I want to implement something akin to what Magnepan has suggested in the following:

Magnepan

No place for a center channel speaker?

The photo below is of a demonstration in a hotel during a Consumer Electronic Show. The MC1s immediately flanking the on-wall video monitor provide a dual center channel array which can outperform a single center channel speaker.
A pair of our on-wall speakers achieves a center channel image in the same manner as a stereo system achieves a center image. By angling the speakers approximately 30 degrees to the wall, the center channel speaker on the left of the video monitor is on-axis with the viewer off to the right--- and consequently is louder than the center channel speaker on the right of the monitor (which is closer to the viewer). This "pulls" the audio image to the left and keeps the dialog centered on the screen better than point source speakers. It also raises the center channel image to the same height as the screen....

Click to expand...

See attached image from the Magnepan site will give you the idea.


I have 4 DML speaker panels to use in the following configuration:


The LG OLED TV only uses a single digital source (an Apple TV).
No subs & no surround needed in this application.
I don't want an AV receiver with lots of functionality I'll never use.
AV separates seem overkill.

The first of the attached images shows:


Can this work?

I think I could use the DDRC-24's DSP to make a "synthetic" center channel output that would work fine for my application. The DDRC-24's DSP probably has a number of ways to do this.

I would plan to use a DDRC-24 and a pair of ICEpower 50ASX2SE stereo amps (2X50W).

I've used similar amps with DMLs in the past. Great combination.

I don't need world class center channel. I just want to hear the dialog and believe that the DMLs will excel in such a configuration.

So, would this work?
Thoughts and guidance appreciated.

Hi I want to mount my new Crow XLI 800 amp next to my chair on wall in a corner of my lounge. It is for powering my subwoofers.

I want the front face of the amp facing the ceiling and I will build a box around it to do this.

Is this ok for amp as it was never designed to go face up? How much space for airflow should I leave around it in the box?
Tim

Dayton APA150 AMP issues, only turns on when I physically heat it up w/ a dryer!

Alright so the stereo amp I have been using to power a pair of bookshelf speakers connected to my PC have recently starting shutting down on me. I can get it kicked into ON mode if I heat it up with a dryer, however, if the room gets too cold, I again have to take out the dryer.

I made a very lengthy post over at the EEVblog asking for help and even replaced what we thought might be bad diode to no avail, same problem persists. I will leave a link so you may view my post and pictures. OPA150 Stereo AMP issues, only turns on when I physically heat it up w/ a dryer! - Page 1

I guess what I'm now trying to do is pretty much Frankenstein this thing and that's where I could use some help. Unless someone can review the above post and knows a way around to keeping the amp on constantly, that'd be awesome.

I have been looking at Amp boards to replace the current boards that are in the Dayton amp, basically just use the case (which is nice), connections (RCA, Speaker etc).
I've heard great good deal about some Class D amps based on TPA3255 such as Amplifier Board - AIYIMA B2D2205 - TPA3255 | 4 Channel 315W Power Ampl It's two more channels than I need but I suppose has expandability in future?
That board requires a DC24-48V, I thought about getting this Amplifier Board - AIYIMA B2D1877 | Schottky Rectifier Filter Power Boa and just using the 28.4V toroidal transformer that's already in the Dayton and that takes care of my power supply.



But this is bit going over what I really want to spend on a Frankenstein build. Then I came to thinking that the rectifier 28vAC to 28vDC part of the Dayton amp works, why can't I just wack off the rest of the amp and keep just the rectifier part that gives out 28V DC and hook up a 2 channel board to it.

Do any of the electrical folks know where I would tap this DC power? The rectifier setup is not that complicated, Its AC-0-AC into a Rectron RS 802 single phase bridge rectifier rated at 100V, 8Amps and then into a pair of 5000uf caps for smoothing I guess usually from there it would go into a voltage regulator but that's where I got lost. Do these boards like the one I linked have their own voltage regulators? I'm pretty sure I can just tap the power somewhere after the caps.

given I have the power supply issue taken care of, is there any other 2-Channel boards you guys recommend?

Or should I just get Amplifier - AIYIMA A07 - TPA3255 | 2.0 Channel | 300Wx2 | HiFi and call it a day? Are these good?

I'm sorry my post is all over the place but I'm just tired of keep using the hair dryer to keep my amp running and I don't feel like spending $180 for another one. I've look at AudioSource amps as well but I dont like their form factor, I have no space on my desk for it.

Thanks for reading my nonsensical post, let me know if you guys have questions or ideas.

What about TPA3255 2x260W 2Ch Class D Audio Amplifier|Amplifier| - AliExpress paired with https://www.aliexpress.com/item/32880495843.html?spm=a2g0s.9042311.0.0.129c4c4d4HAXzH which I can connect to the transformer already in the amp. Would this work?
Any idea on how I can control volume on the TPA3255 Amp? I'm using a TOPPING D10 DAC and would like a physical knob and not rely on my computer for volume.

I came across some 3/4 furniture grade plywood, which I need to extend the length of 4 pieces, by butt-joint glueing a 3/4" square hardwood stick to the edges at either end. I have a large bottle of Elmer's yellow -

I'm planning on staining and finishing the top surface and I know some glue will squeeze out of the joint. Obviously I dont want that to interfere with the stain. Do I just wipe off the excess? With a water soaked rag? Do I just let it dry and no problem after sanding? Scrape it off partially dried?

Stain before gluing?

How should I handle this? BTW, I've got one shot to get it right - and not have it look like crap for all my effort when done. Thanks!

This TIP35C is from Ali Express. Is this right size of die for TIP35C specs for 100V 25A power transistor?

Can you folks please give me a hand finding some info on these rarities? The best I could find by googling was this table, which has info on Siemens Da.

Hello everyone,

Yet another fault in my system.....yawn.

I have a 211 power amp that has become duller/rolled off and when my brother came to visit now covid restrictions are lifted he commented how recessed and dull it sounded. He is into his AV and has a microphone connected to REW software and we compared 3 amplifier set ups and confirmed the source of the roll of was my 211 amp, by deduction. Same DAC, same leads from DAC to amp, and same speakers and speaker cables. Only change the amplifier, we also had a measurement from a friends system (same speakers, different room) this is the orange plot see below.

So the question is what could change to make an amplifier roll off this much, we are sure it never used to be rolled off (but don't have historical measurements) It's 18 years old and has been used in numerous systems at points and has never before sounded dull. It did not seem to change in one event, it's just gotten that way over the last few months I think, and I had shame on me, not really noticed by how much

Speakers in all plots are Klipsch Heresy III

First plot:
Green my old Denon UDM-31
Blue 211+ ARC SP8 preamp
Pink 211 into directly no preamp

second plot:
Green, same as above Denon UDM31
Orange, ARCSP10 + ARC D125
red, blues, all 211 amp, also with different 211 valve sets (V4TC GE)

so deduction is the 211 is rolling off, and the general question is what might change that could effect this amount of HF roll off, over time?

