Chienmortbb

As Lord Claber is doing a guitar cab soon we may well see a change. However seeing Pete Townsend using a mass of Fender combos at Glastonbury makes me wonder what is between the ears of some guitarists.

From memory, the SI (Systeme International) is the real name for the metric system. It has been used in the UK Engineering industry since the 1960s. I started college in 1968 and we never used the Imperial System. In engineering, mm is the preferred unit of measurement or metres for bigger items. I cannot remember seeing cm on a engineering drawing. However as I am old and of failing mental faculties (think plywood debacle) this may all be rubbish.

Passinwind built an ESP designed pre a few years ago that used a Fender style tone stack. I don't know what amp it was use with but I Seem to remember a Fender fan reported it was just like his old Fender Bassman. I will ask Charlie to respond later when he is awake.

Yesterday was Chemo day so I did not have time to upload the latest pics. Attached is the latest pic of the build. I have wired the mains and the speaker connections. I have added a ferrite core around them mains input. It is the cream coloured blob. This adds little to the amp itself although it will filter some of the high frequencies present on the mains. However its main purpose is to stop interference being injected back into the mains. You can also see the speaker cable attached to the upper left hand rail. The supplied cable was too short to reach the speakons so I used a "chocolate block" to connect the speakon cables. The reason for attaching the speaker cable by cable ties is to ensure that there's no excess pull on the connector on the PCB. The cable is quite stiff and the cable tie acts as strain relief. On the right you can just see the fuse board mounted to the right hand side of the case. These protect the auxiliary supplies from the aim amps power supply from short circuits or failures of the pre amp power supplies. I just need to connect the wires to the fuses then I can test the main amp and pre amp power supplies.

[quote name='Phil Starr' timestamp='1435832015' post='2812787'] Oh, someone asked the weight of the cab. It is 14.2 kg. [/quote] That is a good weight for a cabinet. Iwill you make up the 18mm cab before you publish the cutting plans?

Yes much more than psychology. Unfortunately almost all manufacturers inflate the output specs. One well known brand has used the same power supply/amp module in a number of models and had quoted 350W 420W and 640W. On the datasheet it shows 350W at 1% distortion. 420 peak at 10% distortion and goodness knows where the 640W came from.

Well the 220 Watt Ashdown Rootmaster is an AB but the higher powered unit is Class D. Both AlexClaber and Passinwind are right. It is all about the power supply and whether the amp/power supply are designed for pro use. The ICEPower module used in the TH500 is really designed for home hifi/home cinema use and is not really suited for use as a bass amp. The one used by Pasdinwind in his latest modular amp is a whole different beast, That said a lot of people love the TH500 so what do I know. A lot of class A/B amps and Class D use chip amps designed for the consumer market and suffer from marketing hype. Power output quoted at 10% distortion, A good Class D or Class AB or Class G or H will sound good if the content is good. And remember that most valve amps of any power is Class AB although it is usually called push pull. Now I am fascinated by Barefaced brining pit an amp. Do you have any more info Alex?

Hopefully I can post some more pics later asI have completed the mains and speaker wiring. One of the many things I have had confirmed since starting this project is that an Amos quoted power has little to do with its real world output. I don't know about valve amps, but ever snce the first solid state amp, the output powers have been quoted into 4 ohms when most speakers are 8 ohms as standard. So if we look at my old BLX130 Trace combo, it was 80 watts into the internal 8 ohm speaker, reaching its quoted 130 watts only when an extension cab of 8 ohms was connected, most combos with a speaker out are the same although some disconnect the internal speaker when the external can is connected. One point worth making here is that you should never plug or unplug s speaker when the amp is switched on. So my amp module on this build is the BoYoHo My1-251 rated at 260eatts into 8 ohms and 500 watts into 4 ohms. Sounds great but there is a caveat. This rating assumes music inputs where the average power is 1/8 the peak power. BoHoYo are not alone. ICEPower also use the 1/8 figure. The 250ASX2 is used in the Tonehammer 500 but without thermal help only outputs about 60 watts continuos. Aguilar uses two fans to cool the 250ASX2 but no extra heatsink. While this approach works, relying totally on two fans will eventually fail. As fans age they shift less and less air and will eventually not be able to keep the amp cool and the amp will shut down. A heatsink is as efficient at year 25 as it was on the day it was installed. So to enable the amp to be used at higher average powers we need to cool the amp and that either means fans or bigger heatsinks or both, I try to avoid using fans as they are often they are less reliable component and can be noisy. That is why I added the extra heatsink to my build.

