Hi friends!.
Looking opinions for my next build. It will be a slim 2.5 way floorstander.
The tweeter will be the satori ring radiator and I want to debate on the Satori mw16p vs Vifa NE180W drivers.
I know that satori is easier to work with and has better distortion profiles, but I've read many people saying that vifa ne180w actually sounds better.
Also the vifa ne180w is about 20 dollars cheaper per unit.

I'm confused about the proper filament supply design for the 4P1L, or any DH tube, I suppose.

I've seen PSE schematics that show each channel (2 tubes) being heated by the same filament supply.

Yet, I've read posts elsewhere that claim that DH tubes always need to be heated using a separate filament supply for each individual tube, regardless of whether the topology is SE, PSE, PP or PPP.

Which is correct and does it apply under all circumstances? In other words:

Do different topologies (SE, PSE, PP, PPP) affect what is allowable?

Do different bias schemes (cathode, fixed, filament) affect what is allowable?

Good day peeps

I have a Pass Aleph 5c kit amplifier on the bench of a friend.

It has an unacceptable high hum on the speaker outputs.

There is virtually zero DC offset. Grounding was done according to all the tried and tested theories (including referencing to Douglas Selfs writings).

The hum is present when the inputs are shorted and also when the ground is lifted.

Any pointers...?

About ripple rejection what BJT parameters are important.
In a topology, i am working on, Early voltage makes a lot of différence.
I understand there à feed through effect coming from the collector dynamic resistance related to Early voltage.
I think a good pass BJT should have hight VAF.
Low collector capacitance matters too.
What do you think.

Hi, for some time I was playing with the idea of building a portable speaker with tubes. I normally build guitar amplifier, but this time I gave this a shot.




I posted the whole design and build process over instructables How to Build a Portable Bluetooth Tube Amplifier : 14 Steps (with Pictures) - Instructables, maybe you find it interesting.

And a picture from the interior:


For a low cost tube amplifier build it turned out pretty nice.
Cheers.

Hi,


I have a problem with my Schneider TA 4000, sound still coming out of the right channel when volume is at zero. The issue is not in the balance or volmue potentiometers and I have not been able to track down the service manual. Any ideas on what is happening, is there a simple pot to tweek, thanks?


PS How do folks get the boards so clean, is there a special super small cotton bud that does fall apart?

AnTek As-4T360 power transformer for sale 100% works.
360V 0.5A
360V 0.5A
6.3V 4A
6.3V 4A
$60 include Priority flat rate medium box shipping.

Hi
Would like to sell scan speak 21W8555-01
I have 4 of them

Thay have not been used for a while, have been laying in the closet with no use so I would like to sell them.

Two of those I have buy new and two used.

On the picture are those that I have buy new.
The other two I can post pictures in a couple days.

Thay are all working great.

I would like to get 150euro for those on picture ( 2 x 21W8555-01 ).
Or 200euro for all 4 x 21W8555-01
+ shipping costs and pay pall fee if applied...

I think that shipping inside EU is only reasonable.


Thanks

Thought I'd share something I completed a little while ago. This one was whipped up over a few weekend and then a few more weekends since spring, but the effort has been worth it!

The Northern Pikes were a band from my home town, they were a big deal when I was growing up. Highly recommend giving a listen if you're into 90's rock.

It's an AMT3-4 on top, a Wavecor WF120BD03 in the middle, and a Vifa M26WR09-08 on the bottom. Around back is a CSS APR-12. The result is a fantastic combination with exceptional clarity.

The baffle is African Mahogany with Maple accent, and maple veneer on the sides. It was my first time veneering, and learned some valuable lessons. There is some cracking in the veneer unfortunately, as I learned that wood glue iron on mothod is best used on paper backed only, so next time I am using contact cement instead.

The phone photo unfortunately shows a lot more red than there is in reality, the second up-close photo is more proper colour.

Hi.

I´m building a small PA-ish speaker with 2x6" and driver+horn.
(Posting here and not in PA, as I hope for relevant input here)

Crossover is 1.6Khz, 4th order, fully active. 120Vpp amp for mid-basses.

Sound is OK, at moderate levels, but at high levels it becomes "unpleasant".
Amp is not clipping as far as I can see.

The drivers are high-power units with 2"voicecoil and rating of 200/400W pr unit. 91dB/W.

I'm trying to measure distortion with my (cheap) measuring mic and and STEPS/ARTA.

What level of distortion shall I expect? at moderate levels I get around 0.5% and at high levels I get 2-5%. At very high levels I get peaks of 20% distortion at some frequencies.

I will try to capture some waveform and post here.

All inputs are welcome 🙂

Kind regards TroelsM

I have taken the 1980's Maplin 225WRMS disco amplifier and brought it up to date with modern transistors and a better circuit.
Constant current source on front end. Better front end decoupling.
Decreased power output to 100 watts RMS.
Output transistors are MJ15003/4.

Hey guys hows it goin? So I Purchased the Zoudio 4 channel Amp with DSP. Has eq and crossovers built in. But I am having a hell of a time getting my speakers to sound good.

