Hi everyone... I am very new to this DIY forum, but I was in other audio forums for many years. I hope I can learn from this group. I am basically from Italy, and I am currently planning to make a tube preamplifier for my current system. I have done many DIY projects before, but I don't know anything technical about electronics. Still, I am planning to build my first preamp. I hope I can ask my doubts here.

Thank you for your all-time

John Mayall 29 November 1933 – 22 July 2024.

What can adequately describe John Mayall's contribution to the British blues scene? He formed The Bluesbreakers, a band that has counted among its members some of the most famous blues and blues rock musicians such as Peter Green and Eric Clapton to name but two.

Hello, my name is Skye, I've been looking at these forums for some months now and decided to make an account, I know a bit of electronics but I'm just really esoterically fixated to amplifiers/reading schematics and speakers (mostly subwoofer) design.

I finally got decent dac, amp and cables. Got qobuz.
Find out what on good system - I hope mine is good- music sound very different to what I used to listen.
Can you help me and share you favorite music what you really enjoy or what giving goose bumps. Or outstanding records.
I think what all of us cut you self short because it very difficult to keep up with all the music. Just too many different choices so too many of them got unnecessary missed or forgotten.
Can you share yours or guide me to web cites to start. All people different and I need to try something new.
It could be ALL kinds of music.

Hi all,

After reading through the forum, I’m a bit confused while trying to design my next full-range speaker.

I’m planning to build a speaker with the SEAS FEA18RCZ 6.5" driver. The speaker box will be vented with a port, and I’m aiming to tune it to 40Hz.

Looking at the T/S parameters, I noticed that the VAS is 31L. After reviewing SEAS' application notes, I saw that their recommended VB is around half of the VAS.

This is where my confusion began. The more I read about the relationship between VB and VAS, the more confused I get.

The suggested application by SEAS doesn’t fit my design goals, and I’d like to understand what the effects would be if I created a box of, for example, 27L, 35L, or 40L (of course port length and size will change in relation to box size).

Additionally, given the physical size of the driver, I seem to be leaning toward a shallow box. Are there any rules of thumb I should consider, such as ensuring the depth is at least twice the depth of the driver, or other factors that might affect the sound? I understand that having the back of the box too close to the driver can affect its performance.

Thank you,
Avi.

I am searching for a 47uF 25v audio grade electrolytic capacitor. Mouser have 100v rated devices at that 47uF value (Nichicon).

The cap is DC decoupling on the output of a 5534 op amp in an audio preamplifier circuit.

What downsides, if any, are there to using a 100v rated cap? I'm vaguely aware that voltage ratings should be kept as reasonably close to a circuit's specified rating as possible, but this is 4 times higher.

Any comments welcome!

Hello,
I recently got old Cary 805b amp and want to refresh some of its caps.
It has Axon 20uf 1200v capacitors and one of them got a bit fried probably by heat from the nearby 10w resistor - so it make sense to me to start from it.
In the usual places such capacitors are not available.
Would really appreciate advise on this 🙌





Following are 2 versions of schematics of these amp.
I marked by GREEN the cap in question and by BLUE 2 other caps (i hope i got those 2 right).

I asked this in my other Karlson Pipe thread but nobody picked up on it yet so I post it here as a stand alone question.

How important is a uninterrupted slot? Vibrations in large tubes are a problem and could be greatly reduced if the tube is not completely cut through. Is there anyone with enough understanding of the principals or a way to model it who can indicate if slot interruptions are OK and how big/numerous these interruptions can be before it starts to hurt performance?



Another way to reduce vibration is to use different layers. I have seen people use metal and polypropylene. Here my question is; what effect does the thickness of the tube wall have on performance/sound? I could use rubber or cork sandwiched between layers of fiberglass/epoxy but this will give a thicker wall than most tubes I see.

If the slot portion has to be thin I could construct something like this to drastically reduce flexing/vibrations.:

ItsAllInMyHead has been kind enough to loan me a pair of Tokin SITs to curve trace.

Here is the first installment. Current limit for this set of curves is 1.5A

Vgs for curves from left to right -1.5, -2.0, -2.5, -3.0, -3.5

Is anyone using these three Scan drivers in a 3 way loudspeaker? Thank you

Hello guys.
I have a Peavey Bandit for repair. Both power transistors have shorted. I had this peavey just a few weeks ago, with both drivers for these power transistors shorted, and an open SZ-13866 dual diode thats monted thru the heatsink. I replaced the driver transistors with the correct replacement parts according to Peavey, but I couldn't find a corresponding diode, so I used a 1N4007 and it worked. Now with this Bandit back on my desk, I suspect this 1N4007 does not behave so well once the heatsink gets hot.
Any idea what would a better diode?

Thanks in advance

Hi, I joined this forum as I've been recently getting into audio electronics building and repair. Currently working on fixing an old Carlsbro spring reverb unit from the 70s. Looking to build custom guitar pedals n such.

Thanks
Hari

Hello all!

I have recently purchased NAD 2200 amplifier but was wondering if I could improve on the schematics. It is probably as good as it is already, but I still wanted to try.

So I have put together simulation in LTSpice from the service manual.

Unfortunately it doesn't word.

Will appreciate if someone could help and point at why it might not work!

Attached are sim files and schematics from the service manual.

Thank you!

These are 2 of the best measuring 15" midbass woofers, money can buy.
I accumulated these woofers moving forward with my DIY effort but because of the design choices, never found use of them. 1, TD15m and 1 15NMB600 has been used to test Thiele specs. The one AE driver was used to predict whether or not I would move forward with it to complete my project and the one Oberton driver was tested by my DATSv3, free air tested by a mic+REW and placed back in its box, The other woofers were not used at all.

As I write this, I think....am I supposed to sell these??? The problem is I cannot justify buying the 18"s I need to complete my project with 6 - 15"s laying around doing nothing. So here I am.

My offer is, these woofers, at the price I paid for them plus whatever shipping is.... which is $300 less than what you can purchase them for now after prices went up. The AE driver is 649+shipping +how ever long you'd have to wait for AE to produce them and the Oberton woofers aren't even available in the states.

--350usd per AETD15M(16ohm)
--275usd per 15NMB600(8ohm)


I am not even sure I am supposed to sell the 16ohm version of the TD15m since I am fortunate to have been able to get them in the first place. Normally a large order is required for special runs of this woofer, as the 16ohm version is not offered. The lighter 16ohm voice coil increases HF sensitivity. This thing sounds almost Full Range....The 15NMB600 is an equally impressive woofer that has been described by some as the best measuring woofer they've found.




http://www.loudspeakerdatabase.com/Oberton/15NMB600
http://www.loudspeakerdatabase.com/AE/TD15M#8Ω

JBL 2384 has «toe down».

Is it possible to use it vertical inwall to get toe-in?

I know i get a narrower sweet spot with less even off axis repsonse. But i like them with toe in to get a deeper soundstage. I move from dedicated listening room to an appartement and will build a wall with TV, bookshelf etc. Then the 2384 must be flush/soffit mounted In the shelf. The ceeling has 60 mm absorbers over the thin planks. The wall left for the small window will have a TV/Hifi/book shelf who is 3,6 meter wide. The wall is 5,4 meter wide. We will have big fat thick rug in front.








This is just to show how the horn is designed. My plan is to tilt it 90 degree.

Folks,

please indicate your interest here if you would like to be in on this.....


I'll let @EUVL do the technical description, but suffice to say they are very neat, fit in a TO220 form factor and you need one set for each channel. The photo below shows them in a heatsink that I used for testing purposes, and gives you an idea of the nature of them.

Fran

So I have a mouser order going in shortly and I’ve decided to give the little 1-bit DAC CDP a refresh. I’ve owned this since new and so I feel I owe it a little refresh to see out the remainder of it’s life.

