2. amps-preamps
  3. 140029-80294

Does anyone care to ask an amplifier designer a technical question? My door is open.

I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
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Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.


128x128ramtubes
jlhaudio
1 posts
 
Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?
ramtubes's avatar
ramtubes OP
460 posts
 
@jlhaudio Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?


Along with changing the bias system from fixed to cathode bias and changing the B+ I found the 12AT7 was a better choice. It has a lower saturation voltage than a 12AX7 and higher current. As far as we can determine the amps sound the same. We want them to. 
fleschler
1,920 posts
 
My pre-amps are unusual in many ways as they use only six subminiature tubes, are a voltage regulated design with no fuse/breaker necessary and have the stepped attenuator out of the signal path but operates by bleeding off voltage to ground to attenuate the volume. That’s what the manufacturer told me. Sounds as good or better than an EAR 912 with tubes rated for 100,000 hours and non-microphonic. The phono pre-amp is similarly designed without the attenuator.
ieales's avatar
ieales
1,201 posts
 
I think it was Monster that did it to "burn in" their cables
When I consulted with Monster Pro in the 80s & 90s,AFAIR burn-in was never mentioned.

The first I heard of it was in the early naughts, but I had been in AA [Audiophile Anonymous] for a few years.
atmasphere's avatar
atmasphere
11,595 posts
 
Apparently some people just cannot restrain themselves or have difficulty with reading comprehension
-Or there might be a third explanation.

minimize artifacts occurring from the interconnect cable between the preamp and amp.

A second reason is that a preamp can provide a fairly high impedance load for the source
Source output 22R, amp inputs 23k5 or 100K. Adding a preamp with attendant switching, circuitry, noise and additional cables is little more than a subtle tone control. It maybe different, but it may not be better.


I agree with ieales and not the answer given above his, but then you all know that. What are these artifacts, are they Egyptian?
If you've heard cables sound different from one to another, that is an artifact. Cables have capacitance, inductance and characteristic impedance (hence the 600 ohm standard used with balanced lines for several decades).
The thing that intersts me is that most complain that the bass of passives is usually lacking. However the bass of passives goes to DC with no phase shift. Tube preamps do not go to DC and at 40 Hz will start to have some phase shift. Is the phase shift what they like?
It would be interesting to see if it is indeed phase shift. Many preamps don't have any phase shift right to 20Hz but I suspect that passives often do- not because the passive itself does of course, but because it in tandem with certain sources might.

A preamp need not have DC response to have immeasurable phase shift at 20Hz. For that it only need to go 2Hz.
Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?
Electrolytic capacitors do need to be formed. Most of this is done at the factory, simply by charging the cap to the forming voltage (and is actually the difference *in some cases* between two voltage ratings). This is to prevent the cap from being damaged at installation! However the caps are shipped without charge and can sit unused. They do need to form up properly again when installed.  In some of our larger amps, we often see the amp blow a fuse during turn-on (due to current inrush) that it won't ever blow later after the caps have formed up properly (which seems to take a week or so of intermittent use). 
More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.
+1


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