Thanks for the link Pavel!
But this poor English only speaking fella is lost. I recognise the layout and price info.
We need parts available in North America. A very good case for a kit type offering since the parts are hard to obtain in North America. I am not asking for a kit, I am merely pointing out potential problems with what are common parts in some areas being unobtainium in other areas.
However, we will adapt and make it work. Someone may redesign the amp PCB later anyway. I still think everyone did a fabulous job in designing this amplifier.
-Chris
But this poor English only speaking fella is lost. I recognise the layout and price info.
We need parts available in North America. A very good case for a kit type offering since the parts are hard to obtain in North America. I am not asking for a kit, I am merely pointing out potential problems with what are common parts in some areas being unobtainium in other areas.
However, we will adapt and make it work. Someone may redesign the amp PCB later anyway. I still think everyone did a fabulous job in designing this amplifier.
-Chris
I also bought this one /should be on stock/, it is in english, worldwide delivery:
http://rswww.com/cgi-bin/bv/rswww/s...egfkcefeceefdffhdglj.0&cacheID=ukie&Nr=avl:uk
stock number 467-8483
Regarding previous link, there is an English flag (top right)
http://rswww.com/cgi-bin/bv/rswww/s...egfkcefeceefdffhdglj.0&cacheID=ukie&Nr=avl:uk
stock number 467-8483
Regarding previous link, there is an English flag (top right)
Chris, i could send you a bag full of Wimas, it would be a matter of days...
What confuses me, Wima does have distributors in NA/CA...
http://www.wimausa.com/EN/distribution_int.htm
But these links all go to brokers.
Mike
What confuses me, Wima does have distributors in NA/CA...
http://www.wimausa.com/EN/distribution_int.htm
But these links all go to brokers.
Mike
Hi Pavel,
You did give me an idea though Pavel. A surface mount component may solve these issues, also for the silly little mica cap if I build more. The last link did that for me.
This will wait for a future parts order. I've ordered from four places to get all my parts so far.
-Chris
So there is! I didn't recognise it for what it was. Thank you.
You did give me an idea though Pavel. A surface mount component may solve these issues, also for the silly little mica cap if I build more. The last link did that for me.
This will wait for a future parts order. I've ordered from four places to get all my parts so far.
-Chris
This one looks great: (2.2uf 5mm lead pitch, Evox)
http://rswww.com/cgi-bin/bv/rswww/s...cchaddhljeegfkcefeceefdffhdglj.0&cacheID=ukie
Chris, 4 different places ? Digikey has nearly everything... (except this inputcap)
Mike
http://rswww.com/cgi-bin/bv/rswww/s...cchaddhljeegfkcefeceefdffhdglj.0&cacheID=ukie
Chris, 4 different places ? Digikey has nearly everything... (except this inputcap)
Mike
Hi Mike,
Thanks, but not yet.
I am thinking of modifications already. With a Fet input pair, the 1uF may be just fine. R10 I will experiment with as well. I'd like to see a higher impedance there, shouldn't cause too much of an offset problem. I can compensate in the feedback network as well to balance the impedance on each side.
I lean toward higher input impedances and smaller caps. A DC servo later will allow me to get rid of the cap in the feedback network too. That may make a large improvement in sound quality, only by comparing will I know for sure.
Mike, have you measured the DC offset with a short in C10's place?
-Chris
Thanks, but not yet.
I am thinking of modifications already. With a Fet input pair, the 1uF may be just fine. R10 I will experiment with as well. I'd like to see a higher impedance there, shouldn't cause too much of an offset problem. I can compensate in the feedback network as well to balance the impedance on each side.
I lean toward higher input impedances and smaller caps. A DC servo later will allow me to get rid of the cap in the feedback network too. That may make a large improvement in sound quality, only by comparing will I know for sure.
Mike, have you measured the DC offset with a short in C10's place?
-Chris
Hi Mike,
I wanted to try polystyrene caps and a few other things.
Your amp will keep me busy for a while while I explore possibilities. First I want to try it stock. I can forgive a little bass roll off. The mids, highs and dynamics are what I am looking at.
