Internal pre-amp question

Boggsy44

Boggsy44

Active Member
So I bought a fairly inexpensive new turntable (no box) off someone on Facebook Marketplace.

The turntable comes in two models- one with pre-amp, one without.

It was listed as the model with a pre-amp (which I actually didn't want)... but it has a ground wire?

Dumb question: Does this mean it's actually the model WITHOUT the pre-amp? It plays through a Sonos Connect AMP with a lower volume- but not super low.

((** By the way, I'm purposely leaving out the brand of the turntable because I don't want this to devolve into a debate about whether the turntable is any good. I know it's not top of the line- but the reviews were good enough for the deal. It's not my every day turntable- and it was chosen for a specific purpose))
 
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Boggsy44 said:
So I bought a fairly inexpensive new turntable (no box) off someone on Facebook Marketplace.

The turntable comes in two models- one with pre-amp, one without.

It was listed as the model with a pre-amp (which I actually didn't want)... but it has a ground wire?

Dumb question: Does this mean it's actually the model WITHOUT the pre-amp? It plays through a Sonos Connect AMP with a lower volume- but not super low.

((** By the way, I'm purposely leaving out the brand of the turntable because I don't want this to devolve into a debate about whether the turntable is any good. I know it's not top of the line- but the reviews were good enough for the deal. It's not my every day turntable- and it was chosen for a specific purpose))
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If you ask me, no one should be ashamed of their audio gear... Money doesn't grow on trees, which is something some people just can't seem to understand.

Now, regarding your question - it is quite easy to tell whenever your table has a built-in preamp or not. Look for a bypass switch, which is either going to be located on the back, or under the platter. Depending on the brand/model of your table. It should read either "On/Off", or more likely Phono/Line. And please note that I'm not referring to a power switch, this one should be very small and out of sight. If you DO find one then your table has internal preamp, otherwise it doesn't. Having a ground wire connection doesn't necessarily mean anything in particular ... I've seen several USB tables with internal preamp which had either ground connection or terminals on the back. :)
Audio-Technica-Turntable.png
 
Trekkie4 said:
If you ask me, no one should be ashamed of their audio gear... Money doesn't grow on trees, which is something some people just can't seem to understand.

Now, regarding your question - it is quite easy to tell whenever your table has a built-in preamp or not. Look for a bypass switch, which is either going to be located on the back, or under the platter. Depending on the brand/model of your table. It should read either "On/Off", or more likely Phono/Line. And please note that I'm not referring to a power switch, this one should be very small and out of sight. If you DO find one then your table has internal preamp, otherwise it doesn't :)

Audio-Technica-Turntable.png
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I agree with the brand shaming! I actually have a really nice set-up as my everyday player but this is a side project.

That said- it probably just makes sense to say name the turntable. It's a Marantz TT-42. Now, even if it has an eternal pre-amp it would NOT have the option to shut it off (one of its odd quirks as a table). So there would be no switch on this particular TT. I've researched it quite a bit. I would actually prefer to find out it doesn't have a pre-amp... but the woman says it was the model that did. Then again- she had never actually used it.
 
Nothing terribly wrong with Marantz TT-42, I think it's a Dual in disguise.

If the music sounds "normal" to your ears, i.e. you have proper balance of bass and treble, the turntable likely has an internal preamp.
 
To be safe - if you are unsure - first plug the TT outputs into a high level input on your amp - ie: Aux or tuner.

If you hear sound at normal level - then the TT has a built-in amp.

If you hear bugger-all, then its a normal low-level output TT, and its most probably safe to plug the TT outputs into your phono amplifier input.
 
slimecity said:
To be safe - if you are unsure - first plug the TT outputs into a high level input on your amp - ie: Aux or tuner.

If you hear sound at normal level - then the TT has a built-in amp.

If you hear bugger-all, then its a normal low-level output TT, and its most probably safe to plug the TT outputs into your phono amplifier input.
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Was going to recommend the same thing. Alternatively, he could probe the cables with the multimeter between the headshell & RCA jacks. If they have direct contact & read "0.00" then it's a standard Phono output, without the internal preamp.

Edit
@Boggsy44, you could also disconnect the power, lower the tonearm down & spin the platter with your finger, while the turnable is connected into the "phono" input. If it's a genuine Phono output, you will hear the sound through the speakers. If it does have a preamp built in, there won't be any sound, because the internal preamp needs power to amplify the signal from the cart.
 
slimecity said:
To be safe - if you are unsure - first plug the TT outputs into a high level input on your amp - ie: Aux or tuner.

If you hear sound at normal level - then the TT has a built-in amp.

