Kev
Well-known member
Hi Ed,
welcome to the LAB.
:thumb:
welcome to the LAB.
:thumb:
THD hotplate
- Thread starter tony dB
- Start date
Help Support GroupDIY Audio Forum:
Hi Ed,
Thanks for shining in on my little thread, i feel very honored
and happy that i've stated earlier that i didn't want to steel anyone properties :green:
would have felt very dorky if i did after you've had showed up here
Cheers :guinness: and welcome to The Lab, hope to see you here more often :thumb:
Tony
Thanks for shining in on my little thread, i feel very honored
and happy that i've stated earlier that i didn't want to steel anyone properties :green:
would have felt very dorky if i did after you've had showed up here
Cheers :guinness: and welcome to The Lab, hope to see you here more often :thumb:
Tony
Ed DeGenaro
Member
- Joined
- Nov 19, 2004
- Messages
- 15
[quote author="tony dB"]Hi Ed,
Thanks for shining in on my little thread, i feel very honored
and happy that i've stated earlier that i didn't want to steel anyone properties :green:
would have felt very dorky if i did after you've had showed up here
Cheers :guinness: and welcome to The Lab, hope to see you here more often :thumb:
Tony[/quote]
I didn't think you were...otherwise I woulda brought the schematics thing up.
And his place looks pretty cool. And I already know two guys from real life.
Thanks for shining in on my little thread, i feel very honored
and happy that i've stated earlier that i didn't want to steel anyone properties :green:
would have felt very dorky if i did after you've had showed up here
Cheers :guinness: and welcome to The Lab, hope to see you here more often :thumb:
Tony[/quote]
I didn't think you were...otherwise I woulda brought the schematics thing up.
And his place looks pretty cool. And I already know two guys from real life.
synthetic
Well-known member
Isn't the Power Brake based on the GT Speaker Emulator? I thought that box used an actual speaker -- minus the cone -- to emulate a speaker. It apparently makes acoustic sound even though they've dampened most of the sound generation out of it. That would be a fun project to try if you had a blown speaker to play with.
Ed DeGenaro
Member
- Joined
- Nov 19, 2004
- Messages
- 15
[quote author="synthetic"]Isn't the Power Brake based on the GT Speaker Emulator? I thought that box used an actual speaker -- minus the cone -- to emulate a speaker. It apparently makes acoustic sound even though they've dampened most of the sound generation out of it. That would be a fun project to try if you had a blown speaker to play with.[/quote]
I think you're thinking of a few things at once...
Weber MASS based on the speaker thing, Palmer o3 was discontinued becuase GT stomped their foot.
Power brake is built around a switchable transformer.
I think you're thinking of a few things at once...
Weber MASS based on the speaker thing, Palmer o3 was discontinued becuase GT stomped their foot.
Power brake is built around a switchable transformer.
> But this looks like compressor.
{a few coffees later:} Yes, it does. But as I said "I need a LOT more coffee to think how the lamp and caps go (I may be totally ack-bassward here)." This was just to give Tony a general idea of complexity, not showing exact action or the extra features that apparently make this box more-usable than some alternatives.
So I got it wrong. Now Ed knows how close someone could guess just by reading the description. If someone was buying my coffee, I would eventually get the basic function right (lamp and cap the right way round). But I think you have to either be insane, or be in the amp-building business :wink: , to have the fretboard-time to tweak this complex psycho-acoustic-electric system into being "musical" instead of just a bench-toy.
If you just want to play soundlessly, you need a BIG resistor because most tube-type guitar amps will go wild without a load :twisted: . Touch the strings and get 80 Watt square-waves. Pentodes need loads.
And even loaded, you need voltage reduction. 60Watts in 8Ω is 22 volts, you want less than 2 volts for "Line In" or 2V-4V for a small soft speaker.
That's all "simple". Hey, I got a 7.5Ω 40W and some 1Ω resistors here: done.
But just loading the amp with a resistor does not do the same thing as loading in a speaker. Low-feedback pentodes driven into overload (gitar amps) are very sensitive to impedance, and speakers have wild swings of impedance. And over the decades, speaker and amp "tone" have evolved together. The speaker load is part of the amp sound. So if you don't want a speaker, you need a very good "fake" speaker for the amp to see.
