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Rechargeable Battery Pack for Phonostage


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Hello,

 

i am not sure if it is popular DIY option and is there a way to make rechargeable 12V DC battery pack to phonoboard? I have TC-750LC MM phono preamp which I lost AC/DC switch power supply wall adaptor and thinking to power with rechargeable battery pack instead of noisey switch power supply if possible.

 

Any idea, suggestion or guidance would be greatly appreciated and well considered.

 

Thank you....

 

 

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Jaycar sell a decent universal wall wart that does 12 volts, it isn't Hi Fi (i.e. it looks ugly) but will work well for something like a phono stage that isn't drawing a lot of power.  Not sure about noise, I use the universal jaycar ones for pretty much anything that requires DC power under 4 amps.

 

By far the simplest is to string together a pile of recharcheable AA batteries (8 of them in series will do).  Easy to charge with a readily available plug pack.  Then all you need is the correct sized barrel (if that is what the phono pre-amp uses) and a bit of wire.  Put it all in a fancy box.  Would make a fun, extremely easy project that requires virtually no electronics knowledge.

 

If you needed to get super fancy, the big 12V rechargeable batteries used for things like alarm systems are expensive and require better chargers, but would give you a longer time between charges.

 

Only thing to watch is getting the barrel connecter positive and negative the right way around.

 

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17 minutes ago, Old Man Rubber said:

Jaycar sell a decent universal wall wart that does 12 volts, it isn't Hi Fi (i.e. it looks ugly) but will work well for something like a phono stage that isn't drawing a lot of power.  Not sure about noise, I use the universal jaycar ones for pretty much anything that requires DC power under 4 amps.

 

By far the simplest is to string together a pile of recharcheable AA batteries (8 of them in series will do).  Easy to charge with a readily available plug pack.  Then all you need is the correct sized barrel (if that is what the phono pre-amp uses) and a bit of wire.  Put it all in a fancy box.  Would make a fun, extremely easy project that requires virtually no electronics knowledge.

 

If you needed to get super fancy, the big 12V rechargeable batteries used for things like alarm systems are expensive and require better chargers, but would give you a longer time between charges.

 

Only thing to watch is getting the barrel connecter positive and negative the right way around.

 

 

Thank you very much for the suggestion and ideas.

 

Would this type of rechargeable battery pack work for this specific purpose?

 

https://www.ebay.com.au/itm/DC-168-DC-12V-1800mAh-Battery-for-CCTV-Camera-GPS-Wireless-Baby-Monitor-w-Plug/293219435203

 

According to the spec, the output current is 1.8A and if I remember correctly, TC750LC board takes 12V 1A.  🤔

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1 hour ago, Spider27 said:

Hello,

 

I have TC-750LC MM phono preamp which I lost AC/DC switch power supply wall adaptor and thinking to power with rechargeable battery pack instead of noisey switch power supply if possible.

 

I presume you mean you've lost the 12v DC 'wall wart' (SMPS)?

 

1 hour ago, Spider27 said:

 

i am not sure if it is popular DIY option and is there a way to make rechargeable 12V DC battery pack to phonoboard?

 

 

To do a good job is not 'simple'.  :(  Ideally, a 12v SLA would be mounted inside a case, with:

  • charger sockets on the back
  • a 12v DC umbilical on the back - with a barrel plug on the end which fits your TC-750LC
  • a switch on the front to connect the SLA to either: a. the charger or b. the umbilical.

Much cheaper to simply buy a replacement 12v 'wall wart' from Jaycar.  :)  (Although the SLA will certainly be quieter!)

 

Andy

 

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4 minutes ago, Spider27 said:

 

 

 

According to the spec, the output current is 1.8A and if I remember correctly, TC750LC board takes 12V 1A.  🤔

Double check the current draw but yeah something like that would be pretty much ideal - just a matter of getting the barrel plug in the correct size (I have no idea why they vary so much, even on equipment of the same voltage you get a pile of different sizes).

 

edit:

https://www.jaycar.com.au/12v-dc-2-5a-power-supply-7dc-plugs/p/MP3490

 

I usually buy the one that you can switch the voltage on (there is one available that you can switch between 3v and 12v) but having to faff around with that as well as the plugs is painful and this one is cheaper.

 

Edited by Old Man Rubber
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6 minutes ago, andyr said:

 

I presume you mean you've lost the 12v DC 'wall wart' (SMPS)?

