Greetings Friends. I'm curious why one meter, the Klein CL390, can make a measurement when a similar product from the same maker, Klein MM400 can't.

I built a single-ended directly-heated-triode amp using 6B4G tubes. Each output tube has its own, simple DC rectifier fed by a dedicated transformer Like this one. When I was checking the filament voltages, I noticed that the MM400 could not find a voltage pins 2 & 7, while the CL390 quickly showed the voltage. Why is that?

The filament of these tubes has 2 voltages across them - the heater voltage, 6.3v here, and the cathode voltage, 45v. Did the MM400 get confused?

thanks!

w

Greetings everyone am looking for some Toshiba TA7136P2 Pre-Amp Dual power supply if anyone has some to sell.

Many thanks for your time.

John

Hello!
Who had built a bass tower with multiple AE DIPOLE 18

https://aespeakers.com/shop/dipole/dipole18/

It is going to cover under 160Hz.

Any suggestions?

Do you have plans to share for the application?

Thanks!

https://sarahconstantin.substack.co...&r=451zf&utm_source=substack&utm_medium=email

I found this substack article easy to understand and helpful. Moderators feel free to move as appropriate.

Years ago I bought XLO and Audioquest RCAs. I also made a few pairs using OCC pure silver wire. Guess the snake oil got me. Now I need two 8ft RCAs and remembered I have lots of CAT 5E. So, I looked up its spec. and it states it must user pure copper wires and capacitance at 800 Hz is 52pF/m, so that would be about 17 Hz pF/ft. Seems like that might make a good RCA cable. I'd terminate it with Eichmann silver bullets that I also bought while under the snake oil spell. All thoughts would be appreciated.
Thanks

Hey all. Hope this is the right place to post.. 😀

I'm in a situation where I have a built-in 50-foot coax SPDIF cable that needs a termination on one end changed (meaning I cannot buy a custom cable because physically replacing the wire is not cost-effective). The end needing a change is to be connected to the digital XLR (AES/EBU) output of an RME MADIface XT audio interface. In the manual they specify how this can be done (see B&W image), by soldering pin 2 to the core of the cable and pin 3 to the shield, and leaving pin 1 disconnected.

My questions, being a total newb, are:

1) Is it important that the lengths of wire between the XLR solder point and the point where wire stripping ends be as short as possible? Any recommended length?

2) Are there any XLR connectors that would be better suited for digital signal over others?

3) Maybe it's overkill, but is there a solder type recommendation for digital audio? Some better than others?

And any other tips you want to throw my way. I literally have never soldered before so this is allllll new.

Thanks 🙂

Hello,

I search the Sugden A28 II schematic for repair this one.

Thanks.

Hervé.

I have a pair of Sugden P28 Amplifiers, one of which is very sick and the other slightly so.
Anyone have schematics and/or know which preset does what and what how they should be set?

Hoping someone can help

DC.

del

del

del

Hi guys I'm about to recap my 8000A can I have opinions please Elna silmic 2 or Nichicon ues bi polar muse cheers

Planning to get a Wiim Pro and plan to connect it directly to a power amp, I know the Wiim pro has a digital volume control, but since i would be connecting it directly to a power amp (Rotel RB 1090) , I am afraid that there would be a possibility that the remote or app used to control the power amp might go berzerk and go full volume on the power amp. I would like to insert a potentiometer in between the Wiim and the power amp, what value for the pot should I use? The power amp has an input impedance of 33k ohms, sensitivity is 1.8v. I know the Wimm pro's analog output is 2.0v

Hello,
Have undertaken to repair this preamp for a friend, are missing both user manual and schematic (have downloaded the Minuet schematic published here)
Could anyone help I would be very happy.
brutus

I noticed yesterday that the DIP package version is end of life status, last time buy
OPA134PA is still active
OPA4134 is only available in soic-14

Hello,

I'm currently building an active speaker and have run into a noise issue. Here's a brief overview of the components I'm using:

• Two TPA3255 amplifiers (Chinese boards)
• An ADAU1452, primarily as a crossover
• Two PCM5102 to bridge the ADAU1452 and the TPA3255
• A PCM1802 as the analog input for the ADAU1452

I'm powering the amplifiers with a 38V LLC power supply and using an isolated power supply for the digital components. [You can view the setup in the attached image.]


The main issue I'm encountering is that the setup is quite noisy. I observed that if I maintain the isolation on the power supply, I experience an intensely loud noise that has a significant swing. To address this, I connected the grounds of the isolated power supply, making it non-isolated. My assumption was that the noise might be due to the ground connection between the PCM5102A and the TPA3255. With the grounds connected, the only grounding occurs between these two components, potentially leading to the noise swing. However, this is just a hypothesis, and I'd appreciate any corrections if I'm mistaken.

This leads me to my main question: While I've seen numerous recommendations to use isolated power supplies, especially for separating components like Bluetooth modules from amplifiers, I've noticed that the isolation often gets compromised due to the common ground between the pre-amplifier and amplifier. In my case, using the isolated power supply seemed to introduce more problems. Can anyone share insights or solutions based on their experiences with similar setups?

P.S. I am an electrical engineer with access to measurement equipment. If specific measurements would help diagnose the issue, I can provide them. My expertise leans more towards digital systems, so I'm speculating that the noise problem might be related to grounding or another analog-related challenge.

Traditional biamplification consists of a preamp, an active crossover, and two power amplifiers. I wonder is it possible to use two integrated amplifiers instead of pre & power amplifier combination?

Please see the diagram on attached. The first integrated amplifier (Int.1) will be responsible for preamp task and also high-pass amplifier. And the second integrated amplifier (Int.2) will be responsible for low-pass amplifier.

In addition, the low-pass amplifier (Int.2) should be connected input at the “main-in” channels only or could it be connected to the RCA inputs, i.e., CD, tuner, aux, tape in, etc., in order to use the volume knob on Int.2 as a bass level adjustment?

Hi!
Are anyone know similar to QUAD 405 amplifiers with based on the same current-dumping principle as the 405 ?
commercial production 1975 - 1990

Hey,
I’m building some amplifiers that require 20 va xfmr’s. I’m hesitant to use eBay or aliexpress as I’ve had issues with them before. So, where can I get these from a reputable retailer? I’m in the USA which apparently has limited options. Please advise.
Regards

Hello
im working on a Yamaha MX-1000 right now and got a weird problem i couldnt fix despite trying for hours.

