Just been handed a Pioneer VSX-708RDS (1998).
It has distorted audio only on the R/H channel.
Any ideas anyone?

This is the tone circuit from a vintage bogen amplifier E30. I am a newbie to schematics and am unsure of the value. It needs to be replaced . Thanks.

Why are there only disastrous PCB Versions for TDA7293/TDA7294/LM3886 etc. available?

There are an extremly wide range of PCBs and Kits available for this and similar other monolitic audio amp ICs.
For me unfortunately the position of the copper conductor tracks are absolutely
disadvantageous by all examples, which are to find by Google image search - go to

audio amplifier tda7293 - Google Search
audio amplifier tda7294 - Google Search
lm3886 - Google-Suche

By this high resolution example - go to
F200# Audio Enthusiasts DIY AMP TDA7293 Amplifier Board for sale
you will see, that the positive voltage supply rail and the negative rail goes very close to the signal pads and inverted input pad for NFB. Additional there are only cheap caps for the power supply in use without screw terminals. Consequently a certain standart of sonic quality cannot be exceeded. By all showed images unfortunately this situation I note.
I am almost certain, that nothing of the showed versions from image-search sounds really good (at best like Linn's LK85 in genuine condition - i. e. with original part and wire equipment).

After performed tweacking of Linn's power amp model LK85 (equipped with TDA7294V) I observe an exceptionally enhancement by sound quality due to additional use of caps with screw terminals and change the routing of the wires for the main voltage rails.

According to my requirements four holes would be drilled in the PCB near by the pins 13 and 15 in case of TDA7293/TDA7294 (in opposite of the sensitive area). The cans of the caps must go downward (solder side/bottom side) and the screws for the caps must be screwed from the component/top side.

Then I avoid interchanges between the (very short) supply rails to the sensitive areas and I get the possibility to use top class capacitors in outlines like that from
http://www.audiocap.co.uk/ekmps/shops/audiocap/images/als30a153ke063.gif
or
http://s.eeweb.com/resized/images/r.../2011/02/15/vishaycaps-1297787376_455_332.png
instead low cost high CV versions in "snap in" outline.

Are such printed circuit boards really still not available ??
If yes, is this unbelievable. OTOH - there are too many copies of copies (clones of clones), particularly in far east.

Where is the excellent engineering from early days concerning proper PCB design ??

I'm looking for the first version of the Ventus, the discrete one.
With parts has my preference, but boards alone are also welcome.

Thanks in advance!
Erik.

I suggest, for readability and general tidiness, that there should be a limit to a thread title length of 80 characters - a little less than one line.

//

Hi all

Im looking for a service manual for a Yamaha RX-V585. I googled for hours but without any success.

We have regular power outages in South Africa and it seems like this is what caused the "power on" to be disabled a safety precaution. Currently the amp is stuck in this "protection loop" and a found some info regarding someone that had the same issue. He resolved it by shorting pins 2 and 3 on the EEPROM. Holding down the suggested combination of buttons to get to the "protection state/protection reset" doesnt do anything. The only response I get is by pressing and holding "Info" and the power button. This takes me to the USB firmware update. Other than that the protection state remains.

Im not 100% sure where it is on this amp and dont want to take any chances without knowing for sure. The closest service manual i could find was for the RX-V577 but unfortunately it didnt help as the is board slightly different. Any help will be greatly appreciated.

Regards

Hi all, I've done a search. I found a similar power supply issue thread from back in 2017. It didn't say at the end what he used and if the supply worked.
So I've just built up hood 1969 amp off eBay, getting back into one of my favourite hobby's, I've got spare time off work.
I didn't realise when ordering the kit, no cables or power leads included.
I've done some looking around and found a few bits that I think would do the trick. Just want to make sure I'm not buying the wrong things.
So audio in has 3 pin holes, ground, left, right. I've looked for a lead to fit this and cannot find anything.
Thinking of wiring up this to the holes as the input.

Now the power supply is the main issue. This will be my first attempt at fitting one, so don't want to blow the amp, or fry myself.
The 2 I've found look to be the correct type. I just need a to find an enclosure to case it in along with the amp .

Any advice would be a big help. Thanks.

Maybe of interest: https://www.hifinews.com/content/threshold-prepower

Good day all, can anybody plse suggest modern replacement trannies for a Pioneer SA 508 amp.
The output trannies are 2SD 883A and 2SB 773A. These were the old gullwing type.
Help much appreciated ! I have thought about MJE15030/ 15032 and MJE15031/ 15033. Or Maybe BD243C/BD244C, These might be the best option.
Regards
Jan

Hi there!

I received this ak-450ub and I'd like to reuse the parts. It had a TDA7377 and was advertised as a 200W system, which is way above of what the chip specs says. I noticed that the voltage fed to it was 21v, datasheet says that max is 18.

Regarding the transformer, how many watts/amps can I get from it? I couldn't find an identical one with image search. I'd like to use it with a linear regulator to power a TDA7850.

I have for sale these Dartzeel NHB-108 amplifier boards. I built one for myself with 2 output transistors , I removed one pair and it sounds amazing.
I wanted to build a second one but due to budget cuts I had to cancel the project.
The output transistors MJL3281A and MJL1302A, and drivers are all matched, as you can see from the picture the values are written on the back.
Note that these boards don't have the DC servo circuit. You need to adjust it manually from the pot and is very stable, no need for servo, trust me.
I tried with the servo but didn't like it, it affects the sound a little so I remove it. I found the DC offset very stable within 5 to 10mv
This is he best amplifier I built so far, very musical and also quiet, no noise.
Asking $140USD plus shipping.

Hello, I am new here, I read some guides here while I was also trying to design my amplifier and thought of making an account and have my design be reviewed here.
So, my audio power amplifier is not really mine, I made it while following along Bob Cordell's book on Audio Power Amp. design. Here it is,


It is a 15W amplifier with 8-ohm load. I am having output problems as I cannot seem to meet that 15W requirement. My closed loop gain is 28 and with 570mV input, I should be able to get 15.96Vpk output, enough to reach and go over a bit to the 15W spec requirement but I am getting a lower output voltage. Also, is my +17V -17V supply good or I should go higher? I am somewhat limited to that as I am planning to re-use a 12-0-12V 3A transformer from a previous project. I am also thinking of changing my output transistors (Q12 and Q14) to TIP2955 and TIP3055 as they seem much cheaper, but I do not know how to choose the transistor to be their drivers.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
The design is not far from the circuit from Cordell's, I have my CFP output stage to have a quiescent current of about 100mA, I achieved that by experimenting values on the Vbe Multiplier resistors. The 22pF Miller Cap value, I followed how is it calculated from the book. As for the LTP quiescent current it is at 2mA and the VAS stage is 7mA. I do not have much knowledge on how to do the output network (Zobel) I just followed the typical values mentioned in his book.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
After that, any suggestions? recommendations? or something I should do?
Attached is also the LTSpice Simulation file already included the models I used in which I would also like to thank and credit Cordell.

long time ago I start this threads:
https://www.diyaudio.com/community/...ntegrated-and-power-amplifier-devices.146528/
https://www.diyaudio.com/community/...dels-quasi-complementary-power-output.157430/

Now I am looking for an overview of vintage stereo receivers and integrated amplifiers with much more quiescent current through the output stage than the typical class B value between 20-50mA for quasi - and true complementary BjT power devices and 100mA for both only N- and N-/P-channel power MOSFET's.

