So I'm setting up a PA system and I'm kind of confused. I have a berhinger europower p1500 amp. This amp is to be bridged to my subwoofer, a behringer e1800x. I'm imagining this is a very simple answer but it still is confusing me. To go from the amp to the speaker am I required to have a balanced (trs) cable? I have the speakon for the amp wired to +1/+2 but then to go into my mixer I require a 1/4" connector. if i am using a TS cable would that not be putting power to the + terminal (tip of the TS cable) and then also power to the - sleeve which is the ground? isn't that a textbook short circuit? does it work like this or am i required to have a balanced TRS cable? I am very confused.

Also, once it goes from amp to mixer to speaker does the speaker end also need to be wired +1/+2 or does it stay +1/-1?

thanks so much for any help.

Hello again! some time ago purchased this cd player with the usual broken laser head stepper gear, I replaced it, but it's still dead.

When switched on, the motor that moves the cd rotates at full speed (or fast) and eventually stops, no matter if the cover is open or not, as if the closing switch is ignored, the lens tries to focus, but the laser is not perceived. There is no other head movement.

I notice that the R176 resistor gets very hot, I don't know if this is normal, however the resistor measures 327 Ohms which according to the schematic is 330Ohm which seems correct to me. The consumption of the single board on power on alone is 0.12A which seems a lot to me, around 1w for only the LCD?,

The voltages indicated on IC101, IC 841 and IC 871 are correct.

On the CD802 connector pins 1 and 2 receive about 1,7v if we act on the SK130 switch (door switch).

Is there any way to know if the laser is damaged? I think there is no replacement now if it is damaged. Any help is appreciated. Thank you very much!

It strikes me as very odd how almost everyone wants feedback from me these days - even my bank now asks me for transaction fb when I buy things!

Anyway, hello peeps from the forlorn UK. My main electronics interest is not audio but vintage calculators (early 70s), but having decided to treat my niece to her very first 'proper' hi fi (compared to a smart TV and sound bar) for her 18th bday later this year, I had the idea to graft one of those android car head units onto a vintage amp I have, to make it 'cool' and also be able to talk with her cellphone.

But I might have to forget that idea - the vintage amp I had in mind is a Metrosound ST20 which I bought for £10 in 2011, and I only bought it because it was made in the town where I grew up and now live in. My main interest these days is local history.

Well, I had always assumed that the ST20 was bargain basement, but on a fresh surfing of the waves to start my idea off, that seems not to be quite true and I now can't bring myself to cannibalise it! Instead, I might restore (recap and possibly reswitch) it, try to add more separates (I just grabbed a very poor condition companion 8-track deck on eBay), and one day donate the system to the local museum... if they can find room for it.

My surfing brought me to the ST20 thread on this forum, and it was so interesting and potentially useful that I decided to sign up to express my gratitude. I must give a special thanks to Mooly the mod... I might just be coming back in a while to ask for more insight into the schematic Mooly! Old calculators rarely have any sort of audio capability, and those that do are best not mentioned here!

Cheers, amplifryer

I have some very large heatsinks for sale - see photo. They measure approx 32 x 30cm and the longest fins are 7cm long. They weigh 5.5kg each. I do not have a dissipation rating for them but you would have to be building a truly monstrous class A amp for these to be inadequate!
They also look really cool because of the curved profile of the fins. Price is £45 for one or £80 for two plus carriage. I have several pairs for sale.

Hello! Thanks for accepting me. I play the guitar for more than 30 years. I am a software engineer specialized in machine learning and AI with some knowledge on electronics and audio. I've been reading this forum for some time and hopefully I will contribute to this community the best way I can.

Variable inductance with frequency is something that occurs in all inductive loads, and without it, high inductance subwoofer simulations are very inaccurate. Woofer Tester Pro has a way of measuring variable Le, and simulating it is possible with their software. With that and with the help of @Bolserst, Hornresp now has the function of simulating it. Bolserst posted a spreadsheet on the Hornresp thread which can calculate semi-inductance/variable Le with frequency using impedance curves. With that, you can create much more accurate sims. Because of this, I will not simulate any speakers over 2mH of inductance without Semi-Inductance anymore. Here is a link to the spreadsheet: Hornresp - Page 851 - diyAudio
Here is a list of Semi-Inductance drivers:
Semi-Inductance Drivers - Google Drive

I'm adding my final updates to my Citation 2024 amp'

1. No change to the main PCB.
2. Speaker Dethumper PCB , Resistor R1 changed to a 200k pot by drilling two holes for the pot.. The cap C1 changed to 220uF. Time can be set from 48-0 seconds.
3. New Gerber rev 4 files for the speaker PCB with Gerber files is attached below.
4. Power supply PCB changed to rev 15. C2, C4 changed to 1000uF 500VDC. Added a terminal block to add a choke of desired. L1 Chole is a 1H 600mA.
5. Optional two VU meter panels are interchangeable. One is analog VU meters, the other is a LCD Touchscreen. Both are fed off the 12 volt power supply and the left/right signals from the main PCB. All files for both versions are available in this post.
6. Also include with this post are all the schematics, Gerber assembly, BOM and photos.
7. My only request, is that if anybody does try this project to let me know how it works out for you. You are responsible for your changes.
8. Did look into upping the power from 30 to 60 watts. Decided not to do after looking at the original amp and it's wiring.
8. The amplifier has been running fine since August.

Enjoy... Happy Holidays

I'm thinking of building this measurement amplifier having seen the reference to it in Self's Small Signal Audio Design.

I note that Samuel has kindly made gerber files available on his website but I was wondering if anyone had already ordered some boards and had any spare.

Thanks

Steve

Hello,

I've checked all the MOSFETS, inductors, diodes and filter caps and there's no shorts. I've removed the IRS 2093. When I turn the amplifier on, with only channel 2 high and low side transistors in and they're getting hot, I limit my PSU to 1amp hence why I think this hasn't blown up yet I think.

When all channels are populated with MOSFETS only channel 3 MOSFETS get warm, mostly the high side one.
Now with only channel 2 populated the high side is significantly hotter than the low side.

What could be the cause of this?

I'm helping a friend with his Quad am8/16 which is a mono amp used by the BBC to power one of their monitor speakers, we want to test it but need to make a lead up from phono to 3 pin xlr. I'm having a complete mental block of how to wire one up, can anyone give me a point in the right direction?

Hi,
I have a question about B2031a.
They are four potentiometer on the pcb - VR1,2,3,4.
All available from outside.

VR4 is input level
VR3 is bass speaker level ?
VR1 and VR2 are in HT part.
What are VR1 and VR2 doing ?
One is for HT level (VR2 ?), another one (VR1 ?) for 17KHz boost ?
Am I right ?
I just would like to reduce HT level.
Look at the attached crossover picture.
Thank you 🙂

Hi all,

For those of you who burn in your system/components I would like to mention the Cascade Noise Burn in sound file from TARA Labs.

It is an mp3 file with low to high frequencies continuously overlapping. IMHO a quite impressive difference using it, however, from a practical point of view please note that it can be VERY noisy so I would suggest starting out at low volumes (and maybe in general be careful with loudspeakers and headphones).

Download link is here: https://taralabs.com/media/cascade-free-burn-in-disc/

( ... not intending to start a discussion about whether or not burn in matters ... I reckon there may be many opinions about this ... )

Cheers,

Jesper

Hello everyone, I am trying to figure out why resistors R870 and R871 are burning out on the power supply board of the Marantz PM16. All connectors from the board have been disconnected, only the input power remains connected.

I bought the amplifier with regular 150R resistors instead of the original fusible ones. 😳 These don't burn out, but the ±60V voltages are incorrect. If everything is connected and the regular 150R resistors are in place, as it was when I bought it, the -60V rail measures -38V, and the +60V rail measures +25V. The 5V and 22V rails are correct. I have already measured almost everything on the power supply board. If I test it using a 100W light bulb, the 1.2R fusible resistor does not burn out.

Q854 (KRA104M on my board) seems suspicious. It measures strangely, but that might be due to its different internal structure.

Have you encountered a similar problem? Thank you.

Brought this a few yrs ago already built from a guy in Sweden has a few upgrades Caddock film resistors on out put and Auricap capacitors as seen in photos. I used this with a Khozmo stepped attenuator and it sounded really good. Looking for £150.00 plus postage or it can be picked up from Chichester West Sussex. Payment by bank transfer or paypal f/f.