The sound is still good, and no other obvious fault.

The 211 Valve is drive by a 6C45 valve and an interstage transformer and the power supply is valve rectified 5U4GB, so I am getting new versions of these valves, but wondering what else to consider?

I am going to try and suss out the circuit, but don't have a diagram.

Any general thoughts of what could shift to result in roll off?

Thanks,

Hello! please if anyone knows or has more data about this electronic tube: 4Ц14C, I can't find anything about it, thank you!

Hi. I would like convert my Sony CD3000 to make possible use the Sennheiser HD650 cables I own. Whe can i find these retangle sockets?

I want to find any octal base replacement for soviet 6S19P 9-pin regulator tube for tube voltage stabiliser.

6S19P parameters:
http://www.nj7p.org/Tubes/PDFs/Frank/113-Soviet/6S19P.pdf
f = 6.3V 1.0A
Ip = 95 mA cont, 140mA max
Vfk = 250V max
Va cold = 500V max

I want filament with 6.3V 1-1.2A, maybe 1.5A, not 2A as I saw for several types of octal triodes. Current 70 mA minimum.
Any octal analogs for this?

Hi all,

I would to know what kind of diode is this with code 5C. Picture is attached for your kind reference. Thanks in advance.

I need a few KTC-3200GR NPN transistors, 2 at least or more if I need to match them.
Preferably from EU.

Anyone has some of those laying around?

After it went silent I replaced the 5AR4, the 3 wire wound resistors, the 4x475 can-cap and did the UF4007 tweak. Fired it up and it sounds great but...all the voltage measurements are high. Where it should read 430V I'm getting over 500, with other lower voltage areas similarly high.
I checked all the resistors, and besides most being ancient, all test good.
Before I sacrifice another can-cap or the new quad of EL84Ms I could sure use some advice.
Thanks in advance for any help
Karl

Hi all,

I have started fiddling around with my VPI classic 3 + SDS.
I don't have extensive experience on motors so my apologies in advance.

The VPI uses hurst 300RPM AC motor. The outer edge of the pulley of the motor is only 3mm away from the outer edge of the platter, which makes it for an easy modification to have the pulley come in contact with the platter for RIM drive.
Pulley has a diameter of 50mm and I found that it is easy to find a proper O-Ring that will fit the application.

Nevertheless I have the issue that platter with such a pulley will spin at 45RPM and to adjust it down to 33 1/3 RPM, the SDS would have to go down to 45Hz.
Unfortunately minimum frequency for SDS is 52Hz which is a no go. Also I don't know if the motor would still operate properly at such a low frequency anyway.


My question is: is this motor suitable for Rim drive?
Can any expert here please recommend me a top quality AC motor that I can use to replace my original Hurst (no cost object) using 50mm pulley?
Or maybe for this application another type of motor i.e. DC or EC be more suitable?
For AC motors I also have read that best solution is having two sine waves with phase control, such as mark Kelly controller.
Unfortunately it seems that this controller is no longer available. Is there anything similar to this available for purchase?

Thank you all for the attention paid.

One friend needs a pair of scan speak 18w8531g00
If there is any pair over there, please, let me know.

Did anyone try 6sn7(6n8) tubes at 3ma anode current supplied in the region of 200...400v ? I built sone output transformers that have the posibility to be wired for 13k load while not able to run at more than 13ma so i might need some 12sn7 tube run at 3...4ma.i can also wire them for 4 times that impedance, about 47k...

Dear Members,
Just like to share my latest construction.
It’s a preamplifier (line level), based on the small WE417A valve (one each channel), using output transformers. The final result is shown on the attached picture (hope you enjoy it).
List of inside goodies:
- One input resistor from Shinkoh.
- Volume Pot from TKD.
- Balance Pot from Alps on its Black Beauty version (my new old stock).
- Input control from front panel through C&K switches, to relay input board.
- Input relays from Nais (TDS).
- All aluminum chassis (based on Hifi2000 parts), 20mm sides, 10mm CNC machined front.
- Stainless steel shafts for front panel knobs connection to the pots.
- 4 special polymer bearings to guide the shafts (feel is incredible).
- 2 machined connectors from shafts to pots.
- Lundahl mains transformer.
- 1 double Lundahl choque.
- 2 more choques from Hashimoto.
- 3 double Elna Cerafine 100uF/500V power supply caps.
- All power cabling Nordost single strand copper.
- 5AR4 valve rectifier.
- 2 TDO 25W resistors to lower plate voltage from 200V to 180V.
- New old stock Western Electric Valves.
- 2 Tentlabs Heater supplies.
- Hashimoto output transformers.
- Direct connection from input to 1 resistor, next to volume and balance pot, into the valve grid, and direct to Output transformers. Nothing more, just a direct connection to output connectors through the 600 ohm transformer connection.
- All signal wiring is cryo treated pure silver from Audio Consulting.
- Neutrik RCA panel connectors.
- Furutech IEC connector.
It sounds simply astonishing with these impressive Hashimotos.
Best wishes for 2011.

I'm looking for the time constants for the 78rpm RIAA curve. I can find several hundred pre-RIAA curves for 78rpm, and the 33.3rpm RIAA curve, but no luck on the 78rpm one.

TIA

Hello Chaps,

SWMBO asked me yesterday what I wanted for Xmas.
I was thinking about an ESR meter.

There are a few different ones availalbe, any recommendations please?

Thanks!

This was inspired by an analogous mechanical conundrum using springs and string:

Two simple circuits, each using 10k resistors and 10V zeners, each fed 1mA constant current - which voltage is higher, output1 or output2?

The right hand circuit is the same as the left one apart from one resistor (R5) being shorted out.


For the inspiration: The Spring Paradox - YouTube

Most people's intuition is that shorting the resistor will lower the impedance of the whole circuit.

Hey all,
Will the B&C TWB100 be a suitable driver for a cubo 18?

Nominal power handling1500 W
Continuous power handling3000 W
Specs Below

Recommended enclosure200.0 dm3 (7.06 ft3)
Recommended tuning32 Hz
Parameters
Fs33 Hz
Re3.2 Ω
Qes0.34
Qms6.23
Qts0.32
Vas181.5 dm3 (6.41 ft3)
Sd1210.0 cm2 (187.6 in2)
η₀1.8 %
Xmax12.0 mm
Xvar14.0 mm
Mms268 g
Bl22.8 Txm
Le1.64 mH
EBP97 Hz

Many thanks!

I inherited this speaker set, which has been working fine until recently: CyberAcoustics CA-3712BT.

