I hauled in a bunch of push-pull audio transformers to test on my AC sine wave source at work. I generally test using a 50V, 300Hz sine wave. I monitor the output with a DVM set on AC, and look at the exciting current with a Yokogawa WT210 power analyzer that is also hooked up to the sine source. That way, I can determine turns ratio and from the exciting current, I can calculate primary inductance. I had some unknown transformers that looked good for ~40W (on the hefty side) that tested out at around 6k:8, a pair of "7k:8" transformers that tested at around 6.6k:8, some Baldwin organ transformers that tested out at ~3k:8 (probably wound for 16 ohm speakers), and some bitty transformers that tested at around 10k:8, with not a lot of primary inductance. Next weekend, I'll bring in some Wurlitzer P-P transformers that came off of an amplifier that used 7868 outputs. Fun times ahead, as I figure out how to purpose all this iron...

I'm not sure if I raise relevant question or nor, and whether to post here or in the room correction forum. My wondering seems just in between...


I stumbled on the Kii Three and D&D 8c pitch that they can achieve almost perfect operation in "normal" rooms. This seems to rely on the consistent off axis response of the speakers.



Then going through different threads this leaded me to FIR correction as performed with Acourate or Audiolense products (and DRC-FIR for the open source more steep learning curve). This was looking really interesting to improve the system in the room, at listening position. I have bought and read "Accurate sound reproduction" from Mitchco.



Then to Grimm LS1... and the associated whitepaper https://www.grimmaudio.com/wordpress/wp-content/uploads/speakers.pdf . That whitepaper was highlighting the drawbacks/restictions of the FIR approach, especially on the off axis response... Arghh so some promote FIR to solve key issues, but this may impact significantly the off axis response, which is important for imaging and timbre and the secret of LXminis/Kii/D&D.


I started to get bugged about the interest or not to invest time (and money) in FIR correction, either for complete speaker filtering (each driver ground up FIR filtered for listening position) or for final lifting to adjust speakers for listening position.


Is the Grimm whitepaper a bit pushy comparing very different designs related to off axis response (controlled directivity LS1 to MTM arrangement) ?


Can the FIR final corrections be adequate with Cadioid like speakers like my LX-Mini, and would not degrade too much the Off-Axis response?


Is the jury still out, or my problem hill defined ?


(my use case, out of the curiosity/want to learn part, is to have as good performance as possible with my LX-Mini at listening position, in a difficult room (not symetrical, low ceiling, little acoustic treatment possible...).


JMF

Guys, hello.

Here is a story.

This amp is 12 years old now.
I tried to tune idle currents for this amp to be around 3-3.5mA (this voltage is indication of correct idle currents) on each channel. These values are specified in service manual (attached to this post).
Year ago I was able to do this, but it was very hard. Probably because original trimpots were very sensitive, lacking of control.
This tuning inproved sound quality a lot.

But now the amp sounding a bit dead. I read the idle currents values and they went to 5mV and 10mV on channels. So I tried configure the idle currents again but I can not do it any more.
So I decided to replace original trimpots with new (better version)
BOURNS - 3296Y-1-201LF - TRIMMER, 25 TURN 200R
And replacement went well.
And for the first time after replacement I even managed to configure the idle currents to 3.1mV on both channels.
But after couple of hours of listening on average volume the sound went bad again.

But what I see now is :
1) On one channel with trimpot on minimum resistance of 0.5ohm I have idle current is 5.4mV.
If I increase value resistance of trimpot, the idle current goes higher. So no way of getting of 3mV.
On average on this channel the resistance of trimpot is tightly connected with idle current value.
2) On other channel trimpot has value of 120ohm and idle current is configured on 5.4mV.
If I go to lower resistances, then for very long range of them I see no change in idle current, but then it starts to lowering to 4.5mV and then it drops down to 1.2mV. Then, if I go with higher resistances, then again for long time I dont' see any change in idle current and then it jumps up to 4-5mV. So I am not getting the desired 3mV. Such bad not linear behavior.
So, on this channel I see that resistance of trimpot is not very tightly connected with idle current value.


Why such issue can happen?
Do you think that transistors went bad?
If yes, then which once do you suspect?
There are three pairs of transistors on each channel (as I understand).
First pars is small (SMD), second is bigger (vertical PCB mount with small personal heatsink) and then comes the biggest one (Vertical PCB mount on huge heatsink).
But I don't understand (due to lack of experience) which pair is controlled by trimpot and which is not.

Please look on attached schema.
Trimpots have markings of VR103 and VR303.

I measured resistors that are installed in series with trimpots R432 and R232 and they have OK value (slightly above 500ohm, as per spec).
Also both R233 and R433 are fine.

Thanks a lot.

UPDATE from 15/02/2021
SUMMARY OF SOLUTION in my case (for people who does not want to read the whole thread):

The leaking elements were Zener diodes D322, D323, D122, D123.
After replacing them (with MMSZ5231BT1) I got full control on idle currents on both channels.
While replacing pay attention to orientation, see service manual for reference.
Important: don't heat the new Zener diodes for more then 10 seconds on 260C temperature.
260C is enough to solder new diodes in place.

Hello, I would love to buy some moths to make a pair of SLOBs like the speaker camp builds. If anyone knows a good FR alternative with the EQ values for the LX-mini cross-over, I'd also be interested in that. I know about Papa's values for the Cube Magus, but those are quite expensive. Thanks!

Perhaps one or more of you more knowledgeable folks are able and willing to assist me! I have had an AR-1500A for many years, I built it in 1974. A couple of years ago, I decided to replace all of the caps, and did so. i inadvertently reversed the power supply caps, which of course blew, taking the four rectifier diodes and one transistor with them. I replaced all of the burned items, and now the power supply is fine. However, there are now other problems! When using a 60 Watt light bulb in series with the AC mains, the bulb burns brightly. I removed each PC board, using the process of elimination, and learned that with the Multiplex board and the FM IF board removed, the bulb now glows normally. Of course, I have no FM, that is to be expected. I then temporarily replaced each of the two boards, with known good boards from another AR-1500A, and ditto, no FM, so I now also suspect a problem with the FM tuner additionally. I thought I'd work on the boards first. I began with the IF board, checked each resister and transistor, removing each from the board. All check good, with the exception of Q204 and Q205. Both have been burned. Nothing else appears to be burned. Nothing appears burned on the Multiplex board, but I have not as of yet checked any components. I did remove the six electrolytic caps from the Multiplex board, and with them out of the PC board, I can reinsert the board into the AR-1500A, and no excessive current draw, but of course, not FM either. And with both Q204 and Q205 removed from the FM IF board, I can also reinsert that board as well, with the same outcome, no FM. Amplifier sections works normally, as does AM. I only have a variety of multimeters for testing, perhaps one or more of you could direct me to a suitable capacitor tester for purchase. I see many advertised, most require 1-2 months from China to be received. Any comments at all would be appreciated. Thanks much

Howard Spivak

Most all items appear to be out of stock and the Noval pcb that was displayed as available was in reality- not. Has anyone actually received boards from them recently? Is this typical of dry spells the site runs through?

In folders of music by my daughter I noticed there are duplicate m4a files that do not play but start with ._track number (eg ._01). I know she did these via iTunes on her Mac where my files via iTunes on Windows do not have these. I tested by deleting these files and had no detrimental effect and have nothing to do with album art. What are they (see example below)?

I wonder whether these data sets, together with the voice coil construction image, are sufficient to allow the driver manufacturer, probably a modern Chinese company, to build a driver.

