Simple Killer Amp - Listening impressions

[ShinOBIWAN]

Re: Hi ShinOBIWAN,

Can you tell us some more about the music you played to evaluate the amps, besides Andreas Vollenweider'.
Did you play classical music and live-recordings.
Now you heard the amps what is your opinion on the Hurbert his review in the first post of this thread.

I listen to a large variety of music and the amp didn't favour anything in particular. The only thing it really lapped up was the great quality recordings but that's true of any amp or component.

Huberts review sounds right on the money to me.

You evaluate the amp as the best DIY amp you heard, does that imply you have heard better (commercial brand) amps ? If so which commercial amp do you regard better and in what aspects.

Thanks Henk.

That's a thorny subject and one I'm going to avoid because all the really top notch commercial stuff I've heard was at hifi shows or dealers. So there were different rooms, equipment and speakers all of which make any meaningful comparison impossible.

 

[macka]

There have been requests to post some more close - up pics of the wiring.

I will do so shortly.

macka

 

[richie00boy]

Interesting stuff. Just wondering if you ever got round to giving the P101's a listening test and if so was it a/b against any other amp?

Also, have you used the same PSU for all these amp tests?

 

[ShinOBIWAN]

Interesting stuff. Just wondering if you ever got round to giving the P101's a listening test and if so was it a/b against any other amp?

Also, have you used the same PSU for all these amp tests?

Hi Rich

Yes I've used all three diy amps that I've tried now with exactly the same PSU's - the BMM M2010R1:

http://www.bmm-electronics.com/Product.asp?Product_ID=3310

Also, I've never done an AB with the P101's.

 

[beppe61]

Here's my thoughts on the SKA after spending a several hours listening to it in the comfort of my own home.
...
Things can only get better!

Dear Sir,
thank you so much for your great review !
It leaves no doubt about its quality indeed.

Kind regards,

beppe

 

[richie00boy]

Thanks. Did you listen to the P101 at all? With the BMM PSU? If so what were your impressions?

 

[ShinOBIWAN]

Thanks. Did you listen to the P101 at all? With the BMM PSU? If so what were your impressions?

Had the P101's up and running for around 5 months before I sold them on and that was with the BMM supplies.

The P101 is a good amp, though I wouldn't rank it in the same class as the SKA.

 

[richie00boy]

Thanks again. I assume the P101 is also deficient compared to the AKSA? Would you say that the deficiencies are the same deficiencies compared to AKSA and SKA? Or would you say P101 compares to AKSA and SKA in different ways?

 

[beppe61]

Hi Rich
Yes I've used all three diy amps that I've tried now with exactly the same PSU's - the BMM M2010R1:
http://www.bmm-electronics.com/Product.asp?Product_ID=3310
Also, I've never done an AB with the P101's.

Dear Sir,

please excuse me Sir but I looked at the site and could not find the model number of the transformer.
It seems to me that the kit is about the diodes bridge and filter caps PCB.
Could you please tell me the actual transformer you used (in order to get its specs)?
By the way also the amp kit on the bmm-electronics site look intriguing and well done.

Thank you so much indeed.
Kind regards,

beppe

 

[ShinOBIWAN]

Thanks again. I assume the P101 is also deficient compared to the AKSA? Would you say that the deficiencies are the same deficiencies compared to AKSA and SKA? Or would you say P101 compares to AKSA and SKA in different ways?

Its all rather difficult to quantify, especially when tastes in presentation differ so much.

The AKSA and SKA are from two opposite spectrums, one introduces low order harmonics intentionally and the other aims to eliminate any type of distortion, the P101 also shared this same philosophy. What's clear to me is that the SKA doesn't actually sound like your typical low distortion amp, its definitely not etched and forced like the P101 was.

The P101 seemed a little on the edge in its presentation and I've spoken with another builder (still4given) who had similar thoughts. It just wasn't as natural as the AKSA & SKA or at least not to my ears.

I'd rate them as:

1. SKA
2. AKSA 55N+
3. P101

 

[ShinOBIWAN]

Dear Sir,

please excuse me Sir but I looked at the site and could not find the model number of the transformer.
It seems to me that the kit is about the diodes bridge and filter caps PCB.
Could you please tell me the actual transformer you used (in order to get its specs)?
By the way also the amp kit on the bmm-electronics site look intriguing and well done.

Thank you so much indeed.
Kind regards,

beppe

I assume you are talking about what toroidal's I used in conjunction with the BMM M2010R1 PSU?

If so, I used these types for the AKSA 55N+:

http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9531920&N=401

And these ones for the SKA 150w:

http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9532013&N=401

I've also just paid Greg for a pair of 300w SKA's and have also ordered these:

http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=4334826&N=401

 

[hifryer]

ShinOBIWAN,

I see you prefer 50V for the GB300D. Are you going to share the 500VA tx across both channels or use 2 x 500VA tx????

The later would seem very much overkill.

Depending on your speaker load, I would have thought 48V adequate / safer??

Cheers

 

[beppe61]

I assume you are talking about what toroidal's I used in conjunction with the BMM M2010R1 PSU?
If so, I used these types ...

Yes Sir,

that was my question exactly.
Thank you so much again for your very kind and valuable reply.
The choice of the transformer is one of the fundamental step to build a great amp IMHO.
Once I experienced a clear improvement changing only the main transformer with one with a better regulation factor.

Thank you sincerely again for your extremely kind disclosing your personal valuable experience with us.

Kind regards,

beppe

 

[ShinOBIWAN]

ShinOBIWAN,

I see you prefer 50V for the GB300D. Are you going to share the 500VA tx across both channels or use 2 x 500VA tx????