Is there a super simple way to measure the output of my speakers so I can adjust levels and crossover points? then maybe start playing with EQ a little bit 🙂

I built some 2 way bookshelves. tweeters are Beston ribbon tweets. Beston RT003C Round Ribbon Tweeter

And I'm running some CDT ES-400 mids. https://www.cdtaudio.com/pdf/ES-4_07.pdf

I'm intrigued by Michael's latest design. My first thought when I saw the schematic was if it would be as easy to make it a balanced input as it was with the IronAmp.



Regards,
Dan 🙂

Hello,

I have some issues with my lovely Yamaha HS80M Speaker. When I power it on, there is no sound. The heat exchanger gets hot within minutes. When I power it off, the big woofer pops a lot. (The issue seems to be nearly identical to https://www.diyaudio.com/forums/multi-way/341630-fix-yamaha-hs80m.html)


I disassembled the speaker. I did not find any issues, besides the amplifier board. Here is an image of the amplifier board:

WeTransfer


I asked Yamaha for support, but they replied, there would be no option to buy the components, but the whole board for nearly 200$, which I find pretty annoying.

Please let me know, wheter I can repair the board and what I need to do for repair:

Which tools do I need?
Which components do I need to buy?
Where to buy them?

What do I have to do for repair?


I have very, very basic electrical and no soldering skills, but I am willing to learn.



Thank you for your time.

I got suckered into hauling home a neglected 1963 Wurlitzer 4100bw organ for my budding jazz pianist son. 7868 Power tubes were shot, but all the others (5BC3, 9x12AX7, 29x12FQ8, 4x6EU7) test good.

This particular organ uses tube oscillators and dividers, rather than reeds or tonewheels - thus the pile of 12FQ8s. From what I've seen, it's got a great mellow tone when it's in good shape.

To get started, I swapped in some marginal 7868s and replaced the shot 40uF reservoir cap, and I was able to get some very quiet sounds, which tells me the oscillators are all working (whew!) Scope shows the signal hitting the power tube grids is tiny, so next I'm going to work backward through the preamp to determine where the signal is getting lost. I'll replace the rest of the electrolytics along the way.

The motor for the Spectratone (a Leslie-esque spinning speaker) runs continuously, by design; I'm going to add a switch for that, because it adds a lot of noise that's not always necessary. It needs a new belt too, but that's neither here nor there.

Voltages are hot, as I would expect from something designed for 110V running on my 124-125V wall voltage. It's not egregious, though. Plate voltage is 410V vs. 395V on the schematic. Screens are 380V vs. 365V. Preamp supplies are 325V vs. 310V and 295V vs. 270V. Bias is running the other way, though, at -15V when it should be -17V. I'll probably put in an adjustment pot for that.

Not sure whether I want to replace the 7868s with 7591 and new sockets, or 6P41S and a lowered screen supply.

Has anybody else ever worked on these? Any advice? Known trouble spots?

I have decided that I have already wasted enough time in my life troubleshooting poor barrel connector connectivity that wasn't obvious at first blush. So what do people use for cheap, 2 conductor, low voltage, low current (<2A), non shorting, reliable, chassis mount connections?

Hi,

I have an Arcam black box with the TDA1541A chip. After doing a lot of reading I managed to removed the filter chip and works even better. Then a lot more reading and discovered a lot of people connecting a I2s board to the TDA. I purchased one and struggling to get it to work.

There is a post about removing the muting transistor to enable this which I did but no sound is coming out!

I connected WSBD - LRCK, CLBD to BCLK and DABD to DATA. Connected a 5v power source also to the board but nothing after feeding it with a 16 bit 44.1 signal.

Any help greatly appreciated!

can full differential output be connected to pseudo differential input?
would I just connect the two grounds of the full differential to the single ground of the pseudo differential and be good?

Hi there,

Thought I'd stop in, say hello and share that I look forward to learning more about my new hobby.

J. Peterman

Hi Folks;
I have been using an android TV streaming box, that no longer functions for online video streaming but does play 4k 30 fps video 'fairly' well. This box was around the $100 CDN price range.
Could anyone suggest a reasonable economical (box) that could play 4k 60 fps video files possibly via USB from an external hard drive?

Hello

I am trying to wire 5 (8 ohm) full range speakers as a mini array. I would like to keep the impedance to 8 ohms total for the speaker cluster.

How would I wire this? I have seen examples for even speaker numbers, but the odd number is throwing me. Is this doable?

Thanks for any assistance.

Craig

Hello, I was thinking if it was possible to replace an OP TL072 with an Opa627 that would have to be modified in this AMP




Sorry for the question but I don't have much knowledge and sorry for my English 🙂

need a 10x10 crossing switch, with 100Hz to 6KHz BP and low RF suceptibility

Between integrate circuits and discrete transistors, wich design would you choose ?

My negative voltage supply board came with this connector and cable. What is the name/type of this connector?

I need to order an extra connector with cable.

Regards, Gerrit

I'd like to use some solid core silver wire for the signal path of a simple tube pre-amp. In the past, I've used 18g, 20g and 22g for different portions of the wiring. Is there any reason to not just wire the whole thing up with 20g? Does reducing the wire diameter to 22g (or thinner) for the lowest signal portions make any sense? TIA
Dave

These damn tags refuse to solder. I've tried wire wool, filing a small layer off ..turning the solder iron up.

