Hey all, I have a Mutant MT1207 800w 12" car subwoofer which is in very good condition but lacking an enclosure. I've looked around quite a bit and haven't managed to dig up any of the T/S parameters, just a few conflicting spec sheets regarding the MT1210, which seems to be my subwoofer's big brother.

What I need in my enclosure is efficient bass. From the research I've done, it seems like either a tapped horn or possibly a HOG scoop would be what I'm after, but all the plans I've found are for larger Sd drivers. A 6th or even 8th order bandpass could also be an option, but from what I've read these seem to rely more critically on the correct T/S specs. (maybe that's a false assumption?)

Space is not really a huge constraint, I have about a 1m x 1m x 600mm area, which happens to be in the corner of a small-ish room.

Any and all help would be really appreciated! Thanks!

Good morning. I have a problem with two epson projectors. One is EB-825 and the other is EB-85H. After disassembling them the only difference I have found is that the second one has a less powerful lamp and the epson brand ballast besides that it does not have a temperature sensor in the ballast, the first one has the tdk brand ballast. I need to remove the ballast to put a led light on. The problem is that these projectors are not worth jumping the ballast that is upside down, but they communicate through a serial port. I have found very interesting things in this forum Прошу помощи! Создание эмулятора балласта лампы проектора Epson. (Страница 5) / Аппаратные вопросы / Форум arduino.ua the problem is that it does not have the same protocol as mine. After downloading the program to the arduino nano and connecting it, there are times when a signal comes in from the projector but the arduino doesn't respond at all because it doesn't recognize it. The problem is that I do not have an original lamp to put it to be able to read the codes that I should answer. I hope someone can help me.
Thanks in advance.

Hi

I need help with a prototype development. Do I need to change something on schematic or pcb?

Schematic is from Sony TA-E1 preamplifier. Sony is made with SMD parts, my version is with TH parts.

I have LTspice simulation(TAE1-ccsbip.asc), and if someone can help I would be very thankful.

For sale two mini Reflektor regulators along with DC Flexy from you know who. Parts from GB, additionally the DC Flexy comes with 22,000uf 40V Philips capacitor (enough to power both Minis) and LQA06T300 super fast rectifier diodes.

Edit: and of course the are in perfect working condition as they should be, currently with 5VDC output.

I'll provide additonal leds (green, red and yellow) for voltage setup and additional Dale resistors for current setup

SOLD

For sale Soekris dam 1021-02 with Nurmunds input board for spdif, optical, usb input and rpi board input.
Dac is modified with almost all mods that are suggested:
Transistor mod, capacitor mod, disable opamp output stage, just raw output is for use. Optimized power supply, 2x5v Kubota preregulator for shift levels, and lt1085 5v preregulator followed by 3,3V lt3042 and TPS7a4501 for fast transient 1.2V lines.
Dac is completed and perfectly working, just add 2x6-9V transformer for +-5V kubota regulator and 2x6v transformer for other 2 lines.

Boards:
Soekris dam 1021-02%
Nurmundss input board with input selector
Diyinhk usb board
Power supply board with Kubota and 2 other preregulators

All together for 200€ plus shipping....FREE GIFT RASPBERRY PI!!!

The traditional grid-dip meter is an old favorite of the DIY/Ham community: initially, it was a tube-based instrument, but in the sixties it has been modernized with FETs or BJTs whilst retaining the same basic operating principles.

It is a variable-frequency oscillator using a number of pluggable coils and a variable capacitor to cover the frequency range, typically ~200kHz to 100MHz.

The coil is external and can be coupled to a tuned circuit to be tested.
The grid/gate/base of the oscillator has its bias connected to a galvanometer: the oscillation combined with the grid or base rectification generates a current dependent on the activity of the oscillator.

Typically, the bias is adjusted to be on the verge of oscillation, and the frequency is varied with the coil lightly coupled to the resonant circuit under test. When the frequency of the oscillator coincides with that of the tuned circuit, a significant amount of energy is siphoned by the external circuit, leading to a sudden dip in the amplitude of the oscillations.
This dip shows on the galvanometer, and by reading the calibrated frequency dial, it is possible to know the tuning frequency with a reasonable accuracy.

The measurement process is slow and not very deterministic, but the instrument is cheap, and can have other uses, like a frequency generator, which is why it was popular for a very long time.

The alternative I propose emulates the main function of a grid-dip (determination of the resonant frequency), but uses totally (if not opposite) principles: the circuit does not oscillate until it is presented with a tuned circuit.

The circuitry of the pseudo-grid dip is essentially aperiodic, meaning it works for all frequencies without coil change or manual tuning: as soon as a tuned circuit is presented, it oscillates at its resonant frequency.

How does it work?

The oscillator is amplifier-based, and conditional on the external tuned circuit.
"Canonical" oscillators like those used in grid-dips are based on a 3-terminal active device (tube, FET, BJT, etc.) and three reactive elements: two capacitors and one inductor results in a Colpitts configuration, and two inductors and one capacitor a Hartley.
Other types of oscillator are based on a quadripole and a frequency-selective network: a typical example is the diff-amp oscillator.
This circuit is quadripole-based, but the selective network is external and also acts as a gate: in its absence, the positive feedback is completely absent.
In addition, the external circuit is only inductively coupled, to mimic the original instrument

This sketch outlines the electrical configuration:



Nothing is particularly unusual: it is an amplifier looped back on itself, except the positive feedback is nonexistent, because the input and output inductors are not coupled.
Thus, such a circuit has no chance to oscillate, but then, where is the catch?

The answer is in the geometric configuration of the coils: they are magnetically orthogonal, meaning their coupling coefficient is zero.

This is a more faithful representation of the physical configuration:



It is now obvious that no coupling can exist between the Tx and Rx coils, but how can such a configuration oscillate in the end?