This amp uses a class-h topology with +-40V and +-90V rails.
On the right channel, the negative supply is stuck at -HB (-90V allways on the transistors) for some reason. it should be -LB.
+LB and the other channel work just fine at +-40V

ive taken out all transistors multiple times, measured them, bought new ones and put gain matched ones in there (+-10%)
i looked at every solder joint, redone the whole right channel in the end..
tested every diode.
also checked the resistors and connections inbetween as best as i could.

the power transistors are new, all tested and gain matched. 3 PNP, 3 NPN for output, 2 PNP 2 NPN for high rail switching.

This is the schematic of the Right amp board:


this is my problem area:

1, 2, 3 ,4 are identical to the other channel.
the Rail that feeds Q320 Q324 and Q328 on the left is stuck at -90V, it should be at -40V.

i checked (and later replaced for good measure) Q350 and Q346.
also measured every resistor on this board, all are fine.
All diodes are fine in their normal direction, all zeners are fine in their reverse direction.
no caps shorted, non are noticably leaky.

Q342 is good
Q338 is good aswell, so is D324 (12V zener) and Q332.
aswell as D328 (24V zener) and D332

(flipped image..)
on the thermal image, you can see the right lower gets warm, thats the Left channel -HB APS
its dead cold on the left side (right channel) but the output transistors get quite warm at 90V and 22mA biasing..



i wrote down all differences to the other channel

Right channel | Left Channel
across D319/D320 87V vs. D316/D315 23V
across R392 71V vs R391 7.7V
across Q332 Vbe 0V? vs Q331 Vbe 0.61V
(but weirdly when i measure from ground to Q332 base its 87V, but to Emitter its 80V. maybe the internal multimeter resistance is playing tricks?)
across Q332 Vce 80V vs Q331 Vce 24V
across R400 and 396 0V vs across R399 and R395 50V

seems like Q332 isnt turning on.
its a 2SC2705
when i take it out, it measures just fine using every transistor tester i have. tried with a new one, no luck.
maybe because Vbe is 0.. but where should it come from?
Both diodes in parallel are 1s1885.
and measurements past R392 are identical to the working channel.
i checked the positive HB side aswell maybe it affects the negative, but didnt found any obvious problems.





Board pics: (too big to upload here)





im stuck, can anyone help?

If you add a resistor between the amp ground and the incoming ground, then the negative feedback input is also referred to it.The positive input must have attenuation of the same ratio as the feedback to reject the voltage across the GLB resistor as common mode. The positive input attenuation must be precise or else the two channels crosstalk via GLB resistor 10ohms in bellow circuit.
If I install a standard volume control, this ratio will be modified.
I didn't find any example to follow, if you know any, please show it.
I designed one bellow intended for the "Bameless CFP" maybe it can be used for other amps. Max. attenuation is -60db.
Lower channel is without volume control as standard GLB.
This is applied on amp with FET input transistors.

Hello fellows!! I've recently got into cassette tapes and would really like to build one from scratch. I managed to find the Toshiba TA7668BP, which seemed to have some documentation and a reliable source of purchase. However, I'm stuck reading the diagrams as I don't quite understand the "moon-shaped" and "headlight" symbols in left side of the diagram. I tried to research here and there but nothing pops up. I suspect they are playing head and erasing head but I'm not sure and wouldn't want to risk damaging the heads. If anyone has seen anything like this or knows what they represent, could you please help me out? I've attached the reference circuit as well as pin definitions if that helps. Huge thanks to everyone!

Hi DIY'ers,
I have a pair of the aforementioned Infnity cabs with the wooden trim around the outside edge of the front and at the bottom and I'd like to sand them down a bit and give them a nice matte finish instead of the current high gloss lacquer (which has it's marks). Does anyone know if it's solid wood or just veneer over particle board, or MDF?
I'd prefer not to find out it's veneer after sanding them down.

Multi material loudspeaker enclosures

I would like to post this here because it might be of interest to builders, and has only been mentioned in the full range SEAS build.

The ideas are applicable to many loudspeaker enclosures. I am not claiming anything original, just an application of a number of known techniques to improve the enclosure. It was done in the hope that it would improve on an existing enclosure and it did. A 62L sealed box for the SEAS Exotic was replaced by a similar volume enclosure and the same drive units. The original box was strongly made of 18mm birch ply to SEAS app note. The second one (still based on 18mm birch and hardwood ply) follows these guidelines;

• A different shape to alter the flow of pressure around the speaker
• Division of panels into smaller varied sizes and bracing
• Multi material layers construction using stiff and also “lossy” layers
• Extra thickness front and back panels
• Anechoic style foam wedges on the back to reduce reflection to the front

The method;
Make the angled shape by assembling flat panel sections to ribs (like boat building) and put lengthways braces to support the sections.

Stick 1mm commercial rubber sheet to the panel sections with plentiful spray contact adhesive. (PSCA)

Cut rectangular tiles and stick with PSCA. (I used a stout 8mm tile)

Cut 15mm wool felt to shape and fix to sides and ends with, yes! PSCA.

(So we have ply, rubber, ceramic tiles and wool all with lossy adhesive between.)

Cut from 50mm thick foam a double wedge shape about 80mm tall by holding a template on it and band sawing. This only took a few hours to produce about 120 pieces which were just pushed down onto PSCA.

The method is surprisingly easy when once the ply fames are done. Cutting the rubber and tiles was only a matter of a few hours. The spray adhesive was also very quick to use. Fitting the thick wool felt was a slower job. The finished sides were supported by clamping bracing pieces between them and the ends glued in. Then the back and front.

The drive units were installed into the new enclosure and initially they sounded quieter is if something was missing. It became clear that they produced less self-noise and the music was cleaner and clearer. I have been using them for two months and the system sounds very good. The same drive units sound better in the better cabinet.

