DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

ForeWatt Tube SRPP Preamplifier - Support / Update Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=2448
Page 65 of 75

Author:  gofar99 [ 22 Mar 2019, 21:09 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi, What is the transformer you are using? The specifications or drawing of the leads would be helpful.

Good listening
Bruce

Author:  stwh [ 23 Mar 2019, 06:04 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

gofar99 wrote:
Hi, What is the transformer you are using? The specifications or drawing of the leads would be helpful.

Good listening
Bruce


I am using the EdcorXPWR083A. but that I understand. It is the 2014 power supply schematic. The 0v line after the LR8N.

Thanks
Steven

Author:  stwh [ 24 Mar 2019, 06:46 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi all
I think I may have confused things a little. It is not the transformer I am unsure about.
Its the 0v lines on the extreme right of the schematic that I posted above. I am unsure as to where they go.

Thanks
Steven

Author:  ILoveHiFi [ 24 Mar 2019, 14:32 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Those 0v lines are extreme left right after regulator are connected to mains ground via 120r and 0.1uF, they are also connected to ground of unregulated b+. (regulator ground is also connected to Ground of 1uF and 100uF capacitors)

The power transformer is a single 200v ac one and uses a full bridge diode rectifier to get b+. Same as what you'd normally do to rectify a low voltage supply with say +9v ac.

The heater output has a resistor divider via 220k and 100k to create a high voltage refrence to bias up the heater voltage.
The heater circuitry will not become dmanged by this high voltage refrence because its floating.
All this means is that the 6.3v heater voltage developed becomes 100v to 106.3v with respect to b+ supply, if it is biased up to 100v.

This reduces the heater to cathode voltage preventing arcking and helps increase sound quality by reduing heater noise leaked into amp.

Author:  stwh [ 24 Mar 2019, 14:56 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Thanks ILoveHiFi
I think I understand. The 0v lines connect to the ground line with the 1uf and 120R

Thanks
Steven

Author:  poty [ 26 Mar 2019, 03:33 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Just not to confuse further: there are at least two grounds: a safety ground, directly connected to metal parts of the chassis/case and the mains ground, and a signal ground which integrates signal references from all stages, power references (0V) and so on. There were a lot of discussions about that in this and other threads, for example: viewtopic.php?f=9&t=2448&p=52109&hilit=ground#p52109
Main idea: all circuits should be connected to the central point by only one wire (path). The signal ground and the safety ground should be connected together by one of the methods: directly, through RC-network, through a pair of diodes...

Author:  stwh [ 26 Mar 2019, 05:52 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Thanks Poty

I think I have got my head around it now after reading Bruce's article on grounding. The metal chassis will be grounded through the line filter body. The power supply ground through the 120ohm resistor and type X2 cap to the ground pin of the line filter. Input jacks by single wire to the power supply ground and the active circuitry again by single wire to the ground at the input jacks.
I'm hoping I have understood this correctly.

Also if I have 3 pairs of inputs is it ok to ground all 6 plugs in series or should left and right chanels be grounded seperatly or only one side (left or right) be grounded.

Thanks
Steven

Author:  poty [ 26 Mar 2019, 07:37 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

In most cases you can make some kind of "bus" connecting together all the RCAs inputs and outputs ground sides (by a low impedance wire like silver coated or so). You can connect all wires from other circuits to the "bus" in any point.

Author:  stwh [ 26 Mar 2019, 07:44 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

poty wrote:
In most cases you can make some kind of "bus" connecting together all the RCAs inputs and outputs ground sides (by a low impedance wire like silver coated or so). You can connect all wires from other circuits to the "bus" in any point.



That's great. thanks for your help

Steven

Author:  gofar99 [ 26 Mar 2019, 08:49 ]
Post subject:  Re: ForeWatt Tube SRPP Preamplifier - Support / Update Threa

Hi, I use 12ga bare copper wire for a buss between the input and output jacks. I like to attach the circuitry gounds to the middle of it.

Good listening
Bruce

Page 65 of 75 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/