 

 

To do a good job is not 'simple'.  :(  Ideally, a 12v SLA would be mounted inside a case, with:

  • charger sockets on the back
  • a 12v DC umbilical on the back - with a barrel plug on the end which fits your TC-750LC
  • a switch on the front to connect the SLA to either: a. the charger or b. the umbilical.

Much cheaper to simply buy a replacement 12v 'wall wart' from Jaycar.  :)  (Although the SLA will certainly be quieter!)

 

Andy

 

 

Yes, anything outside standard gets complicated. 😔 

 

Jaycar does not have 12V 1A adapter but have 12v 0.4a or 12v 1.5a. 

 

https://www.jaycar.com.au/12v-dc-1-5a-slim-power-supply-7dc-plugs/p/MP3486

https://www.jaycar.com.au/12v-dc-400ma-ultra-slim-power-supply-7dc-plugs/p/MP3147

 

Is it ok to use 1.5a option or better go for smaller than spec?

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28 minutes ago, Spider27 said:

 

 

 

Is it ok to use 1.5a option or better go for smaller than spec?

You can consider the amp rating a minimum.  If the device wants 1A then the minimum power supply you need to buy is 1A.

 

Anything that is rated less will overheat / break / catch fire / cause a loss of magic smoke etc.

 

Anything 1 amp or better (sky is the limit) as long as the voltage matches will power your device.

 

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26 minutes ago, Old Man Rubber said:

You can consider the amp rating a minimum.  If the device wants 1A then the minimum power supply you need to buy is 1A.

 

Anything that is rated less will overheat / break / catch fire / cause a loss of magic smoke etc.

 

Anything 1 amp or better (sky is the limit) as long as the voltage matches will power your device.

 

Thank you very much for the info. 

I will try both methods and will report back. (It may take about a month since battery is coming from overseas)

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58 minutes ago, Spider27 said:

 

Yes, anything outside standard gets complicated. 😔 

 

Jaycar does not have 12V 1A adapter but have 12v 0.4a or 12v 1.5a. 

 

https://www.jaycar.com.au/12v-dc-1-5a-slim-power-supply-7dc-plugs/p/MP3486

https://www.jaycar.com.au/12v-dc-400ma-ultra-slim-power-supply-7dc-plugs/p/MP3147

 

Is it ok to use 1.5a option or better go for smaller than spec?

 

Altronics show a 12v DC / 1a wall wart for $22.50.  Part no. M8932B.

 

Andy

 

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This phono preamp is not going to draw 1A.    I found one on sale where they had "improved" the power supply to 500ma, so obviously it uses way less than that.   Given the typical phono circuit, that would be expected.

 

 

image.png.d71b803baabf81ce0cd56fb5b872e8f8.png

 

 

image.png.2eb5605f8dfc5589f914ca5f22daff1a.png

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4 minutes ago, aussievintage said:

This phono preamp is not going to draw 1A.    I found one on sale where they had "improved" the power supply to 500ma, so obviously it uses way less than that.   Given the typical phono circuit, that would be expected.

 

image.png.2eb5605f8dfc5589f914ca5f22daff1a.png

 

Yep. that is exactly the one.

 

Will it be okay to power it with 12V DC 1.8A regulated power supply or better need it to be exact 500mA?

 

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26 minutes ago, Spider27 said:

Will it be okay to power it with 12V DC 1.8A regulated power supply or better need it to be exact 500mA?

This is a common misunderstanding of electricity.  You need a power source with the correct voltage, yes, but the current figure is a maximum capability rating of the power supply.  So a 1.8A supply can be used for any equipment that draws LESS than the max , up to 1.8A.  The only problem is that it costs more than the properly sized (could be smaller)  12V supply.

Edited by aussievintage
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I use this for my headamp https://www.ebay.com.au/itm/High-Quality-Portable-DC-12V-10000mAh-Lithium-rechargeable-Battery-Pack-5-5X2-1/163272020787 does a decent job and really quiet. The regulator does a decent job keeping the voltage constant which you won't get if you use a straight battery or SLA the voltage will go down as the charge goes down. And if it's silent for a mc head amp it will be silent for a phono

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6 minutes ago, mloutfie said:

I use this for my headamp https://www.ebay.com.au/itm/High-Quality-Portable-DC-12V-10000mAh-Lithium-rechargeable-Battery-Pack-5-5X2-1/163272020787 does a decent job and really quiet. The regulator does a decent job keeping the voltage constant which you won't get if you use a straight battery or SLA the voltage will go down as the charge goes down. And if it's silent for a mc head amp it will be silent for a phono

 

Sounds veryinteresting - but what exactly is that, Mahdie?

