Lately I've done a lot of reading about how to decouple the power supply rails of opamps. But I'm still not sure, so now I want to know once for all, what is the right way to decouple the op-amps?

Let's assume I'm building a preamplifier circuit using a few NE5532 opamps (or similari). From that I learned so far the usual way to do this is to put two electrolytic capacitors at the the board, preferably close to there the PSU is connected to the board (to minimize that ripple current enters the signal ground). And then maybe also two smaller ceramic caps close to them as this;



Then, decouple each opamp power supply pins. This is what I'm unsure of how to do, but I be think there are three main options to choose from here. The first and simplest is to put a ceramic cap of 100nF between the two supply pins at each opamp. Like this;


The second option B is as suggested as almost all datasheet, one ceramic 100nF cap or so as close to each supply pins as possible, then to ground. The downside this this as that I be leave the signal and power supply ground should be separate at the board or very great care has to be taken with the layout, star grounding etc... So that ripple currents from the decoupling capacitor can flow through the signal ground.



The third C option I've seen is to put a capacitor as close to each supply pins as possible and the other rail, like this. This makes the distance from each power supply pin to decoupling capacitor shorter than in option A.



Option A and C has the advantages that no extra power ground is needed, simplification the board layout a lot. Question is if that is enough decoupling? Of course let's assume NE5532 (or similar BJT) op-amps and audio frequency use. And is C any improvement compared to A at all? Maybe overkill but ceramic caps are quite anyway.

With the gain off my subs have low humming bass and gets louder with SSF. If filter is all the clockwise it goes off but gain won't work can't barely turn gain up at all because subs are moving very low unless SSF is at about 35hz its the loudest with no gain

I have a Nady amp model xa-900 im working on. I need a schematic or service manual. I found it uses 4 each of kts301 thermostats. I found 1 open on each channel. I've replaced them but have both channels in protect mode. The +70 volt and -70 volts b+ is good in all collectors of output transistors. i have the +12 volts and +20 volt dc also. The pcb is labled +90 & -90 vdcom the rails reading +70 & -70. I would gladly pay for the schematic and cant find one anywhere. if anyone has it please contact me. Thanks Craig

Im new to car audio, and I'm getting two 10s to run on 1200w, planning on wiring parallel at 0.5 ohm

What are some quality amp brands? I don't know what's good and what isn't, I've heard good things about taramps, but others have told me they suck. Also, their only 0.5 ohm amps have 3000w or more, which is too much power for my application.

Any suggestions?

I bought this cable to redo signal wiring in my preamp due to the noise and crosstalk. The shield is going to be connected to the 0V of the preamp but only on one side so I am not creating any ground loops. My question is, how do I terminate the shield on the side that's not connected to anything? I do have to expose the signal wire and also strip some of the insulation from the shield but at the same time I assume that the shield should cover the signal wire almost to the end. I just want to avoid any strands touching anything and creating shorts. Any tips?

I repair the PS in this amp,all channels playing good audio but it keeps going in and out of protect.I did not see no dc offset on the channels .When in protect pin 3&4 goes above 4v in the 494

Any suggestions?

I was looking for help with regards to connecting a ribbon coil to my crossover.Should the coil be connected from the inner foil to the post positive or the outer foil to post positive? as you see in this photo the inner wire is connected on the left side and outer is connected on the right side. does it make a difference? the speaker crossovers were connected opposite.the positive speaker post goes to the left side. thanks for any help.

I recently received a TA7801 along with two subwoofers in the factory box, the amp didn’t go into protect, but had zero gate signal after further diagnosis, and I am unfortunately not experienced enough in amps to know where to trace it to. Any help would be extremely appreciated!

This is a request for anyone who has the the gatefold of this double LP in excellent condition.

Reason being I have the 2 LPs, what I don't have is the gatefold artwork it was stolen, a long story I don't want to get into. I will happily pay for a quality colour copy of both sides in a large size and postage in a stiff tube. I've always wanted to find a really good graffiti artist to do two walls in a music room. Down the road in Toulouse there are many.

Thanks in advance if you can help.

I have 8 NOS KEF Uni-Q coaxial drivers and one KEF LF driver that I'm looking to sell. In the bunch there are 4X SP1596 8in coaxials, 3X SP1588.2 6.5in coaxials, 1X SP1535 6.5in coaxial, and 1X SP1537 6.5in LF driver. One of the SP1588.2s has some minor blemishes on the cone (pictured below). They are very small and hard to see unless you catch them in the right light. I don't think they would affect performance. Otherwise they are all like new. Asking $75 USD each for the 8in drivers and $50 USD each for the 6.5in drivers. Volume discount if you want all.

