Chienmortbb

Of course if you talk to the transformer manufacturers, they will claim (and do) that the valve sound is mostly down to the way the output transformer behaves. I am not conforming that but is does seem to question the value of valve preamps. As for the look pf the amp, I was trained in the late 60's and all test equipment looked like that. So I suppose I am suffering nostalgia.

Warning boring technical content. From memory (not too good nowadays) the ABM and MAG range use Class AB output stages using power FETs similar to the old Trace designs (can't remember whether they are VFets or Mosfets. Advantages over bipolar transistor output stages are that the the transfer charateristic is closer to valve than transistor so clipping is less harsh, and they do not suffer from thermal runaway (if the heatsink is too small or ambient temerature is too high). Disadvantages are that they give out less power (fewer watts) for a given power supply voltage so transformers are bigger (hence heavier). Incidentally it is a lovely looking amp. Looks like it means business.

Is this the marketing dept. using what they copnsiser a musical adjective?

Seems like two steps forward and one step back at the moment. I was doing a parts order and added some tiny 9mm pots from AlphaTaiwan. One was for the FX return level control. Unfortunately I did not read the spec carefully enough and I got a PCB mounted pot with a knurled shaft. It is not chassis mount. So as I did not want a big knob on the back panel that was proud of the back of the case, I set about mounting the pot on some stripboard with the idea to mount it on pillars, it worked quite well as you can see in the pictures attached. As I was tightening the slotted screws that held the stripboard and pot, the screwdriver slipped and gouged the back panel. I did a test spot of brush applied varnish and it seemed to work well but over a larger it looked terrible. So I disassembled the panel, rubbed it down then applied the last of the spray lacquer I had. Not great but just about passes muster.

post 349 gives the dimensions

[quote name='Phil Starr' timestamp='1438501882' post='2834879'] There are essentially three limits to an amplifiers power output. The voltage it can swing, the current it can provide and the heat it can dissipate. In any given amp one of these will be the important limiting element. (I'm ignoring any protection circuits or DSP here) There are lots of ways to measure and calculate an amps output even if you stick to rms. they range from just measuring the voltage swing and calculating the power that voltage would drive through 8ohms to connecting the amp to a dummy resistor and running sine waves through it for a week and measuring the temperature rise. Different amps work differently so can scre better in some tests than others. It's relatively easy to switch huge voltages so class D amps score well here. Since in most applications the power is only needed for a fraction of a second it makes no sense to put in a huge power supply so this is often the limit. With transistor amps high voltage devices are more expensive and the transistors are prone to thermal runaway so heat is the problem even if the power supply is big enough. Valve amps were usually limited by current, not least because all the power would go out through the output transformer. So, a watt is still a watt but there is a lot of room for confusion and even when standard tests and rms watts are used there will be amps that seem louder than others. The other aspect of this though is the speaker. There is no single drive unit that can handle 1000W continuously at all frequencies, and if you use 1000W through multiple drivers then the sound levels developed are going to be so high as to be unusable on stage. These sorts of powers are only useful for PA arrays safely suspended way above the band and audiences heads. To answer one of your questions. A 3000W rated amp limited by heat and power supply to1600W continuous could be treated as a 1600W amp except it could also put 3000W through your speakers for long enough to damage them. In fact real world speakers rated at, say, 800W rms 1600W peak probably can't handle 200W at some frequencies. We are are all going to have to get used to class D amp ratings. Affordable power is now effectively unlimited, there are a few problems with power supplies but we are going to have to decide to be careful about what powers we wish for. [/quote]Very good points Phil. To add my two pence worth, Valves or Bipolar or Mosfet amps can all be made in Class A, B, AB or D (Class C are radio/tv transmitter power amps and E,G and H are all variations on Class B IMHO). Firstly why do valve amps sound louder. Well to some extent it is a limitation of Valves that they need a transformer to drive low impedance speakers. It is easy to Tap a transformer to match the power output of the amp to the loudspeakers. So a 100W valve amp will give 100W into 4,8 and 16 Ohms of the trasformer is tapped at those impedances. An amplifier without a transformer will suppy different powers into different loads (speakers). A perfect Solid State amplifier might give 50W into 16 Ohms, 100W intp 8 Ohms and 200W into 4 Ohms (It might even give 400W into 2 ohms. No marketing department would dream of calling this a 50W amp. It would be called a 200W amp. So do a test with the 100W Valve V the 200W SS into 8 Ohms and guess what. They sound the same UNTIL the amps are pushed hard the soft clipping or self compression of a valve ourput stage kicks in. The valve amp will sound louder. If the 200W amp has a good compressor the differences will be subtle. Coming on to the power supply this is a big limiting factor. The biggest single cost component in an SS amp, Whether Class AB or Class D is either the transformer or Switch Mode Power Supply. So an amp that can output 250W into ohms may be limited to a much lower level into 4 Ohms. Take a very good amp like the Hartke HA3500, an amp you know well. It is specified as 240W into 8 Ohms and 350W into 4 Ohms. Almost certaily the 4 Ohm figure is power supply limited. Marketing departments are also guilty of using bogus ratings. A number of makers use the Anaview [b]Class D ALC0300, [/b]one manufacturer has used it for amps with a claimed outputs of 640, 420 and 320 watts. It is rated as 200W into 8 ohms and a recent change uprated the 4ohm output from 320 to 350 watts. So clearly 640 is twice 320, and 420 is the peak output specified by Anaview. All these are specifies at 1% distortin figures but some makers quote at 10% distortion that can give a figure almost 40% higher but would be unuseable in real world use. The giggest problem for me is that hardly anyone gives a true technical specification for their amps. so it really makes it hard to compare amp to amp even from the same make. Many amps are quoted at their maximum output assumimg that heatsinking or fans are at the optimum level. Then use pathetic heat management that means the amp cannot possible reach its quoted output for more than a few seconds. There are lies. damn lies and specifications. So how do we compare amps? I would suggest always compare at 8 Ohms. So halve the output of a Solid State Class A/B or Class D Amps when comparing with a Valve amp. After that listen but remember that although the ear has no memory and is influenced by the eye. A big SVT looks louder than a small Class D amp but is it? How much is down to the "voice" of the amps being compared. Don"t compare a sound with the one you remember, it will be innacurate. The only valid comparisons are blind A/B test that happen at the same time and place.

