[amb]

Quote:

Originally Posted by SDA Quick question, are there many headphones that sound better out of a 75-ohm adapter? I'm considering giving this amplifier a separate 75-ohm output just for the sake of variety.

I am of the opinion that inserting resistance inline with the headphones is detrimental to the performance, but apparently some phones out there are designed to work best with some resistance in series (this is why the Meier Corda amps have two outputs, one direct and one via 120 ohm resistors). 120 ohms is also a "standard" that few companies seem to adhere to. At any rate, I won't advocate it, and it's up to you to experiment.

 

[rjkdivin]

Quote:

Originally Posted by SDA Err, unfortunately, there's one more thing. Setup of G and R channels seems to have gone well enough, but the voltage across R5L stays around 17mV no matter how I adjust BIASOPL. I'm guessing I have a short or something, where should I start looking?

So, you are able to adjust G and R to exactly 0.5v across R5? But when you adjust BIASOPL the voltage across R5L does not vary from 17mv at all....no movement?

Oh...I see you solved the problem....enjoy!

 

[wistily]

My modest build:

M3 with AD8610AR, a gain of 11, and a 24V Steps.
Since it's my first diy build (not only electronic), i'm pretty proud of it. I havn't still got my DT880 back (2 month 1/2 at Beyer grrr), so i won't comment on sound, but i'm already happy with it.
The electronic part was very easy to build but so wasn't the enclosure.
Thank you amb and morsel for you nice amp, i hope there will be other top quality, easy to build projects available from you in the future (who said a nice dac? I know, i'm dreaming).

 

[DigiPete]

Nice job wistily! congrats!

I am using DT880s with my M³ and love it! I think you will be pleased. I am using the OPA627s with my amp.

Cheers
DigiPete

 

[xAPaperBoy]

I agree, the DT-880 and the M³ sound awesome together.

Now if I could just choose which op-amp I like best with this combination. Let's see, I have:
AD825's
AD8610's
AD843's
AD845's
OPA627's
OPA637's

AMB and Morsel recommend the AD8610's. Some have commented that they like the OPA637 (L&R) and OPA627 (G) best -- much better than the OPA627 (L,R,&G).

Honestly, I don't know what I prefer!? They all sound good.

 

[Finch&Music]

I am planning the building of an M3 and am in the process of choosing and gathering components. In the Netherlands that is not so easy, I have to make several stops to get a complete inventory for the M3. Some things comes from USA, others from Germany, others from local shops. But that is part of the fun.

I have some practical questions about yes or no using the possibilities of the 'bassboost-section'. Not using saves money also, but I want to go for a quality choice within the context of my reproduction chain.

My M3 (with premium components) will be used with a Sennheiser 650 or a AKG K1000. May be in the future there will be an additional headphone, but that will be a quite neutral balanced one. As a source I will be using a Njoe Tjoep 4000 (a heavily modded Marantz 4000 with severe upsampling and a tube outputstage) or an older Philips transport with several modded external dac's. The first source has a output gain control of itself, the others presents a fixed outputsignal to the M3. The reproduction chain is primarily used for classical and jazz music (and some 'classical' rock) extracted from mostly good to outstanding recordings.

Is there in such a chain in the practice of listening to music a usefull benefit to have a bassboost available for a little compensating for some not so good balanced recordings?

Or is it much more convenient to have a variable gaincontrol on board of the M3, so you can seek your most usable gainrange for the usable settings of the volumepot?

Or is it in practice only exceptional that you use the extra possibilities? I have already seen that there are some builders of the M3 that have not been using the bassboostsection at all. I am interested in the arguments for omitting the possibility. Do they miss something in reality or do they already feel the temptation to modify their configuration afterwards?

When I choose for the possibility of a continuous variable gaincontrol (that is f.e. with an alps in combination with a dact attenuator): can I expect that with the alps in such a function I can compensate for the often heard complaint with a stepped attenuator that the steps are too coarse in practice? Or should I choose another way to overcome that?

Greetings,

Pieter.

 

[morsel]

Bass boost is a matter of personal preference. I like bass boost for enhancing bass weak recordings, of which there are many. Some people don't want to spend the extra money, or don't want to be tempted to tonally alter the original recording in any way for any reason. With the bass boost pot all the way down it does not affect the sound at all, so it will not hurt to include it. The K1000 is bass-shy, all the more reason to include bass boost.

A variable gain control should not be necessary. A switch to choose between low and high gain should be sufficient in the case of using both efficient and inefficient headphones. Note that changing the gain control resistors affects bass boost response. It is better to increase R3 (to 2 or 3k) than reduce R4. Since the K1000 and HD650 are both inefficient you will probably not need any gain control.

I believe complaints about stepped attenuators having steps that are too coarse are due to gain set too high for use with efficient low impedance headphones.

Good luck with your M³.

 

[meat01]

Just got my amp back in its new enclosure. I had someone build me a nice wood enclosure and I am happy how it looks. I used a tread as the power supply. Here are some pictures.

 

[SiuGuyGuy]

I had built a M3 a running with good result

Now i want to try make it to push speakers, as recommended config from amb's web site. I had made a power supply with a Nuvotem Talema 0050P1-2-030K(50VA, 2nd 15-0-15VDC). I would like to ask is this transformer ok to run with speaker?

I just want to have a try first, and will source a bigger VA transformer if get good result. So just want to know if my 50VA is able to run it.

My power supply config is LM317 + LM337, outputing 26V (+13V & -13V). and speaker is jmlab706s(8ohm, 90db)

Thanks for reply first!

 

[SiuGuyGuy]

btw, meat01's amp is very impressive

 

[amb]

SiuGuyGuy, 50VA is big enough for speaker use. However you should upgrade the voltage regulators in your PSU. The problem is, there aren't many high-current negative regulators to choose from. Is there a reason why you're using dual regulators? I would suggest using a single LM338 regulator, adequately heat-sinked and adjusted to the voltage you want.

The PSU's bridge rectifier may also need to be upgraded, depending on what you have.

Note that a PSU voltage of 26V is going to restrict output voltage swing and the amp will clip at around 2W into 8 ohms.

Search this thread for keyword "speakers" to see previous discussions on this topic.

 

[steel]

Hi AMB

I just start build M3.
some part are Difficult to find.
can i use VISHAY CPF2 on R9?
http://www.vishay.com/docs/31021/cpf.pdf

thanks

 

[morsel]

You can use any 2W metal film resistors that will fit. The CPF2 is fine.

 

[Jaypetermen]

Does anyone know of additional suppliers for the 100uf/35V ELNA Cerafines or of an alternative bouquet cap for C4 and C5?

 

[steel]

Quote:

Originally Posted by morsel You can use any 2W metal film resistors that will fit. The CPF2 is fine.

Thanks...

Is this a good idea for R9?
to solder as a frame.
i guess it will be hot