What amp to drive my Magnepan 1.6

[Audio Zen]

These are 4 ohm planars that like a LOT of power to hear its full potential. I currently have them driven by a 600 watt per channel Class D amp and hotrod Mez DCB1 preamp. I also have a 250 watt per channel Class D amp that is warmer but does not control bass as much as the 600. So from what I can gather, Pass amps sound more powerful than what their spec. calls for. I have read that the F4 is a sweet sounding amp and from what I could piece together, the BA is more modular. But how do I get either to push out 100 watts per channel? I would like to house whatever solution in a single Deluxe 4U chassis from the the DIYAUDIO store and would like to keep costs down to a minimum.

I am new to amp building, can solder and follow instructions - I need advise as to what all I need to get to my target of 100 watts. Searching forums has not yielded any noob guides although 6L6 guides are great but for a beginner that wants to know how to piece it together, I came up short.

So to get it kicked off, I know a chassis with huge sinks is needed. A powerful transformer depending on pcb solution. PCB for either F4 or BA and if BA a gain stage pcb PLUS bias and output pcb. What about universal power supply available in the DIYAUDIO store? This should get me a build but from what I can tell F4 is only 25 watts per channel and I have no idea about BA - no specs are listed in the store. So how to get to my 100 watts?

So as you can see this is where I am struggling...

Thanks in advance
Neville

 

[6L6]

So how to get to my 100 watts?

Contact member ' Zen Mod ' buy his "Pumpkin" preamp. Build it. This is a preamp that has sufficient gain and balanced voltage outputs to drive an F4 to max output.

Build (2) F4 amps. Run them as monoblocks, using the balanced output from the Pumpkin preamp. They are now running bridged, and each F4 will make 100W into 8ohm, more into 4ohm.

The only way you can get 100WPC from a 4U single chassis is to not build a class-A amp. Look at the 'Honeybadger ' It's quite nice. http://www.diyaudio.com/store/ampli...badger-class-ab-amplifier-circuit-boards.html

The Burning amps are quite modular and can be anywhere from 20WPC to 50-ish. In a 4U chassis and stereo, you would be hard pressed to make more than 30WPC before you run out of heatsink, and that would be at lower than optimal bias.

 

[Zen Mod]

4U or (better) 5U Modushop chassis will host bal F4 nicely , with biasing up to proper htsnk temperature ....... no need to go all the way up , making welder in A class

there is no Klunk!

however , having more than 3 mosfet pairs per side (or 3 pcs per quadrant) will help , counting on fact that each side will see some 2 ohms of load , while maintaining A class (prior to no Klunk! )

so - bstrd between classic F4 (balanced) and some BA3 OS iteration ....

just short conclusion - one (bal) "F4" per case .........

 

[Audio Zen]

Thanks for input.....when referring to balanced - I cannot help but think this is a term NOT related to the input connector but rather 2 monoblocks? And having said that the only way to get close to 100 watts is monoblocks?

Is the honeybadger as simple as the F4 or F5 build?

 

[Zen Mod]

Thanks for input.....when referring to balanced - I cannot help but think this is a term NOT related to the input connector but rather 2 monoblocks? And having said that the only way to get close to 100 watts is monoblocks?

.....

in this case - balanced means - two SE output stages bridged , thus balanced

if substantial A class portion of power is desired , then monoblocks are must - heatsinking demands ;

presuming you'll not go forced cooling (vent assisted heatsinking) route

if yes , Krell KSA50 as fine example of needed hardware

on other hand - take a look on PL XA30.5 ....... and read tech data ( so much things written between the lines ) :

https://passlabs.com/products/amplifiers/xa.5/xa30.5

An externally hosted image should be here but it was not working when we last tested it.

 

[Nelson Pass]

That will probably get you a couple hundred a channel into 4.....

 

[Zen Mod]

nasty ampsesssss

 

[cyclotronguy]

I was chatting with one of the Pass Labs dealers at CES-2012 who mentioned that he took a Pass INT-30a to a "show and tell" evening hosted by his local audio club.

