Hi all - a friend of mine is using a Thermionic Culture Phoenix valve compressor on the stereo bus at his studio, and complains that when he recalls a mix, the compressor often sounds different despite the settings on the Phoenix being the same. Could this be caused by fluctuations in mains voltage at different times of day affecting the valves? Is there a simple and cheap tool to measure mains voltage (other than sticking the probes of a multimeter into the socket which he doesn't feel comfortable doing) and if this does measure a fluctuation is there anything we can do about it? The Phoenix has recently been back to TC for a checkup, so I don't think the hardware is the issue....

Thanks in advance!

That's Thermionic Culture gear I'm afraid. It sounds WONDERFUL. But it's 'organic' to the point of being a bit different as the week goes on in my experience. All I can suggest is that he lets it warm up for a good while before trying to recall it. And rather than rely on knob positions, use tone where possible to get an exact line up. But this is the reason I stopped using a Culture Vulture I had for mixing. It was just too inconsistent. One day it would sound one way, and then next one side would be noisy, or half a dB down, or just...different. I sent mine back a couple of times to get it checked but that's just the way it always was. It's a shame because the way I work does rely on reliable recalls these days, and I'd have Thermionic gear in my racks if it wasn't for these sorts of problems. I don't know if some of the later designs are better in this respect. Whatever they're doing it sounds really nice. I just don't know if they'd be able to make it more consistent without affecting the cost in a major way. For example using switches instead of those (frankly totally useless) detented pots would be good, but it would add hundreds to the cost of each unit. I think a lot of the weird inconsistencies could be down to some sort of valve related stuff...current, bias whatever.

J

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www.jackruston.com

Well, I know nothing of the equipment save what I have read in SoS but perhaps someone should send the makers a copy of Nelson Jones' Valve Amplifiers!

Making stabilized heater, bias and HT supplies using modern ICs is pretty simple and would add little to the cost of the units.
Bugger! Were I 30 years younger! I can see an nice little earner there! Will, want a lucrative sideline modding vulture giblets?

I know people want the "sound" of valves but surely the challenge is to keep the sound but use modern techniques to overcome their many shortcomimgs and extend their life?

Dave.

Quote wave1:

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...when he recalls a mix, the compressor often sounds different despite the settings on the Phoenix being the same.

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They all do that, Sir! I concur with Jack; the Thermionic stuff sounds great, but it can be quite variable over time as it warms up and the biasing drifts.

Quote:

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Could this be caused by fluctuations in mains voltage at different times of day affecting the valves?

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Possible, but not that likely. I'm not sure how the power supply is configured, but I'd be surprised if the rail voltages vary much.

Quote:

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The Phoenix has recently been back to TC for a checkup, so I don't think the hardware is the issue....

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Au contraire -- if you dig around you'll find similar observations from a lot of users. The Thermionic stuff is wonderfully musical, but you have to use it 'in the moment' and print what you get because getting back to exactly the same place might prove tricky, frustrating and time consuming!

hugh

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Technical Editor, Sound On Sound

"Possible, but not that likely. I'm not sure how the power supply is configured, but I'd be surprised if the rail voltages vary much."

Oh I don't know Hugh? Say 300V as a good guess for the HT supply for a nominal 230V in that gives 330 and 290 max/min for a 10% mains shift.

Then the heaters will be affected as well tho' I would be MOST suprised if kit of that quality had raw AC heaters!

Continuous converting UPS as an answer perhaps?

Dave.

The continuous UPS idea is a good one, Dave, if the mains supply volts really do vary a lot in the studio and if the anode HT really does vary with it. But there are several 'ifs' there and I'd want to hard figures on the incoming mains variation and the anode HT variation before making that kind of investment in a continuous UPS.

The Thermionic stuff is quite old-school in mnay ways -- inherently so -- but I think I've seen some solid-state power supply regulation in them for at least some rails -- although I wouldn't swear to it!

I think the sonic variation is more likely to be an issue of thermal drift... but it's only a guess and I'm not a valve man, really. I gladly defer to your far greater experience.

hugh

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Technical Editor, Sound On Sound

Greater experience Hugh?
Only with guitar amps and NOBODY ever complains about mains variations!

I bit of thought brings me to conclude that a SMPSU as fitted to much high end solid state studio gear now (thus banishing the wall rats I know you love!) is the best solution but 230in 300V ish out supplies are remarkably hard to find.

