UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Reply
 
Thread Tools
Old 13th Nov 2023, 11:07 pm   #1
samjmann
Heptode
 
samjmann's Avatar
 
Join Date: Feb 2014
Location: Nottingham, UK.
Posts: 639
Default Quad 405/34 or Technics AA.

From what I understand Technics AA is a type of class A to B amp. The SE-A1000M2 I have at the moment uses this. I'm thinking about a change and wondered about a Quad 405/34 or maybe a 77 integrated.

My Technics is 70w against the Quad's 100. I don't need any more than 50w in my listening room in reality.

What started all this was listening to my friends Sansui AU-919. I de black-flagged this plus a lot of other work a few years ago. I loved the sound of it. I had the amp for months on my own system, and also on a pair of Shahinion Hawks.

The Technics has a STK output module, which sometimes gets sniffed at...

Any thoughts from the wise which to go or maybe stick with what I've got already!

SJM
__________________
It's never been right since we've had it...
samjmann is online now   Reply With Quote
Old 13th Nov 2023, 11:55 pm   #2
knobtwiddler
Octode
 
Join Date: Mar 2016
Location: London, UK.
Posts: 1,019
Default Re: Quad 405/34 or Technics AA.

Seeing as the Technics has lovely meters and - I suspect - a decent PSU, why not simply replace the STK PCB with a Hypex NC500 module?

0.0002% THD+Noise

https://audioxpress.com/article/fres...-on-a-flagship

The Hypex has even better tech specs than the Benchmark AHB-2.

edit - I just did more reading on the Hypex review and saw that it was tested without the front end buffer and at low gain, so he did 'cheat' the measurements a little. Either way, at whatever gain and buffer or not, retrofitting a Hypex into a classic amp chassis that has nice meters would be fun IMO. But each to their own!

Last edited by knobtwiddler; 14th Nov 2023 at 12:13 am.
knobtwiddler is offline   Reply With Quote
Old 14th Nov 2023, 12:18 am   #3
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,662
Default Re: Quad 405/34 or Technics AA.

That's the problem some people have with hifi. The grass is always greener...

One way lies the curse of the flying dutchman, always driven to move on. The other way is t get yourself something pretty decent, forget about wanting to have the best (no-one has ever decided just what that is, anyway) and get on with listening to some music. People choosing this seem happier and also wealthier.

Most of the concepts being bandied about in high hifi circles are mostly imaginary, chosen to be attractive to the mind and the eye, so it is easy to be hooked, either coming to imagine the things the magazines and websites rave about hearing, or pretending to do so in order to not seem cloth-eared. That purple prose is intended to grab you by the pride ans swell their ranks, and their coffers.

It takes a lot of self control and objectivity to ignore them and to accept what your own ears tell you. If you can't tell the difference, then you can't tell the difference. Spend what you save on your family. This will infuriate the 'true aficionados' because you've rejected their belief system.

STK modules can work quite well, but finding spares whenever one fails is a major difficulty. I avoid the things. It doesn't involve sonic performance but it does relate to the joys of living with things.

Quad 405s are an oddball amplifier. The maths of the current-dumping feedforward bridge work out given a couple of assumptions. Mathematically elegant, the engineering is less elegant. I've heard quite a few, fixed quite a few but never liked them since seeing a few marginal bits in their implementation.

For myself, I've stuck to fairly plain, linear archtecture with discrete devices. As a professional electronics designer, I did my own amplifier for no better reason than I could just for pure egotistical reasons.

Avoid fancy devices with no easy workarounds. Steer clear of fancy claims of new principles and surprising new class letters. Really good straight forward amplifier designs have been on the go for a few decades. Those that don't 'do' something to the sound are branded as 'sterile' by the aficionados, but I thought they were wanting to hear what was on the record?

Have the bravery to form your own opinion.

Bravery is needed because the opinionated will see you as a challenge, and attack you.


Transistor amplifiers use more complex structures than valve amplifiers and rely on large amounts of feedback to correct the more abrupt changes in transfer function. A downside of this is they don't behave nicely when hit with transients inevitably contained in real music. So you will actually benefit if you have much higher amplifier power capability than you'd typically use with a valve amp. It looks unnecessary, it looks inefficient, but it de-fuses a real drawback. Also, running too small transistor amps into a lot of clipping is a popular way of burning out tweeters at parties. Bigger amplifiers doing less clipping actuall stress the little drivers less.

Everyone is trying to get you to get one of whatever they have. It flatters their ego and it makes them feel less insecure over their choice - and staves off a bit of buyer's remorse. Somewhere in all the cacophony of advice are a few quiet voices saying non-dramatic things, but they are easily overlooked in the onslaught of shouted superlatives and promises of revelations. The snakier the snake-oil, the louder the shouting.

Remember, it's supposed to be for fun and enjoyment.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 14th Nov 2023, 10:23 am   #4
Beobloke
Heptode
 
Join Date: Oct 2007
Location: Southampton, Hampshire, UK.
Posts: 808
Default Re: Quad 405/34 or Technics AA.

Stick with the Technics.
Beobloke is offline   Reply With Quote
Old 14th Nov 2023, 11:10 am   #5
samjmann
Heptode
 
samjmann's Avatar
 
Join Date: Feb 2014
Location: Nottingham, UK.
Posts: 639
Default Re: Quad 405/34 or Technics AA.