Hi,

would you please have a look at my hand drawn scetch? I've got the power transformer of an useless, hence scrapped Hammond S6 chord organ. The HV secondary nominally is 285-0-285 Vac. My idea is to use it as the PT of a PP amplifier with 807's. The required screen voltage is 300 Vdc. Can I just connect the input choke to the CT terminal in order to get this voltage without excessive dissipation losses? How do I calculate this choke?

Thanks in advance and a happy new year @All!

Any idea what is this white stuff?
Hopefully it's cheap and widely available

Just got in a new (to me...) acoustic musician amplifier by Behringer. The reason why I bought it is due to its separate channels for Instrument and Mic, along with separate digital effect systems on both channels. Plugging in for the first time, with volume set low, on the Microphone channel I notice whenever I connect the mic cable to the microphone the amp goes POW!. Whenever I switch the mic on/off slide switch - that one on the mic - POW! Different make model mic - same. I thought this is ridiculous...No other XLR input on anything I've ever owned has done this. I searched for the 48V phantom enable switch - no dice. Then I searched for a schematic - found something on my amps bigger brother.



Why did they think it was a good idea to pull both balanced mic lines high only on the XLR input? To +15, never mind 48 - a little something better than nothing? I dont mind going in and hogging out R7 and R5, but before I open the box, I'd like to know Why?

Uh, people dont use dynamic mics anymore? People dont mind a big "KaPoW!" coming from their amp when they switch their mic on and off? Some juice for the case when someone plugs in a condenser is better than none? Mics these days all have built in preamps, which need at least 9V phantom power - those old Shure SM57s arent the design target anymore?

Anyway, I can see what's the work to be done ahead of me. Feels strange to be this out of touch with modern, yet 15 year old mic input designs.

hi just got the above deck - ive got loads of headshell bolts but non the correct thread -any help please

Maybe the LTP solution is simpler than normally supposed. The classic solutions are

• Special power supply (e.g. negative leg)
• Unequal load resistors
• Active tail
• Inductive tail

However musing over data sheets the thought hit me. The 6922/6DJ8/ECC88 really likes low Vp-k so why not just use that tube with a really large tail. It has low rp so doesn't need huge plate load and it likes running with Vp-k under 100V leaving plenty of voltage for a goodly tail.

I've been given some equipment to sell for a project I take part in and all is ok except a fault on the Denon PMA 540 amplifier. It plays fine through both channels via the main inputs (Phono, aux, tuner, CD) but there is almost total loss of volume on one channel when either of the two tape inputs are used. It seems odd that both of the inputs are out of action. Ive tried cleaning the sockets and I can't see anything obvious within the amp. Any ideas or pointers would be most welcome.

I'm experimenting with a DBX 234 crossover to set the xover frequencies before to assemble a fixed frequency crossover. I want to do the experiment with my usual listening chain. My current tube line stage doesn't like low impedance, and based on experience, I think it likes at least 50KΩ.

There was something strange when I first tried the DBX 234 almost bypassing the entire signal. The DBX manual says that "Input impedance is >25k ohm"... so I said let's put an active buffer stage between preamp and DBX. I borrowed a buffer from a friend and everything changed for the better. Now it sounds really good.

There is any simpler way to increase the input impedance "passively". What would you suggest?

Hello!

After a first happy ecl82 spud-amp SE build, well first of all I learned a lot, but now I'd like to take that information and make a similar but better built amp, maybe a bit more powerful too.

The problem is I just can't find any schematics for an EL34 Mono SE (I'm okay with the deviation of the spud filosophy and use another tube, like ecc86/88 it seems is what most people use).

Anyone have one they can recommend?

Cheers and thank you all!

A typical box speaker midbass driver employs a series inductor & maybe a shunt resistor (for baffle step compensation) & a Zobel network (to control impedance), that together provide low pass filtering. The impedance of the inductor is high for transients, so you can't take advantage of an amplifier's low output impedance, is correctly terminating the driver back EMF during transients a consideration during network design? Obviously, a poor termination (stored energy) will show up in a waterfall chart.

Edit:
I don't want to build this amp, I did a long time ago. I just found it in my pc and was curious about if people built it or ideas on it.

