MDAC First Listen (part XXVIII)

[arthur]

Why do you think you need to do that?

It would save messing about with attenuation resistors and all sorts of hassle.

It isn't just Adams that require attenuation.

Ps, I'm sure Ive made some daft conceptual error here.

Hard to see how sticking attenuators on the end my XLR cables can be anything but detrimental even if only a tiny bit.

Still awesome mind, but obviously ( or I wouldn't be here ) I want the very best sound possible from what I have.

But so far as I remember the mdac2 is going to sort out the attenuation issues. So by the spring it'll all be groovy anyway. )

 

[JohnW]

arthur,

The MDAC is designed to output the industry standard 2V RMS (2.2V Rms).

There are many factors such as Amplifier Gain and speaker sensitivity that determine the total system gain - what I cannot understand is why the Adams which have control of both of these factors still end-up with such high gain levels - I cannot image any common situation in today's world that would require anywhere near this level of gain - especially in a studio environment.

As the MDAC has been designed to meet the industry standard gain levels its not easy to reduce this without significant challenges.

 

[arthur]

Cheers John. I was desperately looking for a solution

I have no idea why Adam do this. The gain is ENORMOUS.

You could run the things from an iPod to 747 take off levels of decibels.

Quite daft. Damn good speakers otherwise.

 

[JohnW]

An interesting Power amplifier with XLR inputs on Ebay:-

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=261326023141

MOSFET, 200W per channel - a good starting point for a system

EDIT:-

Oh - taking a closer look its not a MOSFET design but appears to be an IGBT..... a form of Bipolar / Transistor... Erh, best avoided...

Shame as the it has all the ingredients to have been a good decent unit

 

[Steven Toy]

I like GamuT stuff.

 

[JohanH]

An interesting Power amplifier with XLR inputs on Ebay:-

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=261326023141

MOSFET, 200W per channel - a good starting point for a system

Hello John,

A quick glance at the schematic shows it's only balanced in the first stage; there's capacitors and an opamp in the signal path. For me not a first choice. Still it might sound good.

Cheers,
Johan

 

[JohnW]

Hello John,

A quick glance at the schematic shows it's only balanced in the first stage; there's capacitors and an opamp in the signal path. For me not a first choice. Still it might sound good.

Cheers,
Johan

Shame as it has all the ingredients, still I'm sure it will sound better then most in its price range... what else is there around at this price point...?

Nobody say the 8200MB's

Do you have a link for the Schematic ?

 

[JohanH]

Do you have a link for the Schematic ?

http://elektrotanya.com/gamut_d200_sch.pdf/download.html

You have to wait a bit until "Get Manual" appears below the preview

 

[JohnW]

http://elektrotanya.com/gamut_d200_sch.pdf/download.html

You have to wait a bit until "Get Manual" appears below the preview

Thanks

Oh dear - taking a closer look (and despite whats been stated on the Ebay listing) its not a MOSFET design but appears to be an IGBT..... a form of Bipolar / Transistor Hybrid ... Erh, best avoided...

Shame as the it has all the ingredients to have been a good decent unit

 

[PhilCTTE]

Shame as it has all the ingredients, still I'm sure it will sound better then most in its price range... what else is there around at this price point...?

Nobody say the 8200MB's

Oi ! Taking the p out of my amp again

Back in the day, TMA owners thread with Dr Zucker & co, it was highly regarded.
Douglas Self was the engineer. Everyone raved on about it. I believe it was well over twice the price of Audiolab retail price . I managed to get them at half the current rrp . So thought it was worth a punt. I,ve heard that Audiolab have put a smaller transformer in place , apart from that I believe they are the same.

I needed a solution as the Mamps are far off from production.

 

[mcai7et2]

Shame as it has all the ingredients, still I'm sure it will sound better then most in its price range... what else is there around at this price point...?

Nobody say the 8200MB's

Do you have a link for the Schematic ?

With some (minor) diy requirement, the Hypex ncore and ucd amps (with the associated switch mode psus) are amazing. I doubt anything comes close for less than twice the price.

