Lar/Mar PPIMV power tube saturation?

[Ed A]

Hope you guys can answer this because I've been reading Thread after thread about this mod and I need to be clear before I install it in my 69 50W Plexi clone. For not my needs I only need to reduce volume a little bit. I use this amp with a weber attenuator. I crank the amp up to nine or 10 for full power tube saturation and I turn down the Weber attenuator only a little to about eight or nine. I do not need bedroom levels at all. I just need a little volume reduction and I want that power tube distortion! Those Mullard XF2s sound great saturated!

But I keep reading that with the Lar/mar you don't get power tube saturation. I assume people say that when speaking about playing at very low volume and I assume I WILL still get power tube saturation if I only use this master volume minimally? I am guessing that I would bring the main volume down just a little bit and start turning up the Larmar to bring the gain back in? Just curious exactly how it works and if I wanted out of the circuit completely do I put the Larmar on zero? I am considering this so I do not have to bring out the attenuator. Thanks for any help.

 

[ampmadscientist]

Hope you guys can answer this because I've been reading Thread after thread about this mod and I need to be clear before I install it in my 69 50W Plexi clone. For not my needs I only need to reduce volume a little bit. I use this amp with a weber attenuator. I crank the amp up to nine or 10 for full power tube saturation and I turn down the Weber attenuator only a little to about eight or nine. I do not need bedroom levels at all. I just need a little volume reduction and I want that power tube distortion! Those Mullard XF2s sound great saturated!

But I keep reading that with the Lar/mar you don't get power tube saturation. I assume people say that when speaking about playing at very low volume and I assume I WILL still get power tube saturation if I only use this master volume minimally? I am guessing that I would bring the main volume down just a little bit and start turning up the Larmar to bring the gain back in? Just curious exactly how it works and if I wanted out of the circuit completely do I put the Larmar on zero? I am considering this so I do not have to bring out the attenuator. Thanks for any help.

NO.
Gain must be up high - master must be up very high
to get power tube saturation.

Turning the master LOW stops power tube saturation!

Attenuator is used to lower the loudness when the output tubes saturate.
The attenuator "IS" the volume control.

Master volume only PREVENTS output tube saturation.
PPIMV only PREVENTS output tube saturation.

For output tube saturation,
The master should be on 7 - 10. The gain should be on 7-10.
Or there should be NO master volume at all! (plexi example)

PPIMV is for PREAMP distortion.
That's the only purpose of installing it.

The attenuator is (one) necessary tool for reducing the volume.
Other methods include:
1 reducing the number of speakers, use less efficient speakers.
2 Change the amplifier to Triode instead of Pentode. 100 watt amp becomes 40 watts. 50 watt amp becomes 18 watts.

The Triode method is probably one of the best, and the factory does use this method.
18 watts is surprisingly loud, it's louder than you are thinking.

18 watts is still much louder than the drum set.
Because, Power does not = Loudness!

it's the SPEAKERS that make the amp loud. Not the Wattage.

 

[Gene Ballzz]

Ed A,
^^^ All Of What He Said^^^
PLUS, I'm apparently on the same quest as you and even though I only use a "little" attenuation with a fairly high quality Weber Mini Mass attenuator, if I attenuate any more than it's minimum attenuation, I start to lose some of what I "need/want" and get bummed out!

I'm assuming that you are another kindred soul who likes his guitar generally "straight into" the amp? Us folks who depend on and live for the sound/distortion/overdrive of the amp have a tough row to hoe when it comes to controlling overall volume. You might try an advanced "search" of this forum, for my user name and threads started by me, if you are interested in some of the trials and tribulations I've been through on this quest! A lot of great info and comments from some of the most knowledgeable folks on this forum.

Power scaling, by any of the many different names, may be the only real way to go, other than changing to a much lower wattage amp. For example, I'm currently gigging regularly with either a Class5 head or a DSL5C used as a head into my 4x12 1960 cab with early 70's greenbacks! Unfortunately, I STILL get requests to turn down a little and always keep my attenuator handy for when needed!

