I am building a very simple amp, or so I thought.

It only consists of 5AR4 -> LC -> LC -> KT88 single ended output stage (cathode biased)

The input stage is to be built on a separate chassis.

I turned on the amp without tubeI started with 630mA fuse, which blew. I increased the fuse size progressively till 1.25A, which still blew.

I checked for shorts from B+ to ground, or anywhere else to ground. None that I could find.

I got fed up and used a 10A fuse, then the power transformer smoked. Bad idea in retrospect. At the time I concluded that I had a bad power transformer.

So I replaced the power transformer. Powered it up, it worked, sort of. B+ is between 350-380V, I don’t remember exactly, transformer secondary is 420V, so seems good. One of the tube achieved 36.6V bias, seems good. The other tube wasn’t conducting, due to a loose connection.

I rectified the loose connection, and powered it up. I watched the tube bias rises to 50+V, which is very strange, and then the fuse blew.

I checked everywhere for short, but none that I could find.

I removed the tubes, fuse still blew.

Then I realised, the OPT is unloaded after I replaced the power transformer. I thought I might have fried the OPT.

I disconnected the OPT, fuse still blew.

I disconnected the second stage LC, fuse still blew.

I removed the rectifier tube, fuse did not blow. So I guess, at least the power transformer is fine.

So, there is something wrong between the 5AR4 and the first LC? The choke seems fine, no short to ground. The capacitor seems fine to me too, correct capacitance reading, no short to ground.

How else can I check if a choke is faulty?

Would faulty rectifier tube blow fuse? It lights up fine, and seems to pass current fine.

I don’t know what else to check for.

For sale tda1541 D3 Dac. Geniue tda1541 included. Dac was tested with ak4118 input board and battery power supply and it is working perfectly. As you see assembley is perfectly done. Upgrade Pps foil capacitors instead ceramics.
For sale
Symultanious input board + dac board+ Tda1541
GIFT: UFL cables
Price 150eur

Just when you think you know everything.....Does this solder rally make a difference in kit building?

Let's suppose you have a diode bridge in your amplifier's power supply. What are the symptoms that call for a snubber? I mean if you consider the amplifier a black box (you have no access to the internals), what signal degradation or unwanted signal do you see at its output?
In general, how do you tell whether a precisely selected series RC parallel to each diode is necessary or just a C of 10nF value is sufficient?

I bought these to try in a project and decided against them, so they are nearly new (a couple hours on them).

$75 plus shipping (US only).

I just received my order of 10 Jantzen air coils from Nonsolospeakers
Take a look on the picture, theses Jantzen coils seems definitely not in pure copper as they should be... but in aluminum wire...

I contacted Jantzen Audio which confirm: No, we do not manufacture aluminum wire or foil induction coils, as they are usually only for industrial applications, not audio.

We have not sold any coils directly to Nonsolospeakers, but that does not mean that they did not buy our coils via one of our official channels (distributors).

The answer of Nonsolospeakers is: the product is original the coil is covered with tin to avoid oxidation and to facilitate welding.
Our official channel (Jantzen distribution) is contacting Mr. Michael Dahl, you will receyved soon confirm from Jantzen
Regards

Where is the mistake ? 😡

I want to design and build a multi driver setup to control directivity, but not finding any software that fully allows me to do what I am wanting.

Design would be like a Kii 3 or Beolab 90, achieving directionality by using multiple drivers. Not going to make it adjustable, just one fixed setting, so certainly a lot simpler than a Beolab 90, but I do want directivity across a broader range than the Kii3 achieves.


The typical array software or calculators that I am finding are to constrained.


What software can design and model a multi driver directional setup?

Does someone have the specs or a digikey number for the blue screw terminal that is not in the parts kit for the B1 preamp but is recommended in the build guide?

I know where to buy parts buI don't know enough yet to distinguish this particular one -- that will work with the PCB board for the potentiometer -- from the the many options out there and need to buy it per the spec or the number.

Bonesthrower

Hi, I have a solid state Marshall 3315 head that I'm attempting to get back up and also use as a learning experience. One day years ago I turned it on and it just didn't work.

I replaced the 10amp pico fuses but they burnt right up. Should have known better. I then checked the diode bridge and saw that the negative and positive rails were shorted so I took it out of the circuit but it didn't help as the short was still on the pcb at the same point. I did notice if I disconnected either of the emitter leads of the power transistors MJ11015/MJ11016 that the resistance between the power supply rail goes to 10k.



what should I try next? I am mostly a tube guy so I lack any real experience in dealing with solid state power amps. any help is greatly appreciated.

Any body can point me to someone on here diyaudio site for proven plans, my budget with components and crossover is $700 except BB ply for a 3 way home stereo sounding pair of speakers for small PA use? I just finished a few months ago a pair of diy 3 way fully horn loaded and neo drivers from another well known site and sounds ok but it just sounds too PA if you know what I mean. I spent $1200 for the build total. I know I could've spent that on a JBL or QSC powered but I like to build and hope with great success. I have used this for 4 dj use and birthday parties not really what I am looking for and will probably just use it as a back up speakers for future gigs. Thanks🙂😕

Or designs that are DIY friendly? I just built some nifty bookshelf speakers but I am interested in some planer or ESL as a future project.

Hi all,

I was about to order a couple of Eminence Kappa 15C to put in my Peavey FH-1 bass horns. I do know that the Kappa 15C works really well in the FH-1 enclosure, having seen measurements and testimonials.

But I stumbled across an ad of a guy selling a few B&C 15NDL76 woofers, mint, a price slightly cheaper than brand new Kappa 15C; so now I'm hesitating.
Looking at the specs, the B&C seems perfect for a horn with a QTS of 0,22; it also has strong Neodymium magnet and cast frame vs ferrite and stamped steel.
It also has 7mm Xmax vs 2,5mm for the Kappa 15C.

I would be using it on the 70 to 400Hz range, in a tri-amped audiophile system, with low power class D amplifiers.

But I would like to model the response but I cannot do it; my computer is a Mac and Hornrespons can't be used on it.

If someone looking at the specs could tell me if it is a good choice, or possibly model it for me?... :-/ Klipsch Lascala / Belle model could work as well, as the horn is very similar. Currently using Klipsch K33E woofers but I would like more definition and output in the 150-400 range, which the Kappa 15C does.

