A Big Name in the world of recording equipment has passed:

Rupert Neve, GRAMMY-Winning Audio Industry Icon, Dies at 94

Pls I will need to know much about this amplifier. It's a mono 130w amplifier, and I will like if I can use two of it for stereo setup.

Looking for something to put on the kitchen table to protect it while working. Not metal or wood. Some sort of plastic something I guess? Or a large rubber cutting mat? I have no idea - any suggestions?

Good afternoon!

So I got one of these IR-receiver (something like this, but I'm not sure of the exact part). Connected the whole thing and it's working. 🙂

Now comes my challenge: How do I integrate it into my 10mm Al frontplate (black anodized)?

I'd prefer to have it barely visible. (well, a 4mm hole is totally ok, in fact, already done)
Can I:
Use one of those plexiglass-tubes? (Would be nice, allowing me to mount the receiver onto a breakout-board and channel the tube onto the receiver)
Place the receiver on the faceplate's back and have the infrared funnel through a 4mm (9mm deep) hole? (this would probably diminish the wave angle to a narrow window?)

a big hole would be a very last resort.

Side note: Could a much smaller entry-point (2mm) have worked?

Thank you very much, and have a good afternoon!

Hi legends,

New to the blog. Its nice to have people reunited by the same cause.

I just bought a used Yamaha A420 amplifier (1985). Problem is the balance knob is descalibrated, but that did not mean a problem to me until I discover that when I turn the volume knob, the balance in the speakers gets ****** up. Lets say I increase the volume instantly the right speaker starts to sound louder than the left, if I lower the volume same effect other way round. This means everytime I touch the volume I need to balance the speakers...

Does anybody know how to fix this? I have searched in the internet and unfortunately did not find any useful advice, only that it could be dry joints on the volume pot. Talked with a technical by phone and he told me chepear fix would be 90 euros, which is a lot for me now. Any DIY solution would be very very appreciated!

Best regards.

Hi everyone.
I need some help to investigate my subwoofer amplifier.
It is an Class D XTZ plate amplifier.
I observe a normal situation but No sound or output from amplifier.
When sound is on from preamp i can see led change from red to green (Auto on). When measuring VCC+ andVCC-, i have 0v DC. Normally when amp is on, i belive it should be approx 50V DC on this terminal? Is this high voltage normally on when amp is on or is it turned on by the preamp (Auto on function?). I do not have any scematic.

I'm planning on putting together a board i bought a long time ago from the Orient, via eBay. It's a JLHC, but I don't have too much more info than that. I also have 8 "Arctic 12 Passive" heatsinks that I thought I could use with this. (They are "rated" at 47W each!?) I can't find out too much information about this particular board and wonder if anyone here has built one of these 4 OP transistor amps. I think it was rated at 15w when I bought it.



I had planned to separate the transistors onto their own heatsinks, as they seem a bit close to each other on the board. Is this wise? I wonder if that's why the vendor recommended a 15-0-15 200VA supply (I presume per side?). Could the output increase with a larger supply and sufficient space and sinking? Is there any existing guide for setting such an amp up?



Is a regulated supply the way to go with this board? I've seen a JLH update page with a diagram for a regulated supply, but wonder if it's sufficient for this board with it's increased output devices. I presume I'd have to get an 18-0-18 supply to get a 15-0-15 regulated output? (That's what the rear heatsinks could be for.)

Or would it be a better idea to go for a different design to fit my proposed case hardware (because I have it lying about)? I'm thinking for a mirrored dual mono design that I can sit next to each other, with the fins out the sides. I'd like to squeeze as much power out of these heatsinks as I can!

I welcome any suggestions, knowledge, encouragement, intrigue, or slight criticism.

P.S. At the bottom of one of the images is another set of thin boards. I have no idea what they are are, aside from being cloned Class A amp boards, using a 7 leg 2SJ109, a ZTX450 and ZTX550, with 4 IRFP240 output drivers. Any info on these mystery boards would be publicly thanked.

Greetings people

As title suggests, I am currently scheming to repurpose my Yamaha RX-V1700, and would very much appreciate some feedback before I move forward, in case I have missed something. The plan was for pure multichannel amp use for DIY 4-way active speakers. I will use external DAC to multichannel input to 6 of the amp-channels and 2 preouts (center and SW) for volume controlled pass-through. AVR will not be used for other duties after this.

So as known AVR's have some internal stuff going on in regards to LFE/SW. My plan is to change components in SW preamp channel to mimmic the other descrete inputs. This will consist of removing the SW mix with main L and R, removing/bypassing LP filter and changing components to get the same gain structure in preamp circuit as rest of the channels.

Here are some shots from the diagram where I've found need work:
Multichannel input

LP filter

Pre volume control

Post volume control

Pre-out SW and Center


If anyone has some thoughts or advice if my plan seems ok, or if I have missed something feedback is most welcome

For sale a pair of completed mofo boards with verry good parts, takman resistors, mundorf supreme, mundorf silver oil..... With pair ouput capacitors Nichicon 15000/50v super trough and with 2x hammond 193v chokes. If you want to build the verry good sounding mofo amp you need heatsinks and psu.
So:
2x mofo boards
2x nichicon output caps
2x hammond 193v
Price 300eu or best offer.
More info on contact.
This boards were build in my mofo amp on steroids.

Wondering are these amps like the old hifonics series 7 where the caps start leaking over time

The guy brought it to me and asked me to go through it and said to check the caps out .

Wondering if they should be replaced or if they still test fine leave them

OD MLTL @ (pi/9) x total qw pipe seems to be the bees knees For offset ?

Hi everyone. I've put up a new tube preamplifier design at www.redrookits.com

It's a tube phono preamplifier that matches the RedRoo SE5 power amplifier. Tubes are used exclusively in the signal path and all reports are that it sounds very good indeed.

Hope you enjoy. Phil W.

Gone !!!!!!!!

Thanks for looking

Hey.
I've been building tube guitar amps for a while, so when one of my students asked me if I could fix his solid state bass amp, I said I could try.
The amp is a line 6 lowdown 300pro. (I'm attaching the schematic).

