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Barry
11-06-2009, 17:41
Leak Troughline Stereo vs. Quad FM3. First impressions


Introduction

This report describes the comparison I have made between a newly acquired Leak Troughline tuner and a Quad FM3 tuner that is in regular use. I had intended this comparison to be part of a larger survey of ‘classic’ tuner designs, but for reasons that will become apparent I am reporting my first impressions. Depending on the response to this report and with further experimentation I hope to expand the survey to include two valve designs and two solid-state designs.


The contestants

Leak Troughline Stereo tuner.

Encouraged by Neil’s excellent writing on this tuner I recently acquired a sample in excellent condition, s/n 56184. This came fitted with Leak’s own stereo decoder; a solid-state design using germanium transistors. Original Mullard brand valves (with the shield badge) were fitted and the vendor stated that the tuner had been recently serviced. Two flying leads fitted with cheap quality phono plugs provide stereo output. The RF aerial input is via screw connections, permitting the use of 75Ω or 300Ω designs.

The Troughline tuner has an RF sensitivity of 1.5μV for full limiting. I can’t find the output level, apart from fact that the voltage level from the cathode follower feeding the stereo decoder is 1V. It turns out that the stereo output is considerably less than this; estimated to be ~25mV. The captive 2-core mains cable is fitted with an American style plug, with two flat blades; complicating installation.

Quad FM3

This is Quad’s first solid-state tuner, replacing the FM2 valve design. This particular sample (s/n 32352) has been in regular use for 30 years and has had an estimated cumulative use of ~ 27000 hours.

The RF sensitivity is 1μV for -30dB noise level, and provides an output of 100mV for 30% modulation.


Methodology

With radio being an ephemeral medium it is difficult to perform A-B comparisons. Whilst it is easy to be misguided by A-B comparison, it is the only simple way to realistically assess the sound quality of tuners fed by the same signal. To this end the signal from a roof mounted 3-element Yagi was divided between the two tuners using a simple resistive splitter. The signal loss through the splitter is calculated to be 4dB at worse.

The output from each tuner was fed to a separate input of a Quad 44 preamp: these inputs initially having a sensitivity of 100mV and a loading of 1MΩ. With both tuners tuned to the same station, by simply switching inputs it was easy to compare their performance. The power amplifier was a modified Quad 405 feeding Quad ELS 57 speakers.


The results, Day 1

Despite the Leak having a lower sensitivity, some 13 stations could be received. Obviously not all of these were at full strength, but all were sufficiently strong that noise was not a problem. The signal from the more powerful transmitters (BBC Radio 2, 3 and 4, as well as local radio) was sufficiently strong that the gap of the EM84 tuning indicator was almost closed. The output of the Leak was considerably lower than that of the Quad. The Quad 44 uses a stepped attenuator as volume control. To obtain a similar listening level, I found that the difference in volume control setting translated to a difference of 13dB; implying the output level from the Leak was only ~ 22mV.

The listening started with speech on Radio 4. I regard the human voice, whether spoken or sung, to be an excellent test of tonal fidelity, especially in the mid range. From my memory of a previous sample of the Troughline Stereo, as well as from those users reporting on the web and in magazines, I was expecting the sound to be warmer and more open than that of the Quad. I was therefore somewhat shocked to find the sound to be not only warmer, but also warm and woolly – positively ‘pipe and slippers’! This was not simply a case of the Quad displaying a dryer and less forward bass; all voices male or female through the Leak were unnaturally ‘chesty’.

In other respects the performance of the Leak was fine: good stereo spread with focus and depth. The soundstage from the Leak came no further than the plane of the speakers, whereas from the Quad the soundstage started a little forward of the speakers. Frequency range was satisfactory: it was the balance that was troubling me.

I then retuned to Radio 3 for a concert of Chopin piano works. Again through the Leak the piano sounded soft (no pun intended) and distant. Sweeter than the Quad maybe and perhaps more relaxing at lower volume, but the Quad was more involving and engaging. Through the Quad, the piano had the correct percussive nature and to me sounded more realistic. The Leak gave a good impression of height during sung Lieder, one could easily imagine the height of the vocalist, but again the vocal registers seemed to be unnaturally depressed. It was not really possible to assess the acoustics of the venue through either tuner but this is more a comment on the recordings rather than the BBC, who are usually very good at mike placement for this.
One recording was ’live’ and through the Quad one could hear individual hand claps in the applause at the end, whereas the Leak tended to make the applause sound like ‘rustling cellophane’.

Tuning to Radio 2, I was able to listen to Dylan’s ‘Like Rolling Stone’. Through the Leak, Dylan’s nasal ‘whine’ was suppressed (don’t get me wrong I love Dylan but he doesn’t have the best of voices) and a number by Chrissie Hind was relaxing but not involving, and again her voice seemed too ‘chesty’. The Leak did make a good job of Phil Collin’s percussion, so attack and transients were all there.

