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need more gain...what would you do?

Dan ʕ•ᴥ•ʔ

Dan ʕ•ᴥ•ʔ

Peanut Head
I have a Music Hall turntable which has a decent phono preamp built into it. Now the preamp only has 150mV of output, but it can be bypassed to go direct from the cartridge. I'm assembling a passive line stage level control and switch box for it, my CDP, tuner, etc. As I see it, I have two ways to go, I can either get a different phono preamp with the needed 1.5 to 2.0 volts of output, or I can simply build a small gain stage to go between the turntable's preamp and the switchbox to get the extra gain I need.
I'm on the fence on which way to go with this. What would you do?
 
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Bob_in_OKC said:
If the turntable's built-in phono preamp can be disabled, I'd vote for a quality DIY phono preamp from turntable to line stage. Sounds more direct to me.
Click to expand...

I can vouch for the excellent performance of the Hagerman Bugle. It's a simple matter to fine-tune gain by selecting resistor value.

Another option might be using a cartridge with higher output.
 
I think the gain varies, although the specs say 40dB. What is the output of your cartridge? It seems like 40dB should bring a typical 5mV cartridge up to a level similar to other line level sources...250mV to 300mV or thereabout...right? I don't understand the need for 1.5 to 2.0 volts, though. That part is over my head. :)
 
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Celt said:
Unless I'm missing seeing it, Hagerman doesn't disclose the actual output level in voltage. I'm needing at least 1.5 to 2.0 volts.
Click to expand...

Of course the output will vary with the music, Duh Grainger. But the confusing thing is that there are a few standards of measuring output of a cartridge. So you get varying results.

Bob_in_OKC said:
I think the gain varies, although the specs say 40dB. What is the output of your cartridge? It seems like 40dB should bring a typical 5mV cartridge up to a level similar to other line level sources...250mV to 300mV or thereabout...right? I don't understand the need for 1.5 to 2.0 volts, though. That part is over my head.
Click to expand...

Bob is on top of it. Compare the gain of the built in preamp to the Cornet's 40 dB.
 
40 dB of voltage gain will give you 100X more. A cart with an output of 3.5 mV will yield ~ 350 mV out of a 40 dB preamp if you discount any losses from connectors, cables, etc.

This table shows Vin as the voltage ouput of your cartridge (in millivolts), Vout as the desired output of your preamp, and 20*log as the gain required of the preamp to get the desired output.

With a nominal 3.5 mV out of your cart, you will need a preamp with 52.56 dB of gain to get 1.5 Volts out.

These are ideal numbers. Reality will cause these numbers to vary.

V in V out Vo/Vi 20*Log(Vo/Vi)
2 350. 175. 44.86
2 700. 350. 50.88
2 1000 500. 53.98
2 1200 600. 55.56
2 1500 750. 57.50
2 1800 900. 59.08
2 2000 1000 60.00


3.5 350 100 40.00
3.5 700 200.0 46.02
3.5 1000 285.7 49.12
3.5 1200 342.9 50.70
3.5 1500 428.6 52.64
3.5 1800 514.3 54.22
3.5 2000 571.4 55.14


5 350.0 70 36.90
5 700.0 140 42.92
5 1000 200 46.02
5 1200 240 47.60
5 1500 300 49.54
5 1800 360 51.13
5 2000 400 52.04
 
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I can vouch the Rod Elliott ESP-06 phono stage can output thru a passive into a power amp and it's gain can be boosted for a low-ish output cart (but not a lo-output MC).
 
I have two carts. The Audio Technica is 4.0mV and the Ortophon is 5.0mV.
Yeah, I'm trying to achieve a typical line level voltage, which is between 1.5 to 2.2 volts.
I can either build a gain-stage to goose the existing phono pre to the level I want...OR...
build or buy a phono preamp with the needed gain. With one exception, all I've looked at were down around 150mV to 300mV, which isn't enough for my needs. :no: The Music Hall TT has a built-in preamp, and it's response isn't exactly flat. It's +1dB @ 20Hz and -3dB @ 20kHz, that may be enough reason to get a different preamp and be *ready to roll* if I later decide to get a different turntable.
 
Oikily-doikily...gonna give this preamp a try. It has 1.4 volts of output, impressive wide and flat response, excellent s/n ratio and switchable capacitance. Appears to be well made and is very affordable.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=245-876

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It's not just gain. You have to apply the RIAA curve at some point. That's why the manufactured phono preamps are so useful, because they have everything you need ready to go.

There are lots of choices. Obviously, the $49 one will not sound as good as the $5000 one, but they make them for all tastes and budgets.
 
If GAIN is your main objective, check out the 2800-PC mixer from DAK at:

http://www.dak.com/Reviews/2020Story.cfm#in

It has RIAA corrections, phono preamp with 50+ dB of gain, gain control, LED VU meters to indicate clipping, etc. The "package" is $69.99, but they may offer the mixer alone.

I use it for digitizing LPs when I want to get more signal to the PC.
 
vinyl1 said:
It's not just gain. You have to apply the RIAA curve at some point. That's why the manufactured phono preamps are so useful, because they have everything you need ready to go.

There are lots of choices. Obviously, the $49 one will not sound as good as the $5000 one, but they make them for all tastes and budgets.
Click to expand...

Have already addressed all of that. The ART's gonna get me there as much as one that costs four times what it does.
Regardless, there's no way I'm gonna spend 5k on one.
 
For those few who may be interested...
The first preamp showed up defective with a bad voltage regulator.
One phone call to Parts Express got a replacement sent out via Fed Ex at no additional charge.
The new one sounds great and for anyone who'd like a peek under the hood...

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I've have one!! Used it for the last couple of years too till I tried this Cambridge!!

Actually, it was my Maggies and the Systemdek that made me want to change this little gem out!!! The Maggies make you want to address small faults in your system!! And that ART just wasn't as "big" sounding as the Cambridge is...otherwise the ART and I were perfectly happy with the Technics tables I have had and every other component that rotated through!!

Very nice little $50 unit that sounds better than the money you paid for it!!

Cheers!!!

:music:
 
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I modified the preamp the other night. I have several mono 45's and albums and as we all know, switching the signal from stereo to mono signifigantly lowers the noise floor. So, I added a stereo/mono toggle switch to the front panel, making a good phono-pre even better!
(Note: I turned the gain up so the led would show in the pic.)

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