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ForeWatt Tube SRPP Preamplifier - Support / Update Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=2448
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Author:  gofar99 [ 21 Dec 2010, 12:09 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

Hi Josh, You are correct. The key aspect is to make sure you have no alternate paths. I had one some time ago through the CATV shield as it went into the AV system and since it was eventually connected to the signal ground in the FM tuner it made a really round about path. Since then the stereo and TV are completely separate.

Good listening
Bruce

Author:  mazzas [ 21 Dec 2010, 13:57 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

I've prototyped the power section and one channel on my bread board and everything works *great* (thanks, Bruce). One thing I've noticed is how quickly the 7806 gets hot. Has anyone got any advice on what the heat sink requirements are? Does the bridge rectifier also require a heat sink? It gets warm, but because of the rate at which the 7806 heats up I haven't yet run it for more than a couple of minutes... just long enough to test the channel.

Author:  gofar99 [ 21 Dec 2010, 14:34 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

Hi The rectifier is fine without a heatsink, but the 7806 does need one. I use a finned style that is shaped a bit like a "W" and is about 1 inch high and 2 inches wide. larger is of course even better. Use heatsink compound between the heatsink and 7806 for best results.

Good listening
Bruce

Author:  mazzas [ 21 Dec 2010, 17:06 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

As before, thanks for all of your support.
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Author:  mazzas [ 22 Dec 2010, 17:54 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

Have yet to decide what type of enclosure to put this into.
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Author:  gofar99 [ 23 Dec 2010, 17:07 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

Hi I like wood cases over metal chasis. The metal for shielding, the wood because it looks nice. If you use metal be sure to follow the bit about not attaching the shields and signal grounds to the case.

Nice construction.

Good listening
Bruce

Author:  mazzas [ 23 Dec 2010, 17:15 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

I'm with you. I often use metal foil HVAC tape to line the inside of a wood case. Saves me the expense (and constraint) of a Hammond enclosure.

Author:  mazzas [ 23 Dec 2010, 19:32 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

As you can see, I've rigged this up on my bench sans shielded cable... or shielding of any sort. All I can say is that it is already *very* quiet. At first listen the sound is different than a passive attenuator. Very alive. There is excellent separation of the instruments and the resulting sound stage is absolutely wonderful. I'm using a matched pair of JJ's that seems to do the trick. Channels are extremely well balanced. I've not tried anything else, but those stainless steel Russian PIO caps sound just fantastic! Thanks, Bruce. Thanks!!!
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Author:  gofar99 [ 27 Dec 2010, 10:43 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

Hi, I'm glad you like it. It is a deceiptively simple design. Plus the PIOs do a nice job (especially for the price). I have the original one set up so I can swap caps easily and figure the PIOs are hard to beat for the price. I'm using Jantzen Silver Z caps at the present and they are slightly better in the mid-high range. Consideralbly more costly than the surplus K40s. From my own experience (your results may differ) I don't like Spragues, Mallory, Kimble, other Jantzens, Audiophiler MKP, Dayton as well. Auricaps are fine though. Easy to do cap rolling in this design.

Good listening
Bruce

Author:  mazzas [ 27 Dec 2010, 12:24 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Thread

I agree. I ended up paying a fair amount for the PIO caps between the cost and the shipping from Soviet Union. So I ordered way more than I needed. If anyone would like a pair, I'm happy to share.

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