Thanks in advance!

here are the specs:

B&C Speakers

Volume control module PGA2310 with Rotary Encoder - Audiophonics

Is this volume control IC any good compared to a classic stepped attenuator / passive volume control?

I have been rebuilding a Dynaco ST35 amp. I am thinking of doing a new power supply External larger transformer and DC heater circuit. Has anyone tried this?

The little amp before in its original state run very hot. I have seen some threads that say the one thing about this amp is the power supply was never sufficient and is taxed.

Scott.

Hi

I'm at the stage where I have my two speakers built. They are 3-way with two woofers for 4 drivers altogether (perhaps regretting that bit but I'm all in now).

I've been doing some measurements and trying to design a crossover. I have roughly the response I want, I've got impedance in check (I think) but I can't make head nor tail of what i should be looking for in the phase department.

Here's what I have, can someone tell me what's wrong or right about the phase graph?

NOW SOLD Mono 8-Ohm 50W Type AT-50H L-pad
2x for l and r channels

sold by Grieder Bauteile
see:
Speaker L-Pad Mono 8-Ohm 50W Type AT-50H or AT-52H, Grieder Elektronik Bauteile AG

Possibly made in Taiwan ! and not CH.

PAIR
Touch-turn is more than smooth; these are high quality, in
vgc (been used and tested briefly)

these are 29CAD$ + tx new (at SOLEN) -
pair for 22$ is v. reasonable

all Canada postage is 18$ by tracked box.
Prefer EMT Interac (Paypal add 4%)

Hi All.


I'd like to have on hand electrical cable of various colors for Loudspeaker internals. I'd like to minimize cost while catering for both 4.8mm & 2.8mm spades, for most circuit boards, as well as most power requirements I might encounter in domestic HiFi?
Is there a one size fits all AWG which I can use?


cheers Cliff

Hallo ich bin auf der Suche nach jemand der mir helfen kann ich habe vor kurzem einen sansui seven gekauft und jetzt auf einmal keinen FM Stereo mehr auch der Signal vu schlägt nicht mehr aus.
Die Mono Taste scheint ebenfalls nicht das zu tun was sie soll ich denke aber es hängt alles miteinander zusammen weil direkt nachdem ich ihn gekauft habe hat es funktioniert.
Ich bin für jede Hilfe dankbar eventuell auch jemand aus der Umgebung rendsburg mit dem ich das Gerät zusammen durchgehen kann weil ich würde auch gerne etwas lernen .

Freue mich über Nachrichten

viele Grüße Karin

Hi, I have some of these tubes, I would like to know what your opinions are on on this version also in general.... and with which polarization they perform best.
I would like to start using one in a follower cathode of a preamp.

Is a voltage of 270v, grid at -3 / 3.5 and current of 5 / 6mA suitable?

Or is it advisable to have a higher current and a grid .. type at -2?

Thanks 🙂

Hi all,

Has anyone tried to make a home brew Spex card for this amp to bypass the contour preset into the individual cards supplied with the unit? I’m using it successfully with a standalone passive sub, but obviously it would be better if it was simply a straight power amplifier without preset response curves. I’m thinking a bypass should not be too difficult?

Thanks
Mat

12" Radian Coaxes w/ 450sp $230 shipped USA

One pair of vintage Radian 5012 coaxial speaker drivers, including the woofers and high frequency compression drivers.
From the 1990s.
All 4 drivers are in good working condition.
The woofer foams are good and strong.
The cones are good, no tears or rips.
The woofers actually measure 13" across the frame, they're huge.
I had them mounted in some test enclosures and they sounded great.
The compression drivers are Radian 450sp 8 ohms (sp for spade, rather than pb for push button connectors).
Same compression drivers as are used in many other Radian coaxes including the 8", 10" and some 12" newer versions.
Please ask any questions before buying.
The picture with the 10" Eminence woofers is for size comparison only. The Eminence woofers are not included.
No crossovers or enclosures are included.

EDIT: PRICE DROP
$230 shipped within lower 48, paypal f&f or add 3%

No returns, no refunds, sold as is.
These drivers will be expertly packed!!
Shipping via UPS Ground with tracking and insurance.
Thank you for looking.

Hi, I'm building this line preamp to srpp + output buffer.



I have, for the heaters, a toroidal with two 6A 0-8V secondaries.
The tubes I use are 6n23p (instead of ecc88).
The B + is 180v.

For the SRPP stage I would like to use 4x 6n23p tubes, instead of two.
Of each valve I have two options.

First option:
Use only one triode and leave the other unused (if not used they advised me to put the grid on gnd).

Second option:
Put the two triodes of each tube in parallel ... just so as not to leave the second triode disconnected.

Which solution is the best?

The purpose of using 4 separate tubes is to be able to lift the heaters of the high triodes separately from the low ones and, at the same time, not to pass the "left and right" signal in the same tube (even if it has the screen).

With triodes in parallel I would have half the output impedance.
I don't care, I have a 15mA polarized CF for the output.

Thanks!

I built a 4-way tube crossover for a friend. He’s experiencing noise like frying eggs and bacon when playing SACDs at a similar level to the music. The noise is present during quiet passages too. A large collection of SACDs is unlistenable.

There’s no noise when playing standard CDs.

Below is a block diagram of the system.

When playing SACDs there’s no noise when:

• The tube crossover is replaced with an Accuphase digital crossover

• The SACD/CD player is connected directly to the tube crossover.

I’ve read that SACD/DSD produces “an enormous amount of ultrasonic noise (created by the noise-shaping technique used to achieve a respectable dynamic range in the audible part of the band) that can affect amplifiers and cause intermodulation problems in a largely unpredictable way”. I’m doing more research on that.

Is that what we’re hearing?

If the output of the SACD/CD player is causing audio band problems in the Absolare tube preamp:

• how does the Accuphase digital crossover then get rid of those artefacts in the audio band?

• why doesn’t it do the same to the tube crossover which has the same architecture (grounded cathode amplifier stage followed by cathode followers)?

The predecessor to the K1X SACD/CD player had the same problem, and as you’d expect, with DSD fed to its DACs, but the manufacturer installed a brick-wall filter that eliminated it. This time, the manufacturer either can’t or won’t provide such a fix.

Can anyone explain what the problem is and what we might do to fix it please?

