I am looking for a current-production tweeter with high efficiency (95db+) with a frequency response flat between 5k and 20k erring on the side of "tilted up".
My budget is up to about $800 Canadian.

I am wondering if anybody can make suggestions I have not yet considered below.
Unfortunately I am one of those people who can tell when a tweeter is rolling off at 18khz... which rules out a lot of options such as the popular B&C compression drivers.

I am currently unhappy with the way my Beyma CP21/f sounds in my horn system, and I'd like to try some others. What I don't like about the CP21/f is that it seems to sound "sharp but rolled off..." despite extending to 20khz, it still lacks the shimmer I seek in most listening positions compared to other speakers i've experienced. I will be crossing over at 5.5khz

Here is the short list of the high sensitivity tweeters I have consider and their reason for not obtaining:

Hi And thanks for reading.
I am forever having to buy new soldering irons. The ones i buy last about 2-3 months then breakdown.
I use a soldering iron for about 2 hours a day everyday, they can't seem to handle the workload. Everyone else i know has irons that have lasted for many years.
My latest is a weller 40 watt which cost me 60 quid and lasted 2 months.
What can i do, which soldering iron can i buy that can handle the work load.
Thanks

Hi everyone!

Back in 1980, when I was designing and building my first “serious” stereo audio power amplifier, I found the safe operating area (SOA) protection circuit to be the most challenging part. After I was finally satisfied with the V-I limiter performance in stereo mode, I then discovered that it did not perform at all well when the two channels were bridged. When limiting was triggered, the voltage across the load would “snap” to ground producing nasty sounds from the speaker (please see the attached file for a simulation demonstrating the problem). I invested more time looking for a fix, but found none that were esthetically pleasing. As I never used this mode, I eventually lost interest in pursuing it.

Jump ahead 40+ years and this issue still nags me every now and then. There must be people on this forum who have come up with a good V-I limiter solution for bridged amplifiers. I know that most of you will say “easy, don’t use V-I limiting.” This response certainly has merit and may be the best way to go, but it does not really address the question. A well-designed V-I limiter extracts the most power from the output stage while providing reliable protection.

I know the this topic was discussed in the Amplifier based on 2N3055 thread but I didn’t see a solution if it was there. My searches may have missed other discussions. Does anyone have something to contribute?

Thanks in advance!

Bruce

Is there any consensus about whether Linkwitz LX Mini Style absorber stuffed cylindrical diffusers mounted behind OB midranges do anything beneficial for sound? It seems they are quite well hidden in the "shadow" of the magnet structure, so I can't see much energy making it into the cylinder. I made a crude set and didn't measure much difference to frequency response. Obviously, FR is only part of the story, or maybe I didn't stuff the cylinder tightly enough. However, I haven't noticed any other designs using this configuration, have they been proven to be useless?

As I understand the CS4398 it needs to work in software mode to set the DSD format, it not possible in the stand alone mode. If that's the case, what is the easies way to set the software bits, is it with a uP the only way or can a EEProm do the trick?

I'm thinking of to use the CS4398 with the XMOS DSD USB receiver, if that is doable?

Hello All,

I didn’t see a post or sticky about it which is kind of surprising-forgive me if I missed it. Anyway, I’m seeking guidance on buying my first PS as I get into building. My primary focus will be (no surprise) power amplifiers. I’ve already determined I’d prefer linear power but that’s about it. Would multiple outputs be very useful? What voltage and amperage do you recommend? What features are make or break for you? As I said, I’m just starting out so I don’t need much but I would also prefer not to outgrow it in a year or two. I don’t have a ton of money to throw at this, but I feel I can go up to $300. Thank you for your help and patience.

-The New Guy

I'm a newbie here. First post. My goal in this post is to gather the attention of some knowledgable amplifier folks as in a coming/subsequent post I'll be asking for some advice in troubleshooting a Parasound HCA-2003. Now, on to my immediate goal.

Shown is my stretched, dual mono, heavily POOGE-2 inspired modified DH-200. What else can I say other than it's been performing nicely for the past fifteen or so years. I'm the original owner. I do possess a second completely stock DH-200 yet, in my laziness, have never directly A-B'd them. With lots of inputs and outputs to my 5.2 system, it's a rather time consuming exercise to do that. My bad.

The modded amp is used to feed the mid/tweeter housing of B&W 801-II's. (Two channels of the aforementioned Parasound amp are used to feed the B&W's woofers.)

I'd be happy to check back here to comments/questions. Maybe some folks here can guilt me into performing the A-B exercise (with the stock Hafler and/or the Parasound).

I recently bought a new power transformer with a winding rated for 6.3V @ 5A. The winding is oversized as the amplifier will only be drawing 3A max of heater current. After testing it with the actual tubes which draw about 2.8 amps the voltage is extremely high at over 9 volts. Unloaded I read over 12V on the winding. Throughout all tests the HV winding was left unloaded, but I don't think it should matter that much.
I understand transformers are not perfect devices and there can be some fluctuation in the voltage, but this is not acceptable in the long run.
Is this to be expected and my order was too oversized or the transformer was wound badly?
I'm reaching out here as I may be able to ask for a refund or at least a fix if the transformer isn't supposed to be behaving like this.

Side note: assuming I can't get a refund or get it fixed, would it be cheaper to build a regulator (considering the trafo itslef costs about 50EUR)?
Keep in mind the space under the chassis is tight and I'm not looking to bring in that much more heat to dissipate.
I'll say that I'm slightly skeptical about the regulator as the current being involved here is fairly high and I fear the power wasted to heat would be huge.