Dave.

Quote ef37a:

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Greater experience Hugh?
Only with guitar amps and NOBODY ever complains about mains variations!
Dave.

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Apart from Neil Young apparently. His tech's report that that he can hear his Fender Deluxe in a new venue and accurately identify the voltage at the drop down transformer. However, it is the exception that proves the rule

Andy

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When the going gets weird, the Weird turn Pro.

yeah, and eric johnson can hear the difference between nickel jack plugs and brass jack plugs.

Quote Idris Y Draig:

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yeah, and eric johnson can hear the difference between nickel jack plugs and brass jack plugs.

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Who was the guy said he could tell the difference between brands of PP3 pedal batts?

Dave.

Quote ef37a:

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Quote Idris Y Draig:

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yeah, and eric johnson can hear the difference between nickel jack plugs and brass jack plugs.

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Who was the guy said he could tell the difference between brands of PP3 pedal batts?

Dave.

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That's Eric Johnson too. And again apparently confirmed in blind tests. However, both Neil Young and Eric Johnson are VERY familiar with their set-ups and have put them together over many years of experimenting. It's more that they know exactly how their full signal chain sounds and responds to their playing and can hear very subtle differences if anything is changed from what they know. Not sure if that's a blessing or a curse to be honest

Andy

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When the going gets weird, the Weird turn Pro.

Thanks for the contributions, chaps - any suggestions for a handy (and idiot proof)gizmo for measuring mains voltage?

Something like this:

http://www.maplin.co.uk/plug-in-mains-power-and-energy-monitor-38343 < br />

should do - tho' not sure how accurate.

Whether this is your problem is another matter!

I use the very same thing to keep an eye on both incoming mains volts and to measure power consumption and that kind of thing. Seems very accurate and reliable. Mains volts here only seems to vary a few volts either side of 230. Don't think I've seen it lower than about 228 or higher than 233... But the legal supply tolerances allow much greater range.

hugh

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Technical Editor, Sound On Sound

Got one of those mains voltage/current jobbies myself. Quite useful.

Don't underestimate the effect of supply changes on valve kit. As far as I've seen only fairly recent top quality kit has done serious control, and if the mains voltage rises you get a multiplying effect as higher anode/screen voltage gives more gain, but changes the working point of the valves, and at the same time higher heater voltage increases the emission, so again changes the working point.

UK supply voltage used to be quoted as 240V +6% - 10%, but now is European 'harmonised' 230V +- 10% which effectively means the supply companies can get away with lower voltages

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It wasn't me!
(Well, actually, it probably was)

Quote chris...:

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Something like this:

http://www.maplin.co.uk/plug-in-mains-power-and-energy-monitor-38343

should do - tho' not sure how accurate.

Whether this is your problem is another matter!

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That should be as accurate as you can be with mains volts Chris. I don't know whether you have ever monitored the mains but it is never still! I had to set it to 230V for spec' tests with a Variac and everytime I glanced at the meter it was 231 or 229!

Dave.

Quote ef37a:

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That should be as accurate as you can be with mains volts Chris.

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I'm glad to hear it.

Quote:

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I had to set it to 230V for spec' tests with a Variac and everytime I glanced at the meter it was 231 or 229!

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Right, but of course that in itself doesn't tell us much about the meter's accuracy...

Quote chris...:

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Right, but of course that in itself doesn't tell us much about the meter's accuracy...

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No, it doesn't... but if you go to that Maplin Link and then click on SPECIFICATIONS you'll see the rms AC voltage accuracy is quoted as typically 0.002V and maximum 0.01V.

Hugh

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Technical Editor, Sound On Sound

Good Lord! Whatever for? Switch on your washing machine and the figures will be flapping about all over the place.

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It wasn't me!
(Well, actually, it probably was)

Quote Folderol:

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Good Lord! Whatever for? Switch on your washing machine and the figures will be flapping about all over the place.

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Verily! And that is why if I paid £2k+ for a compressor I would expect it to have fully regulated supplies, all of 'em!

I don't know about the RNC but the RNP has quite sophisticated power management I understand? And that at 1/4 the price.

Dave.

You seem to be assuming that the thermionic culture products don't have regulated supplies... Is there anything to substantiate that?

Hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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You seem to be assuming that the thermionic culture products don't have regulated supplies... Is there anything to substantiate that?