The amp stays silent when I connect and try to play a bass.
If I connect an mp3 player to the mp3 input mini jack, I can get sound through the headphones, but still nothing from the regular inputs.

I seemed to get the right voltages from the psu board.
I looked over the preamp board (page 1 in the schematicl), and found a smd resistor that was fried (R82). I couldn't tell why it had fried.
I replaced it with a regular resistor of same value (5k1).
I also looked over the electrolytic caps, but couldn't find any that looked like they'd died.

I fired the amp up again, while starting to check various voltages, but after a little while, I felt something getting quite warm: the U2 voltage regulator providing 3,3V for the preamp logic and codec circuits (page 5 in the schematic).
It seem to output 3,3V just fine, so I presume the regulator itself is working alright?
But I'm a little uncertain about how best to pinpoint where the problem now is. The heatsink on the regulator gets too hot to touch after a while, so I presume something is pulling way too much current through.
Am I right?
Any help?

Regards
Anders

My main system is comprised of DML panels that can cover everything above ~150Hz or so. However they require heavy EQing to achieve a relatively flat response and are pretty inefficient. I am not super bothered.... the system is in my kitchen so the noise floor is often super high anyway (the dishwasher is currently running) but I was wondering what I'm missing from a more "pure" speaker. I have a "pure" build in the works to compare with this but I was just curious. I know nothing is free but to my ears they sound OK.

Is anybody running this combo ?
I just upgraded to '10' and my
DATS comes up but is dysfunctional

Hello guys .
Sorry but I want to know is it possible to make an audio amplifier from old laptop charger ?

Yet another homemade mic the element is a real mic element.
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Do capacitors go bad merely from age, or do they go bad from repeated charge and discharge?

I was wondering whether "new old stock" capacitors are actually okay to use, or whether a 30 year old capacitor is 'dried out' or whatever goes south with them. I have a junk shop nearby with many NOS caps that have never been soldered into anything.

Appreciate any insight on how they degrade. Happy holidays.

Analog Devices ADALM2000 Advanced Active Learning Module
https://www.analog.com/en/design-ce...oftware/evaluation-boards-kits/ADALM2000.html

New and unused. The downloadable software didn't work with my old Mac.
$99.00 postpaid within the USA.

Diaphragms are in great condition. A little surface rust that looks worse in the picture than in person. To be expected on bare iron from 1978. DCR 4.2/4.3.

$100 shipped USPS priority, US only

hi.

please be patient because its my 1st pcb design. i try at my best but please comment on the following pcb if there is any error. or need some correction please mention that. want make sure it correct before i send it to print pcbs. Thanks.

So here the deal! Im building a 4-way Floorstander and ive ran into an issue with impedance. My issue is, im working with 4-8 ohm speakers and if i run them all in parallel i will end up somewhere around 1-2 ohms (just a guestimation). Wont this be bad for my amplifier? As a solution, i would just wire the two LF drivers in series and wire the two HF drivers in series, but then how do i design the crossover so that each speaker plays a specific frequency range? I only understand how to wire crossovers for each speaker when they are done in parallel.

I note one customer review on Bottle Head forum of someone who "upgraded" from ACA monoblock to MonAmour 2A3 monoblock but not too much of a Leap to Audio Note Kit power amp. What's people's build experience of Bottle Head or ANK product?

Here is a design I worked up that avoids those expen$ive audiophool VTs. The prices for the DHT triodes (45, 300B, 2A3, and to a lesser extent the 845, 6A3, and even the 811A) are stratosphereic for new production, and let's not even discuss NOS. The prices for the audio pentodes has also been creeping up there lately. So, what to do about that? How about avoiding trendy types and circuit topologies?

So I designed this amp that makes use of the 6BQ6GTB horizontal deflection pentode as PP finals. As with any other HD pentode, the 6BQ6GTB has a characteristic that allows for some very high Ip's at lowish Vpk's. This means that it can't be used single-ended, since the most linear part of the characteristic is well within red plate territory. However, a Class AB1 loadline can reach this part of the characteristic without any spec-busting. With an Rl of 1K1, the resulting loadline looks pretty good, with an acceptable h3 of 5.0%, which can be improved by loacl NFB.

Though rated like a 6V6 (Pd= 12W for both) the 6BQ6GTB can supply more than twice the output power (37W as opposed to 18W for the 6V6). Another differenceis that the 6BQ6GTB isn't so amenable to either trioding or Ultralinear since the screen voltage rating is so low (Vsgsg= 150Vdc). That, however, may not be such a disadvantage since both of the latter are "trendy", and this might keep the expense of the 6BQ6 down and the availability up.

Loadline

The first preamp/phase splitter is a cascoded LTP with active tail loading, and based on the 6BQ7A small signal, VHF triode. This particular type was designed with cascoding in mind. As an audio triode, the linearity isn't bad, though it's doubtful you'd want to use it as a straight audio voltage amp. There are more linear triodes for that. However, since this is a differential, the balance cancels the even harmonics to improve the overall THD. Cascoding also gives enough gain margin to allow for gNFB without requiring an additional gain stage.

The LTP splitter drives a 6FQ7 dual triode with each section being used as a cathode follower to drive the final grids to charge up the Ci + Cmiller + Cstray, and to allow for DC coupling to avoid the blocking problem that occurs with capacitor coupling to fixed bias finals. This is critical since gNFB will exaggerate an already bad clipping behaviour if capacitor coupling is used. This also makes for an easy bias adjustment to reduce any DC magnetization of the OPT core.

A further aid to sonic improvement is an active screen voltage regulator. Stable screen voltage and a Lo-Z screen source helps to improve the sonics of any pentode final. The screen regulator is based on the 6KE8 (another TV t00b) which combines a high gain pentode (error amp) with a medium gain triode, both connected in an unbalanced differential stage. Reference voltage comes from a 0A3/VR75 gas discharge regulator tube. The series pass element is a trioded 6AQ5. This regulator holds the screen voltage rock steady regardless of the volume.