A good known example is Tim de Paravicini's design for Musical Fidelity (A1, A100 etc.) - go to
https://www.markhennessy.co.uk/mf_a1/technical.htm
The Designer:
http://www.ear-usa.com/tim-de-paravicini
(Hiraga's "Le Classe A" and Pioneer's M22 unfortunately are power amplifiers without attenuation (volume control) and input selector).

Probably there are many more models in this kind.
Thanks for some advice.

Just doing some light restoration to a newly acquired pair of Yamaha JA6681b compression drivers:

The back chamber has 1/4" thick "felt type" pad and foam that is disintegrated, and no gasket between the chamber cover and the driver.

1. Do I need to add a gasket?
2. Do I need to replace the old foam with open cell foam? Or with another felt pad?



thanks!

A new YouTube doc from Asianometry ... seems to be quite comprehensive, but ignores audio devices like Philips TDA and SAA series.

"Lost" is a subjective term. Maybe Europe decided they did not want to go into the semiconductor market -- too many resources required, and too much effort??? Even US, the semiconductor "leader", outsources most of it fab work to Asia. Cheaper labor there.

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Anyone ever try adhesive circuit board mounts? Would eliminate drilling holes and trying to get them lined up right.

Hello guys,
I am looking for an experienced speaker designer that could have a look at my crossover.
I currently own C-Note's that I built some time ago but unfortunately my woofers have developed voice-coil rub after I turned them too loud on a party.
This inspired me to design a speaker by myself. I like the tweeters which is why I want to keep them and like the idea of having a waveguide for directivity.
So I want to upgrade on the woofers and chose the RS150P.
I looked at other designs using them like the "C-Killa" by Rob Elder which I took inspiration of since my enclosure design, by 1 liter, is just slightly bigger than his.
I adjusted some values for the woofer to make it more fitting for the Paper version. I want to try to keep as many crossover parts of the original C-Note as possible.
Crossover is adjusted for baffle-step. Just trying to check if there is anything entirely wrong with the crossover. The impedance curve looks kinda wonky imo, should I worry about that?



Appreciate any help I can get. Thanks for your time!

Hello everyone,

I've got a MF Trivista 300 integrated I just picked up (for a temporary replacement while my other amp is being fixed) and it seems the previous owner wasn't all that truthful about the condition of his amp. Got to love my luck. Anyway, I find myself in a position that I have to try to fix what I have with the much needed help from you lot.

The amplifier seems to play just fine with no distortion or obvious signs when playing at moderate levels of volume. It is when you go past the 11 o'clock mark on the dial that suddenly the right channel will immediately jump to a very high volume and will not adjust up or down unless the knob is just below a very specific point at 11 o'clock on the dial. The left channel will go up an down the entire range linearly despite the right channel being 'stuck'. Below 11 o'clock they work perfectly fine in a linear fashion and at the same volumes .

Again, this is a very specific spot on the dial where it acts almost like an 'on' and 'off' switch on the right channel from being at normal volume and then jumping suddenly.

The dial does not produce noise when moving up or down which leads me to believe it is not just a matter of cleaning the potentiometer, but something in the preamp section (perhaps?). What do you guys think is the issue and how could I fix it? Thank you all in advance!

Hello,

I'm looking to find a small tweeter by outer diameter. My current smallest is the Vifa OX20, with a OD 33.4mm. But I need something than 30.4mm

Anyone used any super small tweeters for small spaces?

1/"2 dome is probably too small for me. I'm looking for something larger, up to 3/4". Soft dome hard dome. Beggars can't be choosers.

Please advise.

I don't see myself doing anything with these in the coming time realistically, need to make some room and create some budget for another purchase.
Monolith Magnetics SA-9 Amorphous core 3.3K primary - 4/8/16 secondaries / 80ma for 300B.
Excellent condition, like new. In original carton. Location Utrecht, The Netherlands. Can ship worldwide at cost but probably most sensible within Europe.

€700 for the pair.

Getting a new ride and I know i will want to trade out the speakers.

First, I need to get the car. But after that, I am curious how the car measures with a mic

I don't know how much room I have for parts.

I think it would be cool to toss in a tiny scanspeak Be dome. The one with a low FS has been on my radar for some time.


This might work if it fits. I like the idea of a sealed mid for a car door's odd shape.

The front door speaker and the dash tweeter are wired together in a series. So a 16ohm mid would work with the scanspeak if I understand things correctly.

My preference is to not swap out any wires or the stereo. There is a front/rear fade and bass EQ so if I put a bass woofer in back that should help me set a level. The XO is the part I need to design and this is my first passive speaker.

I'm always bewildered by the incomplete dimensional information for these enclosures. Wherever you look, the information is always missing something. For example, looking at the diyAudio store's dimensional information for the 2U Galaxy ALU 330 mm wide enclosure, the webpage states: internal height= 80mm, external height= 86mm, Top and bottom plates thickness= 2 mm. My calculation suggests that the external height should then be 80 mm+2 mm+ 2mm=84 mm and not 86 mm as stated. Which is it??

Lately i want to find out if a power pentode can be used as a low (or even normal) noise preamplifier.
I want to be honest so i will say that what i really want to do is use an RF linear power amplifier as a receiver preamplifier in ;order to use it's tuning system for added selectivity.
It doesn't matter if you are in to RF because the same principle should apply to audio frequencies.
If a power pentode has a low noise floor and it is matched to input and output impedance should work as a preamplifier also regardless it's small signal gain.
Thank you in advance
Chris

soundcraftsmen pm860 1 channel down. can anybody on this forum help find the defect?

Hey guys,
I'd like to lay down my preliminary plans for a "force cancelling PA sub" and get your feedback on my implementation this concept.
It is sort of like placing a pair of ported cabinets back-to-back, with a total depth of 24 to 30 inches.

The concept is simple but has a potential problem (and I don't know if it is a problem) so I would love to hear your thoughts.

