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After not getting around to it for too long, Kindle battery replacement. I used this excellent guide:
https://www.ifixit.com/Guide/Kindle+4+Battery+Replacement/117079
Now reading Woodward's book, Rage.
Ipod 30Gb could be next.
https://www.ifixit.com/Guide/Kindle+4+Battery+Replacement/117079
Now reading Woodward's book, Rage.
Ipod 30Gb could be next.
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- Thread Starter
- #143
Bamboszek
Active Member
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Hah, I used to have Cambrdige Audio DacMagic and iConnectivity ConnectAUDIO4+ which are also on this photo. iConnectivity was a huge disappointment however. Manufacturer specified -112 dB THD+N what was simple lie, exceeding even datasheet values of used ICs (AK4627 codec and NJM4580 opamps). Loopback measurement barely reached -87dB THD+N.
What is this preamp, your own design? Thick blue PCB reminds me Glassware / John Broskie's stuff. Nice guitar BTW.
What is this preamp, your own design? Thick blue PCB reminds me Glassware / John Broskie's stuff. Nice guitar BTW.
- Thread Starter
- #145
You are right about the iConnectAudio4+. The poor part with high noise is the input, A/D part. It gets better when driven from low impedance, low I mean <10 ohm. They probably use JFET switches to change range and they seem to have very nonlinear Rds resistance. If you measure DAC in isolation, the result is much better. But loopback is horrible, because DAC Zout is 470 ohm. However, the patch network is very flexible and with mike the performance is sufficient, as well as for speaker measurements. The biggest advantage to me is that it works natively with the iPad.
The tube preamp has its own thread with measurements here
https://www.audiosciencereview.com/...ube-preamp-kit-review-and-measurements.15883/
19" aluminum NAB 2U plate that now has 8 holes drilled in it and Nuetrik female BNC mounted -have just started soldering some thrift store find RG-59 (fresh 250 foot roll stereo for $7.95) to these - other end will be Nuetrik Profi male RCA's on the other end. This panel will mainly be used as a patch panel to switch various SPDIF devices into the two SPDIF inputs on my Maridian DSP-5000 speakers. 55 years of being plagued by RCA connectors has inspired me to hate ,loath and despise the damm things. The ProFi's at least make a decent ground connection without ripping the lousy mating female RCA out of the equipment they are plugged into. This eliminating most analog feeds was inspired by recent purchase and use of the Parks Audio Puffin with a SPDIF out. My remaining analog sources go into ADC's and then to this patch panel -eliminating a bunch of analog cabeling/RCA connectors and a Linn Kollector preamp from the signal path. Currently accomplished with a snakes nest of BNC terminated cables that SWMBO'd definitely looks upon with a hairy eyeball.
I've been thinking about how much level comes off my turntables, compared with the fixed 2V maximum that comes off my digital sources. So, what I need is a PPM to measure what's coming off the turntables.
I'm taking a Velleman VU meter kit K4306 as it had a good PCB, with all the LEDs nicely laid out, and 1dB between the +5 and -5 indications.
I'm then replacing the half-wave average reading rectifier with a full-wave peak rectifier to DIN PPM specification. The LED indicator doesn't care what it's fed with, it just lights up according to the DC level it's sent. This will be a quasi-peak indicator with 10mS rise time for -1dB, -20dB fall in 1.5 seconds, so pretty much what I'm used to seeing in a PPM. It'll miss any very sharp rises, but I'll accept that, as making a hardware true-peak indicator is in the 'too-hard' category.
I have then found a use for the 'world's cheapest DAC' (mine was actually £3.45 including free shipping from China!!) to provide decoding for the CD player and SBT digital outputs, and I'll arrange the gain of the rectifier such that on the two digital inputs, the +5 LED indicates 0dBFS, whilst on the analogue inputs, 0dB is +8dBu (2V) so the +5 LED indicates +13dBu. As my turntables are set to give 0dBu out on 5cm/sec recorded velocity at 1kHz, I should be able to see if any LPs are recorded particularly hot, up to 13dB above 5cm/sec.
It'll all be fitted into a 2U rack mounting box using an old Behringer SMPS that provides +-15v for the analogue electronics and +5v for the DAC.
It's great to have the time to do stuff like this.
S.
I'm taking a Velleman VU meter kit K4306 as it had a good PCB, with all the LEDs nicely laid out, and 1dB between the +5 and -5 indications.
I'm then replacing the half-wave average reading rectifier with a full-wave peak rectifier to DIN PPM specification. The LED indicator doesn't care what it's fed with, it just lights up according to the DC level it's sent. This will be a quasi-peak indicator with 10mS rise time for -1dB, -20dB fall in 1.5 seconds, so pretty much what I'm used to seeing in a PPM. It'll miss any very sharp rises, but I'll accept that, as making a hardware true-peak indicator is in the 'too-hard' category.
I have then found a use for the 'world's cheapest DAC' (mine was actually £3.45 including free shipping from China!!) to provide decoding for the CD player and SBT digital outputs, and I'll arrange the gain of the rectifier such that on the two digital inputs, the +5 LED indicates 0dBFS, whilst on the analogue inputs, 0dB is +8dBu (2V) so the +5 LED indicates +13dBu. As my turntables are set to give 0dBu out on 5cm/sec recorded velocity at 1kHz, I should be able to see if any LPs are recorded particularly hot, up to 13dB above 5cm/sec.
It'll all be fitted into a 2U rack mounting box using an old Behringer SMPS that provides +-15v for the analogue electronics and +5v for the DAC.
It's great to have the time to do stuff like this.
S.
restorer-john
Grand Contributor
Play some 12" 45rpm singles if you want to see "particularly hot".
I like the way you can trim the resistor value using a pencil sharpener!How about pencil resistors?