The two coils divide the space into 4 quadrants: a picture of the prototype should make things clearer:



The two coils of this prototype are ring-shaped, about 27mm dia, and comprise 6 turns of wire-wrapping wire. Their inductance is a little under 2µH.
If a tuned circuit is present in any of the quadrants, it will be able to interact with both inductors, because it will not be orthogonal.
The transmission coil can induce a resonance in the tuned circuit, and in turn, the current in its inductor will couple to the reception coil.
This is shown in this simulation:



Coupling coefficients are only defined for L1/L2 and L2/L3, yet the signal from L1 manages to reach L3.

To summarize, the Tx and Rx coils do not see each other directly, but the Tx coil can “illuminate” the tuned circuit, which then becomes visible to the reception coil.

My amps in the Akai M8 chassis are working. I have started a few threads about it, but I wanted to show the finished unit. I completely stripped out the stock circuit. The chassis and stock iron now hold a 12B4 preamp followed by an RH84 (SE partial feedback 12AT7/EL84 design). This amp will soon drive the tops of a biamped open baffle setup. The 12B4 stage will also drive a mini DSP which will be used to crossover to and EQ the woofers (and a subwoofer later!).

I reused the the stock transformers and choke. I also used the current 30K pot in front of the RH84, and the original speed switch on the back of the pot switches to a little cap that will roll off the fullrangers (that may or may not be the full crossover). I swapped the 1/4" jacks for RCA's. Two inputs, a toggle switch, and pre-out jacks. I drilled out the holes for the original output jacks to install fuse holders. I used to stock sockets, though I did remove one and shift another on the channel that had the 6AR5 (hated the idea of the mono's looking different). I'm using the rectifier filament winding for the 12B4. I added a couple of dropping resistors, as the filament voltage was a little higher than ideal. I put a law faked linear PEC pot in front of each pre (500K pots with 33K resistors). I know it looks a little sloppy. I'm not used to laying things out on that sort of strip, and the additions to the pre section weren't factored in to the original plan.

To make it possible with the stock power transformers, I used SS rectification. The B+ on the EL84's is just over 300V (perfect for the RH84). The power transformer stays plenty cool, but I don't have the meter lamp (or meter) connected. I'm using a moderate sized first cap (22uf Nichicon), a giant RIFA second cap (330uf), a 5uf motor run on the 'T7 and a 33uf THSA for the 12B4. Actually, as part of sorting out the pre, I added another RC section, so there is another 22uf in there as well. A la Poinz (and others), I put a couple of 1uf caps across the filament windings. I've also got a couple of 600V film caps across the diodes, and I'm taking the B+ from the CT of transformer.

The RH84 section is built according to the schematic with basic parts. The 12B4 was more of a challenge. It was initially a little unstable (motorboating). An extra RC section didn't help, nor did changing the plate load resistor for a CCS (stacked mosfets). Using a smaller coupling cap eliminated it, but that couldn't be a permanent solution. LED bias finally did the trick. I've currently got 6 ultra bright green LED's per tube. If memory serves (I've been out of town for a few weeks), that's about 15V. The CCS is set at 17ma.

It sounds nice after only a few hours. It is plenty quiet, though the power transformers do make a little mechanical noise (as nearly all seem to on my audio circuit. It drives me nuts). A big improvement over the stock Akai circuit! Compared to my other tube amp (a variant of Eli D's El Cheapo), it fits many of the SE stereotypes. The midrange is lovely. The bass is a bit warm and soft, but my EC has a big iron advantage. This amp won't be used below 150hz anyway. The high treble seems a little polite, but it might open up. Still, what a midrange!

Overall, I'm very happy. I have very little $$ invested in this build, but stripping the original parts out and getting the pre stable did take much longer than I anticipated. Pick up an M8 if you want a fun little project. My wife even likes the look! They are easy to recap, and you may even like them stock. If not, you can do something like this. A phono stage could easily take the place of my 12B4 stage, and it would be easier on the power transformer.

Hopefully I'll soon have the whole system running.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

Hi,

I am assuming that fullrange drivers like Visaton BG20 with whizzers dont provide uniform polars. A whizzer ends up producing highs mostly on axis at the expense of spoiling the off axis response. This is an acoustic problem so cant be solved by EQ either.

Drivers like TC9 etc have a dustcap and their on axis and off axis response are uniform.

See 4&5 for visaton TC9(dustcap) and Visaton (whizzer) comparison below
Radiation patterns of full range drivers

Can whizzers be improved to yield better polars?
Does replacing whizzer with dustcap improve the polars?

Thanks and Regards,
WA

I have some McIntosh speakers pictured below. Need to know the specs for them and can’t find anything online. Originally were in Ford GT. The original model of maybe 15 years ago or so. Does anybody have any info on these?

The intent is to use them in a portable stereo build. I wanted to know some parameters in order to make ported enclosures. Is there any way of making a ported enclosure sound semi-decent without knowing the T/S parameters?

[/ATTACH]

Hello everyone!
This is actually my first post here despite being a member for almost 10 years!

I also finally decided to pursue my first-ever speaker build, having at last decided to go for the Pensil based on the Markaudio Alpair 10p.

I have decided to use 18mm birch plywood, but I'm currently wondering about this: Since the material is roughly 1mm thinner than the material used in the plans i wanted to account for this, but should i prioritize to get the internal dimensions exactly right or should I instead make sure the baffle has exactly the right width? If I just make sure the internal dimensions are right the baffle will be roughly 2mm narrower than the drawings, maybe this is negligible?

I'm thankful for any input, and I'm sure more questions will pop up along the way!

BR Anton

Hi !


I'm very new to technical stuff like this, but seeing the actual epidemic quarantine in my country I've got time to try to solve that kind of problem !