Fully balanced too

 

[Tonyb]

I paid 750 eur for my Parasound recently. I saw an A21, which is the successor to my 2200ii, for sale in London recently for £800, looks like alot of vfm to me. I am enjoying it immensely. A friend of mine replaced his Accuphase E-560 (I think) with one (plus a surprisingly good pro audio DAC - thats another story) saved some money and is very happy, it just delivered the crescendos even better. Trying out his convinced me. The A21 is a bit more transparent at lower volumes and even more dynamic (what!). But I'd be interested to have any other opinions, and the expert opinion of the 1994 era circuit. "The output stage of the amplifier is a set of six parallel bipolar output devices. A single MOSFET pre-driver in source-follower configuration drives the output stage" so is that MOSFET or bipolar? Whats the characteristic of the bipolar that you would describe John? If I could figure out how to attach the pdf of the schematic..

 

[Obi1]

My understanding is that mosfets give you a more valve like mid and top, but also a bit of a slow, wet bass response.

That was also my reflection changing from a mosfet Rotel amplifier (RMB100) to a bipolar based Rotel (RMB1095) The mid and high is now a little bit sharper (in a good way, imo) with more details and the bass response is a lot better, with more control and a deeper bass.
This could of course be the result of other stuff than just the transistor type, more than a decade has passed between the two amps and I would suspect that Rotel picked up a thing or two in that time.

My taste seams to be leaning more towards amplifiers with bipolar transistors than mosfets, at least based on the limited samples I have had at my disposal.

 

[Tonyb]

That's close to what I noticed moving from a Creek mosfet to the Parasound (at the levels where they could be compared, before the Creek ran out of puff). The sound did perhaps blanche slightly though, the Creek had slightly saturating effect, which was also nice.

The 1095 is quite an impressive looking beast, but perhaps not ideal for the MDAC though, it seems you would have a few spare channels .

 

[Achim]

Hi John,

as I understood it, you recommend driving ones headphones from the XLR outs connecting pos/neg on the cans to pos/neg on the balanced outs, not using the balanced ground, right?

Isn't this equivalent to running the signal through an 2:1 expander, thereby leaving the area of "fidelity"? Not that I advocate against, whatever sounds good is right.

Cheers,
Achim

 

[Obi1]

That's close to what I noticed moving from a Creek mosfet to the Parasound (at the levels where they could be compared, before the Creek ran out of puff). The sound did perhaps blanche slightly though, the Creek had slightly saturating effect, which was also nice.

The 1095 is quite an impressive looking beast, but perhaps not ideal for the MDAC though, it seems you would have a few spare channels .

I am actually using all channels, bi amping my front speakers, and using the fifth channel for my centre speaker when I feel like enjoying a movie. The M-DAC actually suits the Rotal as a glove IMO, bringing some wormth the the sound without loosing any details and not to forget dig out the last of the deepest bass without loosing the control. I love this combination in my system.
The old Rotel mono amps are now serving my surround speakers some much needed power.

 

[JohnW]

Oi ! Taking the p out of my amp again

Ohhh Somebody noticed

Well one things for sure, atleast your Bass is tight and firm like...

Heres a great live recording that I use to test that the systems Bass "gels" read as "times well", foot taping etc ...

Sadly is MP3 so you can hear the MD/HF getting"Messy" when it gets complex... but still a great recorded Bass line / drum kit, gets my little speakers going...

 

[JohnW]

I've ordered the bulk foil resistors for -20ab and -30db attenuation. They will be delivered directly to you. I'm still sourcing a suitable xlr adapter.

Michael

Michael,

Your resistors arrived (470R + 1K5) - just need the adaptors...

 

[LarsS]

Using this not very enjoyable disc to test/verify systems, covers total spectrum in music - - > http://www.elusivedisc.com/THE-ALL-STAR-PERCUSSION-ENSEMBLE-DXD-CD/productinfo/GSDX002/

 

[JohnW]

Hi John,

as I understood it, you recommend driving ones headphones from the XLR outs connecting pos/neg on the cans to pos/neg on the balanced outs, not using the balanced ground, right?

Yes - correct.

Isn't this equivalent to running the signal through an 2:1 expander, thereby leaving the area of "fidelity"? Not that I advocate against, whatever sounds good is right.

No, it does not work how you describe, it drives the headphones deferentially (As a bridged amplifier) - thus provides twice the power, but at all levels and frequency - its totally linear, just twice the power.