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Old 18th Jan 2020, 11:30 pm   #1201
ajgriff
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Default Re: The Audiophoolery Thread.

.... and a fiver in 1989 became 12.53 by 2019. Still an inexpensive Radford though.

Alan
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Old 18th Jan 2020, 11:59 pm   #1202
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Default Re: The Audiophoolery Thread.

The Radfords appeal from the technical point of view, the triode-pentode phase splitter representing genuine and pragmatic development of the basic 5-20 theme, as opposed to merely tweaking an application note. The Quads strike me as stretching minimalism a little too far, with the well-known KT66 unwisely-high grid resistor drawback being a manifestation of this.

What all three represent is the art and science of getting output transformers to work well over the audio range- something that just doesn't trouble the modern transistor amp designer, and saves him/her a lot of money, time and brow-furrowing!
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Old 19th Jan 2020, 4:50 am   #1203
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Default Re: The Audiophoolery Thread.

Radford was principally a transformer designer/manufacturer. Add in Bailey's circuit design and you had a formidable combination very well suited to handling the 'fun' areas of valve audio amplifiers. A phoolery-free zone.

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Old 19th Jan 2020, 10:41 am   #1204
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Default Re: The Audiophoolery Thread.

Agree entirely. The performance of a valved power amplifier is mainly determined by the output transformer.
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Old 19th Jan 2020, 12:33 pm   #1205
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Default Re: The Audiophoolery Thread.

Has the Cardas Sweeper record been mentioned yet? I wouldn't normally advocate posting in threads without reading previous contributions but there are over 1200 of them. I accidentally acquired one of these records (mercifully at no cost) and find it quite extraordinary. This is a quote from the marketing blurb:

"The Cardas Frequency Sweep and Burn-in Record is a unique tuning tool for system set-up, diagnostics and maintenance. It was produced by George Cardas and mastered by Stan Ricker. The 'Sweeper', in addition to the standard tones, includes relative and absolute polarity checks, vocal channel identification and frequency sweeps that ultrasonically clean the cartridge stylus and degauss the entire system. And, locked, pink noise grooves that repeat endlessly, blank plateaus, even a sync label to check platter speed. All on a 180 gram pressing with a smiling Stan cover."

The bit I like in particular is the concept of degaussing the entire system. I'm not sure I want my moving magnet or moving coil cartridges degaussed let alone the rest of the system. Has anyone else come across this example of gross audiophoolery (my view) or have any thoughts on the subject? I think I'm rather relieved that the smiling Stan cover didn't come with my copy.

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Old 19th Jan 2020, 1:41 pm   #1206
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Default Re: The Audiophoolery Thread.

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Originally Posted by turretslug View Post
... The Quads strike me as stretching minimalism a little too far, with the well-known KT66 unwisely-high grid resistor drawback being a manifestation of this ...
Given that the KT66s' anode and screen voltages and dissipations aren't pushed to the maximum in the Quad II, the 680k grid leaks work OK as long as a) they haven't drifted high in value (but after a few decades the Erie carbon comps will have) and b) the interstage coupling capacitors haven't become leaky (but after a few decades the Hunts paper-in-oils will have). The amp can suffer, but it's not really a circuit issue, it's that decades down the line the components are giving up the ghost.

Other manufacturers also worked close to the limit. Stephen Spicer in his book Firsts in High Fidelity describes perhaps the most notable example of this. Harold Leak wanted to spec his TL/12 Plus amp (replacement for the legendary TL/12) which would be based on Mullard's new EL84 at 12 watts output with, like all the Point One range, 0.1% distortion. Mullard themselves had said in their 5-10 design that a push-pull pair of EL84s could deliver 0.3% at 10 watts or 1% at 14 watts. Leak breezily assumed that they had built the EL84 with the same engineering safety margins that previous manufacturers had always put into their valves (and their data sheets). So to get what he wanted he over-ran them a bit. Unfortunately for him the EL84 was perhaps the first example of a valve which was really tightly manufactured. You could run it at the design maximum, but if you went even a little beyond that it would fail. Leak already had plenty of TL/12 Pluses and Stereo 20s in the field when they started to come back with catastrophic 'burn ups'. A substantial redesign was forced on the company, including a whole new output transformer. The output spec was dropped to 11 watts and to be honest seeing 0.1% distortion at that power from this amp is a rare thing indeed.