Inside the MC100 there’s a small power board with a common mode choke (no X caps) with power rectificiation. A small torroid sits miles away. This is a class 2 power device so there’s no protective earth thus the power board doesn’t have Y caps to earth as the only earth is via the shielding connection on the RCA connectors. So no IEC filter without messing with earth (nope not doing that) but I will add a WIMA X2 between live and neutral in front of the common mode choke.
The power rectifier caps I replaced previously after it blew an internal fuse (tray binding). They are now CDE and Panasonic chosen for the handling of 100Hz. That replacement (slightly larger capacitance but not much) improved the sound - especially the bass which then got me thinking for a general refresh of the electrolytics.
The proposed changes are:

Power board
Add WIMA 0.33uF X2 class is my initial thought although I will look for a 400+Vac option here as my mains can hit 252Vac. The PCM22.5 of the 275Vac variant of this has a lower impedance at a point I seem to have noise in the house and this would allow the mains EMI noise to bypass so I'm looking for a high voltage version. The 450Vac MKP-X2 variant is available but 1uF. X2 would mean if there's an over volt, if the cap fails open then there's no issue, but if the cap would short live and neutral and the breaker/IEC power inlet fuse should blow.
I'm not adding any Y class caps because the only route to ground is via the RCA shielding and this is a class 2 device - the route for any internal failure that gets beyond the the isolation is to RCA ground then the amp ground PE pin. There's no PE pin in this CDP (hence adding a IEC filter would need a class 2 medical variant that does not ground the chassis, but searching none of these options have inbuilt fuses! Not worth the hassle with standard IEC filters and insulating the filter metal case from the case and would probably break the forum rules).

Main board supply changes
10V Samsung SSL 220uF -> 16V Panasonic EUU FM 330uF
50V Samsung SSL 100uF -> 50V Panasonic EUU FM 180uF
63V unknown brand 10uF -> 63V Panasonic EUU FR 47uF (10uF sounds more like noise reduction) or the older TA-A series 22uF (not fully decided)

BB OPA2640AP output stage power decoupling (film/polyester caps seem to be next to the chip so we dont need to get too overboard, just a small bunk):
25V Rubicon sky blue 100uF -> 25V Panasonic EEH AZA (organic polymer) 150uF. The low frequency derating of 0.1 (yes 0.1!) is fine as we’re well below that with the OPA2640.

Laser assembly
6.3V nichicon 100uF -> 6.3V nichicon UPW 100uF

I did look at the crystal (whilst pulling and refreshing components). An AEL 33.8688 (oscillator 5V with a 50pF max loading and 100ppm). However this is refresh is to keep the CDP running for the remainder of it’s life. If I want the change the sound then adding a 24bit DAC to replace the Sony 1bit onboard DAC would be the way to go. I’d probably look to a AKM DAC chip with a class A output stage.

I have a stock check as I want to put some power supply PCBs for other projects along with my ADC clock PCB on the same PCB so I’m not wasting the etch. Once those final components are confirmed I’ll put in the mouser order.


Edit: just noted the WIMA MKP-X2 is rated at 400Vac by mouser but in the datasheet it's 305Vac. Hmm I really need 380V peak. WIMA MKX (X1) is rated in the datasheet for 440Vac... phew.

I see a lot of people who use compression drivers in horns that make a cabinet for that horn. I can understand that for live use (to protect) but for hifi why would you make a cabinet for a horn, why not just put it on top of a bass cabinet or use it in a frame to hold it in place (and right angle to the woofer).

I know some do it, but i want to hear arguments pro and contra. Why would this be a good or bad id.

Basic question? Should you twist the blue and brown plate wiring and also the ultralinear wiring. So brown and blue together and then the brown-blue/whites together?? Not sure see pic

What happened to the Alerts blue dots? They were very handy to indicate new posts vs old posts. Now I have to check all my Alerts to see if there is a new post.

I know it dampens the paper cone unwanted vibrations. Something like the soundproofing sheets used in car audio
But it works?

For sale:

2x Gainwire MK3
2x PSU (7815/7915)
2x audio grade toroid 20w

I can guarantee excellent sound

For sale only together. Price 80eur + shipping
Paymet via PayPal

Hi everybody,

Yes I did say that as doctor Nick in my head of those who care. Anyway I'm here as I now need advice on DSP and room treatment all of it will be diy so come along for the journey with me.

Hi

Could someone please help with a Service Manual or Schematic for this preamp

I am having problems with one of these purchased as a working unit only to find that it does not work
I have searched extensively without any success

Thank You in Advance.

Pic from the net

I managed to fry the expensive AlNiCo drivers in one of my Omega "Super High Output Monitors." Eventually I'll probably order a set of drivers ($$$) to replace them, but meanwhile I have a question about whether any of the Mark Audio Alpair drivers might work in the cabinet. I would close the second opening occupied by the low frequency "helper" driver and run it full range, unless the blown helper driver turns out to be a good passive radiator (not likely, I know). I'm looking at the 11MS right now.

I think the volume of the cabinet is about 40 liters. The cabinet is treated internally with R compound.

Fool's errand? Fun and exciting adventure?

Hi All,
I would appreciate some help from the community on the Beast Jr amps.
With Bruce Rozenblit having now made the assembly manuals and schematics available online, I am intending building a pair of these amps, having used their Beasts for many years, but foolishly selling them some time ago. I do have a pair of circuit boards for the Beasts and may build another pair at some point, but as I now use horns, I don't need the power and the Junior's seem a much better bet.
I do, however, have one problem, hence the request for help.
The amp uses Transcendent's patented OTL technology and most of their designs now use the EL509 in the output stage. Here in the UK, the JJ EL509's are £50 each (around US$65) and I need 16 of them. A couple of years ago, I built the Atma Sphere M60's when Ralph kindly put the schematic for his earlier version on this forum. During the build, I managed to buy a large quantity of the 6AS7G's and still have plenty to spare. So the question is, can I use the 6AS7G's in the output stage of the Beast Jr, in the same way that Bruce used them in one of his earlier designs in Glass Audio, back in 1990
If so, how many could I parallel up, and what sort of idle current would be suitable.
I would appreciate some thoughts and comments and look forward to a few replies.
Thanks and Best Regards,
Steve.

Hi experts,
I am repairing Luxman L-100. There are two driver circuits L649 for each channel driving the power transistors. A power supply that is 55 volts DC feeding to these circuits. When I pull up the connector of one channel supply, Left Channel or Right channel it works only that channel which has power supply but once I put connector of both channels, front light keep on flashing. Only one channel at a time. If anybody guide me, I will be thankful to you. Waiting for comments from experts.

Yes, I swap both Channel's power stage but behaviour of amp remains same. This is clearance indication that something wrong with the power supply. It has not enough power to drive two channels together.

Good luck all. I opened a spot for the guide and build of the Pass N Channel VFET.

I look forward to seeing the build come together...

GL

JT

Dear all,

I want to do some mod to improve the sound quality of my mono-block amp, as attached.
As suggested, a change of high quality of OPT would be an option.

As shown, it is a PP with parallel EL34 for each path.

Lundahl LL1663 with 5k:8ohm would be possibly fitted. however, the output power for 1663 is 40w and the output power for the amp in its original design is 50w.

Hammond 1650RA (https://www.hammfg.com/files/parts/pdf/1650RA.pdf?v=1697661945) with 5k:4-8-16ohm,100 watt seems to be another option

my questions are:
1. any comparison between 1650RA or LL1663 for the amp?
2. any other recommendation for the OPT?

Thank you all in advance.

I have been into encaustic (hot wax) and acrylic pours just for fun. Here are some of my paintings.

I have equipped my Pre-amp project with 4x used 6n23p tubes (Russian eq. of E88CC/6922). I had the opportunity to make some simple tests in an OVO tester and the results was not so nice to see. The spread in measures where significant.


