Looking for AOL Sperry LM3875 schematic

[jmillerdoc]

Hi,
I bought a pair of AOL Sperry LM3875 boards a while back and now cannot locate the schematic to build them. Anyone out there have a copy or have the parts list?
Thanks,
Jeff

 

[blu_glo]

Sperry Gainclone PCB assembley

Hi I know its one year old but if you are still looking I'm sure I have the original PDF somewhere! Don't worry I not asking for money - its just on another older computer that actually still has a lot of documents I should have salvaged.... Answer me by PM if you wish!

:edited by mod to remove email address.

 

[pacificblue]

It is good practice not to publish e-mail addresses in posts for your own safety. You can PM or ask another member to PM.

 

[jmillerdoc]

Or, set up a trash email account like i do....gmail is good for this, you can keep yourprivacy by providing bogus info to open a mail account.....i have two or thee of these....

I sent you an email, i could still use the schema....

 

[blu_glo]

HA!

 

[blu_glo]

Ha! thankyou Pacificblue for your advice, any way I can get that message edited with the email address replaced with " pm me "? Cannot see any obvious way to to this ....Administrator??!!

 

[pinkmouse]

Use the "report post" button. But as I'm here I've sorted it.

 

[blu_glo]

Thank you, Pinkmouse for replacing the email address line; it was one I'd rather not loose!

 

[blu_glo]

hi Jim did not recieve your email I have the document scanned in pdf ready. regards, Simon

 

[pieroh]

AOL Speryy Audio

Hi I know its one year old but if you are still looking I'm sure I have the original PDF somewhere! Don't worry I not asking for money - its just on another older computer that actually still has a lot of documents I should have salvaged.... Answer me by PM if you wish!

:edited by mod to remove email address.

eleven years later, same problem ;-)

I also have two of those LM3875 PCBs around but no documentation.
Can you please send me a copy.

Regards
Peter

 

[blu_glo]

Sperry info sheet

- Please find attached! Best Luck!

Simon

 

[pieroh]

AOL Sperry PCBs

Many thanks Simon!

Best regards
Peter

 

[blu_glo]

Its not the complete story, I have the assembly instructions scan in pdf but can't upload it - it somehow ended up as 10MB file..... Attached is a poor quality scan you might be able to make out. I'll see what I can do at the weekend, a rescan is in order. You may however have enough clues here to help you. Supply capacitors whatever you can fit at the voltage you are using!!!! 4 off 1,000uF 50V should cover most needs....

 

[pieroh]

Dear Simon,

this is a very informative and well-written documentation, that can be useful for other chipamp builders too.
I am using the LM3875 PCBs in T-network configuration (inverting amplifier) with tube input buffer and will post my findings.

Regards
Peter

 

[blu_glo]

I will be very interested particularly how you do the valve buffer to see the result!

 

[blu_glo]

Tidied up main Sperry document.....

Here is a better copy of the Sperry PCB documentation. If admin wish to remove the previous one to save space that'll inconvenience no-one.....

 

[AndrewT]

eleven years later, same problem ;-)

I also have two of those LM3875 PCBs around but no documentation.
Can you please send me a copy.

Regards
Peter

- Please find attached! Best Luck!

Simon

Pieroh,
both the schematics shown for inverting and non-inverting are poor. I would not build in either of those arrangements.
Re-design the component values to better suit the chip after you have decided whether to go inverting or non-inverting.

 

[blu_glo]

Those schematics (improved quality in 2nd posting) are from the datasheet and are what the board is based upon. I can attest to having build 2 of these PCBs (and have 4 more) and so far (3 yrs of intermittant, but often, use) have had no problem with them. There were no signs of oscillation and they ran coolish untill I really loaded them with 4 ohms, which is what I expect. They were still however thermally stable at elevated temperature.

They were both fitted on a single heatsink 250mm long x 80mm tall with 50mm long fins, quite a generous surface area, as is best for any chip-amp!

 

[crownnut]

Thank you blu_glo, and even years later I am resurrecting this project!

 

[blu_glo]

WOW DIY Audio has changed since I last logged in Mind you I'm still active on the Facebook page which I assume is related and connected...