What gives? Took me ages to specify them from the millions available and now they are useless to me....annoying!

Hi all,

I have been agonising over building an offline regulated linear PS for a preamp. AC Mains are nothing to mess with, right? So I have become obsessed with questions such as whether to use a PTC or regular fuses or both? Where to place XY Caps? What about NTC to manage inrush? Then there are transients to worry about - TVS or MOV? Not to mention a switch, snubber and on and on.

I decided eventually & sensibly, I think to get an AC/AC wall transformer and work from there (all this was because I need two rails +-12v and was hoping to use a CT transformer I have).

I also happened to have an old Sony STR 6046a on my bench and I was aware it used a similar +- V setup. so I lift the lid and have a look at the schematics and I see... a switch, a fuse, Xformer, diode bridge, filter cap, done. But what about that destructive inrush current (two 6800uf elna filtering caps rated at 50V)? What about transients? What about safety hardware!? I have described the input to the power board which takes +-27V, so 54V total. As I was scratching my head I decided to test the ESR on the big caps and they came back excellent. All were original components and at this stage of the circuitry, all were working to tolerance - we are talking 40 something year old parts here!

So this is a long winded way of asking -
1. is inrush current really something to worry about in lower power devices
(like a preamp or headphone amp etc)?
2. Are all the modern precautions simply a way of protecting lower quality modern parts?
3. Is it really irresponsible to DIY build something offline paying the same indifference to safety regulations and standards as the vintage power gear does? (I am aware laws, components etc were very different 40yrs ago and mean no disrespect to the vintage gear)

Thankyou all!

I'd like some up-to-date recommendations for diodes to use for rectification in tube amps. Are there better options than UF4007, if so which?

I could do with some help on voltage ratings as well. A typical PSU for my amps would have around 300v with a load of say 160mA, but maybe 425v off load. So would a 600v rating be safe? I have a few C3D02060F which are 600v Schottkys. In fact would Schottky or other specialist diodes make any audible difference?

I've always used tube rectification but I do use hybrid/Graetz bridges. I haven't optimised the diodes for a while. I'd also like to listen again to solid state rectification to see how it sounds.

Hi I need 814 (VT-154) tubes. Somebody have?
Thanks 🙂
.

If you were choosing a sub woofer, out of these 3 layouts which might you prefer and why? I realize it’s probably a bit vague, sorry, but just assume the CSAs are similar and the camber or offset chamber and actual main qw paths are similar in size with only the direction (or reflection) being different.

Hello
I need some advice on picking ICEpower amps for my build.

I am building two three-way speakers, each speaker has:

One Subwoofer with 200w rms
One Midwoofer with 100w rms
One Tweeter with 20w rms

All in 8ohm load, it has to be stereo?

What would you guys suggest as the setup, as far as i can see the smartest thing to do, when pairing it up with a miniDSP, is to have 3 amps setup.

I have 4 off Seas 6.5" 4ohm polypropylene that I fancy doing a little project with. 1 on the front, 1 on the rear and wired in phase at 8 ohm. (So far so good ?!)
They aren't the greatest at the higher frequencies so will be doing a WAW style build crossing low to a full range of some description.
Now if I sim 1 driver in a given volume box I get the roll off at a given point. If I put 2 drivers in the same volume the roll off is earlier. I am loosing LF output.
Here is my question. Assuming winisd doesn't take into account any baffle step losses ...which we know it can't....Will I regain LF extension due to the rear driver cancelling the baffle loss.? So I actually will get (in a perfect scenario) the LF extension as winisd shows me for one driver.?
Thanks

I have one of these amps driving a boss platform and i notice an early roll off from 25hz at bass.
anybody knows which ones are the input caps?
i thought if i replace them with larger roll off will go lower.

Hi all brother i want to order smd transistor mark AG & DK
But in indonesia, if order must use code conventional..
Someone can help me code conventional for this smd transistor?

Hi everyone, i have problem with driver modul hifonics brutus 2200 ic u2, u3, i want to replace this ic but i dont know ic code, help me please.

Hi.. Everyone...
I have problem with orion 2500D, while power up after relay on, shown any sound like a horn high freq at speaker .
I was replace ic's at modul driver, ic TL074, ic 14060B, and i try replace ic 305 with 74hc02 but ic very hot mybe wring code because code was erase and ic 305 back to original, but problem not solving, please help..

I have a Soundstream Angina that I recently started to repair. It needed new power supply and output MOSFETs. After replacing them the amp was able to power on. It drew about 1 amp at idle with the remote powered. I was able to get clean output from the amplifier at low volumes but since the heat sink is not attached I am not comfortable doing much more.

My questions are:

The amp turns on when I give it power on the BATT+ terminal and no remote hookup. Is this normal for these amps? I am thinking it has something to do with the "audio sensing" it is capable of doing when using high level inputs but I am using the low level RCAs so still a bit confused. It does eventually shut off after 30s-1min. I can time it exactly if that helps.

Second, the 15v +/- regulators seem to warm up pretty quickly without the heat sink. Is this normal? Or should I be looking for another fault drawing excess current on those regulators? They seem to warm up evenly but I was expecting with no audio signal they would not become hot to the touch within a minute.