Main Schemo

Since this has just been completed, I ran it with no NFB connected whatsoever. This sounds quite good already. I couldn't hear any of that pentode harshness at all. The most obvious sonic defect was sloppy bass which becomes most noticeable when playing bass-heavy techno. I'd say that the 6BQ6GTB is a more heavy duty 6V6. It really does sound surprisingly good! 😎

The cascoded differential also isn't contributing any noticeable distortion either. It looks like the main design objective has been definitely met: a good performing open loop implementation that can be further improved by adding NFB to correct what few sonic defects there are. (Unforch, I'm still waiting on Mouser for some parts I need to complete this right. I had to power up the heaters with AC, and the active tail load with batteries. Once those parts arrive, I can take care of that, and run more tests.)

Pretty good for tubes that don't cost more than $3.00 a pop. 🙂

Any suggestion. I can’t adjust the offset setting in the left channel of the rec. differential amplifier. In SM should be up to `+/-10mV, but in fact the voltage in TP1 fluctuates after fine tuning in a couple of minutes from 5mV to 60mV? Was checked transistors TR,25,26 replaced TR24 and electrolytes C6,7.

Hello

has anyone experience with this module?
https://de.aliexpress.com/item/1005...c3a,tpp_buckets:668#2846#8110#315&pdp_ext_f={"sku_id"%3A"12000028765269808"%2C"sceneId"%3A"30050"%7D&pdp_npi=2%40dis%21EUR%2130.93%2124.44%21%21%21%21%21%40210312ef16694822342023233e18e8%2112000028765269808%21rec

I bought it 2 weeks ago and nearly forgot about it, yesterday as i wrote in Ian Canadas thread about the UcConditioner it came to my mind and surprise, it arrived today 😀
for 30€ it made a REALLY nice improvement i really didnt expect for the price (i power the raspberry pi with it with a usb dac connected and compared it with a ifi ipowerX connected straight to the raspbberry pi or connected it to the supercapacitor module and then to the raspberry pi) i think the best way to describe it is it sounds more fluent now, smoother, more natural now, after hearing it now i think supercaps is the way to go, specially for this price

now i have a few questions
1. can the capacitors be upgraded to even better ones?
2. has someome else experience with this module, specially compared to the big caps of the Ian Canada UcConditioner?

there are also pictures of the inside on aliexpress
what you guys think?

Setup: (in case it matters)

Amps: 2 x GFA 555 II
Preamp: GFP 565 preamp in Bypass
Source: It depends, a computer: Gigabyte Aorus Pro AX with AMP-UP Audio, an Adcom GCD 575 or a lightly-modded Pioneer PL 512 turntable.
Speakers: Polk Audio Monitor 12 series-2 (8 Ohm speakers, still running fine)

One of the amps blew a main fuse a couple of months ago, so I just removed it and powered the setup with one of these in stereo. Sounds OK, but I'm wanting the other amp back in service. I have the time, so I pulled the cover to see if anything looked amiss (bulging caps, melting etc)....and it looks just like the other one that's running fine.

I'm looking for advice, since I'm learning as I go. I have experience in home wiring and automotive wiring. I'm generally capable with a multimeter. This is not the same, but I have time, patience and ability to learn.

I got a complete schematic and parts list,, and I'm admittedly not the best with schematics, but what I see points to output transistors and/or bridge rectifier(s). I'm prepared to pull each and test. But! Before I pull them, is there anything I should know? From my experience with old cars, I know that some things are well known in the community but not so much to "newbies". Just wanting to not make more trouble for myself.

Thanks!!

Mark

I learned electronics by designing and building audio amplifiers in the 1970s. That was great fun for the teenaged me.

The last amplifier I designed and built was in the year 2000. It is audibly perfect. While I have continued to refine the design, I have not built the newer one since it would sound identical.

So... my questions for the hobbyists are:

• After achieving audible perfection, do you continue to build more amplifiers?
• Why?
• What do you do with the old ones?

Ed

I just got my subwoofer and plate amplifier in the mail today. I didn't realize the plate amplifier would have terminals on the end, and the subwoofer just needs speaker wire. Can I just solder the speaker wire onto the terminals, or should I snip the wires, and solder them directly?

The amplifier board is Dayton Audio SPA300-D 300W
Subwoofer is Dayton Audio UM10-22 10"

Hello,

I have some basic questions about hardware for active crossover.

Is the Rpi3+ with its 1 Go RAM powerfull enough for active filtering for a 3 ways with Camilla ?

Is it possible to do that crossover job into the Camilla inside Moode ?

Which multichannel dac or system do you use after your Rpi (volume control question also in mind) ?

Thanks

Pickup in NE Ohio Only make offer for the lot! Must go now 🙂


QTY, HORN, THROAT SIZE, Price Each

2, EV HR 9040 "white whale" 90 degree, 1.3 1.4 1.5, $50.00
2, EV HR 6040 "white whale" 60 degree, 1.3 1.4 1.5, $50.00
2, COMMUNITY BIG 60X40 RADIAL 300HZ, 1.3 1.4 1.5, $50.00
2, COMMUNITY BIG 90X40 RADIAL 300HZ, 1, $50.00
2, COMMUNITY BIG 90X40 RADIAL 300HZ, 2, $50.00
2, EV 60X40 STEEL RADIAL 500HZ, 2, $50.00
2, PEAVEY 90X40 RADIAL 800HZ, 1, $25.00
2, JBL 2350 RADIAL, 2, $50.00
2, JBL 2355 RADIAL, 2, $50.00
2, JBL 2328 THROAT ADAPTOR FOR RADIAL , 2, $75.00
3, JBL 2386 BIRADIAL, 2, $25.00
2, SELENIUM MH3950, 2, $50.00
2, EMILAR EH820, 2, $50.00
2, EMILAR EH1210, 2, $50.00
2, EMILAR EH153 VERY LARGE Front horns , 3.3" , I USE 8-10” DRIVER GOES TO 80HZ, $150.00
2, EV LARGE 100HZ FIBERGLASS FRONT HORNS, 12, 15” DRIVERS, FREE
2, FAITAL PRO STH100 80X70 TRACTRIX, 1, $50.00
2, FAITAL PRO LTH102 60X50 TRACTRIX, 1, $60.00
2, FAITAL PRO LTH142 60X50 TRACTRIX, 1.4, $60.00
1, Cerwin Vega theater sub “earthquake” HORN , 18, FREE
2, SELENIUM HL1450, 2, $50.00
2, GAUSS 4140 RADIAL, 2 NEED REPAIR, FREE

My QSC K10 speaker fan completely stopped working but it's able to play only the fan what can be the causer of this problem

I have two of these transformers, 2x115v primary, 2x 25v secondarys 225va clairtronic branded. These have been used please see pics for details

£30 for both or each plus postage at cost. UK only.