Aiken Amps has a paper on speaker simulation. It is as correct as can be for a handful of components. The values may be correct for some speaker, but there will be about 50% shift in every parameter as you go from big C-130 to a little 8-incher, and of course everything scales for 4, 8, 16Ω.
Then you have to model the electro-acoustic response, which is pretty crazy stuff.
If you did build a lumpy-load with EQ, the sound might be objectively right but sound wrong to the ear, because of our response to different levels (Fletcher Munson and all that). And/or your relaxed ear might hear hiss that you wouldn't notice after a few full-blast power-chords :shock: . That's the part that would really "scare" me: changing gain in a guitar-amp seems like it would screw-up the guitarist's sense of touch. Ed is obviously both braver and a better guitarist than I am. He tackled the problem, well enough to get dealers ALL over and sell 20,000 units. Pretty darn fantastic :thumb: for what is really a very specialized tool. After all: you can sell 20,000 basic amps that suck, since the market is millions. You can sell 200 dummy-loads that suck, if you try hard enough. But selling 20,000 "dummy loads" (with important frills) means a large fraction of the total market (studios and going-deaf pickers) has felt this thing was worth more than its weight in Guinness :guinness:.
I like to understand things. Sometimes I even build things. But if Ed can tie Wil and cohorts to a bench and build 100 a day, the parts/labor cost is MUCH less than for me putzing-up one copy, even if I had the magic values. $100-$200 of parts and package, plus years of experience and months of tweaking so it "just works", plus a warranty, for $300, seems dirt-cheap to me. (It would cost me $50 in bandages just to drill the case raggedly.)
{a few coffees later:} Yes, it does. But as I said "I need a LOT more coffee to think how the lamp and caps go (I may be totally ack-bassward here)." This was just to give Tony a general idea of complexity, not showing exact action or the extra features that apparently make this box more-usable than some alternatives.
So I got it wrong.
Now Ed knows how close someone could guess just by reading the description. If someone was buying my coffee, I would eventually get the basic function right (lamp and cap the right way round). But I think you have to either be insane, or be in the amp-building business :wink: , to have the fretboard-time to tweak this complex psycho-acoustic-electric system into being "musical" instead of just a bench-toy. If you just want to play soundlessly, you need a BIG resistor because most tube-type guitar amps will go wild without a load :twisted: . Touch the strings and get 80 Watt square-waves. Pentodes need loads.
And even loaded, you need voltage reduction. 60Watts in 8Ω is 22 volts, you want less than 2 volts for "Line In" or 2V-4V for a small soft speaker.
That's all "simple". Hey, I got a 7.5Ω 40W and some 1Ω resistors here: done.
But just loading the amp with a resistor does not do the same thing as loading in a speaker. Low-feedback pentodes driven into overload (gitar amps) are very sensitive to impedance, and speakers have wild swings of impedance. And over the decades, speaker and amp "tone" have evolved together. The speaker load is part of the amp sound. So if you don't want a speaker, you need a very good "fake" speaker for the amp to see.
Aiken Amps has a paper on speaker simulation. It is as correct as can be for a handful of components. The values may be correct for some speaker, but there will be about 50% shift in every parameter as you go from big C-130 to a little 8-incher, and of course everything scales for 4, 8, 16Ω.
Then you have to model the electro-acoustic response, which is pretty crazy stuff.
If you did build a lumpy-load with EQ, the sound might be objectively right but sound wrong to the ear, because of our response to different levels (Fletcher Munson and all that). And/or your relaxed ear might hear hiss that you wouldn't notice after a few full-blast power-chords :shock: . That's the part that would really "scare" me: changing gain in a guitar-amp seems like it would screw-up the guitarist's sense of touch. Ed is obviously both braver and a better guitarist than I am. He tackled the problem, well enough to get dealers ALL over and sell 20,000 units. Pretty darn fantastic :thumb: for what is really a very specialized tool. After all: you can sell 20,000 basic amps that suck, since the market is millions. You can sell 200 dummy-loads that suck, if you try hard enough. But selling 20,000 "dummy loads" (with important frills) means a large fraction of the total market (studios and going-deaf pickers) has felt this thing was worth more than its weight in Guinness :guinness:.