I am trying to learn ngspice because it is open source and free. Unlike LTSpice I have to type the netlist directly as a text file which is boring and very prone to errors. Are there any graphical software tools I can use to graphically create .cir files?

What have I got myself in for?

The cabinet is 1,750mm tall, 550mm wide and 600mm deep. With 25mm thick panels of Euro birch ply, the volume is approx 480 litres, or 16.95 cubic feet.

Lovely Jarrah veneer, with Jarrah hardwood trim.

The driver is Lii's top spec reference unit, with this client receiving pre-production versions. Beautifully made, in polished chrome...very heavy.

Adding some quality Cardas terminals and solid core thin cabling.

With a low Fs of 28Hz, the cabinet has been tuned to 30Hz, using a wide slot-port.

Grill cloth will be a Marshall vintage style.

Should be fun.

I have around 1000 CDs collected over many years but find myself increasingly using streaming (Spotify and Apple) along with my vinyls. I am moving house, and SWMBO has intimated that they all need to go. What do you think? Keep 'em or ditch 'em?

Hi From Australia - Looking forward to contributing to the forum. Specifically wanted to join to add to thanks a member who posted a thread which helped me fix up an old REL acoustics storm MK1.

I'm a 50yo electronics hobbyist (software engineer by trade) and want to say thanks for some of the incredible help and resources in this forum.

I'm preparing to restore a family Rock-Ola jukebox and so have been studying the schematic for about 18 months and learning every aspect of tube circuits I don't yet understand. I've now modelled the entire amp in LTSpice and feel like I understand enough not to kill it or me. Some of the posts on this forum have been incredibly insightful, especially the spice models.

I've registered so I can share my simulations and everything I learned along the way - could be a big post! Any tips on where I should submit that? (I guess Amplifiers>Tube.

thanks

As some of us quickly learned from this thread that Lii Audio (established in 2006) is not Lii Song (established in 2019) now it's easy to define the original manufacturer by a line of brand new Coaxial Drivers.

As a fan boy of Tannoy I'm glad the Lii Audio (not Lii Song) is now making not only full-range, but new BIG Coaxial Drivers.

In this thread I want to discuss their new line, please do not post here about Lii Song as they have been separated from each other due to war between two ex partners. This is why you will not find coax drivers in the Lii Song catalog.

I hope Lii Audio will continue manufacturing unique drivers and will be able to expand their sales internationally, at the moment you can follow them on instagram for updates.

If some of you will find any reviews or have personal experience with any of Lii Audio COAX drivers please post in this thread.

On Ali Express for international buyers at the moment I can see '12 inch (C1202) , also '15 inch (H1502) and even '18 inch (Lii Audio TRIAX 18 and C1802) models and they are working on a bigger size as you can read on instargam page.

Some of them are good looking units, but pricey! What about sound quality?

Been cranking rock and roll since the late sixties. With my 70th in the near horizon, I am dedicating this journey around the sun as a music renaissance for the ole man. Having just winged it for all these years, I am digging in deeper into the addiction and this time doing it right. Self study for the last several months, thank you all those whose posts have helped my understanding of the fine art of music reproduction. Sound measurement and the fine art of speaker building are my current educational endeavors.

Does anyone know how to remove the counter weight shaft from the tonearm , so that I can replace rubber bushing that is sagging. I see one grub screw in the shaft and two below on the round part of the arm, but not sure which area. Also, can anyone confirm whether they can be removed, because I see some residue that looks like glue. This is from a QL-10 that is in great shape, except the arm, and I would like to have it spin vinyl again. Thanks.

Hello.

Would anyone know where I would be able to get a replacement bulb (called neon lamp in the service manual, but no part number) for the power lamp on an HH Scott 99D amplifier? I have some LEDs, but the voltage across the connections for that bulb seem pretty high.

Thanks in advance,
Les

Designing a soundbar!

Using B3N woofers, based on Zaph's design:
http://zaphaudio.com/audio-speaker18.html

Posting this in Subs...as the soundbar will mainly be on the sides of the enclosure. Wondering if I can find a way to put a TH in here for the sub!

Since sub will be in close proximity, will likely cross over at 150 hz. That may be the upper limit of the BT 2.1 Amp I'm planning to use:
https://www.amazon.ca/Fosi-Audio-Amplifier-Integrated-Speakers/dp/B0C9WV3XXS/ref=sr_1_3?keywords=2.1+bluetooth+amp&psr=EY17&s=black-friday&sr=1-3&ufe=app_do:amzn1.fos.71722c10-739d-471b-befb-3e4b9bf7d0d6
(I can' t find the hipass spec now... but I don't think it went up to 200hz)

and the sub!
https://solen.ca/en/products/airborne-ur151b4-lj14m-15cm-aluminum-cone-shallow-subwoofer

Thankfully the 2.1 amp will give control over the bass, so I'll have tons of low end headroom.

I'm entering specs into Hornresp - but I have questions:
Is Mmd same as Mms? Is the CM correct? .83 mm/N on specsheet, but 8.30E-01 in Hornresp.


Designing a soundbar!

Using B3N woofers, based on Zaph's design:
http://zaphaudio.com/audio-speaker18.html

Posting this in Subs...as the soundbar will mainly be on the sides of the enclosure. Wondering if I can find a way to put a TH in here for the sub!

Since sub will be in close proximity, will likely cross over at 150 hz. That may be the upper limit of the BT 2.1 Amp I'm planning to use:
https://www.amazon.ca/Fosi-Audio-Amplifier-Integrated-Speakers/dp/B0C9WV3XXS/ref=sr_1_3?keywords=2.1+bluetooth+amp&psr=EY17&s=black-friday&sr=1-3&ufe=app_do:amzn1.fos.71722c10-739d-471b-befb-3e4b9bf7d0d6
(I can' t find the hipass spec now... but I don't think it went up to 200hz)

and the sub!
https://solen.ca/en/products/airborne-ur151b4-lj14m-15cm-aluminum-cone-shallow-subwoofer

Thankfully the 2.1 amp will give control over the bass, so I'll have tons of low end headroom.

I'm entering specs into Hornresp - but I have questions:
Is Mmd same as Mms? Is the CM correct? .83 mm/N on specsheet, but 8.30E-01 in Hornresp.

OK, this one deserves a separate thread, I believe.
It incorporates a lot of experience gained during the last year or so with simulations, prototypes, measurements, listening, etc.

Though, this one is not prototyped yet (working on PCB), it is based on my initial tube hybrid design >HERE< with certain refinements, utilizes a recently developed "super-Hawksford" VAS (inspiration and co-operation from Ostripper ), driving two pairs of lateral MOSFETs directly (already ordered ones for prototype).

For those, who doesn't want to deal with tubes (athough, I recommend to do so 😛 - takes only additional 6.3VAC source and additional 20 seconds delay at soft-start), I have added a number of IPS LTP options - jFET, BJT and combination of BJT + jFET source follower (note some adjustments in compensation, degeneration and load resistors values). Overall measurements are pretty close, however the tube one shows the best open loop linearity and transients handling (showing the lowest voltage gain at the same time), so my first prototype will go with the tube at the input.

All the virtual measurements shown are also done based on the TubSuMo model. One can say - it's just a model, let's see what real life will show. Agree, but having a lot of experience with modelling and further live prototyping, I would say - this model shows an outstanding, very "clean" performance in many aspects. Even at the swing close to the rails, even with heavy capacitive load, at clipping, etc. It's a hell of a VFA!

I will probably add a DC servo to the final design.
Also thinking about reserving the places for presented IPS options on PCB, so that it can be used for any of them.
It will be possible to use the front-end part in combination with well-known SlewMaster series of OPSs as well.

Stay tuned! 😉

Cheers,
Valery

I have to replace the volume control on my old SU-V8 amplifier due to severe mistracking between channels at lower volume levels, so I figured why not add a remote volume control while I'm in there.

I ordered a kit from ebay which uses a RK168 motorized Alps pot and also has power relay. The stock unit uses basic carbon comp elements, which aside from tracking poorly (had to turn balance control almost to 3 o'clock to even it out) otherwise sounded ok.

This is the kit I ordered and then will be swapping the RK168 pot for a higher grade RK271- Remote potentiometer kit with power switching



I'll post more info as I receive more of the parts. I also have added a buffered, balanced pre-out using DRV134 chips. They actually sound very good despite being op amp based.

The main reason I'm doing this is because of the excellent MC phono stage the amp has along with its gutsy double transformer dual mono power amp design.

