The high octane phono preamp

[zman01]

only transistors are obsolete and you need to use some equivalent available. Read this thread entirely

Sent from my EVA-L09 using Tapatalk

Aha - that is a key piece of information.

Have started reading, but any inputs welcome!

 

[Marra]

I will take a pair of boards please.

My mistake one board thanks.

 

[jan.didden]

Bom was already public with farnell part numbers, only transistors are obsolete and you need to use some equivalent available. Read this thread entirely

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The original article is here:

https://linearaudio.net/article-detail/2159

Jan

 

[billshurv]

Jan: Silly question possibly, but will the silentswitcher handle being run as 0 and 30v rather than +/-15 for those of us lured to battery powered stuff thanks to you?

 

[zman01]

I recently became a father so free time became a very rare collectible

Congratulations!

I will post here when I have the boards in my hands

Thanks for taking the time and effort to do this.

One PCB for me please.

 

[kcdonahue]

Would anyone be willing to forward me a copy of the BOM that was hosted on Linear Audio as it is no longer available or I am just looking in the wrong place. I purchased the article when I bought the board but I do not have a copy of the bom.

I bought my boards with the initial run of the smaller green boards without the mounting holes and forgot I had it laying until today.

Thanks,

KC

 

[noviygera]

Final check...

Can someone verify my (old revision) Octane board before the first power up?

1. Is lm4040 in place of LED, in correct direction? Do I need to change anything else?
2. Is it ok to leave out CP1 or install with changes?



thanks,
Herman

 

[jan.didden]

Jan: Silly question possibly, but will the silentswitcher handle being run as 0 and 30v rather than +/-15 for those of us lured to battery powered stuff thanks to you?

Yes it will but the mid-tap (between the +/-15V) is connected to the gnd of the 6.5/5/3.3V output.
So if you use it for 30V you cannot use the 6.5/5/3.3V output at the same time.

Jan

 

[jan.didden]

Would anyone be willing to forward me a copy of the BOM that was hosted on Linear Audio as it is no longer available or I am just looking in the wrong place. I purchased the article when I bought the board but I do not have a copy of the bom.

I bought my boards with the initial run of the smaller green boards without the mounting holes and forgot I had it laying until today.

Thanks,

KC

I don't think I hosted the BoM, at least I don't remember I did.

Doesn't the article spell out a parts list?

Edit: I uploaded Hannes' building notes and parts list here: https://linearaudio.net/downloads
Note that the Gerbers are no longer available as far as I know.

Jan

 

[kcdonahue]

Huge thanks Jan!

My mistake in calling it a BOM. It was indeed his build notes.

KC

 

[jan.didden]

Huge thanks Jan!

My mistake in calling it a BOM. It was indeed his build notes.

KC

My bad. It got dropped on a web migration.

 

[Freecrowder]

I would be interested in purchasing a single board. How do I go about that?

 

[jan.didden]

I think Hannes will post when he has the boards:

http://www.diyaudio.com/forums/analogue-source/242387-high-octane-phono-preamp-45.html#post5100874

Jan

 

[billshurv]

Yes it will but the mid-tap (between the +/-15V) is connected to the gnd of the 6.5/5/3.3V output.
So if you use it for 30V you cannot use the 6.5/5/3.3V output at the same time.

Jan

Cool. in that case I may just have to add another phono to my list

 

[zman01]

Edit: I uploaded Hannes' building notes and parts list here: https://linearaudio.net/downloads
Note that the Gerbers are no longer available as far as I know.

Jan

Jan,

Many thanks for sharing.

However looks like some parts are missing (at least to me ) - but noob here, so appreciate the guidance...

The parts list does not mention part numbers like C101, C111 while the board seems to have them - I am attaching a build pic from diyA member msdin (hope that is ok) for your reference:

http://www.diyaudio.com/forums/analogue-source/242387-high-octane-phono-preamp-32.html#post4622575

Same I see for the LCR FSCEX 1% RIAA caps - 3 are listed, but 6 are present on the board.