Driver type: dynamic
Cone diameter: 10 inches
Cone material: copolymer
Surround material: butyl rubber
Impedance: 7.6 Ohms
Voice coil diameter: 2 inches
Voice coil former: Kapton
Magnetic flux density: 0.9 Tesla
Magnetic flux: 1.17 x 10^-3 Weber



Credit for picture: tysontom of “classicspeakerpages” forum

Not sure how many of you boys do the vacuuming around your place but I am one of them. My wife is unable to so I'm the man. We had a Dirt Devil upright corded unit that we bought new 10 years ago. Because of my right side injuries, it was becoming quite the nuisance. We have laminate floors with lots of runner carpets and area rugs. Adjusting the roller brush height was an ongoing job.
I used the old vac for the last time and then ordered a Dyson cordless on Sunday as they are having the Black Friday week long sale. It arrived 2 days later and just for fun I decided to run it over the carpets that had been done 2 days prior.
I could not believe my eyes when I saw the amount of dust and dog hair that it picked up from recently vacuumed areas.
I am now a walking advert for the Dyson V10.
Okay, enough said. You guys don't really want to hear about vacuums anyway, unless of course were talking tubes. 🙂

Hi gang,

I've been a lurker around here in the past and now have a need for some specific help.

I recently purchased a mid-90s Conrad Johnson Premier 14 tube preamp. I am getting a static-like noise in one channel, then some frying egg type noise that usually ends with a mild pop. Then the pre settles into the static noise, repeating the egg frying pop again. I don't perceive a change in loudness of the noise with volume on the preamp and input source or no source have no effect. The previous owner had noted this noise as well and stated it went away after a few minutes. I have listened to it for 30 min or so and still didn't hear it calm down, though it seems to get less frequent with the pops as time goes on. Last night I decided to let it stay on for an hour or two before listening and then it was quiet. No static, nothing for the next couple hours I listened to music.

Diagnostics done so far: swapped tubes around L to R, and mixing the tubes front to back (there are 2 per channel). Noise seems to always stay on the left channel. I pulled the tubes in and out about 20x and gave then a brushing with the dental flossers and I will pick up some Deoxit this weekend. I retensioned a couple of the socket connections as one socket (on the left) seemed looser than the other 3. I have used the chopstick method and nothing changes the noise. I did feel like one time when the frying was actively happening wiggling at tube might have changed the sound, but that could have been coincidental.

Some info on the pre: It uses two 6GK5 tubes per channel, which mine are currently a mismatched pair of mullards and another brand. The volume control is a series of resistors and relays, effectively making a step attenuator. Vishay metal foil resistors and CJ poly caps in most everything short of the power supply.

What do you guys think I should test? I do need to get a complete new set of tubes just in case I have 3 bad of the 4. I am a little knowledgeable on working with electronics, enough to know how not to get shocked and I am handy with a soldering iron. I have read a ton on this and plate resistors come up a lot. Is there a way to test without unsoldering? Can I pull the tubes and check resistance or power up to check the voltage to see if L and R match?

Thanks
ben

so i have a esx signum se7000d that i been working and learning on. So after changing some bad parts the protect light is now solved however the output relay are not being engaged, sometime it engaged and would dissengage soon after. twisting or bending the pcb wouldnt do anything,then i recently came over this tread https://www.diyaudio.com/community/threads/crunch-class-d.395669/page-2 where they talked about shutdown pin2 on ir21844 which where internally supplied by 5v which i did not have after removing pin 2 from ir21844. before removing pin 2 it was about 2.5v referenced to terminal ground and after removing pin 2 it dropped to 8mv but had 5v at transistor which connects throught a resistor then to pin 2. after changing ir21844 i still had no 5v on pin 2 but somehow the amp engages the relay and stays on like normal with sound output.
why is there no 5v on pin 2 and i am worried that reconnecting the transistor to pin 2 that it will blow like all other ir21844.

Back in 2020 I was building my SSE and chose Transcendar OPTs for the build. Some may remember that I also got a crazy good deal on these Chinese "Laidys" OPTs https://www.diyaudio.com/community/threads/rolled-the-dice-on-chinese-opts.348858/post-6422961

Recap: They weigh in at 990g, cost me ~$80 CAD total (for both, including shipping) and they are ugly AF. 5K primary and 4/8ohm secondaries (with UL tap). 38 Henries.

I plan to build a TSE-II (w/45s) and I am gathering parts. Apparently, Gery isn't winding the Transcendars anymore. It occurred to me that I could rob the Transcendars from my SSE and use them in my TSE-II build, and swap the "Laidys" into my SSE.

So, that's what I did. This is the first time I have ever even heard these OPTs and I must say they are quite decent. Everything from lows to highs all sound perfectly pleasant to me, even when I push some fairly loud SPL. I will give them a more thorough listen this evening.

I'd like to say it is hard to find fault, but it isn't. They truly are the ugliest OPTs I have ever seen. Would be a great OPT if "sleeper" amps were a thing. You know, like those sleeper cars that look like a piece of junk but have 600hp under the hood and can do 0-60 in 5 seconds.

The bad news? Sellers on ebay seem to be asking around $90 each (incl. shipping) for these same OPTs now.

I am recapping HCA-1206 and i would like to perform all work that was done by @Tsipkin in following post. Is there someone who can provide part list for it? i got the basic caps down but i can figure out other parts that i should replace. Any Mods you can recommend to better the sound are also welcome. This is my first time i have good friend who can replace the things for me and he agreed to do it 🙂 but i just need to know the parts and things i should replace. There are 4 bord. 1 seems like power supply 2 are for Chanell and one small by the input.

My current List
47uf80V X 48
10uf80V X 2
1000uf100v X 2
220uf100V X 2
220uf100v X 4
220uf25v x 1

https://www.usaudiomart.com/details/649982032-parasound-hca-1206-amplifier-fully-upgraded/

Does anyone have a stash of these? They are dual emitter resistors, with leads also on the top to clip Alligator clips and measure bias/ vdrop etc.

died on Dec. 29, 2023

I have a S550 e that has gone cold on left channel. I live in Las Vegas and am looking for someone in so cal or near me to take it to to be gone through. Any suggestions?

I need a new phono preamp and would really prefer a tube preamp like the Hagtech Cornet 3. I’m not looking to spend a lot of money but let me know what you have. Thanks and have a great day.

Hi All. As a project looking at an ACA set up as bridged monos. Can these be wired up in one case as in four modules in one case so a mono amp on either side as have a case to use up? Also interested in the Toshiba MOSFETs jfets as an upgrade has this been done successfully? Thanks for all your suggestions

Hello all,

I recently acquired an auto-ranger - (thanks ItsAllInMyHead) for the workbench.

To complete the auto-ranger, I am looking for a Linear Audio Silent Switcher power supply. Does anyone possibly have one they would sell? Or maybe suggestions on where to find one?

Thanks in advance,

bmdduck

@ jhstewart9 posted this schematic of a Hybrid Transimpedance Tube amp a couple of days ago : https://www.diyaudio.com/community/attachments/transimpedance-amplifier-hybrid-jpg.1158737/

It was presented in Wireless World Mag Oct.1995. I only found a poor, blurred copy of the article and a schematic with all the component values (attached).

So far I understand it the transimpedance part is buried in the sand and not in the vacuum.