I like to understand things. Sometimes I even build things. But if Ed can tie Wil and cohorts to a bench and build 100 a day, the parts/labor cost is MUCH less than for me putzing-up one copy, even if I had the magic values. $100-$200 of parts and package, plus years of experience and months of tweaking so it "just works", plus a warranty, for $300, seems dirt-cheap to me. (It would cost me $50 in bandages just to drill the case raggedly.)
> a pity that they come in different versions depending on the impedance... i need at least 2 or 3 for our studio...
Ed, this seems to me like a serious marketing problem. (Though with at least 100 Google hits on the product, many of them dealers, maybe you don't have any marketing problem!)
How many string-pluckers even know their impedance?
How many people have several amps, each a different impedance?
How do dealers feel about stocking 3 part-numbers and helping customers pick the right one?
At the going prices, three boxes is a thousand bucks, not a minor expense. If you could actually get most folks to buy several, fine. But I suspect some folks go paralyzed when faced with a decision and buy none.
I understand why it isn't a simple switching problem. About 6 parts have to be changed, and the values don't really lend themselves to series/parallel combinations, which are not easy to switch anyway. But putting 18 parts in a box more than doubles cost.
How expensive would it be to use an autotransformer in front? Then one set of values covers 4-8-16Ω. A 100 watt rating only needs about a 30 watt core. If this is guitar-only, it can be a little short in the bass, and quite short in the treble: 80Hz-8KHz.
As an extreme design: transforming everything to 100Ω -might- allow use of film-caps instead of electrolytics (I assume you use electros if you model the bass-lump). That might not reduce cost but might add snob-appeal. It also makes the box bigger and heavier, which might make it "feel more valuable".
Ed, this seems to me like a serious marketing problem. (Though with at least 100 Google hits on the product, many of them dealers, maybe you don't have any marketing problem!)
How many string-pluckers even know their impedance?
How many people have several amps, each a different impedance?
How do dealers feel about stocking 3 part-numbers and helping customers pick the right one?
At the going prices, three boxes is a thousand bucks, not a minor expense. If you could actually get most folks to buy several, fine. But I suspect some folks go paralyzed when faced with a decision and buy none.
I understand why it isn't a simple switching problem. About 6 parts have to be changed, and the values don't really lend themselves to series/parallel combinations, which are not easy to switch anyway. But putting 18 parts in a box more than doubles cost.
How expensive would it be to use an autotransformer in front? Then one set of values covers 4-8-16Ω. A 100 watt rating only needs about a 30 watt core. If this is guitar-only, it can be a little short in the bass, and quite short in the treble: 80Hz-8KHz.
As an extreme design: transforming everything to 100Ω -might- allow use of film-caps instead of electrolytics (I assume you use electros if you model the bass-lump). That might not reduce cost but might add snob-appeal. It also makes the box bigger and heavier, which might make it "feel more valuable".
PRR, thanks again for the insight!
Our posts crossed :grin:
I don't have all these amps, but get a lot of people into the studio. Could i buy a trannie to help me out with this? as an input prior to the Hotplate?
Just had a good read about impedances and (mis)matching, powersoacking, speakers, ... the works on http://www.amptone.com
Still it gives me doubt as overthere, all Mr gtrs agree that powersoaking/reduction can't work because of the missing speakerdistortion generated by a heavy driven amp.
That's obviously what i still hear what's missing in my holygrailgtrtone.
But, i'm too curious now... will check with my local supplier and give it some deep testing...
THD, i'll check you anyway, i'm sure you deliver a fine product, but my ears aren't easy to satisfie, so if it doesn't work out, same friends :green:
Louder is better :sad:
Maybe i need a Marshall studio 15 watt amp?
Heard a few mp3 on www.amptone.com and i'm impressed about what these little geezers spit out in raw power! :twisted:
Our posts crossed :grin:
I don't have all these amps, but get a lot of people into the studio. Could i buy a trannie to help me out with this? as an input prior to the Hotplate?