I was playing fairly loud music for a while (1-2 hours, listening from another room), and suddenly the subwoofer cut out.
The other smaller speakers still produce sound fine.

My guess is that something overheated, and maybe even burnt out, but I'm not sure.

I opened the case, and the power transformer was very hot, as well as the heat sink that's near it (not attached, but nearby when it's assembled).

Some pictures are below.

I also noticed an electronic component attached to the heat sink, which I thought maybe was a temperature sensor - so maybe it cut itself off to avoid overheat? But even after letting it sit and cool a while, it's still not working.

I'm trying to get an idea of whether it's worth repairing or not.

Pictures: imgur listing

Questions:

• How can I verify if, in fact, this transform is burnt out? I have a multimeter, but not sure exactly what to measure.
• Is this something I could replace, if it is burnt out? I didn't see any obvious off-the-shelf parts that match it, and I'm uneasy trying to mix-n-match parts that are rated for different volts,amps. It has 2 sets of wires (2X11V - 1A - Blue/Black/Blue, 8V - 0.3A Yellow/Yellow - see pictures)
• Any other guesses what might be wrong?

Thanks for any input!

Can be yours for a song.

In glossy piano black finish. New in box.

Specs:
XTZ Sub Amp 1 - XTZ Hifi

$200 for the pair.

Looking for one of these, ideally in the UK but would consider from Europe.

This aint no revolution, however it is the SOAP Evolution .. 🙂

After some time of silence i now have tuned the SOAP preamp to a more complete version.

There was some request to have it even more simpel then the MKIII but i decided that it already was very simple (and cheap).

This version contains a full onboard PSU. Onboard trafo, Dual discrete rectifier, room for more smooting caps.
The in/out caps has switched placed for placement reason. (Out caps are generelly bigger)

Grounding has been optimized even further. 😎

This version will make installation a piece of cake with less cabling. 🙂

Testing will follow shortly.

A first glance on how it looks.. 😀



/JZ

Finally after almost a year and about a dozen designs I have a functioning prototype that is meeting my expectations.

All transistors except the EXICON double die lateral mosfets are SMD.

Photo of prototype and the simulation results, will post actual measurements later.

As the title said. The kits include a pcb, all components and fixtures plus a suitable Hammond enclosure. You'll need to find an external 24V DC power supply (50mA or more) and to drill required holes in the case panels.

Two full kits are available - for the MM version (£160) and for the MC version (£190). Prices include shipping in Europe, overseas orders add £5. Blank pcbs, partial kits and assembled pcbs are available on request.

Here is the discussion thread (and the link to the circuit diagram/description).

Enquiries and orders by email to "sales(at)ant-audio(dot)co(dot)uk"

Payments are by PayPal.

NB: the kits contain static sensitive and SMD devices - please consider that before ordering as you have to use proper anti-static precautions during the assembly (grounding wrist strip and mat, grounded soldering iron). For a kit with a fully assembled and tested board add £50 to the price.

Cheers

Alex

I am looking for a P channel mosfet for use in a class A or AB audio amp application. Quiescent Vds can be up to 100 volts with peak excursions approaching 200 volts at near zero current. Quiescent current is at or below 160 mA in class A with peaks to over 300 mA near saturation (near zero Vds). Class AB applications will see similar or lower static bias currents with peaks approaching 1 Amp, again at Vds in the 10 volt range.

The application is a vacuum tube amp with a cascode output stage involving a tube paired with a mosfet. The schematic is in post #91 here, the fet in question is the IRF9640:

https://www.diyaudio.com/forums/tubelab/340856-unset-coming-10.html

ON Semi / Fairchild does NOT seem to acknowledge secondary breakdown in their mosfet data sheets, which is real. They no longer list any mosfets for high powered audio amps on their web site. Many other companies do not show any DC curve in their SOA specs. I have tried dozens of the usual mosfets intended for SMPS use, and I have a big pile of dead ones. The Fairchild FQP9P25 is the best I have tried so far, but I have scattered a couple by driving the snot out of the amp with a guitar preamp, or having a bad ground on an interconnect and messing with it while playing music at full power. Yes, these are extreme tests, but I build my stuff to be capable of this kind of abuse.

I spent a good deal of the last year of my engineering career (2013) chasing secondary breakdown in GaN fets used in RF amps......now I'm chasing it again, or running from it.

Hello
Hard to choose when listening is not always possible [emoji16]
I have a very high quality 2A3 direct coupled amp, and want to build a corner speaker.
This to listen to Classical music (symphonic, baroque, opéra, piano and concertos....).
I am thinking about :
Altec 604 GPA
GRF type Tannoy (maybe a bit short in efficiency)
Klipschorn
TP1 London with Lowther or Alnico 215-2000 Supravox.
Some of you could share their experience with this kind of configuration and for Classical musical taste ? (Timbre, extinction, subtility, dynamics, etc....)

Just a remark : on YouTube, demos of Altec 604 are only with jazz or pop music, Tannoy mostly with classical : is that a sign ??

Julien

Maybe i should reduce a bit my coffee consumption, but hey hey, here's another thread for your DIYolic pleasure, and mine. 😛


So, let's start by the beginning:

http://www.diyaudio.com/forums/multi-way/301988-about-sound-noise-go-through-cone.html

Then, the ''no-box-is-better'' started to show up (as expected), then i tried the 18FH500 baffleless ('cause i couldnt do better tonight) and now i'm asking:

IF the produced bandwith fills my needs (80hz+ as of now)... Is any added baffle is useful/wanted, or the ''baffleless'' or ''minimalistic baffle'' is a approach worth considering ?

I'm simply thinking about reducing as possible the unwanted reflections & resonnances that i felt/heard (that comes usually from an enclosure in the 80-500hz region) and also to reduce the baffle material and size of the ''enclosure''

These drive 2 ohm loads even. They are true Gan amps. Very inexpensive. So why aren't we hearing about them?

I have a H-K TA5000 and I m running an inexpensive active sub. My rig is in a small room so I use the sub because I'm running small bookshelf speakers; I just turn the sub up enough to barely hear it and fill the bottom - I dont rattle the windows with it. This sub has a line level input connection that I m using off the tape-out on the receiver. I was going to put the sub in a new location so I unplugged it. The volume and bass response of the main speakers increased dramatically with the sub unplugged. Obviously not the best way to connect a sub to this receiver. I don't ever turn the sub up passed 1/3 volume or so. There is no chance I'm trying to drive a passive sub with this amp.

Would putting a resistor in the line going from the receiver to the sub work and would it be a good way to keep the audio signal from being pulled down by the sub? If so, where would I start with resistor values. Is there a better way to go?

Hi. I'm intrigued by a lot of the benefits of a full range and am considering diving in. I don't have a set chair in my listening space that is mine though, so would prefer something that doesn't have a laser beam sweet spot. Is the small sweet spot something that affects all full rangers, or are there designs/drivers that have wider dispersion.

