Mottlefeeder

+1 for Steve Robinson David

Dirty contacts may be the cause of your switch-on click, or alternatively, a faulty output relay could cause that, and the distortion that you are hearing. I've only used Ashdown to repair one of their amps (fried by a faulty generator), so I cannot comment on amp techs in general, but there have been threads on that topic. David

if you don't know its history, it's possible that whatever ambient crap the fan pulled through it has tarnished the Fx socket contacts, and also some of the other switches, so yes you probably need an amp tech, but it may be no worse than cleaning the various contacts in the signal path. This is the type of jack socket fitted to the FX circuit of a Hartke HA4000 This is the state that the contacts were in This is what they looked like after cleaning David

Having seen the block diagram, I suggest starting with a mic cable from the DI out to your mixer. That will check out the whole preamp (post EQ) or just the input stage (pre-EQ) while bypassing the Fx sockets (which might be the problem). David

I may be wrong, but I think headphones are normally fed from the main amp via an attenuator, so: a) using your bass to BD121 to Fx-return would bypass most of the preamp, and b) using bass to BD121 to amp input, and Fx-send to mixer to headphones would bypass the amp Make sure to make all the connections with the power off and the volume controls off to avoid noisy surprises. Siully question, but can't see the answer in your original post - have you tried bass to GK to BF cab without the Behringer, in case it is the faulty item? David

Having got as far as narrowing down the fault to the amp, I'd check the preamp outputs and tuner outputs for distortion. This will tell you whether the fault is in the Amp or the preamp. The former is likely to be much more expensive, but the latter may be as simple as dirty contacts on the FX send and return sockets. David

I use a strap to secure my bass to the side of the speaker cab, or to secure the gigbag to the side of the speaker cab, so I can just slide the bass into it when we stop for a break. It works if you have one tall cab or two stacked cabs. Markbass do/did a purpose made strap for this. David

Thanks Phil. David

I've seen triangular ports in some designs, but never seen any guidance about how to calculate them. Are they calculated as square ports and built in two halves, or is there some correction factor needed to compensate for the extra resistance of the additional wall, and the effect of the cab walls close by? David

I'm not familiar with that amp, but have you considered a 2U rack tray as an alternative. If the amp is open-topped you couldd use the tray upside down. https://www.studiospares.com/ProductDetail.aspx?p=401350 David

Yes, Kala do 5-string models in their solid body range. The scale length is 23.5 inches as against 22 inches for a typical u-bass. Aquila do a 5-string set, but the low B is from their Red series, so it looks a bit odd on a BEAD 4-string, but it works for me. David

You might need to check the speakers used before deciding that. If they use 4 x 32 ohm speakers to give you a 8 ohm cab, you can simply connect your four cabs in parallel. but if they are wiring four 8 ohm speakers in series/parallel, then your separate box connections will be come a bit more complicated, and two 2x10" cabs might be an easier option. David

Is there a problem?

They feel different in that the tensioned string does not have the length beyond the nut, and round the tuning peg, so the string is not as 'elastic' as a conventional bass. Also, with a short body and no horn, a bass strap will hold the bass two frets to the left of a typical bass, which takes time to get used to. If you play on crowded stages, open mic nights or under a small gazebo, having a shorter bass is much easier to work with. David

If you wire the amplifer output to a Jack plug, it will be shorted out momentarily every time you plug it into a socket when both the tip and the sleeve are moving passed the first contact, and possibly also when the Jack plug is unplugged and dangling free. On most occasions, the amp will be off, but one day it won't be, and since it was designed to be permanently connected to a speaker, it probably does not have short circuit protection built in. I had a similar arrangement with a high-powered speaker in a low-powered combo, with the option of using an external higher-powered amp. Setting up in a hurry on a dark stage, I managed to connect the output of one amp to the output of the other. The bigger amp fried the smaller one. I've since redesigned it to make sure it can't happen again. Whatever you do, it has to be idiot proof, so I'd suggest a 10 Amp two way switch with the speaker connected to the switch wiper, and one switch contact connected to the amp and the other to a speakon socket. No risk of shorting either amp, and nice big contacts on the switch and the plug/socket. David

400W @ 1KHz but at lower frequencies it runs out of cone movement well before that. David

