hi salas ! i am using the original 2SB737 (ROHM, Hiraga used Toshiba when i beleave the literature) here but the Hitachi-Renaisas equivalant is even lower in noise particular with a lower corner frequency and it has up to 600 Hfe when you get good ones, reducing DC offset at the input due to lower base current. my intention was to closely mimic Hiragas work but i found his choices not ideal in my system. i find it tragic that there are so few manufactures left that produce good transistors for low noise, low distortion audio work. there are some video types not intended for audio that do a very good job too, thank you very much. one philosopher said something like "we are living in the time of quantity, quality has gone a long time ago". it whould like to send a prayer to Linear Systems to come up with some good P Fet devices single and double for my high Z MPP.
[QUOTE=Joachim,
>>>Allen: the circuit is theoretical. to avoid thermal drift i would search for fets that need around 0.65 volts of gate voltage and produce 2mA. then i would thermocouple both. at that voltage temperature dependence of fets is near zero<<<
OK. Yes, all of those things would need to be done to make it stable.
>>> i am really surprised that you come up with that kind of questions. don´t you know that i have studied with some really extraordinary people and that kind of problems are so easy to solve it is a joke ?<<<
You obviously are pretty smart, but lots of people with different skill levels read these posts, and if someone with less skill than you or I sees your circuit (which is NOT labled as theoretical anyplace I can see) and builds it - they could have a problem with DC through their expensive cartridge.
>>what do you think about a servo to keep the current stable?<<<
If you want to make something simple(ish) into something complex, why not?
It's an elegant topology, and I will be trying it as a I/V converter for a DAC chip.
Regards, Allen
>>>Allen: the circuit is theoretical. to avoid thermal drift i would search for fets that need around 0.65 volts of gate voltage and produce 2mA. then i would thermocouple both. at that voltage temperature dependence of fets is near zero<<<
OK. Yes, all of those things would need to be done to make it stable.
>>> i am really surprised that you come up with that kind of questions. don´t you know that i have studied with some really extraordinary people and that kind of problems are so easy to solve it is a joke ?<<<
You obviously are pretty smart, but lots of people with different skill levels read these posts, and if someone with less skill than you or I sees your circuit (which is NOT labled as theoretical anyplace I can see) and builds it - they could have a problem with DC through their expensive cartridge.
>>what do you think about a servo to keep the current stable?<<<
If you want to make something simple(ish) into something complex, why not?
It's an elegant topology, and I will be trying it as a I/V converter for a DAC chip.
Regards, Allen
Hi Allen ! I was in a bad mood yesterday, sorry. I can see your point now better. You behaved as a lawyer for the DIY society and that is noble. I am honord that you will try my circuit. Yes, it is a good and simple I/U converter.
I will make more shure in the future if a circuit is still in it´s infancy to tell peoble that it is not ready yet for 1:1 copy. i was a bit difuse about that. I will call those circuits ALFAS in the future. An idea that syn08 had, and i find that good nomenclature.
I will make more shure in the future if a circuit is still in it´s infancy to tell peoble that it is not ready yet for 1:1 copy. i was a bit difuse about that. I will call those circuits ALFAS in the future. An idea that syn08 had, and i find that good nomenclature.
Today i got more 25mH coils and had some spares to try them in the power supply of the Hiraga. It was a major success. Without the coils there was still a faint low frequency rush that totally disappeared with the coils. I simulated the combination of the caps and coils i used and it suppresses 50Hz by 12dB with a 12dB octave roll off. So 100Hz is suppressed by 24dB and so on. 50mH with 20.000uF would be even better with -24dB at 50Hz. The pre-pre is now extremely quit and the noise sounds very "white", quite different from an OP amp chip that has a more complex character. The sound got more smooth and liquid, maybe because of lower intermodulation distortion. As exiting the sound was without the coils this is maybe more accurate.
I also worked further on the inductive RIAA and put the coils in a separate soft steel box. Hum was even lower then before but still not zero and ear on speakers the noise did not sound exactly the same on both channels. I will try Mu Metal now. This is quite challenging. The sound of the inductive RIAA is quite different from what i heard before. Somehow it is more real with a particular translucent midrange but also quite rough around the edges like carved from wood. It is still no match in terms of "HiFI" like my Telepath MM stage that is somehow smoother and more linear but it shows great potential that i would like to explore further. i will now keep my system constant until Holger Barske comes on the 22nd. I plan to play the Hiraga with Telepath and the MPP Low Z with the inductive RIAA in comparison. Both systems sound the way i like it. Very dynamic and open with big drama. Emotionally moving and you forget about the HiFi. Both setups can do that. See the Circuit diagram that shows the current setup of the Hiraga optime. The 4 Ohm resistors are the impedance of the filter coils.