The Lar/Mar does allow saturation/overdrive/distortion of the phase inverter, but eliminates the actual power tube overdrive. Standard "pre phase inverter master volume" eliminates the phase inverter overdrive also and leaves you with NADA but preamp distortion!
Just My $.02 & Likely Worth Even Less,
Gene

 

[jimmyjames]

I have just got myself an Aracom PRX-150DAG attenuator. I use it at home with my DSL15H and have it dialled in for full fat power tube goodness, at domestic volume

 

[Gene Ballzz]

I have just got myself an Aracom PRX-150DAG attenuator. I use it at home with my DSL15H and have it dialled in for full fat power tube goodness, at domestic volume

I've heard nothing but great things about those attenuators! Just curious, do you use pedals for overdrive and/or distortion?
Curiosity Gets This Cat,
Gene

 

[tweedman8758]

Ed A,
^^^ All Of What He Said^^^
Power scaling, by any of the many different names, may be the only real way to go, other than changing to a much lower wattage amp. For example, I'm currently gigging regularly with either a Class5 head or a DSL5C used as a head into my 4x12 1960 cab with early 70's greenbacks! Unfortunately, I STILL get requests to turn down a little and always keep my attenuator handy for when needed!

The Lar/Mar does allow saturation/overdrive/distortion of the phase inverter, but eliminates the actual power tube overdrive. Standard "pre phase inverter master volume" eliminates the phase inverter overdrive also and leaves you with NADA but preamp distortion!
Just My $.02 & Likely Worth Even Less,
Gene

I totally agree. I love the full bore of a big Marshall amp but realistically can't use it anywhere. I have also used a Class5 head with Lyle mods into a 2061x cab. It sounds amazing but it's not the same. I NEED to feel my pants legs flapping! BTW the Lyle mods make a huge difference along with a separate cab.

 

[Ed A]

Hey guys I appreciate the comments and info but I think i'm not being completely clear. I know full well how power tube saturation happens, I've been playing for 40 years I've had tons of vintage equipment both guitars and amps and still do. I have a 69 100W Plexi and at 71 50W that will remain stock. The 69 50W clone is my amp that I would not mind modding if necessary. As I said this plexi clone I love the way it sounds dimed. But I need to lower the volume just a little bit with the attenuator which is working great. And maybe that will be my only solution. But I was assuming and maybe I'm assuming incorrectly that with the master volume I could still have the amp quite loud but of course not with full tube saturation, maybe turned up to 7 or 8 and use the added ppimv to bring back in some of the gain I've lost by turning down the volume a bit. But again someone here mentioned that the PPIMV eliminates power tube saturation. I don't understand how that's possible as long as I'm still cranking the amp fairly well. Am I missing something? Again thanks for the input!

 

[mickeydg5]

Hello Ed_A

The PPIMV will allow the amplifier to achieve full preamp gain which will overdrive and distort the signal while dropping the overall output of the power tubes. So the power tubes will be cleaner as you turn down the PPIMV but the signal feeding them will still be sizzling.

The PPIMV will give more adjustment for trying variances but you will loose power tube and OT saturation as it is turned down. Only the use of an attenuator after the OT will allow for maximum saturations.

 

[Ed A]

Hello Ed_A

The PPIMV will allow the amplifier to achieve full preamp gain which will overdrive and distort the signal while dropping the overall output of the power tubes. So the power tubes will be cleaner as you turn down the PPIMV but the signal feeding them will still be sizzling.

The PPIMV will give more adjustment for trying variances but you will loose power tube and OT saturation as it is turned down. Only the use of an attenuator after the OT will allow for maximum saturations.

Okay but one of the advantages of Read about this master is that it can be adjusted to be completely out of the circuit. So if turning it all the way up is over driving the preamp section then it's not out of the circuit. But somebody else here said that turning it to zero won't work either. Could someone explain where you set this if you want the option of not using the master volume at all if I feel the need to crank with no drop in volume?

 

[mickeydg5]

Okay but one of the advantages of Read about this master is that it can be adjusted to be completely out of the circuit. So if turning it all the way up is over driving the preamp section then it's not out of the circuit. But somebody else here said that turning it to zero won't work either. Could someone explain where you set this if you want the option of not using the master volume at all if I feel the need to crank with no drop in volume?

No sir, it is a master volume. Zero is nothing, no sound, and ten is maximum volume just like on every other type volume control.

Placing anything in or along the signal path will have some affect but basically setting the PPIMV on "10" is maximum volume, closest thing to taking it out of the circuit.
Lowering the PPIMV, from "10", allows you to maximize the PREAMP VOLUME(s) which overdrives the preamp and PI tubes while attenuating the signal to the power tubes.

 

[Oatie]

I played my 1970 JMP50 Smallbox tonight w/Lar-Mar PPIMV and I used a Mil-Spec PEC Dual 250K Pot for my MV and installed it in the Polarity Switch location since it's not used with the Grounded 3 prong cord. Makes it easy to adjust from the front. The better quality PEC Pot helps a bit since the signal passes through it. I also installed Sprague Vitamin Q .22-1000v. Snubber Caps in the amp and the PIO Caps help give a nice clean signal in the system. These are the good ones with the metal housing and the glass end caps from 1960s old stock. I use them on all my replacement snubbers.