Eminence provide speaker design details for most of their speakers, but you have to go to that speaker page to get to them. For your unit they offer this - http://www.eminence.com/pdf/Delta_12A_cab.pdf In a large box, it goes deep, but has limited power handling (2.5 cu ft / 60Hz / 50W). In a smaller box, it handles more power, but does not go as deep (1.35 cu ft / 78Hz / 100W or 0.75 cu ft / 100Hz / 200W). It might work in a monitor wedge, but not very well as a bass guitar speaker. David

Had two gigs yesterday - Left home at about 08:45 with my battery powered gear to get to Wythenshawe to set up bass gear and PA for a 10:00 start. Busked until 16:00 with two half hour breaks. Packed up and got home at 17:10. Loaded in the battery rig and loaded out the mains rig. Left home at about 18:00 heading for a village fair in a field in Weaverham. Set up by 19:30 - pie and chips while the other act was on, then were were on for just over an hour. Packed up while the crowd watched the fireworks - got home about 22:15. Today we started about 10:30, busking in the entrance of a local Tesco Extra. We had two bass players, so we shared the load. Musically, it was mixed - we don't have set lists, so you know most of the songs being covered, until the lead busker decides to try out a new one. For paid gigs like the evening one, we have a smaller pot of songs that we know well, but we still follow whatever the lead busker decides to do next. All the donations and payments go directly to Cancer Research UK. David http://www.loosechangebuskers.org.uk/

I'm no expert, but the style reminds me of early transistor amplifiers, which were about 100W each. It may not be very loud. David

In theory, yes you can, but in practice it would not be a good idea. Jack sockets for speakers are fairly robust, and may cope with 500W, but jacks intended to switch signal inputs tend to be more fragile. A better solution might be to install a double pole two way switch and switch the amplifier output between the internal speaker and a speakon or jack socket. Speakons are designed for that job, many jack sockets are not. David

Harley Benton being built for a German company, and Fender being a US company, could it be that your existing allen keys are imperial and the HB needs a metric one? David

Picking up on what others have said, there are two types of earth 1) A safety earth designed to blow the fuse quickly if there is a fault 2) A signal earth - often the return path of your signal circuit, or a screen to protect your signal circuit. The green/yellow wire in your mains plug is type 1, the screen in your instrument cable is type 2. The earth lift is designed to break the circuit of a type 2 earth where it might conflict with a type 1 earth, as with a DI signal between two items of mains-powered equipment. Hum can be caused by having two earth paths to a piece of equipment, ad DAD3353 mentions, but can also be caused by noisy electronics on the same circuit, or close by. The fact that the hum is location dependent, and also affects the guitarist's passive instrument, makes that the most likely culprit in my opinion. So, in those problem venues, try and identify any local lighting, gaming machines, etc, which may be plugged in to to the circuit you use, and see if the hum goes away when they are switched off. Fluorescent lighting would be an obvious candidate. David