[quote name='Roland Rock' timestamp='1438459070' post='2834708'] Is your sarcastic gybe based on the fact that you think I was talking about Class A and Class B amps? I wasn't - I was referring to two different hypothetical types of amp labeled Type A and Type B. [/quote] Yes. Sorry I misread you post. Blame it on my bad eye.

[quote name='Roland Rock' timestamp='1438429482' post='2834462'] Real world you say? I have a 1000w Type A power amp which easily handles the lows. Then I sell it, and with half of that money buy a cheaper Type B 3000w power amp which handles those lows just as well. Great. My inner voice will be nagging me to buy the 3000w version of the Type A power amp, as it will be amazing. I'm now skint with an aching back, but happy. [/quote] So as a Class A amplifier is around 10% efficient, you need 10000 watts or around 40 Amps of current at 230V. Three times what you can draw fro a single socket ( unless you are running three phase) it is August not April isn't it!

So what do you consider a super tweeter. I am not asking for a particular technology rather what the frequency response of a good tweeter is. Also is there an argument for a Low Pass Filter before a tweeter? I wi be honest, putting a tweeter in a bass cabinet that extends to way over 20KHz seems crazy to me even fior slapping. So any ideas on what the top -3dB point should be for a tweeter? I have no real opinions myself, just trying to learn from other people.

How much extra bracing will the slot port give. Will it make room on the baffle for more bracing?