Hi All,

I am having some trouble with a REL Storm MK1 amp that Is behaving odd! Its a Lateral Mosfet amp, with a pretty basic board using BUZ900/905's.

It powers on, voltages look good and i can initialy hear the 1khz signal fed from my picoscope but it will fade out and then be very tempramental, coming and going but always very quiet.

I have checked the Buz900/905 Mosfets, drivers and replaced the opamps(tl072) all which look good. I have traced the signal out of the preamp onto the powerboard and looks good.. Finally i have reflowed all the solder joints and contact cleaned the pots/switches!

What else should i be looking at, would electros cause this? I cant find a schematic as REL are not forthcoming with these🙁

thanks
Craig

The sound pressure of an electric matrix speaker will decrease with a monaural signal, but a physical matrix speaker will have the same sound pressure for both stereo and monaural signals.
The biggest advantage is that it can be used with BTL and D-class amplifiers.

These boxes were separated for both sides of the TV, which also improved the surround sound experience.
If it is not possible to place speakers to the left, right, or behind the listener, I think front-only surround sound is effective.
I used three types of drivers (Alpair5.2, CHN50P, CHN519) I had on hand, and the sound quality is perfect.

Hi all,

I completed a fun project using some concepts I've been learning and throwing around ideas with and wanted to test some things and try a few new things and it gave me something to work on through the hurricanes instead of wondering what it would be like to use my subs as canoes after being washed away in hurricanes (I'm in Florida). Finished this one up and just wanted to share the results because its different and probably about as DIY as it gets in many ways. So I hope you can come by an take a laugh at it or maybe some interest in it, either way, as I went to clown town on this build and tried a little wacky finish as practice using some materials new to me, etc.

GRS12SW-4 x 8 Drivers, These are cheap, was $25 a pop. High Qts, Fs in around 30hz in series. 8.5mm excursion but its good beyond that until it hits xmech limit. I have used these in the past in open baffle platforms to punish out 10hz and up for tactile response and despite being cheap and lower xmax, they do it quite well. So I figured, let's put them in a bigger open baffle and stand it up as a tower.

I recently made some threads to ask questions, figure out how to do the right baffle design, ended up with a W-frame, which lead me down the rabbit hole of cavities and slots and slot loading, mass loading, etc. Really fun stuff. I put all that into practice and made something that works (I think?).

I wanted to keep opposing pairs for vibration suppression in the structure as I've done this in the past and I really like the effect. My trinkets and drinks don't walk off the tops of the cabinets anymore which is fabulous to not have invisible cats in the rooms.

My old threads:



Here's the results, for the TL;DR people. The build log and image dump will be in the following posts.

Thanks all for any help who contributed to my threads and questions... it was very helpful to at least exchange ideas and learn about anything offered.

GRS 12SW-4 x 8 Drivers
W-Frame Open Baffle (51" x 21" x 13.25")
Slot loaded cavities (11" x 11" x 3")
Handles 960w total, but only needs less than 200w to hit excursion limits below 28hz







Response with no filters, no EQ, no low pass filter, etc, Cavity resonance peak frequency range kept (in that 200hz range). Roll off starts around 28hz or so. Needs a low pass filter for practical use, but this is the raw response to single digits and I took it as high as it would go until I saw compression starting in infrasonic values which was just under 20hz here. If I high pass this so its only 30hz and up, I can take this output much higher. So its capable of doing two different things based on the bandwidth I want to keep. Either way, its enough output for me in a room on its own for virtually anything just from cone area.





Very best,

So while working on lowering hum in my HB I noticed some strange behavior out of one channel of my amp. All measurements are taken with both inputs shorted and a speaker connected to the offending channel. While listening to hum I noticed this periodic issue. It happens like clockwork about every 10 seconds. On the scope it is getting a burst of DC from normal being 4-6mV dc to over 300mv when it occurs. It also looks like some oscillation on recovery. I'll attach scope shots. The shots are in order at a faster timebase each pic. Not sure where to start troubleshooting?? Maybe just walk through each gain stage until I see the behavior?

A few members asked me to start a new thread for these two circuits. I made them while playing with the denoiser circuit presented in this thread. The denoising circuit was developed by Elvee and improved by Diego.
I applied the denoising circuit to two types of discrete regulators and it improved their performance by quite a bit. They both have a PSRR of more than -140dB depending of output voltage/current.
I also made some pcb designs for both, with and without a capacitance multiplier. Depending on your needs it can improve the PSRR to around -200dB.
Both circuits can be made with regular parts but for maximum performance certain BJTs should be used. Voltage reference can be either two LEDs in series, Zener or even LM329. PCBs have footprints for all of these. Out of all three options LEDs have the worst tempco but it's usable.
Voltage output range should be pretty wide and limited by capacitor voltage rating and transistors used. In simulation I managed to get 30V/4A output from both circuits but some modifications are required for mora than 1A current output.
For up to 30Vout you could use two LEDs in series but above this you should switch to Zeners. I tested with IR, red, yellow, orange and green LEDs and worked fine with either. I tested this for the Vref LEDs and also the CCS LED. I recommend using red LEDs, you can use the model in the LTSpice sim files so you can test your needed part values.
I built and measured both designs with earlier versions of the posted pcbs.
If you have questions about recommended part values for certain voltage/current output I will try to help.
I'll attach the pcb designs in the next post.

First of all, big thanks to Hephaïstos (ascended Master), to Peufeu, to Douglas Self, to uncle Charlie, DestroyerX, and to all those that investigate on thermal memory distortion and finally to everyone who is willing to help me here.

This is not a thread about THD. It is a thread about experimenting with putative Low Thermal Memory Distortion or LTMD circuits.

Edit: just at the Lions Gate of 2022 I found the best output configuration. Check out post #806 (I attached the diagram down here) for the latest official Bootstrapped Darlington output configuration.

Edit: it also runs very well with VFETs as bootstrap element for the outputs.



I am proposed to implement the mods that Peufeu studied for diminishing putative thermal memory distortion effects on solid state amplifiers, but adding my own experiments on the output section, which Peufeu did not (unless I am not aware of that) address. In fact, I began my research modifying the outputs (Cascode all thy outputs), that is why Peufeu's articles were so interesting to me. I took the liberty to re-post the proposed amp from Peufeu. (it may have a minor error on the cascoded CFP like my experiment proved)

I have no electronic background; only the experience and scarce knowledge I obtained here, so be patient.

The blameless amp is the prototype to modify and since I have a Blame ST from Destroyer X, the idea is modify it section by section as Peufeu proposed and evaluate if there is any improvement in sound to be achieved.

I already swapped differential amplifier BJTs (Q1 and Q2) for cascoded CFP (J103 P channel JFET cascodying BC556-BC546 Sziklai pair) and it worked. Current is 2,09mA by side, though one may have to trim mirror resistor R8 to achieve 0 offset.

The sound, and this confirms Peufeu's claims, became very smooth and relaxed, with soft highs and more prominent midrange and mid-bass (my test speakers are very bright sounding) very soothing experience...the bad news is that the other channel has a problem that I could not solve yet: -27V at drivers bases, without oscillation 🙁 But, hey! That is the way we learn the most!

I let to the theorists the task of discriminating if this supposed sound improvement comes from increased linearity, from decreased thermal memory or from shared thermal task of units with different thermal behavior...

Time ago I had already tried a mod to the output section that I liked: I cascaded the output BJTs with other BJT power devices (D44H11/D45H11) in common-base. Not properly a cascode, since it is not a common emitter output (even if I CAScaded the COllector 😀) apparently, but I perceived an improvement in transparency and dynamics. I have also modded another amp, the VSSA, with this trick and I also noticed a worthwhile improvement. My plan is putting, like on the input section, a cascoded CFP output later. You may notice that, absolute and eternal beginners like yours truly, are willing to try mods that reasonable people would never even think of... 😀

Then, I will try the mods to the VAS circuit (cascoded-cascoded VAS) that Peufeu recommends.

But the final goal of all this is to gain experience to attack the modification of my Sony TA5650 VFET amplifier to make a real AMNESIS amp. I already cascoded the VFET common-source output section, which not only make it usable and stable, but also made it a very good sounding amplifier, with increased dynamics and punch.

I hope this humble effort awakens renewed interest in this most important topic.
Cheers,
M.

Hello all, I've recently taken on what is for me a somewhat advanced project...a rebuild of an ST-70 with an upgraded kit with auto-bias. Not VTA but similar.

