Digitally controlled preamp/headphone amp

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bikedude

Member
Joined 2004
BrianDonegan said:
I have just posted the latest HEX code on the site (Kooaburra page). Here is a shortcut to it.
Click to expand...


What version of the firmware is in this hex file? Does it solve the glitch at the 0 volt crossing of version 1.1? What are the changes in this hex file compared to the previously posted main.txt source code? Would it be possible to post the source too?

Wow that's a lot of questions!

BTW, thanks for putting together the great Twisted Pear kits and all your great support.

(K)
 
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bikedude

Member
Joined 2004
Re: Where is the HEX file for 12F683/12F675?

bbp said:
This thread is too much long,I can't find it myself.
Could any body show it to me or mail it to my mail box?
Thanks!
And ,are 12F683 and 12F675 the same?
Click to expand...


No, they are not the same. Depending on the features you use, the same source code may be compiled for either processor. However, the resulting hex files are processor-specific. Either chip will work in the Kookaburra; I've used them both.

(K)
 
BrianDonegan

BrianDonegan

Member
Joined 2004
twistedpearaudio.com
Er, I don't think there ever was a zero-volt crossing issue. There was speculation about it though.

There was an issue with v1.1 of the code, due to a C compiler bug, which resulted in a full volume blast in a particular position near full attenuation - it scared the crap out of me even when I knew it was coming ;)

We are currently shipping the V1.0 code, which didn't really have any issues. Russ was just trying some new things out based on work he was doing in the Joshua Tree pic code.

So, the HEX up there is V1.0. If you search on "main.txt" you will find the source in the thread.
 
B

bikedude

Member
Joined 2004
BrianDonegan said:
Er, I don't think there ever was a zero-volt crossing issue. There was speculation about it though.
Click to expand...


In my testing, the blast happend at the crossing between 0v and the next 5/256 volt. (5 volts / ADC precision)

There was an issue with v1.1 of the code, due to a C compiler bug, which resulted in a full volume blast in a particular position near full attenuation - it scared the crap out of me even when I knew it was coming ;)
Click to expand...

Amen brother! The first time it happened to me it nearly knocked me over. While I was investigating, I hooked it up to a crappy old set of headphones and just let them sit on the side of my head (i.e not in my ears). This technique kept me from having to do excessive amounts of laundry.

(K)
 
BrianDonegan

BrianDonegan

Member
Joined 2004
twistedpearaudio.com
"Zero crossing" refers to a technique used in the PGA to only make volume changes when the audio signal is at the zero-crossing point, eliminating pops.

From the datasheet:
"The PGA2311 includes a zero crossing detection function
that can provide for noise-free level transitions.
The concept is to change gain settings on a zero crossing
of the input signal, thus minimizing audible glitches."

This is what I was referring to.
 
C

curtvm

Member
Joined 2006
I figure this may be the best place to ask this-

I just purchased a Kookaburra which will be driving an Amp6. Currently have the Kook put together (but not powered up yet), and am in the process of completing the Amp6-

http://www.mtcnet.net/~henryvm/amp6/

I have a question about the input gain I should use on the Amp6- my choices (using the components supplied) are -1.8v/v (portable mp3/cd player), -1v/v (general use), -0.56v/v (preamp with fairly high output signal). The total gain of the Amp6 (voltout/voltin ) is 12 times the input gain. The maximum possible voltage the input stage should handle is about 4V peak to peak (1.41 VRMS).

So assuming I want to be able to use the full range of the pga2311, and am using "standard" line outputs from a dac, what would be the recommended input gain on the Amp6?

I assume there is some easy way to figure this out, but I don't know what it is (max line input voltage x max pga2311 gain X amp6 input gain <= 4v pp or 1.41vrms ?)

Thanks for any input you experts may have!
 
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curtvm

Member
Joined 2006
OK. -0.56v/v it is.

Seems like I can get alot from the pga2311. If not, I should be able to adjust input or output buffer on kookaburra (tda1543 will be driving kook- which seems to put out good voltage from what I can gather).

Once I solder in resistors into amp6, they are there to stay.
 
A

awpagan

Member
Joined 2004
Russ
This may have been mentioned before but,
pga2311 +/- 5v analogue
pga2310 +/-15v analogue

pga2310 much better for volume headroom in a preamp, plus pin compatible.

If you used separate 5v reg's for digital and analogue, it will give you a choice in which pga (2310/2311) to use.
If you used 317/337's, just change resistor values.

allan
ps
besides separate analogue digital power supply and grounds makes a big difference.
Just look at any cdplayer mob and upgrades.
 
C

curtvm

Member
Joined 2006
bikedude said:
I'd go with the general use setting so that you could use it with other pre-amps and portable mp3 players. It will also work fine w/ the Kooka at that level. I use a chipamp w/ 23:1 gain and get usable volume control w/ the Kooka.
Click to expand...

Thanks for the advice- I plan on making this amp system 'permanent', so would like to be able to use the full range of the kook. Maybe I'm making this harder than what it is, but I'm trying to figure what the max output of the kook would be with a tda1543 on its input (tda1543 running on 5volts, 1k on vref and on outputs). I'm not sure what +30db on the pga2311 computes to in terms of voltage, I'm trying to find out but come up with 30x input, which doesn't seem right.

I should just probably hook up the dac to the kook, then measure output on the kook at max volume. Then figure what the amp6 input gain needs to be for max output on the amp6, then solder the amp6 resistors in.
 
BrianDonegan

BrianDonegan

Member
Joined 2004
twistedpearaudio.com
Russ
This may have been mentioned before but,
pga2311 +/- 5v analogue
pga2310 +/-15v analogue
Click to expand...

This has been mentioned several times around DIYAudio. Here are a few things I never see mentioned...

PGA2311 - Input Capacitance: 3pF
PGA2310 - Input Capacitance: 7pF

PGA2311 - THD: .0002
PGA2310 - THD: .0004

PGA2311 - Output Noise: 4uV
PGA2310 - Output Noise: 13.5uV

PGA2311 - Crosstalk: -126dB
PGA2310 - Crosstalk: -130dB

PGA2311 - Output Offset: 3.0mV
PGA2310 - Output Offset: 0.5mV

Compare graphs on Page 5 of each's datasheet. More to it than just voltage swing... ;)

We have talked about seperate supplies in future revisions, for this and for better isolating digital/analog. A few things to work on before that though
 
A

awpagan

Member
Joined 2004
BrianDonegan said:


This has been mentioned several times around DIYAudio. Here are a few things I never see mentioned...

PGA2311 - Input Capacitance: 3pF
PGA2310 - Input Capacitance: 7pF

PGA2311 - THD: .0002
PGA2310 - THD: .0004

PGA2311 - Output Noise: 4uV
PGA2310 - Output Noise: 13.5uV

PGA2311 - Crosstalk: -126dB
PGA2310 - Crosstalk: -130dB

PGA2311 - Output Offset: 3.0mV
PGA2310 - Output Offset: 0.5mV

Compare graphs on Page 5 of each's datasheet. More to it than just voltage swing... ;)

We have talked about seperate supplies in future revisions, for this and for better isolating digital/analog. A few things to work on before that though
Click to expand...


thanks Brien
i need to study the datasheets again:rolleyes:
Has been a while, got the 2310's,2311's and 4311's (samples)over 2 years ago, haven't done anything with them.
saw them here
http://www.mhennessy.f9.co.uk/preamp/index.htm

allan

ps I need a volume control the my x******bosoz:D "pre-twisted"
 
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