I know the ECL86 (in triode mode) is a good sounding tube for making a simple SET mini amp with. Just curious if an ECL85 would do even better? Any experiences soundwise?

Finished a new FEA18RCZ build using the specs provided in the Seas Application Note exactly. Great sound except for the extremely bright top end. Not really listenable at higher volumes. Seas recommends to install an inductor/resistor circuit, and recommends using 1.2mH and 18 Ohms. I had a 15 Ohm, so I used it instead. Now the highs are severely attenuated, and not really listenable. Almost as if you removed the tweeter from a typical 2-way system. Do you think that using a 15 Ohm instead of the 18 Ohm made much of a difference? I wouldn't think so, and if anything it would have attenuated the higher frequencies less than an 18 Ohm resistor. Seas states that this design "offers the listener a loudspeaker system with a precise, coherent and engaging listening experience using this high quality driver." I attached a picture of the assembly I put together for testing. Thanks for the help!

Can somebody please explain to me if lossless digital volume control can be implemented on a Mac?

In practical terms all my sources are on my Mac Pro:
- YouTube and other online sites
- TV channels (I watch Freeview channels on my computer, no TV)
- iTunes (all my music is on an external hard disc)

My tube system is designed to have only the amplification I need, nothing more. So normal listening level is around 80% of maximum volume at a guess. If -6db means losing 1 bit, I'm probably not losing that much.

I'm interested in the idea of lossless digital volume controls, but I have no idea how to implement this on my computer since my mouse does all the volume control on whatever website or software I'm using.

Do you have any thoughts about changing factory binding posts?


In this case to pure copper or mostly copper, upper 90%.

Besides the new potential parts I chose looking way nicer, the original parts contain mostly brass in them. Maybe I opened a proverbial can of worms upgrading all of my stereo wire and spades to parts containing a high percentage of copper and silver. If there is an inferior link in my speaker connection chain it would be the factory posts.

Fortunately I'm not utilizing all 4 posts, the WTB or Cardas aren't exactly inexpensive.

Hi,

I have good basic electrical engineering knowledge but little experience. I now have a problem is out out my league, so if any of you can give me a a head-start I would be very grateful.

I got a NAD-amplifier from the dump, that I try to repair. Except from starting up, it did not "do" anything and the first fix seemed simple enough. BR101 looked bad, so I replaced it. That made the LED on the board work again, but the amp still did not work. Then I noticed how R167, R154 and R156 got smoking hot (I saw smoke) within a minute. I then switch off the amp.

So the left channel and the right channel have resistors that carry way too much current. Notice that the resistor R167 has a different function than R156 and R154.

Then some measurements: R154 and R156 had a voltage of 15V (and rapidly rising) R167 measured 90V

In simpler amplifier diagrams I can calculate the expected current running through stages. Here my lack of experience is showing. In this schematic I did not see how current sources set the circuit.

Then I registered on this forum hoping that posting my question here teaches me how to go about with this one.

The service manual is attached to this posting

Somewhat tube related, was wondering if anyone had a copy for the ART Tube MP schematic.
Tube MP – The Original – ART Pro Audio

Thanks in advance.

Up for sale are new never used pcb boards to build a no compromise class AB power amp.
Power 400+ W @ 4ohms

Boards:
1x Amp control board ver. 6
1x NS modular input supply board ( for the drivers stage psu)
2x NS modular supply board ( PSU boards)
2x NS modular X4 input board (a driver stage)
2x NS OPS double power board (output power amp boards, they are huge!!!)
2x Thermal sensor boards (for monitoring temperature)
1x Protection board (Speakers protection board)

The boards are the newest revision! I can provide all the manuals I got. Or more info here: Virtual Zero Audio Store





Price: Feel free to make me an offer...
Shipping worldwide.

SOLD!!!

Up for sale is a nice balanced gain stage board using the 12AU7 tubes. The original circuit is from Andrea on his page:
Hi-End DAC tube output stage
As you see on the pictures there are no pcb sockets installed as I used chassis mounting but I guess this is no problem to solder
a 9-pin ceramic or better belton pcb socket on the board.
The CCS for the tubes is 2sk170BL this way it sounds uncolored! The original CCS had a glare like sound and this is not my cup of tea. But If you want it
back to original schematic then I guess its only two Jfets and 4x resistors to change.
On the board are very good parts, also the 2.2uF russian MKP new production very good sounding.

For sale are also mains transformer EI core and a special wide band 20H choke.
If you want the populated board only the price is 150 EUR (icluded a nice pair of GE 12AU7 tubes)
Mains transformer (P: 230V S:230V @ 300mA + 15V @ 4A) and 20H 170mA choke= 100 EUR

I am shipping worldwide!

Hello girls and boys...
Need an advice or "how to"...
I have a pair of P Audio BM-8CXA drivers.
Would like to remove the back of the tweeter for mounting into an open baffle project i am working on currently.
Can someone tell me what to expect under the cap of the backside of the tweeter?

I know i have 4 screws to remove but what is holding the tweeter coil with the dome there and how to secure it when i remove the backside of the tweeter part of the driver....

Would love to know what i have to be careful on before going into this ..
thank you

Hi,

I’m quite new on analogue electronics. I found this schematic for a audio line mixer, but I can’t understand something... maybe someone could help me:

1) Why audio signal pass on drain level on t1-t2-t3 but on source level on t4?
2) Why is not present another capacitor to filter dc - ac on output line after t4?
3) why r1 is after t4 and the resistor on the source of t4 has a different value respect the other resistors?


Thank you for your help... I’m try to learning but eletroninc is not so easy...

Someone said why our forum have no any FPGA-based DAC. So It’s here now. I hope someone will interested in and discuss
This DAC will be compatible with Raspberry Pi and any I2S signal.

