Simple Killer Amp - Listening impressions

Status
Not open for further replies.
Jump to Latest
#381
macka said:
Did more evaluations last night.

Removed/ shorted C9, some improvements to the midrange issue I noted earlier but its has a mif range bloom.

I am wondering about the bootstrap caps, I'll try another variety.

Macka
Click to expand...

Hi Macka

I've just soldered in some 100uf standard Blackgates at C4 and C5 that I took from the AKSA when I did the parallel Blackgate type N mod. They were too big to fit on the component side so I mounted them underneath. No listening done yet but I've got two modded channels and two standard to do a comparison when I have more time (probably this weekend).

Careful with C9, you can end up rolling off the bass response with values smaller than 47uf.
 
#383
"I have always wondered which is the best alloy for soldering operations.
Is 95.5Sn/3.8Ag/0.7Cu the best alloy available ?
I use normally a 62Sn36Pb2Ag alloy .
Which is the optimum temperature for the iron soldering tip?
I am very interested about this.

Thanks a lot.
Regards,

beppe"

Beppe, sorry for the delayed reply; been a bit busy.

The composition I quoted is for lead-free solder. It has a melting point of 217C. Tip temp for it is 350-450C.
99Sn1Cu has a higher melt temp of around 227C, so is more aggressive on the bit. Also it doesn't flow as well, and looks duller.
The material you've mentioned is normal lead bearing solder, the silver addition slightly lowers the eutectic temp from 183C to about 179C. Excellent solder, commonly used in SMT paste, but unfortunately will be banned in most products (with certain exemptions) from 1st July 2006 (RoHS legislation)
Interesting question is where the DIY fraternity stand. No doubt those who build and sell to much of the world will have to conform. Difficult to police the DIY mob. Probably, though, all our components will be lead free anyway so might as well go there.

Brian.

(Plain Mr, but I for one appreciate your politeness; it's becoming a lost art)
 
#384
Originally posted by Pingrs
Beppe,
sorry for the delayed reply; been a bit busy.
1) The composition I quoted is for lead-free solder.
It has a melting point of 217C. Tip temp for it is 350-450C.
99Sn1Cu has a higher melt temp of around 227C, so is more aggressive on the bit.
Also it doesn't flow as well, and looks duller.
2) The material you've mentioned is normal lead bearing solder, the silver addition slightly lowers the eutectic temp from 183C to about 179C.
Excellent solder, commonly used in SMT paste, but unfortunately will be banned in most products (with certain exemptions) from 1st July 2006 (RoHS legislation)
3) Interesting question is where the DIY fraternity stand.
No doubt those who build and sell to much of the world will have to conform. Difficult to police the DIY mob.
Probably, though, all our components will be lead free anyway so might as well go there.
Brian.
(Plain Mr, but I for one appreciate your politeness; it's becoming a lost art)
Click to expand...

Dear Mr.Brian,
no problem at all and thank you sincerely for your extremely kind and valuable reply.
1) Thank you for the info. I have always been worried in someway by the solder's smoke for health reason.
Not that I solder so much by the way.
2) Actually I find the alloy I use very practical and easy to use.
I like it very much.
I am sorry to hear that will be banned.
Maybe with some precautions it would be possible to go on using it for small work.
3) I understand the problem.
I hope that this lead free alloy will be easy to use as well.

Thank you again.
Kind regards,

beppe
 
#388
Hi Upupa,
Next direction of " green brains " will be " ecolgical leadless bulets " for submachine guns...
Click to expand...

We are ready shooting bismuth in shotgun shells. Lead shot is illegal to use. Darn, I have a lot. In a tribute to Darwin, maybe I can salvage the powder and primers. 🙄

So if you get shot with bismuth, will it cure your heartburn? :angel:

-Chris
 
#390
Hi Upupa,
what do our " ecological leadless cars " with green vegetatin all along highways
Click to expand...
You mean those useless cars full of lead-acid batteries? They generally drive at least 10 Km below the average traffic speed in the passing lane. The drivers always look very happy with themselves.

-Chris
 
#391
No Chris, I mean oxigen nitrides... In my country you can see along highways rusty coniferous trees, which is caused by HNO3, which originate from oxigen nitride... And do you mean, that it is problem ? No, " oil lobby " is strong and people are stupid and like drive a cars....
 
#392
Upupa Epops said:
Next direction of " green brains " will be " ecolgical leadless bulets " for submachine guns... 😉
Click to expand...

I guess the problem is that we now use and throw away very large quantities of all kinds of stuff with cheap, essentially disposable electronics - stuff can can't be economically repaired when it breaks. That stuff goes into landfills and lead leaches out over time. I would guess that lead free is not so much of a problem for manufacturers, given the high levels of automation and process control. For us clumsy DIY'ers low melting temp and poor process control makes leaded solder easier. And we hope to make nice projects that don't end up in a landfill in a couple of years.

Sheldon
 
#393
Hi All
Another friend listened to my GB300D based system, on Sunday (now about 30 hours of run in), and I asked him to write a summary of his listening experience. This was his experience ... :cubehead:


Dear KL

Firstly, let me thank you for introducing me to the GB300D. I had only read about it in the various audio forums and was very interested to hear it for myself. The following is taken from notes I made whilst auditioning the amplifier at your place, I was also able to compare this to the notes I had made at other listening sessions we had had with your previous (and highly regarded) amp.