So I've got a Technics intergrated amplifier SU-C04 since 5 years. It has been working really well all this time. And yesterday, as I was preparing myself to spend a month home alone because of the virus, it just stopped working. When I push the start button, the light doesn't turn on and the sound neither.

I tried to open it and clean the dust inside but it doesn't change anything.

Any advice ?

Thank you very much


Etienne

If you are on LinkedIn, I encourage you to follow the brand, they do a pretty decent job of posting their new products on their feed.

Approximately 11", 3" voice coil and +- 14mm of LINEAR excursion. 🙂

https://www.linkedin.com/company-beta/553719/

http://www.scan-speak.dk/datasheet/pdf/28w-4878t00.pdf

Two words that constantly crop up in eBay and Aliexpress hardware descriptions, I guess via Google Translate, are 'fever' and 'bile'. Can someone who speaks Chinese tell me what the real translations are?

Hallo There

Please look on page 2

best regards abc4230

I am trying to build the Krell KSA-50. Here's the schematic of the input stage.
I couldn't manage (2N6431/2N6433) complementary pairs but instead I bought some (BC337/BC327) complementary pairs, hoping to finish the project. As far as I know, the 'hfe' of the transistors in the input stage of an amplifier need to be matched.
I bought around 2 dozens of each transistors but the 'hfe' of the NPN is not matching exactly with that of the PNP's. The closest match for 'hfe' I got was '265' for NPN and '242' for PNP's. I know there is a risk of DC offset at the output if the gain 'beta' of the transistors are not matched.
Now, if I build this amp with the transistors that I got, how much offset should I
expect at the output? Is there a limit in how much the 'hfe' can vary? Also, is there any other way like shifting (collector and emitter) resistor values to minimize the DC offset?

Please help. I am making this project on a protoboard and it will be difficult to solder or desolder the parts. I am asking this because if there is a maximum risk of the amplifier not being able to work properly, I won't build the project. Thnx everyone in advance!!!!

I got Dual CV60 for spare parts. Its power amp stage is physically damaged. However the rest is cosmetically in perfect condition. I have been thinking of using its preamp with controls and case and feed it into class D amp.
I have been using 2x50W amp like this for years and it sounds really good with my system.
Mini Class D Power Amplifier HiFi Stereo 2.0 Channel Digital Audio Amp 50W+50W | eBay

Now I have got tired with all the separate parts(Phono pre, switch box, tone control, power supplies) and accompanying cables and think to put everythin inside one box.
This Dual has very good dual rail power supply of +/-15V that could feed my DIY Phono pre as well.
So can you recommend a board that can use the Dual power and sound good according to your experience? I think that 50W per channel is plenty - I haven't got past 4 notches(out of 10) on Volume knob ever.

While searching for low power car amps I found this one and since I did not find any review video of this one.

I was wondering if anyone could give there opinon on this amp as the seller claims that it has exceptional sound.

AZDOME X9 Plus DSP Amplifier Bluetooth 5.1 channel 31 band EQ tuning audio processing amplifier stereo subwoofers car audio|Multichannel Amplifiers| | - AliExpress

Anyone knows something about it?

Schematics, specifications, etc...

thanks

I want to buy 3.3uf/100v and 4.7uf/100v, for the speaker XO

Genesis began as "'horn removal' or: deconstructing an A5/A7/828? " on the AUB.
'horn removal' or: deconstructing an A5/A7/828?

Simply put, You can get close, but no it's not practically possible to save both the horn flare and the cabinet.

Advantage: Cabinet

The 828's top and sides are 5/8" paperboard, and so once gutted they are not very good except to me as square starting point with ok enough cosmetics.

So we concentrated on salvaging the baffle (I barely do straight lines, let alone new circles) to mount a GPA 416-8C in a reasonably rigid ~12 ft3 ish sealed box - for about half the 416 spec'd Vas (iirc).

enter: Voice of the Futon MKI

- Innards were gutted save for the corner blocks left in place.
- slanted horn board removal leaves dado'd slots visible in the front, these are filled.
- existing front face was reinforced, extended with wood support pieces salvaged from a futon. This makes a continuous seat for the full-length removable front baffle.
- Top and Bottom are reinforced with 3/4 ply (good stuff), sides are 3/4 (probably flooring ply). Having left the corner blocks intact forced cutting these into jigsaw shapes: boo.
All additions screwed (probably too many) and glued with generous application of PL Premium, such that we're probably approaching constrained layer dampening of a sort.

- rear panel seat was given an additional insert step (pine) for better sealing, better rear panel screw bite.
- rear panel (not paperboard) 2x4 is removed (paucity of glue, popped right off!) and was glued and screwed with the nicer (some sort of hardwood) pre-finished pieces from the futon

The front panel/baffle is mocked up, i.e. screwed but not glued yet, as I want to leave it open for modification or revision for now. Front panel screw pattern matches the rear for interchangeability.

Finally, steel from victim futon #2 was added to the exterior face of the front panel for rigidity and reinforcement. Attached from the rear, it joins the baffle with the filler panel.

Unfortunately, I've not yet been able to remove the baffle without some unsightly damage to the exterior face. along the top edge. And note that the opening is offset. This forces orientation as seen for woofer clearance with the cabinet's panel seat.

The paint scheme is 'Accidental Mondrian'.


Next up... Voice of the Futon MKII with EF styling package!

Hello, I was wanting to know if anyone can Identify these vintage tube monoblock amplifiers - they use 6973 , 7199, and 5u4 Tubes ..... Thanks!

I'm not sure if it's still the same as original or been modified inside the chass ..

Have the option to buy one of these for cheap but can't find any information on the specs, was wondering if anyone had any idea about them/had any insight into whether this is a good amplifier (for use on small PAs for smallish indoor parties)

Hi Guys,

I was wondering if there were any examples or literature of DIYers creating their own headless DSP PC. I am building a 2 way speaker and want to implement a digital XO on it.