Dood said "[color=#282828][font=helvetica, arial, sans-serif]Engaging the bright switch and setting the passive tone stack to that classic scoop setting (all controls pointing up) tamed the cabinet. A little bit of excess cone movement - but I think the Kilo has absolutely no subsonic filtering. "[/font][/color] [color=#282828][font=helvetica, arial, sans-serif]Do you think that and HPF should be fitted to al amps? The amp I am buiding has an adjustable one and the more learn about speakers, the more I am convinced they are vital.[/font][/color]

The midpeak on the SM212 is less pronounced than either of the Kappalite 12" speakers. I wonder why is it so obvoius here? I can understndthat the 3012LF may be cossed over at 1-2KHz meaning the peak is missed or at least tamed. However the 3012HO peak is much closer to 1Khz and that has been used in a number of commercial cabs. I understand that mids reflect off the rear of the cabinet and come through the cone but does that also mean that they bounce back through forward facing ports? I am sure I read that Audio Kinesis put their ports on the back because of this but I may be remembering incorrectly. If so that is correct, might there be some reduction with a slot port? Dood, can you compare this to any commercial cab you have reviewed or used?

I hAve finally completed fitting and soldering the Pre Amp PCB and the High Pass Fillter & Parametric Equaliser PCB. They are pictured now in place on the chassis.

Mods, perhaps you could combine tis thread and the one entitled [b] Class D amps lack uumph?[/b]

[quote name='Grangur' timestamp='1437394755' post='2825552'] So am I reading this right; it seems they don't fail on you when in use, you arrive at the practice studio and you find them not working? I recommend you start taking your amp home. YOU might not abuse it, but others may not be so careful. Is someone connecting a lower impedance cab than is recommended? Or some other problem? Fact: electronic devices don't fail when not in use, unless it's water or heat damage, and you'd see signs of that. [/quote]you are correct, most failures happen upon switch on when the most electrical stress is on the amp.

[quote name='Truckstop' timestamp='1437284050' post='2824781'] The way I've always thought of it as, is that Class D 'sounds' loud while class A 'is' loud. [/quote]Class A is not used an any real amplifier over about 10 watts. You probably mean Class A/B.

Sure to some the idea of the sound or response changing if the cabinet is rotated is ridiculous but allegedly many silly things change the sound of a cabinet. To me it appears that there will be very little change but if the driver is closer to the floor then there will be a change, albeit quite small. The question is clearly prompted by the idea that tall is better than wide for bass drivers, when used in multiples. On a final note, having read many forums/ threads on speakers, there are more daft answers than daft questions.

[quote name='Phil Starr' timestamp='1436972739' post='2822477'] Stevie's right. (I keep saying that) we started out talking about offering either a Celestion or the Eminence Beta 12A-2 as a cheap option with the Beyma as midprice and maybe the 3012HO as the deluxe version. Modelling showed the extra for the Beyma was worth the money and the 3012 was offering almost nothing for a lot extra. Which made life simpler for us. [/quote]When I first saw you were using the SM212 I was a little surprised but when I modelled it I could see why you chose it. When you take the price into the equation (well in Europe anyway) it is clearly the best driver for the project. It is about 1.4Kg (about 3 lbs in old money) heavier than the eminence speaker and handles slightly less power but the sensitivity in the low and low mids area is very similar and is hardly a dealbreaker.

The Thumpinator is a High Pass Filter. That mean low cut so it us cutting the very low stuff that you can't hear but can hurt your speakers. SFX do not publish their specs but I suspect it is around the 25-35Hz region. This is where most modern bass reflex cabinets lose control of the speaker come, allowing it to move a long way with very little power applied. This really low area adds nothing to your sound and cutting it helps your amp too as you are not asking it to power sound you don't want. The filters in amps are often too high and do cut the sounds you want. I have heard that some amps cut from 75Hz and that is too high to just take the speaker. However the new thinking is to combine a fixed HPF for speaker control won't a variable one that can adjust for room boominess. Look on TB for FDeck's HPF thead for more info. Going back to the original thought about the thumpinator, it will give real benefits even if you cannot hear them!

[quote name='Passinwind' timestamp='1436882283' post='2821661'] Nice job. Are you using a pot for setting final stage gain where R24 would go? And I also agonize a lot more about front panels than the back ones. [/quote] You spotted the deliberate mistake.Actually I cannot find that value at the moment so I am going through my stash to find it. I was not planning to have a pot but now you mention it it could be a good idea. One issue though is that using a pot cups put the gain close to 1. ( or -1 as th opamp is inverting) the plan is to use LM4562 as the output opamp and this works well at unity gain. Other similar opamp a such as NE5532 becomes unstable at unity gain so a pot would probably need a series resistor to ensure stable operation if other opamps are to be used. Having said that I think I have just talked myself out of using anything but the LM4562.

