John Curl's Blowtorch preamplifier part II

[simon7000]

Originally Posted by KBK

I finally went to listen to my phono preamp, now that it is fully burned in from stem to stern... and I found I had managed to, ahem...'soften' one of the Rohm D786s transistors at the input.

Due to availability, it's a notable problem.

Any suggestions for a drop in or near drop in?

Have ROHM 2SD786 - want ROHM 2SB737

[john curl]

While many here can not figure out why, we still 'trudge on' on a daily basis to make better audio electronics, both analog and digital. What one group of us is working on most, is reducing power supply noise and interference. Kind of like making the equivalent of a perfect battery. How can this matter much?
Subjectively, we have found it to be very important. The CTC Blowtorch that this thread is based on, used 3 passive components and 3 active stages before the DC met the amplifying circuitry.
We are finding the same effort, when used with digital, can be at least as important.
I think that we have to look at the power supply as being an input port, somewhat similar to the inputs, and while often considered an unlikely contributer, but at higher frequencies, especially in this time and age, with switching supplies, etc, the power supply rejection is just not that good to keep it out, in every audible way. Perhaps a meter would have a problem measuring it, but the ear can certainly hear an A-B difference.
Many here have probably seen examples where audio engineers have just given up trying to make a 'perfect' power supply and switched to gell cells, (lead acid batteries), or a string of D cells. If you try this, you might be surprised how good it works, but also what a hassle it is to keep the batteries in operating condition.
It is better if we can use some sort of AC-DC conversion, without compromising the audio quality. That is the quest.

[jan.didden]

A quick off-topic one, John.
Did you receive Linear Audio Vol 1? I had a few gone AWOL between the old continent and the new.

jan didden

[john curl]

Yes, I did, it is very good, thank you.

[Johnloudb]

Originally Posted by john curl

While many here can not figure out why, we still 'trudge on' on a daily basis to make better audio electronics, both analog and digital. What one group of us is working on most, is reducing power supply noise and interference. Kind of like making the equivalent of a perfect battery. How can this matter much?
Subjectively, we have found it to be very important.

I, of course, agree with you about the importance of eliminating noise. I've found even the highest quality audio gear can be susceptible to noise from the power line. The amplifier that hurt my ears measures very well and has excellent noise performance.

Months ago, I was hooking up our main speakers differently - using two amps in a vertical bi-amp configuration - so we could use an external crossover to a subwoofer and not have it go through the mids/tweets.

Anyway, I hooked them up and gave a listen and right ear started hurting. I wasn't sure which amp was the one I just added since they are identical, and they were both hooked up to a PS Audio power line conditioner.

I let the amps warm up and let them alone to let my ear calm down. This type of hurt makes your ears more sensitive to other everyday sounds, and I had to just it easy for awhile. I waited a day and then gave a listen. Again my right ear came away hurt again and my left was hurting slightly. I was kind of upset given the past experience with the amps, and the fact that I was using a power line conditioner.

So, I went looking for a problem, and I found the right amp had a cheater plug on it. I didn't know why that would have any affect ... just guesses, but I took off the cheater plug. As I remember I didn't listen for a day or two to let my ears get feeling better.

The next time I listened, all was good and it sounded as it should. They sounded really good. The amps had very good specs and reviews, and I can heard no noise from the speakers.

I've even talked with some else who had the same problem with a quality amp.

I think the noise spectrum is really important. The LP has a lot of low frequency noise but decreases with increasing frequency, whereas CD has a flat noise spectrum.

Flat, white noise is a lot harder for the ears to filter out. People with decreased sound tolerance find wide band noise difficult to tolerate sometimes, and it hurts their ears at any level. At the same time working with wide band noise is helpful. They use a pink noise or a special wide band noise that's easier on the ears then white noise, to treat people with decreased sound tolerance.

[jan.didden]

Originally Posted by john curl

Yes, I did, it is very good, thank you.

Thanks John.

jan

[john curl]

JohnloudB, at this time, I am trying the Bybee music rails as a useful add-on to my newer designs. They can be amazing in their measured performance, just doing an A-B.

[john curl]

The Bybee Music Rails do what they are supposed to do, and they go right down to very low frequencies. About 40 dB is possible (and measurable) with a relatively noisy supply that needs filtering. IF your supply is already VERY quiet, then they might not help too much, but many standard lab supplies, for example, can be improved. In fact, I am going to add them into my test set-up. Power supply hum residual reduction is amazing!

[Johnloudb]

Originally Posted by john curl

JohnloudB, at this time, I am trying the Bybee music rails as a useful add-on to my newer designs. They can be amazing in their measured performance, just doing an A-B.

Those look nice. I would be tempted to try those in our amps ... the trick would be to convince my dad to even let me touch them.

[jkeny]

Originally Posted by john curl

While many here can not figure out why, we still 'trudge on' on a daily basis to make better audio electronics, both analog and digital. What one group of us is working on most, is reducing power supply noise and interference. Kind of like making the equivalent of a perfect battery. How can this matter much?
Subjectively, we have found it to be very important. The CTC Blowtorch that this thread is based on, used 3 passive components and 3 active stages before the DC met the amplifying circuitry.
We are finding the same effort, when used with digital, can be at least as important.
I think that we have to look at the power supply as being an input port, somewhat similar to the inputs, and while often considered an unlikely contributer, but at higher frequencies, especially in this time and age, with switching supplies, etc, the power supply rejection is just not that good to keep it out, in every audible way. Perhaps a meter would have a problem measuring it, but the ear can certainly hear an A-B difference.
Many here have probably seen examples where audio engineers have just given up trying to make a 'perfect' power supply and switched to gell cells, (lead acid batteries), or a string of D cells. If you try this, you might be surprised how good it works, but also what a hassle it is to keep the batteries in operating condition.
It is better if we can use some sort of AC-DC conversion, without compromising the audio quality. That is the quest.

Couldn't agree more John - it has been a mantra of mine for a while now that PS in digital has a huge part to play in the overall sound. I have focused on using battery power & removing the inconvenience factor. The improvements that are immediately apparent with battery power might not be currently measurable but the Nordost/Acuity paper seems to throw a chink of light on this issue & hopefully will prove not to be just marketing blurb? You have probably seen this paper already referenced in the Bybee thread