First, I will list my "wants":
Scalable, so one or more cabinets, depending on the application: outdoors, or indoor venue such as a bar or a club.
A pair of 12" or 15" drivers per cabinet, one on the front and one on the back.
Ports on the front only
Simple to build in multiples
Mobile cabinet and not too big and heavy
Cabinet depth of 24" to 30", stackable for use in multiples
Needed bandwidth of 30-150hz

Why force cancelling? The reason is many venues are built in such a way that the vibrations from subwoofers are transfers to the building structure. It is problem for DJs and vinyl playback as well as causing the entire venue to vibrate. The goal is to minimize this problem to not have to fix it down the road.

What is the potential problem? Well, here is where this concept may hit a dead end. The issue of the front woofer to back woofer offset that is tied on the depth of the subwoofer, 24" to 30" inches. It will cause a delay between woofers from the listener location. There will probably be a NULL in the freq response but where? What kind of irregularities can I expect in the radiation pattern around the sub? What happens when I use multiples, lets say a stack of 3x3 -- now the distance from front to back woofer is greater than that of single box. Will this create a NULL in the front and rear radiation pattern?
Is it a cardioid type of a NULL?

Most certainly there will be a NULL somewhere, tied to the offset of drivers, but where? Will it be audible in a room? Outside?

This sketch is based on above criteria:



thanks!

Hello everyone. After 50 years in this hobby I am jumping into designing and building my own speakers. My question is, what are the latest software available for analyzing speakers and designing and testing crossovers. What is recommended by the DIY community.

Any possibility of a group buy for Cinemag 1254, round IV?

I began my experience building single ended vacuum tube stereo amps, based on a number of kits, including EL34, KT88, and 300b. I have had great success with each of them resulting in amplifiers that sound fantastic. After about 3 years of bulding several of these amps, I became interested in OTL headphone amps. I have successfully built several of them based on the Morgan Jones design: https://headwizememorial.wordpress.com/2018/03/20/the-morgan-jones-mini-tube-headphone-amplifier/

Specifically I am building the "optimized amp with feedback" (which is the third schematic. For the B+ power supply I use a power supply with a 240vac secondary and full wave rectifier followed by a capacior, resistor, capacitor, resistor and anoter capacitor. The caps are 100uf/450v, the resistors are 1.8k/10W. My B+ voltage matches the spec, around 220v, althought it goes up to around 350v as the tubes are warming up. The filaments are 6.3vac with two 100 ohm resistors in series across the AC out and the center of the resistor is grounded (this is done to eliminate hum). The amp, in my opinion sounds great. I built 6 of them with no issue. For some reason, the seventh one I built has a spark in one one of the output tubes, lasting a fraction of a second and occurs about 3 seconds after turning the amp on. I have tried switching tubes, but the spark occurs no matter what tube I use. Also for some reason, the spark is only on one of the channels - the other output tube never sparks. I have been beating my head against the wall (figuratively of course) to figure out this problem. I measured the voltage of the top plate, top cathode/bottom plate, and bottom cathode (once the amp is warmed up) on both a working version and the defective version and the voltages are all very close to spec. I took the power transformer from the working one and appied it to the defective one and it still had the same problem. I took the power transformer from the defective one and applied it to the working one and it worked fine, so the power supply doesn't appear to be the problem. Once I get past the spart on the defective one, it works fine, but clearly this problem must be fixed as sparking is unacceptable. I am using a circuit board for this amp, that matches the design in the article. https://www.aliexpress.us/item/2251...2e9Bjft&gatewayAdapt=glo2usa&_randl_shipto=US

This vendor also sells a very nice looking case which I use, but I supply my own parts. I decided to build another board and completed it and replaced the defective board with the new one, but the new one also has the same problem. The only difference between the working one and the two defective ones is that I am using an audyn 0.47uf coupling cap in the working one, one of the defective ones uses a solen 0.47uf coupling cap and the other one uses a mundorf 0.47uf cap. I can't imaging that that could be causing the problem.

Any thoughts on how I can diagnose and/or fix this issue would be greatly appreciated. I have been working on this for several weeks and am running out of ideas.

Hi all. New guy here.
I'm having a problem with my set-up and I was wondering if the speakers could be causing it or if I'm the culprit.
The rig:
Acoustat Model 1's 141 Medalion (Not running original sub) Luxman MB3045's and a powered sub running off of RCA's from the second output of a Quad pre-amp.
From there it is fed by the channel out of an Onkyo receiver that I use to power lesser speakers when I don't need to have the full glory of the good stuff.
The problem:
Over a period of time one of the mono blocks develops a crunchy distortion. They were completely referbed and repaired a couple of times and yet the issue persists. I'm not sure that it's the same amp as I've changed where they live and didn't take note of which is which. It's always on the left channel so I'm wondering if the speaker could be causing the issue or if it may be my unconventional setup.
Thought I'd check here before taking the amps back to the repair shop or bothering the folks in the tube amp section.
Any advice would be greatly appreciated.
Cheers.

I got a Crown D-150A for $40, there are not too many modifications out there, the only thing about to upgrade is the op amps
The original op-amps are the ua739PC

according to this video the tech used

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https://www.ebay.com/itm/2838610294...IH1Z77Mr+2n8gej56r15kc3g==|tkp:Bk9SR9SKmrz1YQ
this adapter and the 5532 op amp, however he did not get good result and went back to the originals

Anything else I can use that will yield better results ?

Sold

Hi,

Is someone aware about the supplier of polypro caps for Monacor as well as for Visaton, please ?

thanks

Looking for a single driver build and and interested in working towards a true full range system. Be that speakers and a sub or just a pair of large speakers. I want to use mark audio as they are the most readily available and from what I can tell offer great price to performance. That said Marks product stack is pretty confusing and I'd like advice as to which divers would suit me best (though thinking about supra baffels so I can play around with different drivers though that'll be later down the track). I listen to most kinds of music from metal to opera but mostly metal and at moderate volume levels (my listening comfort level is around 72db). My priorities are clarity, sound stage and to some extent off axis performance. I'd love people to chime in with which drivers and enclosures people would recommend. I've been told by one person that pluvia 11 in the frugal horn XL is my best bet but I've got a list of chores to do before I can have my play time so I've got time to ask around some more.

https://www.morelhifi.com/product/powerslim-6-integra-carbon/

Very impressed by the shallow depth. Please help me understand how this could possibly be deployed, though.

The woofer had the first break-up at around 1kHz. Looking at the impedance curve, the break-up is aligned with the tweeter's resonant frequency. Is this a coincidence or intentional?

There is a second break-up slightly above 2kHz. How does Morel expect this to be used? On the surface it seems like there are some insurmountable challenges building a crossover for this. The break-ups occurs in the woofer's passband and in the vital 900Hz-2.2kHz region. Or do they have some magic to make these unoffensive?

Or you may just shake your head and tell me, "I'll pass"? This is expensive stuff from Morel and I want to see the point.

I am starting on a new project. Two millimeter steel chassie, and now I am looking for a schematic...Is this an ok choice?