Oh well one good myth destroyed by another. I must have just been lucky. Of course I have been making cabinets since 1970 but maybe my 5 builds does not give a representative sample coated to Alex's experience. Two more questions then. Is there such a think as void free ply. I mean can you order bios free or do you just have to purchase and hope. Secondly what is a void? I can only imagine knit holes or possibly where two sheets of veneer have not been lined up properly before the adhesive sets.

[quote name='stevie' timestamp='1435671339' post='2811226'] . I've no personal experience but I've heard that the Chinese stuff is to be avoided as it delaminates and is full of voids. [/quote] Below is my original post but Alwx's subsequent post suggest I am wrong. I will leave it unaltered so the next post makes sense! I am not sure of the quality of Chinese ply but the point about voids is an urban myth. When ply is made, adhesive is used to glue the layers together but it is kept under enormous pressure until the adhesive is set, the excess adhesive is squeezed to wards the edge but any knot holes or gaps are filled by the adhesive, The only voids you may find is a knot hole on the outer surfaces. However you can specify really nice looking wood for the front and back of the boards but the better stuff is exoensive.

Passinwind talks a lot of sense Stevie and when I said DIY was not the cheap option. What I really meant was that if you are looking for the lowest cost, DIY is not the way to go although this project does seem to disprove that. As for woodworking skills, fair point. Mine are reasonable although there is no sense in making the big cuts yourself.

Phil my originalm idea was to use a slot port but I have changed my mind. Why make more work for yourself, We now know the design works so why not stick with the 12mm ply and the round ports.

Phil, you have no need to apologise. Life gets in the way sometimes and you are offering your collective expertise free to the community, Having started on an amp build I have had the same problems and it always takes longer than you think to get it right. However it is no cheaper to build your own amp but it is possible to get a self build speaker at close to half the price of a commercial offering. Arguably time better spent than my amp build.

[quote name='Guinness21' timestamp='1434702592' post='2801927'] This is BASSCHAT, we don't want your guitar-playing kind around here - leave this place and never return! [/quote]I have seen the light but you know I used to use a dummy till I was two and I not ashamed of that either (mind you I still have an acoustic guitar and I am taking the 5th on the dummy)

[quote name='alexclaber' timestamp='1434364976' post='2798877'] One handle. About 100lbs. And 50 years old. [/quote]Have you ever got a decent sound out of it, Sold mine and bought an AC30 treble boost. Wish I still had it.

Health problems have prevented much progress recently and so a lot of thinking has gone on and a slight layout change. I have added more heatsink. I have attached a picture of the original layout and one with the extra heatsink. The layout adds a second heatsink and requires that the two preamp regulators move. I added the Ezra heatsink as I want to be able to use the full power of the amp and thermal management is the liting factor even with Class D, Now everyone told you the Class D amps run cool but the truth is they run cooler but some heat is dissipated. Compare a Class D Amp to a Class A/B. Most solid state amps used to be class A/B and the highest possible efficiency for Class A/B is approx 70%. That means 30% of input power is wasted as heat. So a 100W amp would have approx 43 watts waste as heat. In contrast a good class D amp would be over 90% efficient so our 100 watt amp wastes only 11 watts. In effect a 400 Watt Class D amp needs the same heatsink as a 100 watt Solid State amp. My heatsink a were designed for a fan cooled 240 watt amp and although that looks like overkill, I am not using a fan although there is room for one if needed. Despite the apparent overkill on the heat sinking, the fins on all three heat sinks are lie horizontally, the least efficient way to cool an amplifier. I hope that there is enough convection and radiated to keep the amp cool but it might need fan assutance to run at full power.