Hi, I found this in my pc as I was cleaning a bit.
I remember I built it a long time ago.
At first glance I tought the intput is a diamond buffer, but it's just a push-pull differential pair ? T7 / T8 VAS .
T5 / T6 being current sources for the input pairs ?. I don't get what the 5v6 zeners do tho.
( I usually used Constant current sources with two transistors like this:

D3/D4/D5/D6 limit the output current?.
How did they get away with only 3x820nF C3/C4/C5 ( 2.4uF ) and non polar in the feedback , I usually see polarised in the range of 100-200uF there.
I know it's an old design, from Elektor as I recall. using the nostalgic 2n3055's .

- Bruno.

Hi,

I have a new instance of MoOde Player. I'd like to add some new radio stations. I know there' a GUI page but I can't find it. Can anyone please help me to find it?

Just wondering, does anybody know if diyhifisupply out of Hong Kong (I think) has changed hands? Their website has changed as well as some of their stock. Just curious, as it seemed like the previous owner was a reasonable guy and I had good experiences with them in the past.

I have a pair of highly regarded Sansui (Hashimoto) 1000A output transformers that I removed from a working amp project.

These have a nominal 6K primary and 8 & 16 ohm outputs.

The bells have been repainted, and longer leads were spliced onto the originals inside of the bells. They look very nice and performed flawlessly.

$ 249 for the pair (plus freight)

I've built so many power amps that I don't have room for or energy to construct a new one with these fine transformers.

I have bought a little micro class D amp for my car 4 x 65 w rms ( vibe powerbox 65.4 )
the amp connects to the speaker outputs on the head unit then boosts the output to the speakers the amp is 4 ohms stable
But the problem is my car front factory fit speakers each side piggy backs of a sub under the seat see hand drawn pic
so the amp sees 2 ohms and at high level starts to distort the door speakers
seeing the door speakers have a bult in crossover the 4.7uf caps i only need a 2 way 4 ohms crossover which i can connect near the subs which is what the head unit feeds first
would the last pic be any good ?
20240110_165346 by glenn jarrett, on Flickr
20240111_120059 by glenn jarrett, on Flickr
20240111_122530 by glenn jarrett, on Flickr

Hi everyone
Greetings and best wishes for 2024

I had the opportunity to buy a slightly used 405-1 last week.
When tested it was found ok but of course I am planning for a recap / restoration.
So I opened it today for a preliminary inspection and to my dismay , the transformer grey silicon compound was molten and had leaked on one board (pcb) covering most components.

See attached photos. In the previous quads I worked on I did notice some semi-molten transformer compound but not like this !!

I would be most grateful if anyone could advise me how to remove this grey molten silicon compound from the board and also any method for curing/solidify the remaining compound inside the transformer

Thanks a lot

Regards

I am in search of this amp s schematic, but i had no luck. I ve found the 5350 mk2 se schematic but not the 5350 se.
I think x-pro, member here and a well gifted professional engineer designed it.

SOLD

The switch is an Elma four-wafer. Resistors are Susumu thin film 0805 SMD 0.5% 25PPM. The switch wafers are made for through-hole resistors, but SMD resistors have been soldered across the circular pads. Solder is Cardas quad eutectic. The audio taper is taken from a resistor list to be found on the Goldpoint website. Included is a spare resistor of each value.


Please note that the switch bushing is of the new kind. It has two flats and is intended to be inserted into an appropriate panel opening to prevent the device from rotating. There isn’t the familiar tag that slots into a hole in the panel as in older types. But it is easily clamped using toothed washers. Coupling included. Eyelets are unsoldered.


€80 incl. postage to UK and EU only.


PayPal preferred.

SOLD

Hi all,

I have a Goodmans One Ten Receiver.

It crackles when the volume is rotated in several places.

New pot hooked up still does it.

cleaned pot no fix

Seems there is DC offset of 250mv on the input of the fist stage IC amplifier.

Disconnected the coupling cap and the output ressitor so chip isolated, still dc offset present?

Replaced the IC with same part, still DC offset is there on input????

The mains filter caps have been replaced as have all the electrolytics couplers.

The resistors around the chip were all out of spec so replaced, the ceramic capacitors removed and all are tested as OK.

At a loss now, nothing odd on the scope regarding noise and the DC voltages are all correct.

suggestions please.

thanks, and Happy New Year to all.

I all , this is what my spdif signal looks like at the differential receiver ( FIN1002) output , just before entering the DIR9001 , what could be the reason for such ringging ?

I forgot to mention that the signal is clean at the input , and the length of the trace between the two chip is 13 mm , 0.3 mm wide , I thought the trace could do that ?






.