I have hum in both channels. Very messy signal on oscilloscope. Multimeter Hz reading shows 60 Hz but bounces around it a fair bit.

I have entirely removed the wires between the RCA input and the PCB and it made no difference. But at least I guess that means I ruled out its coming from the input. When the RCA was connected, hum was still there when RCA shorting plugs were used.

I have also "unbundled" various wires that were running next to each other to make the wiring look neater, but moving that stuff around also makes no difference.

I have used two entirely different sets of tubes and it made no difference.

I plugged it into a PS Audio power regenerator that theoretically creates an absolutely clean AC sinewave and that made no difference.

If I put my ear near the power transformer, I do hear a constant hum that I think is 60 Hz. It's louder for the first few seconds and then drops down to a lower but constant level.

At this point, the level of knowledge required for troubleshooting has exceeded my expertise and I'd be extremely grateful for any help.

Best,
Ross in Denver

Been diving on the forums for several months, and have built a 2-way I love, which I should really make a post about, but it was for my bedroom to wake up to, so so many things didn't apply.

What I'd like to build next is a 3-way speaker pair for a small library, for two people seated a meter or two apart while reading, with great musicality, not to be played very loud. So much of what I find here is optimized for the listening position. Monkey coffins sound okay to me, but space is a bit of a premium. Would like to build a moderately sized floor or pole stander of 50-75l. I'm not asking for driver advice, but just be pointed in the general direction of enclosures/designs that are aimed at this listening case instead of playing at standard or higher levels.

I prefer sealed woofers to ported (though I did build an under-bed ported sub for the bedroom, again because I wasn't particularly high in there), and am aiming at a pair of speakers without a sub.

Please berate me as to the threads I haven't dug up.

I need a small simple audio recorder.
Sounds simple but there are a few problems.
First the owner is old, about 90. Second she has bad eyesight so cannot read screens or menus.
The recorder is to record live music playing so that she can replay it and practice playing the tune and practice the tune on her violin.
It needs to be simple, preferably one button to record and another to play back.
Has anyone any ideas

Hallo liebe DIY-Freunde,
Ich interessiere mich für DIY-Lautsprecher, DIY-Audio-Verstärker und DIY-Netzfilter. Nachfolgend ein Paar Bilder meiner Basteleien

I’m new to speaker building and would like to build the Classic GR MarKen12p.

http://frugal-phile.com/boxlib/P10free/CGR-Mar-Ken12p-310817.pdf

I’m unable to find 12mm wool felt, but have found two alternatives

1. 8mm felt from Jantzen (recycled fibers of unspecified composition, but Troels Gravesen says on his website that he uses it).
   http://www.jantzen-audio.com/wp-content/uploads/Damping-Materials-Catalogue.pdf
   
2. 5mm felt (90% wool), more expensive but still reasonably priced

Can I use two layers of the 5mm for a total of 10mm, or would 3 layers be preferable?

When the notes say “All internal panels lined with ~1/2" (12mm) wool felt (preferred), 3/4" (19mm) poly-fluff batting, or 1" (25mm) fiberglass”

Does this mean all internal surfaces, including both sides of the brace?

Starting a new project. I'd like to make something with a very fast decay from 500hz-5000hz. No bumps in the GD would also be nice.

Step one is to make lots of sims! Right now I am comparing XO's and driver spacing for the Satori md60n and BlieSMa t34b. The data is from hificompass and that is tossed through vcad's baffle sim.

The spacing and baffle shape is a little different for each image. All of the sims use a baffle with a 44mm edge radius. Also, some XO's might be crossing at impossible spots due to distortion or the FS. My main focus was to get the phase locked in and see what I could see. I don't know how much ceiling nulls matter at a frequencies where there is a head shadow? My eye likes r7 and r8.

I'll make a few more sims and look into my second and third choice mids.

fake sims of the t34b + md60n:

I have a bunch of power transformers to sell
I would prefer to sell them all together
they are so heavy that I cant even lift one of the two boxes

contact me and we can see if we can agree on a fair price

last picture is just a sample of what is for sale

I do not have specs but most are labeled as to where they are from

I am in Washington state USA

I have three transformers for sale, two are the same
pulled from audio equipment power supplies
price is $100 plus shipping for all three or $45 for the large one or $40 each for the smaller ones
I only have the specs that are printed on the transformer

Just joined up today, have been on this site before and have gathered much important info and advice. Look forward to asking more questions. LOL.
My equipment I have to throw in a 2019 GMC Denali 2500 HD is as follows:
Kicker 46CSS674 Components
Kicker 46CSC674 Mids
Kicker 48CWRT122 12" subs
Alpine PDR-V75 5 Channel Amp
Kicker CXA1200.1 Amp

...found them plus a ton more useful information here, so I signed up and hope to contribute in the future!

Thanks!

Hi All, I've been an electronics hobbyist for many years, and got into audio about two years ago by building a speaker kit from Parts-Express, and most recently a pair of custom bookshelf sized speakers with Morel drivers where I designed the crossover. Ironically, finishing the veneer on the cabinets was my biggest obstacle! 🙂 I'm now going down the DAC/Streamer rabbit hole inspired by Gabster videos and IanCanada parts, and I have two unassembled ProtoDACs as well.

Hello. I’m looking forward to joining the convos. I’m a hobby audiophile and record collector.

https://shenzhenaudio.com/products/...5d8r89rrFmVoY_16pgkENLterw29LG4FPSLqmMV0pY6yE

What are your thoughts?

People always talk about JFET in the input stage, but nobody talk about using MOSFET in the input stage.
The only reason that I could find is MOSFETs have high noise figure. How high is too high? Does it matter in the power amplification context? It is not a preamp.
As JFETs are pretty delicate, the voltage rating is pretty low. You have to babysit them. In contrast, you can find MOSFETs with voltage rating from 60v to 240v in TO-92 package easily.
In my simulation, BS170 is more linear, lower distortion, higher transconductance than 2SK170. Why don't we use MOSFET?

I am attempting to upgrade an old Pi3 with MPD outputting to a "7.1 sound card" with a Pi 5 and a HifiBerry DAC 8+ hat. So far, I have been able to make sound, but not really get the hat configured so I can set up my file streamer or anything further.
aplay -L:

null
Discard all samples (playback) or generate zero samples (capture)
sysdefault
Default Audio Device
lavrate
Rate Converter Plugin Using Libav/FFmpeg Library
samplerate
Rate Converter Plugin Using Samplerate Library
speexrate
Rate Converter Plugin Using Speex Resampler
jack
JACK Audio Connection Kit
oss
Open Sound System
pulse
PulseAudio Sound Server
speex
Plugin using Speex DSP (resample, agc, denoise, echo, dereverb)
upmix
Plugin for channel upmix (4,6,8)
vdownmix
Plugin for channel downmix (stereo) with a simple spacialization
default
Playback/recording through the PulseAudio sound server
hw:CARD=vc4hdmi0,DEV=0
vc4-hdmi-0, MAI PCM i2s-hifi-0
Direct hardware device without any conversions
plughw:CARD=vc4hdmi0,DEV=0
vc4-hdmi-0, MAI PCM i2s-hifi-0
Hardware device with all software conversions
sysdefault:CARD=vc4hdmi0
vc4-hdmi-0, MAI PCM i2s-hifi-0
Default Audio Device
hdmi:CARD=vc4hdmi0,DEV=0
vc4-hdmi-0, MAI PCM i2s-hifi-0
HDMI Audio Output
dmix:CARD=vc4hdmi0,DEV=0
vc4-hdmi-0, MAI PCM i2s-hifi-0
Direct sample mixing device
usbstream:CARD=vc4hdmi0
vc4-hdmi-0
USB Stream Output
hw:CARD=vc4hdmi1,DEV=0
vc4-hdmi-1, MAI PCM i2s-hifi-0
Direct hardware device without any conversions
plughw:CARD=vc4hdmi1,DEV=0
vc4-hdmi-1, MAI PCM i2s-hifi-0
Hardware device with all software conversions
sysdefault:CARD=vc4hdmi1
vc4-hdmi-1, MAI PCM i2s-hifi-0
Default Audio Device
hdmi:CARD=vc4hdmi1,DEV=0
vc4-hdmi-1, MAI PCM i2s-hifi-0
HDMI Audio Output
dmix:CARD=vc4hdmi1,DEV=0
vc4-hdmi-1, MAI PCM i2s-hifi-0
Direct sample mixing device
usbstream:CARD=vc4hdmi1
vc4-hdmi-1
USB Stream Output
hw:CARD=sndrpihifiberry,DEV=0
snd_rpi_hifiberry_dac8x, HifiBerry DAC8x HiFi pcm5102a-hifi-0
Direct hardware device without any conversions
plughw:CARD=sndrpihifiberry,DEV=0
snd_rpi_hifiberry_dac8x, HifiBerry DAC8x HiFi pcm5102a-hifi-0
Hardware device with all software conversions
sysdefault:CARD=sndrpihifiberry
snd_rpi_hifiberry_dac8x, HifiBerry DAC8x HiFi pcm5102a-hifi-0
Default Audio Device
dmix:CARD=sndrpihifiberry,DEV=0
snd_rpi_hifiberry_dac8x, HifiBerry DAC8x HiFi pcm5102a-hifi-0
Direct sample mixing device
usbstream:CARD=sndrpihifiberry
snd_rpi_hifiberry_dac8x
USB Stream Output
----------------
when I try to address any of the 8 outputs (HifiBerry says these are not stereo pairs, but individual channels), I just get errors like:
jay@raspberrypi:~ $ aplay -D sndrpihifiberry,DEV=0 --dump-hw-params /dev/zero
ALSA lib pcm.c:2666🙁snd_pcm_open_noupdate) Unknown PCM sndrpihifiberry,DEV=0
aplay: main:831: audio open error: No such file or directory