About DAC:
+ Auto detect sampling rate upto 768khz and bitdepth upto 32bit
+ Asynchronous I2S FIFO with 2 clocks for 2 sampling rate families (x44.1 and x48)
+ Upsampling or Resampling
+ FPGA-based Delta-sigma DAC with digital filter and noise shapping.
Board Detail:
+ Intel/Altera Cyclone IV FPGA
+ 2 clocks with precision power supply (ADM7150)
+ Power supply 5V or all individual voltage for Diyer upgrade (1.2V, 2.5V, 3.3V)

I have a two way set of speakers that need 5db attenuation to balance the speakers.
8ohms
50w
Tweeter = 95db
Woofer = 90db
According to the online line calculator I have been using here L-Pad (Driver Attenuation Circuit) Designer / Calculator
Then I get R1=3.5 ohms @ 21.88watts
R2 =10.28 ohms @ 10.28 watts.
5w & 10w resistors are available from a limited source, but the question here is what would be the best way to approach the contruction for this Lpad.
Do we really need more than a 10watt resistor or can we use a combination.Bear with me here as I'm still a noob when it comes to design and build for crossovers.

Amp cam in with blown outputs and the output filter inductor broken off the board .

Fixed the inductor and replaced all outputs with matching date codes .

Amp will power up and idle fine .

Problem is the amp has very distorted output .

Any ideas on where to start ?

Hello. Many years ago i was given this subwoofer, the speaker box without the servo amplifier. I purchased a couple of used Velodyne servos online but the system did not work. Later on a learned that the servo had to be calibrated to the specific driver and that there was a built in accelerometer on the driver to do the feedback required to reduce distortion. I still have the box, i would love to make it work. Amplifier technology has improved, before spending money and time, i would like to ask if the sub is worthy of it. I could buy a decent sub for a bit more than $1k but I rather no put this thing in the trash can if possible. The driver box and foam surround are in good condition. I was thinking of a hypex based plate amp with built in servo circuit. What do you think? Advice appreciated.

I see that the MCHStreamer and USB Streamer support 10 channels in via USB and 8 channels out via I2S plus another 2 via existing SPDIF - for a total of 10

I'd like to somehow take the 8 I2S channel outputs, convert them to SPDIF and send them along to 4 Khadas ToneBoards ... to support active speakers (DSP functions applied in the source PC) with mostly 44k & 48k signals ie. CD and Video standard audio

In theory its easy. ToneBoards accept I2S input (in theory) and I2S can be converted to SPDIF
BUT

How to do this,

• sending over distance > 25cm (my understanding is that signal I2S integrity suffers over these distances)
• sharing one clock from I2S so all DACs are synchronised
• sending "correct" voltages etc
• I'd prefer to avoid debuging I2S - I2S unless both ends are known to be compatible across all proposed use cases

Is there an add-on board that will plug-n-play. Does anyone have schematics or advice on how to do this (or how not to do it)?

I'm aware that the UDIO-8 and nanoDigi offer this kind of functionality but both are limited to 8 channels out and the nanoDigi only offers 2 channels in

grateful for any advice 😀

Hi everyone. I need help in measuring my Mezzo Utopias with new focal drivers to adjust the crossover.
I decided to biamp them. So I bought a Crown 1502 to use for the bass and I will use my Aethetix Atas for the mid-tweeter sections.
The current status is that I have new Woofers, the ones used in their latest Utopia Scala speakers, and replacement midrange drivers from the Mezzo era but the ones used in the Grand Utopia then, and I have had my tweeter replaced by focal, with a titanium I think, since they had no spares for my tweeters.
This is the state of the drivers. I also purchased both Parts Express DATS and Omnimic V2 measuring systes, so that I can take proper measurements and be more sure about what I am doing. So the expert measuring system is at hand, I just need the brains(which I do not claim to possess...).
As I am using a Metric Halo Lio-8 3D as both pre-amp and DAC, and since it has the capability to act as anything soundwise really, including a crossover, I was thinking of using it for this task.
Initially I was thinking of connecting the drivers on the cabinet but without any crossover and to test them in place (including the effect of the box), using the DATS and the Omnimic, to have all the right parameters. I could change the parameters of one speaker using three of the four channels availiable in my amplifiers, until I get the right curve, so that I can know the best cutoff points between the three drivers. I will then keep the crossover for the bass and the output for it and make a crossover for the mid and tweeter without the need to cut the low for the mid, since I will be cutting it using a the Lio-8. In this way I can build a crossover with minimum components and exact to my speakers.
Since I have no experience in this, I would very much appreciate it if you can give me some guidance as to what to do. If you can help I can send you the characteristics and you could perhaps help me with the design of the crossover.
Initially I read various articles on measuring the speaker response and I have a couple of questions:
1. Do I take near field measurements of all, the bass(and port), the mid and the tweeter, to reduce the effect of room interaction, or do I use the transient response curve for the mid/tweeter to identify room interaction and separate the useful part of the frequency response of each driver and add it up to get the real response of it?
2. In near field measurements, do I measure in the same distance from the center of the drivers for all drivers(so I am limited by the woofer distance which is the largest), or each one within 0.11 times its' diameter which will remove outside interference?
3. If I take measurements at ear level and 1m from the speaker, should I activate one at a time or all together and measure the resulting curve?
Should I also take measurements around this area, moving the mic higher/lower to the right/left?
I am not sure about all this. I have Xsim to input the data of the measurements for the drivers, and I can perhaps then design a crossover. I can perhaps use the crossover that in them as a guide.
If there is another simpler way that I can follow, please tell me. I do feel a bit lost....

We are constantly told how bad our SE tube amplifier are when it comes to Damping Factor, some people don't realise or choose to ignore the fact that the actual speakers DC resistance tends to be dominant in most cases.

Hi, I have noticed in many schemes the presence of a diode between the grid and the cathode.
I would like to have, if possible, all the information about it, if it is useful and when, if there is a degradation of sound ... etc ..
I also notice that there are those who implement it with a resistor ..
What is resistance needed?
What value should it be put on?

Thanks! I attach some pictures ...

Hi Guys,

After some advice please? Hope this is ok to post here but please move if this is in the wrong place. I've recently built the 8600SVK but have an intermittent issue with the right channel.

Powered up and there was a crackle/pop on the right channel and then silence.🙁 Followed the troubleshooting guide, swapped the 300b and the right channel started working again so assumed it was a faulty tube.🙂

• Received a replacement 300b, installed, and worked a dream listening to music all day.🙂
  
• Following morning powered up and a crackle/pop and the right channel is out again.🙁
  
• Took voltage reading's to diagnose where the issue may be and tested again with music on the off chance and both channels working again!🙂
  
• Following morning tried again and the same crackle/pop on the right and it's out of action again.🙁

Before I tear it all apart and review all the soldering is there anywhere I should be focussing on first?