Hi Guys,

Sorry yet another CD104 question.....

I aquired one a few months back. Did deverything to it, replaced all capacitors and the grouding issue (griplets) resoldered the servo board. It works fine eye pattern is good and my test CD is fine. I have one particular CD that has a skip to it. It plays fine on my other player that CDM 1 MK2 but on the CD104 (CDM1 I think) it jumps like crazy. Its also slow to read the TOC. I've seen videos of the CD104 it loads in 2 seconds mine is double that. But it plays just fine.

Laser is adjusted to 500MV. Its all greased, height adjusted and I even played with the 2 screws that hold the laser. I even fiddled with all the other pots on the servoe board. It still skips the scratched track!

Any advice appreciated.

Hello All,

I'm embarking on my first speaker build and am trying to measure T/S parameters with Room EQ Wizard. There have been a couple discussions on this forum regarding this process but I have not seen this problem discussed yet and I believe it's specific to the UCA222. I'm following the guide here for reference since I haven't found a better explanation: Login to view embedded media
This is the error I'm getting during my short circuit cal sweep:


Here is how I have my setup wired currently:

I'm using the headphone output after someone on here pointed out that the line out does not have the capability to drive the load (https://www.diyaudio.com/community/threads/problems-with-impedance-measurement.319740/#post-5365046)

Here are my settings in the preference menu:


Here are my sweep settings:


Does anything jump out to anyone?

Here's some main questions I have for this setup:
1. Should the monitor button be on or off? The manual for the UCA222 states " With the monitor switch OFF. the headphone output recieves the signal from the computer over the USB port (same as the RCA jacks). With the monitor switch ON, the headphones recieve the signal connected to the RCA INPUT jacks"
2. Should the volume knob on the UCA 222 be at 100%, 0%, or somewhere in the middle?
3. Is my problem that the resistor has too small of a power rating?
4. Are alll of my settings correct?
5. Is my wiring correct?

Any help on this would be appreciated, I feel like I'm going crazy with this and am hoping I didn't just blow $15 on a interface I can't use for this project.

Thanks!

Hi to everyone,

I'm trying to repair my Smartpower Plus Cyrus.

The standby led is flashing red, even when a PSX-R is connected.

I did not detect any visible damage inside, all voltages are there and clean, power transistors and drivers are OK.

I'm looking for the service manual or at least the schematics. In case, I know that Cyrus X-Power amp has 99% the same circuit.

Any availability about?

Many thanks in advance to anyone!

I have a pair of Aiwa bookshelf speaker when I messure one bookshelf speakers it shows 6 which is rated ohms but other shows 30ohms why? It's a 3 way bookshelf speaker both used to measure 6ohms previously

Looking for the stryrol capacitor replacement in rotel marked on pcb C616 . All comments are appreciated.

Dear all,
I came across this diyaudioperks video
Login to view embedded media I want to build such a passive crossover but not sure if the final output will be in correct phase.
Can analog signal experts please verify this circuit
Thanks in advance

Hi It's me again. Sorry for bothering you on this cold tuesday morning, i have a problem. I read a post about someone who purchased a china amp that kept breaking down. After some troubleshooting he figured this was because the secondary voltage was too high.

In china the ac mains voltage is 220v, and here in Britain it is 240v. He claims to have lowered the mains voltage the transformer sees to 220v by hooking up a 20v transformer with the stock amp transformer.

But I can’t shed any light of how exactly this was done. Do you have any idea, any suggestions

Bonjour Bonne année 2024 à tous

je souhaite réaliser un amplificateur de casque à tube, quel est le meilleur :

Tube en entrée 6n1p ou 6n3p et en sortie 6n6p

ou un kit style Aïkido tout en un

Merci pour vos réponses

Would you use this type of inductor in a tweeter crossover:


I usually use air coils or ferrite coils, but am stuck as the suppliers around here are asking for $40 minimum orders so am forced to turn to ebay for small orders
Are there any pros and cons you can think of, are these okay or a poor choice for a tweeter crossover

Hi Guys, EE student and forum newbie here. Looking for some guidance on industry standards/what to aim for when building amplifiers.

In a past life I was a studio engineer so most of the kinds of projects I'm hoping to build would be in the vein of Mic/Line Preamps, EQ's, Compressors. Mostly analogue for now.

Does anyone know of good reading materials for someone studying EE but interested in Audio Electronic design specifically? My course is great, but far too general so far and non of my tutors really have any interest in audio. I have Small Signal Audio Design by Douglas Self which has proven useful. I was also looking at the AES Journal subscription, does anyone have any experience in this? Is this useful for a learner?

