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[GuitarBuilder]

Here's the part I have trouble with:

While the MP-1 input stage is tube-based and therefore gives you all the nice interactive responsiveness, touch, etc. for your guitar, the output is solid state!  That output design dictates what response you will see in your power amplifier.

A tube power amplifier will not add any more of the nice interactions; instead, you will only add additional coloration or distortion (if you like) to the sound.  While the tube power amp may sound warmer, etc., in effect it is requiring you to change your patches' EQ and gain settings.  A solid state amp with flat response will not.

Why would you care?  Because if you change tubes or tube power amps, you will most likely have to go back and re-EQ all your patches.  No problem of course if you enjoy doing that!   

[rnolan]

Hey GB, while in general I'd agree, I didn't experience that when I switched from my B200s to the TS100, I didn't have to change the patches at all. Just picked up a very slight hint more warmth with the TS100 (it's deliberately flat response and tranparent). It will really depend on the tube amp, the TS100 was also designed to power passive studio cross reference monitors and would be quite at home in a high end HiFi setup.  Tube HiFi amps would also work quite well with MP1/2 though to get enough power they tend to get heavy and expensive.

[Rusty]

Hey, thanks everyone for your replies and opinions that I am taking on-board.

I'm gonna have to get a good loud blast again on the 9100 50/50 and see what I think, It's been a while!

The 8008 80/80 valvestate that I'm using at the moment is transparent in the rack. I mean, it is transparent and invisible between my ADA's, effects and the speaker which I think is a good thing as it only acts to amplify what I have before it in the chain without coloration.
There is a switch on the back to select from normal to 'valvestate' sounding which only adds in an RC series low/mid pass filter circuit at the output stage after the power transistors.
I just keep it on normal though. It's a very good amplifier, light in weight well designed and 1U rack space.

I did modify it and installed a 12V fan that kicks in with a 50 degrees celcius thermocoupler bolted to the heat sink via a simple little circuit.
I know,,,, mos-fets don't mind getting hot and they can operate hotter than hell,  but my concern was what do I have racked above 1 for 1, with no space. Thats why I moded with a fan that kicks in at 50 degrees. if the heatsink is at that tempreture it's loud, and you will never hear the fan. 



But,,,   back to the 9100 50/50,,,  A good option with the 9100 50/50 is that with some slight modification, I could select what type of valves to use for each channel.

Like, I could have 6l6's on the left and El34's on the right, or I could try out the KT77's or even the 6CA7's, any of them, left or right or on both sides in pairs. It provides that optional platform with slight modification.

Who knows yet, money is tight, LOL

Thanks for all your replies ADA'ers, it's very much appreciated from yous all, I just need to make a decision. 

   

[rnolan]

Hey Rusty good to hear, and nice one with the fan and sensor  , BTW EL34 = 6CA7 last I looked, but hey maybe there are differences in their construction that make some difference.

[El Chiguete]

Here's the part I have trouble with:

While the MP-1 input stage is tube-based and therefore gives you all the nice interactive responsiveness, touch, etc. for your guitar, the output is solid state!  That output design dictates what response you will see in your power amplifier.

Yeha???

[rabidgerry]

I like how Rusty has stuck up for a much maligned 8008 valvestate.

I am glad you explained the valvestate option Rust.  So is it just a little lo mid boost before the output?  I like the idea that you can switch between the two.  I thought of getting one before but I'm still going for this
http://www.thomann.de/gb/harley_benton_gpa_400.htm

I will keep my Crate Power Blocks as option B as they are now sought after since they stopped making them and also they can come in handy should I not find cabs at a venue that will work as well with the Harley.  It's a copy of the Rocktron Velocity.

I heard the 8008 had an issue with melting down.  But the info I read said if you bought one now it would be more than likely one of the models that wasn't defective if it had survived until now.  The fan idea is f**king genius BTW.

[Rusty]

Cheers RG, I could go higher with the fan mod, The 12V fan that I installed sucks 3 cubic meters or air per minute.  I might even put another one in and get a breeze going on inside .

I cannot afford to cook another GMaj 2 at the moment.       I learned the hard way with the Marshall 20/20. That amp got so so hot man I could fry bacon and heat my kettle on top of it. 

 

[rnolan]

Here's the part I have trouble with:

While the MP-1 input stage is tube-based and therefore gives you all the nice interactive responsiveness, touch, etc. for your guitar, the output is solid state!  That output design dictates what response you will see in your power amplifier.