Anyway, over the weekend I put it into LTspice but the result was devastating:

• extremely distorted output even at low levels (claims are 32 W and 0.07% THD at 20 W)
• phase splitting is not working properly (quote from the article: "Phase splitting is produced by coupling inverting inputs A1 and A2 together via R11 and C4. This results in two antiphase equal amplitude signals to drive the output stage." unquote)

This is not the case in my sim (attached)
Tried 3 different opamp models TL082, OP07, NE5532 to no avail.

Questions:

• How is the phase splitting supposed to work ?
• And why does it not work in my sim ?

A friend of me use since any months for his no longer available Kaisaya power amp units (Accuphase E505 clone) - go to
https://webcache.googleusercontent....005002934655996.html&hl=de&gl=de&client=opera
a power transformer from this series:
https://sklep.toroidy.pl/en_US/c/To...EME-AUDIO-GRADE-V2/99/2/default/1/f_ov_8_78/1
this version:
https://sklep.toroidy.pl/en_US/p/TT...ade-transformer-TSAS1500VA-voltage-to-50V/427
No mechanical hum and very good sonic performance are recorded.

This brands are also known for good quality, but more expensive:

1) Tauscher (Germany)
https://www.tauscher-transformatoren.de/assets/pdf/R_11.pdf
https://www.tauscher-transformatoren.de/assets/pdf/R_14.pdf
2) Plitron (Canada, now Noratel)
https://www.noratel.com/news/news-e...nounces-rebrand-of-plitron-manufacturing-inc/
https://www.noratel.com/products/type/bespoke-oem-design/
https://web.archive.org/web/20050223084832/http://www.plitron.com/ (go to products, then "low noise transformers")
https://web.archive.org/web/20050215093935/http://www.plitron.com/pages/technote.htm
https://web.archive.org/web/20130705130420/http://www.plitron.com/

Could it be that these brands have a number of further advantages (like e.g. an integrated snubber network) that one don't find at Toroidy?
Thanks for any information.
check out also this threads:
https://www.diyaudio.com/community/threads/what-makes-a-good-audio-power-transformer.12611/page-3
https://www.diyaudio.com/community/...rmer-snubber-using-quasimodo-test-jig.243100/
and page 103 from the attached PDF

Hi all,

I've designed a biradial waveguide for my tweeter in CAD (linear horizontal expansion and exponential vertical expansion). Looks great, although I can't quite get my head around how I would could the ideal crossover frequency for it. I've analysed it in AKABAK (using youtube tutorials) but not quite sure what I'm looking out for. Tried searching google but the results I get aren't quite what I'm trying to ask - maybe I'm wording my problem wrong.

I'm trying to optimise a wide directionality for an open sound.

Fairly new to DIY speaker design and building, and very new here so apologies in advance if I've posted this in the wrong area.

Any nudge in the right direction would really help.

I recently picked one of these up in very good shape and within specifications. It is an audio range filter - 99KHz max - and I'm wondering what it would be used for in practice.

Thanks!

Want to buy a pair of XRK RTR SSR Speaker Protection boards of to send to Spain, peferably from EU. I prefer last version.

I'm looking to buy one single 2SK77. I'd like to build ZenMod's Singing Bush - the Larch.

Taking a break from tubes, one is naturally drawn to static inductive transistors. The specs are what tubes could only dream of and would enable the most compact two stage and high quality headphone/speaker/linestage. Luminaria was a great paper to get my feet wet and so an idea emerged, why not treat them like tubes? After much planing this project came to life:



The resolution this amp brings was hard to believe and a punch in the face to my tubes4life mentality.
2SK79 is running at 4.5mA and should have 2K rp, the AVC takes care of the input capacitance of the 2SK82, not only is it a volume control but at my listening level the output impedance is well under 100ohm, Pass recommends under 600.

The UTC LC-33 allows for fine tuning of the output and input. The return to cathode works really well with the caveat of floating output.

Hello, I have a modified AR EB101 turntable that sounds good but I have the common problem of the 12-stepped AC motor on the way out! It looks like I must go the DC route which is easier than fitting another AC motor but do not want to buy into the Origin Live setup.

I want something that quality-wise is going to fit into my system so I am looking at a Maxon 110945, for speed control a Motor Speed Controller PWM Regulator on eBay, and I already have a TeraDak 30W PSU Regulated Linear Power Supply DC24V. I am assuming the motor controller will work with the motor.

Any advice would be appreciated - Thanks

I've recently refoamed a Hertz ML3800 because the surround was cracking (https://www.diyaudio.com/community/threads/rubber-coated-cloth-surround-cracking.395384/).

Before the operation I measured the TSPs and they were a bit off - but not by too much. I didn't save those but I remember the Fs being around 42Hz and the Qts being around 0.6. I thought that replacing the surround that looked in a very rough shape would help.
It didn't.
In fact I made it way worse. The parameters are unusable. The Vas is basically halved and the Cms too. Qts skyrocketed to 0.8. The SPL dropped too. I remember I measured 93dB.
The TSPs were measured after about 10 hours of break-in at Xmax with a 10Hz tone.

I think that the surround I installed is way too stiff, however it was the only one I could find which looked similar enough and was of the right size and the same material.
I was thinking that if I swapped it for a foam surround (or rubber, if I could find one of the right size) it would be much softer and it might help.
My guess is, however, based on absolutely nothing, and a Google search wasn't successful either. I fear that this operation might be of more trouble than it's worth.

I wanted to ask if anyone did a similar operation and therefore could share how it turned out.

The driver in question has a "double" center spider, even without the surround it is very stiff and doesn't "sag" at all.
I'm attaching the TSPs of the disaster

SqueezeCore is a project that I had in mind for a long time for personal use.
Now that it's "finished" (aka working) I thought it was worth making it available to anyone.

The main purposes that I have taken into consideration are: a comfortable, fast, plug & play os, which requires (pretty) no configuration and reduced to a minimum to be installed on a thin client (or other low power hardware) used as a player.

The result is an o.s. of 17MB which runs on ram.
The first time it is turned on, a quick configuration of the squeezelite parameters is required (which is optional, it can be avoided by directly editing a file while preparing the USB drive); after this, at every boot and on any computer you'll plug the USB flash drive containing SqueezeCore you can start listening to music in 3 seconds.

Of course, since SqueezeCore is working only as a client you need, as prerequisites, another computer with a Logitech Media Server installation.

Download and installation guide: SqueezeCore

it's still in "beta" because I've tested on a limited amount of devices. Feedbacks appreciated.

UPDATE 20/02/2020

I have released a version with a custom RT kernel.

From the FAQs:

"It is a specific build with a custom Real Time kernel; the hardware requirements are different from the generic version:
Minimal Hardware Requirements for RT:
CPU: Only Intel, Only Core2Duo and newer (Xeon, Core i3 i5 i7, new Pentium and Celeron). 2 core 4 thread (recommended 4 physical cores).
The Other requirements are the same of the generic one.
In the RT version the difference is not only in the kernel but there are other tweaks under the hood like:
The player runs on a isolated core with round robin scheduler.
All the DAC USB interrupts are isolated on one core.
The remaining core are for kernel and the remaining interrupts and software running."

UPDATE 08/07/2020
New release of the RT version. Added the option to configure a static IP

I recently gave my granddaughter my Sony STR5600 and Kenwood KL5050 speakers which she has been begging me to give her for years. I had been using it in the bedroom as a stereo/TV sound system as I have some hearing loss and the speakers in most TVs are lacking for me.

So, I moved my spare 6P41S SE amp and FF125WK speakers to the bedroom, but found the amp does not have enough gain (TV output is very low and I had to crank the STR5600 past 3 O-Clock to hear it).