I also worked further on the inductive RIAA and put the coils in a separate soft steel box. Hum was even lower then before but still not zero and ear on speakers the noise did not sound exactly the same on both channels. I will try Mu Metal now. This is quite challenging. The sound of the inductive RIAA is quite different from what i heard before. Somehow it is more real with a particular translucent midrange but also quite rough around the edges like carved from wood. It is still no match in terms of "HiFI" like my Telepath MM stage that is somehow smoother and more linear but it shows great potential that i would like to explore further. i will now keep my system constant until Holger Barske comes on the 22nd. I plan to play the Hiraga with Telepath and the MPP Low Z with the inductive RIAA in comparison. Both systems sound the way i like it. Very dynamic and open with big drama. Emotionally moving and you forget about the HiFi. Both setups can do that. See the Circuit diagram that shows the current setup of the Hiraga optime. The 4 Ohm resistors are the impedance of the filter coils.
Hi Allen ! Maybe we can make a trade in. I never heard your preamps under controlled conditions. For power amps i use more high power fast transistor stuff but i am working on 96dB sensitivity dipols too. We make the midrange ourself and i am waiting for Alex from RAAL to have his dipol ribbon ready. That is really a freaky loudspeaker i was planning to have ready when i am 50 and now i am 52 ! Time passes by so fast.
Joachim -
I'm glad you're trying out the inductive RIAA - it's on my list of things to do. I have a short thread on the subject from a few months back. Everyone I've read about so far that tried it deems it to be at least different sounding than RC equalization, and some think it superior.
Have you tried looking for the standard pot core shielding hardware? Siemens and Ferroxcube/Philips once had a whole line of mounting and shielding accessories for pot cores, no doubt aimed at telecommunications precision filter applications. I intend to try this before I go to more extreme measures. I was lucky enough to find a bunch of 4229-size pot core transformers in shielding cans on the surplus market. Since they were not varnish impregnated, they will be easy to pry apart and adapt to my nefarious purposes...
I'm glad you're trying out the inductive RIAA - it's on my list of things to do. I have a short thread on the subject from a few months back. Everyone I've read about so far that tried it deems it to be at least different sounding than RC equalization, and some think it superior.
Have you tried looking for the standard pot core shielding hardware? Siemens and Ferroxcube/Philips once had a whole line of mounting and shielding accessories for pot cores, no doubt aimed at telecommunications precision filter applications. I intend to try this before I go to more extreme measures. I was lucky enough to find a bunch of 4229-size pot core transformers in shielding cans on the surplus market. Since they were not varnish impregnated, they will be easy to pry apart and adapt to my nefarious purposes...
Unfortunately i have to do different temperatures for different jobs. Can be as low as 280-90 ° for small resistors, 330° for medium parts and more the 400° for bigger pieces. It´s a pain in the bud. We use Metcal soldering irons in the USA that are easier to work with then my Weller station i use here. Somehow they adapt automatically to the situation. HS10 sound quite good but i think Kristall511 is even better. My friends in the USA use ETI Eichmann solder that is good too.
Wrenchone, yes, inductive is a new world. The reason i have not tried commercial shielding
cans is that we are used to build prototypes our selfs with what we have but this time i run out of steam. Can not wait to hear more from your Lineac. I think is is a good circuit and it reminds me on old times. A friend of mine ( a very good HF engineer) always build single ended and i build parallel symmetric. We had endless discussions about what is better. I also learned a lot from JLH. I think he did a great job for coming up with quite simple solutions that still performed well for the time they where introduced.
cans is that we are used to build prototypes our selfs with what we have but this time i run out of steam. Can not wait to hear more from your Lineac. I think is is a good circuit and it reminds me on old times. A friend of mine ( a very good HF engineer) always build single ended and i build parallel symmetric. We had endless discussions about what is better. I also learned a lot from JLH. I think he did a great job for coming up with quite simple solutions that still performed well for the time they where introduced.
There is a yearly festival in Kassel. They hire a German installer that uses a line array that a friend of mine designed. True line, uses planar elements.
Not that strange.
Kent is the guy with the tripod steampunk speakers on Burning Amp's photos BTW. Well, those are really strange.Attachments
tvi, that circuit is from Rambeyrolles also published in L`Audiophile. It was the first folded cascode that i have seen in audio. Unfortunately the 120 feedback resistor does make more noise then necessary and the MAT02/03 combination is no good for lowest distortion and symmetry because of very different Hfe. The PNP has very little. I stumbled upon that stone also in the beginning of my adventure. Anyway, it did inspire me. it´s a visionary circuit. The 120 Ohm could be much lower if you use stronger transistors for the cascodes. Something like BC140/160. If that problems are solved it should sound very well.
Salas, do you mean the festival in the tent ? Kassel is a very interesting town. I studied furniture design and Exhibition design there. Come to the Documenta, the biggest art show festival in the world.
Salas, do you mean the festival in the tent ? Kassel is a very interesting town. I studied furniture design and Exhibition design there. Come to the Documenta, the biggest art show festival in the world.
Yes, Salas, same idea but i whould try DC coupling. Anyway, i had never dreamed that i could make the Hiraga that good sounding. I really go through a period of simplification right now. Because i will not work on phonos for the next days i will look if i can steal time for your meaner shunts or are the minor shunts ?