I'm quite baffled by these tubes and what their actual dissipation rating is. They are spec'd as a 60W tube, but when I bias them over 40W on my newly build SE monoblocks I start seeing signs of them red plating on one side of the tube. At 50W they start getting some serious looking red plating. I biased up some cheapo muzishare branded KT88 tubes at 90% in the same amp and they don't show any signs of red plating. Obviously in a SE amp biasing the tubes cold has a major impact on the power they produce, I built this KT120 amp to try to get more power than my KT88 amp, which it does (and sounds great) when biased up but I'm afraid it's going to kill the tubes.

I have a quad of these KT120 tubes and they all behave this same way. Is this normal and are these tubes really just KT88 tubes in a bigger bottle or?

Hi Everyone,

For the past 3 years, I have competed in Car Audio shows and did well in the area of bass with my lexus is250 (2006) and the original ski hole (140db-144db of front windscreen). I started my journey in SQ last year with Deaf Bonce AP Neo 6.5s and W81 8s. The car sounds really good and all, but I would like to upgrade to 8s only and was wondering if it makes sense to modify my door chassis to take 8s and fabricate the panels. The reason for this, is to ensure I remain within the cone area of 60in - as part of my vehicle class (stock with minimal modifications). What do you think?

Another question, is which 8s do I go with for midbass and midrange to have the best overall audio effect at low and loud volume. I was thinking of either the B&C Speaker 8PE21 or Eighteen Sound 8M400F for midrange and Beyma 8MC500Nd for midbass. What do you think?

Thanks for any input or suggestions.

Hi All. Great forum. I have a Donegan Optivisor with various lens plates. One of them the DA10 is never used because it is extremely powerful.
For Microscopic work I suspect. It may be of use to someone here who uses an Optivisor. This is the uber quality ground glass plate not the cheaper lite acrylic one.
Best Regards, DD

I have a couple of Fostex FD600 lying around and am considering building a couple of speakers from these, preferably with active sharing. Does anyone here have input/experience with these drivers and what can match? Maybe the Celestion H1SC-9040 can fit as a horn? They are essentially reasonable.

Hello everyone

I'm looking for help on replacing an old speaker set.

I have recently gotten an old speaker set from my dad. A pair of AKAI SR-H310's (Photo attached).
As you can see they aren't in the best shape.

I am looking for help on how to replace these speakers and with what speakers I should go with.
Or if it is beter to just buy a kit (speakers and cabinet)?

Info:
Sizes of the speakers:
Tweeter: 65 mm
Mid: 100 mm
Low: 200mm

Impedance: 8 Ohms
Rated power in: 45W
Max. power in: 55W

Couple questions:
I was wondering if it possible to find some replacement speakers to put in the cabinet?
Is it worth looking for replacements or should I buy a kit somewhere?
Are there any sites/service you can recommend on this topic?

Could you guys give me some pointers to where I should look for replacement speakers and what to look out for?
Suggestions are also welcome.

The speakers are going to be hooked up to the AKAI AM-U3 amp.
(See photo attached)

I do not have any experience on this topic so any help would be appreciated.

Thanks in advance
Michiel

I’ve recently started a speaker building project and have reached the point whereby I need to make some frd and zma files to further my design. I’m local to the south west of the UK and was wondering if anyone on here was nearby and had the tools to do so or knew someone nearby who did??

Does anyone know if the bootstrap electrolytic on a chip amp like TDA2004/5 has an influence on the sound concerning its quality?

Can it make a difference if it is bipolar or even being parallel with a foil C?

I design and sell a lot of model railway electronics.
I build hundreds of pcb's a year.
For some reason I have now become aware that I put all resistor in same way around as colour codes work.
On my pcb designs I like to put all my resistors in a single column down the pcb.

Can anyone direct on where I can find a transformer for this unit. I searched and cannot find anything.

I bought a Chinese DAC which has two NE5532 op-amps for I/V and two 470uf 25V capacitors are driving these op-amps as far as I could guess (by tracing the lines on PCB from the caps leading to op-amps). These two capacitors started to bulge in a matter of days. I thought I was unlucky - these must have been defective. So I bought the exact same DAC board again and installed it - and voila, the same two capacitors started to bulge again in a matter of days!

Maybe the voltage is not sufficient ? Out of curiosity I de-soldered the two problematic capacitors and soldered more expensive high quality Panasonic caps, this time with 470uf, 50V (double the voltage). After about a few days, sure enough, they started to bulge again. This is just so weird. It is always these two that are next to the Op-amps. I don't think op-amps are responsible because each time I replaced the DAC board or capacitors, I used different op-amps.

Can someone offer any possible explanations and solutions for this problem? When I touch the caps, they are barely lukewarm (not hot at all). So this can't be due to overheating or being overdriven. It is especially weird because it takes only a few days for this to happen. Would it help to try with 1000uf, 50V caps this time? (Just stabbing in the dark out of desperation)

p.s. I circled the two cap locations, one spot is de-soldered. You can see the bulge on the cap although it is not that obvious from this viewpoint. Please disregard opposite polarity of the cap placement - I just placed the desoldered cap on that spot in order take the pic

Was browsing for speaker's ads and found this one (I usually have insomnia and nothing better to do at 3AM, apart from browsing really old ads):

https://www.usaudiomart.com/details/649268271-energy-audis-sexy-a32-floor-standing-speakers/

I noticed the bindings, so I searched for documentation, and I got intrigued by the manufacturer's (apparent) lack of coherence:

This definitely does not make any sense to me:

Bi-amping usually means, as far as I know, having two amplifiers, one for the high, and one for the low frequencies.

On this particular case:

Frequency response
30-25k
Crossover points
1800hz

The manufacturer states that two amplifiers must be used, one for the low and one for the high frequencies, but looking at the image (image 4 on the PDF), they state that the left channel goes down and the right channel goes up (lower and higher frequencies respectively)

I'm not aware of any traditional amplifiers dividing channels by 1800hz, or I might be wrong?

Biamping is not meant to be used with active crossovers before reaching the speakers?

This configuration looks pretty useless to me, unless someone much more educated on this subject than me, states it otherwise.

So:
What's the point in biamping using full range on both frequencies?

