Mark IIC+ vs Mark V

[chipaudette]

The second question I can answer. On the V, the Pull Deep is always "off" and there is no switch for engaging it. And yes, that certainly covers some of the perceived brightness. I almost always have it pulled on my IIc+. But even with it pushed in, the IIc+ mode on the V is a good deal brighter than my IIc+.

Do you know that the circuit is designed to mimic the not-pulled-deep mode? Or are you just saying that there's no switch?

There's no Mark V switch for the equivalent of the pull-bright on the Mark II/III volume knob, yet it's built into the circuit. The same could be true of the Pull Deep...

Chip

 

[Catthan]

Regarding the small cap of the non-geq IIC+s, isn't this smth that could be modded in the V?

 

[LesPaul70]

Do you know that the circuit is designed to mimic the not-pulled-deep mode? Or are you just saying that there's no switch?

In the V manual, when they tell you which pots you ought to pull on the IIc+ to make it similar to the IIc+ mode setup on the V, they say you should pull the first Volume pot (Pull Bright) and the Lead Drive pot (Pull Lead) on your IIc+. Not the Master 1 pot (Pull Deep).
In other words, Pull Deep was not pulled in the setup they used as a basis for the IIc+ mode on the V.

(This was already mentioned earlier on in this thread.)

 

[LesPaul70]

Regarding the small cap of the non-geq IIC+s, isn't this smth that could be modded in the V?

Presumably, and it is (along with a 'Deep switch') something I've been intending to do to my V once its warranty runs out.

However, maybe I won't. For one thing, the Mark V is a nightmare mess of computer motherboards and tightly fitted components under the hood, not very encouraging to modders. (See this thread http://www.grailtone.com/forum/viewtopic.php?f=33&t=38280 for images.)

Secondly, it could be just pointless to try to exactly replicate the sound of my IIc+ on a V. I know I did, for a long time, with all kinds of tricks (esp. an EQ pedal in the loop). But while the overall timbre got very close at best, it wasn't exactly the same, and the amp feel and behavior were completely different. More seriously, the sounds I got when I tried to imitate a IIc+ on a V weren't even very good. In fact, they were a far cry from the best sounds you can get from channel 3 on a V!

Furthermore, then your IIc+ mode and IV mode would sound a lot more similar to each other. One of the biggest differences between them is the different coupling cap.

And, even after the mods, a V would still have a very different power amp section, which will have a major impact on the amp sound, feel and behavior.

So, probably not worth the effort. Especially when I have an original IIc+ already.

 

[chipaudette]

I popped open the Mark V schematic to see what they were doing about the "Pull Deep" functionality and to see how it compares to its implementation on the IIC+.

On the IIC+, the Pull Deep enables a big fat cap on the cathode of the tube immediately following the reverb and effects loop (V2B). The bigger the cap, the deeper the bass extends. (Note that this doesn't add bass, it merely lets bass through that already exists. ) With the Pull Deep disabled (ie, the knob is pushed), the cap is 0.47uF. With the Pull Deep enabled (ie, the knob is pulled), the cap is 15 uF. Big difference.

On the Mark V, the equivalent part of the circuit is V6A. This part of the circuit is only for channel 3, unlike on a IIC+, where it is used for the clean channel, too. On the Mark V, the V6A circuit does appear to be used for all three modes of channel three...modes "M7", "M8", and "M9". Presumably, M7 is the IIC+ mode, M8 is the Mark IV mode, and M9 is the extreme mode.

On the cathode of V6A, the IIC+ mode (M7) has 4 uF worth of caps. In the other two modes (M8 and M9) there is the 15 uF cap.

It's interesting that the Mark V's IIC+ mode uses 4 uF and not the Mark IIC+'s actual value of 0.47 uF. By using the bigger cap (but not quite the full 15 uF), they'd get something that's not quite "Pull Deep", but also not "not Pull Deep".

After this point in the cicruict, there's lots that's different compared to a real IIC+. The effects loop, for example, is in a totally different place and, as a result, has added another gain stage. Also, Doug West's 0.22 uF cap for the EQ vs the stock 10 uF cap would also greatly alter the voicing. So the net effect of these alterations could easily have suggested to them that they should make their own alterations to the earlier circuits (such as V6A) to compensate.

Whatever their reason, I find it interesting how they chose to handle the Pull Deep issue.

Chip

 

[user 19640]

Another twist to this:
Isn't one of the key part of the sound of the IIC+ the "Volume 1" control?
I have never tried a IIC+, but I have owned a Quad pre for some years now, and I've tried a Mark V with the IIC+ mode. I was really disappointed with the mark V.

So, I little theory:
To recreate the more lush and dynamic feel (as my Quad Lead 1), maybe try a clean boost ( Mesa tone-burst) in front of the mark V with the amp's gain set really low? Just to kind of "replace" the Volume 1 knob which the mark V is lacking?

And maybe also put in some RFT ECC83s .

My personal opinion with the mark V was that it were more stiff, modern and harsh compared to the quad.

 

[chipaudette]

Another twist to this:
Isn't one of the key part of the sound of the IIC+ the "Volume 1" control?

IIRC, for Channel 3 on the Mark V, the circuit is built as if "Volume 1" were hard-wired to 7.75. So, its function in the circuit is there in the Mark V...it's just not changeable by the user to adapt to different styles or guitars.

Chip