  1. You have it plugged into the wall continuously ... and it has a 12v output to feed your 'Paris'?
  2. What socket does it need for the headamp - 2.1 mm barrel or 2.5 mm?
  3. Is the charger continuously connected to the lithium rechargeable battery which feeds the Paris ... or do you swap from 'feed head amp ' to 'charge battery '?

 

Thanks,

Andy

 

 

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20 minutes ago, mloutfie said:

I use this for my headamp https://www.ebay.com.au/itm/High-Quality-Portable-DC-12V-10000mAh-Lithium-rechargeable-Battery-Pack-5-5X2-1/163272020787 does a decent job and really quiet. The regulator does a decent job keeping the voltage constant which you won't get if you use a straight battery or SLA the voltage will go down as the charge goes down. And if it's silent for a mc head amp it will be silent for a phono

Looks good.  I had also wondered about using one of those LiPo packs they sell for jump-starting cars.

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11 hours ago, andyr said:

 

Sounds veryinteresting - but what exactly is that, Mahdie?

  1. You have it plugged into the wall continuously ... and it has a 12v output to feed your 'Paris'?
  2. What socket does it need for the headamp - 2.1 mm barrel or 2.5 mm?
  3. Is the charger continuously connected to the lithium rechargeable battery which feeds the Paris ... or do you swap from 'feed head amp ' to 'charge battery '?

 

Thanks,

Andy

 

 

Hi Andy,

 

It's a rechargeable battery so the plugpack is a charger rather than a DC adaptor. You charge it full then you take it off the charger. There is an on off switch so it doesn't drain power when it's not in use even though its still plugged in to the Paris.

 

One bad thing it is not possible to know how much charge left so I just charge it every 2 weeks or so to keep it charge that will last 10 hours a week session. Paris doesn't take that much power. The charging time is quite quick an hour or so. But looking at this model they seems to have updated with a charge level indicator which is good.

 

I can double check but I think it's 2.1mm barrel plug.

 

Basically this is just a bank of 18650 battery with a voltage regulator. You can't definitely diy this and spend less

 

These are the specs 

 

Specifications
Model: DC-121000
Capacity: 10000mAh
Limited Charge Voltage: 12.6v
Output Voltage: 12v
Maximum Current Input: 3a
Maximum Current Output: 3a
Protection: Over-discharge, Over charge, Short-circuit
Dimensions: 25mm X 85mm X135mm 
Edited by mloutfie
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30 minutes ago, mloutfie said:

Hi Andy,

 

It's a rechargeable battery so the plugpack is a charger rather than a DC adaptor. You charge it full then you take it off the charger. There is an on off switch so it doesn't drain power when it's not in use even though its still plugged in to the Paris.

 

One bad thing it is not possible to know how much charge left so I just charge it every 2 weeks or so to keep it charge that will last 10 hours a week session. Paris doesn't take that much power. The charging time is quite quick an hour or so. But looking at this model they seems to have updated with a charge level indicator which is good.

 

I can double check but I think it's 2.1mm barrel plug.

 

Basically this is just a bank of 18650 battery with a voltage regulator. You can't definitely diy this and spend less

 

 

Thanks very much for the info, Mahdie.  It sounds very suitable for the 'Paris' head amp - so I will buy one.

 

Regards,

Andy

 

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38 minutes ago, mloutfie said:

Hi Andy,

 

It's a rechargeable battery so the plugpack is a charger rather than a DC adaptor. You charge it full then you take it off the charger. There is an on off switch so it doesn't drain power when it's not in use even though its still plugged in to the Paris.

 

One bad thing it is not possible to know how much charge left so I just charge it every 2 weeks or so to keep it charge that will last 10 hours a week session. Paris doesn't take that much power. The charging time is quite quick an hour or so. But looking at this model they seems to have updated with a charge level indicator which is good.

 

I can double check but I think it's 2.1mm barrel plug.

