Aksa 100W-N Complete!

Lost81 · « **Reply #20 on:** 22 Jul 2004, 10:19 am »

Quote from: MattCassidy

On a slightly different note, earlier in the day I went to do the final check on the bias after 20 mins of loudish music. The heatsinks were appreciably warm, however when I went to measure the bias, rahter than being around 48mV as suggested in the Gospel according to Hugh, it was up around 65 on the left and 67/68 on the right, hmmm.. I left it for the recommended 10 minutes idling and the values were still quite high. I re-adjusted the bias to 55, left it for a few more minutes, confirmed it was still 55 and put it all back together and headed over for the test. Sounded great!

I suspect that when i set the initial bias the amp was not warm enough (it was a cold night) as I remember the heatsinks were not very warm at all.

Would this be a likely explanation?? as to why the bias was a bit high? Do I now need to do the 20 minute thingo again?

Sounds like my experience while setting up bias too.
2 of my monoblocks behaved like that.
As I remember, those were particularly cool nights too...

-Lost81

AKSA · « **Reply #21 on:** 22 Jul 2004, 12:58 pm »

Yes, Matt, Benny,

The initial set point is crucially dependent on device temperature, reflected in the heatsink temperature.

Winter will thus be a little different to summer.

This is why it is necessary to turn it on, cycle through some music for a time, get it warmed up, then set the bias at equilibrium. Anything less will be rather too dependent on ambient temperature.

Cheers,

Hugh

MattCassidy · « **Reply #22 on:** 22 Jul 2004, 09:21 pm »

hmm, i certainly did play some music for quite a while, however it must have been pretty cool as those heatsinks did not warm up too much, at the time I put it down to incredibly big heatsinks and a cool running amp. oh well no harm done, the thing sounds beautiful! and is now set up correctly!

Lost81 · « **Reply #23 on:** 22 Jul 2004, 09:33 pm »

Hmm, slightly OT here.

I am assuming that when we swap resistors out, it is a good practice to go through the gauntlet of re-testing and re-biasing the amplifier, no?

Since even the same value (as marked) resistors have different measured values (correct me if I am wrong, but that's how I comprehend the concept of tolerance % on the resistors).

I think the extra care is worth it.
Won't want to fry your speakers there...

BTW, anyone ever pitted the tantalum resistor vs. the Vishay S102?

The general impression I have received from reading about the tantalum resistors is that they "sound glorious," while the S102 is hawked as "most transparent."

That sounds like 2 very different things. If I am not mistaken, Riken Ohm carbon-film ceramic resistors "sound warm" because they are current-sensing (?) to a certain degree, thus adding 2nd and 3rd harmonics. That is very different from being "transparent" (i.e. adding or subtracting from the signal). I wonder what does "sound glorious" actually mean...

Cheers,
-Lost81

MattCassidy · « **Reply #24 on:** 23 Jul 2004, 08:59 am »

Quote from: Malcolm Fear

>>Shunt volume.
Normally on a pot, the signal goes to pin 1, the output comes from pin 2 and the earth is pin 3.
With a shunt, the input goes through a 30K resistor, then to pin 3, then to output.
Pins 1 and 2 are joined together and go to earth.

There is nothing like a new hobby to make you feel stupid..

Malcolm I now have my pot, and two one what 27K resistors..can you clarify the above, input (ie hot) bit of the RCA to 30K resistor, then pin 3 then where? If pin 2 and pin 3 are joined then there are no more pins..

sorry if this is a dumb question.

Greg Erskine · « **Reply #25 on:** 23 Jul 2004, 11:45 am »

Matt,

Have a look here. I have found this site very good in explaining things.

http://www.goldpt.com/how.html

My guess is looking at figure 1
Rin = 27K
Rg = your pot connected as a variable resistor

Hope it helps
Greg

kyrill · « **Reply #26 on:** 23 Jul 2004, 12:30 pm »

hi 81

I have put tantalums on the AKSA 25 for every R in the signal path and then some.Same values of course and it measured the same on the DMM.

I have not put the thantalums on the AKSA 55 for the mid and bass units.
However for all AKSA's I have replaced the R18 and R20 the big white 5W resistors with thick carbon film resistors (5 W) SO they have a (non) sound of their own.

In due time I will give a report. I was especially interested in the "tube like " sound of the tantalums.

What brand are the "normal" metal film resitors of the AKSA's?
They are not riken ohms are they?

AKSA · « **Reply #27 on:** 23 Jul 2004, 10:13 pm »

Kyrill,

You have taken exotica to new heights, and I will be very interested in your school report......

The standard metal films in the AKSA are Beyschlag, a German company who have been making their resistors in Czech Republic for many years. Just six months ago Beyschlag was bought by Vishay, an Israeli company who over the last decade have bought Draloric, Dale, Roederstein, Sfernice and a couple of others whose names escape me. In about five more years they will doubtless own the entire Western passive components industry, such is their expansion. Of course, the oriental passive industry control all the Japanese and Chinese markets for consumer goods; the Riken, Rohm and various other Japanese companies are actually fairly small producers who concentrate on quality.

