Posted 4th September 2010 at 05:58 PM byalexcp (My DIY projects)
Updated 5th September 2010 at 07:59 PM byalexcp
This was unavoidable, I guess. Dual mono LM3886 kit from ChipAmp.com with Avel Lindberg's transformers in a wonderfully compact enclosure from Design Build Listen. I liked the simplicity but not the sound. Why is everyone so excited with gainclones? IMHO, Papa's Zen V4 is not much more complicated to build (although no kit is available), but is so much more an interesting experience!
Posted 4th September 2010 at 05:54 PM byalexcp (My DIY projects)
Updated 7th July 2011 at 12:33 AM byalexcp
Last year I got an Lm60 kit from AmpsLAB. This year, I finally got an enclosure from Design Build Listen and a power supply and built it. Each channel is built on a small (120x60mm) one-sided PCB and uses one 2SK1058+2SJ162 pair in the output stage. With proper biasing, the sound is good, esp. for such a simple and compact design. I should have started with this one, rather than with the (equally inexpensive) K-8LS.
Posted 31st August 2010 at 10:44 AM bywintermute (Wintermutes Rantings)
Well I said no more excuses, and I for the most part started to make some progress. But good old Murphy stepped in and threw a spanner in the works.
The Boot Drive on my main computer decided to die on me, I've got backups of all the important stuff so no big deal other than the inconvenience. I could always use my work laptop... step in Murphy again, it too decided to die... once again have backups but all of a sudden nothing to run LT spice on, bring up my Plans, test data or anything.. I've got a loan one but I'm not going to set it up for a couple of weeks only.
So since my main computer was nearly 8 years old (single core Athlon 2000 which is really only 1667Mhz) I decided an upgrade was in order... This would probably have been a relatively modest machine if it weren't for my recent discovery of LTSpice and the knowledge that it takes a lot of cpu grunt, and that it benefits from multiple cores!!
Posted 31st August 2010 at 03:34 AM byabraxalito Updated 1st September 2010 at 04:23 AM byabraxalito
Here are the schematics - the original output stage and the modified one.
On the first player I bought, I did all those mods in one hit. The third pic shows what they looked like - I took out some of the redundant connectors (guessing the same board is used in players which have more features like component video outputs) to make space for the electrolytics. Having replaced the board (just two screws, one on the rear and another in the base), then I listened. The improvement in bass performance brought about by increasing the value of the coupling caps was noticeable in listening - the cello became more full-bodied - and also on a frequency response plot I made using Audacity. I felt (but can't quite describe) that the soundstaging has improved - music feels more interesting to listen to somehow. I week or so later, I went out and bought a second one (at 99RMB, who's counting?) to remind myself of the original sound. On listening for the first time to a CD I'd just bought...
We're having a small get-together at my place Thursday, October 21st. Besides a group of visiting audio geeks (Jan Didden, Pete Millett, Panomaniac, rkoonce, sonidos, and their tolerant spouses), we're having a house concert, featuring the insanely talented alt-country singer/songwriter/guitarist Robert Ellis (who will be selling his CDs and vinyl) doing an all-acoustic show. Lots of beer and wine to drink, much food, much merriment, and a chance to hear my lousy low resolution stereo.
Room for three or four more people. PM or email me if you want to join the festivities.
The amplifier is probably the single most important composite circuit element in electronics. Certainly such familiar devices as radios and music systems would be impossible without amplifiers. The very large majority of amplifiers these days are solid state, that is, they use transistors. While there are many types of transistors, the first mass-produced transistors were BJTs, or bipolar junction transistors, and understanding transistor amplifiers, for most people, begins with these.
The transistor has three terminals and can be arranged in three basic amplifier configurations, the common emitter, common base (or grounded base) and common collector or emitter follower amplifiers.
Common base amplifiers are not commonly employed at lower frequencies as, amongst other reasons, they have a low input impedance, although they can be found in amplifiers for e.g. moving coil microphones. They are sometimes employed as current buffers, having a current gain of 1,...
Keantoken C multiplyer
Here is the output impedance using the 2SC4793/A1837 pair. This rivals some of the best electrolytics I have measured. It would be hard to improve on this using anything but film caps.
post1259, latest version
Q2 & J6 should be fed from the supply rails, not from the measurement rails.
What voltage (Vdg) is across the BF862 when they are set to 2 to 4mA?
I think you should be using a low Vpinch off for some of these locations, particularly J5 and maybe J6.
Here is the SCH of this Board that you see above.
I didn't buy any part yet, but I'm waiting for the board quote.
In fact I'm looking for chassis and cases for my amp. I'm very demanding with the case, especially for a project with this price.
I'm designing a KT-88 Ultralinear amplifier using the idea of Satoru Kobayashi 2002.
The pre amplifiers is a solid state using a TL-72 with gain 10 and the second stage i have the superb DRV134 Burr-brown (Low distortion: 0.0005% @ 1KHz) which is a differential output amplifier.
Following comes the 6N1P svetlana and the EI 12BH7AEG direct coupled and the last stage with KT-88.
The most important part is that it's all in one, I mean, all in one board. I integrated the high voltage power supply regulator and the low voltage for the op-amps in the board eliminating wires around.
I've been working in this board for more than 3 months and creating BOM, calculation an so one. So far the project is around U$ 1266,00 including all parts, not board, and transformers plus the tubes.
Attached you can see the print-screen of the board. I didn't send to production yet, and i plan to go slowly in this project due the cost mostly...
Posted 15th August 2010 at 01:50 PM byalexcp (My DIY projects)
Updated 15th August 2010 at 04:18 PM byalexcp
This handy instrument is a version of the design published in Australian Silicon Chip (a subscription is required to view the details of the article). It is based on a dsPIC33 microcontroller, has TOSLINK and S/PDIF digital outputs (44.1k, 48k and 96k sample rates) and a stereo analog output. Output frequency, phase, attenuation, and other parameters are set by the keyboard. It produces sine, square, triangle, and sawtooth waves and has a variety of modes. It can be powered by an external DC source or a battery. The article claims low distortion for sinewave (less than .06%) and even lower with a good external DAC, but I did not have a chance to verify that just yet. Highly recommended.