 

Basically this is just a bank of 18650 battery with a voltage regulator. You can't definitely diy this and spend less

 

These are the specs 

 

Specifications
Model: DC-121000
Capacity: 10000mAh
Limited Charge Voltage: 12.6v
Output Voltage: 12v
Maximum Current Input: 3a
Maximum Current Output: 3a
Protection: Over-discharge, Over charge, Short-circuit
Dimensions: 25mm X 85mm X135mm 

 

Thank you for sharing the info.

May I double check two sockets?  Is USB plug for charging the unit and DC plug is output to another device to supply power?

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48 minutes ago, Spider27 said:

 

Thank you for sharing the info.

May I double check two sockets?  Is USB plug for charging the unit and DC plug is output to another device to supply power?

 

Maybe not... The first and last 3rd photo shows no USB but DC plug input only. Second photo show USB socket but it may be copied from another item.

 

s-l1600.jpg

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17 hours ago, Spider27 said:

 

Thank you very much for the suggestion and ideas.

 

Would this type of rechargeable battery pack work for this specific purpose?

 

https://www.ebay.com.au/itm/DC-168-DC-12V-1800mAh-Battery-for-CCTV-Camera-GPS-Wireless-Baby-Monitor-w-Plug/293219435203

 

According to the spec, the output current is 1.8A and if I remember correctly, TC750LC board takes 12V 1A.  🤔

Okay, two issues I see here.

 

1.  The plugpack power supply is bound to be a switch-mode.  IME not really recommended for audio, especially low level signal devices like pre-amps.  The d.c. output would be most likely riddled with noise which could contaminate the audio depending on how well the filtering is in the actual amplifier itself is.  Okay to charge a battery but not recommended as the main power source to run the pre-amp from.

 

2.  The 1800mAh battery when used on its own to power the amp will not last long.  1800mAH = 1.8Ah giving you approximately 1.8 hours of listening time based on the amp drawing 1A of current.  Obviously longer listening time is possible if the actual current drawn is less than 1A.

 

If it was me I would purchase a linear power supply capable of delivering a minimum of 1.5A and a good old fashioned 8Ah SLA battery..  The battery acts as a nice smoothing capacitor once fully charged and this will further reduce hum from the power supply whilst in use.  SLA batteries are safer than Li-Ion of questionable lineage and the 8Ah capacity will yield at least 8 hours of listening on battery power only should you want to have a nice quiet power supply..

 

As a rule of thumb. batteries should not be rapidly charged or discharged.  The 0.5C rule should be considered the minimum, so the battery doesn't become hot during the charge or discharge cycles.  Rapid charging or over-current discharging can lead to battery failure, in some cases with catastrophic results like a fire for example.  Lower charge / discharge rates of 0.1C or thereabouts are much safer and the batteries will last a lot longer too.

 

Cheers,

Alan R.

 

Edited by Monkeyboi
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10 minutes ago, Monkeyboi said:

Okay, two issues I see here.

 

1.  The plugpack power supply is bound to be a switch-mode.  IME not really recommended for audio, especially low level signal devices like pre-amps.  The d.c. output would be most likely riddled with noise which could contaminate the audio depending on how well the filtering is in the actual amplifier itself is.

 

2.  The 1800mAh battery when used on its own to power the amp will not last long.  1800mAH = 1.8Ah giving you approximately 1.8 hours of listening time based on the amp drawing 1A of current.  Obviously longer listening time is possible if the actual current drawn is less than 1A.

 

If it was me I would purchase a linear power supply capable of delivering a minimum of 1.5A and a good old fashioned 8Ah SLA battery..  The battery acts as a nice smoothing capacitor once fully charged and this will further reduce hum from the power supply whilst in use.  SLA batteries are safer than Li-Ion of questionable lineage and the 8Ah capacity will yield at least 8 hours of listening on battery power only should you want to have a nice quiet power supply..

 

As a rule of thumb. batteries should not be rapidly charged or discharged.  The 0.5C rule should be considered the minimum, so the battery doesn't become hot during the charge or discharge cycles.  Rapid charging or over-current discharging can lead to battery failure, in some cases with catastrophic results like a fire for example.  Lower charge / discharge rates of 0.1C or thereabouts are much safer and the batteries will last a lot longer too.

 

Cheers,

Alan R.

 

 

Thank you so much for sharing the info and suggestion. 

 

Re: Linear power supply, would it still matter if unit will be used only battery power without charger connected when using and charger will only be used when charging the battery?

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16 minutes ago, Monkeyboi said:

Okay, two issues I see here.