Improperly designed power amp units where output power transistors with 30-60MHz are in use as mentioned in post #1 under
https://www.diyaudio.com/community/...amilies-for-audio-power-output-stages.147656/
may degenerate into an RF oscillator - unfortunately often only temporarily (removing or moving of only a single cinch-wire or mains power cord or move the amp device of any few cm lets abruptly break off the unwanted oscillation).
Main reason therefore is a bad layout choice of the conductor tracks - consequence is, that several parasitic capacities are additional present.

Most audio engineers still believe that with regard to human hearing from 20Hz to 20KHz, the design of audio power amplifiers is completely uncritical (compared to power amplifiers for RF/HF applications) and checking the frequency response of audio power amplifiers up to 100 MHz is complete nonsense from the view of those engineers.
I don't think so.

I claim, an examination of those frequency area below and a bit above ft of power output transistors is definitely necessary - i. e. between 0,5 MHz and 100MHz, if ft from power Transistor is 60MHz.
Which is well very far away of 20 KHz.
Only then can one clearly see whether there is a tendency to oscillate or not. If there is a tendency to oscillate, the plot looks basically like those from the attached image (red curve) - but the peak is mostly between 1MHz and 10MHz.

If there is full level RF oscillation or if there is an undesired oscillator function immediately (recognizable by the immediate destroy of the output power transistors due occur of max quiescent current value that be supplied by the power supply), this can only be proven with a power supply with integrated current limiting unit (one suspects at first glance faulty pot in the vbe multiplier stage - go to post 14 under
https://www.diyaudio.com/community/threads/differences-between-various-vbe-multipliers.117047/)

With any few amplifier models that I had on my desk because oscillation issues, I was able to find out the reason with help of the CAD program CIRCUITMAKER. These were the amp models I remember well:

1) Meracus Onesta Integrated Amplifier
http://ftbw.de/xp/amplifier-xp/meracus-onesta-v1.html
The device oscillated sporadically to around 3 MHz with nearly full voltage swing (without speakers and 1K load) also depending on the routing of external connecting like cinch cables) - accompanied by rapid heating of the output transistors BD911/912 (three pairs in parallel mode).
My repair was supposed to be the fourth attempt - this amplifier device had actually been abandoned from the owner.
In the simulation of this circuit topology the frequency response looked smooth up to around 400KHz and dropped off at around 6db/oct. without anomalies up to 100 MHz

Parasitic capacities due to conductor tracks running in parallel were initially not taken into account while first circuit design from the this German manufacturer. As is well known, a capacitance between the output and the inverting input (in parallel with the NFB resistor) is critical, which was not planned or taken into account while circuit design.
Due to the parallel PCB routing on both component and solder sides, a capacitance of about 70pF was created (noted by measuring after de-solder several resistors and caps around the NFB loop).

After introducing this capacitor into the circuit in the simulation (CAD-program), the oscillation was also present here - slightly deviating in frequency and level in opposite to those from real live (according my own oscillographic measurement).

The frequency response measurement looked basically like the last diagram on the third to last page under
https://hifiakademie.de/pdf/phono.pdf?si=google
however, the peak before the drop was around 2.5-3MHz.
I increased the capacitance in the circuit under simulation to 220pF, which made the peak even more pronounced, and then changed the values of all present compensation capacitors so that a flawless "roll-off" between 1MHz and 100MHz was occur (effortful work and many sessions on my personal computer).
After introduction of new capacitors in the "ONESTA" itself with the values from the simulation and the 150pF capacitor parallel to the NFB resistor (= 220pF ./. 70pF), flawless operating without any RF artefacts resp. ring-ring effects was also recorded in real live, which is still the case until now (about 15-18 years ago).

2) Luxman L190
integrated bass-treble control in the NFB loop of power amp section (and passive preamp consisting of source resp. input selector and volume control) - go to
https://elektrotanya.com/luxman_l-190a.pdf/download.html
Perfect function in the middle position of treble control pot - degenerates into an oscillator when the treble control is turned down, the occurred oscillation level being so low that the output stage transistors are not destroyed.
Frequency of ring-ring around 100-200KHz.
Power amp not unity gain stable (same phenomenon as on op amps, not unity gain stable without external compensation). Regardless of whether speakers are connected or not.
The problem was not eliminated because in the currently application the trebles of the loudspeakers used were usually turned up further (full range driver in use without dome tweeter).

3) Philips F4215
https://www.hifiengine.com/man…brary/philips/f4215.shtml
Same observations as on Luxman's L190, but maximum level and destruction of both STK chips.
Correct working amplifier channels without RF oscillation designed with the help of the mentioned CAD program - after doing this no longer RF oscillation even in min-position of treble control pot. Unfortunately I don't have the details anymore. As I remember right, main effort was the creating of a unity gain stable power amp unit.

4) Horch 3.0S
https://www.diyaudio.com/commu...er-output-devices.379808/
Depending on the location, the fuse sometimes but not always blows - even without speakers connected.
Most likely unwanted high level RF oscillation as well. Still has to be tested with a laboratory power supply and current limitation.