Readings below: TP3 & TP4 seem to be whack so i'm not sure if this help's diagnose where the issue may be.

Any comments/thoughts gratefully received.

TP1 0.8 0.84
TP2 0.8 0.82
TP3 110 98
TP4 110 103
TP5 0 0
TP6 0 0
TP7 8.7 8.7
TP8 8.7 8.7
TP9 175 167
TP10 175 168
TP11 235 223
TP12 235 226
TP13 330 335
TP14 330 339
TP15 -70 -72
TP16 -70 -72
TP17 -70 -72
TP18 -70 -72
TP19 360 364
TP20 360 366
TP21 5 5
TP22 5 5
TP23 365 370
TP24 365 371
TP25 2.7 2.7
TP26 2.7 2.7
TP27 16-22 15.4
TP28 16-22 15
TP29 385 390
TP30 385 390
TP31 -98 -98
TP32 160 159
TP33 12.6 12.6
TP34 60 59.5
TP35 6.5 6
TP36 6.5 6
TP37 12.6 12.2
TP38 300 296

Hey there,

I'm stuck with a Beyerdynamic A1 clone kit I'm building: 2015 Latest Headphone Amplifier kit reference to Beyer dynamic A amp | eBay

The board is fully populated, and I've applied power:

+/-16vac has been applied to the board from a 30VA centre tapped transformer.

Both LEDs near the driver transistors come on, but the relay does not engage and the front LED does not come on.

If I apply signal and turn up the potentiometer, the heatsinks start getting a bit warm, but no where near hot.

I've attached photos.

If anyone could help me with troubleshooting steps that would be appreciated!

Thanks,
Chris

Never used, can’t even recall what they cost. I think they are about 9.3k output impedance.

How about $60 plus shipping for the pair?

Discount if bought with the toroidal power transformer separately listed.

My offer are ultra low distortion amplifier DiY kits at a non-profit price until further notice, sold through Ebay, payed with Paypal.
Condition for resorting to the non-profit price: send me photos of the completed amp that I can post on my homepage within 6 months of purchase.

All kind of distortions are surely much lower than what can be sensed by human hearing (e.g. 1kHz THD<0.001%). 6 prototypes were built and all function perfectly. ABX blind tests and nulltest prove no "sound of its own", neutral and transparent. Can be used as reference amplifier or loudspeaker measurement amplifier, too.

LDA MIN: 2x80 Watts stereo with turn-on thump muting via a mechanical relay (the mechanical relay may somewhat degrade distortion), no protections. 75 EUR + shipping.
LDA DM1: 2x120 Watts dual mono with full protections via ultra low distortion solid state relays. 140 EUR + shipping.
LDA DM2: 2x200 Watts dual mono with full protections via ultra low distortion solid state relays. 178 EUR + shipping.
LDA MON: 1x200 Watts mono with full protections via an ultra low distortion solid state relay. 90 EUR + shipping.

Outside of Europe shipping costs may be prohibitive. The above non-profit prices include packaging fee, Ebay commission, and Paypal commission. Currently on Ebay in the UK, Germany, France, Spain, Italy. If you're interested and the kit is not listed on the Ebay of your country, please write me a private message. If there is no Ebay in your country or you don't have Paypal, then you can't buy safely from me.

All components are from reliable source. Critical components are from renowned manufacturers.

More information: DiY loudspeaker and amplifier design
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Please check what is included in the kits and what is not.

Hello,

I would like to build my first pp; a 6as7 circuit to suit the tubes and opts I already have (opts are from vintage Philips el84 parallel PP recording studio amps, 4k to 8ohms). I have been looking around for schematics and found a few candidates but each poses a problem to my limited technical know-how:

http://www.diyparadiso.com/sk6as7pp1.htm

--> looks promising; my plan would be to leave out the PS and desing one using PSUDII to suit my old stock power trafo; is the part of the circuit on the top right meant to delay B+ for the 6as7's? Additional problem would be to achieve the high 550V B- (my trafo is about 375V@ 200mA, I never designed a PS with B+ and B- rails) + the circuit is not so simple for a beginner like me

http://www.triodeguy.com/6as7_pp.htm

--> Biggest downside is the class A operation (to suit the toroids I guess); I would prefer the 10watts output of class A/B. However, amending this circuit with simple class a/b output stage cathode bias would, if the preceding stages can drive it, seem like an easy 'beginners'-circuit. I'ld also design a different PS with the additional filtering these amendments would necessitate

http://www.dissident-audio.com/PP_6AS7/Schema.gif

--> I can't identify the phase-splitter used, looks weird to me + the output stage and PS have a few elements I don't understand (the connection starting from the power trafo's centre tap)..


I would be very happy if some of the members with more technical luggage could comment on these circuits or do some propositions; for now the second schematic with new output stage and PS looks like the best option...

Thanks a lot!!

Simon 😀

Hi All
I'm looking for reliable and competent Accuphase P-300 (Kensonic) repairs on east coast, Recommendations north of NYC are ok but not further south of Baltimore, MD.

Anyone have experience with repair shops? please keep discussions limited to experiences of actual Accuphase repairs done please.

Thanks
Rob

Went to Madisound and sb acoustic to check mw19p paper driver spec. Even at the same impedance driver both site are listing different specification. Did satori made some update on their satori paper drivers ? The fs showed in an accoustic site are rated lower.

This has probably already been discussed many times but the forum search engine refuses to search for sag :-(


I'm working on an experimental guitar amp for a friend, and I plan to do this in stages, i.e. first build a pre-amp and then start work on the power stage. As a result I will need a power supply for the pre-amp before I even know what the final B+ will be for the whole, so for a while at least I will be working with a power supply which is only designed to drive the pre. And that leads me indirectly to some speculations ...



One of the things I plan to play in this amp with is controlled power sag, and this leads me to ask: when sag occurs, does this primarily affect the power amp or is there also also a sonic effect on the earlier stages? My guess is that all stages are affected, so for example a pre-amp stage might go into clipping earlier when the plate voltage falls. Is this so, and is the result more likely to be "interesting", or just crappy?

I am working on a passive crossover of a 3-way. There is an active crossover in my preamp, dividing the bass and higher frequencies.
Then, there is a passive crossover between my mid and tweeter. This is the crossover I am working on.