Thirdly, Perry so generously shared a schematic for the Soundstream A4 series awhile ago but the Angina seems to vary a good bit beyond the power supply. Does another schematic for this amp exist?

If pictures or other/more information would be helpful just let me know and I will do my best to get what you need!

*If you are reading this before I add my tools to my signature just know I am doing it right now 🙂

Thanks!

Hi, on a Hammond power tranny with multiple input voltage options and hence multiple wires what do you do with those you do not need?

Thanks.

Hello, I'm new here. And new to circuitry. So bear with me please, I don't have really any experience with circuits other than electrical (residential/commercial) circuits.

I have a Rockford Fosgate P1000-1bd that I got cheap (too good to be true). Cosmetically good shape. I opened it up and found the output capacitor with a broken leg but everything else looked fine. The cap also had burn marks on the leg of it as if it has arc'd. So I replaced it with a Panasonic ECQ-E1106JF (below is a picture of the old one and then new one installed)

The amp powers up but does not have any sound or output when feeding it a signal from my phone through the RCA. No DC on speaker terminals.

I found that Q2000 transistor seemed to read very odd, it had - 19v, -. 741, - 7xx. I replaced it, now it's reading - 22v, - 7.01v, - 7.11v.

When I measure the rectifiers (CR1004 & CR1005) from left pin to left pin I get -83.7mV DC, center to center I get 55v DC, right to right pins I get -84.7mV DC. Seems very odd.. The rest of these transistors read accordingly to this picture attached with voltages that I found in another thread.

The 75344G fets voltages all have:
6.68-6.7v DC gate to drain
12.06v DC source to drain
5.44-5.45v DC gate to source
Not exactly sure what I'm supposed to see on these?
All the fets to left of the rectifiers (IRFP3415) read in the mV range jumping around on all their pins..

Nothing is getting hot on the board either.

My test bench consists of a computer psu that puts out 12.08v

Unfortunately I do not have an oscope..
Looking for suggestions on what to check next.

Hi



Recently purchased a 2nd hand Vitus RI-100. Upon delivery the rear panel had been bent inwards as the binding posts had come into contact with the ground/hard surface.


Managed to straighten the rear panel and the input board that also mounted on the rear panel appears fine. No signs of any other internal damage and after straightening the rear panel you would not know any damage occurred.


Upon firing the amplifier up for the first time I got a ***WARNING*** PTC PROTECTION error.


Obviously something else is wrong and my fingers are crossed this is not indicative of a major issue.


I can't find any service manual or information regarding repairs on Vitus equipment. Does anyone have an idea of what could possibly be wrong with the amplifier?

Whilst downloading Audio magazines here: AUDIO - Consumer audio and music magazine from 1947 to 2000.

i chanced opun a 1995 edition about a 100w class A amp by Norman Thagart:

part 1: https://worldradiohistory.com/Archi...tu34fta2pKBdd2ikr_ZXd6U-ka40d9A3hwSVwEco2D-wM

part2: https://worldradiohistory.com/Archi...PNVytNdEr_d0W_Mwrkn8hETqCz7PtE4E0w8eMlHNeanZE

part 3: https://worldradiohistory.com/Archi...HNacs6fkqGSS6gq0XvADNChbQRnGQZpo86U3PmWvm7DY4

the 3 art article is complete with all information needed to build this amp, so i wonder if anybody here besides the author built these monoblock amp. looking for your feedback...

Hi, I have started restoration of my Yamaha MX-50 and looking for a good quality replacement for this transistors in reasonable price. Please note there should be minimum 140 hFE (S hFE range). Prefer shipping from europe to avoid weeks of waiting for parts.

Regards, Frogeon

Why do my guitar amplifier crackling like a campfire whenever I plug ANYTHING into the input jack? Cable, adapter, wireless adapter.. anything. Silent when input jack is empty. Both channels, clean and overdrive. Sometime it's more prevalent in the clean channel, sometime more pronounced in the overdrive channel. Does it no matter what volume it is. Tried it at four different homes with a Furman power filter, still sound like a campfire. Any help would be appreciated. Thank you.

Hi All. I hope this topic fits this room. I have a custom amp based on the AC30 with 2 Celestion Alnicos. The amp has less than 10 hours use on it. It sat for a year or two without using, and I know I am supposed to use a variac to power it up, but I turned it on, loud pop, and now one of the speakers is buzzing like it's blown. When I put my hand on the cone the buzzing/grumbling stops. This amp was never cranked. Did I blow the speaker? Hold downs are all tight, and I cant see anything rattling, though I have not checked tubes yet. Thank you in advance. Also, I'm assuming that I cannot simply unhook one speaker and run it, as this will damage the transformer?
Sincerely,

toneless in Seattle

Hello all. I have been having a devil of a time trying to get this circuit to work.

The upper CCS is supposed to be a power Jfet from united SIC with fixed bias working in class A and the lower device is supposed to be a CCS load.

The idea is to have the opamp bias the bottom device so that I do not have to use a bias resistor. By avoiding a bias resistor, the voltage drop across the CCS is minimized.

The issue with the circuit is that I keep getting 12.8v at the output instead of the intended 0v. I know I am doing something wrong/stupid, but I just can't seem to figure it out.

Any thoughts are appreciated.