I know I'm being stupid, but I've been stuck here for months. . .

Thanks for any advice!

For a streamer based on a Raspberry 4, I bought two DAC hats - a HifiBerry DAC2 pro and an AUDIOPHONICS DAC I-Sabre ES9038Q2M.

I measured THD and noise on both hats with a Motu M4 and an E1DA COSMOS ADCiso. Software: REW and AudioTester. For playback I used LibreELEC and Moode. The test signal was a wav file with a 24-bit sine (sampling frequency 44.1 kHz, level 5 dB below FS).

While the noise floor was quite low with both DAC, I was a little surprised with the comparatively high THD value of around 0.04% for both hats. For comparison: the distortion of an old Roland duo capture EX DAC (same measuring setup) was more than an order of magnitude lower (0.003%) and the value published by ASR for the AUDIOPHONICS converter was even lower than that. Both ADC and programs delivered very similar results, BTW.

OK, 0.05% is (for me) not too bad, but I'm interested in what the reason for the high THD values could be. Any ideas?

Peter

It is my understanding that a. a digital signal is expected to/from a (mini) USB connection and b. that while the PAM8403 output is regarded as digital it is actually a PWM signal. If this is so can I feed a USB port - perhaps to be connected to an iPhone - from a PAM8403? (I have attached the PAM8403 spec sheet.)

Hello clever people 🙂

I am rebuilding a 211 Power supply and have the following layout as attached, using 440VAC rated capacitors.

These are the smoothing capacitors that follow a voltage doubler circuit using 2 5u4GB valves to achieve the 1000V, along with some inductors prior to this bank of capacitors.

My question is simple, should I connect the dotted line between the 3 capacitor pairs at the voltage mid point or not?

I hope this makes sense as a question, the answer maybe it does not matter!!

Thanks for the guidance,

Rich

Hi Gurus!

I am trying to figure out how to model the lower frequencies from the attached speaker, which is an old zenith driver.

The surround of the cone does not have the typical flexible gasket, but this
Driver seems to have a nice sound down in the 500 hz zone, though it only goes to 8khz or so.

All the modeling software that I have used so far requires Sd...but this is surely not a pistonic movement situation.

Is this a case where I am going to have to acoustically measure in the baffle to know what things look like? Or is there a rough way to estimate and get close?

Is this thing even worth playing with? I suspect there is a reason I don't see these anywhere but old systems.

@jholtz

Dear Jim,

Hope you are going OK. I know Curt is probably busy as per usual and hasn't had time to update the website speakerdesignworks.com
Is the Anthology II design completed? I know a few people interested in this design, which uses the tried and tested RS225-8, as well as good value SB drivers like the SB15CAC-8/SB26CDC.

Your cabinet designs are always well thought out and prioritise aesthetics and ease of build. And Curt always takes care on the passive crossover, including taking off axis responses all the way out to 90 degrees, to ensure, among other things, good directivity matching and a smooth even power response.

Did you have the opportunity to scale down the cabinet to 80L for the pair of RS225-8?

That midwoofer is hard to beat for the $, although that doesn’t stop me from continuing the search.

Yours sincerely,

Thanh

Unknown reason of constant blown fuses at model 3.0s located in the 230VAC line to transformer's primary input forced me to find out the differences to the reliably operating model 3.0. The following was observed in detail:

With this power amplifier (independent mains transformers for each channel), the fuses between the mains connection and each mains transformer, located at the back plate, often blown away - sometimes only those from the right channel or only from the left channel, sometimes also those from both channels.

As a first step, I switch-on the power amplifier at another place with good daylight conditions near the window without connected loudspeakers and pre-amplifier.
The fuses do not blown here and the DC voltage values ​​as well as the quiescent current match with the 3.0 model on both channels (offset between +/- 2,5mV and 5mV.
The next step was to set up the power amplifier at its usual location near the other audio components, but now also without connected speakers and pre-amplifiers.
One of the fuses blown again immediately.

Faulty wall socket for mains?
No, because now connected to the same wall socket as near the window, the fuses of both channels blown away again.

What's going on here ?

Next I examined the differences in detail between the models "3.0s" and "3.0" (of model 3.0 I create a circuit diagram with the DC measured values ​​a long time ago).
The following differences to the model 3.0 I note (check out also the schematics of the images No 1-4):

1) a. Low-pass filter capacitor is missing in the input (not used on PCB - go to image No 2 and 4 in post #2 - the one from last image and image No 3 in post #2 I have added, the value in the 3.0 is 220pF)
1) b. Enclosure (chassis) not electrically connected to circuit ground (no grounding cable soldered to the present soldering lug in the middle between the cinch input sockets and cinch input sockets of both channels insulated installed - go to image No 5) - therefore the chassis acts as an "antenna" for electrical interference fields of all kinds.

2) Input resistance reduce to 22K (47K for the 3.0)

3) NFB resistance reduced from 1K to 820 Ohm and not on the circuit board but externally in the shrink tube in series to the separate cable to the GND star point on the main capacitors (2x33mF/80V) PCB-holes therefore not used. Go to image No 8+9.
4) LTP resistor (15K) on the complementary input differential amplifier replaced by a constant current diode (possibly J508) in a TO92 outline - go to image No 7
5) MPS-A42/MPS-A92 (for VAS stage, TO-92 outline in the 3.0) replaced by metal versions in the TO18 outline without printed type No - go to image No 1 in post #2
6) Series air coil with parallel resistor 4R7 at the output is missing (but Boucherot network on the speaker terminals at the back plate is present - go to images No 5+6)
7) Bridge rectifier with single diodes in the TO-220 outline - presumably "fast-switching" or "fast recovery time" versions (printed type naming sanded off unfortunately) - see images under
Unknown TO220 Diodes (discrete Bridge Rectifier) for Horch 3.0S and Threshold 4000 (in model 3.0 two normal 35A bridge rectifier are in use on the bottom of the case).
8) Another transformer with the same voltage and the same dimensions, but higher current delivery capability and thus higher value for VA (in both models class II versions with angle brackets are in use - probably made by German's transformer manufacturer "FG-Elektronik" - meanwhile taken over by Uber Uns – Sasse Elektronik)
9) Inrush current limiter on the back of the mains connection plug (IEC inlet C14); missing on model 3.0 - see images in post # 41 under
The ultimate Inrush Current Limiter Solution for large Toroidal Transformers
10) Toothed lock washer (to ensure a perfect electrical connection between the output transistors connected in parallel) on the top of the board (go to image No 9 in post #2) instead of on the conductor track side - go to image No 5-8 in post #2.

Here rises up the question of which differences were wanted and which differences were unwanted - in particular the differences under 1) are unwanted in my opinion and could be responsible for the blown away fuses, because this could be the reason for unwanted high-frequency oscillations which forces the highest possible current flow like with an interrupted VBE pot for adjusting the right value for quiescent resp. idle current.

Perhaps someone also has the model 3.0s in use and could see whether a cable leads away from the soldering lug by removing the dust cover.
And maybe someone already has repair and modification experience with it.

