New Aleph 30 In Progress

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Blues

Blues

Member
Joined 2003
Mark,

Tough but nice looking A30 you built...but can't keep it to yourself huh? Wait for the HotRod Aleph board before building your own. Just remember to put a hoodscoop on the top cover instead of the shotgun-shot cover we usually see;) Did you utilize R1* and R8* in matching q1 and q2?

Allan
 
H

highbias

Member
Joined 2004
Hi Allan,

No I haven't had the need to utilize those resistors... I just match the input pair very closely. Its really pretty easy and I've matched up over 100 IRFP 240's and about 50 9610s so far. I bought these large batches from Digi-Key back when I built my 2's. I have a Racal 5 1/2 digit DVM that I use and I generally try to match at least as close as the factory does(.01v or better) on the input devices. So far all the amps I've built, the 3, a pair of 2's and a Mini all have less then 5mv offset. I know the 30 utilized the ability to tune with different resistors in those positions but I have not needed to so far and doubt that I will. Having a pot in there or being able to change them easily would make matching less critical for those that don't know how or that don't have the equipment to do it.

The best sounding amp so far(and by a considerable amount) is the Aleph 3.... its simply a very amazing amp!! The dynamics, soundstaging, depth, and high end resolution are something that you have to hear to believe... Its pure magic and doesn't sound like a 30 watt amp. I will be building one for myself as the next project.

To those that are still considering which Aleph to build I reccomend the 3 unless you have VERY inefficient speakers... the 3 drives my Dynaudios to very loud levels with out any strain at all.

Mark
 
jacco vermeulen

jacco vermeulen

Member
Joined 2004
wuffwaff said:
I´ve got some 2mH torobar chokes from intertechnik
William
Click to expand...

I think the torobars are rated at some 600VA.

In the 80's i built my first loudspeakers.
For the filters there was a choice of coils, the latest then was the Zero Ohm coil.
As it looked like an ordinary transformer i wondered what the clue was.
Later i swapped from ic regulated powersupplies for preamps to C-R-C with Hiraga as example.
The voltagedrop and dissipation bothered me so i stepped over to batteryfed.
At that time i read an article on a choke filtered power amplifier, for my power amplifier i had just gone over to 2955/3055 regulated supplies.
I even considered submarine batterycells(see my stats), at 500lbs per volt/side and considerable maintenance that was a nono.

Anyway, i did some experiments with chokes.
As my bedlay is a medical specialist i had access to big chokes wrenched from derailed hospital fysiotherapy running excercisors
( "Loopband" in Dutch, not a clue for the English word, Zero in Dutch is "Nul", hence my translation to Aleph Zero lately).
The chokes are part of the inverter section for controlling the motor speed, originally at 10mH and 0.10 Ohm.
(I can post a picture if someone is interested).
For loudspeakers i used them with succes, it seemed like a nice thing for the powersupply of an amplifier because of the low voltage drop and little dissipation.

As i have a love thing with toroids for a long time i wanted to try toroids for chokes for the obvious reasons.
The rule for powersupply toroids is preferably 3 times output level, i quote Mr Pass.
With Caps a voltage safety margin is desirable, 10-15% minimum, according to the conservatives.
As a toroid choke should not reach saturation for the reason William uffWaff mentioned it is logical to use oversized chokes, reasons above.
I have used the torobars, even in parallel mode, it is a lot cheaper at 15-25$ each than air coils, at 50% of its power spec.
The only downside i have read of so far is the distortion figure for toroids, but with powersupplies that seems of no interest in my view.

Currently i am thinking of trying to wind chokes from round toroid cores, Magura has a thread for a group buy on that.
Maybe someone has a pointer for obtaining the proper bell wire ?
( wikkel/schelledraad )

Just for mentioning it, i started building 6 Alephs( for which i am using my 24 300VA toroids) to make an 8-Aleph amped system with an active crossover.

For Zero Cool=>
It has 48 times 78000 uF Mallory's ~ 3.75 F, nanananananah !!

I am thinking of hooking it up to the heating system of the floor with a bypass and an extra waterpump for cooling.
In my previous house i added an extra waterpump and an aircon system at construction of the heated porcellanato livingroom floor, during winter the floor was heated, during summer cooled.
 
A

arold19

Member
Joined 2002
For the aleph 30 !

I have two 1.8mH inductor at home that I don't use.
Do you think this will make any difference if I put in the power supply ??? In the original Pass Labs Aleph30, it doesn't have inductor....and the sound seem wonderful.

I will have a 20v+20v transformer.... so about 29V dc... a couple of lost by the charge... baybe 26 or 27... If I am a couple volt over the +-25V, I plan to use my two inductor if you think that it is a good idea!

thank!
 