My first impression was of an incredible smoothness to the music, certainly the best I have heard to date. The next impression was the total abscence of any sense of speaker location. When doing a critical listening session I always do so with my eyes closed in order to focus better on the music and these two features positively lept out at me immediately.

At first I thought the soundstaging was a little narrow, then another CD was played and the soundstage was well beyond the width of the speakers and had futher depth as well. This amp really shows up any flaws in the recording as you can clearly hear if the recording engineer has done his/her job properly. Dynamics were sensational as well, but yet again, the quality of the redording is paramount to getting the best dynamics. People who get this amp will certianly be searching for audiophile quality CD's as there is the quality there to show up whatever signal the amp is fed.

Now onto the various levels of the musical spectum. Bass was clean and clear, definitely not a one note bass amp, this one. It was very easy to discern the bass was played on either an electric or accoustic guitar. Mid range was exceptionally smooth and all the instruments played within this range were there right in front of you. Treble was also very good but perhaps not as prominent as your previous amp.

One feature I always look for is the quality of reproduction of the piano as this is the instrument I play. I can report that the GB300D has the honour of being the best I have heard to date. Prior to taking up playing the piano I had always found the reproduced piano music lacked a lot and it was only on hearing it played live that I found what rich harmonics this instrument has. As you would know the piano is a large instrument and this is because it has a large sound board in order to produce it's beautiful tones and harmonics, I am pleased to say that the GB300D is easily the best I have come across, well above all previous amps.

Lastly, I had an unusual experience during the latter part of the listening session, as mentioned before, I had my eyes closed whilst listening and at some stage I started visualising the group in front of me. I know critics have written of this before but it was my first experience of this and I found it quite startling to have this happen to me.

All in all an exceptional amplifier.

best regards
Ian
Click to expand...

mine still to come
:cheers:
 
#394
ShinOBIWAN said:
Hi Macka
I've just soldered in some 100uf standard Blackgates at C4 and C5 that I took from the AKSA when I did the parallel Blackgate type N mod. They were too big to fit on the component side so I mounted them underneath. No listening done yet but I've got two modded channels and two standard to do a comparison when I have more time (probably this weekend).

Careful with C9, you can end up rolling off the bass response with values smaller than 47uf.
Click to expand...

Hi ShinOBIWAN/Macka
I think that C9 is same as C19 on the GB300D, ie. the Feedback cap to ground.
That being the case, I just have this feeling that it should be twice the size, ie. approx 100uF, or even larger :att'n:

The reason for this is electrolytic distortion. I can't remember the complete reason for this distortion, without doing some reading/researching. :dead:

What do you think?
rgds
 
#395
Hi,
I don't know the circuit values for the GB amps but it is often recommended that the RC time constant for the NFB loop is between 60mS and 120mS.
Keeping the RC at this value usually results in a tiny measurable voltage across the capacitor.

D. Self gave some numbers for DC blocking caps and in that section he reported that ensuring minimum AC voltage across these caps reduced the distortion that otherwise would be generated. His recommendation was to use a cap about ten times bigger than you would expect for audio frequencies. My interpretation on this is to use 1Hz to 2Hz as a roll off frequency instead of 10Hz to 20Hz and that happens to get you into almost flat response and low phase error at 20Hz.
 
#396
BOLD STATEMENT

my opinion based on my experiene is that:

ANY electrolytic cap any value in signal path / feedback loop seriously degrades the sound - even most film caps arn't that great.

So I suggest instead of adjusting, think of removing ... 🙂
 
#397
Hi all
My friend, Ian, has since emailed me and reported the following criticism
I do have one criticism in that I felt it lacked some "sparkle" in the top end.
Click to expand...

As good as the amp is, it would appear there is still more that can be done, to extract absolutely everything from this amp.

I am using standard GB300D amp modules, but, ShinOBIWAN and Macka are modding their GB300D's.

So ShinOBIWAN and Macka, we await your reports of the mods.
:cheers:
 
#398
Re: BOLD STATEMENT

mikelm said:
my opinion based on my experiene is that:
ANY electrolytic cap any value in signal path / feedback loop seriously degrades the sound - even most film caps arn't that great.
So I suggest instead of adjusting, think of removing ... 🙂
Click to expand...

Hi mikelm
This is the FB to Gnd cap. Do you think that the cap can be removed without any DC problems arising?
:cheers:
 
#399
AndrewT said:
Hi,
I don't know the circuit values for the GB amps but it is often recommended that the RC time constant for the NFB loop is between 60mS and 120mS.
Keeping the RC at this value usually results in a tiny measurable voltage across the capacitor.

D. Self gave some numbers for DC blocking caps and in that section he reported that ensuring minimum AC voltage across these caps reduced the distortion that otherwise would be generated. His recommendation was to use a cap about ten times bigger than you would expect for audio frequencies. My interpretation on this is to use 1Hz to 2Hz as a roll off frequency instead of 10Hz to 20Hz and that happens to get you into almost flat response and low phase error at 20Hz.
Click to expand...

Hi AndrewT
Thanks, you are right. I am not sure about the factor of 10, but, that would imply that the FB to Gnd cap should be somewhere between 200/470uF.
:cheers:
 
Status
Not open for further replies.
Top Bottom