Thank you very much for any advice.

P.S.: for the used power devices in the TO-3 outline there exist only a small range - go to the TO-3 versions in post #1, under number 1) and 4) under
bipolar (bjt) transistor families for audio power output stages
Unfortunately all out of production (obsolete):
1) 2ST5949/2ST2121 250V 17A 250W
https://www.st.com/resource/en/datasheet/cd00178796.pdf
https://www.st.com/resource/en/datasheet/cd00171926.pdf
2) MJ21195/21196 and MJ21193/21194 250V 16A 250W
https://www.onsemi.com/pdf/datasheet/mj21195-d.pdf
https://www.onsemi.com/pdf/datasheet/mj21193-d.pdf
3) additional this older types: MJ15022/15023 200V 16A 250W
https://www.onsemi.com/pdf/datasheet/mj15023-d.pdf
https://www.onsemi.com/pdf/datasheet/mj15022-d.pdf

Are TO-3 versions still available resp.in ongoing production ?

Title says it all ...

I purchased both SE and Balanced essential kits. I’m going to make the SE one but have also decided to go for the Pumpkin so the Balanced kit is now up for sale. These are the 2021 boards. Never even opened the package. For Uk buyers the Balanced essentials kit is currently £178 plus shipping. I’m asking £150 plus shipping.

How important is bracing? Over what panel length is it required?
I bought a BIC America F12. The plate amp was shot so I converted it to passive. The longest panel length is 450mm but the cabinet has no bracing.
To my ears it sounds a little woolly . . . but I paid five bucks so maybe it's just crap?

I’m looking for a commercially built Pass Labs Aleph P with remote. Thanks!

Hello, my name is Aric and I'm currently reading Morgan Jones, taking breaks where necessary to refresh myself on electronics 101. I want to work through some small projects and eventually build my own tube amp. I'm here to pick up any more knowledge I can from those much further down the road than me.

Greettings everyone, I just joined but have collecting and fixing vintage audio for about 25 years. I mostly work on power amps and receivers but have also started fixing older CD Players (mostly Naks) and Technics turn tables.

Thanks!

Всем привет. Позвольте мне представиться. Я занимаюсь ремонтом и разработкой радиоэлектронной аппаратуры в направлении ЦАП, CD плееры, усилители.

Dear all, I am designing a PBTL amplifier circuit around the TDA3220 chip. The datasheet gives this example circuit bellow. I have chosen for a post LC filter PBTL because it says that the inductors can be smaller. The impedance of the speaker I will drive is 2 ohms (quite low). Since I have no experience in power amplifier design my question is:

1. Are there components in this circuit that require to have some minimum specs. Like the components in the filtering circuit after the 10uH coils towards the speaker, do they need to be able to withstand the power (~60watts continuous). And if so, what specs would I need to look into and what would be safe margins to use based upon your experience.
2. I have chosen post filter PBTL to reduce needed component size, but are there any hard pro's for going pre filter PBTL?

Thanks a lot!

Improvement the speaker with flat sandwich diaphragm.

Noticed that a large part of the flat inner diaphragm is large. More than the edges. What triggers a significant resonans.
It is easy to detect finger impacts. This will sound.
Extended voice coil element, which increases rigidity. Using a thick paper, Kevlar and carbon fiber.
Adding a slight weight.

Can somebody please help???

I'm after info on the differences between the Audiolab 8000CD & CDE?

It's obviousy components but what components? I'm thinking of saving the £200 and buying the CDE and spending the £200ish savings on mods.



Any ideas?

I have been looking at various driver options for a straight forward 2-way design with a reasonable driver cost.

This will be a first time prototype for me, so I'll be using an active crossover to learn about the drivers and the crossover configurations.

Ideally, both drivers would be matched as closely as possible in terms of sensitivity, in order to reduce the amount of gain manipulation needed in the DSP.

Targeting a frequency response of ~150Hz or so to 20kHz. The lower end will be handled separately by a dedicated subwoofer.

Currently looking at the following driver options:

Tweeter: Dayton RST28F-4 (Don't particularly like the resonance starting at 2kHz to 2.5kHz as per spec)

Mid-range: Dayton RS100P4 or Dayton SIG180-4 (Higher sensitivity, but don't particularly like the impedance oscillations between 50Hz and 150Hz and the resonance at ~420Hz as per spec)

I'd appreciate any advice and suggestions, especially for driver combinations, thank you all.

I have seach Google for a time now with no luck. Do anyone of you know how to get schematic for DP1?
Best regards

This "thread" details the restoration of a Sony CDP790 and the KSS240 optical pickup and mechanism used in the player. The general procedures and
faultfinding approach may be a help to anyone working on a problem CD player as many aspects are common to many makes and models. The US only version of the CDP790 is internally totally different (the main board) to the US/Europe CDP790 which also seems to go under the CDP209 banner. Something I only found out later...



This particular player was one that had caught my eye in a local second hand shop. For week after week it sat there, unloved and looking for a good home.
Normally I wouldn't have bothered but this one, although covered in weeks worth of shop grime seemed cosmetically perfect. No obvious scratches, the large display window was unmarked and it even had its remote. It wasn't quite the usual abused gear you often find in these places. It was marked up at just under £30. I was tempted but first thought I'd look at the service manual and see what technology and mech this player used. It was a KSS240, no real surprises there and I guess that dates it around the early 1990's. Thinking it would make a nice little restoration project I took the plunge. The guy in shop said he'd test it first and I was pleased to see the VFD display was in mint condition, clear and bright with no dull segments. Popping a disc in and pressing play the TOC was read and the time counter commenced. It plays all the tracks he said, so the lasers good, thats how you test them you know, you see if it plays a track near the end.

And so the restoration commenced. First up was the remote. It was in generally good condition but this whole project was going to be thorough if nothing else. Now to anyone that has worked in a large service department you'll know that a daily intake of faulty remotes is the norm. For "faulty" read dog chewed, cat pee'd, coffee spilt, got trodden on (but it went like that on its own... honest), well, you get the idea. Dismantling remotes without leaving a mark is a challenge, they have to coerced, prised at the correct points feeling where the case is clipped together. The remote was dismantled as far as was possible and all its parts incuding the PCB washed with foam cleaner, rinsed and dried and reassembled. 30 minutes later and one mint remote 🙂

(Worth mentioning is a strange affliction affecting some remotes in that what looks like spillage on the underside of the rubber keypad is actually some type of plasticiser or polymer that eeks from the conductive rubber. Its all gooey and sticky, and you tell the customer they spilled something in the remote... only they didn't... the top of the rubber is clear)

Next on to the player. I'd left it on "repeat" for a few hours (I hadn't listened to it yet) and it seemd basically OK. The disc was still playing after 5 hours. One fault did show immediately though and this was that the tray would often close immediately it had fully opened. One to look at later, probably microswitches needing attention. The next step was to fully dismantle the front panel, removing the PCB behind that housed the display and to give it all the foam cleaner wash treatment. Its beautifully constructed with a small PCB and motorised volume control where the headphone socket is fitted, the headphome level knob actually being illuminated. That must mark it out as a high end player. The front came up like new. I carefully polished the display window inside and out until it sparkled. There were no visible scratches even under bright light on the perspex.

(A word of caution. Some display windows have a thin coloured filter material sheet applied on the inside of the window. If you wash these water inevetably gets behind the two and will dry leaving marks. But this one was just tinted perspex and mint. One reassembled front later and the player was fired up again. It was looking good. Time for the microswitches)

There are two microswitches, one to detect when the tray is fully out and the other fully in. Both are on the loading motor PCB and access is simply a case of removing the two loading motor screws and popping the whole assembly free from the three plastic retaining lugs.





The switches looked OK but further dismantling was needed. The two plastic "tops or paddles" unclip from each switch allowing the contacts to be cleaned.



Paper soaked in iso and pulled carefully through the contacts revealed a bit of discolouration as dirt or tarnishing was removed. I left the switches dry using no contact cleaner.



You can see in the pictures the three gears and the loading belt.



These just pull off and so were cleaned and a smear of plastics grease applied to the spindles. The teeth must be left dry with no lubricant. This grease also serves another purpose besides making the mech super quiet and silky in operation. It serves to "slow" slightly the loading and unloading and so prevent the tray "bouncing" as it reaches the end of its travel. In combination with the micrositch clean this should resolve the original tray issue. And so it proved. I also took the opportunity to measure the loading belt for future reference. Although the original was soft and supple and would stall the motor if the tray held, if a new one were needed it would save dismantling again just to determine the size. The dismantled mech was also cleaned and washed. The magnetic disc clamp "twists" to separate it fully from the frame which I did for cleaning, not wanting to wet the ferrite magnet.