In general, it has always bothered me that there are no measurements for home audio amplifier models up to at least 100 MHz and I cannot make any myself to prove whether the peak before the final frequency response drop is missing or not - the latter would always indicate that the phase reserve is too low - see basic description under
https://bilder.buecher.de/zusa…20871/20871854_lese_1.pdf
A low pass filtered square wave form at the amplifier output as seen under
https://www.amplifier.cd/Verstaerker/verstaerker/images/rechteck_10kHz.jpg
and numerous under
http://saba-forum.dl2jas.com/index.php/Thread/8271-square-wave-behavior-of-hi-fi-amplifiers/
is no guarantee that no oscillation or undesired ringing can occur - but a smooth roll-off (i.e. without a preceding peak in the upper range befor falling) in a frequency response measurement up to 100MHz is a clear evidence of this.

To carry out this measurement one need an RF-capable broadband noise generator and the possibility of such a frequency response measurement display. Furthermore, all filter capacitors must be removed outside of the NFB loop - mainly the input capacitor for limiting the slew rate and limiting the upper cut-off frequency - otherwise I get not helpful results and looks like those under
https://www.amplifier.cd/Verst…ages/gain_db_normiert.gif

Does anyone have experience with this kind of measurement on audio amplifiers ?
Which measurement could alternatively (to the frequency response up to 100MHz) to be made to estimate the risk of unwanted RF ring-ring ?

Many thanks for hints.

P.S.: this threads don't provide the appropriate information:
https://www.diyaudio.com/community/threads/amplifier-oscillations.3767/
https://www.diyaudio.com/community/threads/audible-or-noticeable-symptoms-of-oscillation.73724/
https://www.diyaudio.com/community/...il-override-problem-with-my-power-amp.323960/
https://www.diyaudio.com/community/threads/parasitic-oscillations-in-general.137972/
https://www.diyaudio.com/community/threads/rf-suppression-in-power-chip-amps.191989/
https://www.diyaudio.com/community/threads/relaxation-oscillations-in-an-amplifier.361203/
https://www.diyaudio.com/community/threads/amplifier-oscillation-problem.207554/
https://www.diyaudio.com/community/threads/check-for-oscillating-amplifier.162545/
https://www.diyaudio.com/community/threads/oscillation-in-ecl86-amp.338885/
https://www.diyaudio.com/community/threads/amplifier-oscillation.50697/
https://www.diyaudio.com/community/threads/amplifier-oscillation-problem.207554/
https://www.diyaudio.com/community/threads/amp-oscillation.97569/
https://www.diyaudio.com/community/threads/parasitic-oscillation.351771/
https://www.diyaudio.com/community/threads/op-amp-oscillation-advice.358610/
https://www.diyaudio.com/community/threads/neutralizing-an-amplifier.224046/

Maybe under
https://www.diyaudio.com/community/threads/bob-cordells-power-amplifier-book.171159/
or in one of the books under
https://www.diyaudio.com/community/...amplifier-books-overview-google-books.153311/
are some hints concerning the create of frequency response plot of audio amplifiers up to the RF area.

I'm in need of a test CD manufactured by Sony called YEDS-18. It is possible to get hold of it through official channels but this piece of plastic costs around €220,-

I thought it may be a possiblity to use a copy... If someone is willing to help, many thanks. Btw, I have a Paypal account... 😉

Anyone got a spare LM4780 they'd be happy to sell? Just found a PA03 board in a drawer and thought I'd build it, but I can't find the chip.

Hi,

I'm new to the forum.

Please find see the attached schematic of my effort to reproduce the Cordell Super Gainclone using the LM4780 as opposed to the LM3886.

I have simulated the circuit in Proteus with some success and plan to see if it works in reality. Probably due to my lack of knowledge, the current mute circuit works in reverse, open circuit gives amplification. The output initially went rail to rail with SW1 circuit closed. Installing output caps C22 and C23 seems to have fixed that but I'm still unsure as to why.

I know it is probably futile to try to simulate the circuit as reality is always very different. I did this because it helps me to prevent catastrophic failure and wasted time.

I am not an electronics expert, and realise there are probably many errors in the circuit, therefore, I was hoping for any criticisms prior to embarking on silk-screening a pcb. I believe I need to separate the signal grounds from the power grounds.

Any input is more than welcomed.

I just sold my fy6600. I rarely used it due to ground problems. Many contributors mods this model (power supply, final amp) to compensate "light" engineering.

Are actuals products mature ?

Selling 12 pairs Sony V-FET 2sj28/2sk82

12 pairs: 1100 euro + PayPal fees + shipping

1 pair: 100 euro + PayPal fees + shipping

Contact:. fscerbo@libero.it

Hello
I have 6 pieces of 6l6gc tube and 1 Hammond 1650T OPT, and I am looking for a simple wiring diagram for a PP monoblock,
I have found some schematics at Turner-audio.au but they are a bit too advanced. Anyone have any good suggestions
Regards Peo

Hi all,
My home electrical installation does not have grounding, its bi-phase 220V (127V + 127V). What kind of grounding should my tube amp have?

I recently had Mark do me a small run of boards and I can offer some here for sale.
3 pairs available.
£8 per pair plus shipping.

I want to replace opamps in my DAC that use JRC5532DD right now with LM4562NA. These come with 10MHz and 55MHz speeds. Does it matter witch one to use?

​

Hi All.


I am moved here for the LLC and questions tips. Reason is I am busy with low power, high voltage LLC.

Problems are feedback, resonance amd Lm Q what is best.

Output is 2 x 120 volts 250 mA 1 x 180 volts 250mA (use a voltage doubler here) and 6.3 and 12,6 volts 10 amps.

I do use feedback on the 12,6 volt, but when draw more current the high voltage go quite high, when draw lower it get less high, se need to do something about that.

I have some transformers and hev order also edt 39 and have edt 49 already received.

So now fun, and carefull because of voltages.

Pics here are some sims, the feedback do work, but it is quite dependent of frequency swing, I do not use a pfc,

Hi all which do think would be better an Audiolab 8000c pre or Rotel rc 850

Greetings,

New member, first post and just found out about this lovely community with tons of knowledge.
Long story short, 5 years ago I bought 2x Parasound HCA 2003 and used them for a short period of time until they went back to storage.
Fast forward to today, I will be finishing my Home Theater setup in my basement and will bring back my Parasound from storage.