Non-inductive, non-magnetic graphite. Audiophile quality, I promise
View attachment 88714
A lot easier than laser trimming!
S
How about pencil resistors?
Non-inductive, non-magnetic graphite. Audiophile quality, I promise
They make good voltage dividers if you're in a pinch.
restorer-john
Grand Contributor
We got caned in the science labs for carbon arcs on steel rulers and smoking up pencils (sharpen each end and attach to the lab power supplies). I worked out really quickly which grades of pencil (2B) made the most smoke.
restorer-john
Grand Contributor
25 years ago (I was in my very late 20s) I decided to build a >200W@8R/350W@4R MOSFET amplifier using Exicon MOSFETs based on the K-5180 design published in Silicon Chip. I amassed all the parts, except a case (I was going to have that built for me).
I recently pulled the box out of long term storage as I'd moved on to bigger and better gear, and never finished the build...
Here it is. The box weighs 22.6kg. Two choices of transformers, a pair of 650W toroids or a higher voltage pair of 700W toroids. 160,000uF of capacitance (16x10,000uF 100V caps). 16x Exicon P and N Mosfets. A full set of gold terminals, three heatsinks (in case I buggered one up drilling like I did with my other "super" amp in the 1980s), brackets, heatsinks etc.
The two main boards are 90% assembled, just the drivers and outputs to go in on whatever mount I was going to choose.
Should I scrap the idea altogether and put the box back in storage, or maybe finish two big monoblocks instead (I don't feel like any more big stereo power amps)? There's about $1K worth of parts all up. Even a 10"x12" sheet of silicone impregnated insulator which was going to be cut into a long strip under the rows of MOSFETS.
I dunno, get me excited, what to do with this project? The choices in casework now (25 years later) are amazing. Do I throw more money at it with a few nice cases? I don't need another big amp, but leaving it unfinished is a bit naughty. Ideas?
I recently pulled the box out of long term storage as I'd moved on to bigger and better gear, and never finished the build...
Here it is. The box weighs 22.6kg. Two choices of transformers, a pair of 650W toroids or a higher voltage pair of 700W toroids. 160,000uF of capacitance (16x10,000uF 100V caps). 16x Exicon P and N Mosfets. A full set of gold terminals, three heatsinks (in case I buggered one up drilling like I did with my other "super" amp in the 1980s), brackets, heatsinks etc.
The two main boards are 90% assembled, just the drivers and outputs to go in on whatever mount I was going to choose.
Should I scrap the idea altogether and put the box back in storage, or maybe finish two big monoblocks instead (I don't feel like any more big stereo power amps)? There's about $1K worth of parts all up. Even a 10"x12" sheet of silicone impregnated insulator which was going to be cut into a long strip under the rows of MOSFETS.
I dunno, get me excited, what to do with this project? The choices in casework now (25 years later) are amazing. Do I throw more money at it with a few nice cases? I don't need another big amp, but leaving it unfinished is a bit naughty. Ideas?
Bamboszek
Active Member
- Joined
- Mar 17, 2018
- Messages
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- Likes
- 306
Wow, those parts looks impressive! But after all those years big electrolytic capacitors might require reforming.
Lateral MOSFETs are lately getting very hard to source. Renesas EOLed them a few years ago, is Exicon still in business?
I don't know performance of that K-5180 design, but if you want state of the art amplifier try to find somewhere LME49830 driver chip. Also discounted few years ago but still hard to beat. LME49830 with pair of MOSFETs you can easily reach 100-105dB SINAD.
LME49830 Datasheet
Interesting project
Lateral MOSFETs are lately getting very hard to source. Renesas EOLed them a few years ago, is Exicon still in business?
I don't know performance of that K-5180 design, but if you want state of the art amplifier try to find somewhere LME49830 driver chip. Also discounted few years ago but still hard to beat. LME49830 with pair of MOSFETs you can easily reach 100-105dB SINAD.
LME49830 Datasheet
Interesting project
Still getting familiar with my QuantAsylum equipment. So am testing my NC502MP with it. The QA451 programmable load has thermal protection so can only drive so hard. Am planning to build a higher power load to supplement.
Here are a couple of early results (with both channels driven):
...and with a single channel:
Here are a couple of early results (with both channels driven):
...and with a single channel:
Well the QA451 is handy, but could only handle 200 watts for less than a quarter of a second. Have had some nice aluminum heatsinks from an amplifier project that did not materialize. Bought a couple of 4 ohm 200 watt resistor and tapped screw holes for the first of the pair...
A quick test and can the thd vs power plug-in on my Hypex NC500 without even noticeably warming the resistor. I ran the spectrum analyzer at 0 db for a couple of minutes and that was enough to get it warm to the touch. Now to add the second resistor so I can test at 2 or 8 ohms too.
A quick test and can the thd vs power plug-in on my Hypex NC500 without even noticeably warming the resistor. I ran the spectrum analyzer at 0 db for a couple of minutes and that was enough to get it warm to the touch. Now to add the second resistor so I can test at 2 or 8 ohms too.
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restorer-john
Grand Contributor
Well the QA451 is handy, but could only handle 200 watts for less than a quarter of a second. Have had some nice aluminum heatsinks from an amplifier project that did not materialize. Bought a couple of 4 ohm 200 watt resistor and tapped screw holes for the first of the pair...
View attachment 91504
A quick test and can the thd vs power plug-in on my Hypex NC500 without even noticeably warming the resistor. I ran the spectrum analyzer at 0 db for a couple of minutes and that was enough to get it warm to the touch. Now to add the second resistor so I can test at 2 or 8 ohms too.
Have you checked those 200W resistors' inductance?
If they're anything like the Chinese cheapies I bought from Amazon for my dummy load, quite low. Impedance vs frequency up to 48kHz barely budged.
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