Can JLH 80W Mosfet Monobloc drive an Isobarik speaker

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tonewheelkev

Member
Joined 2010
#1
As it says on the tin...can a JLH 80W Mosfet Monobloc drive a Linn Isobarik speaker?


Have listened to Isobariks in an active setting...and like them!
Wondering if my JLH 80W amps could drive them successfully in a passive configuration??


Any thoughts please...?
 
#2
Recommended amplifier power rating is in the range of 50–500 watts. Hi-Fi for Pleasure noted that the speakers' impedance, although quoted at 3 ohms nominal, dipped considerably at some parts of the audio spectrum. This made the DMS Isobarik very hard for amplifiers to drive, potentially causing many amplifiers' output protection to trip.
You need to evaluate the ability of your amplifier to drive 3 ohms. The quality of the power supply, sufficient heat sinks, the number and type of output transistors, etc.
 
#4
Having built the very same amplifier at the time , its very robust and the improvement of the power supply in removing the Darlinton BJT,s from the pass output and fitting mosfets made a very big difference.


Having said that Isobariks are indeed a real test of a power amp but believe it or not Hi-Fi Choice (now defunct ) tested a NAD 3020 with them .
The power amps "made for the job " were Naim which were able to drive them correctly , IMO the JLH 80 Watt mosfet could drive them but not to the full extent and power of the Naim,s .


As you are using JLH,s own designed power supply it has built in safety features and those mosfets (TO3 ) are very tough as I found out at the time but still I wouldn't mark it as favourite to drive those speakers.
 
#6
I don't know if you are addressing me or the OP but JLH,s 80 Watt mosfet amp has a 470n (0.470mfd ) capacitor at the input so "all stages are not dc coupled" .


I am looking at the original 1984 design & the 1989 modification version but if you know different could you post only an original John Linsley Hood design not a modification by other parties ?


The all mosfet design (signal path ) has one also .
As well as his EW "evaluation" test design of igbts.
The May 1992 igbts finished design also has a 0.47n capacitor at the input.
His EW June 1993 "integrated " design has a 0.47n capacitor at the input.


Even his "gain blocks " in teaching in articles in EW has a 0.470n capacitor at the input .


I have the original EW magazines to hand if you want to query it ?
 
#7
duncan2 said:
........The power amps "made for the job " were Naim which were able to drive them correctly , IMO the JLH 80 Watt mosfet could drive them but not to the full extent and power of the Naim,s .
Click to expand...
....and it's unlikely I'll ever make the move to those amps anyway!!

duncan2 said:
As you are using JLH,s own designed power supply it has built in safety features and those mosfets (TO3 ) are very tough as I found out at the time but still I wouldn't mark it as favourite to drive those speakers.
Click to expand...
Yes...and I think that PSU can be demanding in it's own rights.


So ...not looking like a great idea to put them with Isobariks.
Ta!!
 
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