I always wanted to service them, replace the caps and whatever needs to be done to give them another 20 years of life.
I see that there is an mod upgrade for the HCA 3500 being shared by bigskyaudio which by the way I was always wanted to send my units to them for servicing and always told my self that will do that eventually. I should have done that sooner since Big Sky retired and closed the shop 🙁

My question is:

1. Is there an upgrade mod available for the HCA 2003?
2. Any recommendation on what to do with them? what to change, remove, replace? I will be sending them to a technician in this coming fall.
3. Is the upgrade done on the HCA 3500 similar to HCA 2003?

I love my amps, first high end purchase I did and would love to give them more life.
Any help would be appreciated.


Regards
Manyakus

Hoping someone might be able to help out.
Inherited one of these units with a blown output... the unit has been previously repaired and looks like someone has swapped the original (?) STK4154 to the higher rated STK4164 ..
Wondering if anyone is aware how swap-able these units are with any other STK chips and if anyone can point me in the direction of a source of STK units?

Would like to get the amp back up and running rather than abandoning it to it's own devices in 'the shed'
All help appreciated

Brett

Hello, what about the second configuration (covering the internal bracing holes with sheets of polyfill)?

In theory I'm going to form two aperiodic halved volume chambers (one approaching "sealed", and the other "reflex") separated by a sort of light Variovent (flow resistance but not too much damped, just few centimeters of not compressed polyfill)

Here I found few references with similar idea

I think I'm going to lower the Q of the cabinet and increasing the virtual Vb. Is this correct?
How to model the behaviour?

The Power transformer

my Example is

the Primary is 220 volts (Philippines Base) but you can Deduce it by Dividing by 2.
the Secondary is 12-0-12volts or 0-12volts

we are going to compute specifies 12 volts output with 750ma current (my Example) converting milliamperes to ampere will give us. .75a , multiplying voltage by current gives us wattage or power.

12x.75 = 9 watts


after having solved for the wattage of the transformer, which is 9 watts, look at Tables 1, where 9 watts is listed, follow the table horizontally and pick up the date for the center leg, thickness and turns per volt.


Center leg - 3/4
thickness - 3/4
turns per volt - 10

see at Table 1 and Table 2

the nest step is to compute for the number of turns for the the primary and secondary coils respectively. the number of turns per volts in the primary is equal to the number of turns per volts in the secondary.


Primary coil - 220 volt (PHILIPPINES Base)
Secondary coil - 12 volts
Number of turns (primary) = 220x10 = 2200 turns
Number of turns (secondary) = 12x10 = 120 turns

having computed for the number of turns in the primary and secondary coils. determine the sizes of wire for these coils in the next step . before computing for the guage or size of wire (AWG) must find out the current capacities of wires and their corresponding sizes. this data is provided in table 2 .

the power formula is used again in solving for the currents of wires in the primary and secondary. dividing the watts over voltage gives us the current of the wire:


note:

I = Current, W = Wattage, E = Voltage


I = w/e


I secondary = 9watts/12volts = .75 a
I primary = 9watts/220volts = .04a


after having solved for the currents of wires pick up the corresponding sizes of wires from table 2. choose the closest current listed in the table.


Size of wires (Primary) - #35
Size of wires (Secondary) - #23


in case of a multi-voltage secondary, the higher voltage should be taken for computation. if the transformer has multiple secondary coils, the wattage of each coil is computed and then summed up. in other words, the wattage of the primary is equal to the total wattage of all secondary coils.

if the secondary coil is only center-taped, half of the wattage and current is taken to compute for the wattage of that coil.

the primary is 220-0 volts, the secondary is 12-0-12 volts

Could someone in France or in a neighboring country help me out with two pairs of FRH/FCH20A15 (4 in all, two of each) ?
thanks in advance

Selling some stock I haven't got around to using, at a fraction of their original cost.

Magnequest's EXO-173 phase splitter transformers are very highly regarded. These have the brass channels. There are a host of projects / applications on the internet for them.

$249 for the pair, delivered.

Login to view embedded media This guy bought a farm grade gas/petrol and sawed it in half, then built semi-functional models of the working bits, to show how these nozzles "know" to shut-off when liquid touches their nose. (After 11:30 is an interesting ad but nothing more about nozzles.)

Login to view embedded media Same idea, done not so well (he knows too much), by the guy who makes most of the nozzles in the US.

I also see why we can latch-on with the little lever (here we used to carry a wood wedge) and the nozzle can still shut-off.

Study it before liquid hydrocarbon fuel goes away!

Hi DIYers,

Can anyone recommend a good, not overly expensive ESD mat? I’d like one that’s heat resistant for soldering and about 20” x 20” or wider.

I’m mostly going to be working with discrete transistors op amps.

Thank!

Can you check these like the Ir21844’s ?

I know the pin configuration isn’t the same but wondering if you can check them like that?

The amp I’m working on is a Rockford prime 750-1D

It had full rail voltage across the speaker terminals all outputs test fine but it looks like some has either replaced the outputs or pulled them to check them and soldered them back in

What if we create a local feedback around one of output tubes similar to a paraphase splitter? I have no illusion that I'm the first but I couldn't find any mentions of this circuit. Does it have any major flaws except it will work in class A only?

Can someone identify these speakers? They are pioneer for sure.
There are so many models that look like this from outside but internally different. Please help!

Hello,

I saw i had a 6as7g NOS in my collection and it's honestly just beautiful, might be my favourite looking tube. Definitely at least my favourite looking double triode. So I wanted to use it for a headphone amplifier. Then I saw I had a 6c8g which is the same base so I thought why not put these together? One is a medium mu double triode and one is a low plate resistance double triode, should add up to one headphone amp, right? 😁

Looked around and found this on the Web and was thinking I'd adapt it for an autotransformer volume adjuster and obviously redoing the input stage along with larger value caps to get a better low frequency response. Also want to do a different PSU.

https://www.gammaelectronics.xyz/ax_06-08_tube-headphone-amp.html


Not sure if there are any other glaring flaws in the design i am missing. The input signal to the 6c8g should be around 0.5V(but obv has no drive or I would need an amp 🙂 ) at max volume and the load will be my 50 ohm headphones.