 

1.  The plugpack power supply is bound to be a switch-mode.  IME not really recommended for audio, especially low level signal devices like pre-amps.  The d.c. output would be most likely riddled with noise which could contaminate the audio depending on how well the filtering is in the actual amplifier itself is.

 

2.  The 1800mAh battery when used on its own to power the amp will not last long.  1800mAH = 1.8Ah giving you approximately 1.8 hours of listening time based on the amp drawing 1A of current.  Obviously longer listening time is possible if the actual current drawn is less than 1A.

 

If it was me I would purchase a linear power supply capable of delivering a minimum of 1.5A and a good old fashioned 8Ah SLA battery..  The battery acts as a nice smoothing capacitor once fully charged and this will further reduce hum from the power supply whilst in use.  SLA batteries are safer than Li-Ion of questionable lineage and the 8Ah capacity will yield at least 8 hours of listening on battery power only should you want to have a nice quiet power supply..

 

As a rule of thumb. batteries should not be rapidly charged or discharged.  The 0.5C rule should be considered the minimum, so the battery doesn't become hot during the charge or discharge cycles.  Rapid charging or over-current discharging can lead to battery failure, in some cases with catastrophic results like a fire for example.  Lower charge / discharge rates of 0.1C or thereabouts are much safer and the batteries will last a lot longer too.

 

Cheers,

Alan R.

 

Agree with most of this, except the reliability/reputation of Li-Ion Batteries, that have been problematic in the past. But they are pretty well used in any mobile device these days.

 

Also the same appraisal of the other one showing the bank of 3 X 18650 batteries (nominally 3.7V 2500mAh) rated at 10000mAh. They may have slightly overstated the capacity of the battery bank, if you do the sums it gives a max of 7500mAh before losses are considered. Which is a fair bit anyway. But it is also a DC-DC voltage converter type, to bring the total of 10.1VDC up to a little over 12VDC, then regulated back down to 12VDC output.

 

Depending on the voltage converter design, they can be relatively quiet, but you won't know till you get one and test it.

Edited by bob_m_54
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49 minutes ago, Spider27 said:

Maybe not... The first and last 3rd photo shows no USB but DC plug input only. Second photo show USB socket but it may be copied from another item.

 

 

38 minutes ago, Monkeyboi said:

1.  The plugpack power supply is bound to be a switch-mode.  IME not really recommended for audio, especially low level signal devices like pre-amps.  The d.c. output would be most likely riddled with noise which could contaminate the audio depending on how well the filtering is in the actual amplifier itself is.  Okay to charge a battery but not recommended as the main power source to run the pre-amp from.

Charging and output port is the same. It is using a charging adaptor not a dc plug pack input completely different type of adapter. You can't use the adapter and use the battery the same time

 

2 hours ago, andyr said:

Thanks very much for the info, Mahdie.  It sounds very suitable for the 'Paris' head amp - so I will buy one.

 

Its quieter that ifi ipower for paris. ifi is quiet enough for most usage but for something that really low voltage output like paris a high pitched noise is picked up.

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55 minutes ago, Spider27 said:

 

Thank you so much for sharing the info and suggestion. 

 

Re: Linear power supply, would it still matter if unit will be used only battery power without charger connected when using and charger will only be used when charging the battery?

Any suitable power supply can be used to charge a Li-ion battery where the battery has its own internal BMS (battery management system) as the BMS controls the charging and discharging of the battery.  The problem with most switchmode power supplies used in a float / charge configuration is noise from the switchmode power supply when used in the float configuration (that is charging the battery and powering the device at the same time.)  Because the noise produced by switchmode power supplies is mainly high frequency in nature the battery even in float configuration doesn't effectively remove the switching noise from the supply.

 

It has been mentioned that you can buy very low noise switchmode power supplies.  This is true, but not at the price point of the eBay item you linked to.   I recall in this thread one of the respondents refers to the power supply recommended by the manufacturer of your phono pre-amp.  It uses a regulated switchmode unit.   Most likely (but without a service manual it's only speculation) it uses a linear regulator inside.  Best of both worlds - cheapness, compactness and efficiency of the switchmode part and the electrical quietness of the linear regulator.  You'd be surprised just how much noise can be removed from a "noisy" supply by the use of a simple series regulator chip like a LM7812 or uA7812 IC regulator and a couple of ceramic multi-layer capacitors.

