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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tomic601's avatar
tomic601
12,957 posts
 
 @mrdecibel indeed.....I think IF memory serves correctly we sold at least 4 pair of them including to a bar owner who loved his music while tending bar....
On a lark one night at the store, while owner away, we biamped them w DH500 on the low end and a DH200 on top ( we had better amos but wanted similar tranfers function )..Played Peter Gabriel - Security...that CD has some low end wallop !!!!!
wow...

I would buy a pair today just for grins....ha


analogluvr
859 posts
 
I think microphonics can sound euphonic. I built a Bottlehead be pre-and while it was fantastic the tubes in that application were very microphonic. It lends everything a rounder more robust sound as it’s like a delayed Feedback. 
 That is ultimately what made me get rid of it 
mr_m
1,900 posts
 
tomic601, DH-500 and DH-200. Are you referring to the Hafler's? I had a DH-200, and a DH-220 and DH-110 pre, that I built from kits. Great little amps and what a blast to build from kits! Quite the learning experience. All mine worked from the first try after assembly.
atmasphere's avatar
atmasphere
11,861 posts
 
I think microphonics can sound euphonic. I built a Bottlehead be pre-and while it was fantastic the tubes in that application were very microphonic. It lends everything a rounder more robust sound as it’s like a delayed Feedback.
That's a new one on me- usually microphonics causes harshness!
ramtubes's avatar
ramtubes OP
460 posts
 
@bdp24 

@ramtubes, Roger, I know you consider the 6DJ8 superior to the 12AX7 for use in a phono stage, but let me ask you this anyway ;-) : how do you feel about substituting a pair of 5751’s in place of a phono amp’s 12AX7’s? I know the 5751 exhibits lower gain and noise (in the 1980’s I had a Dynaco PAS 2 that was "modified" by Frank Van Alstine, and he put in 5751’s. That pre was very quiet.), but are there trade-offs involved between the two tubes? Is the 5751 a true direct replacement for the 12AX7, regardless of application? Or are there circuit considerations? If used in an RIAA moving magnet phono stage (gain of 42dB or so), will the 5751 automatically provide a little more headroom/freedom from overload than the 12AX7?


The 5751 is slightly different froma 12AX7 and close enough to be tried. We have plenty of very low noise ones. CJ has used them for years. I use one in the integrated I am developing. I could have used a 12AX7 but like the 5751 better. it also happens to be a "Premium" tube which means they took more care on consistancy and long life. It falls under the "industrial" category where failures are not appreciated. Headroom is more of a circuit parameter than a tube parameter. 
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