Lar-Mar Type II MV for EF80 Bassman Micro? Ohhhh, yeahhhhh...

King Fan

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Slight bump. My Utah neighbor @joulupukki was kind enough to drive northern Utah traffic so we could compare his JTM45 Micro (12AX7 in V1) running dual triodes (his has a 12BH7) to my Bassman Micro with a 12AY7 and EF80s. His amp sounds *fantastic.* We concluded these two amps are also neighbors -- in the tone department. As far as overall SPL, we never tried to compare, but both sounded great clean and distorted at household volumes.

The point in *this* thread, however, is his Type III MV seemed more effective in his dual-triode setup than mine had in the EF80 version. Now *I'm not sure this is true* -- our amps also have the V1 difference and possibly others -- but I'll stress again that my recommendation for the Lar-Mar is just based on my personal experience in my EF80 build. If you already have a dual-triode version, and like your Type III, feel free to curb my enthusiasm. Actually, also feel free if you have an EF80 version and like your Type III. :)
 

Bitsleftover

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Hi King Fan,
I just ordered the pot and resistors to try on my 12AU7 Plexi Micro.
I’ve had plenty of time to get used to the existing type III MV so should be easy to tell if this gives me more lower level control.
I’ll report back.
Overall, how did you find the response of the two different power sections?
My PT doesn’t have enough heater current to support another tube otherwise I’d convert to the EF80 version and I’m suffering from Fear of Missing Out!
 

King Fan

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Good for you. In reading a lot of threads about big amps and small, in a lot of forums, it sounds like lots of folks find the Lar-Mar a more sophisticated and linear MV. I'll be interested to find out what you think.

Regarding a 12AU7 vs. EF80s, I can't offer much insight. You've no doubt seen the current thread by our friend @joulupukki speculating about just such a 'lateral move' -- and the smart folks reminding him the small wattage difference involved wouldn't be expected to be make much change in volume. The difference between triode and pentode distortion is no doubt real -- and that's the main factor I looked at in choosing EF80s. But our listening test, with different preamp tubes and different MVs, was *especially* unlikely to reveal that.

I've been hoping we could get @dougsta , who IIRC helped popularize the EF80 in these parts, to drop in and offer some thoughts.... Can you just pop up to Scotland and buy him a pint?
 

dougsta

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Good for you. In reading a lot of threads about big amps and small, in a lot of forums, it sounds like lots of folks find the Lar-Mar a more sophisticated and linear MV. I'll be interested to find out what you think.

Regarding a 12AU7 vs. EF80s, I can't offer much insight. You've no doubt seen the current thread by our friend @joulupukki speculating about just such a 'lateral move' -- and the smart folks reminding him the small wattage difference involved wouldn't be expected to be make much change in volume. The difference between triode and pentode distortion is no doubt real -- and that's the main factor I looked at in choosing EF80s. But our listening test, with different preamp tubes and different MVs, was *especially* unlikely to reveal that.

I've been hoping we could get @dougsta , who IIRC helped popularize the EF80 in these parts, to drop in and offer some thoughts.... Can you just pop up to Scotland and buy him a pint?
Me and the wife have been down touring (including a wedding gig) in the south of England (1300 miles in the motorhome) then a fight over to the south of France all adding up to nice long break.
Make mine a pitcher of IPA as even the weather here in Scotland is sunny and dry.
In theory it should be just a case of inserting your preferred preamp, but getting the best sounding drive from the PI to the output tubes/OT/speaker is an art!

@King Fan - sure would be great to hear some sound samples your new amp!

I've been 'working' on a Fender Reverb 6G15 clone including winding a custom OT for a 150Ω input imp tank (as used on solid state drivers) and trying a bunch of junk box tubes, inc the EF80. I'll do a write up soon.
 

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King Fan

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Me and the wife have been down touring (including a wedding gig) in the south of England (1300 miles in the motorhome) then a fight over to the south of France all adding up to nice long break.
Make mine a pitcher of IPA as even the weather here in Scotland is sunny and dry.
In theory it should be just a case of inserting your preferred preamp, but getting the best sounding drive from the PI to the output tubes/OT/speaker is an art!

@King Fan - sure would be great to hear some sound samples your new amp!

I've been 'working' on a Fender Reverb 6G15 clone including winding a custom OT for a 150Ω input imp tank (as used on solid state drivers) and trying a bunch of junk box tubes, inc the EF80. I'll do a write up soon.

Thanks. Your summer travels sound great. And the pic! That's something nearly as rare as the old joke's “drummer driving his new Porsche“ — tanned Scots!

I'm working on a sound sample, I promise. And I’m really interested in your point that getting 'the best sounding drive from the PI to the output tubes/OT/speaker is an art.'

In that regard, do you have any thoughts for our friends with the 12AU7 versions of these amps who are wondering what they'd 'gain' (or lose) going to EF80s?
 

Lynxtrap

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I'm the opposite of an expert, but, on his 5E3 mods page, Rob notes it's about PI gain: "Placing the MV after the phase inverter is the standard location for most amps because most other amps use the long tail pair (LTP) phase inverter which is a true gain stage. Having the master volume after the PI is more effective for controlling output volume in amps with long tail pair phase inverters but adds nothing to the 5E3."
I don't really get that description.
MV's are placed post PI to get overdrive from the PI in amps where the preamp doesn't produce overdrive on its own. It doesn't really matter if the PI produces gain or not. Same thing with cathode followers, they are not gain stages but can and do produce overdrive in some high gain circuits.
Now, overdriving a cathodyne might not sound very good, but that's a different story.

I would also argue that pre PI is the "standard location", as most amps with master volumes have preamps that create the overdrive. PPIMV are more of a "boutique" or DIY thing added to get some overdrive from low gain amps without the corresponding dB's. It's always a bit of a compromise since no PI's are designed for overdrive.
 

Bitsleftover

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The parts I ordered from hifi collective turned up in less than 24 hours and I’ve just installed them. WOW! Just WOW! I rarely used the type III. Instead I just left it on 10 and controlled volume on an attenuator. But this is great. Full linear control. All the way from fire-walled right down to silent. But without the dead spot between 7-10, and without going from “still quite loud at 3” to zero.
I can’t compare tone properly because my new wife has a costumer in at the minute, but as the KingFan says. It’s head and shoulders above the type 3! Outstanding!
Happy Saturday Brothers.
 

Bitsleftover

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Me and the wife have been down touring (including a wedding gig) in the south of England (1300 miles in the motorhome) then a fight over to the south of France all adding up to nice long break.
Make mine a pitcher of IPA as even the weather here in Scotland is sunny and dry.
In theory it should be just a case of inserting your preferred preamp, but getting the best sounding drive from the PI to the output tubes/OT/speaker is an art!

@King Fan - sure would be great to hear some sound samples your new amp!

I've been 'working' on a Fender Reverb 6G15 clone including winding a custom OT for a 150Ω input imp tank (as used on solid state drivers) and trying a bunch of junk box tubes, inc the EF80. I'll do a write up soon.
Punching well above your weight there Doug!
 

GlideOn-Designs

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LarMar is superior to Crossline in everyway, period. It makes your amp 1000% more versatile with little to no compromise in tone.

Many are apprehensive to do because it is a p.i.t.a. to install but like the good mantra says: "You do it right, you only have to do it once"
 




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