Other parts like qty for Opamp and FET seem to be listed accurately.

Which part of the bill of materials are to be considered as "parts required for a single channel" and to be multiplied by 2?

 

[noviygera]

Post #467. CP1 still needed?

 

[Destroyer OS]

I'm in for some boards.

 

[h_a]

Hi everyone,

it's sooo great to see there is still so much interest in my little phono pre! Especially at DIYAudio where so many great phono designs are made available!

There are a few questions about the amp, please give the high octane wiki a chance to help with some questions, you'll find it here

The high octane phono preamp

Post #467. CP1 still needed?

Regarding CP1, you can simply leave it out if you want to be on the safest side (works in all cases).

If you have one of the green boards (from the 1st run) then you can alternatively rewire one leg of CP1 to make it work, see also the Wiki:

Voltage regulator: do NOT insert CP1 (it will damage the opamp) and DO NOT ground its second leg (which is connected to the opamp input); the schematic shows correctly how CP1 should be connected (or leave it out simply)

The red boards should have this issue fixed and can use CP1 without modifications if I'm not mistaken....

EDIT: just checked my old posts and yep - for the red boards CP1 can be used as it is shown on the board,

http://www.diyaudio.com/forums/analogue-source/242387-high-octane-phono-preamp-12.html#post4495991

There are a few changes to the previous board, e.g. to make mounting of the board easier (it has now mounting holes) as well as it will fit into a normal Hammond 1455N1601 enclosure.

Then it also corrects a few warts and bugs of the previous version (C6/C106 are gone, CP1 is fixed and goes now to ground).

Oh - and of course the new board is RED

 

[zman01]

h_a,

Good to see you back on this thread again.

Was a HFE range for the 2SC2547 recommended? Do they all need to be matched or within an acceptable range?

 

[tommydoan84]

hi Hannes,

I've skimmed through the thread and there are quite a bit of the mods that some of the members did to improve the sound quality of the phonostage and to get the voltage regulator to be more stable such as #1, #3 and #4 below. Are you also taking these mods into account in this new batch of red boards ? or at least make some place holders so we can solder in the new mod component ?

Let us know,
Thanks,
Tom

I’ve built and modified it with the three modifications and can only say that it improved it, with the sound as a whole became more natural with vocals and instrument have a life like quality.

1.
C7, C107, change to 220uF and add 1K between SENSEV and C7, C107, as per post #314.

This modification improved the PSRR of the first transistor with a reduction in hum and I found it had a small effect on how it sounded.
As I did not have any real 2SC2547A I used a BC550C which was fair noisy, I found the bass was muddled and the treble had an etched quality.
The best transistor I try was a BC337-40 noise was lower and sound wise was very well balanced.

2.
R13, R113, change to 700K, as per post #317f.
R15, R115, change to 820R, as per post #317f.

The original riaa network was tested with an inverse riaa and a 20Hz -20kHz signal, with the output voltage read off a valve voltmeter and viewed on a scope.
I check the original riaa network using LTspice and this confirmed a very similar plot using the voltage values of the meter.

I made this change after listening to the preamp as I could hear the drop around 100Hz which had a dry sounded boxy.
The rising in the treble was also noticeable my first though was I hadn't set the input capacitance correctly for the Ortofon 2M Blue.

3.
The Two Diodes LED Lift modification, as per post #334 and #338.
4.
Alternatively, replace the LED ref with a 2-pin 5V ref, as per post #330.

Mods three and four achieve the same results.

This modifications came about with regards to the shunt psu when someone's preamp was oscillating and 'rjm' look into the problem.
The problem turn out to be the op-amp was not suitable for rail-to-rail operations, as it was marginal stable unless the components were carefully selected so rjm proposed lifting the reference voltage.

Sound wise you will have nothing to loss if you try all a three modifications.

This is just my thoughs sound wise the High Octane RIAA phonostage is very good.

Sharif.