So far, I've mostly been considering the Frugel Horn Mk3 with a MA Alpair driver, for no better reason than it's one of the first designs I looked into deeply (read, got obsessed with).

Hi,

As the title says my MM Stage 3 now has no audio output which has been caused by user error !

After an amp swap I`ve accidentally connected the output from the cd player to output (rec out) on the amp, so I guess it`s 2 volts across the MM`s output. Can someone advise what I`ve likely blown ?

Many thanks.

David.

Hi - I have a technical question I have not been able to find a satisfying answer for trawling the forum archives.

I am working on a parallel PCM56 NOS DAC. I have the design finished at a high level, working out some details. This is a first for me, digital design, so hoping to gain some insight from those with technical / engineering experience.

Here it goes: when it comes to the power supply for single channel DAC chips, like PCM56, is it beneficial to use separate supplies for each channel?

For instance, PCM56 requires VS+ and VS- (analog), VL+ and VL- (logic). I plan to separate these four supplies - so four supplies minimum plus the digital supply. If I were to use separate supplies for each channel, or at the very least split each supply rail at some point for L and R, the DAC would have in total eight supplies (plus digital)! As you can imagine, this is a nightmare to lay out on a board...so would be interested to know if there is a benefit.

Let me know what you think, thanks 😀

Hi I am building some speakers each with a 6.5" SB Acoustics SB17NRXC35-8 for the lower frequencies. This needs between 17 and 25 litres for a ported enclosure. I have calculated it to 22.5 litres with a 19.5 cm x 43 wide port.

I would like to ad a midrange driver the Dayton DSA115-8 4" but this needs a ported volume of 3.68 litres.

How do I add this, does it change the volume I already have calculated for the SB Acoustics 6.5" ? Does it change the port size by adding the mid range Driver??

Greetings!

I've got a TAS5630 2.1 (running at 48v) but my phone doesn't seam to have enough power on the audio output to bring the amp to it full potential.
So i'm looking around for a siutable preamp now. My question is, if it is possible to use a small amp like the TDA2822M with 2x1W or a slighly biger version with 2x5W as preamp?
I also had a look into headphone preamps but they seam to be more expensive and have less power.
Or do i need some board that is sold as preamp?
I had a look into the TAS datashet and thought the ANALOG INPUTS section is the right one. The voltage gain is 23db there. In the sure manual that gain value is described with in input voltage of about 2v. So i guess i need 2v input voltage to drive it to the max. Still i'm confused why it says that the input resistance is 33 KILO ohm - wich sonds quite high? Max input current is 342 mA btw. So how i know now if a 1W amp delivers 2v at 33 kOhm resistance or if i need a 5W amp for that? - or can't i use amps as preamps at all because there is some different functionality?

Thanks for reading, hope someone can give me a hint 😉
Cheers!

Hey guys, hope it's the right subforum.
I have this low pass filter based on NE5532 that is not working:
CIRMECH Low Pass Filter Bass Subwoofer Pre AMP Amplifier Board Single DC Power NE5532 low pass filter bass preamplifier|amplifier board|bass preamplifierlow pass - AliExpress

It is brand new, the chip is fine since I have a known working spare, and the led lights up so it gets power, but no output. Measure the voltage at the output, it's like -0.06V to -0.11V, something like that. Tried switching polarities but again no sound.

Don't have an oscilloscope to debug further. Is maybe something simple I can check, maybe a cap/resistor is broken?

Hey all,

I'm thinking about gutting my Soundboks, and trying to improve the quality of the output. It's an original kickstarter one and it's had plenty of use. Frankly I've never been super thrilled with the quality of sound, though it did get very loud.
The cabinet itself is pretty well made and I think the woofers could produce some much tighter low end if they didn't also produce a bunch of mid range as well. I also don't need it to last 2 weeks on one battery charge, So I don't need the ultra efficient amp module it currently uses. If I can get it sounding half respectable for around $100 I'll be happy to keep using it.

Standard configuration is like this,

2 - 10" Eminence 4 ohm woofers (custom made, but very close to this I think Eminence LEGEND BP102 - 10" Bass Guitar Speaker) in a dual ported enclosure

2 - Eminence 1" Super Tweeters - These ones I think Eminence APT:30 - 1" Bullet Tweeter

1 - 4x"42 watt" Soundboks branded Bluetooth amp board.

I'm thinking to keep the woofers, replace the shrill tweeters, preferably with something that rolls off closer to 1khz instead of 3.5khz then power it with a little 2.1 amp that has tone and high/low pass knobs to tune it.

Tweeters I'm thinking - Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter

then powering everything with one of these amp modules
TPS3116D2 Class D 2.1 Bluetooth 5.0 Amplifier Board 2 x 50W + 100W with Filter and Volume Controls

The only problem I have with this, is that the tweeters will have to run as stereo, I don't think I'll be able to make the amp output mono easily, at least not using bluetooth anyway.

Does anyone have any suggestions on how I might do things differently to end with a better result?

Thanks for your time and input.
Ash.

Hi would like some help or advice for my stereo. When the faceplate is attached, the unit turns on and turns off at random. I press the eject button and the unit turns on. It sometimes cycles thru the different sources if I press the eject button. All the other buttons don't respond. I tried to reset it which didn't work. I took apart the faceplate and also sprayed some electrical contact cleaner on both sides, and all of the buttons and it still didn't fix the problem. I also figured out that if you hold down the eject button while pressing the other buttoms, it will function, ie: volume with the rotary knob, and switching sources. Can anyone help me out with this?

Here's a link to a youtube video with the exact same problem:

http://www.youtube.com/watch?v=IsljBqy72xc

Recently bought a 6j1tube pre amplifier board and built up a small pre-amplifier. My question is in the directions it says to short the jumper for if your using a 12v or 18v transform. I’m completely confused and obviously a newbie and haven’t found anything online that would make me confident enough to do it myself. Could someone please help. I’m using a 12v r-core transformer

Dear all,

What is the difference between Philips CD100/00 and CD100/30? Thanks!

mike

This amplifier has no pre-amp output. It obviously has got a pre-amp and a power section its just all enclosed. Can anyone tell me please looking at it, is this a simple job were I could just tie in some RCA leads from the board to give me the option to T off after the pre amp so I can use it with a separate power amp as well?



Marantz PM6003 Integrated Amplifier, Inside - YouTube

I found an old pair of paper 12" woofers that sound great, but the cone is bending a lot and distorting the sound quite a bit. I am on a budget and am wondering if there is any way to stiffen up the cones. Could a thin layer of epoxy be put on top? What about epoxing little strips of cardboard (like from a legal pad) to the cone? Any suggestions would be appreciated. Thanks.

