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Firstwatt F6 build


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--- many of these builds are Class A circuits so they run hot, some very hot so they require many square inches of heat sinks. Look at all the Nelson Pass First Watt chassis - they are all identical and large with lots of heat sink and a lot of empty space inside. All Class A, all run hot. 

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Guest wdecho

As Richieb B said all are class A requiring huge heatsinks. In class A/B the transistors idles at minimum setting till needed to be turned up so smaller heatsinks can be used. In class B the transistor is cut off till a signal comes in. In class A the transistor is wide open going full speed all the time. It is call the biasing of a transistor. The more output transistors running wide open the bigger the heatsinks required for adequate cooling. Very inefficient but the most linear of all types of amplification. Mostly for purist wanting the best. 

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8 hours ago, jwc said:

Why are these DIY amp chassis so freakin" huge?  Does anyone know of a supplier with a more visually appealing chassis?

 

Heat sinks for class A amps need to be large enough or components will burn up 

So the casing is made to the size of the heat sinks 

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I get it.  I couldn't tell the size of the heat sinks relative to height of the case.  But maybe a case that is a little more attractive.  Just Curious.  I don't want to steer too much off topic....thanks

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On 5/5/2018 at 4:54 AM, wdecho said:

I've built both and like Full Range I prefer the M2 over the F6 with horns. The sweet part of building a Firstwatt clone is that you can now just purchase the M2 boards and stuff them and replace the F6 boards for very little money. Slightly over $100 being higher than some of the other designs because of the input transformer used in the M2. There are no culls in the Firstwatt line for diy'ers. All are great sounding class A amplifiers designed by the premier designer of amplifier circuits. Whether you would prefer the M2 over your F6 can and does depend on the music you enjoy. There is a new project designed around the M2 but not using those hard to find and expensive J-fets you may want to read about. It is hard to just build one.

 

http://www.diyaudio.com/forums/pass-labs/321925-diyaudio-watt-m2x.html

 The M2s I've seen used Encore transformers. Ive had a been time with time more than once... its a non starter for me. 

Ive heard my fair share of pass amps... I put the ACA and the F6 and Alph right up there. 

I went F6 for use use of input transformers. 

If selecting Firstwatt DIY projects, Id always recommend ones without feedback as they are a more forgiving sound :-).

 

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--- granted the the F3 is mid-way in the line of F-series amplifiers and only one of two to use JFET power transistors but Pass himself extols the virtues of JFET's "the sound is absolutely extraordinary. The F3 is by far the best single stage audio power amp on the planet, a testament to the potential of power JFET transistors". And it does sound awfully darn good. Even with a Pass Labs XA25 sitting next to it I have no plans to sell it. They are both superb in their own way, its a nice problem to have.

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Guest wdecho
5 hours ago, justinsweber said:

 The M2s I've seen used Encore transformers. Ive had a been time with time more than once... its a non starter for me. 

Ive heard my fair share of pass amps... I put the ACA and the F6 and Alph right up there. 

I went F6 for use use of input transformers. 

If selecting Firstwatt DIY projects, Id always recommend ones without feedback as they are a more forgiving sound :-).

 

A respected member on the diyaudio forum Zen Mod  who is tremendously talented loves the M2. He is called Nelson's adopted son and gets to see all the new schematics of all the new amplifiers. He flew in from a country that use that was part of the USSR, forget name, to the Burning Amp Festival last year and returned with all the parts to build one of Nelson's new amplifiers. He still considers the M2 the best of the best with his horns and has nothing but praise for it. I love mine but it is not my favorite child. A worthy addition for someone that likes to build clones. I still favor the BA-2 with the BA-3 front end. 

https://www.zenmod.in.rs/

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Guest wdecho
4 hours ago, richieb said:

 

--- granted the the F3 is mid-way in the line of F-series amplifiers and only one of two to use JFET power transistors but Pass himself extols the virtues of JFET's "the sound is absolutely extraordinary. The F3 is by far the best single stage audio power amp on the planet, a testament to the potential of power JFET transistors". And it does sound awfully darn good. Even with a Pass Labs XA25 sitting next to it I have no plans to sell it. They are both superb in their own way, its a nice problem to have.

I like my F3 as well. There is a newer version that uses J-fets called the J2. The official schematic has not been published but I doubt many will be built when it is available for diy'ers. The reason being that it uses NOS J-fets made by SemiSouth that has went out of business. When one finds them for sale they are terribly expensive. 

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On 5/8/2018 at 10:33 AM, jwc said:

Why are these DIY amp chassis so freakin" huge?  Does anyone know of a supplier with a more visually appealing chassis?

Short answer... no. Most look like lab equipment. 

There are some Jeff Roland clone chassis around... those look amazing.

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Guest wdecho

I believe there are a number of input transformers that will work, some maybe better. It would take some reading of the M2 thread at diyaudio to find answer. Another solution is just post the question at diyaudio forum M2 thread. After posting I found this answer at the forum, Just use a Jensen with the right turn ratio.
I think voltage gain of amp is around 6.  No op amp, 4N35 optocoupler. As far as feedback, post 1435 by Nelson. http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-144.html

 

http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic.html

 

Unique circuit even the best minds one the forum could not figure out how the function of diodes in conjunction with optocoupler worked. Nelson revealed the answer via Zen Mod in the thread. The M2 was preferred by Nelson with horns when introduced. 

 

Page 5 and 6 will answer some of your questions about transformers and function of optocoupler and diodes.  http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-5.html  As far as the correct number Jensen post the question on the thread and you will not have to read complete thread. 

 

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On 5/9/2018 at 11:05 PM, justinsweber said:

Short answer... no. Most look like lab equipment. 

There are some Jeff Roland clone chassis around... those look amazing.

Where is the listing for just his chassis?

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Guest wdecho

One is not going to beat the deal for an adequate heatsink chassis' at diyaudio.com. I use this one myself but one must drill and tap the holes. https://diyaudiostore.com/collections/chassis/products/dissipante-4u   For a ready to use, holes already drilled with back panel already cut and drilled go with this one in steel.

https://diyaudiostore.com/collections/chassis/products/deluxe-4u-amplifier-chassis-steel  Aluminum one is a few dollars more. https://diyaudiostore.com/collections/deluxe/products/deluxe-ultimate-amplifier-chassis

 

The price includes shipping which one is not going to get from Asia. I have searched for better deal many times without beating these deals. Before they were made available I use to buy the heatsinks and build my own case from https://www.heatsinkusa.com/   Not a easy task I would want to do anymore with the cheap prices diyaudio store has now. 

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