Hi first post, I just wanted to share my experience with a $2 headphone amplifier PCB from AliExpress,

I was looking round for a cheep amp that I could connect up to my phone to give it a little bit of power so it would drive some cheep cans (Behringer HPS3000) anyway's I stumbled across a listing for a very basic circuit that used a TPA6120 quite an impressive IC, I had a quick look a the data sheet and the PCB layout appeared to match the manufacturers default circuit diagram. The tpa6120 needs no output coupling capacitors, so basically the PCB is just a few resistors and some filter caps for the power.

I got the hole thing wired up (after wireing the input to the output pins swearing at it and starting again) I got the little amp to start cooking. Quite literally I burned my thumb on the IC and had to mount a heat sink on the little fella to stop him burning up.

So my assumption was that it was oscillating. so I worked my way though the circuit drawing a circuit diagram while comparing to the data sheet. I'm very amateurish so this took a lot longer than I really expected it to, nothing! could not find a thing wrong with the wireing of the input, feed back or output.

By this stage I'm really doubting myself, maybe this IC needs to be mounted to a heat sink ? Maybe it's a fake IC ? Maybe I'm just a idiot ?

I found the manufacturer of the IC actually offers feedback on circuits, wow amazing ! surely they can help me because I have to get to the bottom of this now, but first I might as well draw a diagram of the power to the IC so I could upload an image of that too.

2 surface mount ceramic caps and 2 electrolytic capacitors so simple! The first electrolytic had the postive wired do the positive supply, and the 2nd capacitor had its positive wired to the negative supply.... Wait WHAT ! hours and hours I've spend on this, and all it was was a cap wired backwards !! /smashes head into table .

I don't know what the moral of the story is. But I had to post this somewhere and now I need a strong whiskey

So the turntable in question is a pioneer rondo 3000x/y.
Everything seems to work fine except for speed.
My ac power is exactly 50Hz. And I've sanded off the 50 years worth of shmuts off the belt drive spindle...
But still to my ear its running noticeably fast. Basic app test shows 33.9rpm and 46.0rpm (both +/- 0.1rpm)
I cant see any adjustment pots on the motor
I tried to find a service manual but was unsuccessful.
And I've tried to google 'speed adjustment' but still couldn't find anything.
If there really isnt any speed adjustment, is it just a case of replacing dried out lubrication?
Thanks 🙂

Hi Guys

I hope you don't mind. I'm not a audio DIYer but you guys are full of knowledge I was hoping you could answer a simple question for me.
I have a pair of active speakers that state the input impedance is 10Kohm per leg. I'm not used to seeing the "per leg". Does per leg mean the input inpedance is actually 10+10 = 20Kohm. I need to know as was hoping to use with a tube pre-amp, they wont work very well is they really are only 10Kohm.

Many Thanks!

I unfortunately broke a speaker binding post (red) on my ROTEL RB-1590. ROTEL's parts webpage shows the terminals, however, ROTEL will not sell the binding posts and require the amp to be sent to a repair facility. The part number is: C-4717A01.

Hopefully someone can recommend where I can find the part new or used.

Thanks for reading!

This is my 2019 Toyota Tundra.


I will be starting a system install today. I have been acquiring the components for it over the past couple of months now and I finally have what I need to start the install and the rest will be coming today or Monday.

There will be some tricky parts to this install especially with the subs since there is little room for them. I'm debating whether I should cram a narrow wedge box behind the rear seats like so many other Tundra installs I have seen on youtube that leave the subs pressed right up against the back of the seat or do a more serious involved custom install that requires me to cut into the factory installed foam floor riser under the rear seats and use fiberglass to build boxes for the subs between the raised mounting sections of the trucks floor. This would give me upward firing subs under the rear seats that won't be smashed right up against the seat but it will require quite a bit more work and it forever alters the "stockness" of the truck. The subs I have chosen for this install are two JL Audio 12TW3 shallow mount drivers. These are some very nice drivers and are nothing like what I expected from a shallow mount driver. These things are going to bump. They should be quite musical too as JL Audio gear is always top notch and that is the reason I went with them. I hadn't heard any of the many different manufactures shallow mount subs before so i have no idea how any of them sound but I do know how JL Audio subs in general sound so I figured if I'm going to pull the trigger on something as expensive as subs I better have a general understanding of how they are going to sound before buying them so I went with what I know. At this point I'm leaning toward installing them in the floor but that might change.

My goal for today is to get the back seats out and start applying the sound deadener to the rear wall and possibly the rear doors as well. I have some very nice set of CDT ES-6CX coaxial drivers coming today or Monday for the rear doors plus I will likely put a small tweeter up in the door panels where there is one now as part of the stock system.

If anyone else has installed a system in a second gen Tundra I'd like to hear what you have to say on the subject. I'll update this as I progress with pics.

Cheers.

Hi everyone, I have a samsung wireless sub that I'm trying to re-purpose and add a 3.5mm jack to. The problem I'm running into is that the wireless chip seems to only have options for digital in for something like usb. The wireless chip on the sub is the WSM520V. I've included photos of the board the chip connects to and if anyone has any suggestions on where I could insert a analog line in connection I would really appreciate them.

Thanks!

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thoughts from you smart guys? 🙏🏻💚

Hi,

I would like to know if you have some experience with Heissmann Acoustics.

I've contacted Alexander from Heissmann Acoustics, and he has been very helpful, and he also seems to know very good his trade, but since I am not from Germany nor Europe, I don't have many references on his work.

I saw the comparison on the DXT vs the Neumann and it looks very promising! But what about the Cinetor? I am looking for a speaker for home theater (5x identical speakers) and the DXT Mon 182 seems a little steep price wise... besides that slanted baffle! I am not that skilled with my saw.

Anyway, any comment on Heissmann Acoustics would be greatly appreciated!
Also, If you know of any other recommended DIY home cinema speaker, speak please!

EVERYTHING WAS SOLD

Hello.
Taken from som JBL Ti speakers tunned, for sale:

4 units JBL 806G-1 Midwoofers. Perfect condition. Outer diameter 190mm.


A pair of tweeters JBL Ti025k in good condition althoug some marks in the domes as can be seen in pictures. Outer diameter 100mm. They measure and play perfectly well. The domes can be swapped:
https://www.toutlehautparleur.com/diaphragme-audax-tw025a8-tw025a14-et-ti025k-4-ohm.html










If interested, PM me

This what the rail ripples look like with a standard psu for an amp 25Hz current shown bellow.

