Flat Phono Preamp and Inexpensive: Mutually Exclusive?

[Wigwam Jones]

How about a pre with a tape head (NAB) input? That would be flat I presume and could be loaded to get things just right. I've owned a few of them over the years. Dyna PAS3 maybe do it?

Is NAB flat? I didn't know that. I agree that a PAS would be nice, or even a PAT, but probably out of my budget for now. Looking for something cheaper, although I agree, those are sweet. Kegger brought one over to my house for a SMAC party and it was amazing.

 

[Wigwam Jones]

I have two suggestions. The first is the Tracertek CTP-1000. This is what I use. It does a good job, it's certainly good enough for 78s. It's all analog.

Another one to check is the Parasound Z-Phono USB. It has both analog and USB outs. The flat EQ is only through the USB port. I'm really thinking about getting this. I've seen some excellent reviews, then I've seen some from those who are disappointed and complain the power supply is noisy.

I saw the Tracertek in my Googling, and although it's about twice as much as I want to spend, it might be a compromise I am willing to make if I don't find anything else. I will look into the Parasound, thanks.

 

[Wigwam Jones]

Wigwam:

Just about any audio grade Op Amp will do it for you. A flat gain amp can be made with 2 resistors, an op amp and a power supply. Input impedance is set by another resistor and, if needed, a parallel capacitor. I'm not home right now so I cannot post a quick schematic but you would probably want about 40 to 50 dB of gain.

Here is a link that has the general schematics on it. The one you would want to use is on the right, non - inverting.

http://www.elexp.com/t_gain.htm

To add the termination resistor it would run from the + input to ground. Any input capacitance you would want to add would be in parallel to the the resistor. In the diagram if R1 = 180K and R2 = 1K would would get 45 dB of flat gain. You would want to use the highest voltages that the Op Amp is comfortable with, typically +/- 12 to 15 volts.

Hope this helps you.

Shelly_D

It does help me, thank you. I am about two steps behind that capability in my abilities with things electronic, but if I could see a schematic rather than a block diagram, maybe I could do it. I will look for just such an item, thank you!

 

[shelly_d]

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[shelly_d]

It does help me, thank you. I am about two steps behind that capability in my abilities with things electronic, but if I could see a schematic rather than a block diagram, maybe I could do it. I will look for just such an item, thank you!

First pass:

A 24V CT transformer will give you about +/- 15 volts. Going to a 30 volt CT will allow you to use regulators for a +/- 12 volt regulated supply. The filter cap values are a first approximation for value. The 220pF caps are optional and their value should be based upon the value of capacitive loading your cartridge wants to see. the output caps (C3 and C4) are in the signal path. They are there to block any DC offset coming off the Op Amp. Use the largest value film cap you can find. Working voltage for those should exceed the DC value of the power supply, that is if you are using +/- 12 V then the cap needs to be rated for 24 volts or more.

Shelly_D

 

[Wigwam Jones]

Wow, thank you! That's amazing!

 

[dumptruck]

Note that's additional loading capacitance for the cart after the tonearm wiring and phono cables.

 

[shelly_d]

Wow, thank you! That's amazing!

Actually not. It is about the simpliest Op Amp circuit there is. But thinks for the kind words. I'm not so modest that I don't like hearing them.

Shelly_D

 

[fiddlefye]

Is NAB flat? I didn't know that. I agree that a PAS would be nice, or even a PAT, but probably out of my budget for now. Looking for something cheaper, although I agree, those are sweet. Kegger brought one over to my house for a SMAC party and it was amazing.

I cannot guarantee that NAB is flat, but I suspect so. I don't think what comes off a tape head has a curve thrown at it, does it? Someone with more expertise than I would know for sure. I can tell you it sure isn't RIAA as I plugged into it once to find out and the results were not good.

 

[tblob]

NAB is not flat. It is NAB. Tape, as a storage medium, is not flat and must be forced into general flat record/playback with with bias and response curves.