I'm thinking 300V B+ for the 6c8g and 150V for the 6as7g so I can use OA2s(I'd use OD3s for the looks but I've only got two octal sockets and I have a lot of BG7 sockets and equally huge piles of both tubes 🙂 ).

Not sure if I want to do tube rectification or solid state, I'll have to look through my tubes but I don't think I have any that would really be up for the task. I remember having four 6x4 tubes but I think they would be a bit weak for this, right?

Anyway that's what I've got for now, suggestions welcome as I've probably overlooked a few things!

Help me what can really be the problem for the fan not working on my QSC K10 speaker but it's able to play sound only the fan

Just finished recapping my onkyo m504 amplifier.
I noticed that there are provisions on the main amplifier board for additional output transistors. c
Currently the m504 uses 4 output transistors per channel sanken 2sc3856 and 2sa1492
I would like to add an extra pair of outputs transistors making it a total of 6 outputs per channel.
I looked at the prints for the bigger m508 and both amps use the same amplifier board.
The idling current t is even set the same. I know I have to stuff the board with the extra resistors base resistor, and .47ohm collector and emitter resistors.
So here is my question where to get the sanken outputs and how close do they have to match the ones that are currently in there.
There are sanken transistors on ebay but I'm not sure if they are real.
Anyone have any suggestions

We had two JL Fathom f113 subs come into our shop a few months ago. The customer had blown both w7 13" woofers and there is damage on one of the amp boards. The quote for repair for the subs was nearly 2/3 the original cost of the subs so the customer just left them here for us to deal with, so I took them home to try and repair. I was able to get parts for rebuilding the woofers from the guys at Lord of Bass online. I have both woofers rebuilt and installed and amazingly I have one working sub! Unfortunately the other sub had a loud whine as soon as I powered it on. The noise continued after I put it into standby and only stopped after the caps drained. I tested the transistors on the output and 5 out of the 8 were shorted. This is where my knowledge of trouble shooting amps ends sadly. If I can get any advice on how to move forward, I would be most appreciative. Mostly I need to know how to tell if the drive boards are damaged before I install new transistors. I don't have an oscilloscope.

Hi all,

I would like help choosing the correct thermistor/s to place on the primary of my 400va XO. It supplies dual 25vac to 6 lm3875 gain clones, each with 2 x 1000uF caps. Trying to preempt nuisance blowing of fuse. I have several CL60 CL50 CL80 on hand.

Thanks for the help.

Gary

300 watt subwoofer amp with speaker and line level inputs. also has an LFE input if your using it for home theater.

No hum at all. I have had other amps, all of them with hum, but this one is dead quiet.

Controls include auto/standby power, phase, volume, and crossover frequency.

$125 plus shipping.

To all vintage enthusiast & FM experts, I had this unit on my bench for a while now.
When I feed the unit (via Variac) 60 VAC the FM band is perfect, low noise, sensitive station tuning even without an antenna.
No stereo light (sound is only present when pressing the mono button).
As soon as I plug it directly to 120 V there is distortion & noise all across the FM (stations are still there but much lower sound quality & garbled).
AM & all other inputs are working fine.
The 76 Khz signal on PA1001A demodulator is present until the a certain voltage threshold then it disappears.
The majority of the elect. capacitors have been replaced, perhaps it is a power supply issue or one or more components that are failing beyond a certain voltage. Looking for other opinions. Thanks

I'm looking for a service manual and/or circuit description for the B&K ST-140 or ST-140M. I already have a few low resolution versions of the schematic, the minimalist owner's manual, and a one-pager on adjusting bias that applies to multiple amps. I'm not sure if they ever produced a model specific service manual but I'm hoping somebody can help me out. I've split a stereo version of this amp into two monoblocks, and on one of them the bias is low and will not adjust up when trimmed. Looking for insights into the circuit so I can address that. Thanks in advance!

A question for you digital aficionados.
I have been playing around with a Up2Stream board, I note that the supplier offers an optional DAC expansion board (ESS9023) which allegedly improves the sound quality.
Having an old DAC laying around (HIFIDIY 8*TDA1543) I am wondering if it’s possible to bypass the SPDIF receiver chip and connect I2S directly to the DAC, or is something more required?

Looking for 1x LL1638-4H

Anyone have one lying around or can point me to where they have stock?

Amperex MR-123A DHT transmitter triodes, aka FR-123A. Four of them.
Similar specs as 211, 845, trioded 813, etc. 1kV-1500V plates, 10kohm OPT... With minor mods (top cap for plate) these can be rolled in 211 and 845 amps.
These are unused but the boxes rotted away so they have no box. Carefully packed into a relatively solid cardboard box. Ships from Norway, so that is probably coming at 100USD for non EU, and perhaps 50EU for EU.
Will make a great DHT SET amp at roughly 20W output. I just don't have time so want them to find a new home...
Asking 600USD for all four + shipping. OBO...
Compare to new Chinese 845 and 211, or other NOS 211s and 845s on ebay this is a great deal! Besides if I don't sell, eventually I can build an amp with them, I just don't have time for a long while and if good offer (600USD) I will let them go... (I have them on 'bay for 800USD)

Looking to build smallish portable set.

Powered by Bluetooth 2.1 amplifier with batteries .
The idea is to have 2 speakers being joint most of the time to carry around easily but also be able to separate both of them when I want to hear stereo.

So what are some ideas for locking mechanisms to join the two speaker boxes. I am thinking of having a sub that might also be attached at the bottom of the two speakers
The sub I'll probably not carry around too much..
Speaker boxes are around 6x6x 12 each.