Hello People! I'm new to the amp diy building world and I would like to build one with your help! I went for this 300B SET amp and I have most of the components. I really learned a lot from you all from all these threads and posts but now I think I am ready to build one of my own! I have a custom power transformer that I found and it's really close to what I need, I'm missing only one 6,3V output but I bought the Hammond 266L12B for the two 300B tubes(I'll put a picture), I'm thinking of putting maybe two 230V power cables from seperate electrical outlets? But I'm sure there is a better way of doing this. I've made a wooden box and I need some help with that too, What material to use for the top and bottom plates? And I would like to have a PCB for it. I know that the point to point construction is better but I like the clean look of an amp haha. I have all the tubes, output transformers, chokes, Capacitors etc.

DIY 300B Single-Ended-Triode (SET) Hi-Fi Amplifier Project

This is the one I'm trying to make. Have a good day!

I'm mostly a car audio guy so please bear with my lack of knowledge on some of these topics. I've got a pair of 6" Silver Flute drivers mounted in my doors and decided to build some AP type enclosures for them to see how they'd work. There's not a lot of AP guidance available on the internet, other than one site that states that:

"..the woofer's Qts (total system Q) that determines the AP candidates! ANY WOOFER WITH A QTS OF .45 or LESS CAN WORK VERY WELL IN AP DESIGNS! I made that bold so it will stick with you guys. So, if you want to try your hand at this type of enclosure, seek the Qts spec of the woofer. If it is less than or = to .45, you have a winner. You will find that it is mainly the subs designed for ported enclosures"

The 6" Silver Flute has a published Qts of 0.24, and Zaph's testing showed 0.29. Based on the criteria above it seemed like a good candidate for an AP enclosure. There's not a lot of space in a car door, so the enclosure depth was limited, and it also had to be water resistant, so the port had to be shrouded and point down. The membrane is fiberglass matte, in layers, and clamped between two grilles. Here's what it looks like:



So I ran some tests using REW and my living room floor, to get a rough idea of the change in the impedance curve with varying amounts of fiberglass membrane. The tests were run in the middle of the floor with the driver in the enclosure and aimed up at the ceiling. It wasn't extremely precise, in that I was holding the test mic at approximately the same height over the driver in each test. I can see that adding more resistance to the membrane drops the low frequency impedance spike, but from what I understand that in itself isn't really critical unless using tube amps? I'm using all Class D in the car. Anyway the results of the impedance tests came out about as expected:



It's also altering the frequency response of the driver, but that's not critical in my application either, as I have a DSP and can work with just about anything. Here's the amplitude plots:



But the real questions come from the distortion runs. It seems that the AP membrane reduces the measured distortion levels by as much as 5 dB up to about 2000 Hz, then there's some real nastiness that wasn't in the open vent plot. Maybe that's from reflections inside the enclosure? But overall below 2000 Hz why would the distortion drop so much with an AP membrane in place?



So, ultimately I'm trying to figure out what I figured out, and if I should bother applying it. Thanks -

I am going to build myself a Remus preamp. Have the original magazine, Audio/Video from around 1990? Built my first version around 1992-ish?, and it did not sound very nice at all. My skills are probably better now, compared for about 30 years ago? Found a new schematic at Lencoheaven

https://www.lencoheaven.net/forum/index.php?topic=28010.0
Looking at the schematic I see that the cathode resistor on V2 are 10K, but at the original schematic from about 1990, i think it was 2,2K? I know that the tapebuffer are removed from the new schematic. But why 10k and not 2,2k?

Searched and found nothing on these interesting fellas. The diagram in the datasheet seems to indicated that the diode plates lie in between the cathode and the control grid. As such how would you handle the diodes if you are not using them. I wouldn't want them to strip off electrons nor would I necessarily want to turn it into a space charge tube (although that might be interesting) yet it is generally considered bad form to have elements floating. Can one simply ground them?

Hi wondering if you know the value of theese resistors in the amp ? I cant make out what the color bands are and the amp that im working on someone cut them off the board.

I've been simulating the signal currents that flow in the primary of the First Watt M2's input transformer. And this has led me to a discovery: I might be badly mistaken, but I think the circuit is discussed erroneously in the user manual. Here is the pencil and paper explanation.

The relevant piece of the M2 schematic is attached below as figure 1.

I think the user manual describes this, in the passage which is attached below as figure 2. Please have a look at the red underline. I think this is saying that the impedance looking into the primary of the transformer, is 6K ohms. That's what I drew on figure 1 above.

To analyze the impedance we treat C2 and C3 as short circuits, and we treat V+ and V- as AC-grounds. Then the transformer secondary is loaded by R6 and R7 in parallel, plus another big nasty mess caused by the Cgd's of the output MOSFETs, which I will assume is super high impedance and thus negligible.

What I get is displayed in figure 3 below. The Edcor transformer has a turns ratio of 5-to-1. {Math check: 600 = 15K / (5*5)}. So the impedance on the secondary, 23.5K, is reflected back to the primary, by a factor of 6 squared. Thus Zin = 23500/36 = 653 ohms.

But the manual says 6000 ohms. Where have I gone wrong?

If anyone happens to be wondering, "Does simulation agree with the pencil and paper explanation?" the answer is yes.