So I now need a pre-amp. Rather than design one, I decided to see what I could pick up from the Bay of E's for not so much.

I came across one advertised as "HiFi 12AX7 +12AT7 Tube Stereo Preamplifier Board Base On MATISSE Preamp".

Un-assembled kit for $40 plus $4 shipping. I messaged the seller for a schematic and received one several days later.

After entering it into LTSpice, I was pleasantly surprised to see that the distortion at 0.5Vrms out into 100K (6P41S input pot) was quite reasonable at 0.0004%. I was originally planning on redesigning it to use a different output tube, maybe a 12BH7 for better drive and load tolerance. After simulating it I decided to go with it as is for now to see how it sounds.

As it stands, I am waiting for some connectors to arrive to finish the build and start testing.

I was not able to find any reference to this board in searching the site.

Full construction time was less than 2 hours. They just don't supply input and output connectors, although the spacing supports them.

Has anyone else built one?

The design is basically parallel 12AX7s common cathode circuits cap coupled to parallel 12AT7 in common cathode with feedback from the output back to the cathode resistor of the 12AX7 stage.

I’m using Museatex idat44 DAC in my system. It has optical and coaxial inputs. I connect the coaxial input to Yamaha YBA-11 bluetooth receiver and inexpensive Android TV via optical input. After living with them for a period, I recognize that it’s time to upgrade the source. I will keep the YBA-11 in place, but the Android TV. Are there people using Apple TV as music streamer? The new generation Apple TVs no longer have optical output, to use it as an audio source, HDMI output port is the only channel to deliver signal. In brief, to connect the Apple TV to my DAC, it requires to connect Apple TV to the Android TV via HDMI first, then, from Android TV to the DAC via optical cable. The question is will the digital audio signal received by the DAC belong to “Apple TV” or “Android TV”? Remember the objective of this attemp is to discontinue the use of Android TV as a digital audio source and switch to Apple TV instead. So if config the system as mentioned, Apple TV —> HDMI —> Android TV —> Optical —> DAC, will it considered to be the upgrade? Finally, is it worth to invest the Apple TV for this purpose?

Hello there,

I'm playing around a CFA headphone amplifier. I was inspired by Accuphase amplifiers to try with CFA design. My friend from https://muzgaudio.com/ helped me to get going (thanks Konrad!), but he can't give me all his free time (which I understand). I'm a beginner analogue designer and a hobbyist.

The concept is to deliver 2W@64Ohms with THD+N below 0,001% for 1kHz. Currently, I'm at 0,004%.
The compensation is taken from the famous article by Mr. Alexander: https://hifisonix.com/wordpress/wp-content/uploads/2012/09/The-Alexander-Amplifier.pdf



The amplifier is not considered stable yet! It is not calculated, just a placeholder.

The topology consists of a diamond buffer in Marantz HDAM 3 topology, a Widlar current mirror and a 2EF.

Operating currents are described in the sim. Please feel free to download and play around with it.

There is a weird distortion in the current between first pair of emitter followers (Q7, Q9):


Can somebody advise? The sinusoidal current in VAS side, degeneration resistors for current mirrors also seem to not be symmetrical (e.g. I R22).

Still to do:
Baker clamps
Bias generator
Compensation
DC Servo
Output stage bias tuning

So I went on Madisound website and was looking for a new project and came across the Fostex Driver’s page and noticed a few weeks ago the Newer FENV line is now updated to the FENV2 line models. That was a short lived updated FE line update. What I got from the update : By eliminating the metallic eyelets new FE-NV series offer reduced harmonic distortion in the midrange. The pocket neck damper developed in the FF-WK series has been adopted to continue the three-point bonding of the voice coil and the damper and cone paper on the same circumference. The shape and material of the dampers have been reviewed for more linear amplitude characteristic than the current FE-En series. Also not shipping paper out with specs. and down loading the specs. on the fostex website. So I guess am posting this to ask if anyone has done any side by side listening or comparisons between the FENV vs FENV2 speakers. I added pictures of both drivers and frequency graphs of both drivers. First graph is the older FE126NV and the 2nd graph FE126NV2 drivers. Jeff

I need some 2SC1775A(E).Any source for them? The China ones are fakes.

Dieter

Hi there. I am making a DIY build with some Hypex Ncore NC500MP boards. There will be a couple of amp modules in a box with custom input PCB for signal detect auto power on, 12V trigger IO, and temperature monitoring.

I was thinking of adding some kind of soft start functionality, i.e. have the amp modules muted on turn on/off, to reduce pops and/or speaker damage. At the moment, this is done by using the amp power good signal to control the amp mute input. Is there any point in doing this if I am controlling the amp ps enable line to bring amp modules in and out of standby mode. For reference, the amp module datasheet is here: https://www.hypex.nl/media/90/08/74/1646057938/NC500MP_04xx.pdf.

If anyone has any comments, suggestions, advice, that'd be much appreciated.

Hi all,

KSA1220 seems to be obsolete and KSC2690 is available at the big seller.

Did someone know which can be used as a good replacement for KSA1220 / KSC2690?

I have a pair of QSC HPR152i clones along with B&C DE250 drivers. The horns are 14"x10" horns. I also have a pair of JBL 2226H.

I'm curious to know if there are any obvious warning signs before I start making sawdust. Specifically, I am concerned about the center-to-center distance between the CD+Horn and the Woofer. I've read before that the CtC distance should not exceed the crossover frequency.

The closest I can get the center to center distance is 12 inches, and that's with overlapping the horn and rear mounting the woofer.

12in = 304.8mm, which corresponds to a wavelength of 1,132Hz. I'm not sure if that horn+tweeter combo will play that low.

As I was perusing through Troels website trying to find an implementation of a waveguide in a speaker design, I came across his Quattro 2-way speaker.

In that specific design, the crossover frequency between the waveguide loaded tweeter and the woofer is 2.5Khz. The wavelength of 2.5khz is 137.6mm. The center-to-center distance per Troels website was 170mm.

Obviously Mr. Troels knows what he is doing and I'm sure he is well aware of this general rule of thumb. So there is clearly something at play that allows flexibility (maybe trading one benefit for another).

Thoughts?

I found a vintage speaker pair has quite weird specification. They’re ADS L1590 speakers. Their specification shows they have woofer-to-midrange crossover point at 350Hz. However, the midrange used is merely 2-inch dome!

So, I don’t think this is the -3dB point of the dome midrange. Instead, it might be an actual crossing point between woofer and midrange, I don’t believe there are any 2-inch domes could handle that low frequency. Is my assumption correct?

If so, the next question is about the roll-off. The crossover schematic also shows the filters are second-order configuration on every section. The question is if the second-order high-pass filter was applied to that 2-inch mid-dome at -3dB point of its natural roll-off, the acoustically combined response of the mid-dome (high-pass section of the mid-dome) should be 24dB/octave instead of 12dB/octave (first 12dB from the filter and another 12dB from driver’s natural roll-off). Is my second assumption correct?

I will make a slim speaker with six identical 5 1/4» midwoofers.

It will be MTM on top. The question is 2,5 or 3 way?

If it will be 3 way i assume serial-paralell wiring og the 4 woofer drivers is best?

But if i choose 2,5 way, how should i wire the woofers then? Could it also be an idea to shade pairs of woofers with different lowpass?

Hi all, I have a naim AV2 I use for AV and realising its now 20 years old I decided to treat it to a recap of the Tantalum caps as I understand these are the units needed replacement at the recommended service interval.