Has anyone created a small PC whose only job is to act like a Digital XO and apply DSP and FIR filters to all sounds coming to it? Should this XO PC run Linux or Windows? Can this XO PC be connected to a normal work PC, MacBook and receive all sounds from them, like YouTube, Foobar, Video Games etc?

Possible Chain: Windows PC/MacBook to DSP XO PC to 4 Channel DAC to 4 Amp Modules to Tweeters and Woofers

I’ve been reading a lot of great work done in the past few years by some genius members of this community, hoping someone can point me to some data to help me out.

Thanks for your time!

I'm repairing this amp and the psu driver transistors are blown the original instaled was a1266,(the service manual saids a1268 for the PSU driver transistors) what do you think about replace this with a1023?..... I have in hand a1023 , if this is not a good idea i could order a1266.
I asked about this because i have repaired another class d amps and some of them use in their psu a1023 transistors as transistor drivers.
Thank you

Member 6L6 and I were amusing ourselves listening to the SR71 "Los Angeles Speed Check" audiotape, when I realized that a teeny fragment of it sounded, to me anyway, just a little questionable.

The SR71 pilot casually says he was directly over Tucson AZ and could see the skyline of Los Angeles CA out the window. Which seemed, um, improbable.

So I hired an 11th grader to work out the trigonometry of the situation, and make a plot of (distance to the horizon) versus (flying altitude). Result is below.

To my surprise, Google Maps says there are 484 miles of Interstate road (which is certainly NOT a perfect straight line) from Tucson to Los Angeles. While the plot below says the horizon is about 500 miles away when you're flying at a comfortable spyplane altitude of 16 miles. So it's quite possible. Golly!

Note: earth is assumed to be a sphere of diameter 7900 mi.

_

Due to a WS upgrade and being skint I'm reluctantly selling two signal generators. The first is a type H1 - 15hz - 50khz, 0 - 20v + 600 ohm OP Z, sine and square wave. I recently calibrated it and fitted a new 6SN7 valve as well as replacing all coupling caps and electrolytics I think. A schematic is available online.
It's easy to work on, IE fix and has been my main sig gen for testing amplifiers, transformers etc for years. Only thing wrong with it is a non working mains on switch, I just SW it on at the plug.

Asking £20 (worth that for the valves and caps), a courier would be £8 approx within the UK.

Also have an Advance Type 81A, 15hz - 200khz, 0 - 25v, OP Z 600 ohm, sinewave only has a balanced OP, very usefull for driving valve push pull output stages. It has two attenuators in dB and volts. Recently replaced main smoothing caps and gave it a check over. It has a damaged meter but works fine. It comes with a hard to find manual, schematic and extensive paperwork covering past work done.

Asking £30 courier £8 approx within the UK. If interested in either , drop us a PM, Andy.

Sold

Hello all

I hope I can ask for some guidance in my attempt to find and repair the fault of this amp. Quickly explained - This is probably not something everyone finds worth repairing, but this amp belonged to my late father so it has some sentimental value. My electronics skills are limited but not hopeless. That is to say, I have some education from earlier and have built some stuff over the years, but I lack the real experience acheved by messing with this stuff on a weekly basis

This is the situation:
- Amp was used by me for a few years then the speaker relays started acting
up. Stored it a few years and then pulled it out and replaced the relays last month.
- Got hold of the manual to check the biasing, witch was slightly off in class A/B, and far off in class A
- Adjusted bias in A/B to spec (50mA/18mV). Could not reach correct bias in class A (500mA/180mV). Adjusted to about 90mV to even both channels
- Amp vorked on low volume for a couple of hours then died. Glass fuse 3,15A on AC mains side was gone
- Replaced fuse and tried again only in class A/B, wich worked on low levels but amp triggered fault mode if volume was increased, but no blown fuse
- I have now done some measurements, mostly voltages and there is a few odd things going on

1. No DC on speaker terminals, witch is a good thing I presume
2. B+ and - seems good, if not a volt or so too high
3. Class A is stated to drop B+ to 24,9V witch is not happening
4. Class A switch circuit is working in terms of activating the opto-couplers
5. Some small voltages seems off at the input side

I'm wondering if the lower voltage of b+/- in class A stated on schematic is supposed to happen just by switching over to class A, and if so is this the circuitry pulling down the voltage, or is the feed lowered? The measurements are equal on both L and R

Schematics are power amp board only, but I have the rest if needed

I found some parts from HEISENER. Are these guys trustworthy?

I picked up a non working RX-V2400 for basically free. Unit did not power up or do anything. No relay clicks no display nothing. I assumed its likely in the standby power board so checked some components, see attached schematic of this board. Transistor Q4 and diode D11 were shot. Replaced them and unit powered up and appeared to be back from the dead, seemed ok and no error codes displayed. Did a few more power cycles then just left in on for few min. Shortly thereafter heard a click and went dead again 🙁

Im going through the standby board again and can't find anything shorted or not otherwise bad. I have 11volts on the S9 pin but only a few milivolts on the PDD pin. So based on the attached circuit, is PDD voltage going out from the standby board or does this voltage come into the standby board?

I traced the S9 to the function board where it goes through a regulator and I have the required 5.8volts leaving the regulator. Again on the function board PDD voltage is nil but again not sure where this should be coming from.

Any help appreciated!

Dear DIYers,

I have transformer from Marantz PM-5. Amp does not exist anymore, but transformer can be good donation to my new project.

Unfortunatelly - cannot find explanation of any wire. There are (I think so) 5 secondary windings, one primary. On hifi engine - manual is OK, but no color explanation which can be navigation what is what.

Perhaps here you can help me. I will measures all values, but need only primary detection.

On transformer are two labels:
TS1961402-0 and ETP96HS1A

Regards, thank you,

Boris

So a pair of these have come into my possession this evening by way of a house clearance.