Hi folks,

a seemingly wild idea:

to maximise the number of available FIR TAPs I had the idea to run two miniSHARC (or two openDRCs) in parallel, but only use use the left channel in device 1 and only the right channel in device 2.

My question: How can I get the device 1 left output and the device 2 right output combined back into one Stereo SPDIF signal in hardware (without using a PC or mixer!)?

Thanks and Regards,
Winfried

This is an overview of building a Modified Open Baffle Loudspeaker Built Around 4 JBL D123 Drivers.

First some design philosophy that will leave most of you as baffled as these speakers! Sometimes I design around enclosures. For instance, a couple of very solid old wooden pyramids come my way. Not sure what they were used for, but I notice how acoustically dead they are and wonder what I can do with that shape. Though a series of iterative tests an improvements using only my skilled listening and woodworking, I come up with an omnidirectional little beast with an 8" downfiring woofer and 4 silk dome tweeters arrayed on each side of the pyramid. Then I add a false bottom with about an inch clearance for the bass to radiate from. I have built several speakers around variously shaped enclosures and most compare well with the better commercial factory built, computer designs in terms of accuracy and convenience.

Other times, I begin with a driver and build the eclosure to bring out its best. This requires a different attitude. Because I am going for charm and beauty, not accuracy or easy placement, etc. For instance, I have built folded horns for 1950s Electro-Voice coax drivers such as the 12TRX. I wanted the finished design to sound like the most lovely 12TRX in Heaven. Not some modernized edgy cleaned up (or watered down) compromise. I have to add that the magic of these drivers is in vocals and re-creating a convincing stereo stage placement. And in being able to play loud with 5 watts of class a valve power. One has to give up on the idea of really deep bass, accurate cymbals, and handing the inner voices in very complex passages. These drivers can't do that. If you try to force them to try, then they will sound worse because what they can do so well will be compromised. So a folded horn design something like the EV Aristicrat cabinet is called for. Not too big. Perfect for vocals, combo jazz, singer songwriters.

The current design, I just finished building the first mockup for was designed around 2 16 Ohm JBL D123 drivers in parallel per cabinet. So we wind up back at 8 Ohms. These drivers are 12" fullrange models. They have an aluminum dust cap that acts as a kind of high frequency radiator. They are less than 4 inches deep. A 3" voice coil. None-the-less, they can deliver very convincing brass and percussion. My best guess is that they start to fade at about 13.5K and are gone at 16K. Bass probably starts to fade at 80 and is gone by 35. BUT, and this is important, the bass is actual notes and the treble is surprisingly clean. It does not screach; it is smooth and fades politely anf gradually. SO the sound is much more fullrange sounding that it probably measures. I usually give them a bit of a boost at about 50 Hz and 15 KHz depending on the room and placement.

I've read that these JBL D123s were Jerry Garcia's favorite drivers. And it makes sense. They are very smooth and inoffensive drivers with just a small plateau in the upper midrange, maybe 700 to 3K, but just a small lift and generally they are very pleasant sounding with just a bit of added "presence". A cloth speaker grill helps even out this plateau. I could have added a supertweeter and/or subwoofer and some electronics to slice up the signal. But that would have wrecked what is best about these charming vintage stoner drivers. And The Dead's "Sugar Magnolia" would not have sounded and better. Nor would Duke Ellington's "Piano in the Background". No one in their right mind would use these drivers for funk, disco, hiphop, or anything else that calls for more than 20 watts. So why go there? Play to their strengths of delicacy, detail, and smooth easy ear massaging.

To do just that, I went with a modified open baffle design. The top speaker is fully open baffle, but offset in a 2" x 2" flat board. No sides of back. About 3 feet off the floor. It even had a 1 inch by 8 inch slit directly above the driver, so it is really a mix of open baffle and no baffle. Now you would think there would be way too much bass cancellation with this design. Not so. The driver is offset in such a way that it still produces significant bass radiating out toward the side walls. Additionally much of its down-back firing energy is reflected back up at the ceiling. So one gets lots of deep bass coming off the back wall and ceiling. Strange but true.

The lower driver is about 8 inches off the floor located in the center of a large upsidedown triangle over 2 feet tall, 3 feet wide at top, and 16 inches at bottom. It has non-parallel sides about a foot deep, but no top or bottom. These sides focus the bass down and compress it into the floor as well as radiating all the frequencies up and out toward the back wall and the ceiling.

The BIG PICTURE is this: rather than bouncing the sound from the rear of the driver around in a box or tube and waiting for some chosen bass frequency to turn 180 degrees so it can reinforce the front wave, what I am doing is bouncing sound back and forth and all around outside of the box. But I am still getting it to turn around 180 degrees. But not just one frequency. Lots of frequencies. So this design is, as we say in Maine, unGodly effeicient. Honestly, 5 clean watts will make your ears bleed. This is because one is getting nearly the full back and front wave of 4 really efficient 12 inch drivers with almost no cancellation. Try to do that trick with a closed box!

And an added benefit is that the stereo imaging is about the best I have ever heard. There is absolutely no hole in the middle effect even with the speakers 8 feet apart and the listener sitting 5 feet in front of them. This is because of all the sound radiating from the ceiling, floor, and back wall. In fact, the effect is stunning. Vocals seem nailed in place between the speakers with none of the wavering and quavering of more boxy designs. And when a sound is located far off to one side or the other the illusion of space is abrupt and starting. I knw this sound a bit odd, but the only way I can think of to get across the feeling is that most nice speakers are like a warm shower, but these are a long luxurious lazy surrounding jet massage in a hot tub. They are that good.

As it is 1:30 AM, I will wrap this up with a few photos. Later I might add some detailed specs on the design. But I do not think those details are the critical thing. Once you get the idea of how to bounce sound around outside the box rather than insice to get the backwave back in phase, well the rest is a snap and probably has a thousand different implementaion details. I have already dreamed up several more ways to accomplish the same thing. I guess the big drawback so far is that most of these design ideas are fairly large. And have placement limitations. But they are worth a little minor inconvenience, for such glorious, smooth encompassing musical pleasure!

Hi,

I was looking at the VU meters such as this or this.

Can anyone tell me if it's possible to use them with the output from a regular PC sound card? My plan would be to have them mounted on the case so preferably the wiring would be inside the case. Which means I'd need to get output from the soundcard from somewhere inside.

But regardless of that I also can't quite figure out the wiring either. First, I need to split the channels, left and right. Then I need a ground in also?
And for the power supply, it says AC/DC but I'm not sure if it takes DC. The Aliexpress ones mention a transformer that goes from 110 or 220 AC to 12AC.
If they take DC could I just power them from straight from the PSU?

Thank you.

Hi guys, nice to be here.... my first post, so I've got a question for those who may know. I have this amp, which is well known among enthusiasts, and which should be powered by 24V AC CT, so there are three posts for the power wires (24AC - 0 - 24AC), and two diode bridges (for each channel, I guess), one to the left, one to the right.