Here what a semi floating (at low frequencies) look like with 25Hz using equivalent capacitor.

Hi everyone, this is my very first thread.
My father and I are building a DIY piezo system to amplify my upright bass.
We've already made the pickup, now we need a buffer preamp because obviously if I plug the pickup straight to the input of my amp it sounds like absolute dog ****.
I've already tried googlin' some schematics, but I couldn't find any true solutions. I'd like to make it in a pedal format to include it in my pedal board for gigs and I'd also like it to be powered by a DC adapter rather than a 9V battery like all the designs I've found online. It'd be nice to have a HPF pot as well.
Thanks in advance for your help.

Selling a single midbass horn together with one Oberton 15NMB600 driver. Developed together with Bjørn Kolbrek (PhD in horn theory and author of "High Quality Horn Loudspeaker Systems: History, Theory and Design").

Measures very even and needs little EQ, and has a constant directivity of approximately 80x50° between 200 Hz and 1500 Hz.
The horn also avoids the floor bounce and measures therefore amazingly flat in the room.

A few pictures:






Dimensions:
Width: Max 122 cm
Height: Max 89 cm
Length with rear chamber: 120 cm

Rear chamber is built with a sandwich of two layers of birch plywood (2x 10mm or 12mm, can't remember exactly) with viscoelastic glue between and the horn with 21mm birch plywood. The rear chamber has a 2-pole speakon connector.

It's possible to buy a second midbass as well. However, the appearance will be different than this one and price will be higher. Or perhaps you can use this a center speaker.
Take note that shipment from Norway to the USA can be very high. Shipping to Europe is considerably less. Will need some time to pack.

Measurements here: https://www.soundlyvisual.com/index.php?threads/vera-audio-midbass-horn.35/

Asking price: 13000 NOK (approximately 1129 euro or $1206 plus freight cost. Or you can give a bid.

Contact: info@lydogakustikk.no

If I change my Altec hf driver's diaphragms from 8 to 16 ohm, how much effect on the crossover point can I expect ?
I am using a 1st order XO with just a 5uf cap .

Hi,

This is a 2 part question. I have a SB20FRPC30-8 full range driver and 2 SB20PFCR-00 passive radiators.
My plan is to build (will do calculations) a box which is slim (depth), but it could be made pretty large regarding height/width.

Because of the aesthetics, I want to do PR - FR - PR next to each other, vertically.
And also because of the depth there is no way to mount them on the sides.

Question 1: Are there cancelation problems if I mount these 3 in the positions I mentioned?

Question 2: Let's say in the future I hook (multiple of) these up to a 5.1 amplifier and cross them over at 80hz or 100hz, will the PRs still have their function or should I just go for sealed then?

Btw, I'm an absolute beginner. Know my way around making the cabinets with MDF but have not done anything more advanced regarding crossovers etc.

Thanks for your time!

Hello,

I recently popped the lid on my ares2 to photograph the chip for upgrade and noticed 3 x 47uf 25v Elma’s and 1 x 1uF 50v Wima cap per channel….. and I got thinking..😝😝 I wonder if it’s been done? Googled the crap out of it and couldn’t find anything so here I am

A pair of brand new Hashimoto H-EQL inductors.

Asking $550 or best offer.

Hi,

I would like to know if anyone have experience with PCBs with immersion silver vs immersion gold. Is the silver plating offer a better conductibility ?

It doesn't have a big difference in price. I'm asking because I have virtually no experience with PCB manufacturing and need what could be the best choice for an SS amplifier PCB.

AISIN TAKAOKA CO., LTD. - TOAC HiFi Rack
Aisin Takaoka manufactures engine, brake, and automobile parts from a global production network of 24 companies in 7 countries around the world, using casting technology and plasticity technology. (Sister company of Sun Valley , owned by Toyota Motor Corporation (24.8%) · Toyota Industries (7.68%)





Two arm boards: SME V and SAEC + WT4700

I recently constructed an LDR attenuator and volume control from Tortuga Audio. I was rather surprised and very impressed once I connected this up in my music system, replacing mono series resistor attenuators in each channel. The series resistor attenuator is a very purist connection between player output stage and amp input stage, a varied series of resistors and a switch contact. The music was good and I thought it would be hard to improve on.
I constructed the LDR unit mostly out of curiosity. I have read about them for years, but nevertheless a lot of things get talked up. But some times curiosity gets the best of everything.

Much to my surprise, I found that all the comments on LDR attenuators were not really exaggerating anything. The channel balance became more precise in that the music images became tighter and more focused from what already were tight and focused music images. Bass response was more pronounced and deeper. Dynamics were much more, as in the softs were softer and the louds were louder than before. The dynamics were the first thing I picked up on and then I began listening for other things.

Well that's all good and all, and then I immediately posted about the build here, trying to share my profound new enlightenment, as one is likely to do in such instances.

Now, I occassionally browse the threads about LDR attenuators and volume controls looking at what others have done, and reading all the arguments by those who think LDR's are all a bunch of rubbish and unfit for such an application and implementation such as this.
I really like the latter postings. It is clear from reading that the posters have no experience with LDR attenuators and volume controls. But the posters do seem to have profound knowledge about LDR's and why they are no good for this application.
But all the designers know the foibles of LDR's and their shortcomings. It's just that they know how to use them in an application for a specific purpose.
Theory be damned, it's the implementation that matters. And in the case of LDR's the implementations are really good.

For the curious or anyone wanting a simple project, constructing one of these is a real good use of time and money with benefits unforeseen.
While I went with Tortuga, there are other less expensive options. They all have their followers here.

I've been adding absorber panels to a room trying to damp reflections and the room decay time. This works and the results are in WideBand Absorber Panels however they are not practical for VLF (<125Hz) as the structures need to be very deep.

The "CABS" schema uses 2 source and 2 sink drivers in an attempt to suppress reflections and reduce the room mode decay times. CABS is described in :
A. Celestinos and S. Nielsen, “Controlled Acoustic Bass System (CABS)—A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms,” J. Audio Eng. Soc., vol. 56, pp. 915–931 (2008
Nov.).

