Relay input buffer resistors.

[Dave the bass]

I'm building a simple passive input switching and volume control unit I can switch between sources without having to swap RCA plugs around on my DIY projects. All my DIY amps have just single line level L+R i/p's

I'm using the nice little WD i/p relay switching board as the heart of it, the output of the board will feed whatever DIY power amp is in favour and the tape-out will feed my headphone amp.

Now, when I built the WD88 I noticed there's 2 off 1Kohm resistors that are described as 'tape buffer resistors' (RR1 + RR2). My question is....

If I'm driving a headphone amp from this o/p do I really need them? And also what do they do? I think I asked Dr John at a show once but I can't remember what the answer was, I'll blame it on the Ale

See, I'm still about and building, bet you all thought I was having a nap!

All the best

DTB

[Audiognome]

Originally Posted by Dave the bass

See, I'm still about and building, bet you all thought I was having a nap!

Yes - what's happened to Komrade DHTski? He stopped reporting in some time ago. I was beginning to think he might have defected!

[Dave the bass]

Originally Posted by Audiognome

Yes - what's happened to Komrade DHTski? He stopped reporting in some time ago. I was beginning to think he might have defected!

No need to worry Nigel, DHTski's still with us, he's all completed and pumping out beautiful moosics everyday here in the workshop.Sorry, I'll put some piccies up soon.

6EM7 is currently living under our bed untill I finish the source switcher project which is also including a switch so Julie can power up my DIY amps without fear electrocution. I've also incorporated a small front panel switch that switches a 10A 240V relay that'll power everything up at once. She was getting a bit confused with the Phono-pre and seperate power amp PSU's and wasn't confident switching over leads from different sources either.

Tcht, girls huh! She can handle vinyl and WD88 so she's not all bad so thats what I'm back to right now at home

DTB

[John Caswell]

Hi all
The tape buffer resistors are there to effectively "stand off/isolate" the main output if you accidentally put a s/c on the tape output.
If you are feeding a high impedance input from them ie Headphone II/III or tape deck etc, they will have negligible effect on anything, they are really for safety's sake. Leave them in or remove them it is your choice.

John - Dr John

[Audiognome]

Originally Posted by Dave the bass

No need to worry Nigel, DHTski's still with us, he's all completed and pumping out beautiful moosics everyday here in the workshop.Sorry, I'll put some piccies up soon.

Good, it'll be nice to see some amp pics - it's all gone a bit quiet on that front recently (no pun intended, ouch!)

I've got a load of projects I want to start myself at the moment, but no money, 'cos one of my cats rather inconsiderately broke his leg. He's encased in scaffolding at the moment - you should see the vet's bills

Nigel

[Dave the bass]

Many thanks for the info John, I'll leave them in for now then. The Headphone amp (a Chinese Little Dot 11) runs happily from WD88's Tape Out loop.

Cheers again for your help,

DTB

[Dave the bass]

Well I dunneded it, the source switcher/volume control is finished. It's been my lunchtime project for the past few weeks, doesn't look much but it enables my GF to switch between sources on my DIY SE amps without fear of electrocution with the added bonus that she doesn't have to plug IEC mains leads into in-line sockets to power (via a 10A mains relay) the beasties up now, hence the 'AMP-POWER' switch at the front which supply mains to all the kit in my HiFi cabinet.

WD's little relay i/p board keeps the switching simple, nice little useful project methinks. I've rearranged the switching so the 'mute' function is next to the 'Phono' position...this is so that should any fluff 'n' stuff require removing from the stylus I don't have to play around with the volume control to avoid that 'sawing of the stylus' rumble and racket experienced when trying to remove the crud. Flick the switch to 'Mute'...remove gunge...flick back to 'Phono' and we're back in business with no speaker damaging sawing of the stylus sounds.

Where do I collect my Nobel Prize from?!!!









DTB

[Shian7]

You collect your prize from the same place that gives you some proper labels...instead of the monkey scrawl you have on the case at the moment! :p

Ha Ha !!!

[Dave the bass]

Originally Posted by Shian7

You collect your prize from the same place that gives you some proper labels...instead of the monkey scrawl you have on the case at the moment! :p

Ha Ha !!!

You leave my Monkey out of this you brute, he's a talented chap



DTB (and Bubbles)

[Shian7]

The peanuts are in the post!