Now I only have a 5A transformer, 25v and 32v CT. Bigger transformers would set me back a bit too much, but this 5A is pretty cheap.

I was wondering...

1) can I buy another identical transformer and use them both one for each channel? The idea is to rectify the CT current of each with two diodes, and connect them both to each 24v post, with the 0 cables connected together to the central post. That would give me 10A.

2) could I also use 32V? The specs say 24-30v, but the chip can take up to 40v.

Thank you for reading and I hope the question is not too ignorant...

P.S. the caps have already been replaced, if you're wondering: now there are 8 Nichicon Gold 2200uF 63V as opposed to the previous 1mF 50V cheapos, and thermal paste has been added too.

Hi All,

Working on a DD Audio M3c amp that came in with a blown output section.

Damage included:

• Inductor to -Rail +12V Regulator
• 1ohm resistors to the output MOSFETS
• TC4452VAT Drivers
• Output MOSFETS (FDA24N40F)
• and a 10ohm resistor between REM and the Remote bass controller (R169)

Following repair, had audio oscillation when setting LPF pot, with audio disappearing in certain settings also, POT was broken.
Replaced POT (104C), but have audio oscillations when I set the LPF. If I touch the pot shaft I get a 2000 hz audio output at 20V RMS!

Schematic is a good representation of the pre-amp portion of the amp.

If I switch the amp to slave input, it works as expected.

Any advice on how to track this issue down would be appreciated.

Thanks!

Mentmore M100

HI

Ive just been given a a pair of these amps and they work. They were built in 1989 and I think they have never been used. I beleive they are
similar to the TVA10 but with some differences. I have a schematic for the TVA 10 but not for the Mentmore M100.
Does anyone know anything about these amps or where I can get a schematic.

Ps They sound very good with wonderful tight bass.

Thanks

I have all the components to build a DCB1 preamp including a muses volume module and power relay. Got in a bit over my head and I’m not able to complete it.

The DCB1 board is partially assembled and I also have a case with silver faceplate if interested.

PM me and I can provide pictures and other info. If you can cover shipping I’m willing to consider this a diy donation. I just don’t want to go to waste.

Burning Amp Festival returns as a live event (Covid willing!) and online via Zoom. It will be a two day event with Saturday being a workshop day and Sunday the Main Event with displays of all your builds and our keynote speakers.

Check back here, or at burningampfestival.com for updates.

See you there!

-Tom-

Beat way to rid yourself of hearing this near field (or small room,etc)

rear fire into corner ? Down fire?
it’s annoying and some HF junk in my TL stuff is bugging my ocd level more and more as I get picky

Over the next day, I am listing a bunch of electronics test equipment, bare with me and I'll get all the pics uploaded as soon as possible. First I'll list it out, then I'll post pics below.

NO SHIPPING OUT OF US!!!

1. Load bank for testing stereo amplifiers. It is 8 ohms and 500 watts for EACH channels. The huge gold resistors are all heat sinked and the enclosure has two fans in it for cooling. Background: I bought this several years ago for testing WOPL Phase Linear (500 wpc x 2) amps after gutting them. I bought it from a guy who was helping settle James Bongiorno's (Marantz, Dynaco, SAE, SUMO Electric, Great American Sound Company (GAS), Constellation Audio ) Estate and they were liquidating some equipment and this Load Bank caught my eye since I needed one, we negotiated the price and he shipped it to me. Well, this was James Bongiorno's load bank out of his shop during his engineering projects. I believe he built it for testing some of his famous inventions. It does have some other functions like Input Signal shorting switches for checking Noise etc... I used it for years set up for 8 Ohm 2 channel and it performs excellent. Plug it in to the wall and you have dual Boxer Fans with on off for keeping the monster resistors cool. If you look closely, the enclosure he built to house them looks oddly familiar, kinda like one of his GAS amps. He may have used part of a chassis. I haven't really played with it to see if it operates like the switches are labeled. 4 Ohm - 8 Ohm 16 Ohm and shorting. Heavy Duty built to last, great history $400 plus $30 shipping by fedex.








2. Restored W10MT3W 10 amp General Radio Variac. Powder coated, new meters works perfect. My Go-To Variac This is the model with the Wattmeter. Correct dual scale Wattmeter face. This one will last another 50 years. 1 year warranty. $450 + $25 shipping by Fedex.









3. Variac- Restored W5MT3AW $375 with $25 shipping


SOLD









4. Owon 60MHZ 2 channel Digital Storage color O'scope. PDS6062TB. Very Nice. It is Portable with battery backup, comes with power cord and two X1/X10 probes. It works excellent and you can store settings, along with Auto Measure and many functions. Very easy to operate, excellent condition. Manual available online. 90 day warranty. Compare apples to apples when researching online. The PDS6062T (about $175) and does not come with battery backup whereas the PDS6062TB has the OPTIONAL battery. This one with battery option can sell for more than $300. $250 with $25 shipping.






5. Leader 775-5D 75 VDC 5 amp Power Supply #1 Pics coming You can hook up 2 of these in Series Configuration and have +75 VDC and -75 VDC $225 plus $40 shipping

6. Leader 775-5d 75 VCD 5 amp Power Supply #2 Pics coming You can hook up 2 of these in Series Configuration and have +75 VDC and -75 VDC $225 plus $40 shipping

7. HP 6033A 0-20V/0-30A 200W Power Supply Pics coming $225 plus $40 shipping

8. WaveTek Model 134 Sweep Generator Pics coming $250 plus $40 shipping

I ran into some ALPS and Panasonic motorized-potentiometers... I don't know if they are any good...

any idea appreciated 🙄
pics:


both side by side:

ALPS (side view):

ALPS (top view):


Panasonic (side view): (there is no Panasonic printed on them but I'm told they are)

Panasonic (top view):

Hi im trying to design a box for this sub, but i dont have info on it, and dont have a manuel since i got it used, and i was hoping some of you could help me find some specs on it?

What are they talking about? Sound maybe?

I'm using my Klipsch Quartet (the heritage 8" woofer "Forte" design with a passive radiator on the back) in a very compromised location. Recently moved into a small one room (studio style) guest house to help family and have to put speakers and stereo into an 8 foot wide closet area. No other wall space is available. The speakers front baffles are pulled out in front of the opening, and there are no doors or coverings on the front.

I know it will never sound good, and I do plan on demolishing the closet, but I want to keep using these speakers. For the time being I'm looking for a way to eliminate the passive radiator on the back. I could construct small boxes around the passives with dampening material, but I thought I would ask the group if there are better strategies. The closet material is textured plaster, and I could line the interior of the closet with dampening material. Any thoughts?

I obtained this curve from another site, it's for an Infinity RS 3A. The crossover points are 600Hz and 4kHz. Apparently they're known for eating amplifiers. Full understanding of impedance curves apps a little outside my wheelhouse.