The Hypex modules do give impressive performance. Quite apart from the abundant power and low distortion, the damping factor is off the scale! There probably would be space inside the Technics. I would have to limit the power output if using the old PSU...

The grass is always greener... Just about sums it up!

My hearing has deteriorated. I have tinnitus in both ears, a constant 6Khz whistle in each ear. In level terms, normal listening level of the TV just drowns it out. As regards frequency range, it all falls quiet at 9Khz -both ears. So the perception of sounds should be different now to what it was when I was 18 and could hear up to 18Khz easily. But it's not.
All the records I listened to in my teens and twenties sound just the same. In fact better now on my better hifi.

So there's something rather clever going off with the ears and brain as to what's being heard and the way we actually perceive it. So what I'm saying is, if I do change the system, the AGC, bandwidth compensation, notch filtering at 6Khz and all the other things going off in my head, will no doubt re-align and the end result would be compromised!

So, Should it Stay or Sould it go? I'd always fancied a Quad. The internal construction looks impeccable. But the 405 does appear to have problems, why did they use a crowbar trip? My Dad had a Quad II given to him, it was that that started my interest in electronics. Perhaps that explains it.

RW: At the end of your post you mentioned enjoyment. For less money than a amp change, I could buy a tuner. Daft as it is I've not got one. A lot of my vinyl is worn out and sounds poor on any cartridge. I repaired a tuner/amp a year ago for someone and used it at home for a week on test. I listened to more music than I'd done in ages that week. So maybe that's the way to go.

Thanks to Knobtwiddler and RW for the excellent advice.

SJM.
__________________
It's never been right since we've had it...
samjmann is online now   Reply With Quote
Old 14th Nov 2023, 11:21 am   #6
knobtwiddler
Octode
 
Join Date: Mar 2016
Location: London, UK.
Posts: 1,019
Default Re: Quad 405/34 or Technics AA.

As someone who fixes amps, do you have dummy loads and an FFT analyser? Whether or not the combo will diagnose exactly what it is about the Sansui that you like, I cannot be 100% sure. But if you have both items, you will see that amps vary like mad in terms of noise level / signature, as well as harmonic distortion (i.e. some amps are mainly 2nd, with little 3rd - whereas others can be the opposite).

You don't need to spend a fortune on an FFT machine now that we have high-performance soundcards and freeware software (although you'll want a pad if testing pwr amps!).

You could well find that the one of the amps has a large dollop of 2nd harmonic, a bit like a valve amp, and that makes it more 'likeable'. Or you may not...your ears might prefer something really clinical (we are all different!). What a dummy load + analyser will show you is that no 2 amps are the same. If something has better objective performance, when listening to it, I always think it's better... But would my ears be able to tell in an A/B/X test?

(unless the amp were exceptionally high in distortion + noise, I doubt they would! I tend to agree with the great Peter Baxandall, who felt that by the late '70s, good SS amp designs were at a stage where they exceeded the capabilities of human ears. And let's face it, who else has contributed as much to the art of audio as PB? Blumlein did, but sadly he didn't live long enough to experience Peter Walker's amps)

NB - the only STK amp that I have (a Hitachi) has extremely low THD+N. It's flimsily made (unlike Hitachi 70s designs) and has no right to deliver such good performance, but it does. I prefer my '70s Hitachi, as it has pleasing meters and keeps the room warm in winter.
knobtwiddler is offline   Reply With Quote
Old 14th Nov 2023, 11:58 am   #7
fetteler
Octode
 
fetteler's Avatar
 
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 1,458
Default Re: Quad 405/34 or Technics AA.

David's comments (post #3) are excellent, as is the idea of buying a tuner but since the future of broadcast FM is not at all certain perhaps a method of streaming audio is something to consider as well.

Steve.
__________________
Those who lack imagination cannot imagine what is lacking...
fetteler is offline   Reply With Quote
Old 14th Nov 2023, 12:34 pm   #8
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,662
Default Re: Quad 405/34 or Technics AA.

The wobbliness of the future of the FM band has had the effect of pulling the rug out from under FM tuner prices. You can pick up some rather good ones quite cheaply nowadays.

I have a Revox B261 as well as one of the later Sony 'ES' series. The former cost me £300, the latter £20. Both work well and have some interesting circuitry. The Sony uses the lower frequency components of the demod'd FM to wiggle the tuning of the RF tuned circuits, so they track the transmitter, reducing phase nonlinearity from them.

The problem is the commercialism of the band with the BBC joining in with their own brand adverts. Finding something worth listening to is more difficult nowadays. The commonest denominator seems to win.

On the other hand, the FM band may live longer than we think. Antennae for these wavelengths are inconveniently big, so competition for cellphones, internet connectivity etc doesn't get going until much higher frequencies. So the monetary value of these bands is low and governmental greed is looking for higher frequencies to flog off. So the financial pressure comes from broadcasters themselves looking to cut costs.


Transmitters are expensive to buy but more expensive to maintain and feed. But it's tall masts, their maintenance, inspections and insurance that seem pricier. However, space up these masts has often been flogged off to non-broadcast services who might not want to close down just because the broadcaster lose interest.

It's complex, but the FM band isn't being pushed into oblivion with quite the gusto that analogue TV was.


David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 12:35 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.