As the tubes are used and from unknow origin was this perhaps not to unexpected. Tube #2 are scraped, #3 doesn't look so good either.
My first thought was to buy another set of 5pc, test them and try to match 4 out of my 5+5. After some reading do I understand that the Russian tubes have big variations from the factory. There are also a risk of buying a lot where someone else already has sorted out the the best tubes and resold the not so good ones to me.

There are sellers who claim to have NOS 6p23N: What kind of variation can be expected?
If I buy NOS Philips: What kind of variation can I expect?
If I buy new JJ: What kind of variation can I expect?

Hi,

i Upgraded my NAD C352 with a 356Bee some days ago. The Amp worked absolutely fine and the sound improvement was even a bit more than i had expected.

As i opened it up to clean the inside from dust and get a short overview of the board i immediately saw blewed up a shunt regulator sitting there.

The Regulator ia an AZ431BZ-BE



Unfortunetly that regulator isnt existing anymore.

The only ones i could find were

AZ431BZ-ATRE1
AZ431AZ-ATRE1

As i understood, the AZ or BZ Versions differ in the entrance Voltage tolerance of 0.4 -0.8%

Also the others go from 2,5 up to 36v instead of the Original BZ-BE 2,5 to 18v

So my question is one of these, the right regulator to exchange the blown up one?

If i just can get the 2,5 to 36v Versions is an exchange enough or do i have to regulate something after because of the larger range?

Thanks for any help!!

cheers

I was given some very rough Goodmans Magnum K speakers when I went to collect a Goldring 88 deck.

The drivers worked but the sound was poor. Removed the stuck-on backs with the continuous-pull method. All the capacitors measured correctly at 10 and 4 uF, double checked by running 50Hz through them and measuring current. I replaced the 4 uFs with 2 * 2.2 Polyesters anyway. All four L-pad potentiometers were unserviceable.

The failure mode was high resistance between the moving wipers and the fixed centre terminals. The HF pots were easy to open but I had to get medieval with the MF ones. After all, the pots are otherwise scrap. Cleaning made no difference. Using some very flexible instrument wire I soldered to the wiper and to the terminal. 4 times. Very easy to do.

Result was surprising. The speakers go very low - I was hearing bass notes on the club-dance tracks I never heard in the clubs! This from 35 year-old metal cassettes.

They really are competent speakers for a mid 1960s design. If I want accuracy and realism use the 'statics. For trouser flapping use the Goodmans.

Incidentally the crossovers are similar to but not the same as the cct diagrams I've seen on this forum and others. The signals from the crossover filters go to the centre of the pots. Either the mid or the high - can't remember which, has a 15 Ohm load resistor to ground at one end of the pot's track and the driver at the other end of the pot's track. So you select between sending the signal to the driver or to the load or to a combination thereof. If anyone wants the details I'll open them u[p again.

Hi,
What are viable alternatives to AL1401/2 for ADAT I2S?

***FPGA is too complex for me.

regards.

Hello, would anyone know what the voltages are on the secondary of the transformer in the rotel rsx 1560? The transformer model is 022t-1111n01. I can't find the info anywhere online. Thanks

Hi, I'm from the Czech Republic, sometimes I get my hands on some interesting piece of HIFI technology, so I'll be glad if you can help me to get it up and running.

Hello,

Hope you had a good weekend!.

Looking for guidance and help regarding a t-line design for car audio purposes only.

Driver
Soundqubed HDS 2.208
https://soundqubed.com/8--hds-2.2-series-subwoofer/
called them to confirm RE


I am planning to have two of these. They are Dual Voice Coil 4ohm and will be wired in parallel for a total of 1ohm. Hence I have selected ND as 2P and the same for BL (blp) signifying voice coils wired in parallel. Eg was input as 1000W and 1ohm hence 31.62. Followed the old school guide of line length (196cm) calculated from Fs and line area from cone area (412 in this case as I have 2 subs).



Frequency Response


Next I checked the displacement. It was exceeding max of 13mm but a subsonic or high pass filter at 30hz should take care of that.





I also checked group delay and mouth velocity. From what I have read about ported box, group delay of around 40 is fine. As for mouth velocity, they say that needs to be around 30 but this 45 is at 1000w input. Not sure if at that power I will actually hear the port noise.



Questions I have

1. Assuming this is based on old school quarter wave theory, Have I done or made any wrong assumptions till now.
2. Since my goal is to put the t-line in the trunk of a car, do I really need to care about the sharp drop at 120hz? Most car audio setups will set a low pass filter at 100-120hz if not lower at around 80hz. I have read and simulated that to fix this we can place the subs roughly at around 1/3 down the line. If placing 1/3 down the line is not possible, then even having subs and vent diagonally opposite or as far away from each as possible will help because the "Path" comes into picture. Hopefully my understanding of "Path" is correct.
3. I know this is the old school design and can be improved, but how do I go about it. In my forum introduction thread Dave aka @planet10 mentioned "Sd has little to nothing to do the line design. Vas is what is pertinent". Can someone please explain this to me.
4. The peak at around 40hz I believe can be fixed by some stuffing either in first 1/3 of line or last 1/3.
5. Do I need to worry about Group Delay and Mouth Velocity. If so, how do I reduce those.
6. All sims assume that the box is a straight line, which it might not be and in this case it won't be. What affect does line folding have.
7. If these drivers are not suited for a t-line, then please suggest some others or what to look for when choosing drivers for a t-line.

Questions You might have for me

1. What are the goals? An SQL system
2. Why duals 8's? 8-9 years back I had a t-line in my car but it was not designed or built by me, I knew nothing about t-lines. I lost the car and system in a crash. I want to put subs in my car again and there was nothing I didn't like about it. It could get loud if I wanted it to, and if I turned down the bass knob it would not bother the neighbors 😉. I am trying to recreate the same setup. The exterior dimensions of the box were around 30" wide x 22" deep and 11.5" high, .075" birch plywood. I am limited by height if 11.5 for putting the box in the trunk. Once in the trunk I should be able to add a baffle (to raise the total height some more) in case I decide to replace the dual 8's with a single 12. I believe max side I can go is 34" and depth be 24". If depth is 24 then subs will have to be mounted along the depth face (which could be good as they would be closer to 1/3 down the line).

Please let me know in case you have any more questions for me.

Thanks a lot for reading and hope you have a good day ahead.

Edit
Attaching Hornresp export for dualhds208

Hi,

I'm trying to identify the UTC transformers used in the Universal Audio 175B.
So far I've come across this references but can't find more info on the T3 UTC PA-6003, anyone can help ?

T1 : UTC 0-1 : Low Z to grid (Pri : 50, 200/250, 500/600 Ohms // Sec : 50 KOhms)
T2 : UTC A-19 : Plate to PP grids (Pri : 15 kOhms // Sec : 80 kOhms (split) )
T3 : UTC PA-6003 : ( Custom winded by UTC for UA's 17(5/6/7) Limiting Amps ? )

Thanks for your help !

PS: I'm looking at UTC 1963 catalog

Hi there, I'm just another audio enthusiast looking to learn from the community. For posting approval, thanks.

I am an engineer specialized in factory (paper mill) maintenance. I have some electronics design background but my abilities are rusted and almost two and half decades old. I am new in hi-fi. Looking for technical replies from experts to my questions in this area. Have a nice forum.

Hello all,

I wanted to introduce myself and an ongoing project I have, well really a whole series of projects. As a way to learn a bunch of techniques related to audio engineering, purely as a hobby to stop brain rot, I have a pair of active speakers from the 1980’s, Meridian M30, which I am hoping to have a long-term experiment with. Fortunately I have the schematics for the crossovers and amps.