Cheers,

Hugh

MattCassidy · « **Reply #28 on:** 26 Jul 2004, 08:42 pm »

Hi Malcolm and Guys,

I put in the pot control set up as a shunt, it seems to work pretty well. I have not tested it with a proper listen as yet. I currently have a 27k resistor in line with the hot. The volume control is backwards which i guess stands to reason since it is wired backwards..

A couple of minor issues came up.

1. A slight buzz has appeared, is this interference from the AC? Any possible solutions. I am not too worried as this is a temporary measure until I get the GK-1 built..

2. As Malcolm suggested may happen it is a bit of a touchy control. a fraction of a turn goes from inaudible to a bit loud.. so do I put in a bigger resistor? What happens if there is no resistor?

Thanks for your help (especially Malcolm)
Matt

AKSA · « **Reply #29 on:** 26 Jul 2004, 11:30 pm »

Matt,

If the pot range is very limited, and you need to turn it in the opposite direction (CCW) to increase volume, then you have the left and right pins on the pot interposed. Swap 'em over. Ground and conjoined wiper should be on the right side, looking at the terminals on top with the shaft facing towards you, and the 27K in line series element should be connected to the left side.

Buzzes are usually traced to inductive pickup around the volume control wires; keep them as short as possible, and try to enclose them all in a metal shield of some kind if possible.

Hope this is helpful,

Cheers,

Hugh

MattCassidy · « **Reply #30 on:** 26 Jul 2004, 11:38 pm »

Thanks Hugh,

I was thinking about taping my wires down with some of that metallic tape, whaddayareckon?

As for the pot being backwards it is curious, with the shaft facing me looking down on the pins the two right pins (pins 1 and 2) are joined and are the earth and the left (pin 3) is the hot with the resistor..I will swap them around anyway and see what happens.

What do you think with the "suddeness" of the volume situation?

Matt

AKSA · « **Reply #31 on:** 27 Jul 2004, 12:15 am »

Matt,

The 'suddeness' will be remedied if the pins are swapped over; you have the steep end of the audio taper, so volume changes at this end are abrupt.

Let us know......

Hugh

Malcolm Fear · « **Reply #32 on:** 27 Jul 2004, 07:27 am »

I initially set up my pot (DACT) arse about. At minimum volume setting it was at full volume. Turning the volume up (clockwise) reduced the volume.
If the volume increases as you rotate the volume, the thing is set up correctly.
What are you using for a pot?
What value?
Is it logarithmic or linear (it should be logarithmic)?
I kept increasing the resistor (I think it is now about 34K).

MattCassidy · « **Reply #33 on:** 27 Jul 2004, 09:56 am »

Thanks Malcolm and Hugh,

I ahve now rewired around the other way and am pleased to report that it is a nice smooth transition in volume and is the right way round, also the buzz seems to be gone. Still sounding great can finally use it with a proper source.

Thanks again for the help!

Matt

MattCassidy · « **Reply #34 on:** 27 Jul 2004, 10:47 am »

Sorry Malcolm forgot to answer some q's. It is a 20K logarithmic pot, with a 27K resistor. It is all working just dandy now, goes nice and soft and goes good and loud too. Sounds good either way. Any man who wants more than this is a greedy man.

kyrill · « **Reply #35 on:** 27 Jul 2004, 02:20 pm »

Quote from: MattCassidy

....Any man who wants more than this is a greedy man.

You mean, not so modest as I am

Malcolm Fear · « **Reply #36 on:** 27 Jul 2004, 04:28 pm »

Greedy man indeed.

Now you need to start experimenting with brand and type of resistor.
I have only compared Redio Shack (Jaycar) resistors with a Riken Ohm. I love the Riken Ohm.
I will be interested in other peoples comments on other types, like the tantalums.

kyrill · « **Reply #37 on:** 27 Jul 2004, 07:00 pm »

AH, what else can I do, then trust my intuïtion ?
I do believe a transformer is a better sounding volume device than a shunt resistor(s) DACT or Goldpoint ( I think Goldpoint is better than DACT)See http://www.stevens-billington.co.uk/page102.htm
If you like Andyr and others want to follow the ultimate route (within reason of course)

I cannot follow that route against my feelings as I have the digital volume device inherent of the DEQX, but no complains as of yet

MattCassidy · « **Reply #38 on:** 27 Jul 2004, 08:38 pm »

If i keep experimenting with resistors and DACT's, transformers it will just delay me from building the GK-1. So for a temporary solution it is doing nicely. The Aksa sounds much better than my Marantz PM7200 which it is replacing. So I am happy.

Matt

kyrill · « **Reply #39 on:** 27 Jul 2004, 11:07 pm »

hi Matt
Everything in the right context of course.

MAybe one day Hugh will release a Nirwana+ for the GK-1
The difference will be greater than for the AKSA's

Just teasing
Kyrill