I have my naim power and pre-amps serviced 'normally' and quite capable of doing the work, but for some reason wanted to keep the main amps serviced with correct parts etc. Anyway my question is I have 34 tantalum caps to be replaced all 10uf 35V and I have the correct replacements but after taking 6 out, I have realised they are all very well marched (more so than my 5% replacements) and all measure 11.2uf and all measure the same or close ESR to the new units I have bought. So given I am about to spend many hours carefully removing and adding 10uf (that mostly measure 9.9uf) with similar ESR am I just about to burn £100 and a day or so of fiddling to achieve nothing ?

Any advice on the Tants and perhaps some take more wear than others I did pull one off near the regs as this is feeding the +- 15v Opamp rails and this measures, 11.2uf and bang on for ESR as well. Are naim just avoiding premature failure with the 10 year replacement, I had understood the ESR normally raises before any failure ?

Hi All,

I have a question regarding resistors values that are in between a digital filter and the Dac chip I2S input.
I've noticed that the resistors values are different in every CD player or Dac, some use 300r, some have 1K, some don't have any resistors at all.

I would like to know please why there is a difference and how the resistors value affects the Dac ?

Thanks

I am wondering how to best twist transformer leads? There are the heavily insulated manufacturer installed leads like from the LV secondary winding or the primary windings. A lazy twist seems ok but further twisting seems like it maybe stressing the connections inside the bells. Also the tighter the twist the more the pair of leads wants to coil up on itself - looking non-professional.
These are Edcor type units.
Thanks

A piece of history! I dont have White paper on this but my Memory says those are One of the First Digital cables of Mr. Chris Sommovigo ,ante kimber orchid that should be its commercial effort.
The cable Is 1,5mt lenght and Is serial numbered. It has the original "Illuminati" packing box. . The cable has two small break on the overall cable mesh sleeve that are shown in pictures. But the cable Is internal to It and its perfect. A piece of history! 200 Eur + shipping

Sale BJT set for the new Stasis FE (new design by NP).
The set consists of:
1. ZTX450 DIODES DC:2236 4EA (matched quad)
2. ZTX450 DIODES DC:2236 4EA (no matched)
3. ZTX550 DIODES DC:2322 2EA (no matched)
4. 2SA1381E ON DC:1213 2EA (matched pair) and 2SC3503E ON DC:1349 2EA (matched pair) Called OPTION1
or
5. KSA1220AY ON DC:2209 2EA (matched pair) and KSC2690AY ON DC:2210 2EA (matched pair) Called OPTION2
all matched TRs are measured by hfe +/-5 and Vbe +/-5mV by using DCA75.

Sale price @ US$18.06 per set for both options.
+ shipping cost (ship by registered airmail from Thailand).
Payment via PayPal only.

If you are interested please PM me.

My nobsound ns-20g amplifier dosent show any signs of overheating or lot of disturbance only little bit on high volume I have connected two bookshelf speaker 35w+45w both are 6ohms connected in parallel configaration which goes to 3 ohms
Per channel

My amplifier specs

Nobsound ns-20g
the output power is improved to 200W (100W*2) with 2PCS TPA3116 chip
Suits 5-8 inches / 4-8Ω / 20-120W speakers

Greetings all,

This is my first thread here but I have been a long time reader and learned a lot. I have been an owner for the Le preamplificateur Kanda I have assembled it from the kit back then and I have upgraded the filter capacitors few years back and I am really happy with the sound. However, now I am looking to do some modification and I would be really happy to be advised and guided by your experience. this is the Document for the preamp I have installed and aligned as per the instructions with great help from friends. the sound is great especially in the low frequency it makes my Technics Sb-500 ring the room. I believe the unregulated power supply section is fine unless you have a new idea. please see the picture below. please see the picture.

looking forward to hear your ideas.



Thanks
Ahmed

Hi,

I am planning on getting a minidsp Flex 8 with Dirac live. I already have a omnimic from Dayton Audio. So I wanted to find out if somebody has tried it instead of the UMIK? I tried asking minidsp and the answer I got was the recommended mic is the UMIK.

Thanking all in advance.

Oon

Hello,
I contract IT services and it has expanded into AV integration with RTI / Kramer and URC. I'm just curious if anyone else on the forum messes with this type of thing.

Jeremy

I've had success in making two valve amps with global feedback unconditionally stable, compared to original operation showing unstable operation with certain capacitance only loading. The technique used follows on from Patrick Turner's use in two restorations (a Dynaco MkIV and a 100W UL monobloc). Sadly I didn't get time to discuss this topic with Patrick, but was pleased to follow his lead and test the concept in a Williamson amp last year, and just recently in an Encel X1212 stereo 12+12W valve amp from mid 1960's (aka a Star SA-30 from Japan).

The technique inserts a small low-value inductance in series with the normal voltage feedback signal, such that load current passes through the inductor, as shown in the example schematic below. The inductor used was a modified 22uH open-wound ferrite slug type, with turns removed to get down to circa 1-3uH. I compared stability performance in the Williamson, with results in https://dalmura.com.au/static/Williamson output transformer measurements.pdf.

The Encel amp was unstable with certain capacitance only loading, but otherwise stable with its 13dB feedback as it uses a heavy step network on the input stage to roll off gain. I wasn't able to improve on the stability performance with simple capacitor compensation across the feedback resistor, but didn't go further down that path. Instead I deployed a 2uH inductor and was able to achieve unconditional stability even after removing the step network (which was my aim if practical).

The inductor I used was quite small, and very simple to retrofit in the Encel, and in some amps it may be quite easy to implement. So I can recommend it when squarewave testing is available to check stability.

Ciao, Tim

Newish member here. I have been reading lots on this site and I have learned a lot. I recently acquired a pair of Dovedale 3 from a CAM member for 200 CAD because his technician said that one of them may have a short in the wiring after one channel of his vintage Sansui amp blew. I have put them on a DATS and they measure as I think that they should, so I went ahead and hooked them up.
The cabinets are immaculate and I believe that they are untouched internally but I have not had a look inside. I am used to listening to full-range speakers of various sizes in well-designed enclosures and I like that sound, generally.
What I find with the Wharfdale is that:
The midrange blends well into the high frequencies but the midrange lacks detail and the high frequencies don't sparkle. The bass is kind of wooly and muddy. This is the biggest disappointment as I expected the 12" woofer in a sealed enclosure would give me tighter bass than my Spendor BC1 (recapped). I attached a Schiit Loki and set the 20hz pot to its lowest setting which helped a bit; I am not a bass-head but do feel that I am missing something this way. Playing with the other 3 EQ pots did not improve anything. I have left the rear panel controls for mids and HF at "increase" as I wanted to keep the old resistors out of the circuit. That is probably where I would want them anyway.
On the plus side, there is no ringing on percussive high notes on piano; something that drives me crazy.
These are about 50-year-old speakers and I realize that one usually recaps at this point but I don't just want to throw in new parts as the protocol. I would like suggestions as to the order of operations to improve the above "faults", if possible. I have tried driving them with a big Perreaux amp as well as various Class D amps; Icepower and TPA3255, with a Schiit preamp. That doesn't seem to make much difference.
I look forward to your opinions and suggestions.

I have some Woden Lance with FF85wk and want to move to something larger in the Baby Lab series. (but open to other suggestions)

The budget for a driver is up to $50ea and looking for some options. It's for near-field, 6' away and it's a 2.1 chip amp with a voxel sub.