Apologies if this is a subject covered before. I tried combing through the forum but couldn't find anything along these lines.

This is a pair of the Hugh Dean designed and XRKaudio,Alpha Nirvana 39 watts Class A boards,
They are tested and sound fantastic just add your favorite dual supply of between 26v to 28v
Only the boards are for sale not the 5U Heatsinks.
$275. Shipped USA only.

Scott

SCA v1.2

Single ended Current Feedback Amplifier.
It could be done with various power supply voltages and bias cureents, this is just an example I`m testing and listening for months now..
No thump at start up (if all caps are disscharged). No noise or hum of any kind with sensitive speakers 97dB.
Some measurements in a few days.

Need some help building a buck converter with TL494 + BJT , Mosfet's .
Goal is variable buck converter , 0 ( or close as it can get ) to 35V at 2-3Amps.
I used lm2596 and I wasn;t happy with it. I want to build a " discrete" buck converter.
- I'm not sure how to use the two comparators for voltage adjustment ( done right ) so it changes duty cycle to maintain output voltage, let's say 5v and when I connect a 2amp load it will stay at 5v ( 4.9v at least ) not a few volts drop like I had with LM317 with output transistors for current boost.
I'm a noob when it comes to power supplies.
Here are a few example schematics I found.

https://www.diyaudio.com/community/threads/tl494-help.407455/

- Bruno.

Anyone have an HH Scott 340B they want to part with?

Hello everyone,

I am considering building an ANK 300B SET amplifier, but I am debated if I should use the ANK quad c-core OPTs or if I should look for something better, without breaking the bank (The Monolith S9, for instance, on the paper look great).

Has anyone experience comparing the ANK OPTs with other OPTs?

I have some Celestion 15ftr3070c woofers, 510 clone horns, and EV DH1A compression drivers. I have used the woofers and CD in a k402MEH and they worked great, crossed them over at 500hz. This project will be for surrounds and maybe for a center channel (with the MEHs for the front channels). I still have a 2nd pair of MEHs that I could use, but I am trying to keep the size down. I have a Xilica xp4080p crossover and some Icepower 125asx2btl amps to power each driver.

Hello,

I am building the Philharmonic BMR speakers and thought id start a post about my progress. Before purchasing the kit i tried to find a build guide/progress report on the speakers but didn't find anything. Maybe someone will find it useful down the line.

Materials:

Speaker Kit - Meniscus
Birch Plywood
Cardas binding post / Blackhole Damping / Soundcoat damping - Sonic Craft

Tool Purchase:

Jasper Hole jig - Amazon
(so i bought this knowing it did not fit my router with plans to purchase a compatible one, well come to find out its compatibility list is less than accurate, be aware)


So far i have cut all the wood pieces, the next step will be to cut out all the speaker holes, brace hole and the recess for the binding post plate.
I have the crossovers mounted and twisted on the mdf boards included in the kit, after reading through some posts here ive decided i need to find a better way to fasten the components to the mdf. A user recommended E3000, I'm going to give this a try. Soldering coming soon

I will update some more pictures of the cabinet cuts ive made so far next day im in the shop.

SLD 10 vs SD'4 10... Which will (probably) be louder in a sealed enclosure?

I'm putting in 2 10s, with 0.8 ft³ of airspace for each

SLD has higher sensitivity and BL but 2.5mm less excursion, with a qts below 0.4 and Vas of 0.51 ft³, ive been told with sub 0.4 qts that box should be below Vas, so my box might be too big? and the cone is deeper I don't know if that contributes to sound

SD4 has lower sensitivity and BL but more excursion, with a qts of 0.51 so from what I've heard the box should be above VAS, but VAS is 1.275 ft³. the sd4 has more excursion, and much lower Fs HZ, which I like the low bass.

So I'm not sure if either of these subs would be good for my setup, which should I go with?

I recently purchased a DENON DP-30L at a hamfest for $20, and it actually plays. It seems like quite a nice turntable. The main problem with it is that when the tonearm is done playing the record and is at the center, the tonearm does not pick up automatically like it should and the turntable does not stop.

So my understanding is that there is an optical sensor, a cadmium sulfide photocell, which is illuminated by a red LED when the record is finished. The photocell is covered by a shutter that is rotated by the tonearm, so that when the tonearm reaches the center of the record, the photocell should be uncovered by the shutter and the resistance of the photocell reduced by the LED illumination. I can measure the voltage at the testpoints 15/16 and indeed the voltage rises from only about 0.4 V when the photocell is blocked to about 3.2 V when the photocell is unblocked. I haven't tried to fine adjust the position of the shutter yet.

