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Mini A Board Run

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#61
mpmarino said:


I'm pretty sure I have some toroids that are:
-Amveco Magnetics
-Prim: 120V 60HZ, 258VA
-Sec: 57 VCT or 28.5 VCT @ 4.68A
-potted center
-new in box

I think the secondaries are 57v ct with 'mid taps' at 28.5v, so I think you could use either voltage but at only 4.68A regardless of voltage.
The higher voltages could be good for small AB or gainclone too??

If anyone is interested I'll get one out, plug it in and make a couple of measurements to confirm voltages. I could sell 'em at 20 bucks ea. usd plus ~$10 flat rate shipping in US.

Marc
Click to expand...

I wonder if they would work. HUmm..
 
#62
I am 'pretty sure' they are wound like this:
 

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#64
Forgive me for my questions - I'm a total noob 😀 I searched, but couldn't find anything:

Is SMD really that difficult? I see a lot of people saying even normal soldering is tough; I just soldered for the first time in my life - a gainclone - and it was very simple. All of my joints look perfect. I also used a $3 iron 😀

Can someone tell me what the differences between the Mini-A and the Aleph 30 are? I know the Mini is 10w, whereas the 30 is 30w. How about price differences between the two? And, these are both Class A amps? Told ya' I was a noob 🙂
 
#65
cheeba said:
Forgive me for my questions - I'm a total noob 😀 I searched, but couldn't find anything:

Is SMD really that difficult? I see a lot of people saying even normal soldering is tough; I just soldered for the first time in my life - a gainclone - and it was very simple. All of my joints look perfect. I also used a $3 iron 😀

Can someone tell me what the differences between the Mini-A and the Aleph 30 are? I know the Mini is 10w, whereas the 30 is 30w. How about price differences between the two? And, these are both Class A amps? Told ya' I was a noob 🙂
Click to expand...


I responded to your email Cheeba. You might want to buy a better soldering iron one that is tempature controled for smd and other styles. Also you might want one that has a esd protection. a basic radio shack one wont help you from esd 🙁 spend 100$ or maybe get a weller off ebay. having a good multimeter and good soldering iron are the first pieces of equipment you want to have.

Smd is not that hard it just requires a steady hand a nd a esd controled soldering iron.
 
#67
imin-A input attenuation

welcome back Jason - a quick and probably noobish question for yourself or Brian / Mark

any suggestions on best method to install a fixed amount of input attenuation on the mini-A board? I'm using the amp as a reference in A/B testing of speakers and amps;and with the signal level from either my CD player direct or from the tubed linestage, it's way to sensitive.

Due to the physical layout of the map, I'd prefer not to use volume pot(s), and would prefer a simple resistive LPad at the input; to start with at least 6 if not 10dB would provide the required degree of system volume control

thanks
 
#68
Reading Glasses With Metal Frames...
Click to expand...

Hehe, I'm with you on this. I had my eyes lasered, so now I can use a camera without wearing glasses. And instead of having only one pair of expensive glasses, I have a pair of el-cheapo reading glasses in every room. Another that stays in the car, and yet another that I leave at work.
 
#69
I never wore glasses for my first forty yearsw on earth. Thank God they're a buck a pair. Every lamp shade is decorated with three pairs. Four pairs in the car. Countless on the boat and all over the shop. They last about 6 weeks before they fall off my head and I step on them. Sometimes I'll stack two pairs on each other giving 2.5 + 2.5 = 5 diopters. Good for SMD...

BUT WHY?
 
#70
Smd

I don't think that the Mini-A SMD board will be hard to build. The initial set of boards I built over a year ago were my first SMD soldering project.

I used 1210 sized resistors, which are quite large compared other resistors out there. I don't think that this project will be too difficult for a person who has soldered through-hole components before with success.

The BJTs on the pcb are through-hole now, as the SMD counterparts gave me troubles the first time around due to their limited power dissipation and small form factor.

The IRFP9610S devices are quite large also, which make it easy to solder.

For the 220uf caps, I left a choice for the user to use SMD caps (like on the earlier design), or through-hole caps, which will offer a wider selection of capacitors. The other capacitors (NPN compensation cap, feedback cap) are through-hole components.

I think that with a halfway decent soldering iron, a set of tweezers and some fine solder, a beginner should be able to complete this project.



On a side note, I never designed this project to be something that I would get a batch of boards made. I was in school, and had some spare space on the pcb I was getting made, so I decided that I would do a quick layout. I had never done an SMD layout, so I decided to do a simple one. The Mini-A caught my attention due to the simplicity of the design.

--
Brian
 
#72
Re: imin-A input attenuation

chrisb said:
welcome back Jason - a quick and probably noobish question for yourself or Brian / Mark

any suggestions on best method to install a fixed amount of input attenuation on the mini-A board? I'm using the amp as a reference in A/B testing of speakers and amps;and with the signal level from either my CD player direct or from the tubed linestage, it's way to sensitive.

