Hello all,
Would anyone be interested in a replacement amplifier board for the Pioneer SX-750?

As a design exercise I designed and built a PCB to replace the stock amplifier board with the aim of improving the less than stellar performance in as close to a "drop in" package as possible. As benchtested, the board has met my design goals.

• Slew rate is 15V/us into 8ohm at 40W which is fine for a 50W/ch amplifier.
• THD+N (1kHz, 50W, 8ohm) has improved by a factor of 20X from 0.082% to 0.0038%.
• Bias is maintained by a VBE multiplier rather than the original "rubber diode" STV4H.
• DC offset measured ~1mV using beta matched input transistors

I know there it not a huge demand (if any besides me!) for this board, but I thought I would float it out there if any other Pioneer fans have an interest.

Dear all,

Is it possible that NOS DA conversion is owned by some one like for instance Audio Note?
Is there a patent on this?

Would this apply also to private use or is it limited to the manufacturer of the complete DA converter.

Any insights on that would be welcomed, thanks!
Regards, Veeren

Hi,

I have a newby question which is confusing me here. I modeled the attached transformer, bridge rectifier, and load resistor in PSUD2 and it says the voltage across R1 should be 321 volts. I did not any filter caps yet.

So I bread boarded this circuit exactly as shown, applied my 230 volts transformer to the bridge rectifier, added a 100W load resistor I had of 4,191 ohms. But when I measure the voltage across R1 on the bread board I get only 204 volts? How could my circuit be so far off from the 321 volts PSUD2 says I should be getting? Am I measuring the voltage wrong?

Rick

Heya all, I'm Jonathan from northern Indiana. I am very new to DIY audio (and indeed, circuits of any sort). I have a pair of Grado SR80e headphones, and I have decided that, during this quarantine, I am going to learn a bit about basic circuit design and building, and then try a DIY headphone amp (of which I see a few projects out there).

Would you recommend any of the books seen here: 76 Best Circuit Design Books of All Time - BookAuthority

Or any of these (as they're free)?

Electronics Design 101

Electrical engineering | Science | Khan Academy

Other free books / websites?

I'm not opposed to buying anything, but if someone says, "Skip all that and use this website," then I'll proceed in that way.

Thanks, all!

Bought from TechDIY one pair, matched. No idea IDSS as he didnt write it on package.
I'll take offers via message
Have a ton of 2sk170 and lots of pairs and will take offers on pairs as well. I tested those on my M3 transistor tester. It does not give IDSS. They are BL.

Youd think I would have the 9240 also and maybe I do but I didnt find any. Just found these after rummaging around more today.
I dont know whats a fair deal on these and cant recall what I paid. Lets guess at $60 per sextuplet. I was thinking $80 but 60 is probably good for us both.
I have two sets

Hey everyone!

I was given an NEC CD-705 player that won't read discs. It tries to read the disc, spins it around for a while but then spits it right back out. Does it with every disc. I've tried newer and older discs, originals and CD-Rs, high and low reflectivity but this guy's having none of it.

Took the lid of and observed the action with no disc in. It uses a photo diode detector so it's easy to trick it into seeing a disk. The pickup moves to the front and backs up a little, motor runs, lens moves in and out, the pickup then drives forward, tries again, drives forward, tries again, etc... until it gives up and ejects the disk.

I tried cleaning the lens, re-capped the laser PSU board and tried adjusting the two trimmers on the laser PSU board but no luck. It's a 2nd gen player and uses a Toshiba OPH-32 pickup which is unfortunately no longer available. I don't know how strong the laser is but I don't remember it being visible to the naked eye. Looking at the laser with a camera, there is a blue-ish-purple laser dot visible but it's not super strong.

There doesn't seem to be a service manual available for this unit.

Anyone have any ideas? I work on a lot of professional and home audio equipment but I've not worked on many CD players apart from easy stuff like lens cleaning, belt replacement, etc...

How should I go about testing it? How should the RF, laser power, etc be checked?

It looks like a pretty nice unit and it's visually in immaculate condition, would make a great addition to my workshop hi-fi stack.

Here's a video of what it does:
YouTube

I have been following the site for hobby purposes for a long time. I want to make an amp for myself. I designed an amp according to the suggestions of those who do this job properly.
my problem is, saturation at 15V. After 6Vpp, harmonics rise.
what are your suggestions? what do i need to fix,

Hi,

I have an old active sub box with two 10 inch subs, that has a plate amp that has died. I'm trying to figure out if I can find an amp board and power supply that I could get working rather than replace the plate amp (because it's probably not worth spending a lot of money on).

It appears to have had a 200 watt plate amp. The speakers are both single coil, and they are wired in parallel. When I put a multimeter on the speaker wire with both speakers connected, I get an ohm reading of 4.

Ideally I would have liked something simple like a "AIYIMA TPA3116 Subwoofer Amplifier Board TPA3116D2 Audio Amplifiers 100W Bass Output DC12-24V" with a laptop power supply, however I think 100watts isn't going to be enough considering it used to have a 200 watt plate amp.
AIYIMA TPA3116 Subwoofer Amplifier Board TPA3116D2 Audio Amplifiers 100W Bass Output DC12 24V|subwoofer amplifier|subwoofer amplifier board|tpa3116 subwoofer - AliExpress

Can anyone recommend something similar with more power? I realize I probably wouldn't be able to use a laptop power supply for something with more power, so I'm open to other suggestions for power.

Would 2 of the above boards connected to the same laptop power supply work (1 to each driver)? Or would they each need their own power supply?

Greetings to all. I'm looking for advise from those that have modified these particular drivers if possible.
I have 2 pair of these drivers, plan to leave one pair stock and modify the other to compare how much can be done to improve their sound. Will be using them as a stand alone speaker system in 2ch up to moderate music levels, no sub ( but avail ), no tweeter ( although I do have a pair of Optimus Linaeum ET-6 tweeters @ my disposal).Mind you I have no test equipment, and a no to low budget to work with. I have the drivers plus 2 full sheets of 3/4" particle board, screws, glue, polyfill etc. to work with.
With that being said, how would one go about the simplest approach to achieve the best results possible? As to the drivers themselves ; Remove dust cap and replace with a phase plug, keep or remove whizzer cone, dampen basket, perhaps dampen the cone ( dope, felt ) etc.
Type of cabinets; sealed, ported or other? No open baffles or bookshelf type please. My limit size wise would be something along the lines of 36"h x 12"w x 12" d. Livingoom is 13' x 16' w/9' ceilings.
I do not expect audiophile grade results from these , just a nice, reasonably smooth sound. Any/all suggestions would be greatly appreciated as this would be better than shooting in the dark with my lack of experience and components/materials I have to work with.
Thank you.