They are Pm6c Lowther drivers in home made horn enclosures.





The foam surrounds are shot as you can see but I am thinking of getting them repaired. Are they repairable or not? If so how and where would you guys recommend?

I’m in the uk.

Matt

I would like to know the formula to calculate the 'tractrix revisited' curve, thank you for your help.

Hello,


I am looking for Creek 5350 PCB layout or photo from bottom PCB side.
Especially for output relays section.


Thanks.


Best regards,
Tadas

Hi everyone,
I'm going to build Ska amps and I know there is the public schematic of GB-150D. But I searched for the GB-300 and couldn't find any. Could somebody help me whit that?

Hello.I want to add aclipping indicator to my amplifier.It uses +-45.5V rails.

Any suggestions?

Hello,

I would like to built this model:
Ellipticor-3
but the price of the speaker...

What I like on this project is very well documented. Just coy past and you have something and in term of design it's totally WAF.
I don't want to make a new project from scratch, if you have some idea.

Regards

The power supply drivers are marked

M6
L6

And some other transistors marked G1

Does anyone know what the part number is for these ?

Hi, I purchase some years ago the uTracer, a tube tester kit, from dos4ever.com, this circuit is very useful but I'd like to add a voltmeter an amperometer at the heater circuit.
There's someone know this Kit, and if yes, has does this improvement add a voltmeter?
Thanks

Sergio.

So, I'm having a problem with the definition of Vas.

I've read somewhere that Vas is the volume of air that, when compressed down to 1 m³, exerts the same force as the speaker suspension.

So I'd imagine the speaker suspension is also pushing it back too due to the displacement (the same one that compressed the air), and the two forces are equal, both pushing it back.

The problem with that is that, considering isothermal compression at least, the initial volume doesn't matter: there are only two volumes where the suspension and the force caused by pressure difference will be equal, one being the initial volume itself (as both will be zero) and the other one being a fixed value. So Vas could be literally anything, the final volume would be the same, and it would only be 1 m³ for some combinations of suspension stiffness and cone area.

I considered adiabatic compression too (which makes much more physical sense), and then the initial volume does matter and it's possible to find a "Vas", but the values I found were nonsensical.

But then I went for another interpretation: The volume of a sealed box where the air would behave as spring of constant K similar to that of the speaker suspension.

Considering adiabatic compression and expansion, and that the pressure in the outside of the cone is constant (a good approximation in most cases, as the variation of pressure inside is much greater than the variation outside), the force caused by the pressure difference is:

F = P_atm·A·{1-[V/(V±A·x)]^1.4}

Where x is the displacement, V the volume, A the frontal area of the cone, P_atm the atmospheric pressure and 1.4 the adiabatic index of air. Using SI units, the force will be in newtons. The symbol ± was used because it will depend if it's an expansion or compression.

Doing a Taylor expansion of the term [V/(V-A·x)]^1.4 near x=0, we can reduce everything to a spring-like force of:

F = -1.4·P_atm·A²·x/V

Where the spring constant would be 1.4·P_atm·A²/V

That approximation is very good for small x and large volumes, which is mostly the case for speakers, as the volume they displace is very small compared to the enclosure volume.

That interpretation gives more reasonable Vas results. For example, a 20 cm (effective cone diameter) speaker with a 400 N/m spring constant suspension would have a Vas of 0.35 m³ or 350 liters (considering P_atm = 101325 Pa). This is a speaker that would lower 25 mm if you put a 1 kg weight over it.

Is that the correct meaning of Vas?

I have 3 video sources feeding to my main audio system, the cable box, Blu Ray play and a 4K firestick. The TV is a cheapie Spectre 40" with no digital sound output. I want to feed the video sourced audio to my analogue sound system, stereo only. Anyone have information on the quality of the DAC in this decoder?
4K HDMI 5.1 Audio Decoder Bluetooth 5.0 Lossless Player USB Sound Card Version | eBay


I do not need a home theater 5.1 channel decoder. I want the HDMI switching and DAC. Currently, I have to use 3 pieces for that function.
1. A HDMI 3-in/1-out switch.
2. A HDMI input to I2S output converter
3. A ES9038Q2M DAC
It works ok, but looks messy.

Greetings.
I am shopping for replacement parts for this amplifier, I have Mr. Babin's repair tutorial, and am an experienced tech.
The first question I have is about the two large filter caps in said amp.
One is bulged and the other is not.
I intend to replace them both, along with a lot of other parts in here.
The max height with bottom cover installed is ~35mm.
Is this a suitable replacement?
Thanks for the help, and I will cover this repair completely in this thread for the next guy/gal to use...😀

paul

Hello,

I'm fairly new to speaker amplifiers but I understand the different classes (i.e.: Class A, Class AB, Class D, etc), but how would I identify the class of an amplifier, for instance if I was buying an amplifier online and the class was not mentioned, how could I know the class of the amp?

Thank you.

Has anyone ever built a concertina phase splitter and have the signal be perfectly split but they differed in amplitude?

Hi .

Where can found R-core Transformer in internet?
I want about 1.2KVA

thanks a Lot..
🙂

Hi,
me and my friends are trying to construct a horn speaker, with a bandwidth of 90-500 Hz. We chose to base our design on the B&C 12FW76 driver. We were surprised, that our calculations gave a compression ratio of about 1:4.88.


I used the following equations to calculate the throat area:


efficiency = Fs / (Fch * Qes)
St = efficiency * Re * density_of_air * c * Sd^2 / ((1 - efficiency) * Bl^2)


where:
St := throat area
Fch := upper cutoff frequency (500 Hz)
The other parameters are the Thiele-Small-Parameters of the driver and physical constants.



Are my equations wrong or do you think this is a reasonable compression ratio?
Can a high compression ratio damage the driver?



Thanks and have a nice day everyone.