What I have noticed is that, while trying different alterations of my crossover, the performance of the bass varies considerably.

I know that the bass unit (which has seen no changes) can play very very well, with deep and very dynamic accurate bass. However, with some iterations my xo the bass becomes thick and slow. I have looked, but cannot find anything that might explain what I hear. I looked at phase integration between the hf-drivers and the bass. I have looked at timing differences (time domain). But what I hear seems uncorrelated with anything I can analyze.

I am sure that experienced designers must be familiar with this, and I hope that in general terms I could get some pointers to look at.

What am I missing?

Should the electrolytics (esp. the big filter caps) in a 20 year old low bias class AB amp be OK? By low bias I mean runs pretty cool, not a lot of heat in the chassis interior to accelerate aging. I found an amp I've always wanted but it is 20 years old and not cheap ...

I bought a pair of Chinese KT88 SE circuit boards with the intention of using one per channel for a pair of KT120s and one 6SL7 per board as the voltage amplifier. (Gain of about 30-40 required and will be fixed biased)



The pcbs are quite decent and the KT88 sockets are on snap off pcb sections.


However I am struggling to decide the input stage topology.



According to the Tubecad app it seems to be a cross between a self biased totem pole and a current sourced plate follower.



The totem pole gives higher gain, better psrr and lower output impedance but needs a grid resistor on V1b and R2 would need to be reduced to the same value (~ 4.7k) and both cathode resistors being the same.


Any comments or suggestions?

Hello there

I'm in need of some advice to sort out a speaker problem.

I have a pair of old B&W P4 floorstanders and just recently I noticed that only the tweeter was firing on one of the pair, the mid driver was silent.

So, I pulled out the mid driver and tried it on the other speaker - works ok so the driver itself appears to be fine. Next I tried the driver from the good speaker on the bad one, no sound. So at this point I'm assuming the crossover is the root cause.

I pulled out the crossover - at least as far as I could and notice there are 2 caps on there and not much else.


So, I'm assuming that one or both of these caps needs replacing but I'm totally new to this kind of thing so I've no idea how to properly identity these caps or source replacements. Alternatively, I could keep an eye on ebay for a entire crossover - though I assume the failure is age related and so any of these units will be liable to fail at any point given the age of them (25 years-ish).

Any help / guidance would be very much appreciated.

Thanks!

Never used, but was hooked up and powered on briefly so wires twisted.

See photo for outputs.

Can’t recall what it cost new.

$125 plus shipping

Discount if purchased with the OPTs separately listed.

To the best of my knowledge standard LLC smps is typically protected against OC by either: Split-capacitor and clamp-diodes to rails or voltage-measurment of the capacitor-voltage.

The Split-capacitor-diode-idea is simple but limits the voltage over the caps and for some designs that may be a problem?

The voltage-over-capacitor-reading is proven and tested, but requires a high-voltage-capacitor to work?

So late last night i got en idea: if the LLC is implemented with a seperate series-inductor we can directly measure the current in this by adding a single (isolated) winding and putting a suitable resistor across the single winding. Voltage over the resistor is then a true reading of the current in the LLC-loop.
The voltage could easily be scaled and fed to the CUR-limit input of controllers like L6599.

Is this an old idea? - i could not find anything on google, but that is probably because I dont know the correct words to search for.

I have a working LLC on the workbench and Im tempted to test the idea, but let me hear your thoughts.

Kind regards TroelsM

Sold

Saved this gem from the garbage collectors.
Looks like it was re-coned at some point. Have not tested DCR yet.
Came out of a Brociner corner horn. Hope to use as a mono
or better yet find it’s twin some day. Not bloody likely! The owner’s
eighty year old eyes lit up as he recalled buying the speaker and building a Heathkit Tube
amp to go with it. He then told be that all could bettered by a
a pair of Bose speakers. I smiled in apparent agreement and thought to
myself how rough it is to get old.

The markings are faded but I can make out:
6A0
R7L

They are clearly diodes. I cannot find the types using the limited markings.
Anyone id these?
Thnx

Hello,
I am looking for some help with diagnosing my new Elekit TU-8500. I just finished building the kit. I went through the operation check and everything works except there is a hiss/static sound coming from my speakers. It is loud enough that I can hear it sitting 9 feet from my speakers.


Some Info and might help:

- Both channels are affected.
- The hiss is present whether or not I have a source hooked up to any of the inputs.
- Hiss stays constant no matter what the volume control is at.
- Changed power cords.
- I moved the pre-amp to a different location to see if I was getting interference.
- I swapped in another pre-amp and it was silent.

Any ideas would be appreciated.

Thanks,
Mike

Hi,

Looking for a pair of Accuton C79-6 midrange drivers in good condition.

Thanks,

Steve.

If it matters to anyone.

IRFP044NPBF Infineon / IR | Mouser

Sony 360 audio speaker. Includes loudness correction and automated sound calibration via internal microphone.

Sony's 360 Reality Audio is competing against the other spatial audio formats.

SRS-RA5000 premium Wireless Speaker with ambient room-filling sound | Sony US

LJM Tripath TA2022

Hello,
I build ljm ta2022 amp kit, v. 1.2.
Very nice sound but.... I noticed
that inductors heat up a lot ! 😱
Is this normal ??
I'm pretty worried about the speakers,
especially for the tweeters, for now I have put aside
the ta2022.

Hi All,

I'm playing with a faulty NAD C300. One of the MOSFETs died and had blown the 5 amp fuses. I've replaced the MOSFET but before powering up the amp fully, I'm checking the unit for other issues. Looking at the supply voltages on the power supply board (with the amp board disconnected) I'm not getting the rectified voltages I expect - but I'm struggling with a common ground reference. Fwiw I believe the transformer is good. It's windings seem to be correct when each winding is measured to its corresponding CT and pair - for both volts and resistance. This poses me two questions I'd appreciate advice on.

First Question: The circuit diagram in the service manual shows the centre tap of both the secondaries being connected on the power supply board and forming ground - but they're not connected until the amplifier board. I assume it's ok to connect them on the power supply board while testing so I have an easily accessible ground reference since they are connected but by a different part of the circuit? Trying to hold a multimeter probe onto a header pin is asking for trouble...

