Power Follower (P.Macura) some question?

[bezobraznia]

Hello,
I finaly decide build Power Follower version from Pavel Macura with DoZ preamplifer on it:
Power Follower by Pavel Macura
But i have some question:
First of all, i suceed getting original IRFP350 (IR) and TIP142 (ST)
but there, in Bulgaria is no chance getting high (even middle level) capacitors
Is there any mod possible for parts of this sheme ?
What is proposal of trimer-pot, and how i have to set it?
Is it posible for power amount 15-17VAC, because i have that type transformer around?
Is it ok if i had a chance getting 2uF (or 2.2uF) capacitors instead of 2 x 1uF?
Is there any tolerance for replace passive parts with closest parameters?
And most importand what parts are on the "way of the sound" and i have to strive replacing them with better quality?

Thank you in advance!
Best reggards
Niki / BG

 

[peranders]

Most parts aren't extremely critical in order to get it working. Try to get similar parts. If you have come up with something I'm sure people here can tell you if it's OK or not to use them.

 

[PMA]

Hi Niki,

regarding your questions:
- do you have any chance to buy IRFP240, 244?
- TIP142 can be replaced by NPN Darlington with collector current rated at least at 8A,
- the trim pot VR1 is set to obtain half supply voltage between collectors of Q2 and Q3,
- yes you can use 1uF capacitors in parallel,
- the circuit is quite tolerant to component changes, but ZD3V diode (BZX83 3V0, 0.5W), this must not be changed, see comments on my web page, that were recently added.

P.S. I have no PCBs by now, it would be necessary to start next production lot of 8 pcs at least, depends on interest.

 

[PMA]

Darlington replacement

You might try Sanken 2SD2390 as a Darlington.

 

[bezobraznia]

Uh... i feel so stupid...
i so, and so looking for a IRFP350 ... because i've read it in some other post that this is the best choice for Power Follower
BZX83 i dont finding but i find similar zener for 3V0 about 0.4-0.5W i think it will work ok
my ideia is to use not 2 x 1uF but 1 x 2uF capacitors
VR trim pots i find - many turns...
You don't say nothing about power supply?
I will search for 2SD2390's

I decide for PCB's - I will make two independant PCBs with chemical pencil and Fe2Cl3 - fully amater work LOL ...
for stereo and if amplifier is okay sounding to me after (i think) several future replace mods i think i will talk with my friends for collective order

Thank You and Best reggards from BG
Niki

 

[PMA]

Do not forget to check voltage on that Zener in the real circuit, it must be between 3 - 3.3V.
2uF capacitor makes no problem.
For power supply, you should use 500VA transformer for 2 channels. About 28Vac rms secondary.
And you can make hand made PCB - this design does not change its properties with PCB much.
Trim pot - yes, I use 10 or 20 turn pot.

 

[bezobraznia]

Very fast answer Pavel, appraise that
Ok, i will check is everything ok with voltage

And for power supply if i have to buy some trafos, i think that best choice is two independant transformers - i really like more "3D soundung scene" thanks to independent power...
And also i have some big and oldiest (but working ok) Siemens 33000uF capacitors... maybe i will use following configuration:
Transformer 250VA -> fastrecovery diode bridge -> C-33000uF Siemens -> 5000uF (Tesla) -> 2200uF (another siemens) -> amplifier... Is this good configuration?

And i will try finding IRFP240 or IRFP244 from manufacturer International Rectifier , and will make sound tests with different transistors ...
Is this correct: only IRFP n-mos make difference on sound quality, but TIP142 - no?

 

[PMA]

Regarding 3D soundstage, the most important is placement of speakers in your listening room. Keep them far from rear wall (at least 1.5m), if they are bookshelf speakers, put them on the stands. If your speakers were placed inside furniture or on a desk at the rear wall, you would never achieve 3D soundstage.

 

[bezobraznia]

hm... Pavel,
I've look at Your sheme and I think that Doz preamp is not so good choice for Power Follower... maybe he will give specific transistor sound to complette amp, but i don't want this.
Maybe some tube stage? Is it possible for You remake PCB for only Power Follower without doz-preamp on it, but with parts importand for connection Tube stage + Power Follower ? I mean that maybe PowFoll. will need some different capacitets or resistors or similar ... i really don't know...
Thank You in advance & best reggards!
Niki

 

[PMA]

Tube stage would be excessively loaded by MOSFET Power follower input capacitance.

 

[tlf9999]

Tube stage would be excessively loaded by MOSFET Power follower input capacitance.

what if you use a small signal bjt to drive the mosfet, thus isolating it from the tube?

 

[PMA]

A kind of input buffer would do the job, the case is which solution is the best one. Then it will be a new circuit, I only am not sure if this is what the thread starter is looking for.

 

[tlf9999]

what about going it out all the way with a) small signal mosfet driving b) a power n-channel loaded with a current source? Kind like one of those Zen amps.

 

[jeapel]

hi

My setup now is a source follower not the Pavel follower

but i try with doz preamp and tube preamp and to my

ears the sound is better with tube driver(with low zout).

For the bias the static(tip142) Pavel current source is fool proof

stable in my case(dynamic with feedback) i succeed to stabilize with a

small 10nF cap on gate but not easy.

www.loginnovation.com/jeapel

bye

 

[PMA]

I made the Follower for several reasons:
- much lower output impedance compared to ZEN output stage,
- lower distortion,
- listening comparison with first versions of ZEN.
This was intended as a starting project, now it is "as is". I do not assume to return and modify this project.

 

[jeapel]

hi Mr. Macura

Did you try your follower with tube driver like me

because the result is very good.

My explication (not sure) is the tube give some

more harmonics to the sound.

thanks

 

[AKSA]

Ah, Jeapel,

You like the added distortion from the tube?

How much is it? 1,2 or 3 per cent?

Why does more distortion sound better?

Cheers,

Hugh

 

[jeapel]

first i just saw my very bad english error in my last post

"Pavel current source is fool proof stable"

naturally i want to say "full proof" but

is it possible to erase a post

sorry for my bad english

 

[PMA]

Hugh -

Some like it Hot, that's all.

 

[AKSA]

Pavel,

Now that I know you are 50, this changes my approach to you considerably....... (I am 54, regrettably.)

Yes, indeed, some like it hot. I once did a mosfet with bipolar driver in CFP, with tube as voltage amplifier. In Class A, it sounded better than anything else I've ever done.

But the tube distortion was high, perhaps 2% (not measured). There was, however, just audible intermodulation on highly complex, heavy orchestral music. But gee it was nice.

Shame about the efficiency, or lack of it.......

Jeapel, your English is 1 helluva lot better than my French, don't worry about it, perfectly understandable. That's the thing about English, you can make lots of mistakes and still get your message across. Other languages are not so forgiving.

Cheers,

Hugh