I have been looking at the sizes of heatsink used in domestic commercial 80-100W per channel output amplifiers to find a rule of thumb/tried and tested guide to sizing a heatsink and to consider enclosure space, venting or not and saw this Naim 250 with the covers off.
Two friends owned these amplifiers back in the late 70's and the base panel ran very hot when the volume was past 12 o'clock for a while but I never saw inside one.

The power transistors for the amplifier and regulation modules appear to have no more than a piece of U channel alloy that looks to be 4mm in thickness. The channel pieces attached to what I presume is box pan folded steel of a gauge commonly used for small enclosures.

What does anybody know about the heat dissapation in this amplifier? I googled Naim 250 overheating and there are some results but not so many as I would expect.

Hello

I have a 8" sub driver that is being repurposed from a Logitech THX system. I have a Polk 100w plate amp I will be using with it. I am setting up a 2.1 system in my office which is 12'x18'. I have some decent custom MTM mains with tang band aluminum full ranges and tweeters.

The question is which box design would give me the best compromise between transient response and good LF extension to 30hz or so.....I have looked at T lines, Labryinth, and horns. Don't want muddy sound with no definition. Primarily for music, with occasional use as a Xbox gaming sound source.

Thanks for any help!

Hi all,

I decided to have a go at a design from Bob Danielak, a screen driven direct coupled EL509. Screen Driven, DC Coupled, Single-ended EL509 Amp



Now old EL509's are hardly available, but Askjanfirst has the PL519. And JJ came up with something they call EL509.
What's the JJ like? I'm inclined to go for the PL519 (I like the top cap), but that would mean an extra filament transformer.

Thanks 😉

In my last order went something wrong and I have 14 pcbs of the actual quasimodo snubber Board in my closet...

If someone wants one...

Pcb would be 3€ plus shipping from Germany...

If there is enough interest I would order the components too and sell the bundle too... Will check cost tomorrow...

Two original, unopened, unused circuit boards for the Pass Zen Single Ended amplifier. Purchased from Old Colony (Audio Amateur Corporations) in 1997. Stored with the full issue Two-1994 of Audio Amateur, and subsequent AA related articles.
Asking $40 shipped (CUS only)


11/3/20 Item is SOLD

I recently obtained a Rega P3 and it has the Elys 2 cartridge. I feel I could get a little more out of the table with a better cart. I am prone to migraines and thus cant have anything with sharp or shrill highs. I like a nice warm sound, but still with detail. My music taste is all over, everything from rock to jazz to country to electronic to...

Anyhow, trying to find a good cart under $500 USD. Some say the 2M Bronze is bright, so Im not sure I want that one. I was thinking of a Denon DL-103r, but apparently its not the best for a lower mass tonearm like the Rega's. Others say you can add mass to the headshell. Seems Id be better off just getting something that is better suited. Also if I get an MC then I have to get a pre amp which is more money, but may be worth it. I've also looked at the Audio Technica VM750SH MM. Would that work well on the Rega? I looked at the Nagaoka MP200 or so, and at first I was very interested but then I read they recommend stylus changes at 150-200 hours. I listen to records a good bit, so that would end up being crazy expensive for me.

Any ideas?

I have two different version on h20r1203 which fake , two core or single core ?

I am looking for a pair of OPTs for my EL34 PP design and the specs with Primary - 6.6k, 4 & 8 ohms secondary and at least 30-40w output.

Any good quality iron and shipped to Naperville, IL - 60564, please send me offer either on used or new ones. Usual suspects of Edcor, Hammond, James etc would be welcome.

Thanks for looking.

I've got a little project going on where I'm feeding an LM393 comparator with a resistive pressure transducer configured as a bridge. I connected it up in pretty much the normal way, using 10k resistors to the inputs and a 10k pullup. From the output, I connected the gate of a n channel logic level FET which in turn operates a relay.

So far so good, the circuit operates in an understandable way. Then I remove the FET connection and it just goes crazy. Turns out the fet gate capacitance is imparting some stability to the LM393 output - and I can "stabilize" it without connecting the fet by adding a 200 pf cap from its output to ground. By stable I mean it apparently goes to within some Vce sat of ground in the low state, then to +V in the high, as any open collector output should.

Without the cap, the high state is some indeterminate DC voltage that I assume my meter reads because of some MHz oscillations going on. I cant for the life of me figure out why this is needed. I'm using a regular press-in 0.1" spacing proto board with leaded components. I picked the LM393 because it's a cheap and effective solution - when it working "right".

I'd just like to understand what's happening with this thing. No spec or app note mentions the necessity of loading the output capacitively to get it stable - only mention I saw was resistors connected to the input should be at least 10k to avoid oscillations. So they're 10k - check - still oscillates without the cap.

Any insights into what's happening with this little circuit would be appreciated! I've got a couple / few hours sunk into re-arranging components, changing the chip and struggling to realize what's happening. I use the other half to compare a voltage across a cap to another voltage set by a resistor ratio - no special 10k input / 200 pf output treatment there; it simply works like a comparitor should.

Analog sometimes drives me nutz... FWIW, the little pressure sensor bridge plugs into the protoboard right next the the dual LM393, with the leads all as short as I can make them. Thanks!

