tube Pre amps ? |
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Sinai Sound
Young Croc Joined: 09 November 2009 Location: Sheffield Status: Offline Points: 631 |
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Shame these aren't made anymore
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3864 |
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Don't forget about transformers - they can also introduce distortion, especially if overdriven with low frequencies. In old valve gear, there are likely to be both input and output transformers to match the high impedance of the valve stages with low impedance sources and destinations. Some circuits even have transformers between stages. One valve in a low-voltage circuit hasn't got a hope of replicating that compex harmonic signature. Even a high-voltage multi-valve circuit may not do "it", if the transformers aren't right.
I recall reading an article about Pultec EQ units in SOS years ago, where the studio engineer had found that merely patching in the EQ had a beneficial effect on the sound. It was thought to be down to the transformers in the unit, which remained in circuit even while the EQ was in "bypass" mode. Subjective probably, but shows how much effect the magnetic components can have.
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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Avalon, TL Audio, and the DBX 162 are all still in use on tours around the world, as bus compressors. They’re not insanely expensive.
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5176 |
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There are hundreds of old used units available today. The new units being pushed today are not designed to distort without some means of manual control(s) to enhance the distortion level. The old units would introduce distortion in which, you had no control to alter except by lowering the input level.
The older soundman that grew up solely on Analogue gear will be able to achieve a minuet to aggressive behaviour pattern with just inserting a piece of old hardware within the chain. The younger soundman who grew up using only digital gear assume you must have distortion, saturation, what have you, controls in order to create what they consider "warmth."
Since the younger generation never experienced on hand what an old piece of hardware sounds like in their sound system, they are the ones chasing something they are imagining in their minds that they can tune their liking which, does not exists.
I might add, the majority prefer the distorted sound emitting from semiconductors more than that the distorted sound from valves due to the reaction time semiconductors offer versus valves when focusing on fast tempo music.
I made a comparison a few years ago with three compressors on bass in which, will give you an idea on what to expect using a semiconductor compressor versus a valve compressor to add distortion in the mix. Best Regards,
Edited by Elliot Thompson - 26 September 2019 at 5:44pm |
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Elliot Thompson
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Sypa
Young Croc Joined: 21 February 2013 Location: Croatia Status: Offline Points: 921 |
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Didn't even know that existed and looking around can't find anyone selling it either. Love the xone filter on the 92. How did the tube thing sound?
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
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The VF1 is an interesting bit of kit because the valves in it really do nothing to the signal. They are in circuit wired as cathode followers which means they buffer the signal and add negligible distortion to it. However they are preceded by a classic back to back diode feedback op-amp circuit which is where the overdrive comes from. So everyone who has ever gushed about how valvey and analog a VF1 sounds, haha. Nope, all solid state and quite basic solid state overdrive circuit at that. Very popular with guitar overdrive guitar pedals. You can find the service manual online and follow the circuit yourself to check.
I build a bit of a kit years back for a friend meant to have a bit of VF1 similarity, but I couldn't also resist throwing the kitchen sink in with regard to state variable filters triggered from a selection of intermixable sources. This unit used "proper" valve distortion in that the tubes were wired for gain and actually clipped/rounded the signal themselves before it was reduced and re-mixed back to the source. Device itself worked ok, needed more refinement but parts of it had potential. I was most happy with the automatic gain control circuit that took the bass output of the valve overdrive and mixed it back with the original signal. Unique circuit in its way as far as I know. Anyway kids etc arrived and time disappeared after the first prototype which as far as I know is still kicking. If the faceplate looks a little scrappy its because I did it all using my cnc mill and it was a learning process (still is tbh). Anyway the moral of the story is, don't get all excited just because something says it has a valve in it... |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5176 |
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Good old Diodes The dbx 166 offers a diode circuitry in their variable Peak Stop contour. My CBS Volumax in addition to Gates Solid Statesman offers a diode as well to limit the output signal.
There are a few Youtube Videos in which, certain name brands actually used an LED behind the Tube to give you the impression it is actually working. Unfortunately, many manufactures use valves for decoration and do not offer sufficient voltage for the valve to perform properly which is why, some use such methods.
Unless you are 40+ years of age, the chances of you understanding the tonal characteristics of Valves in your sound system is very minimum. Solid State distortion is more common to the average sound man in these times and, is routinely mistaken for Valve distortion.
Best Regards, |
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Elliot Thompson
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
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Indeed, there are a lot of starved plate low voltage designs out there. They do work, I experimented with them before deciding on ~100V HT for the unit shown above but you are in such an odd region of the device's transfer characteristics that what you get out is chance more then anything else. Having played around with valves for guitar and other units plus plenty of op-amps etc I can confidently say that you can get good or bad sounding distortion out of just about any device depending on your circuit. But thinking something with a valve in it is going to inherently sound good is a very modern mistake to make.
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Sypa
Young Croc Joined: 21 February 2013 Location: Croatia Status: Offline Points: 921 |
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Woah I bet if you built those things and packaged them in a nice hip industrial design it would sell like hotcakes,offcourse the sound of it should play a major role. Out of wonder on a small batch how much did it cost you to build it ? |
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
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No idea! Probably not much change out of £500 once you added all the parts up and that's not counting time and tools. But sometimes you just do these things for the fun and learning experience. I certainly learned a lot, so maybe one day I will drag the design files out of the vault and make a mark 2 with refinements. It was also the first thing I made where I exported PCB designs into 3D CAD software and added the components, this let me design an enclosure and faceplate that fitted perfectly around the boards. Those skills have turned out to be very useful since, never stop learning I say.
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valve head777
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1781 |
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The ultimate solution is...... Get young arms etc to lift your lovely precious heavy Crown Macro Tec 5000 and enjoy the lovely warm sound so desperately missed in lightweight Tec. |
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Freedom of choice, choice of freedom.
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Norseman
Registered User Joined: 04 March 2013 Location: Torquay Status: Offline Points: 124 |
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i have similar thought patterns...
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