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
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I do appreciate all input about Pass Labs amplifiers and possible changes that might or might not affect their sound. I also found it very interesting that reversing the direction of an ordinary brand new Bussman fuse several times did consistently affect the sound I heard.
I own three Pass Lab amplifiers and like many audiophiles I respect what Nelson and his main co-designer Wayne do.
David Pritchard
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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
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I have enjoyed my experiment to see if three different fuses would affect the sound in my Pass Labs INT-60 amplifier. To my brain they did.
My next experiment will simplify things a a bit more. Today I ordered the Nelson Pass First Watt SIT-3 amplifier. This will be compared to the First Watt F-7 using stock fuses and boutique fuses. So two similar very low part count and simple circuit amplifiers will be used to compare the difference between two different type.output transistors. Then stock and boutique fuses will be tried in both.
The SIT-3 amplifier arrives this Friday.
The test will be partially blinded in that my Mother will be the listener and she is legally blind. The new amp if she likes it, is her Christmas present.
This will be fun.
David Pritchard MD
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As the original poster I chose to perform an experiment that I considered fun and thought it was worth while to report the results.
I chose the Pass Labs amplifier as their products do have the reputation of having a good power supply and being well built . I did not want to waste my time evaluating fuses in a product that has a questionable build quality. On all the Pass Labs amps that have fuses, the fuse is easily removed using a screw in fuse holder which is next to the on -off power supply switch. I also considered this an important reason to chose a Pass Labs amp. I do consider safety to be important.
The experiment was not designed to be sales pitch for a new product but to examine if fuses in an amplifier might affect the sound. The test results I obtained revealed that three different fuses had three different effects on the sound, and that in each case simply removing the fuse and changing the direction of the fuse also changed the sound.
I did not expect to hear a change in sound with the Bussman brand fuse. This alone made the experiment worthwhile to me. So for some audiophiles, simply changing the direction of the fuse may change the sound for the better. Fun to try if you have a fuse installed as the Pass products do.
Since changes of fuse type and direction were made multiple times an amplifier who's fuse was easy and safely removable was a conscious decision that I made.
After spending many hours doing this, I thought it would be informative to the audiophile community to publish my results. I hope others will repeat similar experiments and report their results.
David Pritchard
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I certainly welcome off line discussion about audio observations I have made and posted. My areas of interest are especially in fuses, wall outlet sonic changes, and Pass Labs amplifiers.
David Pritchard
575-644-1462
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As the original poster I do think it is important to remember I few points that I wrote about the topic.
This was an experiment to see if there were sonic differences using three different fuses - each installed and removed multiple times and in both directions. A well know respected amplifier brand ( Pass Labs) was used that has a reputation for having a excellent power supply. This was done on purpose to discount the experiment being devalued due to a "poor power supply being a factor in the observed results".
No other changes were made to the system for the past five months. So there are no other known major variables going on. The humidity (measured), and room temperature (measured) were kept constant. The time of day for listening was kept constant - 8:00 to 10;00 at night. The Pass Labs amplifier was also chosen as it can and was left on 24/7 (except when it was turned off to change fuses). Since this amplifier has a screw in fuse holder, fuses can be easily and safely changed.
This was a serious attempt on my part to do a meaningful evaluation of three fuses and their sonic effect on a well respected amplifier. It is the first of several experiments I have planned pertaining to this subject.
It was earlier pointed out earlier that testing - evaluating fuses is " by necessity a time consuming affair". That is absolutely correct and one reason I chose to report this experiment. It is a lot of work. It takes a lot of time.
My observations indicating a change in sound have not and will not ever have a percentage number assigned to them.
I have found it very helpful to watch all the You Tube videos posted featuring interviews with Nelson Pass and his co-designer Wayne Colburn of Pass Labs Inc. I will not attempt to condense what their approach to perfecting a design is but it involves both measurements and a lot of listening. Nelson also discusses the subjective and objective and their place in developing audio products.
Wayne Colburn of Pass Labs has been most gracious in his time and expertise to directly answer questions I had about Pass Labs's use of fuses and circuit breakers.
David Pritchard
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I do hope Audiogon will remove posts that resort to disrespect to other members. But I seriously hope that all posts remain on this thread that are written in a respectful manner , regardless of their agreeing or disagreeing with my observations . I see no reason to allow mob rule to shout down serious discussion about any audio topic. I also welcome suggestions in improving my test approach.
Tomorrow - Friday, the Pass Lab SIT-3 amplifier is scheduled to be delivered. Pass only made 250 of these units because the SIT transistor used is long out of production. Nelson is the sole designer of this unit and the F-7. I look forward to comparing this unique type of topology amp to the First Watt-7, and then to investigate any differences fuses and fuse direction makes.
David Pritchard
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I am glad to read georgehihi6 post. I hope all who have experimented with listening to a same piece of equipment with different fuses will report their findings. I especially hope Pass Labs amplifier users will participate.
georgehifi6 - do you know what brand fuse Gryphon uses? I think that is also interesting. Pass Labs uses Schurter Brand.
Wayne Colburn (Pass Labs) did tell me that their amps with circuit breakers have more circuitry in the signal path than those with fuse protection. I think amplifier design and implementation of a design is a fascinating area of the audio hobby.
Some tube amplifier builders do keep track of wire directionally such as the builder of the SET amp- Serious Audio. In these low part count amps, perhaps wire direction can be more easily heard? I have read where SET amp builders will audition many brands of each part used before the product goes to market.