The later would seem very much overkill.

Depending on your speaker load, I would have thought 48V adequate / safer??

Cheers

I think that your right Hifryer.

Greg recommends a maximum 75v rails for the GB300, so a 50-0-50v toroid is pretty close to that.

 

[HiFiNutNut]

Because Harbuch Electronics at Hornsby was mentioned I may put in my 2 cents.

I have a total of 6 transformers made by Harbuch. 4 or them are custom made. They are excellent (although quite expensive). The 2 stock items are cheaper, however, hum slightly when there is no load!

By the way, I recently bought a dozen of the Nipon-Chemicon 10,000uF 75V computer grade capacitors at an unbelivably low price from www.ledeaudio.com and tried them and they sound excellent on my power amp. They are substantially better than some Marcon caps I previously had and I can't tell the difference in sound quality comparing to the Vishay 100V computer grade capacitors (very expensive at Farnell selling nearly AUD$90+ each but with nearly the best possible specifications). I subsequently bought another dozen. So here are my 2 cents if you are also looking for PSU caps.

Regards,
Bill

 

[Greg Erskine]

Because Harbuch Electronics at Hornsby was mentioned I may put in my 2 cents.

I have a total of 6 transformers made by Harbuch. 4 or them are custom made. They are excellent (although quite expensive). The 2 stock items are cheaper, however, hum slightly when there is no load!

Hi Bill,

Can you tell me a little more about the hum with no load. Do you mean when connected to 240V without anything on the secondaries the actual toriod makes a noise. I have a Jaycar toriod that buzzes even with a load but I haven't noticed a noise from any of the Antrim toriods. I'd like to test them to make sure.

BTW: What VA are they? and are they the black labelled ones?

regards

 

[KLe]

KLe
What I know,
Greg (amplifierguru) will not reply in this thread.
But you can find him at another diy forum.
Regards

Hi lineup
I posted it on the forum,as suggested, and this was Greg's response. Just to share ...

Hi KLe,
whew! here goes -
1. The amplifier is complementary throughout. The input differentials are complementary BJT, the driver stage is complementary Class A 250MHz BJT, and the output stage is complementary common source MOSFET. Even the input stage current sources and thermal comp are complementary. Sexy, hey?
2. The input BJT pairs are matched to 5% on current gain to minimise DC offset particularly in DC couple mode.
3. The output MOSFETs are matched in a custom jig to 10mV on Vgs on to facilitate equal sharing of load current in conjunction with their internal resistance.
4. The amplifiers are designed to function on nominal 4-8 ohm loads and are Vgs limited to limit maximum currents in untoward situations.
5. The amplifier has been optimised for low bias Class AB operation with residual distortions well contained below 0.005% and inaudible at normal levels, but can be biassed up to Class A operation of 1/3 the power rating on suitable lower continuous duty supplies for those who need it. I have not experienced any audible benefit.
6. The topology with the power efficient common source output stage can swing to within 2V of the supply rails so, in conjunction with the high PSRR of the design , can perform with lower supply voltages and capacitance for a given power output over conventional designs. The difference is typically 30% - making this a very lean, green performer.
7. 250VA for the GB300D is about the minimum I would suggest for full output on one channel, typically 300VA. If the power output is reduced this could be reduced further without detriment.

Hope that helps.
Cheers,
Greg

Hi ShinOBIWAN
Excellent review. Can I ask a couple of questions ...
1. What size transformer are you using per module?
2. What is the load impedance of your speakers?

thanks

 

[audiofan]

Does somebody have any experience with the following supplier:
Abra-electronics.com

I think transformer # TRF 330 should be a fair choice for a 100W monoblock.

 

[HiFiNutNut]

Greg,

I initially purchased 2 Harbuch transformers (60-0-60V 625VA) via www.ledeaudio.com (David is an ex-Radio Australia engineer who also designs a lot of amplifier circuits for the professional audio world). I had another two 40-0-40 625VA transformers pulled out from my old amplifier boxes. I think they are Antrim. One of them is starting to hum slightly after one year service. I have been building a tri-amp system therefore am in need of 3 power amplifiers.

Right before last Christmas I decided to build the Aikido line preamp by J.B. and a 12B4A line stage so I ordered 2 smaller transformers from Harbuch, made to specifications including screen, etc. I also decided to change all 3 amplifiers into 3 dual monoblocks for the Christmas so to rush the stuff I ordered an additional 2 x 45-0-45 625VA directly from Harbuch.

Harbuch charged between AUD$110 to $160 for each of those Toroidals. All of them work very well except the 2 x 60-0-60 transformers. When connected to the PSU without connecting to the amplifier circuits, the transformers hum slightly, like a brand new low noise refrigirator. It is the mechanical vibration. I am pretty sure that the transformers are firmly bolted down to a 25kg chasis. Still the noise is annoying.

Peter is the engineer at Harbuch Electronics. Initially they built my smaller transformers wrong. After negotiation, Peter was trying his best to get them rewinded for me before Christmas just within 2 days. I was quite impressed by that.

Would I go back to Harbuch Electronics? I think so but I will have to talk with Peter to ensure that any Transformers I will get won't hum like those 2 out of 6!

Looking from outside, the Harbuch transformers are much better than the Antrim.

Regards,
Bill

 

[AndrewT]

Hi Hifinut,
could the noisy transformers be suffering from DC on the mains supply?
Maybe they are more susceptable to the small amount of DC that periodically comes in and would benefit from a DC blocker.