My reference amps include tube front end hybrids, tube amplifiers and some solid state amps. The critic is my wife (poor thing! 😉 ) and a couple associates. I can never trust myself as I will have biases. But, when something is really good, it really hits you. Although simple in design, your component choices and layout show promise (in my mind).
I will attempt to install some surface mount caps if I can find them Mike.
-Chris
Edit: I have to find a good supply network after being out of the business for almost 10 years. I know what I want, but can't always find it these days.
I wanted to try polystyrene caps and a few other things.
Your amp will keep me busy for a while while I explore possibilities. First I want to try it stock. I can forgive a little bass roll off. The mids, highs and dynamics are what I am looking at.
My reference amps include tube front end hybrids, tube amplifiers and some solid state amps. The critic is my wife (poor thing! 😉 ) and a couple associates. I can never trust myself as I will have biases. But, when something is really good, it really hits you. Although simple in design, your component choices and layout show promise (in my mind).
I will attempt to install some surface mount caps if I can find them Mike.
-Chris
Edit: I have to find a good supply network after being out of the business for almost 10 years. I know what I want, but can't always find it these days.
Hi Chris, i have not tried to omit C10, the problem is that it serves 2 things, block dc into the 500ohms, giving a balanced 22k impedance to the diffamp bases AND reducing gain to unity for DC. It's likely that DC-offset get's horribly high without c10 as it is a non symetric input stage. Even with a perfectly balanced/matched amp you will get a dc-offset at input of ~40mv, amplified by 40 (the gain) to 1.6v ! 
You see, C10 reduces DC-offset ~factor 1000. Without the thermal inbalance in the current mirror DC-offset would be 0mv.
With higher input impedance things get even worse. I chose the 22k as it was the highest value before inputimpedance would fall above 10khz.
If you use jfets in the input things get very different of course. With them you might also emit c1, but is risky.
Mike
You see, C10 reduces DC-offset ~factor 1000. Without the thermal inbalance in the current mirror DC-offset would be 0mv.
With higher input impedance things get even worse. I chose the 22k as it was the highest value before inputimpedance would fall above 10khz.
If you use jfets in the input things get very different of course. With them you might also emit c1, but is risky.
Mike
Mike I will build your amps again...
Can you make new layout ??
With your pcb layout ....
- I can not put other caps at input, like WIMA MKP4, Solen, hovland
- 5 Watt Resistor wire sometimes is to short.... so i can not put in board.....
- 1/4W resistor is too small, if we want use RIKEN/ROEDERSTEIN ( 1/2W)
- mica/ceramics caps is too small to...
Can you make new layout ??
With your pcb layout ....
- I can not put other caps at input, like WIMA MKP4, Solen, hovland
- 5 Watt Resistor wire sometimes is to short.... so i can not put in board.....
- 1/4W resistor is too small, if we want use RIKEN/ROEDERSTEIN ( 1/2W)
- mica/ceramics caps is too small to...
Hi Mike,
I'm guessing an offset of around 325mV if everything is matched, assuming an hFE of 450 for the MPSA18. You are are correct that the offset scales up with higher resistance for R10. Well within the range of a servo. I could inject a current to correct that like they did in the old days.
Things are different with JFets for offset, but that's not the primary reason I am interested in them.
I'd never omit the input cap. Not my style at all!
Aside from lifting foils, the worst thing I can do is blow it up. Since I built it, I'd have to fix it. A fitting punishment, don't you think? 😀
Anyway, all of this is premature. I can't wait to hear the amp in it's stock form.
-Chris
I'm guessing an offset of around 325mV if everything is matched, assuming an hFE of 450 for the MPSA18. You are are correct that the offset scales up with higher resistance for R10. Well within the range of a servo. I could inject a current to correct that like they did in the old days.
Things are different with JFets for offset, but that's not the primary reason I am interested in them.
I'd never omit the input cap. Not my style at all!
Aside from lifting foils, the worst thing I can do is blow it up. Since I built it, I'd have to fix it. A fitting punishment, don't you think? 😀
Anyway, all of this is premature. I can't wait to hear the amp in it's stock form.
-Chris
dytln_02 said:
Folks 😉 ,
how about being more independent and try to work yourself, the best way how to improve your skills??
Michael has done incredibly much work for you on this project and this is a neverending chain of requirements ...
