So, this is my final plan. I added a simple mixer in the end so as to fit everything in one enclosure. Tape player has its own preamp so I'll just add it directly to the mixing op amp.
Ι am also thinking to add a 3 position switch before the mixing amp so as to choose which player plays. But if I just add a 3 position switch is the final op amp necessary? can I skip entirely the final mixing stage?
Ι am also thinking to add a 3 position switch before the mixing amp so as to choose which player plays. But if I just add a 3 position switch is the final op amp necessary? can I skip entirely the final mixing stage?
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The power supply voltage is too low. Of at least+/-15,and best of 18-20 volts and ramp NE5532 or OPA21604 . It is better to apply a passive correction
I asked about this and the answer was that even a +-3 volt is enough. Isn't that true? What will be the difference with lower voltage? As I said earlier in the post, shops are closed and I only have access to eshops and my stack. I don't have a NE5532.
So my schematic will work? if I change the lm353 with a rc4558?
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Tsili
Have You tried
REPLACEMENT ELECTRONICS COMPONENTS SPARE PARTS AUDIO VIDEO
I sometimes buy from them. Mostly faders for mixers & consoles.
Have You tried
REPLACEMENT ELECTRONICS COMPONENTS SPARE PARTS AUDIO VIDEO
I sometimes buy from them. Mostly faders for mixers & consoles.
First time seeing this shop. But I don't think that there is anything that I need from this shop for this project. Thanks for the recommendation though!
If you're going to accept a tape player input from the earphone jack (up to 7 vac), you need at least a +-8 v power supply. So 18 v wall transformer. If a line level jack (2 vac), then +-3 is okay. I don't understand the passion for+-15. My disco mixer sounds fine, better than my vacuum tube PAS2 since I put *****y polyester caps in the PAS2 to replace the off value paper ones.
You haven't biased the inputs to the middle of the power supply, the virtual ground. I think the + input of the mixer op amp goes to virtual ground through 22 k, same as feedback resistor. Or 11 k for a gain of 2. There was a bias to virtual ground version of the mjf RIAA schematic.
You need volume pots on each input, shunting after the 10k to virtual ground. My disco mixer used 40 k pots.
You can have many more 10k inputs to the mixer op amp. I have 5 on my disco mixer, which doesn't hum or hiss. So you don't need a 3 way switch. Just turn on the one input you are listening too, and turn off the other ones.
You can use 4558 for the 1 gain mixer op amp. Only the 50x gain RIAA op amps need to be low noise, like TL072 or better 5332 or 33078.
Oh, gee, you did the RIAA with LF353. I think that is first generation, really hissy. Look at the datasheet, the noise value probably is higher than TL072. Noise value of 33078/5332 is even better. Note different impedences noise specs are measured at make them apples and oranges numbers. If you use a socket for the op amp, you can try different ones to see which is the quietest. I spent 2 years purging hiss from my RA-88a, which came with 4558 op amps and pretty serious hiss and hum.
You haven't biased the inputs to the middle of the power supply, the virtual ground. I think the + input of the mixer op amp goes to virtual ground through 22 k, same as feedback resistor. Or 11 k for a gain of 2. There was a bias to virtual ground version of the mjf RIAA schematic.
You need volume pots on each input, shunting after the 10k to virtual ground. My disco mixer used 40 k pots.
You can have many more 10k inputs to the mixer op amp. I have 5 on my disco mixer, which doesn't hum or hiss. So you don't need a 3 way switch. Just turn on the one input you are listening too, and turn off the other ones.
You can use 4558 for the 1 gain mixer op amp. Only the 50x gain RIAA op amps need to be low noise, like TL072 or better 5332 or 33078.
Oh, gee, you did the RIAA with LF353. I think that is first generation, really hissy. Look at the datasheet, the noise value probably is higher than TL072. Noise value of 33078/5332 is even better. Note different impedences noise specs are measured at make them apples and oranges numbers. If you use a socket for the op amp, you can try different ones to see which is the quietest. I spent 2 years purging hiss from my RA-88a, which came with 4558 op amps and pretty serious hiss and hum.
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So If I bypass the mixer and replace it with just a 3 position switch. So that I only choose which input goes to the output will it be ok? (so for the tape and cd player that have their own preamps it will be just connecting the input to output).
I really appreciate your time and effort replying to my questions
I found walking around the table from the turntable, to the front of the PAS2 preamp to switch sources, annoying. Also changing the one volume pot for each different source. (LP & CD line level have no volume pot). The mixer I just leave everything on at once and the individual volume pots on the mixer mean everything is matched up most of the time unless the mastering engineer of the media used a different target level than the other CD's or LP's.
Note if you don't have volume pots, used mixers with a worn out master volume pot are a plague on ebay & online markets. As is really cheap. You can salvage all the other pots, almost all manufacturers use 10k pots. I got a PV8 mixer with bad master volume pot & a bad solder joint killing all the left channels for $30 +20 freight. The master volume pot was $2, the box of 2mm screws to attach it to the front panel was $5. $8 freight on each box from the vendor of course. (I buy other things to spread out the freight cost from distributors). Weren't OEM pot, it was shorter than the one Peavey used.
Note if you don't have volume pots, used mixers with a worn out master volume pot are a plague on ebay & online markets. As is really cheap. You can salvage all the other pots, almost all manufacturers use 10k pots. I got a PV8 mixer with bad master volume pot & a bad solder joint killing all the left channels for $30 +20 freight. The master volume pot was $2, the box of 2mm screws to attach it to the front panel was $5. $8 freight on each box from the vendor of course. (I buy other things to spread out the freight cost from distributors). Weren't OEM pot, it was shorter than the one Peavey used.
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Ι get it. This won't be a problem for me. I live in a really small house (18m^2 to be specific) so changing the switch won't really be a problem. So I'll built my schematic without the mixer. As I said earlier most eshops don't have stock transformers and I'll try to do the best with my stock.
Here’s a few photos of the RadioShack realistic stereo hi-fi preamplifier
Model 42-2101A
I bought this thing new. So that tells you how long I’ve had it and never used it. Lol
I had one of a different model number
Model 42-2101A
I bought this thing new. So that tells you how long I’ve had it and never used it. Lol
I had one of a different model number
If someone is interested, I could map out all the parts with the values of each part in for the resistors I could try to identifier the band colors for the values
There is an older round-shoulder model which was a complete piece of unpolished turd. Not enough power, not enough gain, and reject-grade transistors.
The later square-shoulder model 42-2101A et al was almost decent. I have heard much better, but good for the price. They adapted the too-small power with a doubler for a good 28V supply. Bottom barrel transistors had got MUCH better in the decades between the two series, the 2101 was less likely to hiss like a dirty steam radiator. The RIAA EQ is about as good as it gets with 10%/5% values.
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There is an extended discussion of the 2101 over there. Even perfboard layouts and SPICE runs.
Another factory scheme:
Realistic 42-2101 MM Phono Preamplifier Manual | HiFi Engine
Another factory scheme:
Realistic 42-2101 MM Phono Preamplifier Manual | HiFi Engine
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So I have built the preamp but the volume is too low. And it is lacking a lot of bass.
Any suggestions?
Any suggestions?