I have some transformers and heat sinks for an amp. If someone around the Methuen area would like to pick them up I will be glad to help them.
1. Nelson set me a 2.5 KVA amp with 35 and 45 volt outputs.
2. I picked up a transformer from Jam when I was in South Carolina. 2 KVA 30 volt secondary.
3. I have a current source Zen amp. Nelson sent me the boards.

If you would like any of these send me the plans of what you are going to build, or the crossover network for you current source amp.
I can put them in the front of the house on the porch. No one will take them because they are very heavy.

((( CLOSED ))) Thorens TD 124 Main Bearing & Spindle

Not needed anymore. My platter was warped!

I need a Thorens TD 124 Main Bearing Spindle. Mine is bent. I would consider buying the complete Main Bearing & Spindle if the price is right.
Shipping would be to my military APO address, or if you are in Europe it can be to my German address.
Michael McChesney

I just tripped out my ps to track down the circuit but I am confused with the rectifier. The red lines is what it is. Are the white lines support to be? If it's wrong, why it works.

The circuit I'm building has a simple change over switch on the screen grid of the output valve to select triode mode or ultra linear mode.
As it's basically switching almost the full HT supply, it will need to be rated for at least 400v dc, though I would not attempt the change with the amp switched on.
I can't find a suitable switch except for industrial control panel switches.
Would I be better using a jumper lead set up, which would mean delving in the chassis to make the change, or is there a simpler solution?

Purchased one of these $20 wonders from China. Sounds real good between my dac and SS amp but too much output so I converted it to a cathode follower.

R13 and R19 stay connected but are lifted from the -28 volt buss. R15 is removed and replaced with a short. R15 is then connected from the junction of R13 and R19 to the -28 volts. The output is then taken from the junction of those three resistors and through C10 which has been disconnected from the plate.

Very simple conversion and sounds good. Much lower output.

Question about the schematic. What is the purpose of R16, the 100k resistor?

1.LUNDAHL LL1674x4
2.6N1-P: 2pcs
3.High voltage output noise: 27µV RMS
4.GE6AS7GA: 24pcs
5.ECC82: 6pcs
6.ECC83: 2pcs

Now that the Lowther America website is defunct does anyone know where to find plans for this speaker? I have done a google search and outside of a Scandinavian web site not much detail is out there.

Thanks.

Hello everyone!

First I must tell you guys that I'm very new at this, so sorry in advance!

I'm starting to put together this Telephone Microphones. They are very easy to do, just grab the two wires from the earpiece and solder them to a 1/4 inch jack, and viola!

The idea es to use it as a lowfi tool, but this earpieces of the phones tends to lead to some feedback so mounted a 100k potentiometer and a capacitor to make a RC lowpass filter to roll off a bit of the high frequiencies...aaaaand the issue appears. When I turn the pot up or down, it hums. When its on 10, the hum dissapears. I've tryed different wirings but nothing seems to work out. The impedance of the earpiece is very low, 20.5ohm, but I've try other earpieces with much more higher readings, and the same happens. Also, I've tried shielded wiring, but...THE SAME HAPPENS.

Now, since I couldn't solve this problem, I thougth that I could make the lowpass filter using a ON/ON switch, attaching the capacitor and a 100k resistor to one part of the switch, so you can select between the "normal" signal or the "filtered" signal.

I calculate that using a 100k resistor with the 2nF capacitor I can get a cuttoff frequency of around 800Hz, wich is what I was looking for.

So I tried to solder the components directly to the input jack to see if it worked out. The resistor in series and the capacitor in pararlel. Aaand it didn't affect the signal at all. I use a 0.1uF cap wich it should cuttoff the signal by 15Hz, basically killing the signal...aaand NOTHING! the signal was still there, unaffected.

So, I really don't understand why it hasn't work. It maybe be the impedance of the mic, but I don't know anything about impedance or how to make it work, I'm barelly know what a capacitor and a resistor do! I'm telling you this because some of you are more experienced and write content that gets my head spinning (I'm looking for an basic electronic course so I can learn propperly) so, sorry in advance.

Hope you guys can help me solving this out!

Thank you!

Hi,

I am new and this is my first post here. Thank you in advance for your indulgence, because I am also new to audio (not to electronics though) and English is not my mother tongue.

In short, I need some help in order to design an amplifier.

Here is the context. I am building an virtual pipe organ, using a ~50 year old electronic church organ. I have removed all the original (analog !) electronics to build my own one. I have done infrared barrier sensors for the keys, managed by an Arduino board. Another Arduino takes the sensors signals as input and outputs a MIDI signal to a Raspberry Pi, the latter containing a virtual organ software (GrandOrgue). The Raspberry Pi is also connected to a DAC board (a HifiBerry DAC+). Finally, I have build a DIY headphone amp based on the CMoy design, with 2 improvements : an op-amp based virtual ground, and a LM317 to further stabilize the voltage provided by an already regulated SMPS. While I can't compare it to any reference (not even a physical pipe organ, because the purpose of my project is precisely to start learning organ), I feel that it "sounds good", with no obvious noise nor distortion. Note: building a CMoy is not in contradiction with being an audio newbie. Two weeks ago, I didn't know anything about headphone amps! I just learnt using Internet resources.

Now to my topic: my organ is working with headphones, I would like to make it work with loudspeakers too.