Hugh

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Well that's where we came in wasn't it Hugh? The compliant that the devices have an inconsistant performance day to day. Valves, especially small signal valves are pretty stable devices (assuming TC don't use bottom draw Russkies!)so the most likely explaination for the wandering parameters IS supply variation, just keeping the heater supply stable is probably 75% of the battle. In fact my experience is that put ECC83s on a 7812 regulator and the damn things last for ever!

Didn't anyone notice when they popped the cans for the photos?

Dave.

I am so slow these days!
There is no longer any need for makers of valved devices such as preamps, EQ etc to get into conventional HT supplies!

I have in front of me a pcb, 150x110mm containing a pos and neg 15volt supply, part of which feeds a heater and a UC3843AN chip driving a FET that produces 304volts at about 2mA but that can be made to supply 400V* and beefed up for more current. The whole circuit is powered from a 24V DC supply which could be a conventional 50Hz job or, as in this case, an external 24V SMPSU.

The pcb is part of two others in a pedal that sells for less than £200 for the top product (psu pcb is common to the range). So there really is no excuse for unregulated heater and HT supplies in anything but the cheapest Bellringer crap!

*I have one modded for 48V spook juice.

Dave.

Here's a little Bustard... There might be more gut shots of TC gear knocking around.

Quote Korff:

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Here's a little Bustard... There might be more gut shots of TC gear knocking around.

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I can't get a big enough image with good enough resolution to tell much. There does seem to be two bridge rectifiers so the heaters could well be DC but regulated?

Oh FCS! the image has now got better as I review the post! No, not a bridge and there are some (limply!)twisted wires that could be heaters and that suggests bog standard AC.

Dave.

http://media.soundonsound.com/sos/nov10/images/thermionic_littlebustard_02 .jpg

Same picture, but bigger resolution. Click on it to zoom in if you are on a smaller monitor.

http://media.soundonsound.com/sos/jan10/images/thermionic_fatbustard_02.jp g

Another one.

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http://soundcloud.com/richie-royale
http://www.mixcrate.com/richieroyale

The choice of knobs on these devices is awful for what is a very expensive compressor. (Sure I know, listen don't look but...£3K +) I have been seriously considering another high end valve compressor (something more coloured than my Summit DCL-200)and I am not impressed by the visual aspect of these devices from the outside. I was thinking "They must have spent the money on the inside". This has been an interesting read.

SafeandSound Mastering

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Mastering online mastering

Thanks,
Still hard to tell if it has DC heaters but I can see no evidence of any regulation,HT or heaters.

I suppose the construction is well...Ok. "Fender circa 1970"? I would expect these day to see all the power supply components sans transformer on a decent pcb.

Dave.

Thanks for the detailed pix. That power supply is a house of horrors!

The heaters are in fact DC. There are 4 diodes in a bridge configuration (you can see them quite clearly if you zoom in). However, they are actually 8 diodes wired in parallel pairs - something you should never do under any circumstances!

Above the ceramic resistor is one of those little circular 1 amp bridges bodged onto the tagstrip. This is obviously for the HT

As Dave said, there is absolutely no attempt a voltage regulation - not even crude mains tappings. And why have the put screening round the mains Tx, which is well away from everything else, but none round the power switch right beside signal switches.

I notice the transformer hasn't been very well fitted - it's sitting to one side of the dished washer.

Apart from what looks like a fuse carrier between the power switch and the transformer there appears to be no protection, and no spike/EMI suppression.

Main PCB looks like cheap paxolin rather than a GRP one - a decision that can only be described as 'quaint'.

All in all, nothing like what I'd expect for 2k - especially including those bargain basement pot knobs.

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It wasn't me!
(Well, actually, it probably was)

Thanks again chaps - all useful stuff. My friend will get to Maplins for one of these gizmos asap, I'll update the post once we get some results. Had a look for some gut shots of the Phoenix online, but nothing doing, so I'll try to get some if anyone is interested - won't be able to do it till next week though.

Cheers

Quote ef37a:

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I suppose the construction is well...Ok. "Fender circa 1970"? I would expect these day to see all the power supply components sans transformer on a decent pcb.

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Hand made point to point wiring is a big selling point for these things. It may have kept the radio/TV repair trade in business during the 50's and 60's but I'm not sure I want that type of construction in a working studio - unless it is done really well.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

For info, I have invited Thermionic Culture and/or their agents to comment and am awaiting a response.

hugh

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Technical Editor, Sound On Sound

Quote James Perrett:

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Quote ef37a:

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I suppose the construction is well...Ok. "Fender circa 1970"? I would expect these day to see all the power supply components sans transformer on a decent pcb.