Hi Everyone

I found and joined the other day, I’ve just upgraded the plinth on my Rega P3 and found some useful information on here while I was researching various bits of info, great forum and loads of good information.

I’ve literally just finished making a new plinth out of a carbon fibre board, which has a foam core, similar construction to the high end Rega decks, however mines much thinner at only 9mm thick.

Wanted to sell😱ne pair Fostex FE 167e

Two hardly used, almost like new in bass reflex test box and are spares for the other two that are in a closed box but are used with low power

Due to living in New Zealand it would be best to ship only the drivers.

Needing to downsize, moving to smaller place, too many speakers. Originally pruchased to make a metronome but it did not agree with our living space.

Have original boxes for two, will need to find some suitable boxes for the other two.

Offers wanted.

edit: No longer available.

Apologies if this has been covered, did not find it in search.

What is the proper way to add LC filtering to a voltage doubler? I have attached a sketch to show what I mean.

For the case where EITHER the Vdc or 2Vdc legs of the doubler will be used (shown as switch selectable), is (1) or (2) the correct method? Or is there another preferred option?

For the case where BOTH the Vdc and 2Vdc legs will be used (current draw simultaneous), is (1) or (2) the correct method? Or is there another preferred option?

TIA

Does anyone know of a setup for the UPV that makes testing compression amplifiers and graphing the ballistics of the attack and decay/recovery times possible?

When I was researching the UPV for purchase last month, I ran across some article about testing compression amplifiers. Silly me, I did not download or save the article and now I can't find it. The article showed some screen shots and talked about using the UPV to test the response times of compression amplifiers. Where is that article?

If anyone knows of a setup file, that would be terrific.

Hi,
I have a Rotel RC 1080 preamp going into a Quad 606 preamp

Here is the Rotel RC-1090





Quad 606 power amp



Quad 606 Power Amplifier Specification
Power Output: 140 watts per channel (8 ohms)
Distortion: < 0.01%
Input Sensitivity: 500mV
Input Impedence: 20Kohm
Crosstalk: -100db (100hz), -85db (1 khz) and -65db (10khz)
Hum and Noise: 105db
Voltage Rating : 220-200V AC (110-120V via simple power board modification)
Dimensions (WxHxD): 321 x 140 x238 (mm)
Weight: 12kg

The preamp out is 1v and the power amp input is 500mv

What level attenuator would I need to buy to match the preamp to the power amp
-10db or -20db or some other figure?

Thanks

Lee

Musical Fidelity X-Cite

Hi everyone.

I’m looking for a pair of musical fidelity x cite blocks to stack my x units, but their as rare as hens teeth 😆. I was wondering if anyone had sizes, dimensions, for these, I could try and make something that works myself.

Thanks for all your help.

I want to improve the speaker setup for a friend of mine who is just getting into hifi, but his room is far from optimal and I need your help. It's L-shaped and has two windows.
Dimensions of the part of the L, in which I can move the speakers arround are 2.5x3x4m (HxWxD) and the dimensions of the other L-part are 2.5x2.6x4.9 (HxWxD). The two widths come together to form the long part of the "L" if that makes sense. The two windows are both on that long wall -one sadly on the 3m part of the wall behind where the speakers are now.
UnfortunatelyI forgot to take some pictures of the room when I was there, but I made a quick sketch of the room in a homedesign software I used for my own house a few years ago -I marked all possible speaker positions with X's. Hopefully that's enough. I'm thinking about placing the speakers infront of the large bookshelf on the 4m wall.



Please help me. I would greatly appreciate it🙂

I have to pare down my stable of amps.

This J2 is factory stock with two pairs of SemiSouth JFETs ( 1 pair per channel).
There is a minor nick on the top of each heatsink, but hardly noticeable. Also some scratches on the bottom, (not from me,) I am not the original owner.
They list for $4000 new, so a good time to buy the J2 and save a few bucks. It is very smooth sounding, very detailed and produces 25 watts into 8 ohms in a single ended amp with both balanced and single inputs.

I will sell this one for $2100 shipped FedEx in the lower 48 states plus PayPal fees. Sold!

Rush

Hi, I'm building a 3-way speaker system. Currently in the process of trial and error about the polarity. Actually, the crossover networks I used were taken from commercial speakers. There's a problem that I'm going to discuss for the following.

The original marks of polarity on crossover were as follows:

Tweeter: -
Midrange: +
Woofer: +

After having wired as original, I felt the sound didn't satisfy me, so I tried to swap the polarity of drivers in different ways. I found the sound of the high region right to my ears when tweeter and midrange were wired with the same polarity. And the low range right to my ears when woofer and midrange were in opposite polarity. And another result I found was the tweeter must be wired at + polarity, don't know the reasons why it's different from wiring at - too.

In brief, the configuration that makes the sound best to my ears was:

Tweeter: +
Midrange: +
Woofer: -

The question is I'm concerned about wiring woofer in - (negative) polarity as I have never seen any commercial speakers wire their woofer as such before. So, could anyone please suggest me the disadvantage of this wiring configuration? I'm afraid the problems may come later, such as the voice coil former hit with the magnet due to reversing its moving direction or anything else. Please suggest to me. Thank you in advance.

I’m just curious as to what you guys think caused these zobel networks to fail like they did.

I’m thinking a short in the speaker wires. All 4 channels have been zapped.

David

I'm very interested in optimisation of a Windows based HTPC. I have an XPC with the following specifications.

Windows 7 32-bit.
Intel i5
4Gb RAM
AMD HD6450
128 Gb SSD
1Tb HD

This system is designed for low noise and low power consumption. It occurs to me that the standard configuration of Windows is unsuitable for the unit's purpose. Features such as indexing, pre-fetch, super-fetch are redundant in this set-up. The only third-party software used is Firefox and Kodi. Even the Windows swap-file is a waste of resources.

