Hi to everyone! I am new to this forum and hoping that this is the right place to ask this question. I am working on a high quality portable record player construction. Based on a Philips portable low quality Stereo record player from the 70s, I am planning to construct a player with a Lenco arm, and a higher quality MM cartridge. Housing will be an old busyness suitcase. I am going to buy some more expensive records, on record fairs I can control 7" & 12" records for noise with that set. So all I need now to complete the assy is a simple good amp with RIAA specifications and pre-amp job. Problem: It has to work on 9 Volt DC! NO SMD technology please! Many thanks in advance!
the schematic in post 5 of Improving a "Disco mixer" to mid-fi performance - diyAudio
is about the simplist available. works with 33078 or NJM2068 op amps. As delivered it had 4558 op amps but was hissy.
If you have only one 9v wall transformer you can split it to +- 4v with the circuit shown in post 4. I split +18 transformer to +-8 v so I'd have headroom to mix in a 5 vac radio earphone signal.
You need a second op amp to drive the 2 m cable to the amp, I believe a gain 10 example is shown in post 4. If the power (speaker) amp is in the chassis you can use the second op amp to drive emitter followers for a 10 w amp from a 30 v wall transformer. See post 48 of this thread DIY Amp Design Critique - Page 5 - diyAudio
is about the simplist available. works with 33078 or NJM2068 op amps. As delivered it had 4558 op amps but was hissy.
If you have only one 9v wall transformer you can split it to +- 4v with the circuit shown in post 4. I split +18 transformer to +-8 v so I'd have headroom to mix in a 5 vac radio earphone signal.
You need a second op amp to drive the 2 m cable to the amp, I believe a gain 10 example is shown in post 4. If the power (speaker) amp is in the chassis you can use the second op amp to drive emitter followers for a 10 w amp from a 30 v wall transformer. See post 48 of this thread DIY Amp Design Critique - Page 5 - diyAudio
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I grew up with 12V-power phono preamps, and I think that's a poor choice; 9V is poorer.
At the usual gains of RIAA preamps, so they make good level in your volume pot and line amp (50-100@1KHz), loud parts of loud records can exceed 3Vrms, 8.5V peak to peak. Yes, in theory 9V covers it. But it is exacting design.
Is there (going to be) a Power Amp in this suitcase? It will surely have higher voltage power.
At the usual gains of RIAA preamps, so they make good level in your volume pot and line amp (50-100@1KHz), loud parts of loud records can exceed 3Vrms, 8.5V peak to peak. Yes, in theory 9V covers it. But it is exacting design.
Is there (going to be) a Power Amp in this suitcase? It will surely have higher voltage power.
Many thanks for your replies!
I try to build it as a low budget project.
There is no reason to invest in an expensive cartridge, I have
some good stuff at home from parted out record players.
A Shure M 75, an Excel ES 70E or an Ortofon Om 10 will be
good enough to test records for their condition.
@ Craigtone: If I cannot find a simpler version I take your advice.
Anyway they are good to use inside a DJ table I am constructing.
Thanx!
@ gigigirl: Please add more informations (schematic?) about the Jan Ditten
simple switcher. Thanx in advance.
In the past I was dealing with a Penny record player, just to check unknown 7" records.
But now I have to clean my "most wanted list" and have to pay more
than about 50 Cent to 2 US$ (converted).
On weekends, I love to travel across Germany to visit other flea markets for hunting records.
I was very successful in the past with that.
But in between I realize that I have to pay for some records the official market prize,
or have to swap good stuff I don`t need.
Ebay and discogs is out of race after making my experiences.
So when I am travelling, maybe visiting a record fair I need a light-weight
suitcase player, but not that crap which was sold battery powered to
the youth in the past.
I want to use a good arm which allows me a simple AS construction use.
Just that what I took once from the curbside!
Not solved until now is the leveling of the player inside the suitcase.
I will never have a clean table to test records, so I have to deal with that
situation.
Anyway, I try to save weight wherever it is possible.
Best regards!
I try to build it as a low budget project.
There is no reason to invest in an expensive cartridge, I have
some good stuff at home from parted out record players.
A Shure M 75, an Excel ES 70E or an Ortofon Om 10 will be
good enough to test records for their condition.
@ Craigtone: If I cannot find a simpler version I take your advice.
Anyway they are good to use inside a DJ table I am constructing.
Thanx!
@ gigigirl: Please add more informations (schematic?) about the Jan Ditten
simple switcher. Thanx in advance.
In the past I was dealing with a Penny record player, just to check unknown 7" records.
But now I have to clean my "most wanted list" and have to pay more
than about 50 Cent to 2 US$ (converted).
On weekends, I love to travel across Germany to visit other flea markets for hunting records.