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Hand made point to point wiring is a big selling point for these things. It may have kept the radio/TV repair trade in business during the 50's and 60's but I'm not sure I want that type of construction in a working studio - unless it is done really well.

James.

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Yes James, peeps love to see "hand wired" in guitar amps too and some think it adds to the sound quality.
In truth the things are FAR more consistant when build on pcb's. I personally think you get a better product at a cheaper price and/or you can put in more features apt to the modern player such as FX loops and MIDI.

Dave.

Quote ef37a:

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peeps love to see "hand wired" in guitar amps... In truth the things are FAR more consistant when build on pcb's.

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I'd like it if my Twin had been hand-wired, as the PCB traces which raised off the PCB wouldn't have required tracking down and repairing There are pros and cons to both approaches.

Badly chosen PCB materials- they forgot about the heat inside the amp. It doesn't follow that all PCBs are "bad".

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madtheory creations
Synths and pianos for Kontakt

Just clocked the gutshot of the Ingram pre' page 176 March issue.

Now THAT'S the way to make a power supply in the 21st century TC!

BTW, early days but the March issue looks virtually as well stuffed as Febs!

Dave.

Yep, there's no doubting that you get what you pay for in the Ingram. Beautifully designed. Shame about the silly production wiring cockup and incomplete QC, but easily resolved and I'm confident that the company has addressed that particular weakness.

Also glad that you're finding so much to enjoy in each issue, Dave

hugh

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Technical Editor, Sound On Sound

Quote SafeandSound Mastering:

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The choice of knobs on these devices is awful for what is a very expensive compressor. (Sure I know, listen don't look but...£3K +) I have been seriously considering another high end valve compressor (something more coloured than my Summit DCL-200)and I am not impressed by the visual aspect of these devices from the outside. I was thinking "They must have spent the money on the inside". This has been an interesting read.

SafeandSound Mastering

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I am also looking for a vari -mu type compressor, and considered thermionic, but it's a bit out of my range (money) and this thread is a bit eye opening too....
here :
http://www.igsaudio.pl/index.php?option=com_content&task=view&id=5
is a guy in Poland who builds many professional audio tools, and also prices are on the 'indie' side:)
many studios in Poland (and not only - check GS -there are happy folks in US too) use his gears and they love it,
I myself got ssl4k 'wannabe':) and it's wicked buss comp
I am considering to get one (vari mu), (I am not reseller or sth.) just dropped that link so you can check it yourself,
good luck!

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online mastering studio | mastering audio

Hi all - just got the first voltage readings from my friend - seems to vary between 241 and 245 so far, well within spec I would have thought!

Cheers

For a mains supply, yes, that's well within the spec, although obviously a little on the high side of the nominal 230V. Probably because he's either close to the local substation transformer or the thing has been left on a higher tap for some reason.

The variation is only 1.6% though, which isn't a lot. Has he been able to correlate 'good' and 'bad' sound with those 'high' and 'low' mains input voltages?

Hugh

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Technical Editor, Sound On Sound

I think his issue is not that it sounds bad, but that it sounds different at different times! He has been somewhat reassured by other people's experience that these things are inherently inconsistent and that it's not just him losing the plot....

Quote Hugh Robjohns:

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For info, I have invited Thermionic Culture and/or their agents to comment and am awaiting a response.

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Did they get back to you Hugh?


Martin

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YewTreeMagic

Disappointingly, no! I had an acknowledgement of my invitation for them to join in, but nothing since.

Hugh

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Technical Editor, Sound On Sound

They probably read the thread and got cold feet!

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http://soundcloud.com/richie-royale
http://www.mixcrate.com/richieroyale

Quote Red Mastering:

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http://www.igsaudio.pl/index.php?option=com_content&task=view&id=5
is a guy in Poland who builds many professional audio tools, and also prices are on the 'indie' side:)
many studios in Poland (and not only - check GS -there are happy folks in US too) use his gears and they love it,

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Review of the his Tubecore Mastering Edition will hit the shelves with the next issue of SOS. Lovely sounding piece of kit. Missing a few functions when compared with Manley and Thermionic mastering offerings, but it sounds great. Price will be going up a bit as they now have a distributor margin to account for, but it still looks rather competitive.