Hi everyone,

I'm just in the process of updating the next iteration of my enclosure in my LS430 and noticing some modelling/real world discrepancies which I'd like to get some opinions on.

First for equipment, the system is comprised of:
- Two 12" DC Audio XLs (3" 8-layer flatwound DVC option, 2200W RMS a piece, QTS = ~0.38)
- Rockford Fosgate T1500.1BDCP (regulated at 1900W/1800W/1200W at 1/2/4 ohms respectively)
- Final impedance is wired to 1-ohm
- ~200L 4th/6th order adjustable enclosure

The enclosure is built as a series BP6 with following specs and pictures below:
- Rear chamber: 55-61L (depending on port configuration)
- Front chamber: 125-131L
- Internal ports comprise of four 46cm long PVC pipes which can be capped off to modulate internal port area (~0/45/90/135/190 square centimeters of port)
- Front port is 27cm long, with 489 square centimeters of area. In front of this there is another ~10cm of effective length having an area of ~900 square centimeters where the arm-rest recesses.



Enclosure has been modeled in Hornresp taking into account all port configurations and corresponding displacements @ 1kW RMS. Overall, the response of the box with the cabin gain is close to expected as we see in the RTAs that follow.

Below are Hornresp graphs which show the five different configurations:
4 ports open vs. 3 ports open
2 ports open vs. 1 port open
1 port open vs. 0 ports open (4th order mode)




I've taking many measurements with UMIK-1 at relatively low volume (well within any limits of microphone clipping). I'm noticing an intricacy in 4th order mode as well as 1 and 2-port 6th order modes that deviates from the sims in regards to peak output. Based on modelling I'd expect it to peak harder than the next closest configurations (1-2 ports open) by ~2-4dB respectively but that does not appear to be the case. At much higher power (1000W+) I've also RTAd the vehicle with the mic outside the window (in order not clip the mic inside the vehicle) and the same discrepancy is observed.

First set of measurements are with front windows open with UMIK at headrest (probably less than <5W). Box configurations can be identified by their low-freq shelf.
Green: 4 ports
Light green: 3 ports
Orange: 2 ports
Purple: 1 port
Blue: 0 ports (4th order)


Second set of measurements are with all windows open with UMIK outside of car, ~1m away from B-pillar at same power. It's clear the car has optimal resonance mode at ~46-47Hz which is the the rough range where I'd like to target for peak SPL. The trace colors are different in this chart.
Green: 4 ports
Orange: 3 ports
Purple: 2 ports
Dark green: 1 ports
Red: 0 ports


For anybody wondering on why I want it to peak harder, it's to optimize this enclosure in these port configurations for SPL competition. I like having the modularity to switch port configurations on the fly for when I daily drive and when I want to compete. For reference before I got the UMIK, for competition I set it up as a 4th order and on the first go it did a 146.1 @ 42Hz on a Termlab at around 1kW of power. Now with the UMIK, I now have more insight into what's going on and I'm wondering if 4th order may not be optimal regard to SPL.

Was hoping to get some insight as to why this might be happening.
In terms of some factors:
- I don't believe that it's port compression as this relative behavior happens at low volumes. Furthermore, even at ~2kW there is no audible noise from the port.
- Could it be impedance being drastically difference in 4th?
- As this is done at low power I doubt I am seeing large-signal driver effects relating to BL-change vs. excursion as the drivers are barely moving when taking these measurements.
- For sealing up the ports, I am using slip-on 3" PVC test caps (very elastic). They don't leak but I do know that they are thin enough to resonate but I'm doubting this is significant.
- Could there any issues with the bracing/port supports/ports causing some tuning effect inside the box (only thing I've considered is just their displacement)?

Hi,

I'm having problems with my amp again and was hoping for a few pointers.

I started to get popping/clicking on the right channel.

I unplugged the speaker from that channel and finished my film.

When I checked it next day, both of the 6.3 fuses were blown.

Only other symptoms I can think is it occasionally used to click when powered up, but this has gone since I'm only using the left channel.

Any tips?

I'm happy to reward any advice that leads to a fix.

I'm an electrical engineer, but electronics has always been my weak point (well that and personality).

No oscilloscope, but decent multimeters.


The schematic is too large for forum upload, but I can send it to anyone.
Also if you search for rotel rb-991 technical manual it comes up in images.

this link may work

rotel rb-991 technical manual - Google Search

Hi All,

i've read about Greg ball's popular GB150 amp a few years ago...
and just recently was thinking about one again...
upon trying to go to the ska-audio site, i noticed it was gone....

greg's not doing this anymore, emailed him to confirm....

I was wondering if there any verified kits which exist on the interwebs?
all i could see was a thread for something based on the GB150...caled the tg7? on diyaudio.


i was hopping there were pre-build modules which i could take to a tech to wire up/box for me (seeing as my diy skills are still not at the mains powered level yet! )

I added a new tool to my company's inventory.
Kinda cool to see the behaviour change when moving from on axis to off axis positions ;-)

New Toy ;-) | Timo's World all around the globe

Hi Guys,

What are the recommendable Capacitors, resistors or any other parts would be recommendable to select for a best possible quality / price ration upgrade to Rotel RB-991 Power Amp. I think they where manufactures starting from 1999

The Amp uses: BHC slit-foil capacitors. It circuit employs Black Gate and Wima capacitors and Roederstein metal-film and Vishay military-grade resistors.

Also, what are the signs to look for if power amps of that age needs upgrades? although is it really necessary to upgrade 1990 + Rotel Amps, meaning would the caps and other parts lose their ability?

Thanks

Hi
I read forum for a while and notice you have expierience with Rotel .
I have 2 pieces from that Company .
Power Amp RB-980BX
And Preamp RC-995
I have aquired them few months ago and they are in working order however sometimes channel play unevenly and power amp gets very hot. I have cleaned pots and selector desoldered of the board dissmantle and cleaned as well as relays in pre.
However in order to improve on the equipment i would like to recap them as a prevention .
Basically i would like to ask you for help with capacitors selection and perhaps a suggestion as what else may need attention . Its all still original black gate. Perhaps i should just do power caps ??
Which capacitor cause problems in zobel network i read in one of your post??
Electronics is very new to me but i know how to use meter and soldering is good fun for me .
I would appreciate your help.
Love Rotel Sound and would like to preserve it.
Best of Regards .
I have both service manuals if needed.

My RB-980BX was stuck in protection mode. I checked every component on the circuit board, replaced a couple of resistors that were slightly out of spec and replaced all the smaller caps. I could not find any issues with the output transistors with my DMM or the four large caps so I left those as is. There are 4 internal fuses and they are all functional. Rail voltages are OK and transformer voltages are spot on. No obvious signs of burnt out components or damaged board from heat. Still stuck in protection. Any ideas as to what could be the problem are welcome!!!

