RMI-FC100, a single stage audio power amplifier

[fab]

DRZ1

DRZ1, can you please send me a private e-mail because your e-mail is not activated.

There is a friendly DIY audio demonstration in Montreal on March 14th and if you can make it I would like to know how the RMI-FC100 sounds like.

Thanks

 

[ttan98]

Roender,

I have most of the parts to make a VARIATION of this amplifier. I wonder what is the impact of non-matching output transistors would do to the distortion level and any serious impact to the sound quality?

thanks

 

[Sheldon]

Getting There

Probably a month or so before I power up the full amp, but ready to test front end.

 

[pooge]

I hope you haven't soldered in those output transistors yet. Not that it would be fatal, but I'd get them bolted onto the heat sink first before soldering them. That will place less stress on the solder joints than if bolted on after soldering.

 

[Sheldon]

I hope you haven't soldered in those output transistors yet. Not that it would be fatal, but I'd get them bolted onto the heat sink first before soldering them. That will place less stress on the solder joints than if bolted on after soldering.

No. Only tacked one lead per transistor. Will mount, then reflow, then solder all connections.

Sheldon

 

[pooge]

Re: DRZ1

DRZ1, can you please send me a private e-mail because your e-mail is not activated.
Thanks

Same here, DRZ1. I'd like to discuss some things with you off line.

 

[pooge]

I have posted another transformer group buy announcement in the group buy thread


Group buy

 

[roender]

Bloody battle

Last weekend I have done some comparing tests against Tibi's QUASAR (QUAD405 reborn) amplifier:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=124348&highlight=
The source was a OPPO, a highly modified player by Tibi, and the same player was used as digital source for my RMI-DAC1.
http://www.diyaudio.com/forums/showthread.php?postid=1758611#post1758611
As for the speakers, we used Triangle Quartet.
Results?
Very good amplifiers, both RMI-FC100 and QUASAR.
I am not good in making descriptions so I would like to ask Tibi to make some, please.

Cheers,
Mihai

 

[iTiberius]

I would like to thank Mihai for honoring my invitation !
We both enjoyed a nice evening listening top notch amplifiers.

Systems used:
- Triangle Genese QUARTET speakers
- bi-wiring NAIM speaker cables
- RMI-FC100 and QUASAR amplifiers
- Audioquest COBRA interconnect
- Rockna RD2 DAC super moded by Mihai
- diy teflon sp/dif cable made by Mihai
- OPPO980H supermoded by me

RMI-FC100 sound:
Excellent separation, very good micro and macrodinamics, wide soundstage with precise focus.
Seems that the amplifier need some time to warm up, so after ~2h started to shine. Instruments acquired body, bass becomes tight and deep.

Mihai's moded Rockna RD2 was a little muddy in the beginning, but after some warm up we definitely switched from OPPO output to RD2 DAC.

I'm really impressed by Mihai amplifier !

Congratulations Mihai ! You are now in the F1 world of audio, where every component make a real difference ! ;-)


Best regards,
Tibi

PS. I need to mention that the schematic of QUASAR amplifier used in this "bloody battle" is not published on this forum, yet. Stay tuned.;-)

 

[roender]

Thanks Tibi

Your amp is better than mine on bass ... The next version of RMI-FC100 would be with better than MUSE KG power supply caps.

Cheers,
Mihai

 

[pooge]

The next version of RMI-FC100 would be with better than MUSE KG power supply caps.

Cheers,
Mihai

Not sure I understand this. Are you saying that using KGs will better the bass in the next version, or that you found something better than the KGs?

 

[roender]

Hi Pooge,

The KG is a very good cap, and the bass response is also good, but I want perfect bass, a very tight bass. I don't know if this is possible but I would like to try Jansen and maybe BHC T network caps.
Also, do not forget that Triangle Quartet is not an easy to drive speaker ...

Cheers,
M

 

[DRZ1]

I would like to thank Mihai for honoring my invitation !
We both enjoyed a nice evening listening top notch amplifiers.


Seems that the amplifier need some time to warm up, so after ~2h started to shine.

Héhéhé it's telling me something....

 

[DRZ1]

This amp is spectacular, no other words.

The bass control is incredible. I thing that this low output impedance with high current capacity make a real difference. My speakers never plays like this before. Deep super controlled extended bass.

The Mids are naturals , very good, like my Symasym.

The highs are like the low end, more extended, more present, very sweet.

This extended response seems to enlarge the presentation, big soundstage, very dynamic.

It's a fantastic amp, and the funny thing, the hotter it is , the better it play and the polarisation seems to stay at it's setting.



Roender , thank you very much for this amp. I think i will stick on this one, enough for me to.

I really encourage anyone who need a HI-FI amp to build it. It's not cheap for home cinema , but it's a real Hi-Fi amp.

And like Roender said it's a little triky to build, not a first time attempt.


My speakers are BW DM 603 S3.

 

[felixx]

Congratulations for both amps.
I know there was many,many hours of tests and listenings.
Also will be interesting to make that burn amp tests on other speakers.

 

[roender]

Thanks Felixx, Vali if I remember correctly... if not, the Ester is close so I will owe you a lamb

Héhéhé it's telling me something....

Denis,

It is true that bass is better and better as amplifier is getting hot, but with hard to drive speakers the bass control is not exceptional. You may say I'm a perfectionist
I will rebuild the amplifier with top components: TX2352 resistors and Jensen 4-pole capacitors for PSU

Cheers,
Mihai

 

[fab]

...
PS. I need to mention that the schematic of QUASAR amplifier used in this "bloody battle" is not published on this forum, yet. Stay tuned.;-)

Thanks Tibi
Your amp is better than mine on bass ... The next version of RMI-FC100 would be with better than MUSE KG power supply caps.
Cheers,
Mihai

Unless the Quasar does not use anymore the Lateral Mosfets anymore (it was the case for the last schematics available on the web site), it seems that 2SK1058/J162 can make good bass after all...

 

[Sheldon]

t is true that bass is better and better as amplifier is getting hot, but with hard to drive speakers the bass control is not exceptional. You may say I'm a perfectionist
I will rebuild the amplifier with top components: TX2352 resistors and Jensen 4-pole capacitors for PSU

Place to fix that is at the speaker-room level. Part of a good speaker design should be a reasonable impedance profile. My amps aren't going to drive the low bass anyway. Instead of biwire, biamp and cross in the low bass at line level.

Sheldon

 

[ttan98]

Roender,

Can you answer post 682 or you refer not to. Is your amp is critical to matching output transistors, ir npn and pnp to sound good?

 

[maxlorenz]

Dear Roender,

Have you considered J. Carr-s advice?

To mention an alternative to batteries, you may like to try your hand at some type of "never-connected" power supply, similar to the circuit that I posted years ago, or the one that EC Designs has come up with recently for his DAC project. Based on personal experience (as well as listening feedback from dealers and customers), I can vouch that, in terms of sonic benefits, this is a worthwhile area for development effort - possibly more so than the amplifier circuit itself.

After succesfully trying it on DACs and preamps, I installed ECdesigns charge transfer circuit (without gyrator part) on my UCD180 amps and the improvement in clarity and detail was surprising< everything sounds more controlled.
It removed a graininess that I did not noticed before.
In my case I doubled the previous capacitance (from 10mF) . I don-t know if you have the space to increase it...I am sure you could addapt it to your amps needs.

http://picasaweb.google.com/lh/photo/rOgiSl8IVgPdqOcKLPkbNA?feat=directlink

I am modding all my equipment with this circuit
Regards,
M