Hello,

I am sorry if this has been covered in the forum. I tried to search for an answer to my predicament but couldn't find an answer.

I have a rather strange issues concerning half-wave rectifiers. I have two large 575A rectifiers (5v 10A filaments each) I would like to use. I also have two 0-10v 10A (pri. 230v) transformers.

I can wire the primaries in series and obtain 5v on the secondary windings, but then - and here comes my question - can I wire each separate transformer to each full wave rectifier? Is there a preferred method to connect the choke to start filtering?

I guess what I am asking is whether I can power each half-wave rectifier independently and if there is a way to obtain filtered DC from such an arrangement. Plate voltage will come from a hybrid configuration with two diodes and the two half wave rectifiers.

I know it's a weird arrangement but I really don't want to get a new transformer made and would be really happy if I could use what I've got!

Extra scenario

Ironic as it sounds I also have two 1.25-0-1.25 transformers rated 50VA each. They were designed for 866A tubes apparently.

If connected in series, the secondary wingdings should give me 2.5-1.25-0-1.25-2.5 voltage points (primary windings would be in parallel of course).

Only problem is that each transformer is rated 11A and effectively I would be drawing twice the recommended current from each 2.5v lead. I don't believe this is a safe approach.

Important detail: each set of transformers is made of identical transformers.

I trust that the collective wisdom of the forum will come to my rescue 🙂

Like the rest of my country I am under lockdown due to COVID so having something to concentrate on is a blessing right now.

Thank you

Hello,
Today i dropped an Elma selector switch after soldering so it broke.
I have a tube line preamp with an output transformer and before the AVC there needs be a selector switch with 2 or 3 positions.
I found a nice Cole 2 deck switch with 12 positions but there is no possibility to add a stop.
Can i just use 3 positions to switch between riaa phono preamp and one or two line level sources and leave the other positions just like they are not there?
I checked it is a non-shorting or break before make type.
Greetings, Eduard
P.s could putting two positions for each source in parallel be an advantage in signal levels are low and contact resistance important?

Hello to all,

I am working on audio divider using LME49720 Dual op amp. I am not experienced with making design dedicated to some op amp, but I guess there should be some resistor and at least one cap.

Any idea what resistors should be used? Or what should be added?

Thanks for help!

Milan

PS: I did some googling but some dividers has feedback resistor, some not... I am confused 😕

I've done this... and the same will be for R ch. as I want dedicate 1 dual op amp to one channel because of separation.


Datasheet: http://www.ti.com/lit/ds/symlink/lme49720.pdf

I probably dont have enough weight behind my suggestion, but I was wondering. As we have so many APEX builds on this forum, if its possible to have a separate section under "Amplifiers" for all the builds.

Like the "Tubes/Valves and the "Pass Labs" sections


Just a thought 🙂

Hi

First a small intro..

I have designed a tiny DAC based on AK4490 which is part of my small modular DAC design. I can tell (or open another thread) about the project later but here are photos to show what it is about. So the DAC itself is only 50x50mm. The boards are stackable with Input board, DAC, and balanced output board, and breakout and PSU board as base board.





I built the prototypes during holidays and everything is functional. At test bench the first THD figures I got out of it were not impressive so I have been playing with it this week to improve the numbers. However, I am still not close to the best results I have seen so I would be keen to hear experiences on how to improve THD+N. I know many have played with this IC and some have been meausring it as well. I know some designs have ended up in commercial products so I do not expect you to share all secrets but any tips are welcome. Likewise, I will share my experiments. The idea is that this board also ends up for sale; however, I will keep the schematic public and write about the development and results.

I have access to AP at work so I have the big boys' toys to play with.


Something I have found out so far:

• 5V line (goes to VDDR/L and VREFR/L) is a sensitive one; my initial THD at 0dBFS was -93dB and I saw weird sidelobes on FFT. Apparently the bench PSU providing this was not good enough, after changing to the PSU baseboard I got rid of those. I suspect VREFs are the more sensitive ones. Need to do more tests on this.
• Adding large capacitance on VREF improves THD+N significantly (as is known - although datasheet does not say it anymore!). However, my THD+N vs. frequency still shows elevated distortion at lower frequencies.
• In fact, VREF capacitance seem to matter the most, even removing other caps do not change performance much.
• I see THD+N sweet spot at around -6dBFS.
• Increasing VREF (I've only tried 6.2V as my caps were 6.3V) improves THD+N ratio slightly at lower signal levels, close to full-scale things get worse. THD+N level actually remains constant but ratio improves due to increased signal level. Obviously this improves SNR directly.
• Playing one channel at a time shows an improvement of around 2dB to stereo.

So I have got from -93 dB to -108dB (0dBFS), the latter with 2200uF on VREF, voltage kept at 5V. Obviously these have been ugly mods and it can be tricky to fit lots of capacitance on such a tiny board. I also have some layout changes I will do for next revision. I probably will also make a bigger board for experimenting but will see now what I can get out on that form factor.

The caps I have tried so far are basic bulk caps. I have ordered some polymer caps and will try when I get them.

Things I'd been keen on hearing experience on:

• Capacitor type/quality, capacitance seem to be key factors here but what about the type of cap, its ESR and so on?
• Separating VREFs from VDDs, separating channels?
• Separate regulators for VREFs and VDDs, having them locally close to the IC?
• Any specific layout tips?

I have checked AKM evaluation board (manual) in detail, and it seems a bit off if they have really got the numbers and figures on that.

And while I am open to all feedback, I am really after measured differences here.

----------

And finally some figures where I am now at:

Key figures:

• Full scale output level: 2Vrms
• THD+N at 0dBFS: -108dB
• SNR/DR: 119 dBA
• Crosstalk at 10kHz: around -130dB

THD+N ratio vs amplitude (I like dBs but forgot this to %), THD+N level vs amplitude, and THD+N vs frequency, and FFT 1k 0dBFS plots below.

I also put schematic. Basically on board I have 100n+100u on all supplies, except now in these mods I have soldered extra caps. And as a sidenote, output filter is not a limiting factor here, I have also measured directly from DAC output.

Lots of info, but thanks if you read and can help! 🙂

Hi, I have some Baby Huey electronic pcbs to sell. Prices are marked at a good discount already, but all offers considered. Shipping is not included. Shipped from Western Canada.