No the marketing dept doubled the RMS (average) output power. The mibass uses an Anaview power module rated at 320W. From more that is at 1% distortion. At 10% it will output aprox 420 watts. Of course those figure are at 4 ohms do you cAn halve them for 8 ohms, However how loud is sounds depends on the bass, preamp design and speakers.

[quote name='aledeville' timestamp='1432409389' post='2781258'] The Synq's are really good! Very quick and precise. I had the Crest 8200 before the Synq 3k6 and this is some difference for sure. For normal use the 1k0 is fine and delivers very much for not that much money. The 2k2 is really tough, but I was able to get the 3k6 for the price of the 2k2 (they were not in stock). So I got that going... which is fine with me Nothing can compete with these amps without making huge limitations in some points. These things are light, loud, precise and comparatively reasonably priced. [/quote]I do not know the synq amps but 3600 watts in 1U is difficult. If you tske the best Clasd D amp it will be approx 93% efficient and a SMPS will be around 90%. So your amp will be generating approx 700 watts of heat Even with multiple fans and the biggest heat sink it would be hard to keep that cool,

[quote name='dincz' timestamp='1421637632' post='2663517'] I've used a Behringer EPQ900. My only complaint is the noisy fans. [/quote]fans can be replaced although good quiet ones can be expensive.

If the control is anti-log (UK) or reverse log/ reverse audio them it is likely that the volume control is a baxandal volume control. This is where the potentiometer controls the gain of the preamp rather than the preamp boosting the signal then a pot attenuating it, This technique was used in the old HH amps. It has several advantages but none you could hear and I believe Warwick were using "marketing speak" when they described it.

[quote name='stevie' timestamp='1359754895' post='1960034'] Thin-wall cabinets ring like crazy. Plastic cabs are useless for bass. Plus a good PA cab is voiced a lot flatter than a bass cab. This is not a good idea. [/quote]you are correct in that most of those plastic PA cabs very poor at low frequencies due to the thickness of the composite used. However my Ramsa PA cabs and Subs have 15mm thick walls and external ribing and are superb, they are small but not tiny and light but not ultra light. I believe that some of Duke Le Juene's ( or could have been a Greenboy) designs were available in a composite version and they too had a good reputation. The material is fine it is the implementation that matters.

[quote name='Dad3353' timestamp='1431257751' post='2769257'] Your guitarist has a point, up to a point, though. The higher the signal, the less gain needed afterwards; any added gain will increase extraneous noise, as well as the signal. Ideally, the signal sent should be adjusted to be the optimum required, neither too low nor too high. Obviously impractical most of the time, so it could be held to be best to send as much as possible (ie: full up...) unless that's too much, in which case turn it down until the overload is gone. In practical terms, I'd leave it full up unless asked to reduce; that's the 'fail-safe' option. The same applies to the instrument. If the bass is turned down, the increased 'gain' in the amp will bring up the level, but bring with it increased noise. The higher level from the instrument, the better, from that point of view. Just sayin'. [/quote]The higher the signal the better. A good desk will have mic and line inputs and most DIs on amps, even at full output, will be well below the max level for a line input. The headroom on a decent mixer preamp would be 20-30dB and that is massive. Most Amps take the cheap way out and output around -10dB so it makes no sense to reduce that level in any way as it reduces the signal to noise ratio on that chsnnel, If the mixer or sound man can't sort it out, you need a new mixer/sound man.

[quote name='stevie' timestamp='1430910860' post='2765784'] That's a perfect design, IMO. Rod is one of the few people posting on professional audio on the internet whose advice is solid. I'd prefer the second order crossover option for use with a midrange driver. Apart from that - bang-on. There are lots of good ideas in that article. I particularly liked his comments on valve amplifiers. [/quote]Stevie Rod has some good articles on valves and valve amps and links to some good resources. They are all worth a read. I think this is an excellent project. Has given me a few ideas although I am trying to resist feature creep, Now back to my project.

Maybe it shows that us Darzet Dumplings know that all that shiny yellow stuff may not be gold.

I will probably my regret asking this but by why would anyone want a valve front end these days? If there is any magic in valves it comes from the output transformer and owner supply not the preamp.