I'm going to modify them to allow biamping - one amp for dual woofers under 600Hz, one for over.

My first thought was to use a Threshold s200 for the bass, the VFET for the rest. But others have advised me to flip that - the VFET for the bass, the threshold for the harder to drive mid/high end.

I believe the threshold is 100W/channel and the VFET 10W/channel. 10W may be a strain for any part of the system.

I thought I'd ask the gurus here, since both amps are Pass pedigree and I trust you guys.

Thoughts?

My amplifier stopped working out of nowhere and i cant figure out the problem. The clip light is always on, the protect light is flashing, and when the protect light has flashed 10 times, the power light turns on for a second, then it all starts over. i cant figure out the problem. i would be very glad if anyone has an idea of what it could be. i checked the obvious things like ground etc. The amp is a swedish amp called basshabit 600.1. Class D amplifier. I have never seen this issue before. Any speculations at all would be very helpful. Thanks

Hi all,

I need some help debugging a Sonus Faber Musica amplifier. I have the service manual (attached). I followed the instructions for setting DC offset and all worked fine. When I tried to set the quiescent voltage per the instruction on page 4, the left channel was not a problem and with the right channel no matter how much I turn the pot the voltage measired stays at 0mv.
The amplifier works and both channels play music although the right side of the heatsink where the output mosfets for the right channel are localted does not heat up as much under normal operation. I assume this is due to low bias current on that channel.

Can anyone assist in what could be the problem?

Service manual Musica (1).pdf - Windows Live

Thanks
ronenash.

It's here:
https://www.ti.com/product/LP2950
It's the TO-92 3.3v fixed voltage reg.
I'm using it for for various 3.3V low-current DAC projects. Such as the V_DDD pin on dacs.
The datasheet for the LP2950 is bit confusing for fixed-voltage applications. I am assuming, just drop it in. No input or output caps are needed nor is some R between leads -- correct?
Or how would you tweak its use further?

I want to make some full-range speakers which can go reasonably low, lets say F3 in 40smth Hz to avoid the need of subwoofer

The main req:
-Fullrange...
-Low cabinet volume - space is at premium, also smaller cabinets are cheaper to build and have much better WAF. Probably go for MLTL or similar long and tall
-Up to 150EUR/USD per speaker driver, so up to 300USD/pair
-Prefer quality over SPL

Nice to have:
-As much range as possible, my hearing is up to 14kHz, but the more range, the better
-Cheaper than 150USD per speaker driver.
-6 inch+ driver size

I am leaning into Dayton PS 180 or smth MarkAudio, but literally lost which Mark's driver has good combo of price, range, sound quality and recommended box sizes.
Definitelly not into 100+ liters boxes

Which driver and which box to choose?
Please help me with brainstorm. Thank you!

EDIT: another advantage is the lack of some sort correction circuit or a need for heavy EQ

I´ve got a Hifonics BXi 8000D here, it breaks way before reaching it´s rated power.

I measured these waveforms at the output section of every bank, there is only one FDA59N30 per bank in at the moment.

Railvoltage reaches +/- 124V

The amplifier builds up heat, as it goes, without any load.

So my question is if these waveforms are fine?

Here is a small and simple project.
Two 9V Batteries power one opamp to give a Gain like 5.
That is all that is needed for HiFi amplifier.

Since I got a bit addicted to 3D printing and I yet have to try a line array speaker, I put this on my project list. And I hope it will be ever finished, too🙂 I really like the 3FE22 driver and I tend to use it quite a lot in my other projects. So I imagine a 3D printed enclosure for this driver (or for a pair or quad) that could be easily stacked to form a line array. The 3D printed enclosure can be made light and strong and non resonant with minimum effort. PLA should work for home use and I am at the moment getting some really good quality prints that would not need any surface finish. I imagine this being held together maybe by hidden M4 threaded rods or long screws with buried square M4 nuts.

The basic plan is:

1) order some 3FE22 - check🙂
2) design a 3D printed stackable enclosure and a bottom plate - WIP
3) print many of them
4) enjoy the line array sound

The tested STL models will be of course shared here. This is a long term project, but my 3D printing skills are finally high enough to start the project🙂

I recently purchased a pair of ML N 33h mono amps from a friend whose father kept them in storage for several years. I plugged them in for a test yesterday and they seemed to enter standby mode and turn on properly but did not push any power to the speakers. After about 20 seconds one of the amps started to generate a crackling noise from the speaker and emit a puff of smoke. I turned the amps over to discover they were both leaking a dark sludge out of the bottom grill. I took the grill off expecting to see a bloated capacitor but the sludge seemed to be dripping out of some diodes as you can see in the attached pics. The amps are probably overdue for a complete re-cap, has anyone had experience servicing this model?

Good day !

I have the possibility to get two ATC SB75-314 SC ( 8 Ohm ) in mint condition for a total of 1000€.

Now I'm thinking back and forth if I should buy them, because I'm planning an custom studio speaker project anyway...

What would you guys suggest me ?

ATC SB75-314 SC or something like the Volt RV3143 ?

I would pair them with some ATC SM75-150 I bought today.

Kind Regards
Alex

I would like to design a waveguide for this tweeter so I can cross it over low with the SB17NRX2C35-4 (https://hificompass.com/en/speakers/measurements/sbacoustics/sb-acoustics-sb17nrx2c35-4)
I am a little worried about the XO so
1. Should I be worried about the XO point in the first place
2. If so would a waveguide be the best fix
3. If so should I design one and how, or are there any good pre made waveguides that would fit this tweeter.

Greetings Friends. I've been tinkering with the Shure M65 Phono Preamp DIY Kit from ZeroZone and have found it to be an excellent performer, especially for the price. Depending on enclosure and tube selection, I can build one for $200, give or take. Here it is in a Hammond 1458 VE3.


I like these boxes because they're well ventilated and easy to work on (the end plates are aluminum) but maybe that good ventilation is letting in too much RF.

As you can see see the PT is close to the board and the 12AX7 tubes are in plain sockets. I have replaced the plain output wire with shielded cable since this pic was taken.

At my home this preamp sounds great and has low/non-exist noise. However, at my buddy's place:

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He's got cell phone antennas almost directly across the street from his house and this noise is present in his guitar amps as well, but it's much worse with this preamp. I assume that's because of the high gain in the circuit. A new Schitt phono pre is virtually silent in the same system.

So what should I try? Would shielded tube sockets help? I'm not sure they'd fit the box. So far we've tried wrapping the box in copper tape, EMF filter on the power input, nothing. Any ideas?

Thanks!

As per title, does anyone have any angel hair
Need about 200g
Also some Herdwick matting. Qta systems used to sell it, but no longer exist, and can't it anywhere.

Thank you.

