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Old 29th Nov 2019, 12:58 pm   #21
Radio Wrangler
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Default Re: Building a 5 valve A.C. amplifier from scratch

Quote:
Originally Posted by Alan's MagicEye View Post
I personally like the "distortion introduced by single ended triode amplifiers,
Now that is a level of honesty rarely seen in audio discussions. I'm afraid we're all much too used to people saying things in a somewhat desperate attempt to justify their preference. Preferences don't have to be justified, people can just get on and enjoy them. It is very difficult (and pointless) to criticise someone who says "Well, I just happen to like it."

The reason behind a preference might not be real, but the pleasure and happiness which can come from it can be perfectly real.

The contention comes in when claims of accuracy, rightness etc are made. Those of us involved in electronics can measure the amounts of distortion, flatness of frequency response, and delay or ringing of transients. We know that some things are much less accurate, but are preferred by some people. We also know that some things don't make any difference which could possibly be discernible also get some people voicing strong preferences. Those preferences are also perfectly OK. Some things work no better, but are nice to have. Some work worse and are still nice to have. I have a model of car which is both famously luxurious and famously unreliable. I can make no rational justification for my choice. It is a simple preference. I'd look a fool if I tried to justify it.

The human race seems ready to polarise on any issue.

The golden ear brigade treats the scientific types as if they are cloth-eared and missing some great truth. The scientific types think the golden ear brigade are deluded or gullible. This can seed unfriendliness.

If the golden ear gang could drop the pseudo-scientific mumbo-jumbo justification and just stick to saying "I prefer this" then even the most extreme hard-science type will find no crack to get a lever in, and they can stick to their world of test-tubes and spectrum analysers.

Astronomers and statisticians must have similar problems with astrology.

David
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Old 29th Nov 2019, 1:05 pm   #22
Alan's MagicEye
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Default Re: Building a 5 valve A.C. amplifier from scratch

Thank you David for your kind comments, this is indeed my position too, beauty is indeed in the eye of the beholder

Alan
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Old 30th Nov 2019, 12:43 am   #23
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Default Re: Building a 5 valve A.C. amplifier from scratch

It is very noticeable that the OP has remained very silent during this lengthy discussion. I wonder if, perhaps, he is completely confused by it. [1]

Perhaps he would like to tell us what his thoughts are on the way this thread has developed.

[1] Back in the 70s I was instructed by my employer to follow the development of Teletext and its application to our system - a 22 channel cable TV system to provide live Stock Exchange prices around the City of London.

Communications facilities were improving and several of the largest users were moving all of their non-trading business away from the City so that the eventual system adopted was a Viewdata system.

The Belgian company BARCO produced our first terminals. Apart from their engineering capabilities, ability to communicate in four languages was essential for employment!

English is widely spoken in Flanders and Barco's location in close proximity to the French border and the 'invisible' frontier which separates Dutch speaking Flanders from French speaking Wallonia didn't make this as difficult as it sounds!

However, this can lead to complacency. Technical descriptions do not necessarily translate into another language easily.

After a meeting in their factory in Kortrijk, I and a colleague were waiting for a car to take us to Lille airport for our flight home and I spotted a large Teletext poster on the wall, purporting to be in English.

I looked at it and asked my colleague to join me. Neither of us could understand it! I picked a short paragraph at random and we 'decoded' it.

When a senior manager popped his head in the door to tell us our transport had arrived we pointed to the poster and translated the gobbledegook into English!

A couple of months later I went to a trade exhibition at Olympia and spotted the Barco stand across the hall - with the Teletext poster on the back wall. I made a beeline for it and found that they had taken our comments on board and employed a technical translator - it was all now in comprehensible English!

Sorry for the lengthy post but something to bear in mind when discussing technical details with someone whose first language is not English!
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Old 30th Nov 2019, 3:46 am   #24
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Default Re: Building a 5 valve A.C. amplifier from scratch

I think, myself Terry, that NOTHING gets past our moderators!! ( to my own frustration sometimes)

This thread has progressed to see who will help a newbie make a very simple 70 odd year old amplifier. ONE, I may say with half decent transformers will still sound excellent!

Myself included, NONE of us have suggested he build the design he has in hand!!
Push/pull 6V6 is a hard argument to beat!!

Sorry mods

Joe
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Old 30th Nov 2019, 3:48 am   #25
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Default Re: Building a 5 valve A.C. amplifier from scratch

I just worked out that my previous post supporting our mods, will be deleted as being OT


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Old 30th Nov 2019, 9:03 am   #26
Alan's MagicEye
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Default Re: Building a 5 valve A.C. amplifier from scratch

Thank you Terry

You make a very good point although the Levente's first post was in excellent English. I must admit to feeling a little guilty for somewhat hogging this thread, it took me too many postings to try and get my point across. I feel that my initial effort to help the Original Poster has gone off in a slightly undesirable direction.

It would be good to know if Levente, the Original Poster is still following the thread or is totally dismayed......

Hopefully amongst the various comments it is possible to extract something of use.

To summarise, I think that we have suggested the following:

The amplifier in the first post seems to be a Pubic Address amplifier and the feeling on this forum was that the design was a little complicated and possibly not very "Hi-Fi".

A good alternative design is the Mullard 5-10 which has a very good reputation and has detailed design information to enable it to be built.

The next suggestion was a copy of the Decware Zen which also has very detailed constructional information but for which there was a lengthy discussion about its technical merits and a little dismay at the original designers' claims. I said in the my final post that when all technical comments had been made that I still personally liked the sound of it.


It would be very good to hear from Levente.

Alan

Last edited by Alan's MagicEye; 30th Nov 2019 at 9:30 am. Reason: Amended text
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Old 30th Nov 2019, 3:01 pm   #27
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Default Re: Building a 5 valve A.C. amplifier from scratch

The OP hasn't visited, or at least logged in, since his last post (4). Since everything subsequent to that post isn't directly relevant to it, he perhaps doesn't feel inclined to comment.
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Old 1st Dec 2019, 9:31 am   #28
Diabolical Artificer
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Default Re: Building a 5 valve A.C. amplifier from scratch

The OP mentions building a valve amp from scratch, which to my mind means designing your own circuit which is pretty easy to do with valves. The problem with building an amp from a schematic you find off the net is that as a begginner you've no idea if it's any good.

First you'd make a list of what you want, EG 10-15w, stereo, without tone controls (makes the build easier) PP OP stage or a rough plan from what bits you have, mainly constrained by what tfmr's you've got.

Next work out roughly what every stage needs, EG OP 50 - 70mA, phase splitter, 10mA, IP, 2mA then build a simple solid state PSU with an L or R C filter.

Wire all valve for heaters paying attention to layout. Build and wire together PP OP stage, then work your way forwards or backwards, whichever way you look at things. If your going to use NFB design for as much gain as possible.

Test and refine.

Lastly build and listen to said amp. All the info you need here - http://www.valvewizard.co.uk/index.html

Andy.
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