 

With SLA batteries, no BMS is required as the battery draws very little current when it approaches the fully charged condition.  That's why SLA batteries are so extensively used in a float / charge configuration.  A 12v SLA battery should be charged to approximately 14.4v for optimal charge capacity and life.  Undercharging SLA batteries can lead to sulphation within the cells and this will reduce the battery lifespan.  I will try to obtain a service manual for your phono stage and see how the 12v supply is utilised within the unit, then comment further.

 

For what it's worth, consider purchasing the regulated power supply recommended by the manufacturer.  I'm quite sure they wouldn't market a power supply which was likely to compromise the performance of the phono pre-amp..  After all it's their reputation at stake.

 

As for pure battery powering, batteries are not a noise free source of power.  This article on Li-ion batteries makes for interesting reading - https://www.researchgate.net/publication/309230404_Noise_Diagnosis_of_Commercial_Li-ion_Batteries_Using_High-Order_Moments

 

Cheers,

Alan R.

 

 

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Okay,  I've checked out the innards of this phono pre-amp. 

 

It's a very simple design that uses three 2SC945 NPN silicon transistors per channel running from a single ended 12v supply that uses no internal voltage regulation.

 

The power input uses a 1N4007 diode for reverse voltage protection, one 220uF electrolytic + 100nF ceramic disc + one 1000uF capacitor as additional filtering over and above what the external power supply can offer.  IMHO running this from a pure battery supply with the implication that a battery would be a superior power source would be like casting pearl before swine.  No offence intended, it's just a fact of life in this case.

 

Any half decent regulated linear 12v power supply would be more than ample.  The current consumption would in my estimation be about 100mA absolute maximum, so the manufacturer's 500mA supply is more than adequate.

 

If you really want to improve the sound of this phono pre-amp, forget about battery operation and change 4 of the coupling electrolytic capacitors in the signal path with Wima film capacitors.

 

Cheers,

Alan R.

 

 

TCC TC-759LC_PCB Top.jpg

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4 minutes ago, Monkeyboi said:

Okay,  I've checked out the innards of this phono pre-amp. 

 

It's a very simple design that uses three 2SC945 NPN silicon transistors per channel running from a single ended 12v supply that uses no internal voltage regulation.

 

The power input uses a 1N4007 diode for reverse voltage protection, one 220uF electrolytic + 100nF ceramic disc + one 1000uF capacitor as additional filtering over and above what the external power supply can offer.  IMHO running this from a pure battery supply with the implication that a battery would be a superior power source would be like casting pearl before swine.  No offence intended, it's just a fact of life in this case.

 

Any half decent regulated linear 12v power supply would be more than ample.  The current consumption would in my estimation be about 100mA absolute maximum, so the manufacturer's 500mA supply is more than adequate.

 

If you really want to improve the sound of this phono pre-amp, forget about battery operation and change 4 of the coupling electrolytic capacitors in the signal path with Wima film capacitors.

 

Cheers,

Alan R.

 

Thank you again for the suggestion. My one must be modified one because it looks a bit different to stock one that you featured.

 

 

IMG_6483.JPG

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My board has 1uJ63 from WIMA (red ones) in 2 spots on 10U/50 and 2 spots on 4U7/50.  And, no caps on 2 spots on 220U/16.  🤔

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3 minutes ago, Spider27 said:

 

Thank you again for the suggestion. My one must be modified one because it looks a bit different to stock one that you featured.

 

 

IMG_6483.JPG

Yes, your's has the 4 coupling capacitors replaces with film capacitors, albeit with different capacitance values.  1uF units replacing 4.7uF and 10uF ???

 

The power supply section has the reverse polarity protection diode replaced by a wire link :( which isn't good if someone accidentally connects a power adapter with a reversed polarity to the power input jack.  The filtering capacitors in the power supply have been also removed   Possibly not that important as the manufacturer's PSU is supposed to be regulated and well filtered,however if it was me I'd be fitting the missing electrolytics if only to provide adequate on-board local PSU decoupling.  The 220uF /  16VW capacitors specified on the silk screen overlay would be adequate for the job.

 

The two loading capacitors, each of 220pF have been removed from the input stage.  Whilst this isn't really an issue I guess you have to ask why as most MM cartridges require some shunt capacitance loading to optimise the frequency response especially in the upper audio frequency range.  This shunting capacitance should be in accordance with the cartridge manufacturer's recommendations and is made up of the capacitance of the tonearm leads, turntable / interconnect leads to the phono pre-amp inputs and the input capacitance of the phono stage itself.