If you hear bugger-all, then its a normal low-level output TT, and its most probably safe to plug the TT outputs into your phono amplifier input.
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Ok- to throw another twist into it... I'm using a Sonos AMP. Its inputs in the back are just listed as "Analog Audio" IN. Again... it sounds ok... just a lot lower than the sound when I'm streaming audio from that same Sonos.
 
One more question... if the amp I'm connecting to doesn't have a spot for grounding... where do you all suggest I attach the ground wire. This is sitting n a console. Can I put a screw into the back of the cabinet and attach the ground to it> Sorry for all the questions.
 
Boggsy44 said:
One more question... if the amp I'm connecting to doesn't have a spot for grounding... where do you all suggest I attach the ground wire. This is sitting n a console. Can I put a screw into the back of the cabinet and attach the ground to it> Sorry for all the questions.
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I would recommend that you first determine IF you have the internal preamp or not. From what I understand, most tables with preamp built in are self-grounded & do not require external ground (unless you happen to notice loud & audible hum coming from the speakers). But whatever you do, do not connect the ground terminal with "earth" from the power outlet, or any other metal surface that's been electrically grounded through the 3-prong power plug.

Again, as I already explained in my previous post, you could disconnect the power, lower the tonearm down & spin the platter with your finger, while the turntable is connected into the phono input. If it doesn't have a preamp built in, you will hear the sound through the speakers. If it does have one, there probably won't be any sound, because the internal preamp needs power to amplify the signal from the cart.
 
Trekkie4 said:
I would recommend that you first determine IF you have the internal preamp or not. From what I understand, most tables with preamp built in are self-grounded & do not require external ground (unless you happen to notice loud & audible hum coming from the speakers). But whatever you do, do not connect the ground terminal with "earth" from the power outlet, or any other metal surface that's been electrically grounded through the 3-prong power plug.

Again, as I already explained in my previous post, you could disconnect the power, lower the tonearm down & spin the platter with your finger, while the turntable is connected into the phono input. If it doesn't have a preamp built in, you will hear the sound through the speakers. If it does have one, there probably won't be any sound, because the internal preamp needs power to amplify the signal from the cart.
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Ok I will try that with the needle. Thanks And just for clarification... where can I put the ground wire? Or just wait until I figure out the pre-amp riddle?
 
Boggsy44 said:
Ok I will try that with the needle. Thanks And just for clarification... where can I put the ground wire? Or just wait until I figure out the pre-amp riddle?
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If you're not getting any audible/annoying hum or buzz - its not something that I would personally worry about.....
 
slimecity said:
If you're not getting any audible/annoying hum or buzz - its not something that I would personally worry about.....
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Exactly. If you have excess noise try under a screw on the amplifier cabinet and it might help. If you don't, don't worry about it.
 
Montycat said:
Exactly. If you have excess noise try under a screw on the amplifier cabinet and it might help. If you don't, don't worry about it.
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Yes, BUT... I happen to know at least one brand (Marantz) which uses 3-prong power plugs for their equipment. Meaning that the bottom plate (and therefore the entire metal cabinet) will be grounded to earth. So, by grounding his table into the cabinet will essentially ground the table into earth (or in some cases neutral, IF neutral & earth are bridged together at some point)
 
So it does have the pre-amp. It says so under the TT. And it sounds perfectly fine now. Just a little lower than the streaming. I guess that’s just a TT being a TT?
 
Boggsy44 said:
So it does have the pre-amp. It says so under the TT. And it sounds perfectly fine now. Just a little lower than the streaming. I guess that’s just a TT being a TT?
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You would know if it didn't have a pre-amp - it would be a lot quieter (about 40dB too quiet, which is a lot) and would would sound extremely tinny due to the lack of RIAA equalisation. Your's definitely has a pre-amp.

Yes, turntables often sound a bit quieter than other sources, but that's normal.
 
Trekkie4 said:
Right, that's what I told OP. If I'm not mistaking, Audio Technica AT-PL120 had the preamp bypass switch under the platter, among many others.
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Not this one. No switch. No option to shut off. It’s an oddly make (cheap to the touch) Marantz table. Very odd. I’d never pay retail for it.

It just worked perfect because of how it fit in the console, it’s all auto - which was good for the console- and it was a deal. Plus it sounds pretty decent.
 
Boggsy44 said:
Not this one. No switch. No option to shut off. It’s an oddly make (cheap to the touch) Marantz table. Very odd. I’d never pay retail for it.

It just worked perfect because of how it fit in the console, it’s all auto - which was good for the console- and it was a deal. Plus it sounds pretty decent.
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Well, all things considered you can always yank the preamp out & bypass the RCA jacks to the tonearm wires if needed. But in my opinion it looks like a decent table. As someone already pointed out, it's a "Dual" in disguise.
 
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