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Somewhere in March 2004 I tested the PhonoCard for the first time. I used LT1115 for the input amps and LT1037 for the second stage. Remember I did receive a battery power supply from Sodejuu which will enable me to run the amp on batteries once finished, but today I tested the amp on the Power Supply of the PhonoClone.
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So no batteries, no blue LEDs and no fancy box for the amp. First impression was "OK it works" but the setup did not allow switching back and forth with other amps so I had no direct comparison. But someting got my attention right away: This amp has more gain than the phonoclone and even less noise. Very, very promising isn't it? Of course I tested the amp with the frequency generator, as all wires inside cartridges are very delicate and you don't want to fry it. So I tested it at least twice, measuring the current on the input, and found it to be 0.02 mA which I thought was acceptable. After all, I have (I think) a faily expensive cartridge so switching the amp on for the first time with that cartridge connected is an interesting moment. All you can do at that moment is wait, the show can be over within a split second. But all went well, and the sound came to live after 15 minutes. I decided to give it a burn-in in our living room setup. In a direct comparison with the CD player (after setting the gain equal on the cd player) I cannot conclude other than that this amp is really fast. |
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In the picture on the right the test setup is shown. The photo is a close up of just the amp section shown in the picture above. I noticed how quiet the amp was even with all circuits exposed in open air, and making use of 4Play interlinks without shielding. Ahum, well, ... a day later I heard a German radio station while listening to music. I found out that I needed a ground connection for the turntable. |
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It's a few weeks after the initial listening setup, and the amp is finished. Only the battery circuit, on/off switch and some LEDs need some work once the final aluminum boxes have arrived.
Also, I'm planning to check the RIAA network at a later date and if necessary do some minor adjustments. To my ears, everything works as designed, but it never hurts to check the filters after a few weeks operation and compare them to the calculations and SPICE models.
Meanwhile, I'm listening for more than two weeks to a very nice phono amp. It's very fast and has good bass.
There are quite some questions left, for which I'll probably find an answer later:
As usual it took me far more time than expected before the amp was finished. Or better, it took a while before I found the time to built the powersupply.
But it was worth waiting for. The picture below shows the two boxes: The left contains a power supply with charging circuit which is connected by an umbillical cord to the amp. Batteries are in the amp so it is possible to run disconnected from the power supply for a while.
The resistor values used in the amp are such that I expect more than the bare minimum for power consumption. Therefore the amp can be switched on and off, although it is expected that the amp will stay on and the power supply/charger will charge the batteries permanently.
OK, of-course we decided to have a serious listening session for the new amp. Initially the setup was a follows:
So what did we listen to:
As I modified the GeenKloon just a week before, this was the perfect opportunity to test the total setup of gainclone and phonoclone. So music played all weekend, which means that we listened to music and not so much to individal components.
Not that I do not like to listen more "technically" to a specific setup, sitting in the ideal listening position on the Sofa and trying to discover the "best" setup of an amp or other component. But for me it works equally best to do other things while the music plays, and then sometimes you suddenly hear things that you could swear you did not hear before.
At such a moment I will start running for the Sofa and probably will replay that specific part of music again (at increased volume levels ;-)
Sounds familiar?
I must say that after listening to Phonocard for while I'm convinced of it's qualities. The inverted setup (current amplifier) is a very fast solution. With just a bare minimum of components and no fat this amp can really move. The combination with the Geenkloon is a very good one too.
Gives me Faith ...
Music of George Michael, but also classical music are a good match for the Phonocard/Geenkloon combination. While playing Eva Cassidy I was not sure about the hi frequencies and Sssss sounds, but these appear on CD and other pre-amp/amp combinations as well. The combination is very revealing and some of Eva's recordings are not top quality. Hmmm, we'll see.
After finishing this project I think the next logical step will be using transisssssstors or so, but we'll see. After all, some projects last longer than expected.
On the other hand, there may not be many people having so many phono preamps in house as I have. Maybe it's time to look for another challenge... (not)
The following article I found when scanning diyaudio.com the other day
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