Saurav
Senior HTF Member
- Joined
- Feb 15, 2001
- Messages
- 2,174
Hi,
For sale is my Bottlehead Foreplay tube preamp. This is fairly extensively tweaked and upgraded from stock. I'll describe the changes I've made, please visit www.bottlehead.com if you want more information about what these changes mean.
Upgrades/Mods/Extras:
Cosmetics/Finish
The wood base has been stained with Tung oil. The top plate has a pretty interesting finish - I spray-painted it with purple metallic paint, put it out to dry, and it rained. So, the final finish turned out a little bubbly, and I actually liked the effect quite a bit:
Miscellaneous
Other stuff you need to know:
* This is version 2 of the preamp, with the 6.3V filaments.
* The separate transformer powering the filaments means that this preamp needs 2 power outlets.
* The power switch only controls the original B+ transformer. This means that the wallwart filament transformer needs to be connected to a switched outlet on your power strip, or else the tubes will glow all the time, even with the preamp switched off. A side benefit of this is that it avoids cathode stripping - you can turn on the filament supply, wait till the heaters are glowing, and then turn on the B+ supply. This will significantly lengthen the life of the tubes.
* Noise - I haven't noticed any additional 60Hz hum when the Foreplay is turned on versus running my tube amps by themselves. There is a little hiss since I added the C4S (due to the increased gain), which I believe is just 'tube rush' and should go away with quieter/better tubes. With my amps (500mV input sensitivity) and speakers (88dB sensitive), I can hear the hiss about a foot away from the speakers, it's silent at my listening position (about 8' away). I had modded my amps to change the input sensitivity to 1V, and that cut the hiss dramatically.
* I can remove the extra resistors on input 3 before I ship this if you want me to.
* My soldering skills aren't exactly professional, but I think this is a pretty clean job overall. My dinky PC camera has decided to stop working, so I can't take pictures of the inside (the picture posted above was taken months ago). The last time I was 'under the hood' was several months ago, so there aren't any recent untested changes that are about to fail.
* I will guarantee that this preamp will make music when you receive it. You realize that it may have a different noise floor in your system, and I won't take it back because your equipment creates a ground loop that makes it hum too much, or your amps/speakers' sensitivity makes the hiss too loud, or similar reasons. The Foreplay works best with amps having input sensitivity of 1V or higher.
* If you plan to make any changes to this, I'll be most willing to help you out. However, if you break something, that's obviously not my responsibility. If you don't know what you're doing and hurt yourself or your equipment, that's not my responsibility either.
* My reason for selling - I've decided to try out passive linestages, and I can't afford to have 2-3 preamps sitting around. I hope I don't regret selling this.
Price:
$350 + S/H o.b.o.
This is pretty much my materials cost for all the stuff that's in there. Feel free to email me at [email protected] with any questions. If you're interested in buying this, I would encourage you to ask all your questions up-front. I can provide my eBay user ID for anyone interested in checking my feedback.
Thanks for looking.
Saurav
For sale is my Bottlehead Foreplay tube preamp. This is fairly extensively tweaked and upgraded from stock. I'll describe the changes I've made, please visit www.bottlehead.com if you want more information about what these changes mean.
Upgrades/Mods/Extras:
- Gold-plated RCA connectors
Sweet Whispers -20dB to -50dB stepped attenuator with shunt mod
Anticipation Constant Current Source (C4S)
Matched pair of JJ/Tesla 12AU7s
North Creek Zen 4.7uF coupling caps
Custom Star Ground, based on schematic on VoltSecond's page and some other ideas
DC filament power supply using separate 800mA wallwart/transformer
RF ferrite clamp on the above filament power supply
Modified version of VoltSecond's filament snubber
Reverse Recovery Spike Filter (RRSF, aka 'HV Snubber')
Extra 100K resistors on input 3 to reduce its signal level (approximately 3dB)
Spare tubes - I bought a whole stash of 12AU7s a while ago, those are included. There's a pair of Tung-Sols in there, and miscellaneous RCA/GE/Westinghouse, I think a total of around 20 tubes or more.
Cosmetics/Finish
The wood base has been stained with Tung oil. The top plate has a pretty interesting finish - I spray-painted it with purple metallic paint, put it out to dry, and it rained. So, the final finish turned out a little bubbly, and I actually liked the effect quite a bit:
Miscellaneous
Other stuff you need to know:
* This is version 2 of the preamp, with the 6.3V filaments.
* The separate transformer powering the filaments means that this preamp needs 2 power outlets.
* The power switch only controls the original B+ transformer. This means that the wallwart filament transformer needs to be connected to a switched outlet on your power strip, or else the tubes will glow all the time, even with the preamp switched off. A side benefit of this is that it avoids cathode stripping - you can turn on the filament supply, wait till the heaters are glowing, and then turn on the B+ supply. This will significantly lengthen the life of the tubes.
* Noise - I haven't noticed any additional 60Hz hum when the Foreplay is turned on versus running my tube amps by themselves. There is a little hiss since I added the C4S (due to the increased gain), which I believe is just 'tube rush' and should go away with quieter/better tubes. With my amps (500mV input sensitivity) and speakers (88dB sensitive), I can hear the hiss about a foot away from the speakers, it's silent at my listening position (about 8' away). I had modded my amps to change the input sensitivity to 1V, and that cut the hiss dramatically.
* I can remove the extra resistors on input 3 before I ship this if you want me to.
* My soldering skills aren't exactly professional, but I think this is a pretty clean job overall. My dinky PC camera has decided to stop working, so I can't take pictures of the inside (the picture posted above was taken months ago). The last time I was 'under the hood' was several months ago, so there aren't any recent untested changes that are about to fail.
* I will guarantee that this preamp will make music when you receive it. You realize that it may have a different noise floor in your system, and I won't take it back because your equipment creates a ground loop that makes it hum too much, or your amps/speakers' sensitivity makes the hiss too loud, or similar reasons. The Foreplay works best with amps having input sensitivity of 1V or higher.
* If you plan to make any changes to this, I'll be most willing to help you out. However, if you break something, that's obviously not my responsibility. If you don't know what you're doing and hurt yourself or your equipment, that's not my responsibility either.
* My reason for selling - I've decided to try out passive linestages, and I can't afford to have 2-3 preamps sitting around. I hope I don't regret selling this.
Price:
$350 + S/H o.b.o.
This is pretty much my materials cost for all the stuff that's in there. Feel free to email me at [email protected] with any questions. If you're interested in buying this, I would encourage you to ask all your questions up-front. I can provide my eBay user ID for anyone interested in checking my feedback.
Thanks for looking.
Saurav
