Lafayette Phono preamp.

mattjk · 21st November 2004, 07:50 PM

I just purchased a Lafayette tubed phono preamp on ebay. From what I've search here, it seemed to be a copy of the RCA phono circuit.

Is this circuit worth modding (replacing all the old caps, possibley with expensive Jensens)?

Thanks!

analog_sa · 21st November 2004, 08:11 PM

Congrats, looks like something the cat ... ah, nevermind, the stuff i build mostly looks the same. The RCA phono is not my favourite but others seem to like it. If you like the sound a lot as is, then it's probably worth swapping caps, etc. If you really don't like it, no amount of cap-treatment will do much good. IMO only very good topologies justify expensive parts.

good luck

mattjk · 22nd November 2004, 07:15 PM

thanks!

can anyone recommend some circuit mods?

mcs · 22nd November 2004, 09:16 PM

Those caps look a LOT like Suzuki caps - even though they have a different name as far as I can see. You can read more about Suzuki caps here: http://stiftsbogtrykkeriet.dk/~mcs/Sansui_500.html

If they are the same, you should replace them at once - at least the ones that are supposed to block DC. Otherwise you'll kill the tubes.

And those Telefunken tubes are worth saving BTW - don't let bad caps kill them

Best regards,

Mikkel C. Simonsen

fdegrove · 22nd November 2004, 09:29 PM

Hi,

Quote:

can anyone recommend some circuit mods?

Do you happen to have a circuit diagram?

Quote:

Those caps look a LOT like Suzuki caps - even though they have a different name as far as I can see.

The smaller orange coupling caps look like old production Shizuki caps too...
A Lafayette made in the land of the rising sun perhaps?

Cheers,

mattjk · 23rd December 2004, 08:41 PM

Ok, finally got this thing in the mail.

The caps are "King oil caps". They look like the suzukis...

The transformer buzzes something fierce, but the signal sounds fairly quiet.

The tubes look fake to me... long plates but don't have the diamond on the bottom of the tube.

I have no idea if the caps are bad, but the sound of this preamp sounds pretty good. The midrange is a bit harsh, but the highs are superb. The bass is a problem though. There is NO bass. Could be bad tubes I guess, but wouldn't that affect the high frequencies more? or does this point to bad caps?

Any help would be appreciated.

Thanks

resident · 23rd December 2004, 08:56 PM

No bass-bad caps.
If your caps are old replace them immediately!

I can't see your images.Maybe there's a problem with my connection

mattjk · 23rd December 2004, 09:11 PM

thank you for your reply.

OK, I will replace the signal caps.

On the caps, there is a black line on the end of the can, is this the inner foil lead?

Where can I find a replacement power supply cap??? It has 4 posts, 40, 20, and 20 uF at 150wv.

resident · 23rd December 2004, 09:31 PM

It's more important to replace PSU's caps than signal caps.
Maybe signal caps are OK.

Quote:

Where can I find a replacement power supply cap??? It has 4 posts, 40, 20, and 20 uF at 150wv.

A little bit difficult to find exactly the same.But maybe you'll find it with a google search.Try JJ/Tesla caps or F&T caps or LCR caps.
There are more brands out there that I don't remember.

Still, can't see your images.

mattjk · 23rd December 2004, 11:24 PM

I just measured the output RCA's

23volts out of the right channel, and 16volts out of the left channel.

That's bad, right?

21st November 2004, 07:50 PM	#1
mattjk diyAudio Member Join Date: Aug 2004 Location: Huntington Beach, Ca	Lafayette Phono preamp. I just purchased a Lafayette tubed phono preamp on ebay. From what I've search here, it seemed to be a copy of the RCA phono circuit. Is this circuit worth modding (replacing all the old caps, possibley with expensive Jensens)? Thanks!

22nd November 2004, 09:16 PM	#4
mcs diyAudio Member Join Date: Aug 2003 Location: Denmark	Those caps look a LOT like Suzuki caps - even though they have a different name as far as I can see. You can read more about Suzuki caps here: http://stiftsbogtrykkeriet.dk/~mcs/Sansui_500.html If they are the same, you should replace them at once - at least the ones that are supposed to block DC. Otherwise you'll kill the tubes. And those Telefunken tubes are worth saving BTW - don't let bad caps kill them Best regards, Mikkel C. Simonsen __________________ My personal electronics website Remote control kits website

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21st November 2004, 08:11 PM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Congrats, looks like something the cat ... ah, nevermind, the stuff i build mostly looks the same. The RCA phono is not my favourite but others seem to like it. If you like the sound a lot as is, then it's probably worth swapping caps, etc. If you really don't like it, no amount of cap-treatment will do much good. IMO only very good topologies justify expensive parts. good luck

22nd November 2004, 07:15 PM	#3
mattjk diyAudio Member Join Date: Aug 2004 Location: Huntington Beach, Ca	thanks! can anyone recommend some circuit mods?

23rd December 2004, 08:41 PM	#6
mattjk diyAudio Member Join Date: Aug 2004 Location: Huntington Beach, Ca	Ok, finally got this thing in the mail. The caps are "King oil caps". They look like the suzukis... The transformer buzzes something fierce, but the signal sounds fairly quiet. The tubes look fake to me... long plates but don't have the diamond on the bottom of the tube. I have no idea if the caps are bad, but the sound of this preamp sounds pretty good. The midrange is a bit harsh, but the highs are superb. The bass is a problem though. There is NO bass. Could be bad tubes I guess, but wouldn't that affect the high frequencies more? or does this point to bad caps? Any help would be appreciated. Thanks

23rd December 2004, 08:56 PM	#7
resident Account Disabled Join Date: Sep 2004 Location: Earth	No bass-bad caps. If your caps are old replace them immediately! I can't see your images.Maybe there's a problem with my connection

23rd December 2004, 09:11 PM	#8
mattjk diyAudio Member Join Date: Aug 2004 Location: Huntington Beach, Ca	thank you for your reply. OK, I will replace the signal caps. On the caps, there is a black line on the end of the can, is this the inner foil lead? Where can I find a replacement power supply cap??? It has 4 posts, 40, 20, and 20 uF at 150wv.

23rd December 2004, 11:24 PM	#10
mattjk diyAudio Member Join Date: Aug 2004 Location: Huntington Beach, Ca	I just measured the output RCA's 23volts out of the right channel, and 16volts out of the left channel. That's bad, right?