Hi, this is my first post here so go easy!
I was hoping someone might be able to assist me with a biasing issue I'm having with my Sony TA-FB920r integrated amp. The left channel died a few years ago so it went into storage as I don't like binning things that could be fixed. I read a lot about common issues with these amps and seemingly bias drift can lead to the output stages failing. Sure enough, both output MOSFETS dead short, amp stuck in Protect mode. I removed both dead devices which cleared the protect mode so I then removed and tested transistors and other components in the various stages prior to the power amp, replaced the o/c gate resistors and finally the pair of MOSFETS.
The channel is now working but I cannot get any bias voltage across the bias test points, it just sits at zero Vdc at any point on the trimmer. I don't want to leave it as is and blow another set of (expensive!) output devices so I must have missed something? Any help would be greatly appreciated 👍

I need waterfall and others. Better from the box. Mid driver plans for active 3way. SB17NBAC35-4 not so good sensetivity but looks good oweral from what i saw in the internet and cheaper...

Hi guys been a while!
well i was diving in to these style of planar magnetics. (mainly because of the ability of low resonance) because i wanted to make something that could be used with my planar magnetics bas/mid panels that sounds better or with a dynamic woofer (so efficiency is s thing) and since i buy a shitload of magnets with one of the members here 🙂

so i made a small tester first since i did not have enough magnets to go beserk.


Part one : Building one
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Part Two : a tune with the 1 version i got and some measurements
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Part 3 : another tune but now with 2 and some adjustments i would like to make.
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greetings Joppe

Hello--

Early this year, I completed my first "from scratch" tube amplifier build. I used JE Labs 2A3 Deluxe schematic. Prior to that, I had only built kits (Audio Note Kit DAC 2.1, Bottlehead phono stage, Bottlehead Crack).

The JE Labs amp sounds great (to me!), but as I develop a deeper understanding of the ins and outs of tube amplifier circuit design, I suspect that I could do a lot better. (Those of you who hate two-stage driver circuits and/or 2A3s being driven by 6J5/6SN7, I've read plenty of your posts and am sympathetic to those views.)

I borrowed a rudimentary oscilloscope from a friend and, during my short time with it, observed asymmetrical clipping near maximum output volume using a Type 76 tube. I'm guessing that that had to do with the 6J5 operating point but I am not sure.

Two issues that I want to explore (beyond making sure I have the fundamentals of the operating points down):
- Global negative feedback
- Lowering gain

The circuit can be found here:
JE Labs Arkiv (up to 2008): JE Labs SE300B Classic and Deluxe

But first I want to know if I'm understanding the operating points correctly. I'm attaching a few images illustrating the following:
- Type 37 operating point (input tube)
- 6J5 operating point (driver tube)
- 2A3 operating point

I hand-drew the type 37 since Universal loadline calculator for vacuum tubes - Vacuum Tube Amplifiers - DIY does not support the type 37.

The type 37 is biased at -2.2 V and swings between ~30V and 75V, with quiescent current @ 2.2mA.

The 6J5 is biased at ~-70V, the plate swings between 240V and 320V, and has quiescent current @ 3.18mA.

The 2A3 is biased at ~-50V, the plate swings between 270V and 420V, and has quiescent current @ 56.8mA.

I determined the quiescent current by dividing the voltage at the cathode by the cathode resistor.

The "Universal Load Line Calculator" shows that the 6J5/6SN7 operating point is pretty awful. It may actually be worse than the chart shows, since I am unclear on whether or not the "load" that I enter into the "Universal Load Line Calculator" should just be the anode resistor (22 kOhm) or the anode resistor + the cathode resistor (44 kOhm). If I use 44 kOhm, the load line is really atrocious.

6J5 Operating Point?
At this point, I'm not sure what's preventing me from changing the quiescent current of the 6J5 to ~6 from ~3 mA. On the load line calculator, that change moves the 2nd harmonic distortion from 4.39% to 1.22%. This would simply involve modifying the cathode resistor (I believe?). But if I do that, do I compromise the operating point of the 2A3? I'm not against also modifying the 2A3 operating point--I just don't know what happens with the 2A3 if I change the operating point of the 6J5.

Too much gain? Negative feedback?

As I mentioned, the amp sounds great, but I believe I have too much gain. My DAC is ~2V RMS out and the volume control on the amp doesn't need to go much higher than 10 o'clock for things to be pretty loud. I suppose that means I could implement some global negative feedback into the circuit to control that? It would be a fun exercise to implement a switch which would let me turn the feedback element on/off at will to see how it affects the sound.

Otherwise, would moving the overall operating point of the 6J5 "to the left" accomplish a reduction in gain? Or, just by virtue of the tubes used, is the amount of gain present in the circuit set in stone?

Other options?
Obviously one option to pursue is a CCS for the 6J5 and use it to establish a constant operating current of ~6 mA, which should keep it (for the most part) below max dissipation.

For those that want to suggest I scrap it and start over with a single-stage driver--eventually I would like to do that, but for now, I want to move incrementally and see how changes to the circuit affect the overall sound and performance.

Thanks for your time!

Hello--

I know there are a lot of posts about this. I've read them over the past couple days and am still having trouble formulating a plan to correct an issue with my latest amplifier. It sounds great but am hunting down a 60hz buzz I can hear from the speakers--not very loud, but loud enough to hear from the couch.

In particular, I'm not sure I understand signal where signal in / signal out / potentiometer housing / chassis fit in. Am soliciting advice so I can minimize time wasted chasing this down and try to educate myself.

On the bench, when this was all just a mess of sockets and wiring, I could easily ground every connection at a single point. It was dead silent. Transferring it to the chassis, I haven't been able to easily accomplish that same approach. An extra challenge to this build is constructing the amplifier out of a chassis with separable top and bottom, and have wires which need to connect from bottom to top and vice versa.

Attaching a diagram of my power supply and grounding scheme. The line on the right hand side is a small length of copper wire. This is a 45 amplifier driven by gyrator-loaded 6N23P. I am using Rod Coleman regulators. So "Cathode x4" is a bit simplistic, indicating the following:

• 2x 6N23P cathodes connect there as separate connections
• 1 wire bringing the left 45 cathode + cathode resistor + cathode decoupling capacitor + grid leak resistor
• 1 wire bringing the right 45 cathode + cathode resistor + cathode decoupling capacitor + grid leak resistor

TheBartola gyrator board grounds (2 of them) also connect to the bus bar.

From there, a single wire goes to a terminal strip which is connected to signal in (1 pair of RCA, 1 bluetooth PCB module) and signal out (the output from my Alps potentiometer, which has a metal housing). I have a DPDT switch to toggle between RCA in and bluetooth in. Bluetooth is L-C-R molex.

I have the potentiometer housing grounded to the bus bar, as you can see, and because of this, the chassis is also connected to the bus bar.

