Doug Self Preamp from Linear Audio #5

AMV8 · 2015-10-10 7:46 am

Hi
Please add me for 2no kits.
Many thanks!

jan.didden · 2015-10-10 8:12 am

MadInventor said:
Carl

My redesign for your project is attached, the problem, mosfet dissipation of over 5 watts is the issue with 1U enclosure. Two options heat sink height of 1" 4.7 C/W, I would run no more than 5 watts, with 1.5" heat sink 3.7 C/W, will probably run out of clearance. The output adjustment for the attached is 14 to 16, to have a range of 12 to 17 at 1A, and stay with 1U case will require builders to choose xfmrs accordingly.

Mad

Neat with the 317 ref. I was wondering, would you have start-up problems if the ref circuitry would be powered from the output rather than the input? It would certainly be even quieter.

Jan

MadInventor · 2015-10-10 7:22 pm

jan.didden said:
Neat with the 317 ref. I was wondering, would you have start-up problems if the ref circuitry would be powered from the output rather than the input? It would certainly be even quieter.

Jan

Hello Jan,

If I moved the 317 to the load side, I would probably use a divider to ground to bias the gate to insure the pass mosfet would conduct on start up. If I also moved the opamp, well then I would have something like the super regulator

, but then this opamp is a lttle slow for that. Maybe I should call this "not that costly of a PS regulator".

Mad

Carl_Huff · 2015-10-12 11:07 pm

Great!

Let's start a group buy list. I'll leave it up until November 1st. Expect delivery to be mid to late November

georgebrooke - 1kit - PAID
Halauhula - 1 kit - PAID
hfxrzw - 2 kits
PJN - 1 kit
kiroje - 1 kit
still4given - 1kit - PAID
GlennW - 1kit
erik777 - 1 kit
arthur - 1 kit
zrxshack - 1 kit
rock12 - 1 kit
canute - 1 kit
Somakmaitra - 1 kit - PAID
MosfetDemon - 1 kit
mik000000 - 1 kit
AMV8 - 2 kits

If you have asked to be added to the list but don't see your name be sure to let me know!

mik000000 · 2015-10-13 7:18 pm

Carl_Huff said:
How many inputs are you looking for George?

at the risk of overcomplicating...

i would like to see 3 or 4 inputs, possibly 1 with a 3.5mm input on the front panel? Also an on/off switch and LED

Carl_Huff · 2015-10-14 2:29 am

mik000000 said:
... i would like to see 3 or 4 inputs, possibly 1 with a 3.5mm input on the front panel? Also an on/off switch and LED

An ON/OFF switch and power state LED would be addressed by the power supply that you select. There are several good examples here on diyAudio.

I will be following up this project with one that replaces the IO PCB of this project adding more IO. The new board will be a simple swap. The initial goal of this project was to build the Doug Self design as published in Linear Audio.

Halauhula · 2015-10-14 3:23 am

Additional Requests

Carl_Huff said:
I will be following up this project with one that replaces the IO PCB of this project adding more IO. The new board will be a simple swap. The initial goal of this project was to build the Doug Self design as published in Linear Audio.

Well, if everyone is sending suggestions, I should add my own:

1. PCB connectors/terminals to allow plug-in of cables from volume, balance, and tome control posts. That way, higher quality posts can be mounted off-board, and plugged into the connectors on the PCB. Good quality connectors exist, and a touch of Cramolin would help ensure corrosion-free connections.

2. PCB connectors/terminals for power and power ground

Carl_Huff · 2015-10-14 3:57 am

Halauhula said:
Well, if everyone is sending suggestions, I should add my own:

1. PCB connectors/terminals to allow plug-in of cables from volume, balance, and tome control posts. That way, higher quality posts can be mounted off-board, and plugged into the connectors on the PCB. Good quality connectors exist, and a touch of Cramolin would help ensure corrosion-free connections.

2. PCB connectors/terminals for power and power ground

#1) The pot connections are thru plate thru PCB and lend themselves to be extended with hard soldered wire. I am very slow to add connectors. In my humble opinion (discount at will) the best connections are always made hard wired unless of course you are tying together circuit boards.

#2) There is already a Phoenix/Euro style connector for power at the upper right corner of the PCB as pictured. I simply chose to hard wire the prototype for convenience.

Halauhula · 2015-10-14 5:25 am

Carl_Huff said:
#1) The pot connections are thru plate thru PCB and lend themselves to be extended with hard soldered wire. I am very slow to add connectors. In my humble opinion (discount at will) the best connections are always made hard wired unless of course you are tying together circuit boards.

#2) There is already a Phoenix/Euro style connector for power at the upper right corner of the PCB as pictured. I simply chose to hard wire the prototype for convenience.

#1: Yes, you are correct. I'm going more for the convenience factor and the reduction of wiring errors due to my advanced age.

#2: Ahhhhhh.

DouglasSelf · 2015-10-14 1:30 pm

Hello All

It's nice to see interest in the preamp. I wish this project well.