David Pritchard
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rbyington:
I did talk directly to Pass Labs and they suggest to keep my amp on 24/7. Paul McGowan ( CEO of PS Audio) also recommends to keep the PS Audio amps on 24/7. Some reasons to keep always on are less stress on the system (from the initial current inrush) and thermal stabilization.
David Pritchard
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Wonderful post. You do not know for sure until you try. But if you are not interested in the possibility, do not try.
Concerning leaving amplifiers on, you will have a lower electric bill if you turn them off. Class A amps use a lot of electricity whether they have a signal or no signal. Mark at Reno Hi Fi certainly knows Pass Labs products. I would follow his advice. Indeed the Pass Labs SIT-3 amplifier (being delivered today) was purchased from him. It will use much less electricity than some of the other amps and so will always be left on.
Except when turned off to evaluate different fuses and their direction.
David Pritchard
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The Title of this thread is Pass Labs Amplifiers and fuses, and so I will discuss at least some aspects of the title subject.
Yesterday Mother's new Pass Labs First Watt SIT-3 amplifier arrived from Reno HiFi. Enclosed was an informative manual.
"The amplifier requires about One hour of operation to reach full operating temperature. I personally do not see a reason to run the amplifier all the time, but you can do that if you want to. The power supply capacitors are likely to last 20 years or more, and while they will slowly dry out just sitting there, they will have a longer life if the amplifier is not run continuously. Practically speaking, it makes sense to shut the amplifier off if you are not planning to use it the rest of the day".
"I answer all questions, even if the answer is No.
and sometimes it takes a little while" - Nelson Pass
In the experiment I performed with the Pass Labs INT-60, I heard a distinct difference using three fuses.
The newly acquired SIT amp is designed having a SET tube amplifier sound without using vacuum tubes or transformers. The goals of this amp are " to get transistors to sound like Triodes(vacuum tubes) and simplicity and minimalism of circuit design". I think this amplifier with a simple design will be a good test vehicle to further evaluate different fuse affects on sound. The amplifier will be left on 24/7 to minimize any "break in effects". This amp uses about 150 watts when on. And yes the Main circuit breaker is turned off when fuse rolling.
This amp is entirely designed by Nelson Pass and only 250 were manufactured. There are a few new units still for sale.
Out of the box with one hour warm up and the stock fuse, the sound is wonderful. For audiophiles with efficient speakers and wanting an amp that is sold state but sounds like a SET vacuum tube amp, this is a compelling option.
I soon will also be posting the results of the interaction of fuses and the Pass Labs Headphone amp.
I hope all readers will take some time to reflect that today is the date of the attack on Pearl Harbor.
David Pritchard
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This is the second of three planned posts evaluating the effect of different fuses on three different Pass Labs amplifiers.
This evaluation is using the Pass Labs HP-1 amp. I enjoy this amp especially for night time listening. My favorite headphones were used, the Focal Utopias and the Sennheiser 800.. The source is a Marantz SACD player.
The amplifier and SACD player were kept on 24/7.
The fuses evaluated were the stock fuse - wire around a ceramic rod enclosed in a glass case, a Synergistic Research Blue fuse, and a Synergistic Orange fuse. Listening was done at night, room temperature was a constant 73 degrees, humidity 35-41 percent and all other electrical devices except refrigerator and heating system were off.
Listening was done with four cd's. Male vocals- Willie Nelson - "Stardust" (SACD disc), female vocals- jazz singer Nnenna Freelon- "Live", acoustic instrumentals featuring multiple instruments and complex percussion - "Sera Una Noche" and solo piano- "Mozart -Works From His Golden Age".
The last two Cd's are on the MA record label. MA owner Todd Garfinkle records using only two microphones in buildings that have wonderful ambient spacious sound qualities.
The Orange fuse's effect on the sound clearly gave the biggest improvement. Especially with the MA recordings, the ability to hear micro details during the decay portion of a played note made me forget I was listening to headphones. Many times I felt as though I was a solitary guest who was allowed to sit in during a performance.
On the Nnena Freelon album ( Concord Records) , the live crowd ambience was not a distraction but added to the enjoyment of listening to the performance.
Willie Nelson's nylon guitar sounded more detailed and richer when the Orange fuse was in the system.
I found the Orange fuse to give a significant improvement to my Pass Labs powered headphone system. I think the cost benefit ratio is most excellent.
Both the Cable Company and VH Audio did announce a buy two and get one free Synergistic Research fuse special. This according to the Cable Company (E-mail which arrived today) is only for the next two weeks.
David Pritchard
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uberwaltz:
I do hope you audition the Orange fuses in the Ayre EX 8. What a special amplifier. Put the fuses in and do a final evaluation after 14 days. If you like the sonic change - Merry Christmas ! Send them back if you do not think the are worth it. Please report what you hear. I am a big fan of Ayre products as well as Pass Labs products.
The last few days I have been watching "You Tube" videos after telling the search microphone on my TV - " Audiophile fuses".
Multiple interesting videos both pro and against.
Magneplan Fuse Upgrade
Audiophile Fuses
Audio Magic Beeswax Fuse vs. Furutech Blue
Fuse AMR
Fitting More Internal Audiophile Fuses
Upgrading to Audiophile Fuses
Audiophile and Ceramic Fuses Tests and Thoughts
Audiophile Snake Oil !
Synergistic Research Orange Fuse
I hope readers of this thread will take time to watch some of these interesting videos. I continue to be impressed with the improvement the Synergistic Research Orange fuse has on the performance of the Pass Labs HP-1 amplifier.
The HP-1 which is a wonderful amp that was specifically designed for both low impedance and high impedance headphones is now performing at an even higher level of sonic enjoyment.
David Pritchard
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