I think if you get envelope size bigger than smalest,and I get custom declarations for free when I buy stamps.🙂
Member
Joined 2002
Mad_K said:
maybe phone the post office and see ? Or take one down to them and see. best to ask than make them all up and have to do it all over again.
Is it really necessary with customs declaration?
I'll check it out tomorrow. I think the best option would be to use just a regular envelope. I also believe you get the "par avion" and customs declaration stickers for free. Up to 20grams it is 2USD up to 50g it is 3USD. I'll wrap the boards in some paper and put the bag with components (for those who ordered components) in there too.
I forgot to say: shipping is included with the 10$ envelope.
I'll check it out tomorrow. I think the best option would be to use just a regular envelope. I also believe you get the "par avion" and customs declaration stickers for free. Up to 20grams it is 2USD up to 50g it is 3USD. I'll wrap the boards in some paper and put the bag with components (for those who ordered components) in there too.
I forgot to say: shipping is included with the 10$ envelope.
Member
Joined 2002
Mad_k YOU have money in your paypal 🙂 Please read the instructions i have provided in the paypal Payment.
Member
Joined 2002
Mad_K said:
right on. ! Keep up the good work. Hope to have these running good. What would the max rail voltage be..
Depends on the capacitors you use and how well you manage to cool the mosfets.. And how BOLD you are ofcourse 😉
I would say 35V is the upper limit (with 35V caps).
It also depends on the bias level you are setting.
What is best, depends on your speakers.
A stock SEWArB (300VA 2x18VAC trafo) will give you 7WRS in both 8 and 4 ohm speakers.
The next level will be a 300VA+ 2x24VAC trafo for 30VDC rails.
This will yield about 12W on 8 and 6 ohm speakers and 8W on 4 ohm speakers. To get 12W on 4 ohm speakers you need 2,5A bias.
Now, 2,5A and 30V is getting hot: 75W total and 35-40W per mosfet..
Use R1=5K6 for 30V rails.
Use 1ohm for R12-R16 for 2,5A bias.
You will notice in the latest schematic that I have left R12 NOT MOUNTED for 2A bias.
I would say 35V is the upper limit (with 35V caps).
It also depends on the bias level you are setting.
What is best, depends on your speakers.
A stock SEWArB (300VA 2x18VAC trafo) will give you 7WRS in both 8 and 4 ohm speakers.
The next level will be a 300VA+ 2x24VAC trafo for 30VDC rails.
This will yield about 12W on 8 and 6 ohm speakers and 8W on 4 ohm speakers. To get 12W on 4 ohm speakers you need 2,5A bias.
Now, 2,5A and 30V is getting hot: 75W total and 35-40W per mosfet..
Use R1=5K6 for 30V rails.
Use 1ohm for R12-R16 for 2,5A bias.
You will notice in the latest schematic that I have left R12 NOT MOUNTED for 2A bias.
Mads,
please use just a regular envelope, that is perfect. Just wrap the boards individually in another pieces of paper. I have received several pcbs like that without problems. No hassle with customs etc. This is a group buy, so to say, not a business.
please use just a regular envelope, that is perfect. Just wrap the boards individually in another pieces of paper. I have received several pcbs like that without problems. No hassle with customs etc. This is a group buy, so to say, not a business.
Hi Mads,
Are you getting sufficient interest in a second run of boards, or am I better off creating my own at this point in time?
Regards,
Mark
Are you getting sufficient interest in a second run of boards, or am I better off creating my own at this point in time?
Regards,
Mark
Lots of interest in boards, so there will be another run shortly. Anoyone interested should send me an email, and I'll add you to the list 😉
OK, I'll just just a regular envelope and don't bother with the cutoms declaration then.
OK, I'll just just a regular envelope and don't bother with the cutoms declaration then.
Hi Mads!
Don't you want to design a Balanced version of the SEWA V1?
I have 4 matched pair of IRFP240 and I am interested to know what is the sound of a fully balanced system like the BOSOZ and the Balanced-SEWA would give. Aren't you interested too?
Greets:
Tyimo
VII Audio Rulez!
Don't you want to design a Balanced version of the SEWA V1?
I have 4 matched pair of IRFP240 and I am interested to know what is the sound of a fully balanced system like the BOSOZ and the Balanced-SEWA would give. Aren't you interested too?
Greets:
Tyimo
VII Audio Rulez!
Mosfet Substituion question
Hi MAD_K.
Its difficult or expensive to find the IRF150s or the IRF250s around here. But I can get several other types of power mosfet (from scrap switching power supplies). My question is what is the main parameters that you look for in order to choose a Mosfet for SEWA or OTA type amplifier?
Thanks
Edgardo.
Ready to build an OTA.
Hi MAD_K.
Its difficult or expensive to find the IRF150s or the IRF250s around here. But I can get several other types of power mosfet (from scrap switching power supplies). My question is what is the main parameters that you look for in order to choose a Mosfet for SEWA or OTA type amplifier?
Thanks
Edgardo.
Ready to build an OTA.
MOSFET:
Voltage: 60-200V
Current: 20-60A
VGS(th): 2-4V
Gfs:5-20S@10-20A
Ciss: below 2000pF
RDS(on) below 0,2ohm
PD:150-250W
Rth(JC): below 1'C/W
See if you can find any the are similar to these parameters.