Hi folks,

What could be the cheapest device for bode plotting in the audio range? It doesn't have to be an oscilloscope, although most devices are. I laid my eyes on the Velleman PCSU 200 first.

P.S. A simple sound card won't be enough, because I need the 200-300kHz range.

Thanks,
Alexander.

So ive built a couple sets of flat panels with canvas pictures and they sound great with a seperate sub matched with them. I am thinking about building another set for my garage shop and I have a couple questions.

1. these are just for garage work shop so not looking for perfect amazing sound but do want them to sound good cranking up the tunes while I work. I have 2 large canvas pictures that are 30x46 that i was debating suspending from ceiling down firing so as to not take up space because my walls are already covered in other stuff. Will this sound decent down firing like that? its a standard 2 car garage

2. using these very large canvas 30x46 what type and size exciter should I use? should I do two 4ohm exciters on each to pair them to 8ohm? I have a yamaha audio video receiver that im using for my computer sound in the garage that I can power these with. I think 100 watts per channel and the receiver is actually designed to be programmed and used with either 8ohm or 4ohm speakers. I can even bi amp if I need to with this receiver

Hi

I've built a number of chip and D-class. Looking for a new project with equal or greater power to the lm3886.
The only SS amp Im familiar with is the ESP P3A but it's not mentioned very often these days and last time I checked PCBs were a bit expensive.
Is this still a great amp, what else is recommended?
- ideally cheap to build
- 60-100w is plenty.
- 4/8r suitable
- Happy to build a clone or buy from China etc

Greetings,

Ohh JOY ... !!!

I bought myself a set of Tannoy K3149 speakers (Tannoys Dual Concentric 12") in mint condition. It came with 1 filter 😱 and 2 filter frontpanels 😛 .

Always wanted Tannoys for my (ever to build) home studio. Now I have this pair, I intend to do a project;

1 - Try to build my own Super Red Monitor cabinets (as close to original as doable)
2 - Design my own version to make it go way more deep, but keep it easy enough to handle.
3 - Build new filters, with the latest and greatest components (affordable prices ?)
4 - Do an active version with miniDSP and class A amps.

Challenges enough, I found a number of web-sites that contain K3149 and Super Red Monitor data, including a schema of the filter used.

To my supprize, the T&S parameters found ALL differ, and not by a margin. I use Bass Box 6 Pro, to design my cabinets (with good results) and it also contains a 12" Tannoy (SRM 12 LF), but it holds a note (caution: These parameters were measured by an unknown source (never knew that an unknown source has this type of talent...😀) and may not reflect the original specifications of the driver.). These parameters ALSO differ from the others found, but seem "More logical".

I also found the dimensions of the Super Red Monitor cabinet, 2 sets almost identical, 6 ALL differ, like internal volume between 72 and 105 liters. Doing a conversion to feet 3, AGAIN 3 differ this time. Hmmmmmm, nice little project popping up on the horizon. (or is measuring and calculating way more complex than expected? 😀

I gave it a first shot with Bass Bax 6 Pro, using the "unknown source" SRM 12 LF driver and the 2 almost identical dimension specs. Gave a result that looks very much like the specs in the Tannoy brochures I found.
Except to the reflex port, looks small on the picture (compared to the 12" driver it looks more like 50-60 mm), but comes out to be 98,8 mm diameter and 18 mm deep (at Fb 52 Hz).

I could just build these and have a listen, but my goal was to do it VERY right.

So this thread is intended to find all details and show all results, ending in designs for all interested parties (except professional builders, you can find this yourself.).

Any suggestion where to get the REAL T&S specs? to start with. Also saw that Tannoy (and almost any other company at that period) used "particle board" as building material, which we now a days call "any unkind phrase" of wood.
Start will be MDF 18 mm, end will be top grade Birch Plywood. Heavy bracing, etc.

Also noticed VERY thin cabling used, see how that effects the sound quality. These were very popular monitors way back when, change it YES / NO?

Keep you informed....

Oooh , by the way, the picture attached of the complete cabinet of course is just an example of what will be the net result of this project. Duuhhh.

Is it possible to purchase the front panel mounting brackets (the angle brackets that bolt to the inside of the front panel and the side panels) for the SlimLine chassis as a separate item?

I found the front panels and the side panels on the Modushop website, but couldn't find the mounting brackets.

Thanks.

Hi all,

I have a Mission Cyrus 2 that I would like to modify so it can be used as a power amp only, now I know that it’s preamp stage (besides the phono stage input) is passive so basically as far as I understand I only need to bypass it volume potentiometer.
But the thing is that as an integrated amp with passive preamp stage the power amp stage probably has a higher input sensitivity than an active preamp stage so I assume that if I’ll just bypass the volume pot and connect an active preamp (tube preamp in this case) to the power amp stage it will overload the Cyrus 2 power amp stage input, any suggestions for where in the input circuitry of the Cyrus 2 should I connect the external active preamp so the power amp stage won’t be overloaded by a too high of an input signal from the active preamp?
I’ll include the Cyrus 2 schematics soon.

Thanks

hi all - motor was working when give a help with fingers- now nothing- the motor was warm but not hot- is there any hope? or it that it - worth taking apart?


wonder if other teac/tascam share the same motor?

Hi folks


Does anyone have any info, especially a schematic for the Dolby Cat. 680 bit rate converter board? All I know is that it was for the CP500 Cinema sound processor.

Comments, suggestions and questions well appreciated:

V2 - Google Photos

Hello,

I have a pair of NAD 802 speakers and although I like the sound of them I think that one of em has a tweeter problem. I (think) I can hear somewhat of a scratchy sound sometimes. It's not permanent but at certain frequencies it makes me wonder if the tweeter might be either damaged or misaligned or something else which makes this scratchy thing at "mid frequencies". Are there ways to isolate this problem to be sure its even there and not just in my head? And even more important...are there solutions I can try to fix this? If not, is it possible to swap tweeters with other speakers if the parameters are identical or is there more to it than the obvious like size, impedance, power rating etc?
I'm going to exchange left with right speaker now and see if its still there or if it is indeed the speaker but thats all I can think of in order to figure things out.
What I noticed is that both tweeters seem to be slightly cracked around the screw holes and I already aplied a bit of glue to the craked parts but could this even be a source for scratchyness or could it even be a problem with the crossover capacitors ? I dont remember if I recapped them, will have to open them and have a look inside...
As you have probably noticed I'm a bit clueless when it comes to speaker healthcare 🙁
Thanks for any advise and have a great weekend!

How to select a replacement MOSFET/transistor?

Regarding a recent post,

Is this the correct method to select a replacement transistor (when the one on the board is discontinued or unavailable to purchase)?