Returning to Radio 4 I found both Bob Brydon and Charlotte Green’s voices to be unnaturally deep.

The Leak needs a good twenty minutes to ‘warm up’, whereupon the sound stage moves more forward a little and also becomes a little wider and deeper.


Day 2

I did a bit of rearranging; feeding the Quad tuner into a tape input set to 300mV (at 120kΩ) and moving the Leak to a radio input (100mV at 1MΩ). Now the volume levels were similar to within a click or two on the volume control.

Listening started with Radio 2. The Leak gave Dire Strait’s ‘Sultans of Swing’ a nice full sound with plenty of ‘swing’. Next up was Dionne Warwick’s ‘Message for Michael’, there was too much bass and her voice sounded distant. Again Chrissie Hind’s voice was too chesty. The only time I preferred the Leak was when playing the Righteous Brothers’ ‘You’ve lost that loving feeling’, here the bass heavy balance added to the Spector ‘wall of sound’.

Retuned to Radio 3, for today’s Chopin concert. Again this was enjoyable, but the Quad made the piano sound more realistic. Finally to Radio 4 for the afternoon play. The BBC always does a good job here, and the Leak portrayed width and depth and atmosphere well. At times the added warmth helped the intimacy, but again most of the voices seemed too deep.


Conclusions?

Well I am perplexed and a little disappointed. I was expecting the Leak to be warmer and more open than the Quad, but to be honest the balance of the Leak is such that there is bass ‘bloom’ at best and bass ‘boom’ at worse. Not what I was expecting at all. Maybe the internal decoder is letting the Leak down – I don’t know.

I shall persevere, maybe the Quad is bass weak, quite likely, but voices through the Leak are definitely wrong at the moment. Any comments will be gratefully received, as I feel the Leak is capable of performing better than it has done so far. To be continued....

Barry

Spectral Morn
11-06-2009, 18:01
Hi Barry

Hope you don't mind me moving your excellent item as I think its more about sound than history so SOG is where I think it should be.

WOW....very well written and I am a bit surprised at the outcome so far.... Warm and woolly is not how my Trough-Lines sound. However in saying that the Trough-Line 2 is usually used with the EAR decoder and the Rodney Hanna Trough-Line is modified in the main by using a modern Motorolla decoder, rather than the original which didn't work anymore.

It is possible than the ECC 88 in the output stage might need replacing...you could try that....if you have a spare one.

I want to read more...


Regards D S D L

shane
11-06-2009, 19:55
From memory, the decoder of the Leak is less than wonderful. Does the leak have a mono output which bypasses the decoder? If so, it might be worth doing a similar comparison with the Quad switched to mono.

Spectral Morn
11-06-2009, 21:31
From memory, the decoder of the Leak is less than wonderful. Does the leak have a mono output which bypasses the decoder? If so, it might be worth doing a similar comparison with the Quad switched to mono.

Hi shane

What you are referring to is the FM multiplex output, its not a mono output but rather carries multiplex info to an external stereo decoder. However the Trough-line stereo does not have this feature as it had the then new Philips based decoder. Only mk2 and mk3 have this output.

Barry had mentioned that he might replace the internal decoder for a more modern one.... However while doing that will raise the performance of the Trough-Line he has it would defeat the purpose of his project...as I understand it which is to compare original examples of these tuners.


Regards D S D L

Barry
11-06-2009, 23:26
Hi Neil and Shane,

Thanks for your comments on what is intended to be an interim report. Clearly my Leak is not performing as well as it should, so I want to correct this first, before I consider trying a change of decoder.

Thanks Neil for the suggestion regarding the ECC88 valve. I have several, so I will try it out. If successful, I might even try a bit of tube 'rolling', but first things first.

My intention, Shane was to compare Leak, Quad FM2, FM3 and Sugden R21 tuners as designed. Two of them will be on loan; so I can't fiddle with them. Maybe afterwards, I might try a couple of mods that have been suggested to my FM3, and to consider a change of decoder in the Leak.

First, I need to get the Leak up to scratch. 'Warm and woolly' was my intial and immediate impression - things improved a bit after the Leak had been running for 20minutes or so, but even then the sound was contrary to what you and the rest of the world hear with your Leaks.

Regards
Barry

Spectral Morn
11-06-2009, 23:31
I am looking forward to the next part of this Barry. Keep up the good work.


Regards D S D L

SPS
12-06-2009, 09:28
very interesting, i have a couple of later troughlines a stereo and a mono fitted with a studio 12? decoder, the latter sounds much better

i have no issues with bass boom, but the output is slightly light in the treble, which gives a bassy sound ,
i have a quad tuner somewhere.. i should give that a go..

nice write up...

cheers steve

DSJR
12-06-2009, 16:44
Excellent comparison. I suspect the stereo decoder is what's doing "it" and not the tuner itself. Apparently, the decoder in my FM2 does similar things to an otherwise good valve tuner. I'll go in the loft and get the FM3 out, as it doesn't like the low (20K) input impedance of the AVI pre but should love the 100K or so of the Croft.