I don't see the MA 6.x series anymore.

Going up to the FF105wk does not seem like it would be much of a change.

That leaves the CHN-70 and the Pluvia 7 - Can someone compare them and explain to me the "Japanese" tuning I saw mentioned? Not sure that is something I'd like if I'm reading it right.

The Storm Shadow just says Pluvia 7 - Is Pluvia 7 PHD the right one?

hello to everyone,
i have designed a 3-way croosover for my active speaker system using minidsp (minisharc). I was just playing with the Vituixcad2 simulator and the crossover i have designed. My crossover is on the picture with the midrange inverted. I am reffering to the low-mid section. Look at the drivers delay. It seems that the woofer must be delayed by 200uS to get the deepest null. One would say that the midrange should be delayed to get that null. All the measurements that i made are 1m at the tweeter level. Now the speaker is working without any delay at the mid or low regions. the total SPL is exactly as the program simulate, so everything seems to be ok. I just thought to play with the low to mid section time aligment and found this. If i connect the input of the low section after the Mid Low pass filter, as i would do if i were to design an analog active crossover, then the midrange section is the one that should be delayed to get the same null. So if i understand correctly the two filters in series in the mid section, introduce larger total delay to the midrange section so finally the low section must be delayed? I suppose that in the minidsp the logic is that the sections are independed between each other, as on the picture, am i right?

AER Sound Gate:
Frequency response curve 20Hz- 20000 Hz +- 2dB
Efficiency with BD 7: 122dB/1W/1m
Size: Wx Hx D: 2000mm x 2000 mm x 300mm
Shipping weight 50 kgs each.
BD3 is plus minus 2dB

You can use from AER BD3B to BD7B..
AER told me the prototype sounds phenomenal.
I have Excentre (1.4M) it is already very good.. I cannot think about the sound of a 2M OB horn.

2M Horn





1.4M Horn


0.65M horn

Hello guys, Imlooking for a good single ended EL84 schematic. I will be happy with bigger power. All my audio projects I worked with were single ended triodes which puts out 2watts maximum. And now I want to try something different.
I have 5k output transformers made for el84 in pentode. My plan is using pentode mode and local feedback including the output transformer so it will have better frequency response.

But where actually start? I have never worked with pentodes.
How to properly implement the feedback?
Sorry for these newbie questions. Thanks much for any reply.
Best regards, Michal

Amplifiers - Feedback/Loopgain stability simulated vs. real world

In many threads here I have expressed my doubts on accuracy of amplifier circuit simulations, especially in two points – very low harmonic distortions <0.001% and feedback (loopgain) unconditional stability. Based on my long, decades lasting experience in designing, building and testing power amplifiers I am declaring that transistor models available with freely distributed simulators like LTspice and others are not accurate enough to simulate neither very low levels of harmonic distortions, nor stability issues with complex load at frequencies >1MHz. I am going to prove my statements on the examples of two real world amplifier samples. And this will be also related to methods of frequency compensation of feedback amplifiers, based on Bode plots loopgain simulations.

Two amplifier samples will be analyzed, one with an old-school dominant-pole compensation, the other with more sophisticated TPC compensation, that allows for more loopgain at higher frequencies, thus lower harmonic distortion at higher frequencies. The amplifiers will be analyzed not only for distortion, but also for stability with complex load and this stability will be compared to assumptions derived from loopgain simulations.

1. The amplifier with the dominant-pole compensation

The amplifier sample has been described here in the thread
https://www.diyaudio.com/community/...er-and-my-diy-mods-schematics-gerbers.406947/

Loopgain simulation says that with a resistor load (4.7ohm) the phase margin at the point where the loopgain amplitude plot crosses 0dB, at 3.75MHz, is about 80°, which is enough for stable operation. The feedback factor (loopgain) at 20kHz is 41dB, which is the factor available for harmonic distortion reduction of this feedback amplifier, at 20kHz. At =<1kHz, the loopgain is 58dB.



Now, when 47nF capacitor is added in parallel with 4R7 resistor, the loopgain amplitude plot crosses 0dB at 2.45MHz and the phase margin is now a mere 14°, so the amplifier should be close to instability.

Let's investigate the real amplifier sample, with a 10kHz square wave as an input signal, and both discussed loads.

Response into 4.7ohm resistor



The response is nicely aperiodic, with no signs of instability. Exactly according to loopgain simulation.

Response into 4.7ohm//47nF



47nF capacitor was added in parallel with the 4R7 resistor, however the square response remained unaffected. This is not in conformance with the simulated loopgain, which would suggest at least heavy ringing, with the simulated phase margin of only 14°.

The amplifier is stable (in the real world) for wide range of capacitances, covering at least 0 – 100nF. First signs of compromised stability we can see with the 150nF capacitor // 4R7:



So, for this amplifier sample with dominant-pole compensation, the simulation was pesismistic compared to the real world results. Something does not fit, models?

2. The amplifier with TPC compensation

The amplifier sample has been described in the thread
https://www.diyaudio.com/community/threads/sab-class-ab-2x50w-4ohm-amplifier-with-smps.386169/

Loopgain simulation says that with a resistor load (4.7ohm) the phase margin at the point where the loopgain amplitude plot crosses 0dB, at 0.95MHz, is about 50°, which might be enough for stable operation. The feedback factor (loopgain) at 20kHz is 57dB, which is the factor available for harmonic distortion reduction of this feedback amplifier, at 20kHz. At =<1kHz, the loopgain is very high 93dB. Brown line in the graph would be a comparison to a dominant-pole compensation with the same unity gain frequency.



Now, when 47nF capacitor is added in parallel with 4R7 resistor, the loopgain amplitude plot crosses 0dB at almost same point near 0.95MHz and the phase margin is now a mere 30°, not much less than without the capacitor, and the amplifier should be still stable.

Another plot is with 15nF capacitor, and we can see that the phase margin is now 43°, definitely enough for the amplifier to be stable, at least in the simulation!



But how about the real world sample?? Alas, the amplifier's response oscillates with 4R7//15nF!



And increasing the capacitor to 47nF makes oscillations with much higher amplitude and the amplifier has suddenly blown the T5A fuse in the +rail of the power supply. But, due to very robust MJL21194/93 output pair, it has survived.

I inserted the 0.4uH output coil behind the amplifier's output ad now it was able to drive 4R7//33nF load with slight signs of oscillations only.



Test bench, load and output coil

So, with the more sophisticated compensation scheme, we have got this improvement in THD+N vs. frequency at the expense of much worse amplifier stability, though the simulations did not suggest the stability worsening.



It is up to you to make a choice, if you prefer some inaudible improvement in THD+N, or an unconditional amplifier stability. And remember, do not forget to use the output coil with feedback amplifiers!

Hi friends, and happy 2024!

Yes I know it's silly. But so is my brain... I'm a bit into avoiding high-tech methods even for high tech products 🙄

Was wondering wether I could make a multilayered board out of the equivalent number of single-layered, self made ones?
You know, with this laser-printing, ironing onto the bare board-method, making one per layer, stack them, and accordingly connect them with a piece of wire...

At least, I hope this is good for a little smile or something...


david🙂

Hi !
Do anyone have a schematic or good picture of key printboard - Clifton SLM-37 = Sheffield SLM-37 ? Both have same internal configuration.
I received one broken, I would like to restore it but is difficult to imagine the originl wiring.
Thanks.

