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jFET phono preamp - boozhoundlabs
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Author:  mwhouston [ 26 Jan 2011, 15:47 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Some times with small devices these big brass cones look a little out-of-place. But I think in this case they will stay. I quoted the customer a price but at the time I was not planing on using the Hammond case - $43 and the cones -$20. I'm hoping when he sees the final product and has a listen he'll think the extra bucks will be worth it.

Today I'll get the proper caps for mine and so when I'm finished this second one I can correct my own. The wrong caps does explain the brightness in the upper mid and if it corrects that this should be a very good preamp. It actually sounds excellent now (if not a little forward) so things should only get better.

Cheap-jack thanks for all your comments and suggestions so far. Interestingly if I had not built this second unit I may never have found the problem with the first.

Author:  mwhouston [ 27 Jan 2011, 09:28 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Just finished and had a quick listen to Mongrel Dog Audio Pacific phono preamp (number two). Though a brief listen (1:30am here) all sounded very good and well balanced. Added some bitumen and Al foil to the Hammond enclosure to give some weight and deadness.

Cheap-jack: the brass cone feet stayed, happy so far. May get a big listen tomorrow.

Author:  cheap-Jack [ 27 Jan 2011, 15:32 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

mwhouston wrote:
Added some bitumen


With the 3-in-a-set brass tip-toes, I don't think you need to add any bitumen. What I worry is overdamming. Too much weight on the box can deaden the box resonance as well as the music itself !

mwhouston wrote:
Al foil to the Hammond enclosure

Why you want to add al foil when the box is already metallic? I add aluminum foil to line up 100% the internal surfaces of a non-metal box against EMI/RFI only.


Author:  mwhouston [ 27 Jan 2011, 15:53 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

The bitumen and Al foil are one. I didn't make that clear. Also I don't think you can over-damp or over screen an enclosure. I often add metal layers to metal cases.

The preamp sound good so far. I hope to get a better listen in the next few days. Also I will soon receive the genuine boozhoundlabs kit complete with PCB and Russian PIO caps. A comparison should prove interesting.

Author:  mwhouston [ 30 Jan 2011, 05:20 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

If you have been following this thread you will know that the orginal preamp built had some resonance problems. These were fixed with re-placing the incorrect caps with the right ones. This is where 0.034uf was required. What I found was the whole phono preamp even sounded better with that cap value changed to 0.0364. This I almost stumbled on by accident.

So I guess what I am saying is the original boozhoundlabs Le Pacific may sounds better with the 0.034 cap replaced with a value of 0.0364. You would be amazed how this very small change in an already small value of capacitance makes such a noticable difference in the overall sound but it does. The preamp now sound very sweet but has not lost its very clear mid range.

Author:  mwhouston [ 02 Feb 2011, 15:32 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Just finished assembly of the BHL Le Pacific kit. Very small pads on the PCB and a little hard to work with. But most of the brd. is copper plate so there should be very good shielding. It only takes an hour to complete the cct. brd. Today I will get an enclosure for the cct.brd. I am going to build this a la Sutherland.

Author:  mwhouston [ 07 Feb 2011, 17:52 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

I have just completed and are now listening to the genuine BHL Le Pacific phono preamp using Russian PIO caps and PCB. Because Gio has asked me to present this build and my findings of how it compares with the two I made from different part types I will not go into detail here. Nor will I display any photos of the finsihed unit. You'll have to wait. This may give you a clue

But I will say that it does not display the slight upper-mid resonance my other two builds have (the first build more so than the second). So when you think that all three builds use the same schematic and parts values (apart from one very small cap value) it shows that not all components sound the same. One type of cap will sound different to another type of cap with the same value and rating. This journey down Le Pacific phono preamp road has highlighted this fact. We all knew it but now I have auditory proof. Or am I just hearing the sonic signature of a PCB?

Author:  Gio [ 09 Feb 2011, 13:28 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Hi Mark, I would expect the PIO to impart their own sonic signature. The small cap you added is in the RIAA equalization circuit so that may have to do with the response.

With the boozhoundlabs kit do the FETs come matched?


Author:  mwhouston [ 09 Feb 2011, 15:39 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Good point. I assumed they do because you only get four. Hard to build it with others. I can check the voltages at the drain and see how they compare. I'm about to start the write-up.

Author:  Ernst [ 09 May 2011, 06:37 ]
Post subject:  Re: jFET phono preamp - boozhoundlabs

Hi Mark,
I see that you are using the Boozhoundlab phono preamp and that you are quite impressed by the preamp. I s this the unit as ordered from e-bay or did you do some modifications to the circuit. I want to add a phono stage to the ForeWatt preamplifier and the Boozhoundlab phono preamp looks as if it could the job. Regards, Ernst

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