Not tried this one yet, but it's another possible candidate from a manufacturer with positive feedback in the usual on-line places: Hand Crafted Labs

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SOS Reviews Editor

Oooer!
I would hate to have to service that Varis device!

"Hand wired" if done with turret board and wireman lacing is nice to see (but still a bit of a PITA to fix and look leaving pristine) but I really do think the whole shebang should be confined now to the "breadboard era" dustbin and folks use ~1.3mm FR4 and heavy copper, plated thru' PCB? Vastley better unit to unit consistancy.

And those meters are a bit "Maplin"?

Dave.

Greetings everybody.

Thermionic Culture are now going to be monitoring user forums to provide any help we can with our products.

This thread alone has a lot of questions, I am going to read back through to answer as many as I can. But please feel free to ask me anything and I will do my best to respond.

Many thanks

Charlie - Engineer at Thermionic Culture

...right now, where do I begin...

Welcome Charlie -- and thanks for getting involved. I'm sure our forum members will appreciate your input.

hugh

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Technical Editor, Sound On Sound

Quote ef37a:

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Well, I know nothing of the equipment save what I have read in SoS but perhaps someone should send the makers a copy of Nelson Jones' Valve Amplifiers!

Making stabilized heater, bias and HT supplies using modern ICs is pretty simple and would add little to the cost of the units.
Bugger! Were I 30 years younger! I can see an nice little earner there! Will, want a lucrative sideline modding vulture giblets?

I know people want the "sound" of valves but surely the challenge is to keep the sound but use modern techniques to overcome their many shortcomimgs and extend their life?

Dave.

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Hi Dave,

We are always developing our products to make them perform better, and yes we certainly do use solid state technology to improve performance. Of course we have our own ethos to valve electronics and design requirements, without them we wouldn't make such great sounding products.

I go to bed with Morgan Jones' Valve Amplifiers every night...

Thanks for your comments.

Regards

Charlie

Quote Hugh Robjohns:

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Disappointingly, no! I had an acknowledgement of my invitation for them to join in, but nothing since.

Hugh

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We have recently changed the way we run the business and have only just heard of the invitation. So we jumped at the chance to talk to our end users.

Very happy to be here, thanks for the invite.

Charlie

Quote Hugh Robjohns:

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You seem to be assuming that the thermionic culture products don't have regulated supplies... Is there anything to substantiate that?

Hugh

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We do use voltage regulation in our products. However, our company is here because of the brilliant designs of Vic Keary who has been designing strickly valve circuitry his whole life. The original designs never used solid state to regulate supplies and this was never a problem - noise at -105dB bellow MOL is better than most studio gear on the market. As time went on our designs changed and we use solid state to regulate heater and HT supplies, I assure you it was quite a challenge to convince Vic to go this way

The Thermionic Culture sound is down to very well designed circuitry, I assure you we take everything into concideration.

Charlie

Quote Folderol:

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Thanks for the detailed pix. That power supply is a house of horrors!

The heaters are in fact DC. There are 4 diodes in a bridge configuration (you can see them quite clearly if you zoom in). However, they are actually 8 diodes wired in parallel pairs - something you should never do under any circumstances!

Above the ceramic resistor is one of those little circular 1 amp bridges bodged onto the tagstrip. This is obviously for the HT

As Dave said, there is absolutely no attempt a voltage regulation - not even crude mains tappings. And why have the put screening round the mains Tx, which is well away from everything else, but none round the power switch right beside signal switches.

I notice the transformer hasn't been very well fitted - it's sitting to one side of the dished washer.

Apart from what looks like a fuse carrier between the power switch and the transformer there appears to be no protection, and no spike/EMI suppression.

Main PCB looks like cheap paxolin rather than a GRP one - a decision that can only be described as 'quaint'.

All in all, nothing like what I'd expect for 2k - especially including those bargain basement pot knobs.

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I appreciate that you can not reverse engineer something just from a picture, but I hope that therefore you appreciate that you are not seeing everything in the unit.

Without going into details about the design of the LB in particular, both HT and heaters are DC, the parralled diodes you mention are zeners, and the transformer case is protecting the small signal stage from the transformer.

We are very happy with noise levels in this unit, and it wouldn't be in production if mains to the power switch affected performance.

Hope that helps.

Regards

Charlie

Hello Charlie and welcome.

My apologies for assuming that the compressor used unregulated supplies.