I've been putting off posting this. My problem is that all I have are the sketches and notes that I used to build a prototype, and I do not have the skills (nor the motivation) to redraw everything so it is as clear as the instructions you would get with a kit. If there is sufficient interest, and someone wants to take that on, I wouldn't have a problem with that. This is the layout of the current battery powered head. At the back of the head, the feed to the amplifier is fused, and the feed from the battery is fused, so regardless of whether the amp is being run from an external battery, or the internal battery is being connected to a an external power source, they have some protection. I transport the head with the external battery-out and amp-in connectors disconnected, so that I cannot arrive at the venue with a part-discharged battery due to the power switch being knocked in transit. Slightly left of centre is a stereo class D amplifier pcb capable of giving 22 W into 4 ohms per channel on a 12-13 volt supply, or about 10 W into 8 ohms per channel. Each channel contains two amplifiers in bridge mode, so you cannot bridge them to obtain more power. The pcb is designed around a TA2020 chip originally made by TriPath (and marketed as 'CLass T' just to confuse things). Various pcb designs are available, but I can only comment on this one. The sensitivity is high enough that you can plug an active bass directly into it, so if you have on-board EQ, you just need this pcb amp, a speaker or two, a battery (hopefully with a fuse) and you are go to go. Alternatively, you can buy an off-the-shelf amp and preamp in a box. Googling [Tripath amplifier pcb] found this supplier of the amp module that I used - https://www.ebay.co.uk/itm/MKIII-Tripath-TA2020-PCB-25watt-Class-T-amplifier-UK-/251464814688?clk_rvr_id=1520242820360&utm_medium=cpc&utm_source=twenga&utm_campaign=twenga&utm_param=eyJlcyI6MCwicyI6OTcyMDIzNywiY2kiOiIwMzhhMTZkNDRlYWJmMDNmNjZiODRkYzNjZWUzYTQ1NSIsImkiOiIyNTE0NjQ4MTQ2ODgiLCJ0cyI6MTUyNTQ1NzQ4MCwidiI6Mywic28iOjE1MDAsImMiOjE0OTcwfQ%3D%3D&rmvSB=true Power supply To the right of the enclosure is the power supply pcb. This is the circuit and layout. The stripboard tracks run along the longer dimension, and are only shown where they are needed; links run across the shorter dimension; cuts in the track are shown with an x. This provides a fused feed for the preamp circuits, and a mid-supply voltage rail so that the op-amps can run with plus and minus supplies. The chip used is a TLE2426 which will be difficult to get cheaply unless you have an account with CPC or RS Components. An alternative would be a pair of dividing resistors each parallelled by a capacitor, as discussed here - http://sound.whsites.net/project43.htm Input circuit The front right pcb provides input buffering and gain, muting, and a feed to the tuner jack socket on the back of the amp. This is the circuit and layout. There are two input sockets, for active and passive basses. Plugging in to the passive (right) jack socket feeds through the left socket switch contacts and into the first stage op-amp. Alternatively, plugging into the active (left) jack socket opens the switches and places an attenuator in the signal path, bringing the level down to match that of a passive bass. The two jack sockets are standard Cliff or similar, where the jack socket contacts cross the tube where the jack plug fits, and are physically lifted by the insertion of a jack plug. These sockets are available with pcb pins, but they are not at 0.1 inch spacing, and do not fit stripboard. However, if you take one with solder tags, cut off half of each solder tag, and squash the remaining bit into a crude pin, it will be pretty close to the spacing you need, although the stripboard hole will need to be enlarged. The first stage op-amp feeds a buffer to the tuner jack socket, and feeds the filter pcb via the mute switch. The other pole of the mute switch is used to change the supply polarity to the front panel LED, so it shows red when muted and green when live. Filter circuit The front left pcb in the first image contains the variable HPF, variable LPF, volume control and buffers to feed the line out and amplifier pcb. This is the circuit and layout. The dual op-amp 1A and 1B is used in two standard filter Sallen Key circuits giving a roll-off of 12dB/octave. The HPF is optimised as a Butterworth filter, giving a sharp cutoff and good transient response while the LPF has a more gentle transition, intended to take out fret and string noise. The HPF operates between 30 and 120Hz (copied from FDeck's design), while the LPF operates from 20KHz down to 200Hz (copied from a Walter Harley design from 2000). I prefer to use Omeg conductive plastic potentiometers because I like the way they feel, but they have a gap of 2 rows between the two tracks. Conventional carbon 16mm potentiometers have a gap of 1 row between the two tracks, so if you want to use them you will need to modify the layout slightly. The authors of the original designs both recommended antilog potentiometers and lamented their lack of availability, settling for a log pot working backwards instead. I have used linear potentiometers and they work well over the important part of the range, but antilog pots are now readily available in carbon, although not in conductive plastic. The dual op-amp 2A and 2B is used to feed the amplifier module at the right level, and to provide a buffered line output. On both the input and filter pcbs, there is a link to allow ground-lift for the tuner, line out and amplifier out in case there were earth loop problems. I had no problems, so the earths can be hard-wired in. Apart from the supply-splitting chip TLE2426, and conductive plastic dual 100K potentiometers, all components are available from www.bitsbox.co.uk and the conductive plastic potentiometers from rapidonline.co.uk. David

My experience of that hardware is that this 'headstock' string anchor will not take a roundwound or flatwould B string. The T-bars clamp the strings behind the zero fret, but after that each string is bent through 90 degrees to be clamped by a grub screw. Thick strings don't bend like that. One option is to drill out the string anchor so that each string passes through the hole where the grub screw was, and then use a separate anchor block to clamp them, as used in the conversion of double ball end headless basses. Alternatively, you can cut away most of the metal which holds the grub screws, leaving enough of a slope or a lip to retain the new string anchor, and proceed as above. David

Not quite relevant to the OP, but may be of use - Something that I only discovered recently - shortly after the purchase of a new mixer - is that small mixers that have a low voltage AC supply for them, typically 2 x 18 Vac, like Behringer, Mackie etc, cannot be used with basic 12 V to 240 V inverters. The harmonics on the outputs of cheap inverters cause small transformers to overheat and fail very quickly. Switched mode power supplies giving a DC output are fine. David