Yeha???

Well to some extent, if the SS part of the circuit is analogue (which it is for MP1/2) (e.g. opp amps and so forth) as long as it's transparent, and can cope with the dynamic rage of the tubes (again MP1/2 have no problem), then the original signal shouldn't be coloured by that gain stage, it's more a pass through buffer ? My take.

[El Chiguete]

So how is that output stage on a regular amp that is has an all tube preamp (what we are talking about beeing solid state on our ADA Preamps)?

And Marshall... could this be a mod to change it to what it is on an all tube preamp?

[rabidgerry]

So how is that output stage on a regular amp that is has an all tube preamp (what we are talking about beeing solid state on our ADA Preamps)?

And Marshall... could this be a mod to change it to what it is on an all tube preamp?

Why would you want to change things?  That's just the way it is, and it works and we all like MP1 sound so why would we want to change this?  If it was a worth while mod someone would have came up with it by now.

As for what amp you choose for amping your MP1 solidstate and tube both work.  I'm not going to get into another SS vs Tube discussion because I know SS works just as well and personally I find it easier to use an SS. 

[rnolan]

Hey El, it depends on the amp and to some extent the year it was designed/made etc, there are so many designs  over many decades. The older tube heads e.g. my '72 Marshall 50 I suspect has no solid state components (but depends what we mean by SS). It has passive eq (an area many newer amps use SS components for, particularly for active eq). Passive eq like that is basically a "cut" filter, it doesn't boost (well my understanding of it).  So over the years, analogue SS bits and bobs have been included after the initial tube gain stages for eq, FX send return etc, partly because they are easier to get output and input impedance's right (e.g. FX send return) but before the phase spliter tube (which splits the signal into +/-) for the push pull output tubes (class B, Class A does the full signal in one (or more) tubes so no crossover distortion but harder to get higher output). (you may recall the excellent article SC posted IIRC re phase spliter tubes and how 12AX7s are a bad choice for that job as good phase spliters are higher current (not gain you have that already) to feed the output tubes (and 12AX7s are high gain lower current compared to say a 12AU7) the article was discussing getting distortion from the tube output stage, with a MP1/2 there is no need for this, but you could if you wanted to  ).

[rabidgerry]

it's only the idea of it bein SS that has alarmed El.  If he was none the wiser would he have thought to change it?

No

Before you knew it was an SS output where you happy EL?  Yes?  Then why you wanna change it?

I'm with guitarbuilder on this.

[El Chiguete]

Guys is not that I want to change it is just that since I've never heard of that I was just posting random thoughts that went thru my head and wanter Marshall to tell me if he ever thought this was needed or could be done... BTW I still dont get the difference between that part of the MP-1 circuit and older all tube preamps, I'm just trying to learn more of this AWESOME preamp family that we all love every day! I believe that knowing more how our gear actually works makes me get the most out of it and better tones... for sure it help me!

[MarshallJMP]

Well there's no way to mod it into an all tube preamp.But the most important thing,the distortion circuit is all tube.
So what's the signal flow in a electronic standpoint of view.Guitar goes to a SS input stage (FET-transistor combo).Then you have the OD1 circuit opamp U4 and a vactrol for the volume.The U4 has clamping circuit so the output voltage is limited to about 9.5V (at this voltage the OD1 led will lit up).If set higher this circuit will act like an overdrive pedal.The output goes to a depending on the clean/distortion tube voicing,either full or mid boost,to the input of the tubeboard.On the other hand the out of U4 goes to the SS clean circuit.The outs of the SS and tubeboard goes to the U13 which is a dual electronic pot.Depending on the setting (SS or tube) one pot is active and the other one is set to zero.Then the signal goes to the tonesection which is active (so you can boost and cut,almost all tube amps have passive tonesections where you can only cut).Then the signal is split and it will go the the send out of the effect loop (so there's always a signal at the send out,no matter if the effect loop is on or off).From there it goes to an electronic switch  that sets the loop in or out.Then it's split again to the output stage and the chorus which will be mixed (at U11)with the output signal when it's on.After that the signal is split again goign trough a filter and then to the headphone out and to the front vol pot which goes to U10 opamp which acts as a impedance transformer with an output impedance of around 100 ohms and this signal ends up at the output jacks on the back.

So that's it in a simplified way.So there's no way you can make this all tube.

[rabidgerry]

good old Solid State is everwhere