I left it playing again and thought I heard the pickup skip. Hmmm... was this an underlying problem ? The reason the player had been disposed of ? I looked suspiciously at the servo board under the pickup scouring it for problems. One joint on the focus gain preset seemed dubious but was probably OK.



I resoldered it. Problem remained, intermittently appearing. Grrrr.

Next step was to do as I always advise on the forum. Scope the RF (eye pattern) and see whats what. The manual showed 1.3volts pk/pk as the level with a tolerance of -/+ 0.3 volts. As you can see the output was low. Scope on 500mv/div



A lens clean brought the level up to a fraction over 1 volt, just within spec.



I left it playing and again it seemd OK until... the next disc wouldn't play at all ! It would spin up to a million miles an hour and then a few seconds later...NO DISC... message on display. A problem somewhere. The next day it was fine again, although I suspected I heard it skip again in play mode. Time to investigate. I left the scope coupled up and noticed that when the problem happened in play that the RF looked as though the tracking correction wasn't being applied to the lens assembly. The RF was extremely blurred and looked a bit like it does during track jumps when the tracking gain is lowered. Time
to dismantle the mech... again !



Three screws and the whole mech comes out with just one large flexiprint cable connecting it to the main PCB. I poked the pickup with a plastic trimming tool while it was playing (well at some point you have to get the technical hat on and I slipped effortlessly into engineer mode) and suddenly the servo locked and played. I repeated the manouvre and caused the problem to appear momentarily. So, pickup out and ribbon cable removed. I've heard of problems with the ribbons but this seemed OK visually. I cleaned the ends with iso and used iso on paper to clean the slot in the sockets. Next a close look at the pickup. Fortunately I have the kind of eyes that can see the finest of detail (although I can't see a car number plate at more than a few feet away without glasses, I can see the gap in a tape head without the goggles on) and I noticed what seemed to be a dry. Surely not. The picture shows it although it looked much more obvious in reality than in picture. It's the right hand pin in that row at the front.



The solder hadn't taken to the pin, that's how it looked.



I resoldered them all including the ribbon socket for good measure although that looked OK. Quick reassemble and test. All good. Faultless even. I must admit even I was surprised and I'd resigned to getting a new cheapo KSS240 but it seemed perfect now. I finished off by getting a drop of oil into the spindle motor top bearing which with only a millimeter or so of access space because of the platter isn't easy. Again the paper trick was used, this time with a little oil specially for sintered bearings soaking the paper edge. Wipe that through the available access space onto the motor shaft and it does the job nicely.

A quick once over of the electrical alignment seemed a good idea now all the obvious faults were corrected.

WARNING... unless you are confident and sure in your abilities and have the required equipment then don't alter any settings.

The KSS240 has three presets mounted on the pickup. APC (automatic power control) or "laser power", FB which is "focus bias" and TB which is "tracking balance". TB is also more correctly or universally called E-F balance. At the end of this post are two short zip files containing videos of actually performing E-F balance.

What is E-F balance ? This refers to the E and F photo diodes in a 6 photo-diode array on the pickup. Diodes A,B,C and D read the data on the disc. E and F are the two detectors used to keep the beam "on track". If the beam wanders left or right then more or less light falls on each diode respectively. When correctly "balanced" the intensity is equal on each. Alignment follows a specified procedure in the manual which involves putting the set into a service mode (a shorting link) and applying another short between two test points. The TB (or E-F balance) pot is now adjusted for the tracking error waveform to be "equal" above and below the notional centre line. That is the full and correct method but another easier method is to just play a disc and examine the tracking error waveform. When you then do track jumps (changing tracks on the CD) the error waveform appears briefly. By continually pressing track up or down you can easily adjust the E-F balance. A similar effect can be seen by just pausing the player (thanks to stephensank for the pause method). Here the error signal consists of very short "spikes" allowing for adjustment in the same way.

The two zip files show the full method where the error signal is continuos and you have as long as needed to adjust. The second shows the quick method by continually pressing track up and down. You average the effect by eye and with experience can get the adjustment spot on. The quick method shows me deliberately mis-adjusting the E-F balance to shift the error above and below the "zero" line.

(The files play directly in Windows Media Player)



The PCB under the pickup has two presets marked focus gain and tracking gain. With scope connected to the RF and the scope ground on the servos "virtual ground" for correctness the focus bias pot was tweaked to give the very best diamond pattern and amplitude of the signal. I must admit to being very naughty and tweaking also the laser power to bring the signal to 1.2 volts pk/pk.



Adjusting while actually playing is the only way to do it.



A 20 year old pickup is bound to have different characteristics of the lens suspension from when it was new and so I realigned the focus and tracking gain presets. Officially a frequency response analyser is needed. Quite what and how you use one I have no idea. That's frequency response of the combined electro/mechanical servo by the way, nothing to do with the audio side of things. Anyhow, these adjustments have quite a margin but, twiddle without knowing what you are doing and you could end up with a player that won't even spin a disc. The scope was connected to the tracking error waveform test point and the gain advanced while playing a CD. What you are looking for is a very low frequency fundamental waveform begin to appear in the tracking error signal. At that point the gain is backed off slightly to just eliminate the fundamental. Tracking gain done we now move on to the focus gain. Increasing the gain causes mechanical noise from the pickup and so the trick is to back the gain off at the point "white noise" starts to become audible from the pickup. A curious fact is that an experienced tech can actually set the focus bias and gain by just listening to the noise from the pickup. I would guess I can get it 95% optimal that way. The tracking balance pot on the pickup I left alone. Although there is a procedure for checking this the simple test is to perform "track jumps" and in the brief time they take examine the tracking error waveform and make sure it is symetrical above and below a notional zero or centre line running through the waveform centre.

Here is the final shot of the RF or eye pattern. Not bad for a 20 year old player with the original KSS240. Scope is now set to 1 volt/div.



So the mechanical side of things were now looking good. The final step was to remove the main PCB and give it the once over. Arguably this should have been done first but the player was basically sound electronically. A visual inspection revealed a couple of possible future problems. Potential dry joints. The four T0220 package transistors had "joint wobble" when they were moved and it was easy to see the solder cracking around them.

This type of problem is common on any equipment. Also spotted were the output socket solder joints looking well on the way to becoming intermittent.





With those attended too the basic restoration seems complete and it was time for a listen.

(I mentioned the main PCB being totally different between US and European variants. Well the US version uses AD1860 D/A convertors and a single RC4558 opamp while the European version uses Sonys own "Pulse D/A convertor" and two 5532 opamps. The muting is transistor only in the US version and relay plus transistor for the European)

Listening trials revealed what I would describe as a typically bright and somewhat "thin" sounding player. It was up against stiff competition though in the form of my old Micromega Stage 2 and the Stages' successor, a Marantz Pearl-Lite SA-CD. I suppose that outcome is absolutely to be expected although I shall look at future mods for the Sony. The analogue stages use SIL package NE5532's (why couldn't they use DIL) and incorporates both "hard" relay muting to ground and "soft" bjt muting. Something for future work maybe.

All in all I'm pretty pleased to have rescued this old timer. It looks as good as new and is as clean as new inside.

Greetings to all!

I want to ask the advanced self-builders. What will happen if you install Purify 1ET400A modules in NAD M22, which has Hypex NC400 OEM modules. What do you think about this?

Pin of Hypex NC400 OEM in NAD M22



is same as pin of:

1) NC500 - Hypex Electronics B.V.
2) 1ET400A - 1ET400A - PURIFI

NAD M22 has a smps +/-64Volt.

Service manual for Nad M22 with shematic:

NAD M22 SERVICE MANUAL Pdf Download | ManualsLib

Under
McCauley.com
: Products: Components
all known models are still listed, but without datasheets as usual on websites from other companies like this one
All Products | Precision Devices Loudspeakers
Only on facebook are several sheets, but not the ones from their currently website.
Maybe one of the members have several datasheets from several years ago (according their website no new types are published in the last years).
Thank you very much.

Unfortunately this closed thread don't provide the wanted information.
How Reliable Are McCauley Drivers?

