Hi All,
Last Christmas I bought one of the boards for my son, and of course one for myself as well
Finally got around to finishing this build. My son's board is done as well, but I'll let him make his own box.
The board is built pretty much to Hannes's original specs, but using C1845's for Q1-3. Most of the components I sourced from my local surplus shop.
Threw together the chassis from some leftover acacia flooring I had, and a piece of aluminum. Lined the inside of the box with aluminum tape for shielding, and since the wall wart I found ($3) had a ground terminal, I added a lug for the turntable ground wire.
I'm not the most sophisticated of listeners, but I'm very pleased with the sound, even in spite the left channel hum from my turntable (will attempt to fix it the next couple of days). Won't try to get too descriptive, because frankly I lack that vocabulary; let's just say it sounds natural and satisfying...
Turntable is a Pioneer 530 with a Shure M92 cartridge. Preamp is a Bottlehead Smash. Amps are Amp Camp Amp monoblocks. Speakers are vintage BeoVox S42-2s, original except for caps.
Pics below for those interested.
Cheers!
Last Christmas I bought one of the boards for my son, and of course one for myself as well
Finally got around to finishing this build. My son's board is done as well, but I'll let him make his own box.
The board is built pretty much to Hannes's original specs, but using C1845's for Q1-3. Most of the components I sourced from my local surplus shop.
Threw together the chassis from some leftover acacia flooring I had, and a piece of aluminum. Lined the inside of the box with aluminum tape for shielding, and since the wall wart I found ($3
) had a ground terminal, I added a lug for the turntable ground wire. I'm not the most sophisticated of listeners, but I'm very pleased with the sound, even in spite the left channel hum from my turntable (will attempt to fix it the next couple of days). Won't try to get too descriptive, because frankly I lack that vocabulary; let's just say it sounds natural and satisfying...
Turntable is a Pioneer 530 with a Shure M92 cartridge. Preamp is a Bottlehead Smash. Amps are Amp Camp Amp monoblocks. Speakers are vintage BeoVox S42-2s, original except for caps.
Pics below for those interested.
Cheers!
Attachments
I've tried several MM's and a low out ceramic cartridge.
Ortofon 2M blue, Linn K9 and Technics UPC205 mk3 the Phillips GP390 ceramic cartridge was the best.
http://www.diyaudio.com/forums/analogue-source/242387-high-octane-phono-preamp-32.html#post4622670
The regulator works by 'amplifying' the ref voltage. With a LED that ref voltage is low and not accurately defined, so often you need to tweak a resistor value to get to the exact 40V output.
The 4040 has two advantages here: you can get it in various values, for instance a 10V version would be nice.
Secondly you can get them in 1% to or even less tolerance so you get close to the 40V with no tweaking.
Of course if you switch from a LED to a 4040 you need to one-time recalculate the output divider resistors at the opamp input; with the required 40V out, the divider should give the same voltage at its mid-point as the reference.
Jan
The 4040 has two advantages here: you can get it in various values, for instance a 10V version would be nice.
Secondly you can get them in 1% to or even less tolerance so you get close to the 40V with no tweaking.
Of course if you switch from a LED to a 4040 you need to one-time recalculate the output divider resistors at the opamp input; with the required 40V out, the divider should give the same voltage at its mid-point as the reference.
Jan
Jan, thank you for the explanation.
which resistors are the output divider resistors?
For the 5 volt ref lm4040, will I need to change values of these?
Instructions say "LED should have a forward voltage of about 1.6 V"...
Do you use the 47ohm resistor on output RCA jacks? I looked at some build photos, but did not see resistors there.
thanks,
Herman
which resistors are the output divider resistors?
For the 5 volt ref lm4040, will I need to change values of these?
Instructions say "LED should have a forward voltage of about 1.6 V"...
Do you use the 47ohm resistor on output RCA jacks? I looked at some build photos, but did not see resistors there.
thanks,
Herman
The 47 ohms are not on he schematic I think, I placed them on the output RCA.
The output divider divides the power supply output down to the same voltage as the ref voltage and connects to the opamp input, the other input than the one the ref is connected to..
The key thing to remember is that the opamp 'amplifies' the ref voltage. And in operation, both inputs will be at the same voltage.
Jan
Jan, thanks for being patient, I'm just learning this.
Looks to me as if RP2 and RP3 are output dividers because they go to opamp input (other input from where LED connects)
original values when using LED 1.6v:
RP2=25K5
RP3=1K
How do I re-calculate both values when using 5v ref lm4040?
Please correct if I am wrong somewhere.
thanks,
Herman
Looks to me as if RP2 and RP3 are output dividers because they go to opamp input (other input from where LED connects)
original values when using LED 1.6v:
RP2=25K5
RP3=1K
How do I re-calculate both values when using 5v ref lm4040?
Please correct if I am wrong somewhere.
thanks,
Herman
Yes.
The idea is that when all is right, the two inputs of the opamp are the same (save for a few mV).
So one has the reference, in your case 5V. Thus, the other, the midpoint of the two resistors, also must be 5V. The top end is the wanted 40V.
Lets's pick a current through the two resistors of 1mA. This is a bit arbitrary; not too much because it wastes power, not too little, or the (small) current into the opamp input can upset things.
So we stay with 1mA. The bottom resistor has 5V across it, right? With 1mA, that makes it 5k. 4.99k would be dandy ;-)
The top resistor has 40-5=35V across it. With 1mA, that would be 35k. That's not a standard value, but you now know how to wiggle the resistor values for the right output voltage: anything (within reason) is OK as long as the two resistor values have a ratio of 5V/35V or 1 to 7.
For instance, 4.7k and 33k are pretty close to 1:7. (Actually 7.02).
But again, an output voltage of 39V or 41V would be pretty good too - there's nothing 'magical' about having exactly 40V.
Jan
If I'm not missing something also...
Probably is because the graph is a FFT and grass is at -120dB at 1kHz, but for all audioband, this will represent less "dB" (eg. a perfect 16bits has a FFT "grass" of -130dB, and has a SN/R near 96dB, if I rememer well - please correct these numbers if someone have the correct info, but the logic is in this direction). Formula for this conversion exists but I never used that or even remember that, sorry
.
I have been asked for PCBs for the High Octane. I checked with Hannes, no more PCBs but if there is interest he might get another batch.
Anybody interested in a PCB for this? The full article is temporarily available from Linear Audio for just € 0.49
Jan
Anybody interested in a PCB for this? The full article is temporarily available from Linear Audio for just € 0.49
Jan