If you want an example from Radford then take the bottom off an STA25. There's a picture of one here http://hifi70.com/wp-content/uploads/2015/10/top2.jpg part of which I've cropped out and attached. It's had some work done, including replacement of the ringed resistors. Note the scorching on the pcb underneath them. That's quite typical. The resistors are R32 and, on the right hand pcb, R10 as well. R32 is part of the potential divider which sets the screen voltage for the ECF82 pentode. It would originally have been a 68k carbon film Iskra rated for 1 watt maximum. Radford's circuit diagram shows it running with 265V across it, so V^2/R is more than a watt. And if your mains voltage is a little high (or, heaven forbid, your toddler has rotated the all-too-accessible mains voltage selector) and/or the resistance is a little low and/or the ECF82 screen grid isn't drawing quite as much current as it should then the resistor will run hotter still. As the scorching shows. It really should have been a wirewound.

Long story short - quite a few amp manufacturers built up to, and sometimes beyond, the component manufacturers' specs. These specs were often generous and (except for Leak) there was rarely a problem until long after the expected lifetime of the equipment.

Cheers,

GJ
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Old 20th Jan 2020, 6:30 pm   #1207
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Default Re: The Audiophoolery Thread.

I asked my professional Audiophriend if he had the Cardas Sweeper record and the reply was no but he aspires to having one. He says that new top-end cartridges take 10 to 20 hours before sounding their best and therefore the locked pink noise grooves would be a great help when preparing for a customer demonstration, allegedly. I'll let you know if he manages to explain how the record degausses a magnetic cartridge.

Len
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Old 20th Jan 2020, 9:18 pm   #1208
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Default Re: The Audiophoolery Thread.

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I'll let you know if he manages to explain how the record degausses a magnetic cartridge.
Love it!

Is there another record to re-magnetise the magnet in the cartridge? It won't be very much use after its been degaussed

David
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Old 20th Jan 2020, 9:28 pm   #1209
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Default Re: The Audiophoolery Thread.

Quote:
It won't be very much use after its been degaussed
OK for a crystal one!!!
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Old 21st Jan 2020, 12:09 am   #1210
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Default Re: The Audiophoolery Thread.

Ah - but then you would need a de-poling record
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Old 21st Jan 2020, 12:58 am   #1211
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Default Re: The Audiophoolery Thread.

Quote:
Originally Posted by GrimJosef View Post
...there was rarely a problem until long after the expected lifetime of the equipment.
And this is surely the point. The youngest original Quad II is over fifty years old. Peter Walker said that if an amplifier lasted ten years, it had fairly done its job. Most failures are due to the same few weak points, not spread all over the unit at random. This is not a failing - it indicates that the general standard of design and construction is excellent.
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Old 21st Jan 2020, 1:55 am   #1212
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Default Re: The Audiophoolery Thread.

The faults we know so well would not have been known so well back in the day. They thought they were using good quality parts, and for the time, they were. They lasted a reasonable time. We just want to see things working after an unreasonable time.

I'm not sure about those Hunts little brown capacitors, though. They used to crack up in fairly short order and must have fed and clothed many a repairman's family. They were known about back in the day. They were failing in older sets while they were still being used in new sets.

It's amusing that back in the day you got 6 months warranty on the set, but only 90 days on the valves.

David
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Old 21st Jan 2020, 2:03 am   #1213
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Default Re: The Audiophoolery Thread.

For "aesthetic" [knob twiddler post 1195*] read psychological. As I keep saying/implying it's really only "umans" that agonise over what they see or hear. It is indeed a technical production, signal wise but the output is then translated in the brain via our emotional circuits! This is very well expressed by
Uncle Bulgaria [in post 1194*]. ie "Remember You're A Womble!"

Dave W

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Old 21st Jan 2020, 10:25 am   #1214
Craig Sawyers
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Default Re: The Audiophoolery Thread.

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Originally Posted by Radio Wrangler View Post
The faults we know so well would not have been known so well back in the day. They thought they were using good quality parts, and for the time, they were. They lasted a reasonable time. We just want to see things working after an unreasonable time.