In a common emitter amp like this how do you calculate the ripple current in the bypass cap
having a 4 ohm resistor, 2A bias and 20V ac output. I would like to use a 1F super cap but it
only has a 1.2A ripple rating so I don't know if that is enough.

One pair of Supertech 10,000uf 63V caps. Brand new, never used. Please note, these are special 4 pin caps and will need a purposefully designed circuit board. $40/pair + shipping.

No international shipping.

Hi,

Ceramic caps change with time (aging) and thus are not considered good for audio line level application. After all, we dont want a filter
whose corner shifts with age.
A friend of mine who has good experience in electronics was of opinion that if SMD ceramics are used at a voltage lesser than 1/3 of their
rated voltage then they don't change the value with age and thus can be used for audio crossover.

Whats your opinion? Are new SMD ceramics usable in this application?

Regards,
WA

Small class AB 50W/4ohm amplifier with SMPS (Gerber files added - see page 2) or linear supply

This amplifier is based on Kenwood KA-5010 circuit topology, class AB with 3EF output stage and 2-pole frequency compensation, which promises to keep low distortion even at higher frequencies. I was curious how it would work and built a 1st sample 5 years ago, followed by change of the linear power supply to SMPS's this year – resulting in a considerable loss of amplifier weight 😉.

Gerber files have been released in post #25 for non-commercial, non-profit personal use
https://www.diyaudio.com/community/...-4ohm-amplifier-with-smps.386169/post-7022262

This is the circuit schematics



As a power supplies I used Mean Well RS-100-24 modules, one per channel. This is the amplifier DIY built in one of my prototype cases



Technical parameters

• input impedance 90kohm
• voltage gain 30dB
• output noise voltage 22uV/20Hz-22kHz unweighted
• output power 2 x 50W/4ohm
• THD < 0.002%/40W/1kHz/4ohm
• THD < 0.003%/40W/10kHz/4ohm
• minimum load impedance 2.5ohm
• frequency response 10Hz – 100kHz/0.2dB/4ohm

Measurements of THD and THD+N vs. output power, with 4ohm load







Measurement of THD and THD+N vs. frequency at 20W/4ohm



Distortion spectrum



LTSpice files

P.S.: the amplifier has been re-measured with linear power supply 2x25Vm post #50, https://www.diyaudio.com/community/...-4ohm-amplifier-with-smps.386169/post-7031738

For sale -
1) A pair of Quad 405 PCB's + 5 2N3773 & washers/insulators + 4 MJE15033G + 3 ZTX553 + 2 ZTX694B + length of aliminium L section - part of what you need to build a Quad 405 current dumping amplifier. Comes with schematic, BOM, L bracket dimensions etc . £30
2) 9 pairs of genuine Sanken 2SC3858/2SA1494 Y £10 a pair. All are from the same batches bought from Digikey some years back. Each transistor comes with a mica washer. If you want the lot am happy to knock a few £'s off.

Postage to UK mainland estimated at £3. Drop me a PM if interested, Andy.

For sale is the combo unit of Heathkit's vintage Amp and Preamp duo the ; AP-1800 and AA-1600. The AP-1800 is the deluxe preamplifier/control unit, and the AA-1600 power amplifier. These are both vintage pieces from the late 1970's era of home audio reproduction. They are designed to work together as the preamplifier really acts as a control center - switching all input and speaker selection as fed back into the pre from the amp. These were both state-of-art, and at the top of Heathkit's audio offerings in 1979. At the time, I was a young grad student, and so they were far from my buying $$ reach at the time.

The amp is rated at 125watts minimum RMS/channel into 8ohms, with less than 0.05% THD, from 20-20,000Hz. The preamplifier has equally impressive specs as well. Both of these pieces are extremely clean, with no missing knobs or switch handles. These are both functional, and did produce music before going into storage about 8 yrs ago. While functional, they will still require a good cleaning of the pots, and possibly repair/replacement of some of the front-end transistors in the amp(I believe). I had some distortion in one channel that I never got around to addressing.

Included with the sale are the original Heathkit build, test, and operation manuals - along with large fold-out schematics - and pictorial build illustrations for both pieces. Please refer to all posted images of both.

I'm asking $550 for the pair. All sales are final. Local pickup only.

Thank you for looking.

Edit: Since posting I've discovered there is an issue with the preamp. No output on the left channel. I suspect it is either a faulty mode switch, or in the left-channel circuitry. I have adjusted the price to $410 for the pair.

Greetings. I have a pair of Thiel CS 1.2 speakers with the original tweeters (SEAs from Norway). 6 ohms, crossed at 2,500, plate a bit over 4 inches diameter. I have searched and the Seas Prestige 27bfc/g tweeter was recommended in one thread as one that is pretty close. However, I have found that the Peerless by Tymphany D27TG35-06 1" Silk Dome Tweeter will also fit well and has what looks like a slightly better response curve, both from 3-5,000 and above 15,000. Can any of you share your experience with either of these tweeters and let me know which you would recommend? Since I am looking for a speaker for more background music and not critical listening, I am inclined to go with the Peerless as it is half the price. I also prefer the sound of a silk dome vs metal dome tweeter in general. Thank you for your help.

Just for fun!

Can AI design speakers? Does anything inspire you?

You can access Stable Diffusion on Discord for free.

I bought some lu1014D on ebay a couple of years ago.
But how can I check if they are genuin?
I have a bench supply and a scope and a dmm.
Is this enough to test them?

Hello everyone, I'm currently in the process of deciding which EQ topology to implement for my rotary mixer. My objective is to achieve full kill attenuation while incorporating three essential controls: low, mid, and high. In my quest for information, I've extensively explored various resources, including service manuals. One particular circuit that has caught my attention is the ESP isolator circuit, which can be found at the following link (https://sound-au.com/articles/eq.htm#s9). This circuit strikes a balance between complexity and performance that aligns with my goals.

However, there's a crucial aspect I'm grappling with—namely, the impact of phase shift on the output signal. I conducted simulations of the circuit in the frequency domain using LTSpice, and the results showed a satisfyingly flat response but also a notable phase shift. To delve deeper, I decided to inject both square and triangle waves into the isolator, maintaining the knobs at the 50% mark. What I observed was a distinct alteration in the signal compared to the input waveforms.

Now, there are differing opinions on whether this phase shift is perceptible to a listener. Some argue that it might go unnoticed, but I find it challenging to fully trust this notion without conducting practical tests. Also at the bottom at the page Elliot wrote:

Phase response wasn't even mentioned in any of the descriptions, because it's extremely variable. All equalisers cause phase shift, and the change of phase is much more rapid with a high Q circuit. We can hear the frequency response variation caused by any equaliser, but the phase shift is not audible. There is any number of people who claim that phase is audible, but the claim belies the fact that most programme material has had at least some equalisation, and therefore has phase that varies from the original either for particular instruments and/or for the complete mix. No double-blind test has ever shown that phase shift is audible, provided it's static. Varying phase shift is used to create vibrato (cyclically varying pitch) which is audible, and is used as an 'effect' with many electric musical instruments.

Click to expand...

To me, the impact of the phase shift appears significant enough that it could potentially affect the listening experience. If not, is there a scientific explanation to it?

This was a suggested dual-rail supply design from another forum. I was thinking of trying this but would like some comments on it. It's intended use is powering an audio/speech amp with +/- 280vdc regul. rails and 40-50mA load on each rail.

Note that the regulator circuits are identical and the design 'stacks' them, (rather than the familiar split supply with pos. and neg, linear regulator setup such as LM317/LM337). I see two things that don't make sense:

First, in the top image note how the designer implements the splitting and the zero voltage reference. The positive rail has a 'normal' ground return to its reservoir input cap. The negative rail however does not - the return path looks to be through the MOSFET device.