Image 1: BHEL34 pcb. I have 4pcbs at $5usd / pcb

Image 2: BHEL84 pcb. I have 2 of these at $5usd / pcb

Image 3: BH MK2 PS pcb. I have 4 of these at $5usd / pcb

PM me if interested.

Regards,

Myles

Hello to All,

I have a simple question, I think it is simple. 🙄

May I simply replace:

2SA1695 https://www.digikey.com/products/en?keywords=2sa1695
with
2SA2151 https://www.digikey.com/product-detail/en/sanken/2SA2151/2SA2151-ND/3929421

and

2SC4468 https://www.digikey.com/products/en?keywords=2sc4468
with
2SC6011 https://www.digikey.com/product-detail/en/sanken/2SC6011/2SC6011-ND/3929418

https://www.milanmedia.pro/assets/ax-10.pdf - Main power amp is on page 11.

I did notfind to many diferences. basically they match. Eg. Vce Saturation (Max) @ Ib, Ic, Current - Collector Cutoff (Max), DC Current Gain (hFE) (Min) @ Ic, Vce, both are 20MHz.

Just output cappacitance is different: 2SA1695 typ 400pf vs 2SA2151 450pf and 2SC4468 250typ pf vs 2SC6011 270pf, so I guess I should change somewhere some PP capacitor on the output, isn't so?

Thanks for an update!

Milan

Dear DIYers,

Just ordered an HA-PRO2 DIY kit as I'm planning it as a gift to my dad.

I would like to add a bluetooth module as well and a input selector DPDT switch to choose between line in and BT.

My question is: what is the best way to include a Bluetooth module in the system? How should I power it?

I have a normal 2X12V AC toroidal transformer but both secondaries will be connected to the power input of the amp (as I need to connect it as center tapped)ű. So how should I power the 5V DC BT module?

I'm thinking about to have a 12V-5V DC step down converter with its input wired to 1 of the secondaries and the other end to a 5V DC isolator but maybe this is not a good idea. Maybe it is even harmful to wire another board to a secondary which is already in use?

Or should I use a separate transformer hooked up to the same IEC as the main transformer?

Any tips would be very welcomed as I'm not a electrician nor an engineer.

Thanks,
G

Hey all - hope your all keeping safe .


Venturing into the world of diy Class D , have read loads and now getting to grips with my first DIY project .


Aim to drive 3 power hungry 4ohn speakers with as lowest noise floor as possible , so looking for great THD , im not one to drive my kit to reference levels



The TPA3255 took my fancy and the 3e variant which is available from Aliexpress seems forerunner, Any other recommendationsd on amp boards ?



Couple of questions ,


Looking for two modules one 2x260w and one at 480w (mono) in one case


I take it I will need two psu as most seem to be single output or is there any meanwell ones which can handle dual outputs to the above configuration.



And is there anything else I should be concerned with ?


I am familiar with class D as i run my B&W 802 off some bel canto ref 1000m mono's



Thanks in advance


G

......................

So I have been planning to build this microphone for a while.. It is the GIC G7 microphone from : http://www.gyraf.dk/gy_pd/g7/gic.htm. They use the transformer as described "the wrong way arround" to transform the 15K impedance of the EF86 to something more useable.

I dont see much mike talk here but my problem is in its roots general.
The transformer is simply too expensive or unobtainable from my country. I could buy something criminally overpriced from ebay, or go with a EDCOR transformer but their shipping is at least 3X the value of the part to my location. So I went with the decision "what the hell just try and wind one".

Unfortunately I have not yet gotten into building the thing but I have done some math on the transformer. The highest permeability core I can get locally would be 2700 (or AL=8700nH). So what I have worked out with a online calculator is that 135 turns would give me roughly 2H on a 13mm core with 0.1mm wire. The core would be RM tipe.

This would be the secondary which would be 600. Since I need a transformer with a ratio of 25 I now have to apply this to the turns ratio which is 3375(LOT OF TURNS BY HAND). With this many turns the primary tube side inductance would be 1200H.

That does not quite add up in my mind I just want to verify if that sounds right to other forum members and if possibly for any advice correct me on the matter of designing this transformer.

I did not quite like the result of my calculation so I wen to other manufacturers who have transformers (as an example TOROIDY with their toroidal output transformers) and as an example my EL34PP transformers I use are about 590H primary so with a little common sense it sounds just about believeable that my transformer would come out to be 1200H.

I could play arround with the wire thickness and eventually find the point where I use all the space of the bobbin but I dont think it would matter as long as the inductance of the primary side is the same the secondary will stay also the same. And I didnt account for layers of the wire aswell but with .1mm it shouldnt really matter.

I dont know really I am not sure I wonder whats the opinion of some more people onto this.

Technical data that I want to achieve:

Pri Z:15Kohm
Sec Z: 600ohm

Just to add the frequency bandwidth here I would expect this to perform in
30Hz up to 30Khz (the high end isnt all that critical as long as its above 22Khz)

I did something wrong here dont burn my house down please I am just a student in electronics and a wanderer in tube stuff. I can only make PCBs well.

For the people assuming: All I want is your opinion if it sound believeable. If you have any idea or advice to try I will gladly consider it and try it.

I was recently given a pair of these neat little speakers, LSR305 (original model). One has a failed amplifier board. Sadly, the replacement cost of the board is close to the cost of a new speaker.

Probably crazy, but I am thinking about modding them both to passive, adding DIY crossover networks and running them off a normal amplifier.

I would only want to do this if it actually might sound better than the original setup. Otherwise use as a mono PC speaker, and scrap the second.

Scrap or Mod?

Finished my FHXLs a couple weeks ago and today noticed a dent in one of the cones. Cat maybe but not sure.

I'm not as familiar with full range and the impact of dents and what coatings are used on the Alpair 10ps. I would say it's small, but you can clearly feel it.

Could the be worked out by pushing from the back? If so is there something I can use to help it hold back in shape?

Or, am i looking at a new driver? If it's a loss of performance I would lean towards replacing.

I recently finished a Rod Elliott P101 MOSFET amp project. Pics on the solid-state project pics #6636

After some listening and getting new speakers Troels Gravesen DTQWT-mkII, something was not right with the sound. Like some odd equaliser effect.

I took a guess at C1 the DC blocking input cap. I had gone with 10 micro f, Elna CE-BP 100v.

I removed that and linked the PCB, turned on. 110mV DC at speaker terms. OK for a quick test. Straight away sounds is normal. Weird EQ effect gone. In fact the sound was really good. Test done power down.