 

May I ask what cartridge are you using with this phono pre-amp?

 

Cheers,

Alan R.

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Jim Hagerman uses 1mH inductors on the rails to eliminate SMPS noise in his Bugle phono stages

 

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38 minutes ago, Monkeyboi said:

Yes, your's has the 4 coupling capacitors replaces with film capacitors, albeit with different capacitance values.  1uF units replacing 4.7uF and 10uF ???

Yes, it is weird why same 1uf for all 4 spots. I might need to replace them to correct value of WIMA caps.

 

And, when I check all of caps with ERS meters, i found that 2 caps on 100u/16v spot are out of spec. I will change them with 100uf 25v caps that I currently have. Hope it is ok.

 

38 minutes ago, Monkeyboi said:

The power supply section has the reverse polarity protection diode replaced by a wire link :( which isn't good if someone accidentally connects a power adapter with a reversed polarity to the power input jack.  The filtering capacitors in the power supply have been also removed   Possibly not that important as the manufacturer's PSU is supposed to be regulated and well filtered,however if it was me I'd be fitting the missing electrolytics if only to provide adequate on-board local PSU decoupling.  The 220uF /  16VW capacitors specified on the silk screen overlay would be adequate for the job.

 

The two loading capacitors, each of 220pF have been removed from the input stage.  Whilst this isn't really an issue I guess you have to ask why as most MM cartridges require some shunt capacitance loading to optimise the frequency response especially in the upper audio frequency range.  This shunting capacitance should be in accordance with the cartridge manufacturer's recommendations and is made up of the capacitance of the tonearm leads, turntable / interconnect leads to the phono pre-amp inputs and the input capacitance of the phono stage itself.

 

I have spare 220uf 50v caps at hand so can use these new caps in those 2 empty spots. 

38 minutes ago, Monkeyboi said:

 

May I ask what cartridge are you using with this phono pre-amp?

 

Cheers,

Alan R.

 

I am planning to use Nagaoka MP-110 cart on this pre. :) 

 

I have not tested this pre as yet because I lost power supply and cannot locate it but if my memory serves me correctly, this one had an issue with one channel distorted (not sure if it was left or right).

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29 minutes ago, Spider27 said:

Yes, it is weird why same 1uf for all 4 spots. I might need to replace them to correct value of WIMA caps.

That would be a good idea.  You can get those Wima film caps in tall skinny configuration which should fit neatly in the spots provided.  any in their 50 or 63v range is more than adequate.  Here's an Australian supplier (not endorsing them, but they carry both values you require.

https://www.pedalpartsaustralia.com/index.php?main_page=index&cPath=82_86

 

29 minutes ago, Spider27 said:

And, when I check all of caps with ERS meters, i found that 2 caps on 100u/16v spot are out of spec. I will change them with 100uf 25v caps that I currently have. Hope it is ok. 

Electrolytic capacitors have a working lifespan.  An increase in ESR isn't anything unusual unfortunately.  :(

Going slightly higher in working voltage isn't an issue.

 

29 minutes ago, Spider27 said:

I have spare 220uf 50v caps at hand so can use these new caps in those 2 empty spots. 

Sweet.

 

29 minutes ago, Spider27 said:

I am planning to use Nagaoka MP-110 cart on this pre. :) 

That cartridge's optimum load is 47k || 100pF. Most of that shunting capacitance is most likely to be in your T/T leads so no need to refit the missing two 220pF caps. :)  You can verify the capacitance of your T/T cables using your capacitance meter.

 

29 minutes ago, Spider27 said:

I have not tested this pre as yet because I lost power supply and cannot locate it but if my memory serves me correctly, this one had an issue with one channel distorted (not sure if it was left or right).

You may find that a faulty cap may be contributing to the distortion issue.

 

Anyhow, get it going and post back here how you went.

 

Cheers,

Alan R.

Edited by Monkeyboi
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Don't quite understand you, Nada?

 

12 hours ago, Nada said:

For a phono amp clean regulated power is indicated that has

  • regulated 12V DC,  not over-voltage from a  "12V"  lead battery

 

Are you suggesting the full charge voltage on a 12v SLA - which can exceed 13v - is dangerous to  a phono stage?