I was very successful in the past with that.
But in between I realize that I have to pay for some records the official market prize,
or have to swap good stuff I don`t need.
Ebay and discogs is out of race after making my experiences.
So when I am travelling, maybe visiting a record fair I need a light-weight
suitcase player, but not that crap which was sold battery powered to
the youth in the past.
I want to use a good arm which allows me a simple AS construction use.
Just that what I took once from the curbside!
Not solved until now is the leveling of the player inside the suitcase.
I will never have a clean table to test records, so I have to deal with that
situation.
Anyway, I try to save weight wherever it is possible.
Best regards!
The OPA2134 in the bugle uses 5 ma per amp, or 10 ma per package.
The 33078 use 5 ma per package, 2 ma.
The bugle uses 3 ICs for two channels, the RA-88a uses 2.
One eliminates the radio signals in the amp by putting 33 pf across the rca jacks and building in a Steel package. Also putting an inductor in series with any power coming in from outside.
The 33078 use 5 ma per package, 2 ma.
The bugle uses 3 ICs for two channels, the RA-88a uses 2.
One eliminates the radio signals in the amp by putting 33 pf across the rca jacks and building in a Steel package. Also putting an inductor in series with any power coming in from outside.
> Realistic Battery Operated Stereo Preamp
Shudder.....
Actually, this is NOT the older model made with rejects from the pocket radio factory. That's actually a pretty spiffy transistor.
The "specs".... ah, whoever typed the data didn't know specs. Same person did the schematic values?
R5 R6 can not possibly be "46". Gain would be obscene, everything would be clipped. Going by the gain, they should be near 420 Ohms. (Maybe "460" Ohms?)
With that correction, the preamp should be suitable for on-site checking of tag-sale records. I assume a 4-inch speaker so I will not quibble about RIAA error at 30Hz or sub-sonic 1/f noise.
I have marked-up the plan. Added + marks on e-Caps, noted an alternate transistor which will work fine and readily available. If the one battery also feeds a power amplifier to the speaker, you need an R-C network to reduce sneak-back from power amp surges to this low-PSRR preamp.
"460K" is a very odd value (factory over-stock?), 470K or 390K is fine. The bone-stock EQ values must be pure luck: they do work-out well within 1dB. Those values may as well be 5% tolerance; all else can be even 20% tolerance, but 5% is probably today's best buy. R7 R8 interact with transistor hFE, but for high-hFE parts as specified the 220k values is fine far below 100Hz, lower than any suitcase.
Shudder.....
Actually, this is NOT the older model made with rejects from the pocket radio factory. That's actually a pretty spiffy transistor.
The "specs".... ah, whoever typed the data didn't know specs. Same person did the schematic values?
R5 R6 can not possibly be "46". Gain would be obscene, everything would be clipped. Going by the gain, they should be near 420 Ohms. (Maybe "460" Ohms?)
With that correction, the preamp should be suitable for on-site checking of tag-sale records. I assume a 4-inch speaker so I will not quibble about RIAA error at 30Hz or sub-sonic 1/f noise.
I have marked-up the plan. Added + marks on e-Caps, noted an alternate transistor which will work fine and readily available. If the one battery also feeds a power amplifier to the speaker, you need an R-C network to reduce sneak-back from power amp surges to this low-PSRR preamp.
"460K" is a very odd value (factory over-stock?), 470K or 390K is fine. The bone-stock EQ values must be pure luck: they do work-out well within 1dB. Those values may as well be 5% tolerance; all else can be even 20% tolerance, but 5% is probably today's best buy. R7 R8 interact with transistor hFE, but for high-hFE parts as specified the 220k values is fine far below 100Hz, lower than any suitcase.
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Why 9 V? Why not a Li powerbank with converter?
For the same task I used once a modified NAd 5120 turntable (kept the original cheap czech cartridge it came with). It's subchassis has good suspension, the tonearm has a resonance damper, the synchronous motor can be easily replaced with a DC-type and there is plenty of space for preamp and headphone-amp. I wouldn't use speakers to check records on a noisy market.
RIAA-preamp? A low-noise op-amp with J-FET input and output rail-to-rail capabilities (due to the low supply voltage) will suffice.
Edit: You should think about a USB-microscope too.
For the same task I used once a modified NAd 5120 turntable (kept the original cheap czech cartridge it came with). It's subchassis has good suspension, the tonearm has a resonance damper, the synchronous motor can be easily replaced with a DC-type and there is plenty of space for preamp and headphone-amp. I wouldn't use speakers to check records on a noisy market.
RIAA-preamp? A low-noise op-amp with J-FET input and output rail-to-rail capabilities (due to the low supply voltage) will suffice.
Edit: You should think about a USB-microscope too.
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