There's a comparator #4 of IC5 which is part number HA17901P, but as far as I can tell it is basically the same as the LM339 quad comparator. When the motor is started, the output of the comparator (pin 2) is pulled high by a 560 ohm resistor (R26). When the stop button is pressed, this grounds pin 2 which is used to create a pulse on comparator #3 which lifts the arm. This works, as when I play a record, and press the stop button, the arm lifts and the record stops as it should. However, when I start the turntable motor, and hold the motor stopped (like it says in the service manual), and then observe pin 5 of comparator #4 IC5 which is the reference voltage, and pin 4 which is the voltage from the photocell, pin 2 is pulled high by R26, but is never pulled low by the open-collector output of comparator #2. The voltage on pin 4 is higher than pin 5 when the tonearm is at the center of the record, and so the output should be grounded. So while the voltage at pin 4 - is higher than pin 5 +, the output of the comparator does not get pulled low, and so the end of the record is never registered and the stylus continues to turn in the end groove. So it seems like the comparator is broken, or is at least unable to overcome the pullup of some other part of the circuit.

How likely is it for a comparator chip to fail like this? It seems to me that I'm more likely missing something, and I'd rather not desolder a chip on an old PCB without having a good reason, because I might damage it. It is 42 years old, but nevertheless I don't really expect such simple ICs such as comparators to fail. Perhaps someone has a similar Denon turntable with the optical end sensor and can advise. Thank you!

I am designing a transistor, low cost, high performance I/V converter for NOS DACs.
The DAC in question is the 16bit AD1856 R2R Iout, +/-1ma impedance, 1.7k
I started by the simple circuit from Linear Audio,
https://www.linearaudio.net/simple-high-quality-iv-converter
The distortion is too high and perfect hfe matched transistors not necessary.
I am at this stage with input impedance of 50ohm, full scale THD 0.0005%.

I am wondering how the 50ohm impedance will effect the distortion of the R2R?
If I decrease, the distortion increases, so, there is a minimum.
Andrea Ciuffoli has tested with 200ohm resistor.
https://www.audiodesignguide.com/DacNoOverSampling/
The THD is 0.01% for 116mv rms instead of 140mv full scale that this DAC can go down to 0.002% THD+N.

Hi, I just got two LM3886 from a PA speaker. Do they look genuine to you?.
Maybe I'll do something with them if they are worth it.
Thanks.
- Bruno.

Hi,

title says it all. He was last here on 03-09-2023 14:35, and I always appreciatred his knowledge in tubes. Does anyone know anything about him?

Best regards!

https://www.ti.com/lit/an/slaa788a/...=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3245

This document describes how to create a negative feedback loop for the TPA3255. Makes sense for the most part, but I think I'm a little lost on some of the finer points.
1) There's a table that prescribes a list of components in order to make the loop. It does not however give too much on why specifically those components and values are chosen. It says "for stability", but why in those amounts?
2) The design, like the reference, calls for an initial filter of about 50khz. In the spec sheet, it says the chip is capable of 100khz bandwidth. Is there as specific reason, or is that just the number they chose?
3) At the output, it has a zobel which is, again, said to be there for stability's sake. The thing that confuses me is the zobel isn't used in any amounts that correlate with a load. I thought you needed a speaker in order to complete the function?

You have not lived unless you have tried to find ASSORTED grommets for 1/8" thick plate,
Does anyone know a good source ?

I own a Hot Rod Deluxe 1VTm Fender. Recently it started emitting static noise when guitar is plugged in. Noise would increase with volume. I would appreciate any help on the problem and how to fix it.

just saw this
if anyone need some of those
https://www.facebook.com/marketplace/item/2142894536058854/?mibextid=79PoIi

Elekit TU-8500 Preamp

Price Down: $350

https://wallofsound.ca/audioreviews/review-elekit-tu-8500-tube-preamplifier-kit/

UPGRADED:
1. Mundorf Capacitors: Mcap Suprem * 4
2. Muses 01 OPAMP * 2

Sound is awesome and plentiful.

"Pleas, read"

1. Line 3 is not working properly.
(left channel is not heard, right channel is too low sounding)
But Line 1, 2 & Phono are working good.

2. right top corder has little scratches.


Except above things, everything is working good.
And good preamp.

No returning, Serious buying please.
Thanks.