If you go for the Lar-Mar, I would suggest the PEC Dual 250k Pot and high quality Carbon Fil 2.2M Resistors. A Few ebay sellers have 2.2M 1% Carbon Film Resistors and they are well worth it for this application.

And I use a 3-Wire Shielded Mil-Spec Real-Silver Tinned Teflon Wire, this stuff is really good for shielding the wire to help make it quiet. Makes a clean install as well, no need to strap 2-wires together. The 3-wire gives you a clean install under the board with short leads coming out the shielded sheath.

And I install the 5k6 swamp resistors on Pin5 of each EL34 socket.


Smallbox on the top, came from the Music Shop Joe Perry bought his first amps from.

Silver tinned shielded wire, each strand is silver tinned and 20 Ga., they make a 22 Ga. and a 24 Ga. as well, the 22 Ga. works well also.

 

[bulldozer1984]

Laymans terms

A standard Marshall master volume is BEFORE the phase inverter. When you turn it down, you reduce the signal to the phase inverter and power tubes.

A PPIMV is just like moving the master volume to a position that is AFTER the phase inverter.
Therefore, when you turn it down it only reduces signal to the power tubes. Therefore, no matter where the PPIMV is set you get the tube in the phase inverter position to also distort. It like adding another gain stage but only at lower volume. Once you turn it up to a certain point, a PPIMV makes no difference apart from the components themselves altering the tone.

A PPIMV makes the amp distort more at the same volume as if you were using a standard (pre phase inverter master) volume because you are getting full signal to the phase inverter tube.

If you put the LAR/MAR PPIMV to 10, it is essentially out of circuit.

 

[jimmyjames]

I've heard nothing but great things about those attenuators! Just curious, do you use pedals for overdrive and/or distortion?
Curiosity Gets This Cat,
Gene

I only got it two days ago, tried my Maxon/Ibanez SD9 between PQ9 parametric and GE9 graphic EQ pedals. I took the SD9 out and just have the EQs in front. Gain on amp is way down at 1, master at 7, sounds much better like this. I've still to try the green channel through it, may use an OD or two then. I've got the SD9, an STL and a Keeley TS9DX to choose from The Aracom has been built to a very high standard.

 

[Ed A]

Thanks guys, this is much clearer now. And thanks Oatie for the details on the parts and the great pictures!

 

[peterichardz]

In my opinion, the only way to get the cranked thru the power tubes....thru the speakers sound.....at a lower volume......is thru a proper iso cab.....with the signal split....one to the house.....and one then re-amped thru a clean amp set to the level you want on stage!

 

[Ed A]

Oatie. Can you tell me where you purchased the Pec pot and the Teflon wire? Thanks much appreciated.

 

[GIBSON67]

I love my Lar/Mar PPIMV. At almost full volumes, you will love it. Try it out, it is just a few dollars in parts and for a clone...who cares if you mod it.

 

[Oatie]

Ed,

You may want to try this new style MV, It's called The Rich II Mod, it's been around for a while but improved now.

George at Metro Amps is only using this MV now, and that says a lot.

You don't need to remove your 220k resistors, you leave everything in place, you just unsolder the two ends on the two .02/400v caps and connect them to the Pot Terminals as shown in the drawing.

Here is the Link with the info,
MetroAmp.com Forum • View topic - Dual 500k PEC Pots for PPIMV

You can buy the 500k PEC Pot at ValveStorm a great place to buy Amp Parts. The Wire is the best hookup wire. The Shielded wire like I showed you, you can get on ebay. Just make sure it's the real silver tinned. Some guys sell the Teflon wire with bare copper strands, it';s not the same.

PPIMV Checklist | ValveStorm

PPIMV Step By Step Instructions:

http://valvestorm.com/sites/default/files/PPIMV Step by Step.pdf

 

[mickeydg5]

That is not new style and has been around for a very long time.
A better version or PPIMV, in my opinion, uses 1M instead of 500k and has coupling capacitors split being both before and after the volume control with ground actually attaching to chassis ground..

 

[Oatie]

The Rich Mod is old, the Rich II mod is the one George at Metro uses on his builds now.

They only carry the 500k PEC at valvestorm now, they pulled the Lar Mar PPIMV info at the Metro site.

I'm installing one now with some Sprague Vitamin Q and then trying some old stock Hovland .02/1000v. coupling caps.

Will be interesting to hear what cap sounds better.