What can I use instead of k170/j74?

[jacco vermeulen]

J313/K2013

 

[Melon Head]

So I guess that means front end unless he is a nut-case like me and uses a stack of them for output stages.

 

[jacco vermeulen]

Go look see "ugs" of the Xs models

 

[Melon Head]

Where do I look?
I am not really expecting any surprises, unless it is very much different than the XA amps.

 

[Zen Mod]

The Front End


Initially we designed a new front end that could be tweaked to produce arbitrary ratios of low order harmonics, and while this worked fine, after we finished working with the output stage portion of the design we found that it worked better to have the front end simply complement the output stage in a largely neutral manner.
The new front end is not more complex than the previous design. It still uses cascoded matched Toshiba Jfets (NOS from our large cache) for the input devices which drive complementary Mosfets.
However we have increased the heat sinking so that this stage can be biased with 2.5 times more current and brought in higher quality Toshiba Mosfets (also NOS). This dramatically increases the linearity and bandwidth of the front end, and with the proper adjustment of each part of each stage and balancing degeneration with loading gives us an amplifier front end which by itself has low distortion, a 100 Khz bandwidth and a fairly low output impedance – all without a feedback loop.
Also, the new front end has a 200 Kohm input impedance (balanced) with very small capacitance. Anything will drive it.
Feedback is not essential for this front end, but we have left it with enough open loop gain to allow some feedback around the output stage. This is strictly in service of the sound of the output stage – it already has decent specs.

entire chapter is about FE , and nothing else


in any case , I already wrote more than I wanted

 

[Melon Head]

OK
This absolutely proves you are smarter than me, and I am the dumbest person on the planet.

 

[jacco vermeulen]

No shock there.

 

[Melon Head]

Thank you Jacco

 

[Zen Mod]

OK
This absolutely proves you are smarter than me, and I am the dumbest person on the planet.

nope

fact that you're contemplating about being dumbest , clearly reveals bitter true :

it's well known that I'm the dumbest , while I'm not even aware of that

 

[Melon Head]

How are you aware that you are not aware?

 

[Zen Mod]

easy

I'm me .

 

[Melon Head]

Hi Zen Mod
Can you lend me $65,000.

 

[Zen Mod]

yeah

if you send me a ton of Toshiba's

 

[Zen Mod]

can I give you advice worth 60K$ , instead ?

 

[Melon Head]

Yeah why not.
Not sure how wise that is seeing you are dumber than me.
😀

 

[Zen Mod]

make proper spks

then make proper amp with 15W

voilla!

you don't need 150W anymore

so , I just save you 60K$

for 5K$ you can do both ............ very well

 

[Melon Head]

You are right, 100%
As soon as I finish the speakers I am working on, I will try and make something better with higher efficiency.
Maybe try out Troels Gravesen's ideas with waveguides on tweeters

 

[Zen Mod]

naah

you can do better than that , if going in under 20-watter realm

 

[jackinnj]

See page 142 of Bob Cordell's "Designing Audio Power Amplifiers" for a complementary input stage with N-Channel JFETs.

 

[Russellc]

naah

you can do better than that , if going in under 20-watter realm

What are the ZenMod speaker recommendations for this power range?

Russellc