Dear members,
i am looking for a few pieces of the long obsolete 3N124, 3N125 or 3N126 will do as well.
Please contact me if you want to sell some.
Kind regards

Dear members,

i am looking for a few pieces of the long obsolete 3N124, 3N125 or 3N126 will do as well.

Please contact me if you want to sell some.

Kind regards

I know some inmates has run their stacked ESL 57 with big triode (211, 845 or others) SE amplifier. Do their stacked Quad ESL 57 wired in series or parallel??

Thanks!

This is a great analog multimeter, with active FET Hi impedance input (10Mohms), and very rare uA current scale.
Meter in perfect condition, slight scratches on the plastic window. Great analog dial meter for audio work.

Used item, but tested working fine. Was used in my lab until recently.

item include: Weston 666, test leads, original leather case. No battery included (need 4 AA + 1D)

COSMETIC CONDITION: some scuffs/scratches

Asking 25U$ + shipping + Paypal 3%
Thanks for looking
SB

Hi

Are there some alternatives for the opa1642 that has pins for soldering into holes? The reason being that I plan to do some DIYing and would like the test different settings on a breaboard.

Thanks!

Up for sale is a pair of Andrea Mori's ultra-low phase noise TWTMC-DRIXO oscillators (45.1584 and 49.152 MHz).
Bought completed directly from Andrea, tested but never used.
Asking 300€ including shipping within EU.

I have been googling but not really found what I'm looking for.
We see many curves on here. Many are audible responses that have been measured with a microphone. I can do this and understand the process.
However I dont know how I would measure the response of say a crossover, active or passive, or an input signal trafo. For instance I am building a NP 6-24 Active crossover and maybe I'd like to 'see' the response before hooking it up.
I have REW, laptop, DATS, scope.
I need to feed a signal sweep into the DUT, understood. But my what means do I 'record' what comes out the other end.
And is using REW, and considering a passive XO over an Active, one being line level one being speaker level, do the signal amplitudes matter.?
Thanks in advance

Hi, I am looking for a schematic for a 300B single ended power amp circuit with about 2V sensitivity. All circuits I found so far either too sensitive (like 0.5V) or too insensitive (4-5V).

Thanks for any recommendation,
Mo

So im trying to repair a gas competition 7000.1d.
so the power supply mosfets and output mosfets where blown, aswell as all gate resistor on power supply fets.
ive replaced all gate resistors and removed the rectifiers.
when testing with fets it just shorts the waveform on the gate and maxes the current limiter i have of 5 amps to the amp.
waveform on ps gate exist without fets but are not the same amplitude, what could be the cause? ive tried to replace the tl494 but no luck. vcc is at 12v. ive checked all 4 step up npn transistor and checks out fine with multimeter.
no green light nor protect diode lights up.

Time to fire up the Table Saw.

Building a Altec 618B cabinet.
Far as I can tell the B suffix was for the 12" speaker cutout.
618 Utility Cabinets being available for 8" and 12" drivers



Here is a photo for reference of Original 618 Altec Utility Cabinets
Showing both cutouts available.



Original Cab believe was 1/2 inch or 13mm plywood baffle
5/8 inch plywood sides.



This project, not using such thin wood at all ... nope
All construction is with Oak 3/4 inch or 19mm Ply
then few extra braces added to baffle.

Well it is very much at the start.
Just got most the panels cuts done today



Then just started the glue up and clamping



Lots of final finish and prep to go.
Cabinets will be painted like original
with Silver Hammer Tone paint.

As mentioned much thicker wood and
extra braces on the way.
Its a 1940's retro upgrade project.

Has anyone put Audio magazine on CD and made it available? I'd buy all of them from 1947 till it's 2000 demise if I could get it.

Hi,
Have Cyrus Two with PSX, working excellent since 1992 until I managed to shortcut one of the loudspeaker cables (don't ask me how...).
Now it is dead, well both the Cyrus Two and the PSX light up when you turn them on, but no sound at all. I suppose that means the fuses are OK?

There was a light smell so probably some components got damaged. When this occured I haven't started to play so there was no output to the speakers, it occured as soon as I switched power on.

So is just teh amplifier damaged, or also the PSX?
Grateful for all advices.

Regards Robert

Anybody point me in the direction of a SS guitar amp kit? Preferably with step by step guide.
Thanks in advance 🙂👍

For sale is a SB26ADC dome tweeter with an 8” Somasonus Wavguide printed in MJF to a very high quality. Price is £100 including UK shipping. Pics for reference of the WG only.