My method:
1) Match the transistor type (NPN or PNP).
2) Match the "Vceo" voltage.
3) Same or higher "Collector current".
4) Same or very similar sized package.
3) buy the complimentary transistor at the same time.

Anything else I should be considering?

I recently picked up a non-working Marantz PM-34 amplifier for cheap.

I received it yesterday and done a quick visual check before powering it on.

Powered it on and nothing! Tested the internal and it was knackered. I ordered replacement fuses (glass fuse, 20x5mm, type T, 1A). I fitted the fuse this morning and when I turned it on the fuse blew straight away.

1st problem:
========
I have tested the main mosfets/transistors for shorts and found that Q764 (PNP) on the the right channel has a C-E short.

Q764 = 2SB1254
Q762 = 2SD1894

First questions:
1) Am I correct in thinking that I should I be replacing Q762 (NPN) at the same time as replacing Q764?
2) Would a FJA4210OTU be a suitable replacement for a 2SB1254. I chose this transistor because it has the same "Vceo" voltage, is available in the package and has a higher "Collector current".

2nd problem:
========
The two white cement resistors (2x0.18 ohm) seem to be reading out of spec.

R767 (L-ch) readings are as follows:

L - R = 1.88 ohm
C - L = 1.50 ohm
C - R = 1.63 ohm

R768 (R-ch) readings are as follows:

L - R = 1.56 ohm
C - L = 1.66 ohm
C - R = 1.97 ohm

Questions:
1) Should I replace the two resistors (at the same time as the 2x mosfets on the Right channel)?
or
2) Should I replace the two resistors, after:
a) replacing the Q764 and Q762, then
b) retesting both cement resistors?


Thanks in advance for any help.

Hi all,


A couple of years ago I build active speakers, drivers are Beyma TD365 CD horn + CP755/Ti compression driver, Beyma 8LW30/N midwoofer in 16L closed cabinet and 2x Beyma 10LW30/N woofers (in a tapered transmission line). All are driven by Hypex DSP2.400 plate amplifiers.

Now I am looking into converting the mid section (Beyma 8LW30/N) into a CD design to match the horn. After reading a lot online I found the design by Jag768 (here on the forum) very interesting.

After thinking about it for some time it occured to me that maybe what Jag768 has done with "resistive ports" should also be possible with passive radiators. I did some sims in Boxsim 2.0 with active drivers to get an idea of the transfer function that is needed from the side fireing woofers to get CD down to about 100Hz.

Some very basic sims in WinISD indicates something similar should be possible with Dayton audio DSA270-PR 10'' passive radiators fireing to the sides.

This would be a relatively simple modification, just dusting off the router to make some holes in the sides and re-adjust the DSP.

Any toughts why this would or would not work?

This schematics has no capacitors in the signal path, and demonstrates wide pass band even with standard easy obtainable parts.
Output voltage is rather stable, within 10mV. It is adjusted by the R5* resistor.
40mA idle current through T2 and T3 was choosen for using them without heatsinks. By adding heatsinks, the current can be encreased correspondingly by adjusting (decreasing) the R7.
I put the schematics together on the breadboard, and made some measurements.
Maximum undistorted sine signal is 17V RMS, the clipping is nicely symmetric.
Also shown the 100kHz square wave (output amplitude is scaled to the input), and 1MHz input and output sine waves.

Hello,

I've found good information for my speaker setup on this forum, but I I've a question I can't find an answer to.

I've an 4 channel (car) amplifier which I can bridge to 2. So I would be able to drive 2 subwoofers.

I wonder if it would be possible to let these 2 bridged channels drive different frequencies on 1 subwoofer, so I can put more gain on the lower frequencies. Adjusting the settings for lpf, hpf and gain must be doable.

But is it possible one way or the other to put the channels together without damaging the system? Or compromise the sound?

Regards, Hajo

Dear All,

This paper concludes the 3-part miniseries on Minimum-Phase extraction.

https://www.bodziosoftware.com.au/Loudspeaker Driver Characterization.pdf

Best Regards,
Bohdan

How I came to this point is a bit of a long story but I really want to make the best of my Eminence Beta 12LTA using an existing enclosure.

What do I have so far?

- A brand new pair of Eminence Beta 12LTA 8Ohms (no filter)
- I have a 114-litre enclosure with a single port 10.3cm diameter and 2.14cm (ish) length, which gives 83.32cm2.This port length came from an online calculator; the port diameter was already there.
- The enclosure is lined with 1.2 cm of felt (except for the baffle)
- As a tweeter I use a Philips RT8 band (circular)tweeter with a 2,2uF capacitor, I used a smaller value (1.0 / 1.5) at the start but I really thought the sound was missing something (gap?).

How does it sound?

It sounds beyond expectation! There is a lot of sound. There are nice highs and surprising lows and I like the “Live” sound. But if I am being critical it sometimes sounds a bit hollow in the mid’s and low’s. And although there is a lot of sound in the low section it sometimes lacks of pressure (I hope that is a right assumption).

What are the worries?

In the Eminence design sheet I see the use of a 30Hz Highpass filter. On the Internet I see a lot of different passive filtering going on and a lot people use DSP (which I don’t have) to control this driver.

What do I hope for?

Nirvana would be nice… ☺ but if someone says “this is it” that would also be fine but a “simple/cheap” tweak to bring this driver in this setting to a slightly higher/next level would be very nice.

R

Hi All,

As far as I can tell the current Onsem/Fairchild datasheet for this device does not list a maximum base current. Does anyone have an idea of what it might be?

For comparison, the max base current for the BD139/140 is 0.5A and max collector current is 1.5A (33%). Using 33% on the KSC3503's 100mA max Ic rating I would suspect 33mA is a reasonable guess.

Any thoughts?

Many thanks,

Greg

Why is full wave voltage doubler not used more in line level audio? Only single secondary transformer is needed and two diodes. Two diodes, of whatever type, make two times less switching noise than 4 diode bridge rectifier.

Hi,


I'm looking for a soft start circuitry for both the heater and the B+ (Moglia CCS in mind for the B+) for a 6DJ8/ECC88/6922/E88CC. Whatever manual start for the heater before or better both PS with delayed start with one front-panel button !



Would like to avoid CT trafo, so no tube rectifier. I'm aware of some shematics, but I'm more looking for a ready made DIY bare pcb to avoid layout problems.



Are you aware of a good enough pcb(s) for both those purposes ? JIM Audio or else ?


Many thanks

Hello, I am a musician, in need of an audio device for my on stage setup, and have not been able to find anything that fits the bill. So, I am investigating the possibility of building it myself and/or having it built. i am having trouble getting started though, as my knowledge is limited.