Just had a good read about impedances and (mis)matching, powersoacking, speakers, ... the works on http://www.amptone.com
Still it gives me doubt as overthere, all Mr gtrs agree that powersoaking/reduction can't work because of the missing speakerdistortion generated by a heavy driven amp.
That's obviously what i still hear what's missing in my holygrailgtrtone.
But, i'm too curious now... will check with my local supplier and give it some deep testing...
THD, i'll check you anyway, i'm sure you deliver a fine product, but my ears aren't easy to satisfie, so if it doesn't work out, same friends :green:
Louder is better :sad:
Maybe i need a Marshall studio 15 watt amp?
Heard a few mp3 on www.amptone.com and i'm impressed about what these little geezers spit out in raw power! :twisted:
Tim Campbell
Well-known member
Hey Ed,
The next Indian dinner's on me!!!
The next Indian dinner's on me!!!
> Mr gtrs agree that powersoaking/reduction can't work because of the missing speaker distortion generated by a heavy driven amp. That's obviously what i still hear what's missing in my holygrailgtrtone.
I'm not sure speakers distort that much at guitar-amp levels. Some at bass resonance, true. But a lot of that phatt-bass is the pentode amp seeing the impedance rise at bass resonance and going crazy with under-loading. This effect has been known a LONG time: it is a prime point in Radiotron Third.
A load resistor alone is not enough. Be sure it simulates speaker impedance. And that bass-rise isn't an easy thing to simulate with cheap coils and capacitors.
> Maybe i need a Marshall studio 15 watt amp?
On the one hand: I dunno why 100 Watt 550V amps don't have a power supply tap for 100V plate supply, which would give few-watt operation at clipping. If you drop the driver voltage too, all the tube distortion should scale fairly well. If nothing else, it could be handy for tuning-up while the jukebox/DJ is still going, since it can't make a big noise to disturb the filler-music. What would not scale is the transformer distortion, so there may still be a need for a small-parts amp to run at small power with "tone".
On the other hand: Fletcher-Munson is still gaining bass at 95dB SPL, and you really don't want to play louder than that, but at 85dB SPL you are far down the loudness bass-loss curve. So a small amp won't have the balls of a big amp, unless it is EQ-ed different and has good big speakers. So push-pull 6V6 at under-voltage and small output iron, but still with 2-10" or a nice 12" speaker.
Traditional ear-damage laws suggest that loud bass is not as harmful as loud treble. I'm not sure bass is as "safe" as hearing-damage laws seem to think, but there is good reason to think treble hurts more. So a ballsy sound without so much scream may be a way to go. Since you always run up to the clip-point, and speaker on-axis output may increase in the higher frequencies due to voice coil inductance and pentode impedance, you might actually go back to the old trick of a capacitor across the output (very common in tube home radio). 0.01uFd across the primary works, though with 100W push-pull outputs living in clipping it has to be a VERY high voltage rating (over 1,000V).
> check with my local supplier and give it some deep testing...
I think that's key. What it seems to do can't be described well enough to blind-buy it. But part of the price makes the dealer happy, probably happy enough to let you play Satisfaction full-bore to help you get the effect. And Ed probably knows more than he can put in the product: if he thinks you can be trusted with a solder iron, he may know more tweeks to get more of what you want for your style.
I'm not sure speakers distort that much at guitar-amp levels. Some at bass resonance, true. But a lot of that phatt-bass is the pentode amp seeing the impedance rise at bass resonance and going crazy with under-loading. This effect has been known a LONG time: it is a prime point in Radiotron Third.
A load resistor alone is not enough. Be sure it simulates speaker impedance. And that bass-rise isn't an easy thing to simulate with cheap coils and capacitors.
> Maybe i need a Marshall studio 15 watt amp?
On the one hand: I dunno why 100 Watt 550V amps don't have a power supply tap for 100V plate supply, which would give few-watt operation at clipping. If you drop the driver voltage too, all the tube distortion should scale fairly well. If nothing else, it could be handy for tuning-up while the jukebox/DJ is still going, since it can't make a big noise to disturb the filler-music. What would not scale is the transformer distortion, so there may still be a need for a small-parts amp to run at small power with "tone".
