We used to call that "Open field measurement" - because we did it in a big farm field rather than a parking lot. Works quite well!
Personally, I think it's lunacy to have an audio system without tone controls.
Fortunately, perfectly functional decades-old stereo receivers can be found very cheap in thrift stores. They have tone controls, and distortion levels below audibility. Perfect!
-Gnobuddy
Personally, I think it's lunacy to have an audio system without tone controls.
Fortunately, perfectly functional decades-old stereo receivers can be found very cheap in thrift stores. They have tone controls, and distortion levels below audibility. Perfect!
-Gnobuddy
There are many op-amp tone control boards which will match the chip/d-amp boards being discussed on this forum. Example-http://www.aliexpress.com/item/J34-Free-Shipping-1pc-NE5532-Volume-Tone-Control-Board-10-Times-Pre-amp-DIY-Kit-New/32581692294.html?spm=2114.30010308.3.2.Xzk1dO&ws_ab_test=searchweb201556_8,searchweb201602_5_10017_507_401,searchweb201603_2&btsid=c66da2c5-bd9b-43b0-a975-c099df775d6f
Now, if tone controls became the norm, would there will be a lot of redundant chip comparers and far fewer posts?
I happen to play electric guitar, and there is similar madness in that world as well.
For example, musicians will pay hundreds of dollars each for rare, hard to find, different vintage versions of a distortion pedal known as the "Big Muff". But if you put a $50 7-band graphic equalizer pedal in the chain, you can make any of these sound virtually identical to any other - because the only audibly significant difference between the various versions is one single altered RC time constant in the internal tone control circuit!
-Gnobuddy
The tone controls typical of the 1950's have plenty to offer. Quad continued with them into the 1980's. I recently needed EQ for a project. Having a Quad 33 control unit I thought it would do as a quick try out. I was very impressed. So much so I worked out how to get the 33 to give it's best. A window of +/- 3 dB to my ears. The 12 V rail is the main reason.
The Quad uses an inductor and a very simple circuit. All the same it has low distortion compared with the real needs. The 33 lives in the unhappy world where if it were valves/tubes it would be heroic. As it is transistor it is like something picked up on one's shoes if a debating group. Both groups seem to chase ideals far removed from reality. I don't mind if it sounds no worse and costs no more. There is a case for technically better for it's own sake. Sometimes that can sound sterile whilst equally good examples sound fine. Ears must always be the ultimate judge.
As I said before some truth in this game we call audio would be the next breakthrough. Sometimes when people critise things what they really mean is they haven't a clue how to make it work well. Then a little club forms to echo that idea. I see it time and time again. It makes for bargains which is no bad thing. Not sure DIY Audio deserves to be included in that group of non believers? Hope not.
Am I alone in thinking the internet has died as far as technical questions are concerned? Google is useless. Any thoughts? For me the ultimate hi fi upgrade would be the internet of 2003. Even my daftest questions could be answered. Yesterday I asked for standard ECC82 circuits to replace an ECC83 and remove feedback. I was surprised how few examples I saw. I suspect I will set it up on a constant current source and play with cathode resistors. It would be from a 200 V rail in an amp called Separo SE88i. Taking out the ECC83 is a better option as I have enough to drive it into the ECC82 SRPP stage. Was just thinking it through. The SRPP has a gain of about 7 as no cathode cap. This drives a KT88. I suspect 4 Vrms required. A further ECC82 should be CD level of input at about 500 mV.
The Quad uses an inductor and a very simple circuit. All the same it has low distortion compared with the real needs. The 33 lives in the unhappy world where if it were valves/tubes it would be heroic. As it is transistor it is like something picked up on one's shoes if a debating group. Both groups seem to chase ideals far removed from reality. I don't mind if it sounds no worse and costs no more. There is a case for technically better for it's own sake. Sometimes that can sound sterile whilst equally good examples sound fine. Ears must always be the ultimate judge.
As I said before some truth in this game we call audio would be the next breakthrough. Sometimes when people critise things what they really mean is they haven't a clue how to make it work well. Then a little club forms to echo that idea. I see it time and time again. It makes for bargains which is no bad thing. Not sure DIY Audio deserves to be included in that group of non believers? Hope not.
Am I alone in thinking the internet has died as far as technical questions are concerned? Google is useless. Any thoughts? For me the ultimate hi fi upgrade would be the internet of 2003. Even my daftest questions could be answered. Yesterday I asked for standard ECC82 circuits to replace an ECC83 and remove feedback. I was surprised how few examples I saw. I suspect I will set it up on a constant current source and play with cathode resistors. It would be from a 200 V rail in an amp called Separo SE88i. Taking out the ECC83 is a better option as I have enough to drive it into the ECC82 SRPP stage. Was just thinking it through. The SRPP has a gain of about 7 as no cathode cap. This drives a KT88. I suspect 4 Vrms required. A further ECC82 should be CD level of input at about 500 mV.
The definition of what would be regarded as truth in audio needs to be defined.... To some truth is based on super hearing and an arrogance that they can hear so don't need to measure, do blind tests or any other way of supporting their hearing... to many of these types mains cables sound different and the unclean deaf members with crappy systems who dare base their views and arguments on such boring things as physics are wrong to disagree with them... Hell I don't know why some of the GEB don't work for CERN as quark spotters as their senses are far superior than anything else....