P.S.: There are a lot of guys, which have the name "Tom McCauley". But I think the founder of this loudspeaker company is this one:
Derol Caraco & Tom McCauley - Recording - Skipper Wise

Hi guys,
I’m struggling to find a speaker grill for my b&c 10n64w subwoofer. It’s 10inch with 245mm screw hole spacing. Grills are available le everywhere but not with this hole spacing.

If anyone know a source for this, I’d really appreciate it! I’m Europe based, but won’t mind buying overseas

Thank you!!!

Up-dated stock list all these fuses are half price or less, please message us for a quote for any you may need.

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Hey guys first time poster long time lurker.. lol I just purchased a Wuzhi zk-3002 amp based on the tpa3255 and a 48v 10a smps to go with it. I have tried it hooked up to a pair of 8ohm speakers and a pair of 4 ohm and the results are the same. When I turn the volume up to medium/high levels it begins to cut out almost like a bad aux cable would from your phone to a speaker. I have tried it with a Bluetooth adapter as input, my phone wired directly, and with a pre amp in between both. My power supply is adjusted to 48.5vdc and doesn't change when the music cuts out at all. I can get an amp reading later today to have a better idea of where it's cutting out.

The amp has an adjustable gain potentiometer on it from 26-36db of gain and I have tried it all the way down at 26 and somewhere in between around 31db.

Im Jojy from India. Im a passionate speaker builder. Would love to get more knowledge about different types of speakers and amps. Thats why joined in this forum. I had already done couple of projects in car audio and also Hi Fi listening.

The OPU/CD Laser Pick-up of my BeoSound 9000 (MK3, type 2571) has died. So I am looking for a replacement OPU.

The broken unit is a 'Philips VAM1250/21' (see pictures below).
I have searched for VAM1250/21 but have only found a VAM1250 (without /21). And I haven't found information if it is different or compatible.


My questions

• Where can I find a VAM1250/21?
• Is a VAM1250 compatible and usable for the BeoSound 9000 MK3?
• Is the VAM1254 safe to use as a replacement?
• Are there other OPU's I can use?

Any help will be highly appreciated!

Hello to everyone!
I like to build an expander based on tube.
Is there any scheme available?
Thanks

Hi guys, NEED HELP! Does anyone know why my subs are making popping noise sometime thumping sound.
I have module icepower 700AS1 with 1 x 12” 4 ohm woofers.
I found the burnt resister 22 ohm components(see photo) speaker output (+) filter section , Anyone can say problem resistor componence burnt ?

thank you for any thoughts!

Hello,

I would like to share a few amplifier schematics that I have designed. I have been involved in the construction of radio equipment for some time, mainly receivers, transceivers, and measurement instruments. The schematics I am sharing below mark my debut in audio electronics.

It all started with my experiments with a simple Class A amplifier. Due to the current war in my country conditions limiting component availability, I had to use inexpensive n-channel MOSFETs and general-purpose BJT transistors. The circuit was simplified to use the minimum number of components.



This is a Shiklai pair Q1U2 loaded with a current source at Q2U1. The IRF4905 with a 75A current source is somewhat excessive, but I didn't have any other p-channel transistors on hand. You can use almost any MOSFET for U2. I used counterfeit ones I received from AliExpress (instead of IRFZ24).
The gain is set by the ratio of resistors R6R4 and is 4. It's not advisable to increase it further as it increases distortion.
U1U2 requires a heat sink with an area of 800-1000 square cm as they heat up significantly.
Resistor R1 should be set to half of the supply voltage at the amplifier's output.

The maximum power output is 2.7 watts, and the current consumption is 1A. The transistors are installed on the same heat sink without insulating pads.
The output signal is almost distortion-free up to 80-100kHz. The -3dB bandwidth is 300kHz.
The amplifier has fairly low distortion levels, with the second harmonic predominating in the spectrum.


The amplifier sounds decent, but I was not satisfied with its low efficiency of 10% and its low output power. Therefore, I introduced additional feedback, resulting in the following schematic.



The maximum power output increased to 5.6 watts, and the efficiency increased to 23%. Distortion remained nearly unchanged. The spectrum, as in the previous circuit, shows a decreasing trend, with the second harmonic being more prominent than the third.



Based on this amplifier, I decided to make a amplifier working in Class B. The resulting schematic is as follows:



Resistor R10 sets the idle current at 200mA. Using the C4R8R9 allows the output power to be raised to 10 watts.
Distortion does not exceed 0.1% at various volume levels. The distortion spectrum is typical for a push-pull amplifier, with the level of the third harmonic higher than the second. A square wave signal with a frequency of 20kHz amplifies without visible distortion. No distortion typical of Class B amplifiers is observed when the signal crosses zero. The -3dB bandwidth is 200kHz, but starting at around 50kHz, the shape of the sinusoidal signal distorts - asymmetry becomes noticeable. It's possible that using transistors with lower gate capacitance will improve this situation.



Resistor R12 can have a resistance other than zero. I experimented with a value of 0.5 ohms, which has an interesting effect: distortion levels increase slightly, but the level of the second harmonic increases by approximately 6-10dB more than the third. At the same time, the level of the third and higher harmonics remains unchanged. Presumably, the higher level of the second harmonic will mask the third harmonic. It should also be noted that this slightly reduces the maximum output power (by approximately 8-10%).

It's quite possible that these schematics could be of interest and benefit to others.

73! de UR5FFR

For the repair of my amplifier AB Precedence 600 XL, I need a readable schematic.
I found unreadable schematics, low resolution, on the internet.
Please, where can I get/buy a schematic of this amplifier?
Thanks in advanced

I am putting this post up here because have I had a very unfortunate situation where a builder in France has put together an X-Altra MC/MM for use with the above turntable and it hums on MM input. We have determined it is not the preamp. It works ok on MC but not as quiet as it should be.

I scoured around on the web and found a number of places where users have experienced exactly the same problem with this turntable when attempting to use it with an external phono preamp that has an earth (safety ground) connection. It appears the Rega phono preamp works with it. This has a 24 VAC wall wart PSU and no earth connections.

This is the first issue of its kind out of the 80 or so X-Altra MC/MM phono preamps that have been built, but it clearly is an issue with other preamps as well.

Loud hum from technics 1500c = broken unit? | Audio Science Review (ASR) Forum

Turntable hum with Technics SL-1500C pre-amp : r/turntables

Please see this long thread with the same problem:-

Technics SL1500C TT hum with external phono | Steve Hoffman Music Forums

Suppose a second-order low-pass filter has been being tweaked for smoothing amplitude of the woofer’s output at its cut-off region. As fas as I can think, there are two ways to achieve the goal. One is to swap the inductor, Dr1, for a larger value i.e. 3mH to 3.5mH and a little tweak on the capacitor, C1, may be required. The other way, which I have seen in many designs but I am unsure if I understand it correctly, is to add a small resistor, R1, in series with the original shunt capacitor, C1. As I tried playing with simulation software, both methods can lead the result to the goal. But I am still curious which method is actually more accurate/ preferred, please?

Has anyone considered designing and building an FM tuner? From an audiophile standpoint there is probably little to be gained thereby. In the USA, at least, with few exceptions, both the audio and aesthetic quality of broadcast FM material leave much to be desired. However, as an educational project it might be worthwhile.

This design has, for the most part, been coded and verified in ADS and later in LTSPICE. The front end is a conventional 4-stage low gain tuned amplifier; low gain was chosen to avoid high level input overload and to avoid the need for AGC. The LO is a Vackar design and is buffered via a high speed comparator for isolation purposes. Down conversion to 10.7 MHz is implemented with a Mini Circuits DB mixer. Both the RF and LO stages utilize varactor tuning, where the tuning voltage is sourced via a precision 10.00V reference and is shifted/scaled to allow the RF amp and LO to track over 88.1-108.1 MHz and 77.4-97.4 MHz, respectively.

Demodulation is based upon a double conversion scheme, where the first down-convert is to 10.7 MHz and utilizes ceramic FM filters. The second down conversion to 1.0 MHz permits a low noise, low distortion delay line based demodulation to baseband. 1.0 MHz was chosen because it permits the use of easily implementable digital delay, and the carrier frequency is sufficiently high that recovery of BB signals requires only simple L/C filters. Subsequent stages regenerate a 38 kHz chopping frequency from the 19 kHz pilot tone and perform the filtering/matrixing to recover the L and R channels from the L+R signal. The front end sections have been built and tested, although I plan a redesign to implement some improvements.