Quick look back at Rods site. 1mf mtk or 10mf caps for C1. Looking in my stores (card board box of bits) 1mf mtk cap. Solder that in. 25mV at speaker terms. But sound slightly down from no cap. Obviously running with no cap not an option. So any help on what caps sound good in this amp input line role?

Current cap would look like a Red Wima 63V.

Thanks

Well, since this has been in daily use for the last couple months I figured it was time to declare it a success, and post it up to show off 😎

Its a variation of my favorite topology, the unbypassed cathode voltage amp, step-network biased concertina, and garter bias. Very similar to my flea amplifier, with a few tweaks. I wanted to go for an all-noval design this time, so went with the wonderful and affordable 6N2P for the front end, and went with rather boring but effective values to set it up. Unbypassed cathode lowers gain and distortion, and the distortion there is will end up primarily 2H from past experimentation with this set of operating points. A little feedback to the cathode is a nice way to tighten everything up 😉

The output stage is where things get a little unusual. For the first time in a few years, I'm actually going with a pentode output stage😱. Since garter bias works so well I decided to try it out on here, and it works pretty damn well, even on pentodes that are reasonably matched. I went with the 6CW5/EL86 for this use, with a nod to trying out the 6P43P-E later on (I have 21 of them, may as well 😉 )

I went with the Antek AS-0505 power toroid for my output transformers, which works out to 4232 ohms, with both primaries and secondaries respectively in series (for the relevant maths, 115+115=230, 230/10=23, 23x23=529, 529x8 ohms=4232 ohms) which should give pretty good linearity for these affordable and lovely, overlooked tubes. I'm running them a little conservatively at 32mA per cathode, for about 9.2 watts of combined plate/screen dissipation, but will likely increase this soon now that I know this setup works well. Of the tubes on hand, I find the Polam EL86 to be particularly nice.

Interesting to note, that if you connected the secondaries in parallel, and used 4 ohm speakers, these transformers would work well for EL84 or 6V6/6P1P as well, showing a primary impedance of 8464 ohms. Some minor changes to the screen supply would be needed to give a higher range of voltage. Easy, add another zener in the string 🙂

For power, an Antek AS-1T230 - 100VA toroid gets rectified through a 1N4007 bridge, fed to a pair of IRF820 mosfet filters, one of which uses a string of five 1N5262 50 volt zeners, with a pot/resistor in series feedig the mosfet gate for adjustment range. This gives an effective way of setting the screen voltage. The output tubes get their plate supply straight from the first reservoir cap, and the additional unregulated but smoothed mosfet filter feeds the preamp stage.

All resistors are basic type stuff, concertina resistors matched, and the garter resistors are 10W non-inductive bulk lot wirewounds, selected to within a couple ohms of eachother. All coupling caps are siemens poly films. Most everything I had onhand other than a few power caps, but it's all basic grade stuff for the most part. Used some leftover hammered texture paint for the affordable 12x8x2.5" BUD industries aluminum chassis. I went ahead and sprung for a fancy swooky purple power button LED this time, though 🙂


How does it sound? Well, very, very nice, if I do say 😉

I'm not one for audiphool jargon, but compared to my flea amplifier it is noticeably different, owing to that pentode sound. Overall it is much more powerful, of course, but it's super clean and accurate, not too clinical or sterile. Sounds like a nice EL84 pentode amp, but with a little more mojo that one seems to find with low impedance tubes. This thing makes thunderous bass, and has a wonderful midrange/high end. Nice general-use amplifier.

Total iron cost, $34.50 power, $17.50x2 for output, plus $13.50 shipping, makes for $83 total. Not bad 😎


Pardon the terrible picture and sloppy schematics!

SOLD - FS: Modified EAR Phono PCB Set

I developed this layout combing the Thorsten and Romy the Cat mods into a single PCB with various options for components (i.e. electrolytic vs. film local stage decoupling caps), jumper selectable filament for 6N2P or 12AX7 12.6V or 6.3V. Silkscreen on both sides for tubes on top or bottom.

Power supply PCB is capacitor multiplier like the original with a regulated DC heater supply.

$30 shipped to CONUS (PM for other destinations)

Got two matched pr of the ASC Blue Line caps. Brand new, never used. 1200VDC. Four are on Ebay from another vendor in Europe @ 26.00/ each plus $ 13.00 shipping.
Offered @ $ 35.00/ mp plus shipping.
thanks for looking
Photos available on request

Using PSUDII to simulate the PSU I get an open window, I guess I need more PIV rated diodes but used all availables and always the same error.

I opened this thread for further discussion about my I2S input ES9023 + JG Filter Buffer boards.

Of course any general discussion about the detailed application (Cs, Rs, regs,...) of the ES9023 DAC chip is very welcome 😉

I'd like to start with my current findings after some first tests:

After initial setup of the board according to the actual "beta"BOM I did some first measurements (of course I also listened and really enjoyed music 😀). Like others reported before there is some noise arround 1.5MHz especially at the NEG pin which could be reduced by moving the 2.2µF MLCC directly to the pins of the DAC (on the board it is only a few mm away 😱). Furthermore I found some modulation from the music signal on the NEG pin! I tried different Elcaps (220µF Pana FC -> 470µF Pana FR with lower ESR -> 22µF Pana FR) and the lowest measured best (no listening test) so i'll probably stay with 22µF.

I remember some discussion about removing the charge pump cap and implementing external NEG voltage, however the discussion stopped and no one posted results. Did anyone test this and can report his findings?

I also measured GND noise at several positions on the board and found it to be quite clean. However my scope is quite old and not the most sensitive on earth (5mV).

Another point is the "clipping resistor" at VREF pin. I could not measure any significant clipping and liked the sound without the R, however this might be personal taste. I'll definately leave this option for the next design.

Hope some will join this discussion so that everyone can benefit from our findings 😉

Best regards, Daniel

SOLD

FQA19N20C x4
Just a dollar each. Shipping is whatever USPS charges.
200V 21.8A Mosfets. Bought from Mouser years and years ago. Never used, never tested.

Hello,

I'm selling a pair of SB-Acoustics Satori TW29B-B beryllium dome tweeters for €300,-. They're in perfect condition, in the boxes.
I'm located in The Hague, The Netherlands. They can be picked up or I can ship them anywhere.