As a summary, highlights of these speakers are:

• KEF T33, 180DC15 drive unit pair, both 4ohm
• Active crossover based on many 5532s with some interesting signal shaping
• 2x70W power amps based on BD139/140, MJ15003/4 output pairs
• Regulated 15v power supply using 7815/7915

So far I have done the following “basic hygiene” tasks

• Replaced all the electrolytic caps (which removed a punishing crack on power up)
• Replaced the ferrofluid in the tweeters
• Captured the schematics into LTspice (at least 98% of it)
• Taken some acoustic measurements with REW/UMIK-1 that seemed to correlate with the crossover design, including a whopping dip designed into the presence region

My aim in this project is to understand by practical activity the effect of changes in electronic/mechanical design, hopefully to produce an “improved” version by the end. Although not a “cost no object” project, I am fully expecting it to become a bit of a money pit over time! At some point this will include getting a 'scope but that's a fairly major jump.

So, I have a few questions I wanted to raise.

• I was planning to document the project as I went. In terms of diyAudio etiquette, should I put this all in a single thread, updating the first entry as I go, or should it go in a series of threads?
• As it includes parts of line level, power amp and speaker (drives, cabinet), should I raise questions for each in their own forum areas?
• The schematics are reasonably easy to obtain online in PDF form, but I think I will only provide snippets from the full diagram publicly. Does this fit with the forum’s IP/copyright approach
• If you were crazy enough to try this yourself, in what order would you consider review/upgrade? Following a source-first approach my thoughts would be to look at power supply, then crossover, then power amp.
• Is the T33 tweeter a bit long in the tooth nowadays and could be improved?
• Are there more modern output devices that could produce interesting changes or are there other places to start.
• I replaced the electrolytic caps and the remainder are mostly polypropylene and a couple of tantalum ones. Would these normally be replaced too? Any other components that would tend to age and should be replaced as a matter of course?

Thanks for any support you can give!

Ian

Hello,
i got my hands on a CP-1 from MAS Metaxas.
never heard of it? me neither,



its so rare, you wont even find it on the internet, except in 2 (now 4..5) places.
seems to be from the 80s, probably 86.. 87 or so.
in their "how it all began story" pdf mentioned on page 7 http://www.metaxas.com/HIFI_2015.pdf
on some site mentioning it in "DAS OHR" magazine and the 2 or 3 posts i made.

i found a picture of a later revision, still CP-1 but industrially made PCB instead of self-etched. in low res, due to original got deleted and using google image cache.






it has a technical problem i cant seem to fix, atleast not easily.
one channel loudly pops and crackles when its cold, after warming up it goes away.

im listening to it since an hour now, and havent heard a single crack / noise anymore.



the popping is so loud, it basically swings almost from rail to rail. and then it starts to create noise after settling. hooking it up directly to a high power amp will likely damage it or the speakers attached.








its not mechanical issue, i tapped and hammered on it, but couldnt reproduce it, it comes and goes on its own.


i replaced all capacitors with new panasonic (FC & FC-A) ones and a x-class foil cap in the supply and renewed the thermal compound, but the issue still persist.
(attached pictures show stats before replacing components.)


i narrowed it down to be one of the potted Gain cells which control the output gain. before that, everything seems to work even the phono stage.

The signal before that is clean and the powersupply doesnt glitch when it happens. so it must come from one of the gain cells.


i confirmed that by swapping left and right, and the issues moved with it.
(its the one with the ripped off sticker in the attached pictures)




The potting doesnt look like epoxy, more like very hard tar.. bakelite? shellac? cracked corners look like glass / obsidian, its very hard,

i have no clue.
i tried melting it with a soldering iron, well it stinks badly but didnt get soft.




The faulty cell is 2°C hotter after a hour of listening, and as i mentioned, at this temperature the crackling and popping is gone.
(ignore the hotspot top left, its the resistors for the front LED; they are both dropping 46V no idea why one is hotter, powersupply is perfectly 23.8V -24.1V on both channels.)

i suspect it to be a discrete opamp to be inside, but i havent got a xray machine (yet 😛)

it has 5 connections, +-24V, signal in and out and capacitor feedback of some sort. (2 tantalums in series, in paralell with a foil cap)


also since theres no info about it anywhere, its very unlikely to find a schematic.


anyone got a idea what to do?
can anyone can tell me something about this rare unit?



rebuilding both cells either descrete or with opamps is the last resort.

its definately not something to throw away.



i also contacted the inventor, kostas metaxas if he can tell me more about this unit but havent heard from him yet.

the sale in the link below a kit consisting of 3 pcbs for the construction of the final stage of the Nad 3020.
https://www.ebay.it/itm/275392868133

Hello Experts, I have a question regarding the replacement of transistors in my AudioAnalyse A9 amplifier (Pure Class A, 50WPC). This amp delivers excellent sound quality, which I really enjoy (sweet, calm, with a wide soundstage). Unfortunately, two MJ15015 transistors have shorted, and after reviewing the schematic, my technician friend raised a few concerns and suggestions. I would appreciate your expert opinion on the following:

1. Why are the same transistors (MJ15015/MJ15016) used both in the output and driver stages?
2. Can we replace the MJ15015/MJ15016 transistors with MJ21193/MJ21194 across the board?
3. Considering the different HFE values (20 vs. 75) and Ft ratings (1MHz vs. 4MHz), would this be an upgrade or potentially cause issues?
4. If MJ21193/MJ21194 can be used in the output stage, should the driver stage transistors also be replaced?
5. Or should we stay with the original value transistors?

Your guidance would be greatly appreciated. Thank you!

(Schematic attached)

Hello, I’m looking at trying the Aciustic Reality series crossover. I’ve never laid one out though. Looks like just three components. Can anyone help me?

Hi,

I'm new to diy audio and have no experience in modifying amps. Few months ago I bought a Bewitch KT88 on ebay and so far I like it a lot, one of the reasons I bought the Bewitch was the positive review on the Lampizator website (Bewitch).
He also made a recommendation on some mods. I'm planning to follow his mods, but recently I heard from some people that the Lampizator mods might not be as good as he claims.
Can somebody give me some information about this mod?

http://lampizator.eu/AMPLIFIERS/CHINA/bewitch 6550/IMG_5577.jpg

There is a circuit diagram simulation error. I don't know why. The first time I used simulation software, I uploaded the file. I hope my friend can help me have a look. The optocoupling uses 4N35, and I use PC817C instead.

After months of getting information of this place, i finally decided, to join and become part of the community.
Being a musician and teacher of technical crafts, one doesn't have to think far to try to build the stuff you need by yourself. Starting with simple audio cables, passive audio splitters, adapters and so on, I got my hands into building more and more complex projects, including power amplifiers and parts of my PA. Looking forward to share some projects and learn from the more expierienced around here.

cheers

Hitachi's advancements in amplifier design, particularly through the use of power MOSFETs, have significantly impacted the audio industry. Their balanced voltage amplification stage design, outlined in their application note, transformed the way amplifiers were built, enhancing performance, efficiency, and sound quality.



In the early days, bipolar transistors were the dominant components in amplifier circuits. They were valued for their high gain and efficiency, but as the demand for higher fidelity in audio systems grew, the limitations of bipolar transistors became more apparent. They required higher driving power, were prone to distortion, and exhibited significant phase issues at higher frequencies. Recognizing these challenges, Hitachi was one of the first companies to explore the potential of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) for high-output amplifier designs.

Hitachi engineers initially worked with small signal MOSFETs used in TV tuners and similar high-frequency applications. Through years of refinement, they adapted this technology to create high-power MOSFETs, which offered significant improvements over traditional bipolar transistors. This led to the development of amplifier circuits that took full advantage of MOSFET characteristics, particularly through the balanced voltage amplification stage.

According to the application note, power MOSFETs offer several distinct advantages over bipolar transistors, making them ideal for high-performance audio amplifiers. Power MOSFETs are voltage-controlled devices, which means they require significantly less driving power compared to bipolar transistors. Unlike bipolar transistors, MOSFETs are free from current concentration, making them far more resistant to damage from electrical stress or thermal runaway. The absence of carrier storage effect in MOSFETs enables a high switching speed and excellent frequency response.

