-near me thats a very early IIC that was upgraded to a C+. It has the 101xPT but when I asked which board it had he wasn't sure and is unwilling to open it up and check. I also don't think it's been serviced, so I was just trying to get an idea on differences.
 
Thing is, these are so expensive because they are collectible. But people expect it to have certain features, and if it varies from that, I think the value might be significantly less.

It'll still sound great and would likely still be an expensive amp, but for a while factory C+ heads were listing at five figures. If this one is priced like that, I would be very hesitant to spend that kind of money if it's features are not the typical thing.
 
GJgo said:
If it passes the loop test, there you go. Factor in $500-ish for a factory service.
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He said it's loop verified but it will need a service. He said it's factory original down to the tubes but he's only used it a handful of time over 15-20 years.
 
Ryan990 said:
He said it's loop verified but it will need a service. He said it's factory original down to the tubes but he's only used it a handful of time over 15-20 years.
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Make sure YOU try the loop test in person....if he's charging huge money for it. If it's a steal, just go get it. I will say, if it is a C and not a +, my first 2C was incredible before the upgrade, and after I kinda missed the tone of the C. It was a rude raw monster.
Still killer as a C+ but it had such a killer raw thing, before that was lost as the + made it smooth.
 
Ryan990 said:
How much of a difference is there between the RP10 and RP11 boards?
Click to expand...
The RP10 is the 2C board, that can be upgraded to a C+. The RP11 is the production 2C+ board. Some might say the production C+ sounds better. Mike B would tell you that's bunk. An upgraded C+ is just as good as a production C+. I had an upgraded SRG, and a factory HRG..the SRG slayed the HRG. Sold the HRG.
 
Racerxrated said:
The RP10 is the 2C board, that can be upgraded to a C+. The RP11 is the production 2C+ board. Some might say the production C+ sounds better. Mike B would tell you that's bunk. An upgraded C+ is just as good as a production C+. I had an upgraded SRG, and a factory HRG..the SRG slayed the HRG. Sold the HRG.
Click to expand...
I emailed Mike and asked that very question and he gave me an almost same response "if I or the factory did the update way back in the 80s, there's no difference. A C+ Is what it is no matter the board."
 
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