Hello to all,

I recently have been looking for a different pair of speakers for my workshop and ran into what the label says is an A25 Scandyna product. However, when I took off the grille cloth, there were three speakers and no vent.
It appears that this is actually an M25 via the good folks of the interwebs and that is was built before the A25. That might explain why the sticker reads 4 Ohms and the speaker terminals say 8 Ohms. (Which is also what the impedance is-- DC resistance at 7 Ohms)

The sound for an extremely cheap pair of speakers is surprisingly good-- the highs are very present and clean with a nice mid range as well as plenty of bass, much more than I expected with a sealed cabinet. However, I did find the bass a bit boomy so I decided to open the cabinet and see what was inside.
Basically, the cabinets are very cheap particle board and the front baffle is loose on one speaker. It appears the baffles are stapled in at an angle and one in the corner by the bass missed so the whole baffle can flex.

As the speakers sound much better than I expected, and they seem to be a nice match with my Dynaco Stereo 35, how would I go about repairing the cabinets? As the original glue pulled quite a bit of the wood around the woofer, I am thinking it might have to be reglued?
Would it make more sense to build new cabinets all together? (Including putting the drivers in a row, or does this not matter so much?)

Thank you for any help!

Hi diyAudio

I have been looking for a pair of not too expensive speakers and have found the Jamo E870 to be interesting. But it is a old pair of speakers and i can't find a lot of information about them. (i have been searching for a review, but can't find any)

I hope you guys know something about them, or know another decent pair of speakers in the 100-200$ price range 🙂

I would like to use the elements of a skyline diffuser i'm building as Helmholtz's absorbers to kick off the modal resonances of a little listening room.

Both have a narrow bandwidth and it is not possible to couple them by models (IMMO).

So I have to misure.

How?

Hitting the cavity by tapping? ... blowing in the hole ? ... noise?



For the larger element, the original formula predicts the resonance at 140 Hz, and I see (empty cavity, mic in the cavity),

...

Hello,

I would like to better understand how one screws a speaker to an enclosure, especially how to set the gasketing tape and how much pressure one has to apply on the screws.

So, any link to a picture or a good tutorial on that specific topic would be really helpful.

If those pictures or tutorial involved the Peerless TC9DF18, it would be even better! I see no gap to to host the screw heads. Should I apply pressure on the soft material surrounding the holes? Should I let the screws heads override the surface? The idea is to screw it from the outside of the enclosure, so to have the smallest possible gap between the speaker's edge surface and the enclosure's surface.



Thank you for helping.

Realise F3 is not as important for a closed design but the question still stands 🙂
I'm getting a modelled f3 of approx 55hz and f6 in the low 40's. Qtc is around 0.65 but can alter box size

Shared album - lance bartlett - Google PhotosFiberglass construction, perfect condition, brilliant white.made by a car body panel manufaturer in poland (horns.pl)

Cost £1200 Inc solid 3d printed PLA parts. JBL 2452h drivers to fit also available. 24 inches wide.

Shared album - lance bartlett - Google Photos

£600.

Another to go is a LM4780 module that I got from the EU. It's the module only with no heatsink, case etc and pics with these are only for reference. Sounds OK but nothing flash. DC offset was less than 6mV for each channel.

The crappy electrolytic caps were changed to Nichicon FW for the power supply and FG for the feedback. The chip had been installed back from the edge of the PCB which meant the chip could not sit flat on the heatsink. It was installed so the PCB went under the heatsink which was mounted on spacers but a metal spacer on the heatsink would also work.

Power supply to be no more than 18-0-18 transformer to give ±25VDC rails as the caps are 35V rated. With this supply expect 29W into 8R, 41W into 6R and 57W into 4R. Heatsink should be better than 1°C/W.

I don't recommend running it in parallel as it didn't like it even though the feedback resistors have 0.1% tolerance. The same would also apply to bridged mode.

These are tricky to mount as the mounting screws can go off on angle but I will supply the spreader that sits on the chip face as well as the insulated mounting screws which as required as these can touch metal in the mounting holes. It's essential that the chip be isolated from the heatsink and I'm supplying the used silicone pad. I'll also supply the input wiring and connector.

I couldn't find anything on this module but did find a pic of the PCB which is attached.

I'll cover the postage in Australia and again this is for the module, spreader, screws, insulator and input wires only.

I've written new software for the HP 8903. Link below:

https://github.com/cosmonaut/hp8903

It's written in python and open source. I'm posting this in the hopes that it may be useful to someone else.

I know there is already some other HP 8903 control software out there but I wrote new software to support multiple operating systems and to create a plotting style that I preferred (and could be made more configurable by the end-user).

Anyway -- if anyone does use this and runs into issues (or anything) please let me know here (or on github) and I'd be happy to try and help.

~MCP

Well I finally finished my two speed Valhalla for my Linn and so far it works great and sounds even better. I had been wanting to play 45's on my Linn for quite sometime but I have always hated the adapter pulley so I've always played my 45's on an old Ariston RD-11S. 45 Singles have always been of mediocre quality so it really didn't matter. However very high quality 45 LP's are much more common now and I wanted to play these on the Linn. At the beiginning of the year my Valhalla suddenly died and I was forced to repair it. Not bad really considering it has been powered up since 1988. Thanks to the forum I was able to get a schematic. After realizing how simple the circuit it was, I decided to make a 45 rpm version. I purchased another Valhalla on eBay and mounted both boards externally in a separate case from my Linn. I wasn't very impressed with the power supply on the Valhalla. For 240V users it has a full wave rectifier filtered through two 47uF caps. For 110V user like myself it uses a voltage doubler circuit to obtain the 320V DC high voltage supply. Despite the low current requirements this is still not a very clean power supply so I built a separate power supply to power both boards using 110-240V transformer with rectifier bridge and 600uF filter cap. I also built a separate regulated 10V power supply for the low voltage circuit. I then added simple switching to allow easy changing for both speeds. I just finished it tonight and have been listening ever since. I think the better power supply has definitely helped with reducing motor vibration and the the sound stage has openned up and deepened. It reminds me of when I first heard a Lingo/Valhalla comparison but not nearly as dramatic. I am definitely happy with the improvment.

Today I want to tell you about how to make useful the DIO part of an old but well old AP SYS2722/2522, which has only SPDIF I/O and quite useless nowadays. I have to use my AP with my USB DACs and SPDIF/TOSLINK I/O no use, hence, I losing convenient features of the AP2700 software(don't tell me that external sweep is ok too!). To make my AP "great again" I made a simple USB "SPDIF" optical bridge with 24/192 IN/OUT at CM6631A and default FW. See the attached schematic. Now I can make a fast and precise frequency response or THD+N vs frequency etc. After the external sweep, which drives me crazy, now I feel much better.

Hello DYA:

I have 3 testers. B&K 747, B&K 707, and Eico 666.
All 3 have been extensively rebuilt and have no problems.
747 and 707 have the 55 line regulation bulbs soldered into the circuit (sockets are bypassed).