While power MOSFETs brought clear advantages, their inherent distortion (approximately 20 dB higher than bipolar transistors) required Hitachi engineers to rethink the design of the voltage amplification stage. To mitigate this distortion, they developed a balanced voltage amplification stage, which allowed them to increase the open-loop gain and apply larger amounts of negative feedback—key to reducing distortion without compromising bandwidth.



The balanced voltage amplification stage works by taking signals from both the inverting and non-inverting outputs of the long tail pair input stage, a critical design decision that maximizes the amplifier’s ability to reject common-mode noise and increase overall gain. By amplifying both signal paths symmetrically, Hitachi’s engineers were able to apply larger amounts of negative feedback over a wide frequency range, effectively reducing distortion.

In bipolar transistor designs, a Darlington connection is often used to increase bandwidth. However, this two-stage emitter follower configuration introduces significant phase distortion, which complicates the application of negative feedback. To compensate for this, phase compensation circuits are required, which can further degrade performance by sacrificing gain and limiting the overall frequency response.

Power MOSFETs, on the other hand, offer a significant advantage. With a single MOSFET source follower, large amounts of negative feedback can be applied over a broad frequency range without the same phase issues. This allows for greater stability and lower distortion, particularly at high frequencies. Furthermore, the driver stage of a MOSFET does not require a conventional class B driver, which reduces the number of components and simplifies the amplifier design.

From the application note on design of voltage amplifier stage:
"A power MOS FET can be used with a low driving power. Fundamentally, only the power for charging and discharging the gate-to-source capacitance is needed to the output stage, so that no class B driver stage is required. The driving power varies with input frequency. At 100 W output and 10 kHz frequency it would be about 10 mW. Therefore, an output stage power MOS FET can be driven directly from a class A predriver (voltage amplifier stage) used in a bipolar transistor amplifier. By eliminating the class B driver, the number of components can be reduced, and impairing the amplifier's performance caused by the driver itself can be avoided. Further, the number of poles for transfer function (open loop gain vs. frequency characteristics) decrease, and the stagger can easily be increased. Consequently, the stability against oscillation is improved. Transistors for the voltage amplifier stage are required to have a high voltage durability, low Cob and high fT. Here the 2SD756A/2SB716A developed especially for power MOS FETs are used. With the NPN differential amplifier and PNP constant current load, high gain and low distortion characteristics were obtained. The class A stage bias current is set as 10 mA. When bias current is lacking, sufficient power to drive a power MOS FET at high frequency cannot be supplied, and distortion would worsen. The drain current temperature coefficient of a power MOS FET undergoes a reversal of polarity at around ID = 100 mA and temperature compensation in the large current region will be unnecessary. Hence, the bias circuit for a power MOS FET is vastly simplified because only one semifixed resistor (1 kOhm) for setting idling current will suffice. For the input stage, a stable differential amplifier circuit was formed by using the high-voltage, low-noise transistor 2SA872, which is known for its high performance in improving the S/N ratio. Bias current is set as 0.5 mA."

Inspired by Hitachi’s innovations, I have decided to create an op-amp design based on the differential voltage amplification stage. This design leverages the balanced approach to drive the output stage of the op-amp, optimized for small signal processing. Since typical op-amp loads are as low as 600 ohms, compared to the 4-ohm loads found in power amplifiers, the current-driving requirements are much lower.

Opamp specs:
THD (G=+1, 600R, Vin=1.41Vrms, 1kHz): 0.000007% or -143dB
THD (G=+1, 600R, Vin=8.5Vrms, 1kHz): 0.000054% or -125dB

BW (G=1): 10MHz
Noise: 1.95 nV/Hz1/2
Voffset: 0.02mA
AOL (100Hz): 110dB
AOL (20kHz): 80dB

Attached you can find Hitachi app note and opamp design in LTSpice simulation.

Hello,
I search the schematic diagram to the Kove AD2400 amp, or the IC111 reference.
Thanks

Hello everyone!

Today I received 2 DeForest DL5 tubes.

I swapped out a Cunningham CX301-A Harrison Plant, long glass bulb in my amp for the DL5 (120H choke loaded , 120V anode ,ballery biased with -8V on the grid.)

Sounds wonderful! Better than the 01A in many respects. I will go back to the O1A and do more comparisons to see if I can decide on a favorite.

It is (~mildy) microphonic , a tad more than the 01A.

I highly recommend this tube😃

Here are some pics

i have been working on this project for a few days now and i managed to get to this, but there are a few things wrong with it.
im thinking about adding another gain stage and improving the constant current sink.

Hello all,

After 15 years of collecting and tinkering with CD-players I decided to sell some of my TDA1541A DAC collection. I personally desoldered (with the proper tools) all of these from CD-players, CDV players and digital tuners. The pins are all straight and very clean, no bent or damaged pins. Will fit sockets fine (even the machined gold plated ones). They have been stored in anti-static materials for quite some time, it's time to let these make some music!

Available are:
none left

In my opinion all the A types sound very alike. Especially with some form of DEM locking they do not differ all that much from my S1 chip. It is debatable whether the R1 version is worse or better than the plain A. Rumours say the R version is for 'Relaxed' specification but the datasheet states it is slightly better than a normal A. The CDP227ESD from sony uses it, so it must not be worse I suppose.
The non-A cannot be locked by DEM, or at least not without some tricks...

All chips are in good working order and have been stored in anti-static packaging.
Fixed price of 50 euros each for an A type and 40 for the non-A. Payment through PayPal, payment cost and shipping is yours. I can ship anywhere but would prefer within the EU.

I can guarantee these chips are good working genuine Philips parts, however I cannot guarantee the working in your project, so no warranty or money back. They all work fine in my projects, but I hope you understand.

I suspect there will be some interest in this, I'll sell to the first person who messages. If there are none left, I'm sorry in advance. I have 20+ CD-players still that have these, they will probably end up for sale too since I'm clearing out the shop somewhat.

Please state your specific interest based on row nr (1 thru 9) and column (1 thru 3).

Best regards
Joris

Hello, I'm a bassist from Brazil who loves some diy solutions for the music demands. I don't have much electronics knowledge, so at this moment I'm seeking some advice for a line level booster

Hi, I’m Navid. I’m passionate about pure stereo and analog audio, and upgrading my audio system is one of my favorite hobbies.

HI all,

Here I sit, staring at a Marantz 2245...Without a balance pot.
OK. It has a balance pot, but it's not connected.
Don't bother to tell me how I screwed up, because I didn't make this mess.

I have a schematic, and if I have to work this out I will, but maybe somebody knows what goes where. Maybe a hand written note from long ago.

Appreciate the help!

From 2004 to 2014 i just used what experts said is best. However the more time i spend with particular chips in difeent projest tho more common sonic features common to chip become clear.

So in short-

DIR-

CS8412 double powersuply) is good DIR
CS8414(double power suply) is almost as good as CS8412
DIR9001 Something sonicaly not right about this chip. Edgy,shouty mids and "PRO" sound.
WM8804 much better than DIR9001, but lacks musicality of CS8412. I cant Hear diferencies I2s vs wm8804 in blind test-its so good technicaly.
AK4413- tought choice between it and cs8414.



DF-
SM5803- quite nice, punchy and dynamycs( including 4x OS mode)

SM5813 suprisingly quite nice(as technicaly it should not be that way) sonicaly NOT IDENTICAL to SM5803(smoother)

SM5842- too smooth with its generation dac chips (PCM63), also need carefull capacitor selection to sound clear and with sharper projection,otherwise muddy and too smooth, velvety sound.

PMD100- best widely available and widely used DF (with condition of double PS and reclocking and dither mode 4). no coloration, sound is interesting and inviting, with enought drama to keep you near audio equipment for hours.

