My Low Watt SET amp & High Sensitivity Speaker Journey ~

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FullRangeMan

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Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #41 on: 15 Nov 2019, 05:02 pm »
Richard, the 15 inch driver is an "Eminence Delta Pro 15" It has several things working for it. The accordion framework that attaches the speaker cone is not paper but is a special treated cloth that gives excellent moving ability to the cone. It does take a breaking in period. The 15 inch driver has an 80 ounce (5lb) magnet. It does not take much current to motivate this speaker. The midrange-tweeter combo is a "JBL-GTO 939" It does an excellent job. Musicians convinced me that the 15 inch driver  does very well at reproducing both bass and midrange. This 15 inch driver is good from 40 HZ to 4200HZ, thus my crossover network is set at 4000 HZ.
see more attached pictures.
Chuck








Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #42 on: 15 Nov 2019, 06:05 pm »
Richard, I forgot to put the "A" after" Eminence Delta Pro 15 A" You can verify the Specs on their web site as was mentioned on a previous post near mine.
Chuck

Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #43 on: 15 Nov 2019, 06:29 pm »
Important point for all on these SET tube amps. They should be given a warm up time without high voltage B+. Why? If one has a very low resistance rectifier tube like a 5AR4 or a solid state rectifier allowing B+ very quickly it causes cathode stripping of electrons of the tubes before the tubes are in control. On my amps I have put a switch between the center tap of the high voltage winding to ground. Given a period of time for the tubes to warm up, then I close that switch to turn on the B+. You will save a lot of life of your tubes.
See another picture of the front of one of my mono block amps. You will see two switches, the big one is AC power on and off, the small micro switch is the on and off of the B+.
To shut down your amps turn off the B+ first then your AC power. See pix.

Chuck


Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #44 on: 15 Nov 2019, 07:53 pm »
My thoughts on Gordon Rankin's Bugle 45 Amp. Very crucial to the workings of this amp besides the "sweet 45" tubes is the 9 pin 6072A tube. The commercial equal is the 12AY7 tube.  I found that the 12AY7 tube does not give the response of the 6072A tube. The 6072A tube is military tube was designed for the WWII military computers!! They are very high quality, designed to be very low in microphonics and high quality reproduction. Many use the GE black plates 6072A tube. I used them also for a time and was pleased with them. A few years ago I was fortunate enough to come across a few RCA long plates version of the 6072A tube. They were considered an extinct tube. The GE 6072A tube's plates are 14mm long. The RCA 6072A(also military) plates are 17mm long. I went back and forth exchanging the GE and RCA tubes and do find the RCA is a little more open and a little better in fidelity. The problem being we will probably never find these RCA long plates again.
If you desire to find out how this 6072 operates in the circuitry of the 45 Bugle amp I have a document on SRPP tube amplification document explaining its operation. It is this type of operation that gives the BUGLE 45 its unique sound.  Give me your e-mail address and I will send it to you.
Chuck

sonicboom

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #45 on: 15 Nov 2019, 10:32 pm »
Important point for all on these SET tube amps. They should be given a warm up time without high voltage B+.

This is the widely accepted "fact" regarding stand-by switches, but it's wrong. Please read Blencowe's article on this topic. You're probably doing more harm than good.

http://valvewizard.co.uk/standby.html

Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #46 on: 15 Nov 2019, 11:21 pm »
Richard, here is what I have gleaned from investigating tube amplification and solid state amplification. Simple triode tubes have a cathode coated with a substance that will release free electrons when the cathode is heated. The a plate with a positive charge that will draw those electrons. a grid that will control the flow of those electrons. when working if a sine wave input to the grid forms a flow of electrons to the plate matching the input sine wave but now with much more energy due to the high voltage. Thus voltage amplification. That is converted back to a high current flow thru an output xfmr. The sine wave is in tact matching the input. Hearing specialists and sound engineers have found that this type of tube amplification tends to exemplify the even harmonics of the fundamental frequency which are accepted well by our ear to brain function thus sounding louder than the db meters indicate.

In solid state devices are solid materials with positive to negative junctions. When a sine wave is entered the solid state material has to give up electrons thus becoming a positive charge or give up protons thus becoming a negative charge. What happens then is positive and negative current flow occurs in two directions. One is called electron flow the other called hole flow or positive flow. This constant interchange causes two sine waves of the original to flow in opposite directions. not only can this cause distortion but causes an emphasis on odd harmonics of the original frequency. This has been found to be irritating to the ear to brain interpretation, thus our brain tends to shut down the level. The musicians have indicated that their solid state amps sound like someone threw a blanket over them. This started a hard long investigation of sound reproduction be sound engineers, electronic engineers, ear specialists to find out the difference. This has led to our great SET low poured tube amps.

