Pass Labs and Fuses

I do hope many who read this thread will go to " You Tube " and type in "Nelson Pass". Watch several of those videos and I think you will get a fabulous insight as to what most interests him, what he tries to achieve in a design, the trade offs he has to make, the parts he uses, etc.

I am not aware of a designer - manufacturer who is more open about his approach to audio amplifiers.
David Pritchard

David, you hit it right on the head,”less emotionally involving.”
Although I do not own one at this time, Mr Pass makes some of the best sounding amps. I think Beethoven proved that you don’t have to be able to hear, you just have to know what you are doing.
Some days my system sounds killer, other days not as good even with the same recording. The only things that have changed are the humidity and the barometric pressure. The real culprit is my state of mind, happy vs pissed off. If there is just one neuron in your brain that thinks something is going to sound better, it will. This does not mean that there are not meaningful changes you can make, there are. In my experience there is always a sound reason why something sounds better. In the case of the fuses there is not one. I use to bypass all the fuses in my system including speaker fuses. Then I started doing AB experiments with fuses, wire and switches. There was a slight improvement in bass bypassing speaker fuses. Otherwise the differences were hard to appreciate. I also always have a second set of ears participating. It would be better to have 100 sets but it would be hard to arrange for obvious reasons.
In most cases you are better off buying more music. 

I have used a Blue Fuse in my Pass XP-20 preamp. It was easy to choose direction and, when in the correct direction, contributed to superior performance versus the stock fuse (which was also checked for direction and removed and reinserted as a check).

How is it that one way it sounds better than the other-way??
When the AC (clue here "alternating current") is changing it direction 60 x a second?? You would have to be changing the fuse direction also 60 x a second to prove what you said that it "it sounds better one way than the other".

On "You Tube there is a six part interview with Nelson Pass. I found it fascinating. He has been experimenting with solid state designs for over 40 years. But it is important to know he is not the only designer at Pass Labs.
 
First Watt 7 amp - Nelson Pass primary designer
Pass Labs INT-60 Wayne Colburn primary designer
Pass Labs HP-1 Jam Somasundram primary designer

I am fortunate to have an example of each designers work.
Wayne Colburn has been designing at Pass Labs for 31 years!

A few quotes from Nelson on why there is more than one product sold and why he has been doing this for 40+ years. "What interests me most about amplifiers are the differences in sound created by different topologies". He creates amplifiers that create a "sound which has a particular signature".

In a You Tube video from 2016 there are shots of many Pass Labs products with their sides and lids removed to show the inside layouts and parts used. On purpose there is a high commonality of parts used to decrease variables. Nelson collects and stockpiles different transistors for possible future products whether they be Pass Labs products, First Watt products, or as a diagram released to the DYI community. Showing just one parts bin, Nelson estimated he had 250,000 examples of that chip.

He will run out of time on Earth before he runs out of different chips to evaluate.

I have also admired audiophiles who post results of evaluating the sonic changes using different capacitors of the same value in a piece of equipment. Tedious, time consuming, and requires excellent soldering skills (which I do not have).

I have enjoyed tube rolling in amplifiers for years. I have a large collection of the same type of tube made by different companies, that vary in age from new to 70+ years old. I do not find the sound to be dramatically different except my emotional response can be dramatically different. With some tubes I get a "That's the sound I want ! " I find that moment exciting and worth the effort in time and money.

I have also experienced the same satisfaction trying different fuses in the same piece of equipment. I now have 11 different fuses of the same value that I have listened carefully to. It is very time consuming and tedious but I find it satisfying.

 I work hard at minimizing any variables. My house is kept at the same temperature, the humidity is kept exactly at 37%, listening is always done at the same time of day (8:00 to 10:00 pm ), a record is kept of how long the fuse has been in the equipment, which direction installed, and the same music is used for evaluation. Written notes are kept to refer as a record.

On occasion I have read people asking the question about possible sonic changes heard using different fuses. I try my best to report my experiences listening to different fuses so others may use them as a data point of reference.

 As in Vacuum Tube rolling or Capacitor swapping, others may not hear a difference between different fuses or may come to a different conclusion to the quality of the change in sound.

David Pritchard