This was at a club members home, Maggie 20.1's.

The little INT-30a apparently did something that most of the big amps couldn't to with the the Maggie's....together they filled the room with music...... and apparently it wasn't a little room by anyone's measure.

Just relaying a story, I've known the dealer for many years and he's always given me good advise.

Cyclotronguy

 

[sakellogg]

20.1's and a int-30a......

i would buy a ticket to that.

 

[Zen Mod]

yup ; 30W/A class

panties off / AB class

ladies and gentlemen ........ Klunk! time !

 

[Audio Zen]

Now that's a sexy looking amp.

6L6 was kind enough to allow me to pick his brain. He gave me an intro into class a and I am more convinced that I want a Pass amp. So far it looks like I will start with a single F4 and If I still need more oomph I will go parallel Mono's. This will be better for budget

Cyclotronguy that's reassuring knowing some have mated this with Maggie's.

 

[Audio Zen]

In process of updating the BOM for Mouser part numbers and adding some other stuff a noob like me should purchases for an F4 build....

I could not find the mA for 2sK170 - I have several matched 10mA...will this suffice?

As for the 2SJ74 and its equivalent 2SJ108, both are hard to find - is there another equivalent or is Spencer the only route?

 

[Zen Mod]

10mA - good

yup , Spencer or , maybe, h_a

 

[Audio Zen]

Thank you !

 

[6L6]

As for the 2SJ74 and its equivalent 2SJ108, both are hard to find - is there another equivalent or is Spencer the only route?

The 108s are going to be impossible to find. As for metched J74, Spencer or Hannes (member ' h_a ' ) are the only people who have good ones. I'm not sure if Hannes sells just the Jfets... he does sell full transistor kits, however.

Or you can buy sets of unmatched K170/J74 from B&D, and match them yourselves, but you would need probably 10-20 pair or so to guarantee having enough matched compliments to finish your projects. (about $100 worth...)

 

[Audio Zen]

Thanks Jim, I cant imagine whats going to happen when the world is depleted of original jfets.....every project I have built has sockets so I can easily swap out key resistors or jfets. Maybe jfets will sell as much as gold years from now?

 

[6L6]

Nah. They just will sell for $10 each. People gladly pay more than that for tubes.

Or Nelson can just start selling his stash, they will fund his retirement.

 

[Jaimo]

I have been a Maggie user for over 25 years and tried many amplifiers but never any Nelson Pass Designs- so I can't comment on this pairing.

Many people claim that Maggies need a high power amplifier - this is a fallacy, most likely conspired by audiophool dealers and manufacturers wanting to sell megabuck jewelery to audiophools who incorrectly believe that good sound comes at megabuck prices. - this 'aint necessarily so!

I ran a Bryston 4B-ST's for several years, and although not in the megabuck league, the Bryston is a well designed battleship rated at 400Wpc into 4ohms. My revelation came when I rebuilt a junked pair of Dynaco based Theta KT88 monoblocks. These amps were able to grab and control the Maggies in a way that no other SS amp I tried could ever do. It took my system to an all new level and many folks with serious high end systems leave by listening room with their jaws on the ground.

The other step up is to replace the MG1.6's crossover. I use the Peter Gunn design which sounds amazing.

Try out a good / suitable tube amp before making any commitments - you may still be converted to the bright side!

 

[Audio Zen]

Thanks for that info Jaimo. I used to run monoblock tube amps and even though they were 60 watts per channel, they drove my speakers and were musical - unfortunately I did not have my 1.6 then. Yes I have considered upgrading the crossover and will do that when I change white cloth for black. But right now I need to focus on my F4

Spencer says he has matched J74 at around 10.6 mA - will this be ok?

 

[6L6]

You don't need a matched differential pair of J74, (which is actually two J74...) that would be for an Aleph. The F4 requires a matched K170/J74 pair. Essentally anything in the BL range will be fine. 10.6 will work great. So would 7.6 . It's not super critical, other than having a good N to P channel match.