I'm using the IRFP140A from fairchild at the moment. 😉
Voltage: 60-200V
Current: 20-60A
VGS(th): 2-4V
Gfs:5-20S@10-20A
Ciss: below 2000pF
RDS(on) below 0,2ohm
PD:150-250W
Rth(JC): below 1'C/W
See if you can find any the are similar to these parameters.
I'm using the IRFP140A from fairchild at the moment. 😉
Balanced SEWA
Just build two and drive each half with a balanced signal. Attach the loudspeaker between the outputs. If you match the MOFETS you might be able to delete the outputcaps 😉
(Even if you don't get a perfect match you can adjust the DC outputvalue by parallelling resistors across R1 or R10)
If you are doing this I would build it with a 2x18VAC trafo and 3A bias (R12-16=1R). This will give you close to 20W on 8ohm speakers. (4ohm speakers not recommended -Better to build a stock with 30V rails and 3A bias)
Should be a interesting experience on 2.order harmonic signatue vs 3.harmonic.
Just build two and drive each half with a balanced signal. Attach the loudspeaker between the outputs. If you match the MOFETS you might be able to delete the outputcaps 😉
(Even if you don't get a perfect match you can adjust the DC outputvalue by parallelling resistors across R1 or R10)
If you are doing this I would build it with a 2x18VAC trafo and 3A bias (R12-16=1R). This will give you close to 20W on 8ohm speakers. (4ohm speakers not recommended -Better to build a stock with 30V rails and 3A bias)
Should be a interesting experience on 2.order harmonic signatue vs 3.harmonic.
MOSFETS (QFETS)
Fairchild semiconductor carries lots of nice MOSFETS for SEWA and OTA.
They are generally very generous with samples to diy'ers.
Why don't you try their sample program? I'm shure they'll send you 4 MOSFETS in a hurry 😉 Don't abuse the system though, or else this sample policy will get cancelled (like TI has done with several of their audio-chips).
Take a look at:
FQA32N20C
FQA19N20C
FQA28N15
FQA33N10
FQAF44N10
FQH44N10
http://www.fairchildsemi.com/sitese...0//200&domains=fairchild_db:part_number&text=
😉
Fairchild semiconductor carries lots of nice MOSFETS for SEWA and OTA.
They are generally very generous with samples to diy'ers.
Why don't you try their sample program? I'm shure they'll send you 4 MOSFETS in a hurry 😉 Don't abuse the system though, or else this sample policy will get cancelled (like TI has done with several of their audio-chips).
Take a look at:
FQA32N20C
FQA19N20C
FQA28N15
FQA33N10
FQAF44N10
FQH44N10
http://www.fairchildsemi.com/sitese...0//200&domains=fairchild_db:part_number&text=
😉
Good for you! (And the rest of us, come to think of it..) Looking forward to doing that extensive listening test again? 😉
Hi Mads!
Oh, no more!😀 I want just listen music!
I have one "interesting" story: last week I was in a big cave (called Baradla, and it is one of the biggest in Europe) and listened some music in the "concert" cave. That was realy amazing!!!! The acoustic was unbelievable! Now I have to build a cave or I will go to be a cave-man.... 😀
When will be your WEB page operating?
Greets:
Tyimo
VIIaudio RULEZ!
Oh, no more!😀 I want just listen music!
I have one "interesting" story: last week I was in a big cave (called Baradla, and it is one of the biggest in Europe) and listened some music in the "concert" cave. That was realy amazing!!!! The acoustic was unbelievable! Now I have to build a cave or I will go to be a cave-man.... 😀
When will be your WEB page operating?
Greets:
Tyimo
VIIaudio RULEZ!
Tyimo said:
Sounds like a ear-opening experience 😀
Isn't it operating?
My website is just a hobby, like designing audio electronics/pcbs and listening to music etc. I don't have plans (only dreams) for any commercial applications for VII Audio. I'd have to quit my day job to pull something like that off. I was really considering it though, after I first listened to SEWAr1. But then I decided it would be much more fun to share it with you guys 😉 I find it all worth while when I get such positive feedback like I did from you, Tyimo
I do build amps for people here in Trondheim, but only by word of mouth/for friends etc. I don't really have much time to design new stuff for the time being, so I have just posted designs that I like, and that I have found to "make the music come alive".
I'm tinkering with my website when I get the chance (and when I'm not bulding something or listeing to music). Also, I don't know anything about website-design, so I have to figure it out as I go along. It's a work in progress and I will try to get some more info/desciptions on the projects up there. For now, only the schematics (and the ability to get pcbs) are operational. I admit, one would have to be a little experienced to take advantage of this, but all the info you really need is already on the website. Under the pcb section I have posted the BOM's, so one can figure out what parts to use for the projects etc. I don't think I will go deep into the details of the designs though, they are all pretty simple/easy to understand. Very basic, only they are implemented on high performance pcbs, keeping the signal and current loops as short as possible. It's amazing how good performance one can get from a simple circuit.
I'd like to keep the page really simple and clean, like it is now, only with more info/pictures of course. My idea is that one should easily find the info one is looking for, and nothing else.
I like to keep things as simple as possible (but no simpler, like a wise man once said).
PS -I'm going away over the weekend 🙂