Second Question: Another deviation from the service manual is that Ground is directly connected to Chassis on the amp board. The service manual shows different types of separation between Ground and Chassis depending on where the connection occurs in the circuit but no direct connection. Is there a reason why the chassis (which has no connection to Mains Earth / Protective Earth) would have been directly connected to circuit ground? Is there any reason I shouldn't reinstate the separation shown in the service manual?

I have attached images showing the power board layout and relevent circuit diagram. All replies gratefully received.

Ive read that carspeakers are designed for infinite baffle. Do anyone know of 4-5,25 in coaxial autospeakers suited for mounting in a box for hifi use in a 2,1 system. Has to be current models

I ask cause carspeakers are often dirt cheap and I need the protection cover for my application.
They need to play down to 100 hz zero db down or close.
Volume has to be reasonable for musiclitening in sometimes larger rooms
Any suggestions? Cheers!

Hi
I have a couple of old MF Dr Thomas power amps, both of which are still working well and I'm keen to give them a thorough refresh to keep them reliable, hopefully improving the sound quality as well! In original form, they sound fairly relaxed with good solid bass and a rather effortless power delivery. Surprising poke for their rated 120w RMS.
Has anyone experience of these amps? They seem to be very simple in their design and construction - which appeals a lot.
Initial plan is to fit new, larger smoothing caps, a better bridge rectifier, replace all the caps on the circuit board with higher grade items and replace all the rather flimsy internal wiring with decent stuff. What about diodes and transistors? Any likely improvements to be made there?
Any recommendations as to what make of components and any other mods that can be carried out would be gratefully received.
Would anyone be interested in seeing photos of the refurbishment?
Thanks in advance!

Hi there!

After moving to a new house I decided to build a new set of speakers. My wife had been complaining on the previously somewhat bulky speakers and I was therefore planning on something that didn't need to take up so much floor space and could be placed into the corners of the room. My thought was going in the direction of a full range line array so I started to look for inspiration. Soon I found wesayso's gigantic thread on this forum, and this has been a main inspiration for this project.

My plan is to build a big bookshelf, covering most of the wall and integrate the speakers on the sides. The room width is about 2.8 meters and the listening area will be about 3 meters from the wall. As of now, the room looks like this:



Ceiling height is about 2.5 meters, so there is room for 28 TC9FD18 drivers on each side. 4 sections in series with 7 drivers each in parallell should do. Minimum driver impedance is 7.75 ohms, so the resulting impedance would be 4.4 ohms.

As can be seen in the photo, there is a big window on the left. The first reflection point from the right speaker will be right on this window. No chance of stuffing the window with absorption...so I got this idea of trying to absorb the sound close to the speaker instead. By doing so I want to narrow the horizontal dispersion and avoid any early reflections in the listening spot:



It would look something like this:



The plan so far is to build four separate cabinets for each side, containing 7 drivers each, and stack them. 2.5 liters internal volume per driver and 16 mm thick MDF for cabinet walls. Drivers front mounted and then (a better looking) second baffle made of oak attached on top of that. One section would look like this:



This is the plan for now, but I'm sure some things will change in the process. 😉 70 drivers (some for future ideas, like ambience speakers etc.) ordered and are on the way!

Hello,

This might be a pretty basic question to some, but I'm unable to find an usefull answer to it.

When a driver manufacturer publish it's driver's frequency response diagram, in what environment and how exactly are those results acquired? Do they mount the driver on some kind of infinite baffle? (Outside wall of the room perhaps?)

Reason for asking is... when I mount that driver to an open baffle, or if I just hang it with no baffle at all, what kind of a readout can I expect? (Provided that the measurement are taken outside with no reflection points, except for the ground perhaps)
I've seen some videos where a downward slope to lower frequency is displayed, with a peak in the middle of the spectrum. Would that happen even to the driver that's measured dead flat on specs?

Thanks for your help,

Stefan

Just an FYI for anyone from Europe (and maybe US?) ordering from Mouser at present... they have looooong processing times at present due to both snow in Texas and all the other crap thats happening in the world. They couldn't even give an estimate of how far behind they were earlier today.

Not thrashing Mouser, they have usually excellent service IMHO (although I'm not a very frequent user), but its best to know there are delays right now before waiting and waiting on something for a project. Its been 8 days now and my order is still in processing.

Hey guys I’m looking at this punch 800a2 board here the problem is there 54.14vdc at both channels. I was in the works of repairing one channel as you can tell by the picture. I installed some fets to test everything and so far it play clear and clean. Then both channels ended up dc voltage. Neither outputs appear to be shorted from left to right pins. All check out good. Any leads to what to check greatly appreciated! Thanks

Friends

If I connect the G3 of the 6AS6 to cathode , this pentode can work fine for audio pre-amplification ?

Thanks, 😀

Aldovan

Any has an eTracer to part with? Looking for one. I suppose the license is transferable with kit. Thanks.

Dear all
Looking for a man-cave HiFi system, in how to address for the frequency range 2.5...10 kHz. Above that I plan to use a rear-firing horn tweeter with high-pass.
But above a 4...5" midrange, I am looking to a 1" compression driver with a 60...90x40° horn. Something like: FaitalPro HF100 with B&C ME45 or P.Audio PH-3520

I am attracted by HF horns for their low distortion and high spl, but how do they sound indoor at low spl levels?
Does it make sense to use them for 75-85 dB listening habits in a 7x4.5x2.3 m room? (23x14x8 ft in US money)

Thanks!

Problem:

I have a James sub woofer amp that blew two Output FETs. This amp Has two IR2011 chips driving two FETs. One High (+60v) and one Low (-60V). One pair drives the speaker negative and the other pair drives the speaker positive. One of the pairs blew. I changed all the FETs. The amplifier worked but the output filter inductors got very hot after running for five minutes while the heat sinks remained cool. While probing the input OpAmp the FETs blew again. It seems only the low side FETs were working as the Bootstrap caps show no voltage. The problem should be something common to both amps but I am at a loss.


Here's where I'm at:

I think the problem is that the IR2011 high side won’t start even though the high input is present. There is no voltage across the Bootstrap caps. This seems to be due to an incorrect startup sequence to charge these caps. I downloaded a reference design from International Rectifier that is an amplifier that is almost exactly the same (See attached). I metered out everything in the Vcc circuitry and found nothing wrong. I changed some caps, pre-drivers and the IR2011's to no avail. If there is no 13V across the Bootstrap Caps the High out signal won’t work. There’s something wrong with the Bootstrap Circuit which I don’t understand. Please help!