Hi Pavel,
I agree 100%. Mike and yourself have done an amazing job for all of us. Added to that is the troubleshooting Mike has done for non-working projects. I don't think we can ask for more.
I think if people want to experiment with this amp, they should. Report their results here as well. You have a great place to start and use as a reference.
Mike, could you use a rest? 😉
-Chris
I agree 100%. Mike and yourself have done an amazing job for all of us. Added to that is the troubleshooting Mike has done for non-working projects. I don't think we can ask for more.
I think if people want to experiment with this amp, they should. Report their results here as well. You have a great place to start and use as a reference.
Mike, could you use a rest? 😉
-Chris
Hi dytln, changing the pcb for bigger c1 is easy, there is plenty of space, you don't need to use a 1000v film cap here, most filmcaps have spacing of 22.5mm. If you want to use high end resistor you could use the "Vishay-Dale CMF-55", they fit. But i am not convinced that you hear a difference, normal 1% metal film should do the job, noise isn't an issue anyway.
Feel free to modify the pcb unless you do not make changes to the layout itself.
Hi chris, the inputoffsets with mpsa18 are 33mv (hfe of ~1000),if you omit c19, inputoffset changes on the fb-side to ~0.75mv giving a difference of 32mv. With the gain of ~40 you have ~1280mv dc-offset at output. But a DC-servo should be able to take care of that. I have the feeling that removing c19 will not change much, bypassing it with 100nf film cap already removed the elyt sound. But i look forward to your results !
Interesting is to remove c20 (the bypass cap), this gives a sweet/lovely terribly colorized sound. Some like it...
The parts in the feedback network are the most sensible ones.
Mike
Feel free to modify the pcb unless you do not make changes to the layout itself.
Hi chris, the inputoffsets with mpsa18 are 33mv (hfe of ~1000),if you omit c19, inputoffset changes on the fb-side to ~0.75mv giving a difference of 32mv. With the gain of ~40 you have ~1280mv dc-offset at output. But a DC-servo should be able to take care of that. I have the feeling that removing c19 will not change much, bypassing it with 100nf film cap already removed the elyt sound. But i look forward to your results !
Interesting is to remove c20 (the bypass cap), this gives a sweet/lovely terribly colorized sound. Some like it...
The parts in the feedback network are the most sensible ones.
Mike
Hi Mike,
Interesting things to think about. I can't locate C20 on the schematic, but I'm still looking. Ah, your web site. C12 on the 5.4b diagram. I don't think I'd remove that one! I can see how it would change the sound. Ever try a larger film cap in there to swamp out the electrolytic more?
Later I want to pull R1 and R26 and run the front end off it's own regulated supplies.
I will keep you posted on what I try out and how your amp reacts.
Thanks Mike!
-Chris
Interesting things to think about. I can't locate C20 on the schematic, but I'm still looking. Ah, your web site. C12 on the 5.4b diagram. I don't think I'd remove that one! I can see how it would change the sound. Ever try a larger film cap in there to swamp out the electrolytic more?
Later I want to pull R1 and R26 and run the front end off it's own regulated supplies.
I will keep you posted on what I try out and how your amp reacts.
Thanks Mike!
-Chris
I guess you meant R31/32 ? Running the frontend from it's own supply should give better dynamics and bass response.
To which schematic do you refer ?
Mike
To which schematic do you refer ?
Mike
😀
Part locators shifted between rev's.
5.4b is the diagram I was looking at. R31/R32 on your web site.
I would expect better dynamics, lower noise and lower distortion. The bass notes would be the worst offenders since they are usually at a higher level. Complex musical passages should sound better. That's just in general, I have no idea how this amplifier would react to that.
Normally I'd run a couple volts higher than the high current supply. Overload recovery would be the thing to watch there. 8R and 4R loads may be different (I bet).
-Chris
Part locators shifted between rev's.
5.4b is the diagram I was looking at. R31/R32 on your web site.
I would expect better dynamics, lower noise and lower distortion. The bass notes would be the worst offenders since they are usually at a higher level. Complex musical passages should sound better. That's just in general, I have no idea how this amplifier would react to that.
Normally I'd run a couple volts higher than the high current supply. Overload recovery would be the thing to watch there. 8R and 4R loads may be different (I bet).
-Chris