The orginal organ had four loudspeakers, which I have kept, of course. A quick test with an amplifier I have but that I don't want to reuse for this project (a Yamaha A-S301, too bulky + I suspect it is not in good working condition) showed that the loudspeakers are working well. Plus they probably still have a significant value. All speakers have a resistance of around 7.5 Ohm (from 7.2 to 7.8). I have tested each of them and measured the RMS voltage at the same time. I got quite consistent results: at 5 V, they are very loud, and at 7-8 V it became to be painful. So, in order to have a safety margin, if I design an amplifier capable of 10 V RMS, I will need 10*10/7,5 = 13.3W per speaker.

I think that the orginal organ had a mono output, because the loudspeakers are arranged this way inside: (see attachment).

So I intend to do the following:
[CMoy] -> [Convert stereo to mono] -> [Amplifier] -----> low-pass filter -> two large loudspeakers in parallelSince the same amplifier would drive all speakers at the same time I would need 13.3x4 = 53.3 ~ 50W.

Then I would have to choose the class. I hesitate between class A and class D, but I think that the power is still low enough for a class A amplifier, which would provide the sound quality and simplicity I am looking for. For example, the LM3886 seems to be up for the task, since its datasheet says "68W cont. avg. output power into 4 Ohms at VCC = +/- 28V". Still, I have to read the datasheet in details to check if this is true, because my configuration is somewhat different : ~2 Ohms at VCC = +/- 10V, i.e. less voltage but more current.

I have had a look at a few designs and it seems that many of them include a pre-amp stage. In my case, I feel I don't need it, thank to the CMoy.

For the stereo to mono conversion, I intend to do this : https://www.instructables.com/id/Simple-Way-to-Convert-Stereo-to-Mono/, while I am not 100% sure if it the right way (it seems too simple to be true).

For the filters, I have no knowledge, but I guess that I will have to go through the following steps: 1) determine the response curve of each loudspeaker 2) design the filters accordingly 3) adjust for overall balance. I am not sure what I will do if one speaker is significantly louder or weaker than the others.

The final word: I am not after the highest sound quality using complex refinements, just a good sound for a reasonable amount of money (say less than 100 € of components). I have posted in the "Chip amps" section of the forum, because I guess this is the best path for simplicity, but I may be wrong.

So any advice is appreciated. In addition, a link to a successful project in this forum with similar specifications would be extremely helpful.

Myself and my friend put on occasional gigs where we play classic trance stuff, from around 1996 to 2006. We do this in the back rooms of various bars around Manchester and we have always used rather budget active PA stuff. We've had various different systems over the years from HK audio, Alto, RCF etc.. all 15” or 18” reflex bins with tops, and all fully active.
It’s always done the job for our small events of up to around 100 people but it has lacked that club style 100 – 250hz kick which I think you only really get from horn loaded cabs.

We’d like to take the current global “no gig” situation downtime as an opportunity to make our own PA system, which will not only improve the sound but also give us a bit of branding, having our own system so to speak.

We’ve done a fair bit of research and we are still undecided on what route to go down. Currently in pole position is the idea to build a cubo setup, with cubo subs, kick, and then some custom mids and a compression horn above that. The main concern with that idea is that a cubo 12 set up might be a little small (not sure if it would be) and the 12 (and also the 15 really) doesn’t really seem to go that low. We don’t need to be playing in the 30hz band but we would like solid performance down to 40hz. Seems a bit daft to build a 3 way system that can’t play down to 40hz with authority. We do like the simplicity of the cubo build though, the wide range of driver options, and the looks.

We’ve also considered the tham 12/15 and Mth 30. Someone suggest the FTH12 tapped horn developed by the late Tony Wilks but I can’t find plans for that.

Any help or input from forum members would be very gratefully received.

We’ll need to buy the lot, wood, drivers and amps. Budget is flexible, not massive, but we also know we can’t build this for peanuts. Keeping the weight down is a priority as it’s only the two of us. Load in’s are fine, but load outs are a morale sapper!

We are handy with building stuff and are lucky to have a well-equipped workshop, but we don’t want to spend time and money building the wrong thing.

Many thanks.

Hi my friend has a roland 909 and it needs a new 7 segment LED .
Can anyone help me work out how to find a way to use modern ones or are there NOS places.

Thanks

Hi all and thanks for any help you may be able to offer.

I'm pretty novice in the world of DIY audio but would prefer it people dont try discourage me from trying anything.

I bought a set of speakers at a very good price and in my excitement to get the speakers at the great price and perhaps being overwhelmed by the incredible house I picked them up from I didn't really check them properly which I only have my self to blame.

However I digress, I got them back and realise the tweeters weren't working on all but 1 of the speakers. I sourced replacement tweeters, put one in and it worked fine, but on all the others only a very slight sound was produced from the tweeters. I had a look at one of the speakers and its clear that one of the coils on it has burnt. So from my limited knowledge my conclusion was that I need to replace that coil, and likely a good idea depending on cost to replace the capacitors given that the speakers have probably been over driven.

This led me to wonder, while I'm doing this, is it a good idea to try and upgrade the crossovers, and in this case how easily is this done and what need to be done?

Thanks for any help! Cheers, Mike.