Zenductor

[Vix]

The other channel, work in progres...

 

[Vix]

Done.

 

[Zen Mod]

impressions now, when you're listening with both ears?

 

[Vix]

Hopefully tomorrow.

I intend to compare Zenductor to MoFo which I use now (19 V switcher, 1.7 A bias) + Jfet Boz (J310 - that's what I preferred).

On the other hand, I was envisaging to use the Zenductor only with the (B1) buffer, but it seems that there won't be enought gain. But it seems to go nicely with Frontend 2022, so it will go with that one.

So, two simplest and perhaps cheapest class A amps on the planet, head to head
Which one is better?

Psst, I know the answer: the SIT one, but it is not here (yet)

 

[Vix]

Being compared. Uh, oh. When you like two ice cream flavors, which one do you chose?

 

[Vix]

Ok, so...
Both are good. Seductive.
I think I will leave MoFo (+Jfet Boz pre). MoFo sounds a bit cleaner, with a bit more depth of the soundstage, voices sound a bit "calmer".
Zenductor. I could liaten to it as my only amp, no problem. Sounds very nice. A bit more forward presentation , and a nice bass.
Not easy to choose between the two.
At the same time, I acquired some old fullrange speakers. With no baffle, sound spooky...
Ghost musicians playing in my room

 

[e_fortier]

Hi

I’m planning to use this amplifier at 19Vdc, 1.5A, with the higher bias of 1.5A resistor R1 will heat up more compared to the original design, is 3W still sufficient? I’m aiming to buy a 5W but could only find 0.5 ohm instead of 0.56 ohm, is this ok ??

Thanks
Eric

 

[Stanislav]

0.5 r is perfectly fine. You need to drop 0.75v across that resistor to get the 1.5A flowing.
Now 5W is better than 3W as at that current it will be dissipating around 1.2W and I personally like it to dissipate no more than 1/4 its rated power.
Just my 2c.

 

[e_fortier]

Thanks Stan, I’ll go with 0.5R, 5W 👍

 

[e_fortier]

Here we go, revised PCB with proper thanks and Gerbers files for the ones who can’t wait. PCB not tested yet but I’m confident it will work fine. Change R5 for the LED brightness depending on your taste, I’ll change it for a 6K8. Also, this version is slightly more powerful and intended to work with a 19Vdc power supply biased at 1.5A

PCB size made to suit my needs which is an odd heatsink shape with a narrow (52mm) opening…PCB is about 50mm x 100mm max.

Eric

 

[e_fortier]

Quick question

If I use let’s say a MOT (60mH) instead of the Triad choke rated at 35mH will there be a huge difference in bass response? No big deal if I lose a few Hz, just wondering the overall bass response difference between both chokes…

I’d like to stick to the original design but would rather save some money and not purchase a pair of 35mH if the MOT is much better.

Thanks in advance
Eric

 

[pinholer]

More inductance will mean higher load and should result in better bass response. One thing to check is the DC resistance. This will affect the voltages.

 

[e_fortier]

The DC resistance of both chokes is around 0.7 ohm.

 

[jostwid]

Regarding bass response and choke inductance.
Have a look at post #336
The combination of choke and output resistor is important.
The choice that Nelson and Mike made for Zenductor results in a nice bass boost.

 

[e_fortier]

Thanks a lot, I wasn’t aware of that part of the thread 👍

 

[jostwid]

Ooops!
Just realized one of my tongue or mind slips. Regarding post #336 its the values of choke inductance and output capacitor that determine the bass response...
Sorry for that

 

[Nelson Pass]

The choice of the Triad inductor was very simple - it's the only one
we've seen at a decent price...

 

[e_fortier]

A new pair of Zenductor monoblocs are born 😀
Gerbers in post 450 can be used until the store releases the official one.
Please note that the bias pot has been wired in reverse so clockwise will decrease your bias..as usual just start with the wiper in the middle.
Very nice sounding amp, thanks Mr Pass 👍
I had to put the Wayne BA2018 in order to increase my output power.

Eric

 

[e_fortier]

Hi @Vix

Have you had a chance to measure the output power into 8 ohm (just before clipping) when biased at 19Vdc, 1.5A

I tried to check it earlier but the clipping was asymmetrical (more than usual) the negative part was clipping way earlier, it got better when I increase the bias but I’d rather keep it at 1.5A

Is there anything I can do to reduce such a big asymmetry when it clips ?

Thanks
Eric

 

[Ben Mah]

Single ended amps typically clip asymmetrically.

Increasing bias increases power output so clipping occurs at a higher output voltage, up to a point governed by the power supply voltage.