All 3 testers have had solder joints reheated, all components checked and replaced if necessary, and worn sockets replaced.

All meters work freely. All are set to factory specs.

The problem occurs when testing rectifiers. Test 1 always reads lower than Test 2. This occurs on all 3 testers. 5U4, 5Y3, 5Z3 all do this. I have at least 20 of each, old and new, they all do this, except for a very few.

The same circuit is used to test both sides of a FWR. Switches have been cleaned multiple times.

Can anyone explain this? Does it have something to do with asymmetric heating? Thanks, Mark

SOLD
8x 240
11x 9240

Since they have been measured lets do $3 each or if its already a pair then $10. Tell me if thats crazy or good pricing. I dunno.

240's I tested on my transistor tester I forget what the heck numbers I asked it for but here are the responses from the tester on the 240's
2x 3.38 1.48
2x 3.41 1.45
1x 3.25 1.59
1x 3.22 1.62
1x 3.29 1.56
1x 3.42 1.44

One of those numbers must be VBE. Not sure which.

9240's had these numbers
2x 3.36 1.44
2x 3.45 1.36
2x 3.49 1.32
1x 3.46 1.36
1x 3.42 1.39
1x 3.35 1.45
1x 3.37 1.43
1x 3.38 1.42

I’m rebuilding a Digital Designs Z2 .

The amp uses the 22uf 250volt bipolar caps .

Are these a critical part wondering if I can switch the values of these say to a 10uf or a 33uf 250 volt bipolar cap ?

I would use the Mylar caps but I don’t have enough room on where they sit in the board with all of the other components in the way .

In the floor-standing speaker with dual woofers, closed-enclosure system, is it necessary to divide the chambers for each woofer? I’ve seen both dividing-chamber type and not. Which one is better? And what is the purpose/advantage of dividing chamber? Thank you

Anyone have these laying around? I have a Sumo Andromeda II needing new Output devices...

Don't know if I can trust ebay...

Let me know.

I have a Halfer DH 101/DH200 that I built from a kit in the 80's. I am a novice about electronics.



The combo was working well and then one side of the stereo channel went dead. I switched to mono and both sides produced music for several weeks. Now the system is dead no sound from turntable, tuner, etc. I checked the fuses, but are OK. Checked connections cables, power, etc., nothing.



The question is how can I check if the pre-amp or amp has failed? I have only a multi meter, and limited knowledge. Any deduction way to check this?

Beside the Mooly amplifier am I trying to experiment and want to make a precise dimmer for one single 3 mm diode.
I think I can use a simple potentumeter for the dimming. It have to be able to dim from off to max on. But how shall the power supply be build? Do I need to make an reference controlled voltage down to i.e. p-p ripple 1uV / 0.1uA or can a less precise power supply do the same?



I hope to be able to dim a single diode and keep the amount of light constant, no matter if the main voltage should change or anything else.

I have two ARC D76A stereo amps that died because the driver card G10 boards and electrolytic caps fried with radiated heat from the output tubes. I'm not restoring them, I'm reusing the XFMR's to make the best amp I can. My speakers dip to 2.7 ohms.

I'm going to parallel the output tubes of the two sections of each stereo amp, and run them with a single driver stage per chassis.

The first stage is a Kimmel Mu follower card marketed by Wellbourne in the '90's that sounds just wonderful in my Dyna Mk III. It uses a 5751 or 12ax7 for its triode, and has the pentode section of a 6U8Aa as a load/CF, feeding the triode section of the 6U8A as a concertina PI.

I intend to run a cap coupled, 6N1P LTP diff amp coming out of the concertina PI, and directly couple each output to a 6N1P CF and thence to its two output tubes (per phase), KT120's. This is ala the ARC VS110.

I'm not sure I need the extra gain of the LTP diff amp, I could just cap couple the Kimmel PI output to a 6N1P CF, but the ARC output xfmr's allow grounding the output tubes' cathodes through the OPT secondary, a local feedback. I'm not sure how many dB are used up, hence the need for gain, I think.

I would appreciate any comments on the above, but here's my question:

The ARC 76A goes to a lot of trouble to create a regulated screen supply (that also feeds parts of its driver card). The (latter design) VS110 just tags the screens to the B+ through a 100 ohm R. I haven't found the VS110 power supply schematic, but could easily imagine it to have a regulated B+. (I understand that my B+ voltage is too high (590V) to do that conservatively on my amps.)

What are the Pros and Cons of taging the screens to the B+? I thought it was considered better to reference the screens at a fixed value above the cathode and let the B+ sag as it may, hence the regulated screen on the D76A, or at least a separate screen node in the PS. The old Fender 5E8A twin and the Vox AC10 SRT were the previous use of that screen to B+ that I was aware of, neither hifi.

Thanks.

Dan

I introduce The Cathedrals.

They are an all sealed, active design. They are in the concept and planning stage but comprise the following:
1 x Dayton RSS390HF-4 15" aluminium woofer
1 x SB Acoustics SB17NBAC-4 6" aluminium as a midrange
1 x SB Acoustics SB26ADC 1" aluminium dome tweeter

The SB26ADC may be waveguide loaded, if the profile of the Visaton WG148R is suitable.

Current crossover points are ~ 200hz and ~1900Hz.

What I wanted over my current 3 ways:
- Larger woofer. a 15" should move enough air.
- Lower F3. The Dayton models ~32Hz in a 124L sealed enclosure. There's enough xmax and with an active crossover I can tailor the in-room response with xmax to spare.
- Modular. I want to separate bass and mid/tweeter sections... such that I can replace mid-tweeter or have different options with the RSS390 filling in bass duties
- Wanted to try a waveguide. This may not work in practice. I have a plan B if that is the case.
- Try an active crossover. This will be using a Raspberry Pi, running ecasound LADSPA host and credit to Charlie Laub's Active Crossover Design tools to provide the ecasound filters.
- An all metal design

The relative phase graphs show the phase difference between driver pairs. I'm trying to get these <= 15 degrees at least 2 octaves either side of the XO points. More work required

Hey guys, I 'm wondering if anyone has one of these sitting around their parts bin. The only ones I seem to be able to find these days are coming directly from China and I do not trust that they are not counterfeit.

I'm looking for one (1) LME49720HA op amp. this is the one that comes in a TO99 metal can. If is has been soldiered into a dip-8 socket already, even better!

I'm looking to match 2 others I already have.

Thanks!
Andy

Hey everyone!