Maybe getting back to the basics of analogue and digital engineering would help on the electronics side, after all all we are doing is transporting either a digital or analogue signal from A to B and adding some gain (oh and of course DAC for a digital signal).
Truth is doing what took me years to do. Finding out what is liked and why of designs that don't instantly suit my way of thinking. An open mind more correctly than the truth. Other peoples truth I guess.
I have a friend who worked at CERN. If he is typical he likes minimalist ideas. He told me they still use big triodes made just for them.
I have a friend who worked at CERN. If he is typical he likes minimalist ideas. He told me they still use big triodes made just for them.
Or all gone to social networking. Many fun eccentric personal websites are gone or stale by sometimes 10 or more years. To much work for no return.
I've seen a Truly Advanced Device on a guitar amplifier: It was a switch next to the tone controls that had positions labeled "Fender" and "Marshall."
The guitar amp circuits back then were nowhere near the standard Bandaxall that hifi systems had already adopted by the 1950s. The labels Bass, Mid and Treble are merely vague suggestions as to what range of the audio band the potentiometer actually controlls (turning up one band often decreased the volume of another), but their weird characteristics ended up being a large part of what distinguished one brand from another.
The UK amp manufacturer Blackstar has done one better: they have a patented knob that supposedly varies the tone control characteristics from Fenderish at one end to Marshallish at the other. They call it ISF, for "Infinite Shape Factor".
Agree with you 100%.
Those vintage tone control circuits are a laughable joke, though a great deal of good music has been made with them, nevertheless. Musicians can be a persistent lot, and if you tinker with those knobs for long enough, you might accidentally find a combination of settings that gives you a good guitar tone. The funny thing, though, is that it's not terribly easy to do better. For Hi-Fi, active (rather than passive) tone control circuits using frequency-varying negative feedback were a huge improvement. But active tone controls are very tricky to use in a guitar amp for a couple of reasons.
One reason is that circuits with substantial amounts of negative feedback (which is necessary in, for example, an active Baxandall tone control) do not clip gracefully. Another reason is that if such a circuit clips, open-loop gain is zero, therefore there is no feedback, therefore there is no tone control!
In Hi-Fi use, the solution is simple: keep the signal level well below clipping at all times. In a guitar amp, this is not so easy or desirable - overdrive is part of the electric guitar sound. So overdrive is inevitable - sooner or later, the guitarist using the amp will turn up the gain or insert an overdrive pedal in the signal chain.
Given inevitable overdrive, the only way I've found to keep the active tone control from clipping is to insert a drastic amount of attenuation in front of the (active) tone control.
For example, if the preceding valve stage can put out a maximum of 120 volts peak to peak when overdriven, and the subsequent active tone control can do the same, but has a +20dB bass or treble boost capability, then you have to restrict the input signal to the tone control to a maximum of 12 volts peak to peak to keep it out of clipping.
The only way to manage this is to insert a fixed 20 dB (or greater) attenuator between the two stages, so that even if the preceding stage is overdriven (to 120 Vpp) , and the tone control set to maximum bass or treble boost (gain of x10), it still cannot clip.
That works, but now you just threw away 20 dB of hard-earned voltage gain. Let's say you got a typical gain of x 50 (34 dB) out of your preceding 12AX7 gain stage, now you threw away 20 dB, so all you have left is a measly 14 dB (that's only a gain of 5!)
Heck, with that much gain loss, you might as well have just used a passive tone control circuit with a 20 dB insertion loss in the first place!
The other approach is to find a passive tone control circuit that is better behaved - less interaction between controls, a "bass" knob that actually affects only the bass (!), and so on. I had high hopes for the passive Baxandal or passive James circuits, but LTSpice simulations show that they both seem to have rather ugly tone control contours, quite unlike their well-behaved active versions.
In my spare time, I've been looking for a better passive tone control circuit for a guitar amp for the last year or two, and while I can now do much better than Fender's three-knob absurdity, I'm still not entirely happy with what I have. The Holy Grail still remains unfound...
-Gnobuddy
The next big thing in audio technology is already here. Sadly only NASA has it so far.
Vacuum transistors.
https://www.nasa.gov/ames-partnersh...nanostructure-based-vacuum-channel-transistor
It's going to be sweet once they become available.
Vacuum transistors.
https://www.nasa.gov/ames-partnersh...nanostructure-based-vacuum-channel-transistor
It's going to be sweet once they become available.
The "next big thing" will be posting single tracks of multitrack recordings on Youtube.
Oh, wait...
https://www.youtube.com/watch?v=y5rUKbI3Y-M
Oh, wait...
https://www.youtube.com/watch?v=y5rUKbI3Y-M
The "next big thing" will be recording hit songs at home.
https://www.youtube.com/watch?v=N2C1RktyFEQ
https://en.wikipedia.org/wiki/Come_Softly_to_Me
https://www.youtube.com/watch?v=N2C1RktyFEQ
One tone control most ignore is the 75 uS of the RIAA. This often is passive to aid design. This offers very simple adustment with no real down side. EQ's between 25 and 100 uS could be useful. A flat EQ if some 78's. OK it will be far from perfect. It should be a nice free lunch all the same. I like active for 3180/318, of late I have fitted an additional 2 uS passive filter to the output. The preamp being passive + active. Some recordings that sound very weird tonally sound fine when totally EQ'ed ( all three or whatever ). Some even seem to loose the antique sound they usually have. Whilst just doing the 75 uS won't do that, it hints at better.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.