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Old 3rd March 2003, 04:58 AM   #1
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Default Zen v4 with paralleled FETs

I am planning on building the Zen v4, but with a twist - want to parallel active devices (FETs), especially Q5. What I am not sure at is how to implement the gate resistors ( one for each FET) and the modulating circuit (R25 / C11).

If I include stoppers (R23a and R23b respectively) and then connect R25/C11 between the gate resistors and the gates of the FETs, I'll be literally halving the value of the gate resistors and turning them into one common stopper, therefore the FETs won't have their own gate resistors any more.

Do you think that this is a problem and have you got any suggestions.

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Stan - wants to double everything, not halve it.
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Old 3rd March 2003, 08:00 AM   #2
Mad_K is offline Mad_K  Norway
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like this:
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Old 3rd March 2003, 08:11 AM   #3
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Well, more or less yes,but...

I was concerned mostly with the FETs in the regulated Power Supply - that was my question and in particular about the gate resistors and the modulating part of the circuitry.

Stan
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Old 3rd March 2003, 08:20 AM   #4
Mad_K is offline Mad_K  Norway
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I think you can place C11+ in the junction between R17 & R18 (ZV4 fig 3). Or you can just skip the modulating part of the reg...
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Old 3rd March 2003, 08:32 AM   #5
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You might be right, but I thought that C11 must be between the gate of the FET and the gate resistor (R18) for the modulation to work.

And I'd rather keep the modulating part of the reg because of the extra output power available.

There are several reasons why I want to do this -
1. reliability
2. using TO-220 FETs with slightly less output capabilities
2a. have more than 50 IRFZ40 FETs and would prefer to use them instead of buying new ones
3. want to bias higher - 2.8 amps
4. will be driving 4 ohm speakers, so every Watt counts

Stan
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Old 3rd March 2003, 08:34 AM   #6
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Small correction:

IRF640 for the regulator,
IRFZ40 for the output stage and the current source.

Stan
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Old 3rd March 2003, 08:48 AM   #7
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by Stanislav
You might be right, but I thought that C11 must be between the gate of the FET and the gate resistor (R18) for the modulation to work.


Stan
You can either make R18 smaller (say 100-200 ohm), or you can make R19 smaller (by the amount of R18, say 5,3Kohm if R18=1500 ohm). Then you will have the same amount of feedback to modulate it. This is what I think, it would be nice if someone else could comment on this.
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Old 3rd March 2003, 09:55 AM   #8
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Mad_K

Thank you for your input, I really appreciate it. I'll be waiting for some other members to express their opinion and then make a decision.

Slighly off topic, but related nevertheless:
Does anyone think that IRFZ40 would be suitable for a Aleph3/Volksamp 30.

Here are some details:
Vdss 50V
Id 50 A
Rds(on) 0.028 ohms
Ptot 150 W
Tj 175 C
gfs 22
Ciss 1700pF

Regards

Stan - loves recycling, hates wasting
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Old 3rd March 2003, 10:28 AM   #9
Mad_K is offline Mad_K  Norway
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The IRFZ40 will work fine! I assume you will use the in paralell.
Just make shure your rails don't exceed 50V..
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Old 3rd March 2003, 10:47 AM   #10
miguel2 is offline miguel2  Portugal
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Hi,

I built a ZenV4 and am quit happy with the sound. Latelly I been thinking in adding a differential pair input like the Aleph one. I already tried and didn't like the sound but the PSU for the differential pair was not good. Feedback had to be adjusted also.

I believe that the ZenV4 and the Aleph 3 are quite similar and interchangeable except one thing: the PSU. So if you are going to buy the transformer, which is an expensive part, I would suggest you to go to an Aleph. This puts away the caps and gives you more flexibility. But if you have (or find one quite cheap as I did) already a transformer with only a + and ground supply then build the Zen. This applies to the PSU caps as well. I really never listened to an Aleph, but I believe the output stage of the Zen and of the Aleph 3 to be not very different.

Miguel
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