El hilo del "Sapphire amp" ( Funcionando :-D )

[repente]

Me ha dicho el hombre que me enviará una version con mas ganancia para los hd800 y en general con auris de mas de 150 ohm.
Ya esta en marcha... 

[MadMardigan]

Pues el cacharrín tiene buena pinta, si encima le pones unos trafos chulos seguro que mejora!

[repente]

Si, "ya que nos ponemos"  voy a irme a por unos toroidy de los buenos.

¿Me recomendáis algun sitio de eBay, aunque sea en china, de confianza para comprar un potenciómetro Alps Blue?

[repente]

Voy que hay Alps con "Loudness" y sin ello. Uno con mas patillas que otro.
¿Cual sería el recomendable?

[repente]

Bueno, ya he ido pidiendo el resto de cosas.
La caja ganadora ha sido la que recomendaba el creador del circuito:




Entra todo bien, sale por 75 dólares con envío incluido, ya tiene los agujeros hechos, viene con el iec, cubre pote... etc y me parece bastante bonita a falta de poner los tornillos frontales en negro 

[maty]

Creo que has acertado con el Saphire, aunque yo hubiese elegido la actualización del O2 al ODA por agdr.

-> http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html

-> http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda.html

-> http://www.diyaudio.com/forums/vendors-bazaar/237226-parallel-njm4556al-two-stage-amp.html

[MadMardigan]

Pues la caja está realmente bien y te ahorras un curro por el hecho de venir ya con agujeros, IEC y eso. Te lo vas a montar en un plis plas!

[repente]

El O2 normal no sé si será igual a esta versión Desktop en cuanto a potencia; pero con los LCD2 se quedaba muy corto, supongo que con los HD800 será peor todavía.
En sonido no estaba mal, pero no me sorprendió la verdad, ¿Este mejora también en calidad de sonido?

[maty]

A cuenta de los op-amp intercambiables, acabo de leer lo siguiente en una tienda muy interesante:

Yulong Sabre A28 Fully Balanced Headphone Amplifier

-> http://shop.grantfidelity.com/Yulong-Sabre-A28-Fully-Balanced-Headphone-Amplifier.html

The amplification of Yulong Sabre A28 is OPAMP driven complementary transistor buffer (also known as “Diamond Buffer”). After trying dozens of OPAMPs – from NE5534 to the latest offers from major manufacturers, OPA 2604 was chosen because its most balanced and harmonic sound in the Yulong A28 particular design. The output is MJE243/253 middle powered transistor...

Other features include:

Plitron power transformer from Canada
Neutrik XLR connectors
Alpha 4-gang potentiometer made in Tai Wan
Unbalanced inputs are converted to balanced signal by an OPA1632
Balanced/unbalanced input selection is done by a group of relays to optimize signal path
Precision machined aluminum case with matching size to Sabre DA8 DAC to easily set up as a combo

-> http://www.alpha-products.com/Potentiometers/potentiometers.html

[maty]

El ODA tiene mucha más potencia que el O2 y es de escritorio. En principio iba a ser un circuitillo complementario al O2. Tampoco es que esté muy atento al proyecto.

[maty]

-> http://www.diyaudio.com/forums/headphone-systems/196149-rjm-audio-sapphire-desktop-headphone-amplifier-14.html#post3762734

I've spent a couple of days doing some serious listening. It's easy work: There is no listener fatigue. This is the current version, OPA134 and 28 mA of bias current. R4=10k, and that's a bit low: I'm listening at 11 o'clock typically (true 2 Vmrs input signal), so R4=15k or even 20k would be ideal with the HD600s.

Here's my observation re. bias current, based on trying 8, 16, 20, 28 and 65 mA:

There is a gradual shift with increasing bias current in favor of the bass frequencies. There is also a related and concomitant shift of the stereo image from the center towards both ears. So, at low bias currents the sound is lightweight but also compressed in space. At high bias currents the air is gone, and the stereo image has the classic headphone "blobs-in-the-ears" effect, with a suckout region in the center.

Now here's where it gets interesting: at the optimum setting that more-or-less balances the stereo image evenly between centered and L-R extremes the soundstage snaps into place ... not simply L-R but out away from you. The sound doesn't seem to be in your head any more, but moves out in front. This makes the whole listening experience far more natural. I suppose this was what the filters used in the old Headroom amps was supposed to do (but for my money never really delivered): remove the feeling of wearing headphones.

I have no idea why the sound should change like this, as the bias currents are all well in excess of the minimum needed to run the output stage in class A. However I have tried enough comparisons of different currents to be quite confident in the correlations I'm hearing.

es.mouser.com OPA134PA - Texas Instruments

[maty]

RIKES-100 - 0.68uF 600Vdc Rike Audio S-Cap Aluminium foil, PIO

-> http://www.hificollective.co.uk/catalog/rikes100-068uf-600vdc-rike-audio-scap-aluminium-foil-p-9442.html £29.40



-> http://www.diyaudio.com/forums/headphone-systems/196149-rjm-audio-sapphire-desktop-headphone-amplifier-24.html#post3885108 by Bibio

I have only tried 3 types of caps. it was easy for me to tell the difference between the caps that i have tried as i have 2 x 14s boards configured the same and the boards have connectors for quick removal/install.

The standard caps that Richard sends out are open but a bit rough in the vocals and get confused when things get a bit hot in the recording. but nice none the less.

Mundorf MCap EVO Oil Aluminium (0.68uf), very nice vocals and fairly open but like the standard caps they can sound a bit rough and congested. they take forever to bed in.

Rike Audio S-Caps PIO (0.68uf), do everything right. open, spacious, clean, deep dark blackness. if i were to criticise them then i would say that they can be too revealing but they never loose control no matter how hot the recording gets, you get what's there. they take less time than the EVO to bed in but still take a good 100hrs+. worth the money i paid for them.. yes as i got them brand new of the bay at half price, worth full retail.. hhhmm subjective, if you dont want to worry about the caps making a difference then yes i would say they are worth the retail price.

What I really wanted was Intertechnik Audyn True Copper Caps but the company never got back to me with the proper sizes as there are conflicting sizes depending on what web site you went to. but i think they are big. it was the diameter i was worried about but i have changed plans so that does not matter any more, i might try them out at a later date.

I'll pop the EVO oil in the 20 boards just to see how good they are against the Rike's and report back as the evo oil are 1/5 of the price.

[maty]

-> http://www.diyaudio.com/forums/headphone-systems/196149-rjm-audio-sapphire-desktop-headphone-amplifier-24.html#post3885787

On the improvement of the R2.0 boards:

Well, I mean yes I can point to a specific reason for the improvement: the bias currents have dramatically changed from 30 mA / 20 mA (driver/output) to 10 mA / 25 mA.

It makes the diamond buffer stage easier for the op amp to drive. There's no other changes on the same level: the filter capacitance increases 50%, the trace layout of the diamond buffer is re-worked. Neither are big deals...

[repente]

Aún no me he puesto a empollarme todo el post de diyaudio.com, pero gracias Maty por señalar las cosas importantes 

Lo de los condensadores viendo el empujón que le meten al Icon, ya tenía pensado cambiarselos 

[repente]

Al final he pedido unos Toroidys intermedios, de la gama "Audio" que estan a mitad de precio que los Supreme.
También tengo pedido el alps, uno normal de 6 patillas.
Esto ya está en marcha.... 

He hecho cuentas así a groso modo y si no me crujen en aduanas, creo que puede salir todo por menos de 200€ en materiales