It's my first time posting here, been reading the forum posts for a while and they're always super helpful.

I have a quick question, would any of you be able to help me find the detailed specifications of Pioneer's TS-A1684S 4-Way speaker? I've scoured the net for a while and can't seem to find anything more than the dimensions and basic info on Pioneer's website.

I'm building an enclosure for a friend of mine and don't have any testing tools during this quarantine 😛 so I can't work out the values myself that I'd need to calculate it.

Any help would be greatly appreciated! Hope you are all keeping safe.

Live4SK

I have 3 of these NICE Vifa 4" coax drivers. these do not have any sort of a crossover on them, you will need to make your own. somewhere i might still have a crossover schematic for them, not sure. otherwise would make nice drivers for an active DSP Bi-amp system.

I have three of them never used. 8ohm. rubber surrounds. sometype of polymer/plastic cone. cloth/silk softdome tweeter.

$25 for all 3 plus shipping

I have a Hifonics Brutus amp that has a damaged power supply. The power supply uses IRF44n transistors, 47ohm gate resistors, and the drivers are A1275 and C3228. They were all bad burned so I replaced all gate resistors, and the drivers for the mosfets and checked the drive at the gate pads. I found some normal and abnormal drive waves. I have attached images of what I found. I’m not sure why I’m seeing the abnormal drive wave.

The first three gate pads on the right side have an abnormal drive wave and the last three on the right side have normal drive.
On the left side the first three gate pads have normal drive and the last three have an abnormal drive signal.

David

Hello everybody,

i have a problem with my amp and i would like to have some opinion.

It is a unison research simply Italy, 12w class A tube, single ended.

It all started a few months ago when, by rehearsing, I realized that the left channel sounded less well and at a lower volume than the right and also emitted a slight hum. So I decided after several emails with the company, to send him in assistance to the unison in Treviso.

They replaced me with some components that they said were worn out and changed the valves because, as they said: "because of the way the amp was reduced" maybe my valves had been ruined (actually in the previous months they had strangely and mysteriously broken well two new el34 svetlana winged C that I had bought to have some fun). Expenditure on repairs only, excluding valves: 180euro.

However when I return from the company, I turn on the amp, I immediately notice that for the same position of the knob, the volume is higher and everything seems fine, until ... I disconnect the right channel and I hear the hum in the left there is still! I send an email to the company and they tell me it's very strange because it didn't happen to them and they even kept it on trial for a week. Then the pandemic broke out and therefore there was no follow-up to the thing.

I wanted to ask you if you have any idea what it can be: it is a hum, not a murmur, only in the left channel. You can also hear it at zero volume, it exits the tweeter and the midwoofer and begins a few seconds after the amplifier is turned on, as if it were due to a final valve. However, when the valves are exchanged, the problem remains on the left. I tried to disconnect all the sources, but the problem remains (on each source), I tried to short-circuit a rca input but nothing changes, to unplug the fridge, every household appliance or switching power supply, without success, to change power cables and power but nothing.

What can be?

Thanks to anyone who wants to contribute ...

Hi All,
In active crossover Hi-Fi systems each loudspeaker element is individually powered by its own discrete amplifier. What would the likelihood be of cross-talking between them via their respective cables ?
Should the cables be kept some distance apart or can they be routed together from amplifier to speaker ?

Would love to get some commentaries/ideas on this.

I'm not dealing with digital often and never re-capped any CD player. Now, I would like to tackle recap of old Parasound /Cec player. The reason I contemplate the recap are various. After I received the player it played one CD than it refused to play more. After a day of warm up it played more frequently and after two days it all seems fine . Giving the age of a player and other consideration I would like to re-cap the digital part (big pcb on the picture)
It contains PSU and various part of the players digital circuitry. Most caps are small Rubycon blue , and a few around the servo IC's are Rubycon gray.
What would be your cap choice to replace them? I'm willing to spend a little more then standard caps since it is my personal player .

Hey all. I have a PC that I'm attempting to connect to a surround system. This seems to be a knowledgeable group, so I'll start with relevant specs:

PC: Win10 Home, x64
Sound Card: Asus Xonar AE
(Link to Specs)
Sound Card Chipset: C-Media 6632AE
(Link to Specs)
Receiver: Panasonic SC-BT300
(Link to Specs)

Receiver has either Red / White Analog in, or S/PDIF in.

The long and short of it is, I want to use 7.1 (at least 5.1 - I understand there may be limitations at play), but the card seems to only output 2 channel audio from the S/PDIF.

I can go into Window Control Panel > Sound > SPDIF Out > Properties > Supported Formats Tab > Dolby Digital > Test = and hear clear positional audio from 5 of the 7 speakers. This is not "virtual surround". The receiver flashes "Dolby Digital" when testing in this method, but seems to revert back to 2 channel when the test is complete.

Games and other apps are only presenting in a 2-channel format. When I had my crappy Logitech 5.1 system (with analog connectors), I was getting full positional audio.

I'd like to use my 7.1 (or 5.1, if that's as good as it gets) on my much more powerful entertainment system. Does anyone know of a workaround?

I found a post from a few years ago on a different site where someone resolved this, but they didn't say how... Something about finding the right drivers to make the sound card encode in Dolby Digital.

My entertainment system can decode:
Dolby Digital DecoderYes (Dolby® TrueHD, Dolby® Digital Plus, Dolby® Digital)(DTSTM-HD Master Audio, DTSTM-HD High Resolution Audio, DTSTM)

Any ideas?

Hello.

Looking for opinion on combining choke loaded class A (like MoFo) with idea from TubeCad - https://www.tubecad.com/2015/11/21/Single-Ended%20Plus%20Class-C.png

Myself have to combat strong visual diffractions visions to predict it's behaviour.
Maybe someone with trained eye can point at possible pointers.

Ideally in class C operating FET would receive signal from LPF with feedback from Source of Class A operating FET equalized with array of active filtering / maybe comparing input to microphones nested around speakers (should be possible to control the gain of circuit by not applying feedback to class A FET's gate).

The goal is to extend the low frequency domain.

I am already building MoFo slowly, and will be using mixed choke (50mH iron+ 20mH air core).
I presume that they might generate some DC, would that be a strong issue for paralleled MOSFET?

What if SE MoFo is given an extra negative rail for this class C FET?