 

I don't see how it can - the minimum rating of any electros used will be 25v

 

12 hours ago, Nada said:
  • no switch noise as from a lithium "battery"

 

Are you saying that a lithium battery has 'switch noise'?  What noise is this?

 

12 hours ago, Nada said:
  • no recharging hassles

 

I agree this is an advantage of using a LPS!  :thumb:

 

Andy

 

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59 minutes ago, andyr said:

Are you suggesting the full charge voltage on a 12v SLA - which can exceed 13v - is dangerous to  a phono stage?

 

I don't see how it can - the minimum rating of any electros used will be 25v

There are other reasons a circuit might be limited to the max voltage that it should be operated at, not just electros. Operating points of transistors etc will shift,  regulators will run hotter, etc  but it's hard to imagine a small difference will matter.

 

59 minutes ago, andyr said:

Are you saying that a lithium battery has 'switch noise'?  What noise is this?

I was going to ask the same thing.     The battery itself won't, but some batteries have built in management circuitry, maybe this.

Edited by aussievintage
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Lithium 12v supplies like

 

https://i.ebayimg.com/images/g/2GsAAOSwt69eU1wh/s-l1600.jpg

 

will need regulation to put out a steady 12.0V.  Switching regulators can be small, efficient and cool for DC/DC voltage regulation. So the idea a lithium 12v battery pack yields clean battery power at 12.0V without switching noise might be a false assumption.  Depends on the quality of the electronics.  As long as it sounds good...

Edited by Nada
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36 minutes ago, Nada said:

Lithium 12v supplies like

 

 

 

will need regulation to put out a steady 12.0V.  Switching regulators can be small, efficient and cool for DC/DC voltage regulation. So the idea a lithium 12v battery pack yields clean battery power at 12.0V without switching noise might be a false assumption.  Depends on the quality of the electronics.  As long as it sounds good...

I was thinking of something like

image.png.80df3af13b9255f0c1345a7b6d213343.png

 

Which does not need any regulation really.  It's discharge curve is flat enough

 

image.png.656d1ad2b8aa0fd057a83e57e9ddf789.png

Edited by aussievintage
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2 hours ago, aussievintage said:

 

There are other reasons a circuit might be limited to the max voltage that it should be operated at, not just electros. Operating points of transistors etc will shift,  regulators will run hotter, etc  but it's hard to imagine a small difference will matter.

 

 

That may well be, av - but those other reasons pale into insignificance beside the issue of trying to power a phono stage from +12vDC!  :(

 

+/-12v DC - certainly! Or +24v DC, for a SE circuit like I use in my 'Muse'. But 12v simply doesn't provide sufficient headroom for good transient response.

 

Do the maths:

  • Input is 5mV, peak to peak
  • Coming off the groove, HFs are boosted by up to 20dB (10x)
  • So HFs come into the  phono stage at up to 50mV, ptp
  • 1st gain stage has, say, 30x gain
  • So the signal exits the 1st gain stage at 1.5V ptp
  • Even if transients are only 10x .. that gives 15v ptp!  (Some people say transients rise even more).

 

Regards,

Andy

 

 

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10 minutes ago, andyr said:

 

That may well be, av - but those other reasons pale into insignificance beside the issue of trying to power a phono stage from +12vDC!  :(

 

+/-12v DC - certainly! Or +24v DC, for a SE circuit like I use in my 'Muse'. But 12v simply doesn't provide sufficient headroom for good transient response.

 

Do the maths:

  • Input is 5mV, peak to peak
  • Coming off the groove, HFs are boosted by up to 20dB (10x)
  • So HFs come into the  phono stage at up to 50mV, ptp
  • 1st gain stage has, say, 30x gain
  • So the signal exits the 1st gain stage at 1.5V ptp
  • Even if transients are only 10x .. that gives 15v ptp!  (Some people say transients rise even more).

 

Regards,

Andy

 

 

You were querying if 13V is dangerous to a phonostage that normally runs off 12V  Nothing to do with the new issue you are now raising.

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1 hour ago, aussievintage said:

You were querying if 13V is dangerous to a phonostage that normally runs off 12V  Nothing to do with the new issue you are now raising.

 

Not so, av - I was suggesting that 13v was absolutely fine.

 

My subsequent post was to suggest that 13v vs. 12v was unimportant - as  the vital issue was the too-low voltage rail.

 

Andy

 

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