Bottlehead Foreplay

00p225

Foreplay hum can be tough to find. Are you getting 60hz humm or buzz? It can be as simple as another component in your house like a fish tank light or pump (don't even ask) or the filament heaters in your FP picking up hum due to microphonic tubes (5963's) don't ask............ if you still can't find the culprit you can do the high voltage snubber, the tube filament snubber, or go the easy route like I did and elimenate the stock FP 6v heater supply and just use a Rat Shack 6V DC 800ma power adapter and run dc to your tube heater filaments and no more noise, dead quiet and black background. This is usually the main cause for Foreplay humm/buzz. The power supply only costs $17 at rat shack. Have fun with that FP!!

00p225

Here's a pic of my homebrew preamp using 12au7 tubes and a nice hefty hammond transformer, kimber coupling caps, alps volume pot etc. My brother built his homebrew about a month before we built mine, very similar to the bottlehead foreplay. Different components of course, but the same basic circuits. Really fun stuff to tweak and play with, and of course the sound is phenominal for the price. Sorry for the pic, just bought that digital camera a couple days before shooting this pic..........

gidrah

That looks like a mighty fine preamp. Congrats!

gatemplin

Originally posted by gidrah
That looks like a mighty fine preamp. Congrats!

Agreed, mighty fine. Wish I could build something like that.

dcarlson

Thanks, it's not as difficult as you may think.

I'd say the hum is more of a buzz and it happens solely when hooked up to the Dynaco tube amp. The gain on the Foreplay seems rather high so I wonder if that's the problem?

00p225

Is the buzz volume dependant, or does it always stay at the same level? Mine was noticable through the tweeters, and I thought it was switching noise from the diodes, but it just turned out to be transformer noise making it through the heater filaments. I sometimes run the FP into my MC2100 which has variable gain on the inputs. I ran the gain about halfway, and still had plenty of volume with the hair trigger FP volume pot, but having the gain halfway opened helped drop the noise floor. You could also try reversing your power plugs on the dynaco and FP.

BTW, your FP is looking great. It took at least 20 hours for the coupling caps etc to settle in on mine. If you think it sounds good now, just wait. For tubes, did you get the HP/RCA 5963's? They are very noisey, a good tube dampner is automotive heater hose cut and slipped over the tube. For tubes in mine, I have tried the following.

E German RFT's (Thanks Organ!) - Smooth with good high end extension, but light on bass below 45hz

Baldwin GE? 12AU7's - Magical midrange timbre, nice bass and rolled off highs. Great for foward speakers.

1960s RCA 5963 greyplates with halo getters. Also nice, a bit bass shy and very foward upper midrange and highs again a nice tube but very forward.

1959 Vintage Mullard 12AU7's - Nice bass extension, BIG sounding midrange vocals and soundstage, smooth highs, but not too extended. These would be nice with bright forward speakers.

1950's vintage RCA 12AU7/5963 Blackplates with D shaped getter - Awesome tube, great bass, midrange, and airy highs without being harsh. My favorite so far, but still rolling!

dcarlson

I only have the tubes that came with the kit and the writting is pretty much warn out. I can only make out electr....

As for the hum. It's stays at the same level and isn't tied to the volume.

I currently have the FP running between my CD player and my integrated. I have the volume on my integrated set at 10:30 and the noise floor is black.