Due to the physical layout of the map, I'd prefer not to use volume pot(s), and would prefer a simple resistive LPad at the input; to start with at least 6 if not 10dB would provide the required degree of system volume control

thanks
Click to expand...


Chris,

you can email me to get help with this.
also you can maybe take teh jumber out of the short between gnd and the munus side of the balanced connection it will drop the input level down.

jason @ zorby-audio dot com
 
#74
cheeba said:
Jleaman, I haven't sent you an email since we started the chassis buy...

Are there any benefits to using SMD in this case?

Anyone care to comment on the Mini vs. Aleph 30?
Click to expand...


Mini a V.S a3 only difference is $$$ and 15more watts of power. To build a A30 it costs about 3 x the price. Why you may ask. Heat sinks heat sinks and humm Heat sink's. A mini A with 20v rails will give you 15watts maybe more. PLENTY OF power. I run them on my towers Chris’b built and they are plenty of power. I would not go for more power if not needed..

maybe try a mini a and see..

Smd VS Through hole. I like the sound of the smd ones better. Closer tolerances and better sound. But that’s just my opinion.

Jase
 
#75
I have a few questions about parts for the SMD/through-hole...

The SMD parts are tighter tolerances, but what if one used somewhat higher grade components? Vishay/Dale resistors, Elna Silmic/Cerafine caps, etc.?

I am also wondering about the difference between the Mini-A and the A3/A30. Wouldn't the A3/A30 sound better (and have less distortion) by nature of having more output devices and thus lower output resistance? Would there be any notable differences if one used more output devices but lower current (as in, use all the extra parts for A30, but scale for a power output closer to the A-mini)? Thanks

(BTW- jleaman- I am probably the one whose email you responded to earler... 😉 )
 
#76
needtubes said:
I have a few questions about parts for the SMD/through-hole...

The SMD parts are tighter tolerances, but what if one used somewhat higher grade components? Vishay/Dale resistors, Elna Silmic/Cerafine caps, etc.?

I am also wondering about the difference between the Mini-A and the A3/A30. Wouldn't the A3/A30 sound better (and have less distortion) by nature of having more output devices and thus lower output resistance? Would there be any notable differences if one used more output devices but lower current (as in, use all the extra parts for A30, but scale for a power output closer to the A-mini)? Thanks

(BTW- jleaman- I am probably the one whose email you responded to earler... 😉 )
Click to expand...


U might have been the one that emailed me 🙂

Like i said above with the a30's and up they all cost much much more to build and get going. Heat sink's are not cheap these days and transformers are $$$ too.

To me a A30 is worth building if you have the heat sinks and transformer first.

I tried the mini a's Through hole with all dale resistor's not much difference. The smd one's do have a different sound tho. A sound that i like much better.

I only picked smd because they are smaller and sound better, i also picked mini a's because they are cheaper and sound the same as a a30 a30 has 15more watts thats it. Are you willing to spend 3 x the price for 15more watts ?

Jase
 
#77
needtubes said:
I have a few questions about parts for the SMD/through-hole...

The SMD parts are tighter tolerances, but what if one used somewhat higher grade components? Vishay/Dale resistors, Elna Silmic/Cerafine caps, etc.?

I am also wondering about the difference between the Mini-A and the A3/A30. Wouldn't the A3/A30 sound better (and have less distortion) by nature of having more output devices and thus lower output resistance? Would there be any notable differences if one used more output devices but lower current (as in, use all the extra parts for A30, but scale for a power output closer to the A-mini)? Thanks

(BTW- jleaman- I am probably the one whose email you responded to earler... 😉 )
Click to expand...

I don't agree that SMD parts have necessarily tighter tolerances. The cap placement on the board will allow for the Elna Silmic/Cerafine caps if they fit on the last revision of the through-hole pcb. Vishay/Dale also makes SMD versions of their resistors in the 1210 package (mouser sells them).

I simply see the SMD layout as an alternative approach. I have not directly compared the two amplifiers, as I only made 2 prototype channels, which were shipped to Jason before I finished my first regular Mini-A amp. The two prototype channels that I built also didn't have any matched components on them.

Once I receive the initial boards, we will run some comparisons, and also have others run comparisons, and we will see if there is much of a difference in the two different amplifiers.

As for the power of the amplifier, I personally would pick the lowest power solution that satifies the needs of your speakers, as the heat dissipation of these amps increases a lot as you increase the power level. I don't believe that the lower output resistance from paralleling multiple output devices will have too much effect on the sound.

--
Brian
 
#78
Thanks for clearing all that up... I was just wondering if having more devices would affect the sound/distortion levels drastically.

I am interested to know how a two-device (or is it one...?) output stage mini-A compares to the 10- or 12-output device Forte Audio 1A that I am currenly running. The Forte is an older NP design, and I think it is almost exactly the same circuit as the push-pull Class AB Forte 1, but rebiased to run full Class-A to 50 watts. It is a lot more power than I need, and the buzz in the left channel drives me crazy. But, it does sound nice... 🙂
 
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