Which pre-amp to build?

[HooRide]

Hello all, i've spent a few months searching the net for a high quality pre-amp schematic for me to build. I started off wanting to build an op-amp based one and have now wound up here asking for opinions on which class-A design would be better.

The designs in question are the ever so popular Bride of Son of Zen and this one: http://www.geocities.com/capecanaver...23/preamp.html

Your opinions and experiences are greatly appreciated.

[mg16]

I can unhesitatingly reccomend Nelson Pass's Bride of Zen preamp. I built mine 3 years ago using run of the mill parts and my jaw dropped to the floor when I first heard Pink Floyd playing in my living room. Yes,it sounded like they were in the room with me. I had never thought a preamp could make that much difference.
If you build it though, don't use the 500 ma. transformer reccomended. Use a 3-4 amp torroidal Avel Lindberg, with 30+30 secondarys. Makes a huge difference in sound improvement. Also fast/soft recovery diodes in the power supply circuit are worthwhile.
Just one opinion though.
mg16

[paulb]

Originally posted by mg16
...my jaw dropped to the floor when I first heard Pink Floyd playing in my living room.

You've got my attention. What are you using for a power amp? And is your BOZ's power supply regulated?

[Edited by paulb on 12-09-2001 at 08:00 PM]

[HooRide]

I was leaning towards the BoSoZ anyways, so now i'll set it in stone. Where can one buy an Avel Lindberg transformer? And how much would a 3A one cost? I was going to buy the 182L60 (60V @ 2.5A per winding) http://www.hammondmfg.com/182.htm for about $60.

Also, since you have built one, what did you do for your volume control(s)?

Thanks.

[mg16]

At the time, 3 years ago, I was using a Quicksilver GLA tube amp. I am now using Doc Bottleheads 2a3 Paramours, with full upgrades. The Boz circuit board includes on board regulation. Yoy can buy Avel Lindberg transformers online. Do a search using Avel Lindberg, and you'll get the web site link. Pick from the 400 series transformers at there site. Use one with dual primarys of 115v, and dual secondarys of 30+30 at 3 amps minimum. Also try the soft recovery/fast recovery diodes. I got mine from Mouser for about $1.00 each.
I used holco 1/2 watt resistors. Panasonic tsu series elec. caps. Caddock t0-220 package 1k drain resistors, and MIT input and output coupling caps. Use 5k or 10k,(max), Clarostat pots at the output of the preamp.
Best of Luck
mg16

[GRollins]

http://www.avellindberg.com
http://www.plitron.com (another good transformer source)

Grey

[alaskanaudio]

Originally posted by HooRide
Hello all, i've spent a few months searching the net for a high quality pre-amp schematic for me to build. I started off wanting to build an op-amp based one and have now wound up here asking for opinions on which class-A design would be better.

The designs in question are the ever so popular Bride of Son of Zen and this one: http://www.geocities.com/capecanaver...23/preamp.html

Your opinions and experiences are greatly appreciated.

HooRide,

I had a few spare moments and plugged the circuit you linked into Multisim 2001 Pro.

My simulated currents were a little higher than the numbers listed on the diagram. Mine were around 75 Ma per device.

At normal listening levels with .25 Vrms input to input level the output voltage will be about .444 Vrms out on each output when loaded with a light load of 10 Kohms.

The distortion will be primarily second harmonic at at level of about .01% at 10 Khz.

In terms of DB down the second harmonic 100hz may be -113DB, at 1 Khz -100.2 DB, 10Khz -81.15 DB and at 20 Khz -76.75 DB. This with .25 Vrms in from input to input.

At 1 Vrms input to input the 2nd harmonic should be close to .2% and perhaps .5% at 20 Khz. This level provides about 1.79 Vrms on each output at 1Khz.

Distortion figures are now expected to be, -89 DB at 100hz, -76 DB at 1Khz, -57 DB at 10 Khz and -52.6 DB at 20 Khz. The third harmonic should still be down to around -96 DB at 20 Khz at the 1 Vrms input to input level.

I ran out of time to do more. Perhaps someone can build it and provide actual measurement data.

I did notice that the voltage rating of the of the output capacitors as mentioned on the circuit diagram is to low. They should be able to withstand the full supply voltage.

John Fassotte
Alaskan Audio

[Edited by alaskanaudio on 12-12-2001 at 10:07 AM]

[Bare]

Now please excuse if this sounds foolish.. I'm new here.
But isn't the best preamp.. NO preamp.
Ive run my system with and without a preamp for years now and can find no audible disadvantage at all..
is this not acceptable practice?

[Nelson Pass]

This circuit is essentially a cascoded version
of the SBOZ and will work somewhat better at the
cost of a bit more complexity.

A cautionary note about the zener diodes at the
input. My experience is that a good number of
sources will oscillate when presented with bare
zener protection diodes, and I suggest some
additional resistance at the input before them.

[Dave]

Mr Pass,

Thanks for the zener diode tip.

I based my design on the SBOZ and a few others which used a similar topology. I have seen this topology implemented with J-FETs and tubes as well as MOSFETs but never with cascode. So I decided to give it a try.

HooRide,

Here is another one you could consider building - http://www.geocities.com/d_broadhurst/sepre97.jpg This was e-mailed to me a couple of years back. I wouldn't know how to contact the designer. It is simpler but features constant current sources.
What about the Aleph P1.7 ?