The FM3 always had a "correct" but slightly small scale sound compared to its peers by Revox, Pioneer and Yamaha (I think the lovely, huge Sansui's and Accuphase's may be just a little too "charming" to be true, but it's a long time since I heard any). It's such a shame how UK radio quality has deteriorated on the popular music stations. Radio 1 has fairly recently gained some bass and lost the worst of the hard-edged "shouty" quailty to its presenters, but the mid is still squidged up with little treble and radio 2 still sounds bland most of the time due to excessive compression. I don't think a wonderful tuner is going to cure those ills any time soon sadly.

I must say that the Delta 80 sounds much better with the Croft, but there's a spatial flatness to it I don't much care for. There's a sort of feeling of space in a good broadcast, but done with cardboard cut-outs rather than three dimensional objects (please excuse the horrid descriptions here).

I look forward to more instalments in the various tuner saga's :D

spendorman
12-06-2009, 17:52
Excellent comparison. I suspect the stereo decoder is what's doing "it" and not the tuner itself. Apparently, the decoder in my FM2 does similar things to an otherwise good valve tuner

I think the same of my Quad 1 FM tuner +decoder. Sounds good without decoder, decoder seems to spoil things. I never got round to building a replacement decoder for the FM1

Barry
12-06-2009, 18:10
Excellent comparison. I suspect the stereo decoder is what's doing "it" and not the tuner itself. Apparently, the decoder in my FM2 does similar things to an otherwise good valve tuner. I'll go in the loft and get the FM3 out, as it doesn't like the low (20K) input impedance of the AVI pre but should love the 100K or so of the Croft.

The FM3 always had a "correct" but slightly small scale sound compared to its peers by Revox, Pioneer and Yamaha (I think the lovely, huge Sansui's and Accuphase's may be just a little too "charming" to be true, but it's a long time since I heard any). It's such a shame how UK radio quality has deteriorated on the popular music stations. Radio 1 has fairly recently gained some bass and lost the worst of the hard-edged "shouty" quality to its presenters, but the mid is still squidged up with little treble and radio 2 still sounds bland most of the time due to excessive compression. I don't think a wonderful tuner is going to cure those ills any time soon sadly.

I must say that the Delta 80 sounds much better with the Croft, but there's a spatial flatness to it I don't much care for. There's a sort of feeling of space in a good broadcast, but done with cardboard cut-outs rather than three dimensional objects (please excuse the horrid descriptions here).

I look forward to more instalments in the various tuner saga's :D

Hi Dave,

Agree with you about the deteriorating quality of radio these days - not just popular radio stations, but BBC Radio 3 as well (use of the dreaded Optimod limiter). Know what you mean regarding 'cardboard cut-outs'; that was exactly how I described the sound of early CD players.

Yes, the Quad FM3 like an input which loads the tuner with at least 50kOhms.

Have just noticed your change of avatar - now this is getting serious!

Regards
Barry

DSJR
12-06-2009, 18:14
Well, I got the FM3 back out (it's s/n 28,***) and gave it a quick listen (I'll give it more time over the weekend..

http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF0443.jpg

On Radio 4 it sounds excellent, with the right kind of dryness you get with this station (the Spendors help here no end of course).

Radio 1 at this time on Friday nights is usually better than at other times and so it was. I love some dance music (although it's getting VERY monotonous these days). The way the music pumped up and down in level with the beat is frustrating though and puts me off listening after a few minutes.

As for Kiss FM, it was unlistenable - squidged dynamics, no top and no bass - ughhhhh!

Radio 3 is always pretty good at worst, but I don't listen to this station much, even now..

The Grand Wazoo
02-05-2011, 08:12
From The Grave

hifi_dave
02-05-2011, 10:08
Back in the 80's - early 90's we sold heaps of Leak Troughline tuners, so many that we had a 6 month waiting list. Each one was re-furbed and aligned and a quality decoder added to both the mono and stereo models by Glenn Croft or GT Audio.

This considerably improved the mellow presentation of the standard tuner as the fitted decoder wasn't up to much plus the circuitry benefitted from being re-aligned.

DSJR
02-05-2011, 10:17
My Quad FM2 needs a new type decoder, and I believe the "One Thing Audio" one fits directly inside.

The FM3 emits a hum field which disturbs the Croft phono stage, so for the time being I've returned to the Cambridge T55. The distortion on one channel I heard a while ago with the Arcam tuner may have been disengaged wiring in the Croft - MY fault when I fitted different sockets to the back... :mental:

ersel
24-03-2020, 17:37
I have actually the same problem as the OP, - woolly and overblown, boomy bass.
This happens with one out of the two Leak II Troughlines that I own, when external solid state decoder (optimized for vintage tube tuners) is used via the MPX-out of the Leak.