I have placed the Firefox cache on a Ram-disk to aid replaying parts of streams.

Does anybody have any ideas as to any further tweaks?

Hi,

I would like to build a Linear P.S. able to deliver approximately 10A.

The output voltage should be 12V (fixed, there is no need to have a variable output voltage): this is to replace the switching P.S. of a NAS.

I am looking for a shematics of a reliable and simple P.S.: maybe a few of you have already built a similar P.S. ?

Thank you for your help,
Michel

Hi ! i have a pairs of chimera labs ace prototype by Dennis Boyle which i really liked them , currently i have 6l6 power tube and the previous owner said that i can used el34 or kt66 for them but i never try them as i don't know how to bias them, i saw there a knob on the back of each with 5 position adjustment i got no idea what that was beside the volume control on the front , so if you have them please give me some info that will be awsome ! thank and have a great day

Here's some information that some of you may find interesting.

At Pass Labs we use Bergquist Silpads for thermally conductive
insulators on TO3P (Plastic packages) but not on the TO3
packages because they tend to shear and fail with the TO3.
This is not the case with the TO3P because of the smaller single
hole and the transistor's plastic insulation around the mounting
hole.

We've been happy with the Silicone pads in this application as
they are less messy and perform nearly as well as the
traditional Mica and thermal goo. As far as I can make out,
they have lower thermal impedance than claimed. However this
is assuming a certain degree of smoothness of the metal, which
is simply the flat surface of an anodized extrusion, and has a
somewhat polished look to the finish.

More recently with the First Watt product, the heat sink has
been bead blasted to make it more spiffy, and you'd think that
the slight dullness of the surface wouldn't make a difference.

In fact it made quite a bit of difference with the silicone pads -
apparently something like another 50% thermal resistance, and
I ended up using Mica and goo. The figures I get are 1.5 deg C
per watt with mica, and 2.1 with silicone. This is obtained by
running the devices at 20 watts and measuring the temperature
of the top of the case versus the heat sink right next to the
device.

If we take the ratings of the device itself, we see internally we
can expect .83 deg/watt, and so we see that Mica and goo
end up about 1/2 the total thermal resistance. If your surface
is not flat and polished, and/or you're pushing on the power
ratings of the device, consider good old messy mica and goop.

😎

I have an extra sheet of Kerafol 'Keratherm RED' 86/82 190mm squared .25mm thick
(7.48"sq x .01thick) imported from Rapid Electronics UK


Will cut/divide into one-third(1/3) sheets which will be enough for 16 (23mm x32mm) TO-247, TO-218 insulators 16 x (1.25" x .92") or cut to suit your needs.



$25.00 - 1/3 Sheet (2.50" x 7.48" +/-.01)
FREE Shipping Lower US 48 States ONLY - International Ship at your cost

Keratherm. 32mm x 26mm, which will fit TO-247, TO-3P, TO-218, and can be cut with scissors to fit TO-220 and smaller packages. One side is smoother than the other.
10 Kerafol "Keratherm® Red" premium insulators
Model: 86/82
Format: XXXX-028 (To suit TO-247, TO-3P and TO-218)

ONLY CONUS

Hi,
How are you?

Hopefully you would give your thoughts and opinion asap...as I am in A shop and they're closing soon.

Amp: Hertz HDP4

2 compo speakers that I need to chose from:

DLS Reference RZ6.2
Impedance: 4 ohm
Power Handling: 100W rms / 150 W max / 300 W peak power
Sensitivity (1W/1m): 85 dB
Frequency Response: 50 - 22,000 Hz

Morel Tempo 6.5
Impedance: 4 ohm
Power Handling: 120W rms
Max. Power Handling: 280W
Sensitivity (2.83V/1M): 90dB
Frequency Response: 40–22,000Hz

Thank you very very much

Hi, all.
I stumbled upon a custom pair of Yamaha HS5 whose woofers were "painted" by the previous owner with gold foil. He said that since its very thin it doesn't affect any frequencies.

Would that be true?





Thanks

Any other countries do this idiotic ‘daylight savings time’ change?

Hello. I have a set of JSE in the closet.
Someone blew a tweeter and I bought a replacement years ago. The new tweeter did not fit the baffle the same way. With no router... I'm thinking find someone to repair the old one. Does anyone know who if anyone is the guru on high end tweeter repair? Thank you.

Hello everybody


A friend of mine given me a old SU-V2X. I've noticed that this amp runs very hot, even on low volume.



It was working fine until the moment it made a clic and enter into safety mode.


I had a look on the net on what could be the root cause and, to stay on the safe side, changed Q501-504.


But no, luck, the problem is somewhere else.


So i did check volatges ou the STK2038 and got strange results


Pin 12 gives 31,4V (supposed to be 1.8), pin 14 : 34.3 (suppesod to be 0) and pin 16, 35.2V (suppsed to be 1.8). All other are according to service manual.


I suppose that the safety feature is detcting this values.
Now, what could be the root cause ? Can you help ?




Any advices are welcome.


JM

I simulated an FLH driven by a couple of dynamic drivers in series. Please let me know your comments and opinions.
Thank you.

I don't know what fiberglass looks like.
So I'm guessing. Is it fiberglass?(see photo)
this cloth is from cheap school/travel bag.

Hello, in my SE EL34 amplifier I have a pretty flat frequency response (within +/- 0.5dB +20Hz-20KHz, measured) and with full GNFB, I reach a minimum of 0.15% THD% at 1KHz @1W on 8.2 resistor.

But if I measure THD% at 50 or 100HZ, distortion rises to 1.5% @1W on 8.2 resistor. Why?

I don't understand if it is incorrect measurement or it is normal, or bad O.T. or something else.
Thanks

Here is a very nice pair of Japanese Tamradio Tamura Single Ended Transformers from the sixties. These sound fantastic and have 8 and 600 ohm secondaries. The primary is 5K and 60 ma.