PMD200 (real ones) best non OEM available chip,period.

DXF6001/DXF7001- one of the best OEM filter- sharp and musical at the same time. Hughely better than PMD100( especialy with single PS andin hardware mode)

DF1704- it have only one bonus- midrange texture is quite palpable. but bright, tent sound technicaly with all regulators and capacitors(best combiantion to amke it sound less dry and less" hi-fi" -old motorola 7805 and chemi-con AWJ capaitors)

for many years i saw upgrade kits from PMD100 to df1704. sure, in short listening comparision df1704 is more detailed, impressive. but once installed a reduced time of listenting music n hours can be expected. in high end system its clear downgrade comparing to pmd100

DXF7001 and pmd200both capable of 192kh) remains best digital filter (Wadia, Theta DSP filters is not included as I had no ability swap them to toher in same conditions)


Dac chips
UA20400A voltage mode units- smooth musical and always washed out.especialy with tube output (most of nits used tubed outputs for this chip)
UA20400A current output mode units - sharper more transparent. already very nice. still its matter of taste but its not the best R2r dac chip IMHO.


PCM56p-k clean, neutral, fast its like AD1862 with less bass.
PCM63p-k silky, increased midrange texture, requires carefull capacitors and DF selection not so sound soft. I consider this dac chip best but this dac chip best avoided in DIY as its very easy to spoil sound(same goes with sm5842)
PCM1702p-k a sonics combo of pcm56 and pcm63( insipte it should sound simialr to pcm1704)
PCM1704p-k midrange texture reduced comapring to pcm1702(and much more than pcm63) but hights is more refined, extended than pcm63 (and also than pcm1702)

AD1864N-K very clear and transparent and modern sounding dac chips. If i would not knew I would say its quite new sound.

AD1865N-k simialr to sound but worse(!) than 1864n-k could be production year issues, not sure.

AD1853- always musshy a bit compressed closed in mids but pseudo musical just like Elna Silmic MK1 capacitors or OPA2132/34.

PCM1794a- reminds PCM1704 in some ways. refined in i hights, also good dynamycs without being shouty-stays calm.

AKM4495- even wore than AD1853. AKM4499 less mooth more neutral
CS4398- very extended airy hights and large soundstage, but very synthetical sounding (even with audiophile type of outputs)

those are finding of same chips in modular contructions( where part can be easily swaped. in case pmd200/dxf7001, and pmd100/dxf6001 no swaping but swithing chips in same pcb A/B)



its subjective opinion, fortunately no measurements were madeto confirm this and no animals or plants were harmed during this comaparision tests. hope it helps to someone choose their own chips.

sorry for errors, typing fast and with small keyboard laptop.

Hello,
I'm looking to buy 4 pieces of 6HD5 or 6HJ5 tubes if anyone would care to part with them. So far I've found 3 places online
that will take money only to inform you a backorder or unobtainium situation exists after the fact. I did manage to find 4
that are coming by post but would like to have a backup set if these are that hard to find.

On another note, I found a few tubes down the road from me in a box that said 'working radio tubes'. I tried the one tube of the bunch
that I can use (Sylvania 6V6GT) and it did in fact work well. The rest are here if anyone can use them with no guarantees.

1x Westinghouse 5Y3GT
1x 6SQ7GT no brand but Made in Canada
1x Rogers Canada Magic Eye (can't make out any real numbering)
1x Rogers Canada 6SQ7
1x Rogers Canada 6SG7
1x Sylvania 6SK7
1x Rogers Canada 6SA7 (GT?)
A couple old chrome rings taken from a chassis I believe and an old tiny brass Phillips pin

Now that I finally have some proper progress made on these, I want to share photos of the build as it continues toward completion. This is my first set of horn speakers, with past builds being 2- and 2.5-ways, as well as a 13Hz F3 ported subwoofer. The 2.5-ways are some Zaph ZRTs that I built almost a decade ago, and they have been so good that I have not really felt a need to build more speakers! They don't really even need the sub (which was built to augment my original self-designed Aurasound 2-ways), and I have it crossed over at 35Hz with my DCX2496 since the ZRTs are solid down to about there. ANYWAY, I got the itch again, and since many people rave about the sound produced by horns, I wanted to give them a go myself. My experience has certainly been that they have vastly better transient response than ported enclosures for snare drums and things like that. Who knows...maybe these FHXLs will take the place of the ZRTs!

As far as the driver configuration, I sourced some new Alpair 10p's from KJF Audio. Shipping to the US hurt a lot, but after I digitized and plotted various MarkAudio and Fostex drivers against one another, the 10p's looked like they would provide the more balanced high frequency response that I prefer. As part of the same order, I also got the recommended damping sheet and stuffing materials.

So, first off I donated to this fine forum and got my copy of the build plans. From there, I created my own model in SketchUp using the actual thickness of the ply sheet stock that I purchased. It came out to 18.4mm, and tiny adjustments were made here and there to both maintain the internal dimensions and ensure that everything fit nicely line-to-line.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_023.png


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_024.png



The plywood is maple-veneered Europly, and I will be accenting the baffle + top with some "mahogany." In reality, it is Light Red Meranti, which many stores call mahogany, but it is in fact not. Still, it is an attractive species and it also does not break the bank. A local supplier has a fantastic selection of fine plywoods, and I was lucky enough to catch this 13-ply birch material while it was a bit cheaper than usual. The "mahogany" was just some 1x12 stock from a local Home Depot. While I usually don't buy wood for anything more serious than a shed from that place, they happened to have some boards which were reasonably straight and not smashed up, so I grabbed the best looking one.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_001.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_002.jpg



At one point, I took some scrap cardboard and made a mock-up of the FHXL to play around with placement ideas and get a general plan for where I would be able to experiment with them. This was prior to buying the wood...gotta make sure they can actually go somewhere! It has since become a hideout for one of my cats.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_003.jpg



Next, I cut out all of the smaller panels to their overall sizes. From there, I added the required angles to the ends.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_004.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_005.jpg



My preferred way to set up angles is the same way that I tune up the saw...a nice digital inclinometer on a tool plate mounted to the arbor. I had bought this Unisaw used many years ago and it was very out of tune, so I had to invest a bit in dial indicators and other items to get everything properly square. Those of you who have used an improperly tuned table saw know how unpleasant (and DANGEROUS) it can be. The other key for ease & safety of use, in my opinion, is to regularly apply some floor wax (I like Johnson Paste Wax) to the top surfaces so that material moves smoothly and with minimal "grunt". The less force you need to move the workpiece, the less chance there is of you shoving a hand into the blade.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_006.jpg



The large side panels were the most work, as I am sure that other FHXL builders have found. I wanted a perfect circular arc, so after marking things up and making some measurements, I decided to make a large format circle jig for my router and then used it to cut a guide piece from some old ply scrap.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_007.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_008.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_009.jpg



For the first side panel, I routed the arc in bits and pieces, leaving as many clamps in place as possible and removing them as needed to pass the router. Things have a tendency to wiggle and slip if you let them...so don't let them!

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_010.jpg



Personally, I am a big fan of down-cutting spiral bits for things like this. If you have your "A" side on top, there is zero chance of veneer tear-out, and if you have the bottom clamped against something, you won't tear there either. It is also nice to have the chips shoot away from your face. Check out Whiteside Machine Company router bits. They are not inexpensive, but they are SHARP and I have gotten many more hours of useful life from them than cheap bits (making the actual cost negligibly different).

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_011.jpg



The first side panel's arc came out beautifully! As with all things, the seven P's of life should be minded (proper prior planning prevents p*ss poor performance). As far as the remaining straight sides were concerned, I also used the router and flush trim bit. Straight scraps were carefully aligned with markings for the straight sides and used as guides. Forget trying to cross-cut the angles on the saw...it is far easier to mark-up and clamp guide pieces very precisely.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_012.jpg



Once I had that first side done nearly perfectly, it was then used as my "golden" template for cutting the remaining three. Measure thrice, cut once, as the saying goes (measure half a dozen times is also something I am a fan of).

