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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:  Geek [ 02 Dec 2017, 14:13 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

I see ".1" clearly ;)

Author:  gofar99 [ 02 Dec 2017, 17:13 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi, The cap shown is a 0.1uf. The value can be adjusted over quite a range. Small values enhance the speed that the regulator can fix output changes. Larger values decrease the speed but make it act more like a capacitor multiplier filter. You can actually go up to 10uf provided you never short out the output side. I will often use a 1.0uf poly there when the load is stable and maxium filtering is wanted like in a phono preamp.

Good listening
Bruce

Author:  coaltrain [ 05 Jan 2018, 14:50 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Here is my completed Forewatt and KT88 Oddwatt amps. Bruce, thanks for the schematics and advice, they sound incredible. The Forewatt really drives the amps, I didn't believe they could sound any better until I hooked the Forewatt up.
Chace

Author:  jazzzman [ 08 Mar 2018, 12:06 ]
Post subject:  IC volume control on ForeWatt Tube SRPP Preamplifier -

I am considering making a forewatt preamp with a remote control for volume and possibly balance. The Muses chip looks like an interesting solution. Academy Audio sells volume control units that include the chip, an encoder for manual adjustment as well as the remote control. The pots on these boards have an input impedance of 20k and output impedance of no greater than 6k. The notes recommend a load in excess of 50k.
If I replace the 100k pot in the schematic with the Academy Audio board, I believe the load on the Muses chip will be too low. Can I insert a resistor in parallel with the Muses’ output (I.e., in parallel with the input to the Forewatt) to increase the input impedance of the Forewatt? If so, would I have to make any other changes in the circuit values?
Thanks for any help anyone can give.
Jazzzman

Author:  gofar99 [ 08 Mar 2018, 14:50 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi, The input impedance of the Forewatt is mostly determined by the 100K pot. If you put a fixed resistor there to ground in place of it you should be fine.

Good listening
Bruce

Author:  gofar99 [ 08 Mar 2018, 14:53 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi coaltrain, the two components are designed to work together and complement each other. Glad you like the sound. I certainly do. They look like nice builds.

Good listening
Bruce

Author:  jazzzman [ 08 Mar 2018, 16:55 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Thank you, Bruce. Is there any reason to choose a particular value or should I just use 100k?

Author:  Xandrell [ 01 Apr 2018, 02:17 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi there...

Would it be possible to use ecc99's instead of thouse ecc802s? I personally think they also look netter :-)

Author:  gofar99 [ 01 Apr 2018, 16:19 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi jazzzman, 100K was the way I designed it. Other values ought to work..but since one resistor is the same cost as another...why change things that work?

Hi Xandrell, It is reasonably close. But ECC802s and all other similar 12AX7 variants are plentiful and often cheap. There is something for everyone. I just happen to like the spiral heaters. It allows for tube rolling, the ECC99s are not so plentiful.

Good listening
Bruce

Author:  jazzzman [ 06 Apr 2018, 19:32 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Thank you, Bruce!

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