Does anyone use this, and does it help ?

Hi,

I’m currently in the process of doing a Matchless Spitfire build. My concern is regarding the primary impedance of the OT. I’ve read through as many of the threads I could find on the subject but don’t thing I found a definitive answer.

I’ve read several times that part of the “Spitfire” sound is the 4k primary impedance of the OT that Matchless uses rather than the typical 8k for a pair of EL84’s. So I purchased a Hammond 1615A with a 5k primary and 4, 8, & 16R secondaries. According to other threads, this OT has been used by a few people for a Spitfire before.

My question is, do I use the 8R tap with an 8R cab? Or do I need to use the 4R tap with an 8R cab to have 10k on the primary? Not sure how Matchless might have had this setup.

Any help would be appreciated.

Thanks

Hello, I have a skar SKV2 1500 and over the weekend my ground came loose on the amp and I’m assuming the amp went into protect mode. After reconnecting the ground, I am no longer getting any output. Any advice on what board components may have been impacted? I attached a video of the board, but probably doesn’t show much.

I recently purchased an Omnimic V2 off of ebay and have been trying to measure a 3-way design to start my crossover build. In every measurement attempt on all drivers in my possession, a sine sweep shows the high frequencies are drastically reduced at around 9Khz (with almost no content above 10Khz). I'm trying to determine if the Omnimic is working properly or if there is something wrong with both my tweeter & midrange.

I downloaded the Omnimic calibration file, so that shouldn't be a problem. Does anyone know how to test this mic to ensure it's working properly?

Hello,

I have a simple question about a push pull output transformer.

For example, when I go to Hammond, say one of their PP OPTs has "4000 Ohm ct" impedance on the primary side and 8 Ohm on the secondary side. My question is exactly where you get this 4 kOhm impedance on the primary side (assuming the secondary load is an 8 Ohm speaker). Is it plate to plate impedance (so that plate to center tap becomes 1 kOhm) or is it plate to center tap (so that plate to plate becomes 16 kOhm). Since plate-ct is the effective load to each tube, I am guessing that the transformer is 4 kOhm plate-ct (so you can directly use this value on a tube's load line) such that plate-plate is actually 16 kOhm, but I could not find a definite description...

Thanks!

The subwoofer in question is the built-in powered sub in one of my Vandersteen Quatro loudspeakers. The speaker takes four high-level inputs, two for tweeter/midrange and two for bass. The hum occurs if the power cord for the subwoofer amp is connected and either of the two bass section inputs is connected (could be positive, negative, or both). The hum is present if the source amplifier is on or off, and is present even if the source amplifier is unplugged!

Why would a hum occur if a single terminal is connected to an amplifier that isn't plugged in?

I've tried a ground lifer, no change. The other Quatro does not have this issue, and they are plugged in to the same outlet.

Greetings friends. I'm attempting to repair a friend's Ampeg Jet J-12T amplifier and have run into the ditch. Take a look?

Here's the schematic. Amp was originally taken to the shop after it stopped working after a loud hum sound. Tech diagnosed a blown OPT but it was decided the repair wasn't worth the cost, so it came to me. As the amp was built in '96 it's time to replace all the EL caps, but all the WIMA film caps should still be in good shape. I was able to find replacement caps with similar specs for all except the preamp tube cathode bias caps; Mouser only had 22uF 35v caps of the Muse-UES type, which turned out to be Bi-Polar. Mistake?

I also found a broken spring in the reverb tank, and a damaged socket for one of the power tubes:
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After replacing the damaged socket and all the old caps, I put everything back together and installed a new reverb tank. I used a Variac and current-limiter and slowly brought up the voltage to full. After running for a few minutes I shut everything down, let the tubes cool off, and then plugged the amp right into the wall. Using my phone as an audio source I was getting a clean audio signal thru the amp, no hum. Volume, Tone, Tremolo and Reverb all working correctly, and the b+ was 320v, right in spec, As I was preparing to test and record all the voltages from test points, I heard a Pop, followed by an airy, fuzzy hum, and saw a purplish-pink glow inside the 2nd preamp tube. After a quick shutdown and cooling period I pulled that tube and saw a small crack coming from Pin 1. The getter of that tube is still mirror-shiny and it's been 24 hours since this happened, so it's not an air leak. Any ideas on what happened? Bad tube, bad circuit, or something else? Any suggestions, advice, help welcome.
thanks!

w

Hello, I have a skar SKV2 1500 and over the weekend my ground came loose on the amp and I’m assuming the amp went into protect mode. After reconnecting the ground, I am no longer getting any output. Any advice on what board components may have been impacted?

I was building a music enjoyment room and it works well. The dimensions are around 4.5x6.1x3.2m and the room is constructed out of concrete, so quite quiet (even with an outdoor music venue close by) but to get control of reverb the largest surfaces are designed for sound absorption: the floor has a damped layer and the entire ceiling has microperforated sound panels with a layer of cotton insulation above it. Also most of the back wall is a bookshelf to act as a sound diffusor. So I am quite content with the acoustics of this room.

One restriction is the placement of my loudspeaker as there is a room opening to the hallway around 1m from the right corner so the distance of the speakers to the front wall is reduced in contrast to my previous listening rooms. Almost all speakers are designed to have enough distance from the wall in order to reduce the back wave and other early reflections to interfere with the primary sound or at least get enough time difference between the acoustic events.

On wall mounted speakers have no back radiation and that fact is used for a lot of monitoring or mastering rooms but not much for domestic listening. Obviously wall hang speakers require different parameters which may be too restrictive for commercial manufactures (with a few exceptions) but for DIY it should be more an opportunity than a restriction. I am thinking of a wedge shaped loudspeaker (25-30º) either close or direct at the corners. My present speaker design is vented but as on wall close to the corner room gain should be much more significant at 1/2 to 1/4 space so a closed box design may be better.

