How do I make an amplifier for an old turntable?

[guidoilieff]

I have this "turntable":



Here is the inside view http://electronica.yoreparo.com/electronica_antigua/conexion-cables-a-plaqueta-winco-3050e-t763076.html


I was wondering if I could use a simple IC amplifier to make it work... I tried connecting the pick up to a pc speaker but didn't work so I was wondering if it needs some kind of filtering or something like that.

Thanks


(Do I need this? http://phonoclone.com/diy-pho5.html )

[guidoilieff]

I want the germanium transistors for a fuzz face (ac127/28)

[Brisance]

how about buy one of the cheap behringer preamps and put it in there?

[GibsonGM]

You could just get an amp, like Brisance suggests, or make one.   

You could make a small preamplifier from one (or more) transistors to bring the signal up a little, and then feed it to an LM-386 type amplifier to your speaker.  This would allow you to hear the output, but not very loud - nothing like a store-bought unit would sound like! But it would work.

Last, you could make a preamplifier and feed the output to a REAL stereo system amplifier, just as you would a tuner. 

So it depends what you want to do with the turn table...just a quirky project, or is this something you want to use for real?

[davent]

Built one of these phono pre's years ago. Cheap, simple and very decent sound.

http://phonoclone.com/diy-pho5.html

[R.G.]

The literature from about 1960 to 1990 is full of DIY phono preamps. One of the best I ever heard was with the National Semi LM381. Another of the best I ever heard was the Dynaco PAS preamp with 12AX7s.

Google ought to turn up huge numbers of DIY phono preamps.

[Mark Hammer]

Thanks for reminding me.  You know, I should probabaly get around to making something with the LM381AN I have in my parts drawer since 198-mumble.

[guidoilieff]

So.... the coil in the needle of the turntable is like a piezo but with a coil? It doesnt need anything in particular?


Im going to use the output, not the speaker, to connect it to some nice pc speakers that have their own amp.

[PRR]

This is a CERAMIC (piezo) pickup.

Not the magnetic pickup used in most high-quality record players.

You do NOT want a Berenger preamp, or a LM381.

You want a HIGH impedance input, no filtering or EQ.

Frankly, wiring the pickup right to a guitar-amp should work pretty-good. (It will tend to make anything sound like electric guitar.)

What is wrong with the amp as-is? It's not the crappiest design around. Maybe leaky electrolytic caps, easy to fix.

[guidoilieff]

This is a CERAMIC (piezo) pickup.

Not the magnetic pickup used in most high-quality record players.

You do NOT want a Berenger preamp, or a LM381.

You want a HIGH impedance input, no filtering or EQ.

Frankly, wiring the pickup right to a guitar-amp should work pretty-good. (It will tend to make anything sound like electric guitar.)

What is wrong with the amp as-is? It's not the crappiest design around. Maybe leaky electrolytic caps, easy to fix.

Oh yeah, the caps leaked everything, Im replacing em now. The thing is that I never use that turntable and was wondering if i could use that amp to make a guitar amp or use it like a pre. Give it some use... Im a bassist btw...

I repaired the "needle" hook up and the wires and tried it with a 386 connected to the pc speakers. Sounds tinny but it works... I don't know if its the cartridge or the amp.

[Digger1770]

The thing is that I never use that turntable and was wondering if i could use that amp to make a guitar amp or use it like a pre. Give it some use... Im a bassist btw...

Could you add a jack and switch on the input and use the amp for phono or guitar...? maybe increase c2 and c4 for bass use?
Good luck

[bool]

"Son, I'll let you in on a secret":

Just take almost ANY of the "guitar buffers" - preferrably the ones with the higher impedance input, and connect it between the cartrigde and the power-amp.

These cartridges aren't all that much different to the present-day "piezo" pickups.

These cartridges have a reasonably high output, certainly much higher than any magnetic ones, and - for example - a TL071 buffer will usually drive any chip-amp to a reasonably high level.

So this should be a good starting point for your further tinkering.

[PRR]

> tried it with a 386 .... Sounds tinny but it works... I don't know if its the cartridge or the amp.

The ceramic (piezo) needle has an impedance versus frequency like:

100Hz - 1meg
1KHz - 100K
10KHz - 10K

The '386 input is roughly 50K.

Do the voltage-divider math, you see that 10KHz is slightly down, 1KHz is significantly down, and 100Hz is WAY down. Bass is like 1/20th of what it should be. Pretty tinny.


> I have this "turntable":... I was wondering if I could use a simple IC amplifier to make it work...
> I never use that turntable and was wondering if i could use that amp to make a guitar amp

I'm confused. Do you want the TT to work? Or do you want an instrument amp instead of a TT that you "never use"?

As a Record Player... it had low aspirations. The 500K input suggests it only aimed for 200hz bass response. That would be very appropriate for a 4-inch speaker. We had millions of 200Hz radios and recordplayers back in the day. And if you truly still love records, you can find a better player.

