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.


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ramtubes's avatar
ramtubes OP
460 posts
 
@bifwynne  Btw, I owe you two quads of KT-150s for matching. The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.

Btw, I owe you two quads of KT-150s for matching. The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.


We have been awaiting your tubes. Time has passed and we have to get back on the same page as to the specs for current and G2 volts. Better not to wait on these things. Strike while the iron is hot as they say.

The difference between Bill Johnson amps and the current products is night and day. I appreciate the simplicity but not so much the performance specs. However specs arent everything. We are finding out some very interesting things on some listening tests. Very hard to get a really good handle on an amp without an A/B and a reference. 


ramtubes's avatar
ramtubes OP
460 posts
 
Here's a schematic of the ST-120 version (sans values for resistors and capacitors), which is apparently the same schematic as the ST-70 except for resistor sets.
https://drive.google.com/open?id=1IMaAaaWRuIU8v-_OZ3jfrcQCI5a0gpP8 


Nice circuit, simple. The 16 ohm tap is a bit silly and taking the feedback off it can have both good and bad effects. Otherwise, classic Marantz, Heath, Eico, etc.
ramtubes's avatar
ramtubes OP
460 posts
 
@cardiff  Here is one nobody seems to have asked yet...

What is the role and importance of significantly upgraded power cords in component design? It seems to me that the PC is a fundamental part of the electronic device and that the manufacturer should optimize the cord for the device in building it. What are your thoughts on the matter as someone who actually builds electronics?


I put the proper cord on my RM-9 but now people want me to put an IEC on there so they can use theirs. I did opimize but thats not good enough for the PC and fuse people.  May I also offer that a captive cord has one less pair of connections. When you pull current on a IEC it gets hot, is that good?

Before audiophiles got into power cords most manufacturers went to IEC connectors for no other reason that it makes the amp easier to handle and pack up, not so people could go fooling around with wire. 
ramtubes's avatar
ramtubes OP
460 posts
 
@atmasphere  A choke is helpful as it can be used to help filter out the 60Hz sawtooth waveform that is part of the rectification process.


Ralph, Im sure you meant to say 120 Hz ripple, not 60 Hz unless you are using half wave power supplies.

Chokes are indeed great things and not found in many amplifiers these days because its just too much trouble for some designers to have them made. I put two in the RM-9 MK II as Ultralinear amps benefit from them greatly. The G2 on an ultralinear has the same ripple as the plate. Where a pentode amp can have additional filtering for the G2.
ramtubes's avatar
ramtubes OP
460 posts
 
@teo Some Ignorance is so manifold that it is used to commit to attacks so libelous and underhanded... that the person initiating is practically kicked off a given forum. So obvious to all, that there aren’t even words for it.And then that illiteracy and ignorance is paraded about as somehow being informed. That we can all be that dense. Jebus. What a horrific world that would be. So far gone that it can’t even be explained to a given person how far off base and wrongheaded a given comment might be.


I think im being called out but so poetically I can hardly be certain. I think Teo has a better future as Poet and Philosopher. 

His verse is  almost Shakespearian

  https://en.wikipedia.org/wiki/Sonnet_94

Bruce De Plama (Brians brother) often quoted the last of this. 

For sweetest things turn sourest by their deeds;
Lilies that fester smell far worse than weeds.
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