Second, how do you implement a single reservoir ground? The bottom image looks like the 'normal' way - but it too appears to have asymmetrical return paths.

Hi folks, new here. I'm building a guitar pedal based on the channel strip of an old tape recorder. The circuit used NJM2068SD and NJM4565L op amps, but they don't seem to be in production anymore, so I'm looking for good alternatives that are widely available.

I know the NJM2068 is available. The original NJM2068SD was SIP-9, but from my understanding, the 9th pin was an extra V+ and isn't used in the circuit. Can the current NJM2068 replace it? Pin configuration is different, kinda. The current NJM2068 doesn't have the extra V+ on Pin 1, the rest is the same but moved up a pin.

For the 4565, the LM4562 seems like it might be a good option. Am I wrong?

Thanks for your help!

Hi

I'm having a go at repairing an Adcom GFA-2535, its a 4 channel amp. 2 channels per board. I have the service manual for it. Amplifier A if working correctly, and sounds pretty good, just needed minor bias adjustment. Not new to DIY, very good with a soldering iron and have a few audio projects done. I thought I'd try understanding the circuit and how it works.

Amplifier B, looked like it had come liquid spilt onto it, very dirty, and first thing I did was clean it up a bit



Just clean water, toothbrush, qtips and blew off excess water



Here's the schematic of the one half of the board, I've highlighted the components that tested faulty from my basic understanding



Started diagnosing what was wrong and I've found the following:

1. Both fuses F601 and F602 blown
2. Q625 = 2SA1507 - Short between Collector and Emitter, no short between Collector and Base
3. Q633 = 2SB817D - Short between Base, Collector and Emitter
4. Q629 = 2SB817D - Short between Base, Collector and Emitter
6. D607 = DSC30TC - Shorted

I'm in the process of ordering parts, have some questions
Do I need to replaced the complementary devices for Q625, Q633, Q629 as well?
For D607, should I replace D605 as well if I cant find an exact part match?

For D607, here is the original spec


Mouser has a SR315 in stock. In this position in the circuit, can I use a 1N5822? What does D607 / D605 do?



Any guesses as to what else upstream could be blown based on the info here, would like to get all the parts in one order if possible.

Thanks in advance, looking forward to reviving this board. Have an oscilloscope and function generator to help with troubleshooting after new parts are installed. Looking at getting a transistor tester from Amazon, any recommendations?

Hello
I have a problem. My pioneer sx410 valve amp does not have pre out option. Can I use the tape rec out as a pre out into an amplifier that has the option
Its an amp so I can adjust volume control bass and treble.

I was wondering how this would compare to the TOP-rated Topping LA90 amp? After all the Topping amp is just an LM3886 with special feedback circuits but not as powerful: Ebay ITEM 272913081255

I recently purchased a Velleman K4040 amp which I have wanted for quite some time. It was assembled by an engineer a few months ago from a kit that had been in storage for several years and appears to be well built. It came with Electro Harmonix EL34’s. Looking around, it seems that, while being a good amp, it has some shortcomings and can be modded to make it much better. Being a retired electronics tech and an avid audiophile I want to make it the “best it can be” without a complete redesign. It seems there are some mods that can be done such as replacing the 12au7 tubes with 12ax7’s, replacing the concertina phase splitter with a schmidt using 12at7’s ( https://www.diyaudio.com/community/...man-k4040-tube-amp-owner.383508/#post-6952838 ), replacing the coupling cap’s with 100nF’s, etc.. I would also like to replace the EL34’s with KT88’s but still operate them in class AB1 ultra-linear ( https://blog.easychipamp.com/2020/12/velleman-k4040-tube-amplifier.html ), unlike the Velleman K8010’s KT88 bias of 75ma. I must thank Baudouin0, alexcp, ironradio, arcorob, & others for their excellent posts on the subject. This leaves some questions………. In their K8010, Velleman chose to use 47 ohm cathode resistors for their K88’s while the K4040 uses 10 ohm and ironradio chose to use 6.7 ohm with his KT88 mod. I think I understand why to use 6.7’s if you want to bias for 60ma and use the led indicator as is. Is there an optimum cathode resistor value if a person wanted to adjust bias using a meter and not use the led indicator? Also the screen feed resistor value is something I don’t understand. Velleman uses 180 ohm in the 4040 but I’ve seen recommendations of 480, 800 and 1K. Is there an “optimum” value & does it depend on whether the output tubes are EL34’s, 6L6’s or KT88’s? What would be best for KT88’s? Also I noticed that Velleman chose to use DC for the heater of the 12AU7 in the 8010. Why did they do this? Any help or suggestions would be very much appreciated.

https://www.diyaudio.com/community/attachments/manual_k4040-pdf.1028988/

https://www.velleman.eu/downloads/0/manual_k8010.pdf

Hi everyone, I'm finalizing my new project and I wold like to have your opinion about the crossover.
The main idea in that project was to build high sensitive 2.5 way speaker with simple crossover (as much as possible). So the driver was chosen to match as much as possible with the idea and of course on reasonable price.
So the speaker is already served by crossover V01 from the picture and sound really good. The main concern in that configuration is the low resistance over 10kHz.
So I make some changes in V02 and I wold like your opinion about two of them.
Thank you in advance 🙂

Does anyone here used S1 or S2 with the last version of AN-1, CD player tests (downloadable from AP server) in addition with the CBS CD-1 Standard Test Disk?
The CBS20_S1.apb and also the CBS20_S2.apb seem to be buggy. I asked AP, but these Analyzers are no longer under support. It is NOT a hardware problem, but definitely a Problem with these procedures. I was able to fix a little error in the S2 version (Analyzer autorange off), but the main problem is still there. Bad calculation of the delta value.

I know that this is something really special, and i have little hope. Maybe someone can offer me the classic AN-1 for S1.exe ?

regards
Bert

Hi All,

I have a Yamaha CDX-630E CD player (Based on Sony CDP-207ESD CD player) which I would like to "convert" it so I can use it as a Dac.
My plan is to connect an input board (DIR9001 based) directly to the TDA1541A chip or to the digital filter if possible after disabling the CD function.
I have a few questions and I'll appreciate your assistance:

1. The DIR9001 input board has I2S output (MCLK, BCLK, LRCK, DATA), assuming I wish to use the digital filter can the I2S be connected directly to the IC4 ? where do I need to connect the MCLK output in the IC4 chip?

2. I noticed that in this Yamaha CD player there are 1K resistors before the Dac inputs, in other CD players the resistors values vary(some use 100r some use 390r), what is the effect of using 1K resistor in comparison to a lower value resistors?

3. I noticed that in the CD player's output stage there is not low pass filter, just an I/U conversion stage, isn't it an issue?

4. My plan is to replace C325/C326 electrolytics (which is part of the output's high pass filtering) with PP or other type of non electrolytic caps, if my calculations are correct then the 47uF C325 and 330K R307 form a very low high pass filtering of 0.01hz -3db, is that really necessary ? can I replace the 47uF cap with lets say a 3uF cap?

5. What is the purpose of R319, R327, R309 ? are they necessary or should I bypass them?


Thanks in advance.

Anyone interested in upping their solder skills might want to check out Mr SolderFix on YouTube. He has several tips/tricks for soldering and desoldering, a note in advance, he loves SMFL flux, apparently it is no longer manufactured.