When not using the MPX-out into decoder, but relying on the RCA mono out cable, from Leak and then splitting it into two channels, with simple RCA splitter, the problem with bass disappears (albeit not having true stereo signal from the tuner being the trade-off). The bass is just correct, huge difference, in comparison to MPX out into stereo decoder.
This Leak II has been overhauled, cleaned, and large cap has been replaced and large black Mundorf cap has been put there instead. Probably similar or same specs, but that has to be checked.

First Leak that has not been touched, with original inner parts and components of the circuitr. It has noticeably lower output level via MPX into the stereo decoder than the other Leak II.
It, however, sounds just far better out of MPX output into the very same stereo decoder, the difference is striking, even if the bass has slight hint of not being entirely tight or articulate, but still - well, ok.

Very puzzled by this.
Hard to find the certified tech outside of UK, Leak II is tricky to align properly from what I have read (proper alignment is perhaps irrelevant in this context) and TdP decoder is nowadays something of an unobtanium.

Any advice and opinion is warmly welcome.

Barry
24-03-2020, 20:07
I've noticed that my OP was written nearly 11 years ago!

Despite my intention to experiment with tube rolling (only partially successful) and try a different MPX decoder (not persued), I have abandoned my Leak Troughline Stereo tuner, which now remains in storage.

Since then I have acquired a Quad FM2, a Cambridge T55 and a B&O 1700 tuner. Both the Cambridge and B&O designs are excellent, and the Quad FM2 is an interesting alternative to the FM3; presenting a very slightly warmer and 'intimate' performance.

But these days, apart from wanting to hear a Magnum Dynalab tuner, I'm more than satisfied with the Quad FM4 which I now use.

Made in 1968
25-03-2020, 06:39
FM-3 is a great tuner.

The best looking tuners of all time to me were the Quad 'FM-3' & Naim 'NAT101'

ersel
25-03-2020, 14:11
I've noticed that my OP was written nearly 11 years ago!

Despite my intention to experiment with tube rolling (only partially successful) and try a different MPX decoder (not persued), I have abandoned my Leak Troughline Stereo tuner, which now remains in storage.

Since then I have acquired a Quad FM2, a Cambridge T55 and a B&O 1700 tuner. Both the Cambridge and B&O designs are excellent, and the Quad FM2 is an interesting alternative to the FM3; presenting a very slightly warmer and 'intimate' performance.

But these days, apart from wanting to hear a Magnum Dynalab tuner, I'm more than satisfied with the Quad FM4 which I now use.

I think the problem with Leak II might be the matter of simply getting it to the knowledgeable tech... how important is the decoder (which decoder is used) might also be a factor, but several have proven to work well with it... It does deserve a custom made one, á la TdP.

Barry
25-03-2020, 17:16
Yes I agree, the original Decoder fitted into the Troughline Stereo model (aka Mk. III) is very poor, and I am sure responsible for the wooly bass.

I had intended to replace it with one using a Motorola chip, but never got around to it.

The only advice I can offer is to have your second Mk.II looked at by a competant service engineer. There are one or two Members here who have the neccessary knowledge (and perhaps also the required test gear). The alignment notes for the Leak Troughline tuners can be found here: http://44bx.com/leak/TLalign.html

Spectral Morn
25-03-2020, 19:32
Yes I agree, the original Decoder fitted into the Troughline Stereo model (aka Mk. III) is very poor, and I am sure responsible for the wooly bass.

I had intended to replace it with one using a Motorola chip, but never got around to it.

The only advice I can offer is to have your second Mk.II looked at by a competant service engineer. There are one or two Members here who have the neccessary knowledge (and perhaps also the required test gear). The alignment notes for the Leak Troughline tuners can be found here: http://44bx.com/leak/TLalign.html

I have a Rodney Hanna one fitted with a motorola chip, works very well.

ersel
18-04-2020, 15:29
I have a Rodney Hanna one fitted with a motorola chip, works very well.

These decoders are - well - not easy to find these days - TdP decoder is pretty much unobtanium these days.

For what is worth - the mono performace out of, I think both of my Leak IIs, is spot on, and simple RCA splitter gives you faux-stereo (well, rather duplicated mono) performance where the bass is tight and articulate.
The sound of the mono is just missing that last part of the stereo FM broadcast.

There is a guy in the US who makes a custom decoders for the tube - valve FM tuners, and says that the sound coming out of these tuners is pretty much what you get out of the decoder, although my small objection would be that the tuner itself got to be a good one to begin with.

Columbo
19-04-2020, 00:10
Pretty sure the TdP decoder used the standard Motorola MC1310 chip for the main decoding duties.

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