Playing with REW (which is restricted to .3m as a minimal distance to the the front wall) a distance of around .6m to side walls should work. One issue I try to find out are early reflections from the side walls (obviously no issue with front wall) with would reach the listening position between 1m and 1.8m from the corner so no issue at the hallway side (opening there) but on the left side. Would that be a significant issue? I was thinking one could design some sound baffles at the side of the loudspeakers even have a small gap between loud speakers and the side walls with some sound absorber stuffed behind. Maybe only beneficial for secondary reflected low frequencies but not too much early reflections. So I'm thinking of wedge shaped speakers direct in the corners (the easier design but no way to adjust the distance to side walls later) or just similar but smaller wedges close to the corners with or without some corner sound treatment.

Hey there,
I have two old Grundig dynamic mics (GDSM202) that as far as I understand employs a Sennheiser capsule.
One of those mics wasn't working and I ended up extracting the capsule from the housing. Now I wanna test it and can't really figure out how to wire it to an XLR.

If anybody can give me some guidance as for how to wire it the right way it'd be highly appreciated.

Thanks!

Hey guys. I've finished building six sets of speakers using advice from this site - so a general thanks to everyone for sharing info!

I have a new project in mind, and after seven or eight hours of research I'm still not clear on what the key factors are in choosing appropriate exciters for a given size & density of material.

I'll keep my two questions short and sweet:

1. I have four 1/8" baltic birch artists panels mounted on pine (I think!) frames that are 3/4" thick and 1.5" deep (see image: https://www.canadaoncanvas.com/images/articles/wood_art_panel_front_back.jpg). Two frames are 20"x20", and the other two are 24"x24", and the plan is to use one of each size for the L channel, and the other two for the right. Any suggestions on what kind of specifications to look for, or any brand/model suggestions?

2. Is it totally crazy to attempt to mount multiple bass exciters on a solid core antique hardwood door instead of purchasing or building a conventional subwoofer? If there's a good chance that setup would produce some decent sound, any suggestions on type and quantity exciters for such a thing?

Sound quality is a much higher priority than budget. And I'd love to figure this out for myself if anyone has a decent resource - I'd definitely prefer to learn rather than mine you guys for suggestions. 🙂

Thanks so much!
Ash

Dear forum.

I'm working on the "futile" project of a discrete opamp 😉

I'm looking for a good list of currently available SMD BJT transistors.

I was starting out with BC860C / BC850C, which overall I would guess is a good option, with low noise and good linearity.

I'm working on 3 stages; input, VAS/gain, and emitter follower/buffer.

I want to end with a design with relatively low overall distortion, but more important which is predominantly 2. order.

I'm pretty far with the design (LTSpice), but would like to tweak further, with choice of transistors in the different stages.

Input and VAS is PNP, buffer output is push pull NPN/PNP



Does anyone have a good short list to use?

Thanks 🙂

Hello!

I am hoping there is someone who can assist me in this little fun project I'm working on.

So I'm taking a Behringer Uphoria UMC202HD and trying to add these VU Meters to meter each input directly.

The VU meters I'll be using are these cheap VU meters I found on Amazon.

Each input already has a signal/clip light so I figure I can just replace the two lights with VU Meters.

Obviously, it's not as easy as that. And honestly, if it came down to it I'd just be open to having it meter my main output instead.

Also another note, I'm pretty sure these VU Meters require 12v power and I'm almost curious if I can tap into the USB Bus power of the interface to get that or if I'll need a separate power supply.

Any and all advice would be much appreciated!!

Hello, I have a problem, the device works normally on the two channels, but when I measured the bias of the KT120
according to Copland procedure, on the first 3 valves it was approximately 0.47V, on the last right V203 valve it was approximately 5V,

clearly the trimmer does not have this range. I swapped two valves, but the problem remains on V203.

I tried to measure the impedance of the resistors in front of the trimmers of each valve with the digital multimeter, on three resistors R120-R119-R220 it was 10 Ohm, on the fourth R219 (always in correspondence with the V203 valve), the message " OL" value too large.

So is the resistor faulty? or could it depend on other components?

Can anyone tell me what type of resistance/impedance/tolerance is the R219? The colors on the resistor are not very clear.
Does anyone have schematics of the Copland 405A?

Thank you

Giustino

Hey guys, wanting to experiment a bit with my active 3 way speaker driver integration. I'm currently running EQAPO and utilizing stacked filters to achieve what I believe is 12db, 2nd order high and low pass filters. This seems to give me good integration with in room response (can't measure outside due to equipment limitations).

My filter settings are quite basic, just picked some easy xover points, 300hz for woofer to mid, 2.5khz for mid to tweeter. I've attempted to utilize higher order filters but always run into dips at the xover points when utilizing the same xover points as the 2nd order filters. Am I correct in assuming that one would need to set the xover points for the drivers so the frequencies overlap? What I mean is that instead of 300hz LP and 300hz HP, I would have to something like 350hz LP and 250hz HP?

My current crossover does appear to give me good integration, I've attached an image. I'm just curious to test the benefits of higher order filters.

Full Disclosure: I'm a mechanical engineer and know next to nothing about audio!

I've been tasked with specing an audio system for a racing arcade game we are designing.

The idea is to keep the speakers very close to the rider in the seat headrest like this: https://hunsakerusa.com/products/hunsaker-usa-gaming-chair-with-integrated-speaker-enclosures (but we will design our own seat)

The more localized the audio is to the rider without bleeding out to the spectators, the better.

The idea speaker size would be 3-4".

We definitely want a "premium sound" to it, but budget and long-term supply is a real concern as well.

I guess I will need an amp and a way to plug it into the micro PC onboard as well.

Any help would be very much appreciated!!

SemiSouth SJEP120R100 Single Ended Follower Amplifier, with Cascode and Choke Load

Always looking for a new diy project, I decided to do something with the two SJEP120R100 that I have. They started out in a diy stripboard version of a First Watt F2J. I really liked its sound, with its lower distortion, compared to the single ended SIT common source amps that I was listening to at the time. Now, I prefer the lower distortion level of common drain SIT amps, having built a few of them. So I decided to try a single ended SJEP120R100 follower amp.

The plan is to house it in a chassis that currently has two channels of a Sony 2SJ28 choke loaded follower. This chassis started out as a 2SJ28 choked loaded L'Amp (single ended choked loaded common source), and then FW F2J before its current iteration. The power supply is CLC, good for 23~24 VDC. The audio choke is Hammond 159ZC, 60mH, 0.7 Ohm DCR, and 2A DC current capacity.