However, the original post was concerning the variabilty of performance that seems to be inherent in these products. I had already said that it was most unlikely that your company would use inferior valves which drifted in their characteristics from day to day and so, in the absence of any other information I theorised that mains supply and hence internal supply shift was the cause of the perfomance changes.

So, if all the rails are rock hard, what else might be the cause of the observed performance drifts?

Dave.

Hmmm.
I'm very curious about that quoted noise level. What weighing are you using? Compressors, by their very nature significantly worsen S/N, and unless there is noise gating (which you haven't mentioned) I would think that was a hard figure for solid-state compressors to achieve, let alone valves.

It is a shame you don't feel able to go into more detail about the PSU. I've been working on electronic equipment (both valve and solid state) for about 45 years and I'm always keen to see different approaches to resolving problems. Some I like, some I don't, but the only ones I view with caution are the 'black box' ones.

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It wasn't me!
(Well, actually, it probably was)

I think Charlie is entitled to restrict how much detail he gives out for obvious commercial reasons. A noise floor 105dB below the maximum output level is very good for a valve product, but quite believable and easily achievable in solid state gear. Assuming a MOL of +24dBu, the noise floor would only need to sit at -81dBu...

Hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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I think Charlie is entitled to restrict how much detail he gives out for obvious commercial reasons. A noise floor 105dB below the maximum output level is very good for a valve product, but quite believable and easily achievable in solid state gear. Assuming a MOL of +24dBu, the noise floor would only need to sit at -81dBu...

Hugh

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According to the SoS review the MOL is only +20dBu and I am with Will, 105dB below +20dB is outstandingly good for valve kit even if the valves are very carefully selected.

Dave.

Max output level of the the Phoenix is the volume at 1% THD, which is usually +24dB depending on the valve. We won't accept anything under 23dB. On paper we spec the phoenix SNR to -100dB bellow MOL, but the majority perform to better than -105dB under test.

I hope that helps.

Charlie

The only reveiw I can find here is this one from 2000.

http://www.soundonsound.com/sos/apr00/articles/phoenix.htm

Was this the one you were referring to Dave? If so you would also notice that the SNR was measured at -85dB bellow MOL and THD with no compression at 0.1%

Figures are now -100dB SNR and 0.06% THD, but under test the majority are better than this.

Regards

Charlie

Hi Charlie. Thanks for taking the time to respond in this thread. We also reviewed the Phoenix MC in SOS March 08 . You can find other Thermionic Culture reviews here.

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SOS Reviews Editor

Morning Charlie.
This,
http://www.soundonsound.com/sos/apr00/articles/phoenix.htm was the review I was refering to and mentions a MOL of +20dBu but no THD figure is given.

I have found noise specs for two well known solid state compressors.
The Neve 5043 at zero compression quotes "better than -92dBu"
The RNP 1773 no condition specified. "better than -90dBu"

And for the valve based Teletronix LA-2A the rather quaint and confusing specification of -70dBm below +-10dBm.

Dave.

Good morning!

Looks like we are looking at the same article?

In the 2008 article Hugh says "and the noise floor is reasonably low, although this unit does benefit from being driven fairly hard to maximise the signal-to-noise ratio" So no mention of figures but this would suggest that they have seen better? In this article it also reads MOL +24dB into 10K load, it will be about +19dB into 600ohm load.

SOS do the most extensive tests so I am sure they would pick up on a misleading specification.

As for the noise figures of other products, it seems like everyone states their figures in different ways so I would be careful of that. It is hard to comment without knowing all the facts. But, maybe they are happy with their noise figures....?

I have a friend that builds custom valve pres and constantly boasts SNR figures of -125dB. So with good techniques it is easily possible

Regards

Charlie

Yes, I would agree Charlie, noise specs are a mess!

The friend is certainly boasting if that claim is for a noise OUTPUT of -125dBu! A 600 Ohm resistor is worse than that at -124.4dBu (ref D Self Small Signal Audio Design).

But I shall leave the debate and conclusions to those far better qualified than I.

Dave.

Quite right Dave, I would always take anyone's claims with a pinch of salt. This is why we try to be as transparent as we can.

In the interest of science I will do some tests with a Phoenix today using a variac to simulate ac mains variation. Will report back.

Best regards

Charlie

Charlie m8,

The Phoenix was one of my 'go to' units when I wanted some really smooth yet big processing.