Yugo

Yugo

Member
Joined 2004
LC vs CL

wuffwaff said:
Hi Yugo,

these post talk about choke inputs wich is not the same as a PI-filter. This means that the findings on sound differences can´t be used here.

william
Click to expand...


Hi wuffwaff,

you are right.But I only wanted to ilustrate that some inputs (LC or CL)sound different in diferrent circuits (tube or SS,amps or preamps);different chokes (toroid or EI) exibit different sound etc.
And of course on post 51 the member talks about how he had made his toroid chokes.

Regards,
Yugovitz
 
keypunch

keypunch

Member
Joined 2004
MOSFET Matching

highbias said:
Hi Allan,

No I haven't had the need to utilize those resistors... I just match the input pair very closely. Its really pretty easy and I've matched up over 100 IRFP 240's and about 50 9610s so far. I bought these large batches from Digi-Key back when I built my 2's. I have a Racal 5 1/2 digit DVM that I use and I generally try to match at least as close as the factory does(.01v or better) on the input devices. So far all the amps I've built, the 3, a pair of 2's and a Mini all have less then 5mv offset. I know the 30 utilized the ability to tune with different resistors in those positions but I have not needed to so far and doubt that I will. Having a pot in there or being able to change them easily would make matching less critical for those that don't know how or that don't have the equipment to do it.

Mark
Click to expand...

Mark,

Could you explain your matching process? I have access at times to Fluke 8840A/AF, Racal-Dana 6000, HP 973A and Fluke 8012A/AD. Any reason you need 5 1/2 digit meters to match to 0.01 accuracy? Seems to me you just need to match to 0.001 accuracy.

I have seen many articles on MOSFET matching. Some elude to need to test at different currents or voltages, some suggest need to allow device warm up times, etc. All these suggestions seem due to efforts made to match and then once devices are installed in the amplifier there seems to some definite measured mismatch well off measured prior matching measurement efforts.


Regards,

John L. Males
Willowdale, Ontario
Canada
12 January 2005 15:01
 
wuffwaff

wuffwaff

Member
Joined 2001
Hi,

one cause for strange results when matching fets is the way you connect your measuring equipment. I tried to measure the 45 IRFP240´s for my Aleph-X the day before yesterday. All went fine until I tried to measure a few of them for the second time and got slightly different results. And when measuring the third time they were again a bit different. I took quite a long time before I found out that the probes connected to my voltmeter (sort of crocodile clips) were not really making contact like they should. I also connected the power supply with these and somehow they are not suited for "large" currents (1.2A in this case).

After cutting up a few wires with bananaplugs and soldering them directly to the measuring/power supply point everything was alright. When measuring 3 times the same fet the maximum deviation was below 0,01V. (I took the value after 10 seconds):

william
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
if you don't have enough knowledge and few measuring gadgets - to decide is choke good enough for purpose , then only way is to put it in situ ( presumed position ) and measure/feel is it warm/hot too much , while working ........


let's say that 50C on surface is Final Frontier ........... :clown:
 
M

markd514

Member
Joined 2011
Zen Mod said:
if you don't have enough knowledge and few measuring gadgets - to decide is choke good enough for purpose , then only way is to put it in situ ( presumed position ) and measure/feel is it warm/hot too much , while working ........


let's say that 50C on surface is Final Frontier ........... :clown:
Click to expand...

I don't completely agree with the speculative approach. Thechoke is in the supply for filtering. How can you "measure" it to make sure it is doing it's job? There has to be a benchmark to measure with it in or out of circuit. Can we prove that there is less noise and ac ripple without it? THe same goes with filter capacitance. It is easy to say, "the more the merrier", but to what point? Cost is a factor, but taking that out of the equation and creating a circuit based purely on performance, there is still some point of diminishing returns. I guess you can "load" the circuit down and test for ripple. I just want to know what others think about this from a design standpoint. What is the maximum "load" that an amp will draw? A
 
R

Russellc

Member
Joined 2003
Paid Member
markd514 said:
I don't completely agree with the speculative approach. Thechoke is in the supply for filtering. How can you "measure" it to make sure it is doing it's job? There has to be a benchmark to measure with it in or out of circuit. Can we prove that there is less noise and ac ripple without it? THe same goes with filter capacitance. It is easy to say, "the more the merrier", but to what point? Cost is a factor, but taking that out of the equation and creating a circuit based purely on performance, there is still some point of diminishing returns. I guess you can "load" the circuit down and test for ripple. I just want to know what others think about this from a design standpoint. What is the maximum "load" that an amp will draw? A
Click to expand...

Well, I guess the alternative is to build it, buy the "gadgets" and measure it.
myself, I'd listen to ZenMod who has built many, many of these devices and has probably forgotten more than many of us know...:cool: I would think measuring the completed PS would give your answer, you could try with choke, and without. Some around here speak of downloadable software that lets you build them on your computer screen and gives predictions? This might be another way.

Russellc
 
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