The IEC inlet ground plug is connected to chassis near the IEC inlet.

Heater center tap is virtual, constructed with a pair of 220 ohm resistors.

Not pictured: bleeder resistor across C4; 30 ohm resistors between rectifier (+ and - ) and C1.

My thinking is that I need to correct C2 -> C1 and make it C2 -> C3. That seems to be the correct approach here. But is that all I need to eliminate the buzz? I feel like there's something I'm missing involving the signal grounding and/or heater CT.

Really appreciate any advice!

Im looking for a service manual for one of these if anyone can help please?

Hello all, I'm looking for a schematic for a pre- SN 3001 Triplett 3423 tube tester. If anyone has one they can post or knows of a source for one I'd appreciate it.

Perhaps this fits in the FAOW or Mofo threads but at this point it deviates a bit.

I am playing with some more flea-power ideas and was selecting a front end to add some gain to my mini-mofo.

And in the spirit of throwing stuff to the wall and seeing what sticks, I got the idea that perhaps we can replace the mofo biasing network and the input cap with a JBOZ style input stage. You can see what I came up with in the attachments below.

We basically have a JBOZ kind of input with its mid-point set at the biasing V for the output mosfet (4.5ish V). By removing the coupling caps, we bias the mosfet. But at the same time we significantly limit the undistorted output because the midpoint is set asymmetrically very low. Gain and biasing is configured by changing R6 which makes everything a function of the PSU V.

In the attachment, with 0.15V input the amp is already starting to clip. Green is Vin, blue is Vout, red is power at the load and cyan is power at the mosfet

The J113 is running at around 15mA and 100mW max with a 20x gain, while the IRF510 is biased at around 450mA and starts clipping at just below 3V p2p (18ish W peak), which is ~1W of output (0,5ish W RMS)

With a 12V PSU, the gain was 8x at 7ish W peak on the mosfet.

One thing to note, is that the positive swing probably has to be limited with a couple of leds or something, in case someone forgets that this is a 1W amp and fries the mosfet because of the larger headroom on the positive side. Of course we could limit the PSU too (we probably won't)

Also, biasing is sensitive to R6 changes, so it probably has to be split to a resistor plus a trimmer for better control.

Can you please review my idea?

I'm trying to upgrade my marantz receiver (replacing regulators and some caps).
Found the schematic and values.
Marantz is using standard capacitors around their dac's. I'm reading a lot of suggestions around different en botique capacitors.

Are there different capacitor solutions/types regarding?

• VREF
• TVDD
• AVDD

I spent a torid time yesterday turning a working XO into a non working one. I wanted to alter various values and so had the thing on the bench and plenty of desoldering old and replacing new components in. And I somehow made a mistake. So spent rest of the day trying to fault find. I had no sound out of it....just some kind of feint music from the tweeter. Desoldered pretty much all I had done to be able to see all the traces clearly. Turns out I had a broken track on the ground circuit.
I have REW and DATS V3 and was assuming given greater knowledge how to use this gear I could maybe test an XO to see what's happening without having to keep pluggin it back into the speaker and amp?

Anyone got one of these, in working condition, they are willing to part with, for a reasonable sum?

Thanks!

Anyone have one of these to sell by any chance?

Buyer located in the UK.

Ok, I'm learning so go easy on me! I've assembled a PCL86 amp using a boost converter and buck converters for the heater and HT powered by a 20a laptop charger.

I'm just using a plastic box for the chassis to experiment and will build a proper chassis with a wooden enclosure once I'm happy with everything.

I've was initially following this schematic with PCL82



But then changed to this one


After building the first schematic, something was clearly wrong. On testing, the audio signal was coming through the speakers for a few seconds at the time I'm before bring interrupted by a short squeal/blip noise which would keep repeating.
I tested the voltage on HT tea and noticed that it was going from the correct voltage and rapidly dropping away when the blip sound was heard.
The LED on the boost converter unit was dimming in time with this

I decided to rebuild using the simpler PCL 86 schematic and found the same result.
A suspected that the boost converter may be faulty so ordered another one.
I replaced it but the problem is still there.

I've tested the voltage with the valve in circuit, the speaker connected but without an audio signal input and the voltage is stable.

As the problem persisted with the second, rebuilt circuit, and the boost converter is new, I'm not sure where to look to troubleshoot. The only thing that has stayed the same are the smoothing capacitors after the boost converter. I've checked these as per the schematic and it looks right.

The the heater supply coms via an LM317 step down converter. I bought a ready built module for this, I intend to build the slow start circuit at a later date. I have noticed that the heaters glow white hot for about a second on startup. I will definitely be incorporating this.

Here's a video of what I'm getting. I've only rebuilt one channel for now. You can see the speaker popping. It stops when I switch off the power supply.

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Thanks!

Hello,
I am currently designing a VCA based on the That 2180.
I am gonna drive the control ports directly with an opamp as specified in the datasheet. The question is what would be the "best" opamp for the job.
It needs to be quite, have a low output impedance and needs to be fast enough.

The datasheet mentions the ne5532 but in some design notes they even used the ad797.

I am using 2 VCA's and drive both of the control ports so I would need 4 opamps. Would be nice to use dual opamps (1 dual per that 2180)
so the opamp shouldn't cost to much also.

Ad797 and lt1028 are good but single packages and they are bloody hell expensive.

So next up in line would be the lm4562. (the same as lme49720?)
It's low noise/high bandwith/ low output impedance... looks good I think.

Ne5532 is also still possible but I think the lm4562 will be better and have lower offset voltages.

Any suggestions are welcome

Hello everyone, I have a pair of W8-1772 and I want to make them a speaker but I hesitate between a Dallas II or a MLTL. The look of plans proposed by Tang Band do not please me. I also heard about the design that Bob Brines made for this driver but I don't see how to find it now that Bob is retired. If you have any opinions on the matter, don't hesitate and if you have any ideas or proposals don't hesitate either.

Seb.

<moderator edit: removed advertising for translator>

UPDATED THREAD
This is the end. Now it is because I have found something that will retire me and I really want to do it.

On the shelf I have lots of high quality and some of the best units for future projects that now won't be build and I have to sell them to make room, money and to get a deffinitive retirement.

For sale:

Audiotechnology Flexunits 10 A 77 25 10 pair. SOLD

Audiotechnology Cquence 18 H 52 17 06 SD - SOLD


Shipping and PP fees not included.

You can PM me your offer if you will combine more items I'm selling. Make a search because there are a lot.

Does anyone have a model number for either the Analog or Coaxial cable that connects the Sony CDP-CX255 player to the Yamaha RX-V1 Amplifier?

Looking for Naim CD5 and/or CD 3.5 CD player schematics.
Naim keeps a tight lid on their schematics. But if you've got these and can spare PDF copy (copies), much thanks in advance!