I think if you guys built a version with some harmonic control and then gave it to me, I guess I would be really happy.
Just think: you would make an ethnic happy, not just for Xmas, but for a substantial length of time until valve gear shot up in price then I would sell it and come back to you with another gem of a suggestion.

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Samplecraze
Stretch That Note

Quote Zukan:

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Charlie m8,

The Phoenix was one of my 'go to' units when I wanted some really smooth yet big processing.

I think if you guys built a version with some harmonic control and then gave it to me, I guess I would be really happy.
Just think: you would make an ethnic happy, not just for Xmas, but for a substantial length of time until valve gear shot up in price then I would sell it and come back to you with another gem of a suggestion.

---

Sounds like you need a Vulture Zukan

Ah yes, forgot about the Vulture....

Do you want me to PM my address? You know, for beta testing n' all that?



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Samplecraze
Stretch That Note

Good day all,

Very sorry this has taken so long to respond to but things have been rather busy this end, and alas I forgot to post results of the mains variation test for you.

With a Phoenix M+ I had available I measured the output level in dBu over a range of mains voltages. I believe the UK mains supply can vary 10% so I checked from 220V to 240V, and the output did not vary more than 0.02dB. This small voltage will be down to the type of regulation in the power supply, but hopefully you will agree that this is not a large enough amount to hear.

As for the OP's Phoneix sounding differently at different times of the day, that may need some further investigation. It may be that the power supply is not working properly, but I couldn't comment until taking a look.

Hope that helps

Charlie

Thanks for coming back on this. That is an interesting result (and much lower that I would have expected).

Is that for a signal actually being compressed (and if so, by how much), or is it the open-loop gain?

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It wasn't me!
(Well, actually, it probably was)

Quote Charlie TC:

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I believe the UK mains supply can vary 10% so I checked from 220V to 240V, and the output did not vary more than 0.02dB.

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That would be a 5% variation, not 10%!

The actual UK tolerance range is currently 216 to 253 V AC, which is a -6 /+10% tolerance, although some EU countries specify a -10% lower limit, which is 207V!

H

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Quote Charlie TC:

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I believe the UK mains supply can vary 10% so I checked from 220V to 240V, and the output did not vary more than 0.02dB.

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That would be a 5% variation, not 10%!

The actual UK tolerance range is currently 216 to 253 V AC, which is a -6 /+10% tolerance, although some EU countries specify a -10% lower limit, which is 207V!

H

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Goodness! I beg your pardon Hugh, don't know what planet I was on there!

It was results straight from my note book, but now I have a little time I am happy to run a few more tests to get some fresh results.

I have monitored our mains over a long period of time and I have never seen it range that much, although it is a filthy signal! Let's try it out, i'll run some tests this morning at different compression settings at different mains voltages.

Folderol - I believe I measured that at no compression, will get back to you with new results.

Cheers

Charlie

OK so Ive got a Phoenix on the bench;

At no compresiion - As stated before there is marginal difference between 220V-240V, beyond that there is more of a change. From 240V-250V there is a 0.2dB difference, and from 210V-220V there is a 0.2dB difference. So if your mains supply was to vary from 210V-250V you could expect a 0.4dB difference.

Tested again at -10dB compression - again very marginal difference in level in from 220V-240V <0.1dB. Pushing to the extremes there is a 0.3dB diffence at 250V and 0.2dB difference at 210V.

If you are unlucky enough that your mains goes up to 270V you will see a 0.4dB rise compared to 235V.

One point to bear in mind is that the harmonic content did not change at all throughout these tests, so I can not imagine any tonal change in the Phoenix at different times of the day, even if your mains was behaving very badly.

I hope that helps, and again to the OP - if you are having trouble with your unit please get in touch with us and we will take a look at it for you.

Cheers

Charlie

very interesting observation, but still even in extreme situation .4dB won't change the music too much:)
I think .5dB-.4dB is the lowest value I can hear when doing a/b
anyway, I am sure I won't be able to recognize .4dB difference listening to track next day!
that's sure so kudos to the engineer's ear who spotted it
anyway, very valuable information,
thanks for this test

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online mastering studio | mastering audio

Wow, you folks really took it to this guy from TC... He should get a free t shirt or something.

...or some new customers?


Martin

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YewTreeMagic

Well I hope that you found the results useful in some way, and that it might help you understand the unit a bit better.

We are happy to help and answer your questions.

Charlie