FM Acoustics amps

[MylesBAstor]

An interesting amp is the Tube Research Labs GTR-800. From what I understand it is push-pull triode 800W class A in 8 Ohm, zero NFB, and staying in 800W class A while impedance is dropping all the way down below 1 Ohm.

Thanks,
Roysen

Did Brian and Paul deliver yours yet?

 

[FrantzM]

Loyd,

It is not enough to know the idle consumption to know the operating class versus power and load impedance - you have to know both the power supply DC voltage and the bias current of the output stage.

microstrip

Point well taken about Class A single-ended versus Push-pull,. You are correct. It remains however that most Class A amps do not even approach 25% even when push-pull, the inefficiency of thepower supply count alsi in the overall efficiency of the amplifier so ... Yet the idle consumption remains an indication . An amplifier idle consumption cannot be 4000 watts and same amplifier be able to deliver 2500 watts in Class A under any load it isn't possible. For that it must move to Class B and most so-called Class A amplifiers, if not all do that.
Tubes

Back to FMA...

 

[Thf99]

Pls post your impressions! would love to know what you think!

I will, Lloyd. In the meantime, I'm waiting for the invitation from the owner.

 

[Roysen]

Possible , it uses an output transformer ...

Yes

 

[Roysen]

Did Brian and Paul deliver yours yet?

Nope, not yet. They are waiting for delivery of the Duelund coupling capacitors. I think it is still 4-5 weeks waiting time for those to be delivered. I requested that Paul tried the Duelund CAST caps instead of the original Mundorf they have used for years. Paul tried them and found them outstanding so this delay is based on my request.

Thanks,
Roysen

 

[microstrip]

microstrip

Point well taken about Class A single-ended versus Push-pull,. You are correct. It remains however that most Class A amps do not even approach 25% even when push-pull, the inefficiency of thepower supply count alsi in the overall efficiency of the amplifier so ... Yet the idle consumption remains an indication . An amplifier idle consumption cannot be 4000 watts and same amplifier be able to deliver 2500 watts in Class A under any load it isn't possible. For that it must move to Class B and most so-called Class A amplifiers, if not all do that.
Tubes

Back to FMA...

Frantz,

I would like to add a point, before going back. to FMA

If you consider the large differences between speakers efficiency and impedance, the dynamic range of recorded music and the logarithmic variation of power versus listening level, you will find that, unless you have access to measuring instruments and some practice, this debate is mainly theoretical. In real life, you risk that most of the time you think that your power amplifier is working in class A it will not be, and may be it will be in class A when you are not expecting.

I can guess that a few are now preparing an immediate answer - it is all bias expectation, guys!

 

[MylesBAstor]

Nope, not yet. They are waiting for delivery of the Duelund coupling capacitors. I think it is still 4-5 weeks waiting time for those to be delivered. I requested that Paul tried the Duelund CAST caps instead of the original Mundorf they have used for years. Paul tried them and found them outstanding so this delay is based on my request.

Thanks,
Roysen

Yes I had to wait 6 weeks for my Duelands. They are very labor intensive to make. Still though have yet to install them but am hoping to listen to them soon. And they are replacing the Mundorf Au/Ag in oil caps in my tape preamp.

 

[A.wayne]

Loyd,

It is not enough to know the idle consumption to know the operating class versus power and load impedance - you have to know both the power supply DC voltage and the bias current of the output stage.

You forgot the amount of output devices ... This is important when designing PSU for desired class-a power, quiescent power is the end results of this , so yes we can get a very good approximation from the Idle current what is being done in class-a ...

 

[Roysen]

Yes I had to wait 6 weeks for my Duelands. They are very labor intensive to make. Still though have yet to install them but am hoping to listen to them soon. And they are replacing the Mundorf Au/Ag in oil caps in my tape preamp.

I am looking forward to hearing your impressions of that change.

Thanks,
Roysen

 

[A.wayne]

What stages are you using the caps in Roysen ....?

 

[Roysen]

What stages are you using the caps in Roysen ....?

Don't know yet. Everywhere he can I guess.

Thanks,
Roysen

 

[A.wayne]

Those are great sounding amps enjoy ......!!!!

 

[Bruce B]

I see FM Acoustics listed as one of the vendors that will be at RMAF in the Primrose ballroom.

 

[mep]

I see FM Acoustics listed as one of the vendors that will be at RMAF in the Primrose ballroom.

Really? Let's all meet there so we can be blown away. If they are giving out Kool-Aid as a refreshment, don't drink it until after you listen and form an opinion.

 

[A.wayne]

Why not carry your own from home, so you can have your favorite flavor ....

 

[mep]

Why not carry your own from home, so you can have your favorite flavor ....

I don't drink Kool-Aid at home or work. Sometimes at work I have to pretend I'm drinking the Kool-Aid, but everybody with half a brain quickly figures out I really poured it out and never drank it.

 

[ack]

Really? Let's all meet there so we can be blown away. If they are giving out Kool-Aid as a refreshment, don't drink it until after you listen and form an opinion.

When in attack mode, I suggest first drinking

 

[mep]

Seriously Ack, I would love to hear the FMA gear.

 

[Mike Lavigne]

Seriously Ack, I would love to hear the FMA gear.

it's there in that room most years at RMAF, the guys from Colorado Springs bring them.

 

[mep]

it's there in that room most years at RMAF, the guys from Colorado Springs bring them.

I obviously missed it last year, but then the FMA drum-beats weren't as loud on this forum last year as they have been now and I wouldn't have been seeking them out for a listen.