Zen V4

[Per Nielsen]

Im thinking about buildig the Zen amp,
but before I begin I wants to know how much it will cost in components, because Im on a small budget, I was also thinking about if there is any of the components that are hard to get?
How large the trafos should be?
If there is any problems by building this design I should be aware of?
Anybody who has some good modifications for Nelson Pass´ design ?
Or a very good pcb design you would share with me?
Well that was a lot of questions I hope you can help me

 

[kirc]

Hi !

Me and my friend Stabist were build ZEN V4 with my own PCB design. PCB is availiable here and also some pictures and informations: ZEN V4 PCB by LEON

How much ZEN v4 was cost will tell you Stabist when he come to board.

best regards,
LEON

 

[Per Nielsen]

Thanks, nice design!

anybody else who has some ideas??

 

[till]

I built Zen V4. The most expesive part is heatsinks. I bought new and really fine heatsinks, was about 120,- Euro. Second expensive part is transformer, I used standart parts from Reichelt, about 33,- each, i used 2* 330VA. I belive 200VA would be OK also. The PCB i used the official twosided lauyout and etched at home - asked for etching chemicals at a Univerity lab - zero cost, and 2 Euro for PCB masterial. The other parts I used mostly standart, nothing exotic, from Reichelt. Not really expensive, some * ten Euros. Hard to find in germany is CL60 for inrush current limiting thermistor, but if you do a search there are people who used other thermistors. Other hard to find part is the ZVP33?? transistor, some say you could also use BS250, or ask for help in the board.

I don´t know exactly, but it wasn´t much more than maybe 300Euro for one Twochannel ZEN V4, maybe it was less.

 

[Per Nielsen]

How much capitance did you youse??

 

[till]

http://www.reichelt.de/

I used "ax 10000/63" from them.

each channel 3 in parallel of them. If you are really short on money for the project, use old heatsinks, maybe smaller with old computer fan, smaller transformers, and i think 1*10000uF each channel is absolutely enough. Even 4700 will do, because the regulator will take away the ripple.

 

[Stabist]

Hmm - after couple of weeky of living with Zen v4

Mine uses 370VA toroid - and is on full (cca2A) bias - and? The toroid gets very loud - I think it should be at least 500VA for such configuration ...
Also - that noise is exactely the hum I can hear in speakers - I know I know - untill now I should allready do some stuff to avoid that - but there hasn't been enough time to tweak it up a bit ...
I think Kirc and I will play a little with it in next few days ...

The total costs? - toroid (that's the reason for using so litle reserves in VA ratings) and heatsinks were gratis - so the big part of expences was avoided ...
The complete chassis costed me 60Eur.
And PCB boards themselves, all parts, switch, RCAs, speaker terminals, ... and PSU capacitors were around 80Eur

So - the total cost for finished ad can be seen on photos (kirc allready sent you the link) were 140Eur ...
Transistors are irfp250N by IR; capacitors are Jamicon and Wima MKS 4; resistors are metalfilm ones (xy brand) and 3W ones are 5W Vitroohm 10% ones ...
That's it - nothing exotical ...
The only thing - PSU is made with 3 Jamicons (10.000uF/50V each) ... I heard from a gay that used Jamicons in PSU - that they are gone after max 2 years of constant use - so - if that's true - it is worth to spend a bit more for a bit better ones ...

 

[till]

I did some test with my toroid transformers because of the hum/noise whatever. I don´t belive they are louder because they have to deliver more current. If i let them deliver only some hundred mA they make mechanical noise after some hours, and if they deliver some A they do also, not louder. There is a lot of discussion and nonsense on german hifiboards with highend toroids, mumetal shielded, very expensive etc - and also noise problems.

I think if the toroid is sold as good for 200VA it should be able to deliver abouit half of this without any problems.

You can´t avoid the mechanical noise, but you can mechanical decoupling the toroid. Build a pot from 4mm steel, 3-5 times the toroids volume. fill with sand or soft foam or both. Put the toroid in the middle. This helps. A 1000 VA toroid probably not - and if you want to buy a very big toroid - why noit build a very big amp with it ? more fun!

btw. of corse my ZEN V4 has full bias.

 

[Stabist]

Yeah, OK, you're right - if it makes noise allready "in idle" - then even 1000VA rating wouldn't help him! - but in my case - if no load on secondary - no hum - now in Zen configuration - very very loud ... And not getting that after some time - but right from the beginning ...

So??

I still thinks - with 500VA one I wouldn't have that problems!

 

[till]

Is this hum mechanical (ear on the toroid), electrical (ear on the speaker, oscilloscope, or both? if hum in the speaker, how many dB/1W speakers?

 

[Stabist]

The hum is mechanical - if I put my ear on the top of chassis - you can hear it quite easely ...

The same hum can be also heard on speakers - just that it is even more loud.
BUT - if one interconect is pulled out - almost nothing - speakers are almost silent ...
So - I guess there is a ground problem - there are few things I'll have to inspect - the first one is - there is no 22kR resistor yet .. Then - mr. Nelson allready sugested to ground RCA inputs ..
But - as said - there hasn't been enough time to play with ... And also momentarily the osciloscope is dead So ...

The thing is - the chassis is very compact - and it gets quite crowdy inside - so - Kirc and I must have enough time to try some solutions - it shall be a couple hours job ...

 

[till]

OK. In my opinion the only consequent thing you can do against the mechanuical noise i described above.

At the speaker, without a long antenna cable at the input, with normal speakers, you should hear nothing. Zen V2 i hear some hum. Zen V4 - nothing.

 

[Nelson Pass]

Toroids are very susceptible to crap on the AC line,
particularly DC imposed by lamp dimmer circuits and
such.

Try putting a couple of 10,000 uF caps back to back
(series) on the AC line to the primary to block DC and
see if that doesn't help.

 

[Stabist]

mr. Nelson I agree - if there is DC component - trannie can get "overmagnetized" - don't know the expression - I mean - B(H) charachteristic and stuff conected with all that ...

Series of 10.000uf caps between AC power cord and trannie if I understood you right?? Hmm - what about voltage of such capacitors?? 230V is quite high - I'm not sure if there are some 230V/10.000uF caps ... - I mean - am I missing something here or ... ?!?

 

[till]

10000uF / 63V 4 times in series => 2500uF / 250V ??

 

[Stabist]

10000uF / 63V 4 times in series => 2500uF / 250V ??

Hmm - it can be clearly seen that it has been a long long day - and that I should allready be in bed for at least 2 hours ...
I've mixed up serial and paralel .... ... Silly me ...

Oh ... I feel so

I feel soooooooo stupid ...

 

[miguel2]

I tried this weekend a DC trap with a 3300uF/25V cap and 4 diodes as in the figure. I noted that when I turned it up it was silent but then the transformer started to hum again.

I am thinking in putting it in a vacuum oven to get the air trapped inside and then bake it. Does anyone knows the baking temperature for these guys?

 

[Per Nielsen]

I really dont under stand why you have theese kind of problems, its just a question about a big enough trafo and enough capitance, then you will not have theese noise/hum problems
Please correct me if im wrong!!

 

[miguel2]

I am using a 800VA toroidal.
Caps are 20000uF per channel.

I do believe my transformer is a bit old but toroids are said to be lifetime guaranteed .

 

[Per Nielsen]

Are you sure it is your transformer that makes the hum?If it is I would not believe in that gaurantee,it could also be the grounding problem or even worse dried out caps!