On the other hand: Fletcher-Munson is still gaining bass at 95dB SPL, and you really don't want to play louder than that, but at 85dB SPL you are far down the loudness bass-loss curve. So a small amp won't have the balls of a big amp, unless it is EQ-ed different and has good big speakers. So push-pull 6V6 at under-voltage and small output iron, but still with 2-10" or a nice 12" speaker.
Traditional ear-damage laws suggest that loud bass is not as harmful as loud treble. I'm not sure bass is as "safe" as hearing-damage laws seem to think, but there is good reason to think treble hurts more. So a ballsy sound without so much scream may be a way to go. Since you always run up to the clip-point, and speaker on-axis output may increase in the higher frequencies due to voice coil inductance and pentode impedance, you might actually go back to the old trick of a capacitor across the output (very common in tube home radio). 0.01uFd across the primary works, though with 100W push-pull outputs living in clipping it has to be a VERY high voltage rating (over 1,000V).
> check with my local supplier and give it some deep testing...
I think that's key. What it seems to do can't be described well enough to blind-buy it. But part of the price makes the dealer happy, probably happy enough to let you play Satisfaction full-bore to help you get the effect. And Ed probably knows more than he can put in the product: if he thinks you can be trusted with a solder iron, he may know more tweeks to get more of what you want for your style.
NewYorkDave
Well-known member
RE: PRR's point about using one set of reactive components and putting an autotransformer in front of it to transform to different impedances, that's exactly what the Marshall Powerbrake does. The autotransformer also acts as the level control (it has several taps).
The impedance selector changes which set of taps the reactive load connects to, so that the desired nominal impedance is reflected to the amp. The circuit is arranged so that the dummy load and the real speaker connected to the output jack are both reflected to the source at the appropriate turns ratio to keep the nominal impedance more-or-less constant as the ratio of power sent to one load or the other is varied in steps.
There used to be a Powerbrake schematic up on the web, but I can't seem to find it now.
The impedance selector changes which set of taps the reactive load connects to, so that the desired nominal impedance is reflected to the amp. The circuit is arranged so that the dummy load and the real speaker connected to the output jack are both reflected to the source at the appropriate turns ratio to keep the nominal impedance more-or-less constant as the ratio of power sent to one load or the other is varied in steps.
There used to be a Powerbrake schematic up on the web, but I can't seem to find it now.
clintrubber
Well-known member
from NYD:
It was definitely there, but I don't know right now where I got it from.
BTW, if anyone's interested in the schematics of the Marshall SE100 (and if that's OK to provide) I'll have a look where I put those. The SE100 is the rackmount bigger brother of the powerbrake - I thought it does both present a reactive load and some active filtering.
Last but not least, the Groove Tubes patent (United States Patent 4,937,874) is an interesting read (but probably redundant after the above posts).
Bye,
Peter
It was definitely there, but I don't know right now where I got it from.
BTW, if anyone's interested in the schematics of the Marshall SE100 (and if that's OK to provide) I'll have a look where I put those. The SE100 is the rackmount bigger brother of the powerbrake - I thought it does both present a reactive load and some active filtering.
Last but not least, the Groove Tubes patent (United States Patent 4,937,874) is an interesting read (but probably redundant after the above posts).
Bye,
Peter
PRR, i'm not sure if the "lowend" in the sounds i'm after is the problem, it's really more something at overdrivecharacteristicslevel, the kind of distortion doesn't seem right for me anymore when going tru outputreducers whatsoever... probably too because the poweramp sees other things going on at the loadside of things?
Flectcher/Muson might also trick me a little but even when i record the loud versus reduced sounds and monitor at equal level, my impression stays confirmed about this. It is comparable as if i would put a bassboost prior to distortion instead of post poweroutput bassboosting if this makes sense to anyone?
Sorry for my invented english vocabulary, my oldest daughter studying English at university would laugh her but of reading some of my posts here :green:
dukasound
Well-known member
[/quote]BTW, if anyone's interested in the schematics of the Marshall SE100 (and if that's OK to provide) I'll have a look where I put those. The SE100 is the rackmount bigger brother of the powerbrake - I thought it does both present a reactive load and some active filtering.
Peter[/quote]
Hi Peter
I am owner of SE100 and if you have schematic it would be fine.
