3 quistion in 1 ! ZV4 - Buffer - BoSoZ volumepot

[lykkedk]

Hi.

After living, with my LeachAmp since 2001, I decided to go crazy , and build a pure class A amp. Well after a lot of reading the last few day's (Including 1hour telephone conversation with Magura). I am in love with the ZV4 (not that Magura told me too ) I decided to go with the ZV4, but as usual, when i go build something, i have some quistion's, which i would like to solve.

1. In the part's list of ZV4 the value (and the digikey value as well) say's C8, C10 = 0,47 uF, but when i have a close look at the picture of the board, it say's 0,22 uF look here PICTURE or am i missing something ?

2. When planning on running this setup as 2 x mono blocks balanced, i need 4 pcb ?

3. I mean, when looking at the board, it say's +in and -out, so all i have to do, is make four equal, and use 2pcs. for +in / -out and 2pcs. for -in / +out .Right ? One of each in each monoblok ofcause !

4. At the time writing, my BoSoZ, is running unbalanced, with a stereopot attached at the OUTPUT. Well i haven't got any balanced source's (and don't plan to), but if i move the stereo-volumepot, to the INPUT side, i guess the thing will work, feeding the balanced not yet buildet ZV4 fine. Right ?

5. I have been reading about the 'buffer for blues' HERE
But really i can't figure it all out... I have some spare 2sk170BL + GR types, could they be used ?. And how do i connect it to, the ZV4 circuit ? (There are some deviations on the schematic Nelson posted in the thread, compared to the ZV4 circuit)

Well it's 5 quistion's

Jesper

[Nelson Pass]

1. C8 and C10 are just high frequency decoupling caps - use any
value that makes you happy.

2. You need 4 pcb.

3. Yes.

4. More or less, right.

5. Buffer for Blues uses P channel JFET. Try a 2SJ108
or similar

[lykkedk]

Thanx... For clear reply's.

About the 2sk170, i forgot it was a n ch. - sorry for that ...

4. More or less, right.

Is there something, i could do better ? I mean i throught the bosoz worked as a unbalanced to balanced converter...

[Magura]

Yes there is! Leave the pot on the output side. That way you attenuate the noise generated by the pre-amp, othervise you will only attenuate the signal, and have max. noise at all times.

Magura

[lykkedk]

Yes there is! Leave the pot on the output side. That way you attenuate the noise generated by the pre-amp, othervise you will only attenuate the signal, and have max. noise at all times.

That's make's sense to me, thanks Magura... The reason i would have liked the other idea, was, that i could avoid buying a 4-decks attenuator !

THIS is from the ZV4 paper's :

If you manage to cool the amplifier very well, you can consider whether you can get more power out of it. I would say the practical limit to this will be Q1, which is run at about 44 watts with the 2 amp bias. Personally, I hesitate to operate this device at greater than 50 watts, but you can crank the supply voltage and bias up higher if you want. With the IRFP044 I would not exceed 50 volts on the regulated supply. If you want to try higher, I suggest the IRF140 or 240 devices.

More bias is easily provided by replacing R1 with .47 ohms, which will give you 2.8 amps, enough to probably get 50 watts into 4 ohms and 100 watts balanced into 8 ohms. Beyond this, you can expect some excitement. If you do replace R1 with .47 ohms, I suggest R16 at 2 K ohms or so.

As i see, i will have to bias the irfp044 into 2,8Amps for getting 100w/8ohm out of this amplifier RIGHT ?

Anyway i would like to tell, that the reason, i would make a balanced set, is that i have some 'heavy' loudspeaker's to deal with. Thoose bear's really give me some punch when playing loud !

Attached a picture of my 'Bears'

[steenoe]

Since the ZenV4 "just" gives 25 watt's, why not opt for an Aleph 5? 60 watt's will surely bring you a lot closer to a dynamic sound on those speakers!! As it happens, I have a pair of Aleph 5 boards, that I dont need anymore Fully populated and tested! I might be pursuaded to sell them!

Steen

[lykkedk]

Steenoe you got mail !

[Magura]

Ha ha, hate to say I told you so



Magura

[lykkedk]

Magura I could have told myself, youre allway's right...

Well, The last word haven't been said yet...

Jesper

[Magura]

Originally posted by lykkedk


Well, The last word haven't been said yet...

Jesper

No, I'm still waiting for the moment youre gonna ask if anybody have a couple of AX boards to spare


Magura