Now I would appreciate some suggestions. The system is very flexible. I can choose to switch various circuits in or out. So the questions I am going over are: 1. Should I have the HPF switchable? Pasdinwind dies but after using his amp for some months he leaves it on all the time. 2. Effects return can be configured as series or parallel. Most Amps are currently series but parallel allows some local control over the wet/dry signal mix. Oh and should those the switch and EFX return level control be on the front or back? 3. The Parametric EQ section gives me control of the mids from about 100Hz to. 2000Hz and of course this overlaps the fixed middle control. It is worth adding a switch to change the fixed mid frequency? It makes the amp more flexible but more complex. 4. Active/Passive switching and gain change. Passinwind has only active basses while I have currently only passive ones. At least one of my bases will be converted to active in the next few months with a variation of the two band MM preamp but I want to have the ability to have the two options. So two Jack sockets or one Jack plus an Active/Passive switch? I would appreciate any comments based on experience.

Ironically the omissions make for a more satisfying build. I am studying the circuit diagram/schematic more closely than I would if documentation were 100% and learning more as I go. The Pre amp board is now complete apart from the wiring. Some of the components are now mounted off board as the preamp was designed before the HPF/PEQ circuit and taking components off board allows us to configure the circuits to the best arrangement. Below is the picture of the completed board. It still needs to be wired but I will leave that until the front panel is complete. As you can imagine I am taking more time and care over the front panel as it will be on show more than the back panel.

[quote name='Phil Starr' timestamp='1436867829' post='2821446'] More news, one of the cabs is to be reviewed by Dan Veall, bass reviewer of Interactive Guitar Magazine http://www.iguitarmag.com/reviews/?issue=&brand=&producttype=Bass and of course Dood of this parish. At the present the Cab is about to wing it's way to Dan, or it will be once UPS collect it. It'll be great to have a professional and independent opinion of the cab and I'd like to thank Dan for taking the time to do this. [/quote] Having seen some of Dan's reviewsI think this is great news. On another matter. Stevie is comparing the cab to his own 15/6 cabinet. Can you tell us more about that cab? Is it your own design or based on ages boy plan. What drivers? Size and weight? By the way I thought I knew a bit about speaker design but have learned how much I did not know during this process. Thanks for the hard work and patience with me and others.

[quote name='Phil Starr' timestamp='1436867829' post='2821446'] More news, one of the cabs is to be reviewed by Dan Veall, bass reviewer of Interactive Guitar Magazine http://www.iguitarmag.com/reviews/?issue=&brand=&producttype=Bass and of course Dood of this parish. At the present the Cab is about to wing it's way to Dan, or it will be once UPS collect it. It'll be great to have a professional and independent opinion of the cab and I'd like to thank Dan for taking the time to do this. [/quote] Having seen some of Dan's reviewsI think this is great news. On another matter. Stevie is comparing the cab to his own 15/6 cabinet. Can you tell us more about that cab? Is it your own design or based on ages boy plan. What drivers? Size and weight? By the way I thought I knew a bit about speaker design but have learned how much I did not know during this process. Thanks for the hard work and patience with me and others.

[quote name='stevie' timestamp='1436712482' post='2820116'] I didn't carry out a full-range measurement, I'm afraid, which would have shown up an imbalance between the bass and midrange. I did a ground plane LF measurement and a gated mid/high measurement but couldn't join them together because the first one was not calibrated. In any case, you need to factor in the changes in frequency response from the cabinet being on the floor, which makes a gated measurement problematical because it relies on filtering out all reflections. I've found that an RTA works well for checking the sound balance of a speaker in situ, but I didn't do one when I had the speakers here. I do know that my own 15" + 8" is ruler- flat on the RTA, which suits me, although others may well prefer a mid-foward balance. I can have a closer look at this when the speaker makes its way over here again. [/quote] No problem. I would prefer a flat response but I have enough control on my amp to EQ it flat if need be. Incidentally what sort of frequencies do you consider Mids? I tend to think 400-800Hz but I think many think mids start much lower.