Thanks in advance
Duka
Peter[/quote]
Hi Peter
I am owner of SE100 and if you have schematic it would be fine.
Thanks in advance
Duka
clintrubber
Well-known member
Please stay tuned, hope to put them up one of the upcoming days.
BTW, do you like this unit ? Please tell.
Ed DeGenaro
Member
- Joined
- Nov 19, 2004
- Messages
- 15
[quote author="PRR"]> a pity that they come in different versions depending on the impedance... i need at least 2 or 3 for our studio...
Ed, this seems to me like a serious marketing problem. (Though with at least 100 Google hits on the product, many of them dealers, maybe you don't have any marketing problem!)
How many string-pluckers even know their impedance?
How many people have several amps, each a different impedance?
How do dealers feel about stocking 3 part-numbers and helping customers pick the right one?
At the going prices, three boxes is a thousand bucks, not a minor expense. If you could actually get most folks to buy several, fine. But I suspect some folks go paralyzed when faced with a decision and buy none.
I understand why it isn't a simple switching problem. About 6 parts have to be changed, and the values don't really lend themselves to series/parallel combinations, which are not easy to switch anyway. But putting 18 parts in a box more than doubles cost.
How expensive would it be to use an autotransformer in front? Then one set of values covers 4-8-16?. A 100 watt rating only needs about a 30 watt core. If this is guitar-only, it can be a little short in the bass, and quite short in the treble: 80Hz-8KHz.
As an extreme design: transforming everything to 100? -might- allow use of film-caps instead of electrolytics (I assume you use electros if you model the bass-lump). That might not reduce cost but might add snob-appeal. It also makes the box bigger and heavier, which might make it "feel more valuable".[/quote]
It's not a marketing nightmare, but it can be a pain in the ass.
I answer numerous calls and e-mails everyday for wat impedance model to use. I don't have to explain to you why there are dfferent models, you already showed that you understand it.
As for the autotransformer, we're playing around with stuff but I can't talk about it yet.
On the flipside, everybody else that uses the resistor idea (Airbrake variety) has a fixed value of 8 ohm and then mismatches to 4 or 16. You can do the same with a 8 ohm Hot Plate. Just happens we think that matched loads sound better.
Ed, this seems to me like a serious marketing problem. (Though with at least 100 Google hits on the product, many of them dealers, maybe you don't have any marketing problem!)
How many string-pluckers even know their impedance?
How many people have several amps, each a different impedance?
How do dealers feel about stocking 3 part-numbers and helping customers pick the right one?
At the going prices, three boxes is a thousand bucks, not a minor expense. If you could actually get most folks to buy several, fine. But I suspect some folks go paralyzed when faced with a decision and buy none.
I understand why it isn't a simple switching problem. About 6 parts have to be changed, and the values don't really lend themselves to series/parallel combinations, which are not easy to switch anyway. But putting 18 parts in a box more than doubles cost.
How expensive would it be to use an autotransformer in front? Then one set of values covers 4-8-16?. A 100 watt rating only needs about a 30 watt core. If this is guitar-only, it can be a little short in the bass, and quite short in the treble: 80Hz-8KHz.
As an extreme design: transforming everything to 100? -might- allow use of film-caps instead of electrolytics (I assume you use electros if you model the bass-lump). That might not reduce cost but might add snob-appeal. It also makes the box bigger and heavier, which might make it "feel more valuable".[/quote]
It's not a marketing nightmare, but it can be a pain in the ass.
I answer numerous calls and e-mails everyday for wat impedance model to use. I don't have to explain to you why there are dfferent models, you already showed that you understand it.
As for the autotransformer, we're playing around with stuff but I can't talk about it yet.
On the flipside, everybody else that uses the resistor idea (Airbrake variety) has a fixed value of 8 ohm and then mismatches to 4 or 16. You can do the same with a 8 ohm Hot Plate. Just happens we think that matched loads sound better.
clintrubber
Well-known member
Hi Duka,
Here we have the (3) files of your unit:
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0789.pdf
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0790.pdf
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0791.pdf
Here we have the (3) files of your unit:
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0789.pdf
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0790.pdf
http://home.hetnet.nl/~chickennerdpig/FILES/SE-100/pc0791.pdf