Here is what I need: I currently have a quarter inch unbalanced stereo line level signal (coming out of 2 quarter inch outputs of my audio interface). This gets connected to the quarter inch inputs of the DI boxes to get sent to the front of house mix.

I need a device that I can insert in between these two points, that will act as a mute switch. Just interrupt the signal and replace it with silence, so that if the computer decides to get weird I can mute it. And because it will be installed in the rack, I need it to be activated by a remote footswitch that I can run out to my feet, along with the rest of my pedals. I’m hoping that any quarter inch switch pedal could be used for that, which would plug in to a quarter inch control jack on the box.

I am not opposed to picking up a soldering gun and figuring out how to build a box with connectors. But I don’t quite understand how the actual switch part of it would work. Would there need to be any electronics in it? I wouldn’t want to introduce any buzz or ground problems into the audio (when the switch is in it’s inactivated/pass through state). And of course it would be ideal if it didn’t make a huge loud pop when activated.

Would I start with something like this?

1/4" STEREO CHASSIS JACK W/ SPDT SWITCHES 24-697-0

I very much appreciate any tips or info anyone might have to point me in the right direction. Thank you!

A friend of mine acquired this deck in an online auction and the VU's aren't working in recording mode, although it is recording fine.

Does anyone have a service manual for it ?

Thank You for Your attention.

Hello to all,

I noticed JLC is offering PCB aluminium board 100mmx100mm for 2 USD. Did anyone thought about DAC (or amplifier) made on aluminium board? Are there any benefits in audio purposes? What are your thoughts?

Best wishes, Milan

Since 2014 I am developping my TPA-3118 amps from scratch including pcb-layout. Although I did the same with their bigger brothers TPA3255 as well, I like these chips for their simplicity and low standby current making them the ideal choice for battery powered amps. Over the years I added some useful features that are not covered by TI's app notes. Besides this I will add some basic remarks that may or may not be interesting or enlighting for you.

LC Output Filter, Snubbers and Post-Filter-Feedback

The LC-output filter exhibits a second order lowpass filter that reconstructs the pulsed PWM signal. Sadly this is only half of the truth. The other half: The class-D bridge output is loaded by a LC-series resonant tank. At its resonant frequency the series impedance drops close to zero, load current increases upto the limits and output voltage rises far beyond supply voltage. To avoid this destructive scenario you can either dampen the resonant tank or prevent excitation by strictly band-limited audio input. The mainstream attempt is dampening the LC-circuit with the speaker load according to the formula

Z(series tank) = sqrt(L/C) = R(speaker),

so with L=10uH and C=1u0

R(speaker) = sqrt(10) = 3,16 Ohms

Should be close to perfect for a 4 Ohm speaker. Well, I do not think so. For some reason nobody points out that dampening requires a strictly real (ohmic) impedance, measured at resonant frequency. With resonant frequencies in the ballpark of 30~50kHz this certainly works fine in the lab with non-inductive dummy loads. But in real world? Did you ever find speakers with 8 Ohm ohmic impedance at 50kHz? Let me say it frankly: No way, forget this! Voice coils of real speakers always incorporate some inductance that shows up in an increasing impedance toward higher frequencies. From this point of view it would be more realistic to measure frequency response without load. I would be very interested in any gain vs frequency plot of unloaded fixed pwm-clock class-D-amp, so if you find one, please let me know.

On the other hand todays audio sources are in 99.99% of the cases band limited to 20kHz making this danger look a bit unrealistic. Nonetheless you often find warnings that class-D amps should not be operated without load - here is the reason for that statement. Moreover this I find it annoying to match the output filter to various speaker impedance and so I searched for a solution. Snubbers came into my mind. And were dropped soon, because a working snubber must either be capable to dissipate full power of the amp - which is obviously unrealistic. Otherwise it is taylored to survive - without having any effect. Remember all these burned snubber resistors on audio amps? No and no!

So let us go for post-filter feedback. This promises not only to tame the resonant peak but flattens the overall frequency response resulting in much better square wave response, nearly independent of speaker impedance. No snubber, no need to fine tune output filter depending on your speaker, no problem operating the amp without load...

After this lengthy introduction the implementation is surprisingly simple: A differentiating RC-feedback network between filtered output and input - that's all! It should be mentioned that this variant of PFFB network is quite different from the common type you will find in many debates around here. Opposed to "normal" feedback networks, the amount of feedback increases with frequency. So it is most effective in taming the high frequeny peak at resonance but with very little effect in the audio band: Do not expect signifant reduction of THD - this is not in my focus here. My priority was stability, not mind-blowing THD figures. To give an idea I simulated the TPA3118 without and with PFFB:

Hello,

I'm admittedly a total novice with this sort of thing, so go easy...

I've got a pair of harbeth speakers that belonged to my father that I'd potentially like to upgrade, if feasible. From what I understand, the newer version of the speaker is more contemporary sounding and probably more to my taste and I'd like to hang on to them. From what I could read online, the bulk of the change is from the crossover, there's some extra dampening too around port.

I've found pictures online of the old and new crossover. I'd likely get someone with the knowhow and capabilities to do the work, if at all feasible. The PCB seems to be the exact same.

So, can this be done? Or is it a silly proposition?

Many Thanks for any input

Older Version

DSC 0750 — imgbb.com

New Version
Harbeth — imgbb.com

I am on my third RF T20001BD. I did find a switch for the first one, and the second one (bought on eBay as parts/not working) actually worked fine. My third is a bit puzzling.

It was rough. Missing front cover, dirty as can be, just rough. It has 4 shorted outputs and all the PS FETs were shorted, as well as their drivers and (open) gate resistors.

I replaced the outputs, removed the PS FETs, replaced the gate resistors, and replaced the drivers. I powered it up using ground and remote, no B+, and went to see if my gate waves looked good... that's when the smoke started.

It popped my new gate drivers. I removed them, and without them in the circuit, I have a great looking gate signal (at the driver).

Drivers Q1/4/15/18 all have gate signal/10v/open on their terminals. IIRC, these are the NPN

The other drivers (PNP) are the ones first to go up in smoke.

I have a diagram, but I'm not sure where I should be looking. I don't see anything obvious (in my eyes anyways) that could be causing this.

I could use some help if anyone can!

hi how do reel to reel machines cope with plastic spools- i have uher 4200- surely they must spoil the alighnment?

Have you noticed the rise in prices ?
Sure covid , supply chain disruptions ....
My basket on TI's store became 4 % more in 2 months , not to mention a tripling of "out of stock" items.
Checking Mouser , higher prices too .
Of course not all items have a price rise , but not many have a lower price.
Inflation is here !

I have a dh 220 with Fantasia upgrades and turn on thump blockers , I have noticed a hum/vibration ever 45 seconds that last for about 5 seconds . It is not audible through speaker just at the amp . Any thoughts ?