Hi one channel is having only top half of sine wave and lower part missing. If I increase gain beyond clipping then the wave form is as shown in the picture. Good sine wave is reaching the output section. Lifted R308 and it had good sine wave. All the transistors are looking good.

Hi,

I have an odd problem with the arm lifter.. I think....

The headshell drops to quickly now when being lowered by the lifter. It used to float down gently.

Does this mean the lifter needs repair or is this an issue with vertical damping?

Should I even be worried about it?

Any help would be very appreciated!

Thank you all on this wonderful site in advance !

Hi. In your opinion what can play better / louder between 2 Tham 15 or 2 DUAL 15 reflex loaded (200 liter net tuned at 37 each) with the port in the middle? We are talking about 2 vs 4 sub, but some people told me that in a horn loaded configuration it will play louder. Cone will be Rcf LF15X401. Thank you

I have a pair of AMT tweeters and a pair of Dayton Esoteric ES25Nd ring radiators for sale. The Daytons are new unused and the AMT's are from a previous project.
I would up with Bleismas and am cleaning house. The Dayon info is here: https://www.audiophonics.fr/en/twee...e-neodymium-tweeter-4-ohm-o1-9cm-p-10021.html
The AMT's are a little bigger than the Dayton AMT2-4 that are popular with more power handling but a little lower sensitivity @ 90db/w
$80pr for the ES25Nd and $50pr for the AMT's

The Audio Amateur Home

Wish I subscribed back then - a lot of interesting stuff going on, still relevant 50 years later.

Inspired by the short thread on Vendor's Bazaar:

https://www.diyaudio.com/community/threads/nad-3020-clone-pcb-kit.388467/#post-7080981

I started thinking about making a tribute amp based on the essence of the famous NAD 3020.

The NAD 3020 was my first amp and I loved it. It sounded good, also playing loud on my Cerwin Vegas and later on my DIY 3 way based on Peerless, ScanSpeak and Dynaudio.

Looking at the original schematics, there are things I would like to simplify quite a bit.
1. The power supply needed is complex, with +-28V, 29,9V and -25,6V ....... would be much easier with just a single +- PSU
2. The power supply for the input stage is regulated, and in the later model 3020i this is also true for the main output PSU. Is this really necessary?? I would guess that the input stage has less PSRR then would be the case for a differential pair.
3. Changing the transistors and components to SMD as much as possible / feasible, and also changing to types readily available in 2022

But what is the essential in this legendary amp?
And would it at all make sense in todays drift towards Class D?
Is the good sound just a good old memory 😉 ?

I would think the essence is the input and VAS configuration, and this is what I would keep. It is not symmetrical, with no diff input and no current mirrors. This would imply higher even distortion, as these steps would reduce exactly even order.

I would go for relatively low power with say +-35V. This could easily be provided by a cheap regulated SMPS, and would be a big improvement over the original PSU of a stock 3023

I have been doing some LTSpice sims, of both the original and a modified version .... stay tuned

as above. I am thinking amps but could voltage rating x amps? Thanks again

Hiya,

I've had my turntable in storage for about 6 months, and begun using it again recently. The issue is that over the last week the speed hasn't been correct, and has now almost stopped spinning.

I've tried finding a service manual so i can have a go at fixing it, the one link i found was to an audio website where you had to register, and they were no longer taking registrations.

Can anyone help? The only L85 manual I've fond only has setup details, not troubleshooting or maintenance tips

I've never tried doing this before, but would like to as it's cheap and isn't worth paying to have fixed

many thanks in advance for any help
David

Hi,
after a rewarding build of the Woden Baby Labs for the CHN-50, especially for the price, I am evaluating my options for a box with more bottom output. I am not leaning against Frugal Horn Lite because of the footprint and more difficult room integration.
So my options are Woden Giraffe and and a mass loaded quarter wave design from the MA website. Both designs are quite similar and the Giraffe is targeted for Alpair5.2. Which box gives more bottom end? Are there other differences I can expect in for example max spl or bass authority?
My biggest full range at the moment is a wide CGR Planet 10 design for CHP-70. In comparison, how would a CHN-50 in Giraffe perform against this? I guess max spl is lower, but what about low end?
Maybe I have overseen options.
Greets

https://www.kjfaudio.com/wp-content/uploads/2020/09/CHN50-Compact-Mass-Loaded-Quarter-Wave.png
http://wodendesign.com/downloads/Giraffe-A52-MLTL-0v99-081015.pdf