So the plan is to make full use of the power supply voltage and choke current capacities. After some simulations, LTSpice showed that it may be possible for a choke loaded follower at 24V and 2A to output about 15W into 8 Ohm. However the dissipation may be pushing it a bit a around 45W, as the SJEP120R100 is a 114W device. To keep the same power output but with lower dissipation, I decided to add a cascode to the circuit.

The lower dissipation of the 2SJEP120R100 with the cascode in the circuit will also help in another way. When I had the F2J up and running, one of the 2SJEP120R100 had quite high gate leakage current. So running them with the higher dissipation would probably not work as the higher dissipation would increase the leakage current even more.

The schematic along with simulation results are shown below. The results are promising so the next step is to build the amplifier. Hopefully the amplifier will test as good as the simulated circuit.

24v AC or DC? Im thinking about using two of them in mono in an off grid situation running them on 24v Lithium batteries with solar charging. Yes/No?

I have started on the development of a variation of the well-liked (and well reviewed) LSA Signature 50 speaker. It will have an AMT tweeter and an all new crossover and will be called the Signature 60.

Preliminary results are very promising.

Predicted response (blue) vs measured (yellow) response for the crossover. The crossover is my own passive (inverted) quasi-transient perfect Harsch. The hand drawn thick blue line is the tilt of the Harman House Curve” to give a slight down tilt of the response to eliminate listening fatigue. Crossover frequency is near 5.5kHz. I am listening to it and still voicing it. Sound is wonderful. Superb drum kit realism. Vocals midrange are to die for:

Measured Step Response:

I designed the Signature 50 speaker for LSA quite a few months back but it’s finally starting to roll off the assembly line and will be shipping soon.

It’s a 6.5in 2-way bass reflex that uses a premium 28mm silk dome tweeter, and I gave details of some of the measurements earlier in the What’s on the Bench Tonight thread.



Predicted response of crossover:


Step response is quasi transient perfect (inverted due to mic response):



Custom crossover uses inverted passive Harsch topology of my design. All high quality parts like pure copper wire inductors, and custom made film caps and non inductive wire wound resistors:


Impedance as function of frequency shows a true 8ohm speaker with lowest dip at 6.5 ohms above 20Hz:


Here is the measured response (yellow) overlaid with the predicted response (blue) based on raw measurements from in-cabinet measurements of the drivers to account for driver offset and cabinet diffraction.



And here is the measured harmonic distortion as a function of frequency - measured at 2.0Vrms and 0.5m:


You can listen to the first sound test here:
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First review is now in from Tone Audio:
https://www.tonepublications.com/review/the-lsa-signature-50-speakers-2/

Here's a dumb question:

I've just built a passive sub with the Scanspeak 30W/4558T00. I'm using it with the TDAI 1120 from Lyngdorf and I'm using the onboard amplifier with a low pass filter of the Lyngdorf to drive the sub.

But how do I connect the speaker wire to the passive sub? Should I connect both left and right of both channels, or should I only connect one channel? I'm confused and I don't want to fry the driver...

Hope you guys can help🙂

Mads

Hi Everyone,
I am restoring a McCurdy tube based radio station phono preamplifier unit. It consists of a pair of AP 120 phono preamp modules, AM 410 mixer / monitor amp and a PS 850 power supply. It's light blue in colour. It is mounted in the console with the turntable on top.

Working on it is tedious, wiring and components are tight. Does anyone have any technical information on the circuits at all? There isn't anything out there except the AU 300 phono preamp. That gives some clues as to how they thought at least. These pictures may ring a bell with someone (I hope).

This gets restored keeping as much to original components to retain the sound character. The carbon composition (new) I'm getting are all out of tolerance, so I'm not happy about that one bit. Modern caps though. Sorry, it has to be reliable.

Thanks for any help at all.

-Chris

hi everyone
firstly i'm an electronics noob
i just purchased a box of fake fairchild bc337-25 from ebay(not for a project just to tinker with), and was wondering how i could test them, so as to compare to the specs of genuine 337's. the fairchild datasheet only gives characteristics information, and no suggested circuits to test.
so far i can continuously draw about 400mA through one of the fakes, but at about 500mA the smoke comes out.

so basically my question is what easy tests can i perform to best compare the fake against the real specs ?

warm regards
gaz

I have several Quad 405-2 amplifier which I’ve done the usual recap on. I always go with the usual TL071 OPAmp. I have always followed DaDa electronics way of fitting a 100uF polarized capacitor instead of bipolar on C2. They fit the positive leg of the capacitor to ground. I myself usually use low leakage Nichicon UKL capacitors for this position. I recently just thought about if it’s is a good idea to use a Polarized cap instead of the bipolar that was fitted there originally. So, this morning I measured a couple of my 405s and saw roughly 0.2mV on both the negative and positive leg to ground, which seems fine. But what does the collective knowledge here say, should I replace the polarized with bipolar caps instead? Pic borrowed from DaDas 405 revision manual.

HI
This is a question concerning the use and connexion a dac to a streamer and set up the hardware volume control.

My volumio is V3, My DAC SMSL M100 that is compliant with the hardware volume control.

When I connect the dac via the USB port I can set up in volumio the hardware volume control
When I connect the dac via Toslink, I cannot, only software volume control is proposed.

It that mean the hardware volume control only available if we connect the dac on usb ?
Did I miss something in the setting to allow the hardware volume control when connected via toslink ?

Help will be appreciated

Georges

Hey recently I've been wandering if I can save some cash on a crossover upgrade by using a mixture of Jantzen standard z , clarity cap CSA with a cdet 940c bypass cap to meld them together. I need to make up a value of 7.5uf so would use 3.6uf standard and a 3.9uf CSA with a 0.01uf cdet 940c. Has anyone on here tried these two caps together in the tweeter circuit. Thoughts would be appreciated. The other components I'm using are Jantzen superes on everything but the parallel woofer spot were Im using Jantzen mox. There also is a parallel cap in the woofer which is an electrolytic so I plan to use a cheaper jantzen cross cap. The 1uf cap will be a Jantzen standard.
Attached is a crossover schematic