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_014.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_013.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_015.jpg



And with that, the sides were done and approximately identical!

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_016.jpg



The next challenge was to cut the mahogany panels for the baffles and tops. I wanted perfect miter joints, so I used some scrap ply to trial-and-error the exact angle that was needed to get a clean miter line. In theory, setting the blade to a 42.5° angle was ideal, but reality often demands a bit of tweaking to have things work out. Once the angle was set properly, I ran my oversized mahogany panels through. They have a bit of cupping in them, up to 1mm in a couple of spots, so the joint didn't look perfect along the length when just sitting as shown. The angles came out perfect though. These boards started out 19mm thick, and I planed them down to 10mm both to remove surface damage, and to be the same thickness as the Alpair 10p basket frames to get a flush mount.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_017.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_018.jpg



Since the miter cuts were set in stone now, I needed to work backwards a little to get the underlying ply panels placed correctly to produce a proper fit when everything is finally assembled. Lots of clamping, adjusting, re-clamping, re-adjusting, etc. Once the cupped boards were constrained up against the ply panels, the joint assumed the perfect profile that I had been aiming for.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_019.jpg


http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_020.jpg



With things clamped together, I needed a strategy to be able to separate them, apply glue, and reassemble them. To ensure proper re-alignment, I drove in some small nails to serve as little datum pins. The nails end about 3mm from the front face of the panels, so there was no cosmetic fallout.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_021.jpg



It has been said that if you can count how many clamps you have, you don't have enough. As I found, I think that I need more clamps. This took all but two of the ones I had in my shop! The glue-ups are sitting and drying now, and should be coming free of the clamps tomorrow after I get home from work. My fingers are crossed that my little nails-as-datums trick actually worked and the miter joints still fit together properly. I've done enough woodworking over the last decade to know that even the best-laid plans can end up failing, so I am prepared to see imperfect joints if things do not work out as planned.

http://www.e30tuner.com/speakerbuilding/images/fhxl_2021/fhxl_022.jpg

Steve,

The Metronomes are also quite interesting.... and not really a TQWT (in a strict sense). I can't remember whether we discussed it here or on the full-range forum. Because it tapers in both directions the taper is not linear, but quadratic. It does make for a very elegant looking speaker.... have you posted drawings anywhere?

dave

PS: always nice to see the "Made on a Mac"

I have a strange behavior with a pioneer DJM600 mixer.
Channels 1-2-4 operate logarithmically. Channel 3 behaves linearly.
Changed all the faders (as I also have another mixer for a donor, logarithmic not linear), trim, bass, mid, treble, fresh solder everywhere.
The strange thing now, the signals go through TC and end up in VCA, the signal path to the potentiometers is the same as the level in all channels.
From there on the thing breaks down, I tried to put resistors 2.7kΩ to fader in the 3rd channel (maybe I ran into a faulty 10kΩ fader alps component, I don't think for sure but you never know, ive try faders from other channel with same results), but that's how it cuts (drops level) and signal from the entrance probably because of TC.
Because I am in the process of changing the TCs (I have a genuine toshiba) it seems extreme to me because I think they either work or they don't work, I don't think and I don't know that linear-logarithmic behavior changes.
Keep in mind that the channel outputs a clear signal and when fully raised the potentiometer gives the same level as the rest.
So does the VCA or the TCs justify such behavior since the signals (1-2 and 3-4) go there in pairs?
PS mute transistors etc I've checked them, I don't have an smd to change them but it doesn't make sense since they measure correctly and the behavior of the channel doesn't change with or without them and the ground is where it should be. As are the supply voltages listed in the schematic.

Sorry for my bad english, cheersm have a nice day.

Hi, my name is Fabian, I'm brand new to this hobby, I recently repaired my dads old dual turntable from 1991, and I got out his old Sony TA-F170 amp and some mission speakers from the time. I'm really enjoying listening to vinyl and have brought some new records to play on it. I repaired the turntable intuitively, as I know a good amount about mechanics but electronics I know quite little about. I really want to get at least a little into this hobby, but I have no idea what I'm doing when it comes to amps, as well as not having the necessary tools such as contact cleaner. It is the amp that is giving me problems, but I will post that on a separate thread. My main area of interest at the moment is engines, but its fun having vinyl as a side project. I also love fixing things no-matter what it is, I find it very satisfying to see something work after having a tinker. So that's me!

Hi folks, Douglas Blake told me there was an interest here in a DIY version of my Null Tester device that compares two signal wires to see if they pass audio differently. Doug asked me if I'd consider making the tester available as a kit, but that would be more work for me than I'm willing to do. One reason is there are two minor problems with the circuit that need to be fixed. Another is I'm not convinced enough people would want to build (or buy) a device that can test only wires to justify the effort.

When I told Doug I'd be glad to hand this off to someone else to complete the last 5 percent needed, he asked me to post here. Doug said there are plenty of people here who are knowledgeable enough to fix the remaining problems. One is the meter VU driver needs to be re-worked to be more accurate. Another is for some reason the 2 watt LM380 output amplifier clips at too low a level, and I never got around to figuring out why. So:

Is anyone here interested in taking over this project and turning it into either a DIY kit of parts or a complete commercial project? I'd be glad to split any potential profits 50-50 if it actually made a profit! 😀

Hey guys, Evan here. Officially joining as a member after many years of reading the forums.

Just attended the Burning Amp festival 2024 (my first one!) over the weekend and it was great to meet some of you folks in person and see/hear some of your projects!

I'm a design engineer @Tymphany/Peerless responsible for many of our automotive endeavors and like many of you I'm a huge tinkerer in my spare time.

Looking forward to spending more time on here in the future.

Cheers,
Evan

I came across a stash of PCM56 chips years ago and am looking to build a modern DAC around them. The analog side is straightforward enough, but after reading many threads about how manage the digital connections, I'm hoping to get a quick sanity check from the community before getting too deep into to board layout.

The goal is to connect an Amanero Combo384 to four PCM56s for hardware balanced analog outputs, similar to the Parasound DAC1600, Adcom GDA-700, Pass D1, etc. I'll be using the Amanero clock with settings recommended by Domenico at Amanero, but I'm open to doing things differently if anyone has suggestions to improve the jitter performance. I'm concerned the isolator and gates will introduce jitter but am not sure if it's possible to slave the Amanero to a clock on the DAC.

Here's the glue logic I plan on using. Does this look like it'll work? Would anyone do it differently?

The short answer is: The method also attunate harmonics with similar level.

I have looked at a a ADAU DSP and a CS42448 codec card. It has several DACs. I have tried to use them differential and used BB INA2137 as a line receivers. The INA is similar to SSM2141 but -6dB gain
The balancing works great.
But it is so good that the measured distortion is mostly the distortion of the ADC of the soundcard.
Then I put another line receiver on two other DACS of the CS42448 and get another single ended signal with the same amplitude and phase.
If i invert this signal and put both into a third line receiver, the fundamental is cancelled about 40 to 60dB, but the noise is still there and the remaining harmonics is way lower than one channel straight into tha ADC. (eg, with or without muting of the cancelling signal)

This could be replicated with a line receiver, REW, stereo DAC and a cheap ADC.

But will the result be valid?
Is too much distortion cancelled out by the line receiver?
And is the load valid when the fundamental signal is cancelled out by an other source?
Napkin drawing

Example of ADAU graph in sigma studio

Hi folks!. I live in Long Island NY. I own 2 recently thoroughly restored Pioneer SX 1980, and 1280. The problem is no sound coming out of the AM section in both of them. On the other hand, it’s hard to find a reputable service technician up here in the NY/NJ area who’s very knowledgeable about repairing the tuning issue on these sets.