As an instrument amp, it is "maybe". Input impedance is fine but gain is very low for instrument use. I think you need about a 10X booster in front. Power output is over 2 Watts, quite high for the market, but pretty low by guitar-amp standards. Distortion will be high but not in a "good" way. Chips offer much better solutions.

[guidoilieff]

The thing is that I never use that turntable and was wondering if i could use that amp to make a guitar amp or use it like a pre. Give it some use... Im a bassist btw...

Could you add a jack and switch on the input and use the amp for phono or guitar...? maybe increase c2 and c4 for bass use?
Good luck

I tried it with some pc speakers and seems to sound ok with bass. There is no need for increasing the caps. The only thing that weird me out now is its 11v output because its meant to be connected to a speaker directly. I'm afraid to connect it to the bass amp.

Is there a way to get rid of those 10v?


That schematic is not the right one, it seemed similar to me, but its pretty close I guess.

[guidoilieff]

> tried it with a 386 .... Sounds tinny but it works... I don't know if its the cartridge or the amp.

The ceramic (piezo) needle has an impedance versus frequency like:

100Hz - 1meg
1KHz - 100K
10KHz - 10K

The '386 input is roughly 50K.

Do the voltage-divider math, you see that 10KHz is slightly down, 1KHz is significantly down, and 100Hz is WAY down. Bass is like 1/20th of what it should be. Pretty tinny.


> I have this "turntable":... I was wondering if I could use a simple IC amplifier to make it work...
> I never use that turntable and was wondering if i could use that amp to make a guitar amp

I'm confused. Do you want the TT to work? Or do you want an instrument amp instead of a TT that you "never use"?

As a Record Player... it had low aspirations. The 500K input suggests it only aimed for 200hz bass response. That would be very appropriate for a 4-inch speaker. We had millions of 200Hz radios and recordplayers back in the day. And if you truly still love records, you can find a better player.

As an instrument amp, it is "maybe". Input impedance is fine but gain is very low for instrument use. I think you need about a 10X booster in front. Power output is over 2 Watts, quite high for the market, but pretty low by guitar-amp standards. Distortion will be high but not in a "good" way. Chips offer much better solutions.

I wanted to make a simple IC amp for the TT and use the original amp circuit of the TT as a pre or amp. It seems its not going to work like that.

I'm sorry but that is not the right schematic. The one I need doesn't exist.   I tried it with bass and sounds fine, it could have more bass but I was surprised. Now i want it to connect it to a bass combo but the output of the TT amp is 10v.

Could it work if I connect it to a TDA2040 circuit?


I'm sorry but I don't know whats the theory of voltage-divider math is, I'll read about it.

[guidoilieff]

[Brisance]

I don't think they are germanium to be honest, TO92 whispers Si to me...

[guidoilieff]

I don't think they are germanium to be honest, TO92 whispers Si to me...

The ones in the heatsink are. The others are silicon 3391 http://pdf.datasheetcatalog.net/datasheets/37/74021_DS.pdf

[Mark Hammer]

Forty odd years ago, I had a turntable with a decent Philips crystal cartridge.  Of course, my standards for "decent" were different back then, but it was still a cut above, as far as crystal cartridges went.

I had it on my desk, and had my guitar amp on the other side of the room.  I had a cable plugged into the amp, but could not reach the turntable leads with my outstretched hand, and pulling on the amp cable so that it was like a tightrope in the air.  I asked my dad to help me by handing me the turntable leads.  In one of those actions-slips that many of us commit daily, he picked up the leads, and "handed" me his unoccupied hand instead of the one with the turntable leads.

Much to our mutual surprise, the turntable signal (there was a disc playing at the time) came through loud and clear.  In fact, even louder than when I eventually connected the turntable leads to the guitar-amp cable.  Keep in mind he was holding the RCA phono plugs in his bare hand on one side, and holding my bare hand on the other.  We called my sister in, and she was inserted into the human chain between my dad and I, and the signal got even louder.

To this day, I still don't know what the hell was going on.  But one thing remains clear: you need to dig up my dad from the grave and have him hold the turntable leads and your bare hand.

Seriously, though, crystal cartridges have a tendency to be a little strident.  Partly because of their own characteristics, but mostly because these days they tend to be processed through amplifier inputs that do not EQ in a manner to complement the treble pre-emphasis on vinyl.  I doubt that a pure RIAA-curve in a mag preamp would yield flat response though, since, like I say, crystal cartridges tend to impose a bit of their own tonality on things.  However, as others here have noted, the key thing is to start with a high input-impedance input stage, JFET or similar.

[guidoilieff]

I like this amp design. I just don't want to burn my bass combo amp. The output is 10v DC. Wouldn't that fry something?