The Third edition of the book Self On Audio will be out in a couple of weeks, and it contains new & extra information on the preamp, as well as a reproduction of the original LA article.

A couple of points before you get too carried away with PSU design:

Firstly, the original preamp runs off +/-17V, not +/-15V, to maximise headroom. It works fine off +/-15V but will not give the spec'd output level.

Secondly, all the development work and measuring was done with a 30-year-old bench PSU. A fancy low-noise PSU is really not necessary so long as you take the usual precautions about keeping rail noise out of the signal ground, ie be careful with the decoupling cap grounding.

This preamplifier is MRP13 in my numbering system. At the time of writing this is the most recent preamp design I have published.

Carl_Huff · 2015-10-14 5:10 pm

DouglasSelf said:
... Firstly, the original preamp runs off +/-17V, not +/-15V, to maximise headroom. It works fine off +/-15V but will not give the spec'd output level.

Secondly, all the development work and measuring was done with a 30-year-old bench PSU. A fancy low-noise PSU is really not necessary so long as you take the usual precautions about keeping rail noise out of the signal ground, ie be careful with the decoupling cap grounding....

Thanks Doug for checking in and offering this guidance. I will be looking for your 'Third edition of the book Self On Audio'

Carl_Huff · 2015-10-15 3:08 am

Great!

Let's start a group buy list. I'll leave it up until November 1st. Expect delivery to be mid to late November

georgebrooke - 1kit - PAID
Halauhula - 1 kit - PAID
jan.didden - 1 kit - PAID
hfxrzw - 2 kits
PJN - 1 kit
kiroje - 1 kit
still4given - 1kit - PAID
GlennW - 1kit
erik777 - 1 kit
arthur - 1 kit
zrxshack - 1 kit
rock12 - 1 kit
canute - 1 kit
Somakmaitra - 1 kit - PAID
MosfetDemon - 1 kit
mik000000 - 1 kit
AMV8 - 2 kits
arthur - 2 kits - PAID

If you have asked to be added to the list but don't see your name be sure to let me know!

Badge · 2015-10-15 3:45 am

please add me to the list for one Kit. Thanks

Carl_Huff · 2015-10-15 4:03 am

Great!

Let's start a group buy list. I'll leave it up until November 1st. Expect delivery to be mid to late November

georgebrooke - 1kit - PAID
Halauhula - 1 kit - PAID
jan.didden - 1 kit - PAID
hfxrzw - 2 kits
PJN - 1 kit
kiroje - 1 kit
still4given - 1kit - PAID
GlennW - 1kit
erik777 - 1 kit
arthur - 1 kit
zrxshack - 1 kit
rock12 - 1 kit
canute - 1 kit
Somakmaitra - 1 kit - PAID
MosfetDemon - 1 kit
mik000000 - 1 kit
AMV8 - 2 kits
arthur - 2 kits - PAID
Badge - 1 kit

If you have asked to be added to the list but don't see your name be sure to let me know!

AMPMAN · 2015-10-15 4:23 am

self preamp

carl put me on your list thanks AMPMAN

Carl_Huff · 2015-10-15 4:26 am

Great!

Let's start a group buy list. I'll leave it up until November 1st. Expect delivery to be mid to late November

georgebrooke - 1kit - PAID
Halauhula - 1 kit - PAID
jan.didden - 1 kit - PAID
hfxrzw - 2 kits
PJN - 1 kit
kiroje - 1 kit
still4given - 1kit - PAID
GlennW - 1kit
erik777 - 1 kit
arthur - 1 kit
zrxshack - 1 kit
rock12 - 1 kit
canute - 1 kit
Somakmaitra - 1 kit - PAID
MosfetDemon - 1 kit
mik000000 - 1 kit
AMV8 - 2 kits
arthur - 2 kits - PAID
Badge - 1 kit
AMPMAN - 1 kit

If you have asked to be added to the list but don't see your name be sure to let me know!

arthur · 2015-10-15 4:49 am

Hi Carl,

Please Amend : Arthur ....2kits

Carl_Huff · 2015-10-15 5:09 am

arthur said:
Hi Carl,

Please Amend : Arthur ....2kits

Yup, you are already there third name from the bottom!

orjan · 2015-10-16 9:37 am

Hi,

one kit for me, please.

/örjan

DouglasSelf · 2015-10-16 12:54 pm

Carl_Huff said:
This preamplifier draws a bit of current, upwards of 650 milliamps steady state. It deserves to be fed by a quality & quiet power supply.

Hi Carl

I don't understand your figure of 650 mA. The original design had 14 LM4562s. The max quiescent current from the rails is 12 mA per dual package.
I make that 168 mA.

You have 15 LM4562s which is only 180 mA total

Am I missing something here ???

PS: I am sure that ordinary 78xx and 79xx IC regulators will work fine. The Small Signal book shows how to get 17V from 15V regs.

Doug Self Preamp from Linear Audio #5

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