If there is any other Pioneer owners who have had this AM/FM issue before and knows anyone in the NY/NJ surrounding area please let me know. I’d be sincerely grateful. Good luck in all of your projects.

Greetings and Salutations,

I recently acquired a beautiful Onkyo M200. Unfortunately, it’s in pretty rough shape - the front glass is broken, and the PCBs were tampered with. The PCBs are in very poor condition etc.

I have basically repaired the electronics and confirmed it by replacing the bad components with good ones from one side and bypassing the protection circuit.

I was able to find substitutes for almost everything from KEC Semiconductor and ON Semiconductor, except for the 2SC1941 and its complementary device, the 2SA916. The KSC3503 and its complementary device would have been a good fit, but I haven’t been able to find original ones with the same grading from a reputable distributor. I’m located in Germany, by the way.

The closest transistor I could find was the BF723. The only issue is that there are no graphs for gain linearity, etc., and I don’t have a tool to plot them myself with a curve tracer. Other than that, it looks good, I suppose? HFE should be reasonably consistent due to its intended use, as suggested by the datasheet.

Are there any other transistors from a legitimate source that would be suitable? It doesn’t matter if they’re THT or SMD.

The NEC datasheet suggests the following:

• HFE @10V 1mA = min 50
• HFE @10V 10mA = min 90

I’m wondering if there’s a mistake in the datasheet, or am I misunderstanding something here?

Thanks in advance and best regards from Germany!

Hi!
Building a power supply for my audio preamp. The build is based on Rod Elliots ”Power Supply for Preamplifiers” using LM317 and LM337 but get noice/oscillaitons - 100kHz, 4.5mVpp and intermittent ~30Mhz, 2mVpp

How can I remove these 100kHz and 30 MHz oscillations?

/Anton

All my equipment uses balanced cable. Right now I have stuff that's sensibly priced but with a fair reputation. I'm about to rewire everything everywhere, including my balanced xlr cables and I am not shy with a soldering iron.

I have no problem buying cables that have the connectors already attached, nor is it a problem for me to solder bulk cable. I've been looking at some products that are OCC copper, silver plated and even solid fine silver wire but I'd like to keep the costs below $5 a foot.

Any recommendations?

Login to view embedded media
But it is in French! I have no idea what he is saying. Seems to be about pipe design & dispersion?

Anyone knows what he is talking about?
Anyone knows what document he is showing?

It's from about 1996. I think it cost £450, and was £100 more than the RCD 970 which was more popular and got better reviews in What HiFi and HiFi Choice.

The reason I ask is I've always wanted to buy one as I have a 970 and want to compare them. The used different DAC implementation architecture but the same chassis:

RCD970:
Phillips CDM-9 laser mechanism
TDA-1305 Continuous calibration DAC chipset - 16 times oversampling filter for 20-bit resolution followed by upsampling to the equivalent of 96-time oversampling. Signal then turned into a 5-bit PDM signal

RCD975:
Phillips CDM-9 laser mechanism
Dual differential time-aligned continuous calibration DAC chips. each D/C simultaneously processes both the positive and an inverted version of the same signal. The resulting analogue signals are then compared to each other, any conversion errors appear as differences in the two signals, which can then be cancelled out.


I got these descriptions from the Rotel website where they still have the old brochure: https://www.rotel.com/sites/default/files/product/infosheets/RCD970 Brochure.pdf

Incidentally the 950 and 970 appear to be pretty much the same in terms of DAC implementation, but the 950 didn't use the CDM-9 laser mechanism and didn't have a toroidal transformer and a few other components were probably less select.

The Rotel RCD975 sounds interesting though - did any other CD players of DACs do things that way?

Hi;

I am 1 guy with an awful lot of Electronic Components that I know would be of interest to members and had intended to post something in the Bizarre area but I am not allowed.
Is there anywhere on the site I can let other members know about a selection of the parts (from 30K different lines, from Diodes to Semiconductors) that I think could be of interest?
Such as old Texas, Newmarket and Mullard transistors. Sanyo, Hitachi, Semeleb Power Transistors, plus much much more..
All my parts are original 'old' but new stock in the UK but happy to ship anywhere either direct or through my EBAY store.

I did not want to break any rules hence this message.

Thanks for your time.

Kind Regards
Richard

I missed my Martin Logan Aeons and find box speakers hard to live with so I was browsing ebay for some used dipole speakers when I came across the Magneplanars.

I'd heard the name years ago but new nothing about them.

I found this Stereophile review

https://www.stereophile.com/floorloudspeakers/595/index.html

and decided to take a chance on the MG1.6i QRs from a busines seller. They arrived yesterday in their original packaging and were soon unpacked and left to acllimatise for an hour. At 64" tall and 19" wide, they dominate my modest lounge and were located 1m from the wall and 1.5m from the side walls, angled in slightly.

I knew my 35w PP valve amp wouldn't be happy driving the 4ohm power hungry load so I connected them to a Marantz PM6007 integrated amp using it's onboard AKM dac to convert the optical SPDIF output from my LG tv.

Theen i sat back, not knowing what to expect or even whether they would be defective but wow, memories of the Aeons came flooding back with their great transparency, accurate 3D sound stage, smooth frequency reponse and absence of exxcess treble or bass.

I was certainly hearing more than my Naim SBLs delivered, in particular, the ambience of the recording venue was very noticeable.

I think I have discovered a best kept secret......

After running down another problem on the driver board I had another component fail. On the schematic all it shows is U2. The part is a 8 leg ic, but the top is torched. Does anyone know the part number for that part?
John

Pair of Ale Moglia Gyrator boards build by Ale and used by me for short time in triode 26 line stage.The top mosfet is IXTP08N50D and the second is BSH111.
The capacitor is Amtrans Gold Black Aluminium oil foil 100nF.
Bouth boards working perfectly and were stored now for almost 4 years.
Price would be 160 euro including tracked shipping inside EU or best offer!
You can use this boards with many diferent old triodes like 26,01a,76,56.....and with some new one also.You can use the boards like gyrators or ccs,you can use
BSH111 output for low output impedance or normal anode output.This boards are designed for build a line stage,tube pre,phono amp or some other project,but of course limiting factor is max.input voltage and needed current. Good to up 50mA of bias current and up to 450V of B+ voltage!
For more info look on Bartola online site and projects that Ale meade with this boards.

Hmmm, what to say. The measurements speak for themselves. This 8" looks and measure really good. I plan it for the woofer in 3way, though I am really tempted to try 2way with WG first.
I was really curious to see how it performs so I did just quick set of indoor measurements.

Can these TX/RX like [DIT4192/DIR9001] do 24bit@96khz?
In many readings it is said that SPDIF only supports 20bit... but what about the AES standard?
Can someone explain?
I am designing an i2s I/O interface and I wanted to add support for SPDIF or AES if applicable, to have true 24bit.

regards.

Newbie post, so please be gentle! OK, I have titled this as a question but understand that it must be possible due to this item - https://www.tisburyaudio.co.uk/mini-passive-preamplifier.

Just to clarify:
1) This is just for a small second bedroom system, so not really wanting to push it too loud or spend silly money.
2) I need (well, would like) to use this to feed a small power amp via the attenuated output and a headphone amp via the unaffected output.

Unfortunately, being a bear of very little brain, I have yet to work out exactly how this is achieved. I have made a few straightforward passive volume controls in the past for various projects & initially thought that I could simply piggyback the input straight to an output (electrically, the equivalent of using a Y-cable splitter) but, of course, having assembled it all, turning the pot did affect this output, certainly towards the quieter end.

(Of course, I realise that I could add a switch to run one or t'other, but the Tisbury does not need this.)

Any help would be most welcomed & thanks in advance.

Tim