I'm not sure about those Hunts little brown capacitors, though. They used to crack up in fairly short order and must have fed and clothed many a repairman's family. They were known about back in the day. They were failing in older sets while they were still being used in new sets.

It's amusing that back in the day you got 6 months warranty on the set, but only 90 days on the valves.

David
I picked up an Eddystone receiver free around fifteen years ago, with the idea of fixing it up and using it. However it was deaf, and a quick inspection showed that it was infested with those small brown Hunts capacitors, all of them cracked, falling to pieces, and needing to be replaced. But Eddystone built these receivers up from a bare chassis with tight point to point wiring. Many of those nasty caps were buried deep, so it was going to be a seriously major job to replace them all.

I sold it instead.

Craig
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Old 21st Jan 2020, 1:00 pm   #1215
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Default Re: The Audiophoolery Thread.

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Originally Posted by Radio Wrangler View Post
... I'm not sure about those Hunts little brown capacitors, though. They used to crack up in fairly short order and must have fed and clothed many a repairman's family. They were known about back in the day. They were failing in older sets while they were still being used in new sets ...
Fortunately there's only one of them in the Quad II and it isn't working very hard. It runs between the screen grids of the EF86s. This is quite a neat approach since, as Phil Moss points out, it means that differential mode signals (i.e. the music) are decoupled at the screens by the capacitor but common mode signals (which are typically noise) are not, and the resulting local NFB therefore suppresses them. It also means there's little DC across the capacitor. So if the shell does split and the cap goes a bit leaky the consequences aren't dreadful. I can't ever recall seeing one, split though some are, cause a serious problem.

They were widely used though. Here's a black one in a Beam Echo DL7-35 https://farm2.static.flickr.com/1402...8c29d6e4_o.jpg. Here are some in a Leak Point One pre http://listeninn.com/Pictures-Used/U...-Stereo-10.jpg. Here are some brown ones in an RCA LMI-32216A http://www.saturn-sound.com/images%2...ing%20side.jpg. Here are some 'orrible 'unts (her words ) in Kat Manton's Pamphonic 1004 https://www.vintage-radio.net/forum/...3&d=1277245073. Rogers seem to have resisted them though, using the impeccable Mullard mustards instead, and Radford stuck largely with Wima for their film capacitors.

Cheers,

GJ
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Old 23rd Jan 2020, 7:10 pm   #1216
Malcolm G6ANZ
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Default Re: The Audiophoolery Thread.

For your RF feed you can either pay 45 for a twin outlet treated with Deoxit https://www.russandrews.com/aerial-supersocket/
And don't forget to burn in the coax https://www.russandrews.com/v21-aerial-cable-male-coax/


Or the same MK socket from Amazon for 5
https://www.amazon.co.uk/MK-K3522WHI.../dp/B005BDASRQ

Malcolm
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Old 23rd Jan 2020, 7:47 pm   #1217
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Default Re: The Audiophoolery Thread.

We'll burn in your speaker cables for you.

https://www.russandrews.com/burn-in/
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Old 23rd Jan 2020, 8:38 pm   #1218
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Default Re: The Audiophoolery Thread.

OFS!
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Old 23rd Jan 2020, 8:46 pm   #1219
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Default Re: The Audiophoolery Thread.

It gets even sillier https://www.russandrews.com/super-burn-in-plus/ the word "will" is used a lot, if it doesn't can I sue? (I would sue my own brain for being so gullible and stupid).

I do like the 5 MK socket, the angled approach means my plugs won't stick out as far, good old engineering job.
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Old 23rd Jan 2020, 9:05 pm   #1220
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Default Re: The Audiophoolery Thread.

The word "will" is actually not used a lot, if at all on the RA website, or any other UK audio website for that matter. RA was the subject of a vexatious complaint to the ASA regarding the wording and claims regarding their mains cables. After a long battle I succeeded in getting the ruling overturned by carrying out a day of tests at an EMC lab.

Chord have also been the subject of a similar claim to the ASA.

The entire upshot of these battles is that wording on audio websites has to be very carefully indeed. You can say things like "we find that" and variations on that, but never ever that a purchaser will hear a certain benefit.
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