Does anyone have any experience with this CD-drive?
I can´t find any schematics anywhere for this one.
It spins up, but very slow like 1/4 of normal speed reading the index. After 5-10 seconds it stops, and after some more seconds, display reads "No Disc".
My eye caught C14 in the powersupply (after regulator), 1000uF/16volt, which had almost opened fully on top. Changed it, but no difference.
Have tried to exchange the Mecha with a brand new one, never used. Same issue = slow disc-speed.
The Mecha is a Samsung with SOH-AAV F11 laser.
Would be nice, if someone had tried this also 🙂 🙂

When is better ?

I am not asking which one is better.

What is the relevant information to decide if is better a Capacitor or a Transformer coupling.

Maybe Plate resistance or Load resistance of next tube ?

I just posted a new thread in the Construction Tips section titled "New active 3-Way, Hypex and SB"

It should have been posted in this section... can it be moved?

I was reading about the mosfet conversion of this amp. and documentation. I have some left over T03 Profusion lateral mosfets and was cconsidering converting a Citation to an ESP P101.
The HK 12 that I can access is in great cosmetic condition, but it has a blown channel with some scarring on the drive board. The power supply works fine deilvering about 40 +/- Volts per rail unloaded.
Just don't know if I can shoehorn the ESP driver boards into the area where the Citation borads are mounted.
Anyone know the physical dimensions of the HK boards?

Thanks, Bill

Hi, I would like to know if I can replace ecc99 with 6cg7, changing the tension of B+ and heaters in this Pete Millett's schematic.
Thanks

el-scorpion — ImgBB



https://i.ibb.co/3cWqNgn/el-scorpion.png

Hi, This is my Balanced Phono board, recently finish, all seems good so far, sounds great. My last phono board was in 1980 something, things have change a lot component size wise, however the basic design is much the same as my 1980 one, this is just a balanced version of it. Still using the same Mayware Step up Transformers..


Mark

My 10s won’t make a sound until I press on the center of its backplate. Is this a problem I can fix myself? Hope so. Any advice will be appreciated.

I'm at the stage now with Xsim and crossover design where I have a decent grasp of the necessary concepts. But, I have been following a couple threads of late where Diyaudio members @Douglas Blake and @jReave have made to compelling post that has me thinking I don't know that much after all.😀 So, in the pursuit to dive further into learning more advance uses of Xsim and crossover design in general; I have attached some screenshots of a current 3 way speaker that has been my winter project. Also, I have included the Xsim .dxo file so others can play along as well. Sometime later today, I will take a couple photos of the one speaker that is completed. The other is in the final stages of french polish shellac and needs maybe 1 more week (hopefully).🙂

The inspiration/ idea for this build came from Paul Carmody's Tarkus design.

Selected drivers:
Woofer- Peerless SLS 830668 (65 Liter VB) ported
Mid range- B&C 6NDL38
Tweeter- SS D2604/833000 w/ Monacor WG300

Thanks in advance! This will be fun learning experience.😀

Hi,
Have had a spot of trouble with the filament power supply on my Ear 834 clone. When trying to get the voltage set with the trimpot, said trimpot failed. No voltage anymore. Replaced the trimpot, still no voltage. So I replaced the existing LT1085 with an LM317 because the board stated it could take either one.
I now have an output voltage of 14VDC or so but as soon as I put just one tube in, the voltage sags to 1,4VDC, even with the trimpot at the highest setting.
Input voltage does not sag, 14VAC at the transformer is stable, voltage at the rectifier is also stable.
Short of pulling all the components and replacing them, is there anything you would recommend ?
I've reverse engineered the schematic as far as I can tell.
Thanks

With lock-down in place a good thing to kill time is to open every piece of gear around and play with their guts as many of you might know.

It is time to mess with an MM & MC phono preamp, a Music Hall PA1.2. Lets see what we can do to improve the SQ shall we.

Unfortunately I don´t have the schematic that would make things easier.

Possibilities:

- Replace the pair of NE5532 with a pair of LM4562NA (I have a pair handy). Worth it? Drop in replacement?

-Add film caps to each IC at the positive & negative supply Vcc (one cap from Vcc+ to ground and another cap to Vcc- to ground)

-Replace the Nichicon 4u7 50v Fine Gold caps with Solen 5uF 250v Film caps that I have left from a Xover project. I assume these caps are in the output.

All recommendations and comments welcomed!

Saludos,
Rob.

Just experimenting with different window functions available within the awesome program FIR Designer.....

btw: this is definitely not a post where i want to complain about the program. It's just to show whomever might be interested in this stuff what to avoid while using the awesome program called FIR Designer M.

A little experiment on different window functions | Timo's World all around the globe

Hi,

I was looking for a DSP in Aliexpress and stumbled upon this DSP.

It seems it is based on the newer AD chipsets, with 4 inputs and 6 outputs with some good quality ADC and DAC.

Also, the price is almost USD$100 which is quite cheap compared to MINIDSP products.

So, what do you think? I would like to know your opinion regarding capabilities and ease of use with this DSP. I assume I can use my USBi to configure it?

The vendor sent me the software that comes with the DSP and it seems it is Sigmastudio. I am still checking it.

I would use this for active XO.

Cheers

hi guys. after problems with a previous amp. I bought a several more amps to try.
one was a tda7492. my question is, what or how do I use the btl mode as it states
Maximum power:50W*2/8 Ohm Mono BTL power 100W

cheers

Hi to all, this is my first post here.
I have successfully converted many Philips TDA1541 CD player in nonos mode.
I don't now how can I modify the 555ESD (or 705ESD) because it have a different digital filter: the CXD1088.
Any help is welcome.

hi all
This amp is not powering up.PS FETs are not being turn on.
KA2535A pin 15 has pulsing .01 to .53v on it.All other pins is below .00v
pin 15 is connected to the emitter of MPSA 651.If i pull the emitter of this transistor from the board i get 11.71v on that leg. Any idea what to check?

LM393n
1pulsing 5.04
2: 5.39
3: pulsing 11.62
4: .00
5: 4.41
6: pulsing 5.28
7: 12.36
8: 12.71

Couldn’t pass up the great deal on these at Madisound. Identical to the Regular Scanspeak 10/f-8424. Running them from 500hz and up. Super flat response up to 15khz

I would like to convert a KEF R-107 Kube Equalizer to balanced input/ output. Somewhere I read that this would require 4 Jensen jt-11p-1 transformers , can anyone provide a schematic on how to wire them .
Thank you .

As implied by the subject, these were lightly used in a 2-way monitor. They are fantastic mids but spent most of their life in a box which is why I'm parting out the speaker. They will arrive well packed. Looking for $180, from suburbs of Boston in case anyone want to pick up. DM me please.

SOLD

what can replace the vifa c17wh-09 in ram Osiris speakers . tey don't make them anymore