I have used these before in amps and they sound and work great! These are much better that modern equivilents.

$130 plus shipping. I am in Vienna, Austria.

Paypal friends and family please or add 4% for fees.

Please feel free to ask questions.

Thanks! -Mac

I was given a Bush subwoofer from S21192. The unit had a 5" driver in a cabinet measuring 20cm x 20cm x 25cm. I replaced the driver with a 6.5" unit from an Acoustic Solutions AV-120.

Unfortunately, I do have the specifications for either drive unit other than the Acoustic Solutions AV-120 bottoms out at 48hz in a floor-standing cabinet.

The results are okay but the bass ain't going to trouble the neighbours. Because the cabinet is so small would I be better off removing the port and converting a sealed enclosure?

Or should I discard the port in favour of 2 x 4" passive radiators?

Hello and thanks for any assistance! I am in Mexico and have built a mini golf / bbar concept. I realized my sound system was lacking and hit Ebay after doing some research. Well I did not do enough research and I do not want to blow the equiptmet I have purchased. Here is what I have:

Mixer:
Pyle pmxu83bt
AMPS:
tpro LZ10k 10000 watt
3065 @ 2ohm, 2125@4ohm, 1350@8ohm
Tpro Ax3000 3000 watt -550@4ohm, 800@2ohm
Monoprice 8ohm 150 watt x 2 rms
SPEAKERS:
2 ROCKVILLE 15.24 3WAY PASSIVE 4 OHM 3000 PEAK - 1500 RMS EACH.
2 ROCKVILLE 15IN PASSIVE SUBS 800 WATT 400 WATT RMS EACH - 4 OHM
2 ROCKVILLE - KPS 12 - 3 WAY - 8 OHM - 200 WATT RMS EACH

ADDITIONAL EQUIPTMENT:
BEHRINGER SUPER-X PRO
TPRO RACK POWERSUPLY
HERCULES DJ CONTROL
AND MORE CABLES THAN I NEED FOR SURE.

WHAT DO I NEED?

HOW DO I SET IT UP?

I DO NOT MIND PURCHASING OTHER EQUIPTMENT IE AMPS
Hello and thanks for any assistance! I am in Mexico and have built a mini golf / bbar concept. I realized my sound system was lacking and hit Ebay after doing some research. Well I did not do enough research and I do not want to blow the equiptmet I have purchased. Here is what I have:

Mixer:
Pyle pmxu83bt
AMPS:
tpro LZ10k 10000 watt
3065 @ 2ohm, 2125@4ohm, 1350@8ohm
Tpro Ax3000 3000 watt -550@4ohm, 800@2ohm
Monoprice 8ohm 150 watt x 2 rms
SPEAKERS:
2 ROCKVILLE 15.24 3WAY PASSIVE 4 OHM 3000 PEAK - 1500 RMS EACH.
2 ROCKVILLE 15IN PASSIVE SUBS 800 WATT 400 WATT RMS EACH - 4 OHM
2 ROCKVILLE - KPS 12 - 3 WAY - 8 OHM - 200 WATT RMS EACH

Additional equiptment:
BEHRINGER SUPER-X PRO
TPRO RACK POWERSUPLY
HERCULES DJ CONTROL
Tons of cables…
Question?
What do I need?
How do I set it up?
Notes:
Completely open to the fact that I should have done this prior to purchasing, and may need additional or replacement equiptment now. Just need to know what to buy. Feel free to let me have it, as I definitely deserve it!
Sound area is large and open. Think beach bar.
I do have my 18th hole which is a 12 ft x 12ft cement pyramid that is dying to be a huge sub cabinet some day soon.
Any assistance will be gladly repayed in full during your next trip to Costa Maya Mexico. Drinks on me for sure!
HELP!
Poco Loco's
Mahahual, Mxll

Hi All,

I have been looking at some cheap 2nd hand transformers on an auction site, and I am left a little confused about the voltage ratings on center-tapped secondaries.

Is there a clear and consistent way the secondary voltage is rated?

Exapmle:

Triad R-23J transformer with the spec printed on the end-bell:
250V @ 22mA Center Tap

I would assume this means that the transformer is 125v-0-125v

But the seller claims it is 250v-0-250v.


Any thoughts on this? Were there historically different ways the secondary rating was expressed?

Thanks!

regards,
John

For the fun of reading on vintage stuff ... does anyone have a service manual or just schematics for Sony's first Class-d amp TA-N88 (running 500 kHz! and with SMPS .... 😀 )

I can only find this very high level schematic
http://toragi.cqpub.co.jp/Portals/0/backnumber/2008/03/p130-131.pdf

Thanks in advance
Baldin 🙂

Hey diyAudio!

I recently purchased a douk audio 6N2/EL34 tube amp kit to dip my toes in the world of tube power amplifiers. It arrived, and I built the kit, however there was absolutely no sound from either of the output transformers. I (probably retrospectively should have looked through the schematic and tested the PCB, but waiting nearly a month for shipping and my eagerness got the better of me). When I did sit down to crunch the schematic, it seems like there are some unusual things happening around the power stage for a single ended amp (in comparison to the other SE EL34 schematics I was referencing). I was hoping you good folks could take a look and see if there are any major errors in the design of this. I tested all of the resistors and capacitors before building the PCB and they were in spec. Just wanted to verify that there were no design errors before I went ahead and bought some replacement tubes.


Quick note: on the schematic, I have written in pen what connections to the tube sockets the PCB traces had using a multimeter set to continuity, but comparing it to a normal EL34 data sheet it looks like the socket may not be wired correctly.


Thanks in advance!

From audio express magazine September 2019

Attachment replaced with the link below:
AppNote: Loudspeaker Electroacoustic Measurements - Audio Precision