The cheapest might be using wellpro to join 2 speakers but was hoping to find something slicker

Is a pair of IRFP150/9150 in class AB possible to operate in 60V rails ?
Thank you

Please, please forgive the newbie amateur post. I purchased some of the red LM4780 boards designed by Peter Daniel and Brian GT many years ago. When I turn on the power, you can hear a soft turn-on thump, but it will not pass signal. I assume the chips are in muted mode. After looking at the datasheet, I am still unclear as to the method of disabling the mute, so the amp stays on. Pins 14 and 20 are the mute pins; do I apply voltage or ground to turn off the mute?

Hi all - just took delivery of a new pair of Faital Pro 10PR320-16 drivers, and was surprised to measure fs at 65 & 68 for the two drivers (out of the box) when spec fs is quoted at 50Hz.

They've come down a bit (both to c 60Hz) after a few hours of burn in - but on last measurement they had both stopped changing.

Is this level of difference (c.20%) from specs normal for Faital drivers? Given I need a pair of 50hz drivers, I am feeling a bit hard done by.

Anyone have any thoughts?

We just discussed ultrasonic noise from Class D amps in a different thread but it would probably fit better here.

It seems people are concerned about Ultrasonic noise polution and I want to have a look into that. So it's about HF noise through your speakers from left over switching frequencies (and every design has some of that).
So I made a few quick measurements with an amp of mine based on Hypex NCore. HF peak is at 70kHz and up to 20uV there, summed from 10-90kHz it's about 600uV. 10-20kHz it's about 19uV (15uV(A)) - so the main part of this is actually HF from 20kHz to 60kHz.

So in my opinion that's absoutely no concern about! Actually you have to search hard for tweeters which will do anything at 70kHz (Bliesma T25B can do this).

But there are so many Class D designs out there - what are your experiences and measurements? How doe ICEpower and Pascal modules do in this regard? Or cheaper chip designs? Any measurements available?

Has anyone reviewed or looked at the new Alpair 7MS or 10M?
Also what are people using for cabinet construction since Baltic birch has disappeared from the Market place?
Rockler has American birch plywood in 3/4" 24"x48" in stock & 1/2" on back order into January- is this a good substitute?

Would the new 7MS work well in the Slim Classic GR dMar-Ken7.3 2v03 cabinet? I used this cabinet for the 7P & it turned out very well. I do keep it out of direct sunlight.
I have 3 sheets of 1/2" Baltic birch I intended to use for the Aplair 7 that I missed buying and now currently unavailable, replaced by the new 7MS.
I veneer 1/4" cherry over the Baltic birch to achieve 3/4" for cabinet density and 3/8" round for the driver opening.

I have not been active on the site since before the Alpair 7 was discontinued & Baltic birch has been hard to find.

Itch'en to start a new speaker project for the Livingroom.

A year ago lost a month apart to the day a father-in-law from Covid & brother-in-law as a collateral death- could not find an open ER due to ER's being too full to see him in time & he bled out from a non Covid health event.


Hope others here have faired better and are in good health.
Thanks in advance. Happy Holidays present & forthcoming....

​

Hello everybody happy thanksgiving ! i have a question about some resistors using in my old speaker ..... I was try to swap some old oxy cable inside and had a chance took out both crossover out of the speaker and found out the manufacture had used two difference brands of resistors in midrange drive section L and R crossovers ......had measure for all the resistors, fortunately they all had the same value , they are in Series 1.3ohm 20w x 3 .. 3.9 ohm total , i feel weird and bad why they did that ?? I think i have to change it. go to the store , the only had 1.2 ohm 20w and 1.5ohm 20w in stock , should i go for it ?? using 2 x 1.2 ohm + 1.3 ohm ?? or go for all 1.2 ohm x3 , sound may be difference ?? please suggest. Thanks .

Hallo gents,

has anyone out there already compared the Telefunken open baffle which can be seen at "glow in the dark audio" by Kevin Davis with the open baffle from the japanese magazin "Stereo Sound" in the artikle "Tube Kingdom" which also can be seen at "je labs" by joseph Esmilla? Regards from germany, Stefan

While browsing through some old Audio magazines I came across this article for an amplifier which uses a three triode phase inverter. Since I like the Van Scoyoc cross coupled inverter, this one stood out. The author has a patent on it (below), but uses a modified version. Here's the article. Thought someone might be interested.

I also saw an amp that uses this version but with type EFP60 secondary emission tubes. I have some of those but no sockets. They're a strange looking loctal style but with 9 pins.

I’m in the process of moving so it’s time to list some excess after figuring out what I’ll need for two speaker builds. Shipping from MA but would prefer pickup for the drivers because I don’t know how well they’ll survive the trip. I have no idea what to price the drivers at so I’ll list them at 75% retail at most, or parity with used market for anything I can’t find new. I would be glad to do bundle offers.


2. Audio Technology 4H520613SD - Works great, just not what I’m looking for (I’m using a similarly sized C-Quenze version). 270 euro each new, listing at $400 $300 $250 $225 for the pair.

3. Audio Technology 6H521706SD - also works great, using the 8 inch version instead. 400 euro each new, $600 $450 $375 $325 for the pair.

4. Usher 8945A - a little dusty but works great. $130 each new, $195 $125 for the pair.

5. Unknown Usher 7 inch - I don’t know what these are. The box says 8836AC but these are definitely paper. The 8836AC was cleared out for $49 each so I can do $80 $60 for the pair if you buy another pair.

6. Scanspeak 21W/8554-00 - Probably needs to be refoamed. I’ve seen people sell them for $200 a pair but if you buy another pair of drivers I can do $125 $100.

Hello, I'm looking for some genuine Supertex DN2540N5-g possibly in EU.

These M2 boards came out of a working amp a couple years back. Just to be safe, I recently inspected, cleaned (some residual flux), bolted them to heat sinks, and tested on the bench...they work fine. They have the Harris 9240s installed. Also, they have Faston 110 spades installed (input, output, ground etc.). I can remove the Fastons if you like. Asking $100 plus shipping. I'll include the Tea Bag PS board as well.