I use only vinyl because I have printouts of oscilloscope graphs showing all of the original sine wave missing due to the sampling rate of the digital sampling. I do realize that there is a great difference in the way different sound engineers and recording engineers do their vinyl recordings. Some over emphasize the highs which are very irritating. Some over emphasize the lows and out comes boom, boom, which is also very irritating. With my preamp I can get some control on this  with my tone controls.
With a passive preamp how do you deal with this?

My preamp is an EICO ST84. It uses 12AX7's thru out except for the rectifier. It was a kit when In bought it in 1967. It was a steal at that time because kit building had gone out of interest. I went thru it last year. Most of the carbon resisters were out of specs. replaced the resister, caps and tubes. The EICO ST84 is a highly sought after preamp now. I saw three of them sell on EBAY for over $900.00 last year.

Chuck

Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #47 on: 15 Nov 2019, 11:28 pm »
sonicboom, thanks for your input. That is why I like this interchange of knowledge. We older ones have believed this standby switch thing for a long time.

Chuck

belle harbor

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #48 on: 16 Nov 2019, 12:24 pm »
Having serviced thousands of pieces of audio gear, tube radios, and TVs over the past 60 years I can tell you that standby switching is totally unnecessary.  If you really want tubes to last you need to ensure that filament voltage remains within 5% of rating over all line voltage conditions.  Putting 7+ volts on a 6.3 volt tube will absolutely shorten its life.  Proper ventilation is also very critical.

FullRangeMan

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #49 on: 16 Nov 2019, 05:08 pm »
Having serviced thousands of pieces of audio gear, tube radios, and TVs over the past 60 years I can tell you that standby switching is totally unnecessary.
This careless and neglect attitude to other people equipment is very common in North America even today, including famous hi-end manufacturers, its a general rule.

These past weeks there was a topic at DIY Audio where various members came to conclusion that soft start ramp voltage and a proper HV delay sequence are need to tube amps if one want his tubes lasts longer than the usual 2000 hours, and we know some tubes can be quite expensive.

Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #50 on: 16 Nov 2019, 06:36 pm »
I also have a long background in working on tube amps and tube radios. It is not just the filament voltage that we are talking about. If we connect an old antique tube radio to high line voltages of today we are asking for trouble. My line voltage runs between 122 and 124 volts AC. When an old tube radio is connected to that,
 not only will the filament voltage be too high, think of the high voltage winding. If the radio had been run on 110 volts before with 250 or 300 VDC on the plates of some tubes, think what it would be with a line voltage of 122 to 124 AC.
Note a picture of an easy fix for these old antique radios which I found on Anglefire website
Chuck



Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #51 on: 17 Nov 2019, 02:40 am »
Richard, I seemed to have overlooked your statement about the on line equalizer you use. So, now I understand how you cope with too much high or too much low. At my age I am not very good at using internet music.

 When I was young I had lots of records, but all were lost. Around 15 years ago I was able to buy records for 10 cents each at thrift stores. I would just throw away the bad ones. It is surprising how many very good records I have. The top of the line recording company was "COMMAND" records. They even got into cutting records from 35 MM film that performances were recorded on. It is interesting how "real sounding" good vinyl is. Most new vinyl I have tried were recorded off of CD's and very poor audio.

Chuck

FullRangeMan

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #52 on: 17 Nov 2019, 04:05 am »
Most new vinyl I have tried were recorded off of CD's and very poor audio.
The mastering for CDs and vinyl are very diferent.

Chuck Harris

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #53 on: 17 Nov 2019, 05:24 am »
My last post tonight.
 It gives me a great deal of pleasure to see so many good informative posts.
What really is amazing to me is to see how so many of you have so beautifully merged or blended the very new sound technology with the old tube sound technology and having it excite you when it turns out so good for you. I really did not think I would ever see this happen.
Chuck

belle harbor

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #54 on: 17 Nov 2019, 12:02 pm »
Chuck, B+ is not usually an issue unless the design-maximum tube ratings are exceeded.  In terms of vintage tube audio gear, radios, and televisions most were designed to operate at a line voltage of 105-125.  At the higher voltages it is usually the filaments which are going to take the hit.  An elegant solution for those who are concerned is a variac. 

Gustavo, I’m not aware of a careless attitude when it comes to tube equipment.  My service shop could not have remained in business if premature tube failure was an issue.  In my own amp designs 25000+ hours on output tubes is typical while the small signal tubes last “forever.”

FullRangeMan

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Re: My Low Watt SET amp & High Sensitivity Speaker Journey ~
« Reply #55 on: 17 Nov 2019, 06:57 pm »
Gustavo, I’m not aware of a careless attitude when it comes to tube equipment.  My service shop could not have remained in business if premature tube failure was an issue.  In my own amp designs 25000+ hours on output tubes is typical while the small signal tubes last “forever.”
Great, I will send you my tubes for you bless them.