Gary

Effects of police defunding

Bought a used 7250PE on ebay with the typical “powers on, but not tested” disclaimer.

On initial power up noticed hiss from right channel and similar lower volume hiss on left. This was present at zero volume. All the input sources worked. Turned up some music and the hiss faded into background. In quiet passages though, you could definitely hear the right channel hiss across the room. First step was deoxit on the main controls. No love.

I pulled the preamp jumpers on the back and still had hiss, so that narrowed it to power amplifier. I went on a long search for a bad transistor or resistor using freeze spray, heat from a soldering tip, tapping the PCB with the eraser end of a pencil, plus DVM checks of components in-circuit. I don’t have an oscilloscope. Anyway, as I went along eliminating certain parts of the circuit (I do have the service manual), I kept doing internet searches. Eventually I found an old post here where someone identified two trim pots out of spec in a 7250PE with bigger problems than mine. Sure enough, they were way out of spec on mine too, and that ended up being the problem.

I found three references on-line to these same trim pots, all failing in the same manner. I am #4 on the list, and I suspect every 7250PE out there has this problem. The pots in question are R618 and R668, both 200 ohm trimmers used for the “minimum distortion adjustment” described in the service manual. Others have reported the resistance of their failed trimmers as high as 1.5M ohm. Mine were 200K on the left and 500K on the right. Out of circuit both my trimmers had tight rivets. When I measured resistance from the rivet to the resistive surface only 1 mm away it was sky high. So I suspect there is galvanic corrosion between the resistive surface and the rivet. In the power amp, NAD uses three trimmers per channel. The two affected ones are physically smaller than the other four (used for idle and centering) and have 5 mm spacing between legs. Idle and centering cannot be adjusted properly with this distortion trimmer resistance so high. My understanding is high resistance in this trimmer causes the switching transistor to utilize the high voltage rail at all times.

I replaced these trimmers with new 200 ohm units. I had pictures of the old ones, and just set the new ones to the same clock position as the bad ones. Others on-line simply substituted 100 ohm ¼ watt resistors. This is a non-critical adjustment that technically requires a distortion meter to adjust perfectly.

All the larger type trimmers showed resistance within spec.

With new trimmers I was able to easily set idle and centering. Hiss noise was gone. I had the slightest hum (sounded like 60 Hz) in both channels, and decided to be anal and start checking the electrolytics. Starting with the power supply I marked the PCB for my check points with power off. With power on I did not get very far, as I quickly realized the hum was positional, and went away when the amp was on its side. The circuits are obviously very sensitive to ambient fields. With the case back on— no hum!

I did measure some DC voltages while I was at it, and will post those here, as they are not listed on the schematic. These were measured with the impedance switch set to 8 ohms. I did not measure AC voltage since I had already figured out the hum was positional.

C865, C866 +76.7 VDC and -76.7 VDC (80V caps)
C862, C863 +46.2 and – 46.2 (50V caps)
C851, C852 +35 and -35 (35V caps)

This amp is from about 1986. I also have an NAD 7125 (ca. 1983) and that only uses the larger size trimmers. My suspicion is that any NAD product from this era that uses these same small trimmers will have problems. Possibly, these smaller ones are only used in the 7250PE.

Since this receiver is now working fine to my ears, I decided to live with it for a while before considering anything like a recap. I have been all over this thing looking for bulging caps or signs of leakage several times. And, yes, I am aware that the operating voltages on those filter caps are very close to (or at) the limits of their ratings.

Hello, I just completed my TU-8600S with TKS volume and Lundahl transformers.

I have 2 problems,

1, at startup there are loud static pops unrelated to where the volume is set, this diminishes as the amp warms up.

2, the audio volume is very low and sound quality is poor.

I have disassembled the amp and carefully rechecked solder joints and have checked and recorded voltage check points. Please see below.

This is my 3rd Elekit project and the first time I have had any issues, I also noticed that while the tubes are glowing they are not very warm compared to my other amp and preamp.

Any assistance would be greatly appreciated.

TP1 .32V
TP2 .31V
TP3 25.0V
TP4 27.9V
TP5 0V
TP6 0V
TP7 3.27V
TP8 3.16V
TP9 55V
TP10 61.5V
TP11 70V
TP12 74.3V
TP13 103.7V
TP14 28.7V
TP15 -97.4V
TP16 -97.8V
TP17 -98.3V
TP18 -98V
TP19 107.4V
TP20 111V
TP21 5.14V
TP22 5.1V
TP23 107.5V
TP24 111V
TP25 0V
TP26 0V
TP27 304.7V
TP28 301.1V
TP29 414V
TP30 414V
TP31 -101.3V
TP32 165V
TP33 12.6V
TP34 61.5VAC
TP35 6.62VAC
TP36 6.62VAC
TP37 12.9VAC
TP38 305VAC

After few repairs, I keep at home, I listen one or two weeks ... and the sound shot down after 15 seconds, I hear the relay opens. If I turn off and turn it on, the relay closes and I hear music for 15 seconds, and so on. It is the same if I start in A or in B mode. I try with headphones without speakers, it is the same.

I found this Yamaha CA1000 in the garbage with a turntable.

In the beginning, when I found it, the amp was not working. The A/B switch was cleaned, the two outside microswitches changed, the back card was cleaned and resoldered. The amp was badly repaired in the past, with transistor installed in the wrong way, bad soldering everywhere on new low-cost components, wrong power transistor replaced, few ceramic resistance was changed.

This thread was merged with a second of the same title and content.

hi all

I want to add a single/mono subwoofer to the two satellite speakers I just built.
Ideally, all three speakers would be powered by the same amplifier, via a passive crossover, split at ~ 100 hz.

I understand the theory and application behind a "regular" 2 way, stereo crossover, eg two tweeters and two mid bass/subwoofer drivers, but can't visualize what I'm after.

Any help or pointers would be much appreciated.

Thank you

JP

How do you "size" an amp? I want everyone to hear it, without making anyone's ears bleed.


Situation could be anything from a 12' x 50' conference room with 10' ceiling to a 100' by 100' showroom with a 30' ceiling.



Surely there's a 'formula' for this sort of thing?