On another DIY audio forum I read about placing a un-connected power transformer on top of or right next to the power transformer of a amp, preamp or other audio equipment. It is said to make the equipment sound better. The exact reason is unknown, but thought to have to do with the radiated field of the power transformer being influenced by the in-active transformer’s core material. This is easy to do with EI core transformers, just set a spare EI core transformer right on top of it. I have tried this and it does make the equipment sound better, more open and dynamic to me. Has anyone here tried this simple experiment? Most tube equipment has EI core power transformers.

I am looking for some UTC MQL-5 coils, new or used.

I will no longer provide EnABL kits (Nov. 21, 2016)

Edited March 20, 2013 re: shipping charges The USPS rates changed in late January. I discovered this the hard way. International rates have ~ doubled.

I assemble and provide a "kit", intended for the installation of "EnABL" patterns on loudspeaker driver cones.

This kit will include the following:

1) Speedball type B nib holder
1) set, A-1 through A-5 Speedball pen nibs (5 nibs)
1) #99 Speedball pen nib
1 oz. Microscale MI-4 Gloss coat
1 oz. Model Master Acryl flat clear (stealth finish)

Mailed in a 6" x 9" bubble mailer. The liquids will be enclosed in their own zip-lock bag.

For the tidy sum of $30. Others (outside US) for $38 (this was $32 before the US Postal Service rate change in January, 2013)

Preferred payment method is by paypal. This has been underway since 2008.

You will need to source the brush of your choice to install the Gloss Coat & containers to dilute the finish to suitable viscosity for application.

Subject to change.

I've had these for a while and I've never gotten around to building something. These are open box, as I tested them once. Price is $50 obo.

Hello,

I am interested in modifying my Schiit Freya +. Before i pop it open i would like to have a schematic on hand to better understand its circuit.

There are other schematics of schiit gear ive seen floating around but no luck on the Freya. Does anyone have a schematic of the Freya + or happen to know where i might find one? I am assuming Schiit does not hand them out on request.

In the past couple of years, I've spent a lot of times reflecting on the measurements performed by Erin at erinsaudiocorner and Amir at AudioScienceReview. In particular, that the shape of an enclosure has a big impact on directivity. Basically, as sound diffracts around the baffle of an enclosure, it reduces how much sound is radiated to the top, bottom, left and right of the loudspeaker.

See: https://www.diyaudio.com/community/threads/what-do-roundovers-do.303155/ and https://www.diyaudio.com/community/threads/the-preference-for-direct-radiators.330741/

Inspired by that, I made an XPS foam "stand" for my bookshelf speakers in my office. Up until now, my speakers sat on a speaker stand similar to the attached pic.

The XPS foam "stand" is basically four foam cylinders, each cylinder measuring 10cm tall by 7.62cm in diameter.



I wasn't expecting it to make much of a difference, but I was curious if it would be worthwhile to eliminate the surface below the speaker. In the measurements performed by Erin and Amir, we can see that the space that surrounds the speaker makes a big difference on the speaker performance. And when you put speakers on a stand, that's not 100% ideal, because the stand itself impacts the sound.

Again, I wasn't expecting much of a difference, and I nearly gave up on this little project because it was time consuming and made a big mess. (I had to cut sixteen pieces of foam, creating an absolute mess of XPS foam dust.)

But, lo and behold, the imaging of the speaker is noticeably better. I really wasn't expecting much, in fact I didn't even listen to it after I finished the project, because I didn't think that improving things on one side of the speaker would do much. But I turned on my usual podcasts this morning, and the sound of the center channel sounds:

1) more solid.

2) It's bizarre how the speakers don't even sound like they're there. It's really strange, it's like the sound isn't coming from the speakers.

3) The soundstage is deeper.

And I didn't move the speakers at all (except that they're 4" higher now, because of the foam stand.)

Of course, this begs the question:

Does it sound better because it's elevated above the stand, creating more "space" around the speaker?

Or does it sound better because the XPS foam is damping vibrations that would normally get transmitted into the stand?

Or both?

I've rarely used spikes on my subwoofers or speakers because I don't want to screw up my floors. Plus, spikes always seemed a little "tweaky" to me and I figured they were probably about as important as fancy loudspeaker interconnects.

But I have a hunch that the improvement in the imaging is probably due to combination of creating more space around the speaker and isolating it.

Back in the day, Geddes mentioned off hand that one way to isolate subwoofers is to suspend them. Basically put some hooks in the top of the sub and hang them from bungie cords, so that they don't radiate energy into the floor.



This little experiment definitely has me thinking that might be a good idea. Since the speakers are in my office, I don't really need to worry about WAF. Perhaps figure out where the studs are located in the ceiling, and then suspend the speakers from the ceiling itself, similar to how you'd hang a plant.

I got an incomplete overnight sensations MT kit.
Some components are missing. Resistors, capacitors and woofers.

I found parts that are missing.

They use hivi b4n 8ohm midbass.

https://www.parts-express.com/HiVi-...zMlouQP7fe8nNGgaNVLjoCqM67wWMWcBoCSH4QAvD_BwE


What will be an upgrade to this driver that will work with cross overs (need to find diagram for overnight sensations). 4-5" midbass.
What thiel parameters do they use when designing a cross over. Is matching 8ohm impedance and sensitivity values sufficient to search for a compatible driver?

Resistors are 6 and 10 ohm. But they use white ceramic resistors.. will wire wound mills be an improvement?

This is what's supposed to be in a kit
https://www.parts-express.com/Dayto...recision-Audio-Grade-Resisto-004-6?quantity=1


Also capacitors are Dayton audio but 5% accuracy.

I think Dayton has polypropylene 1% accurate capacitors

i tried a lot times in this code but i am so confuessed to write this code...can anyone write this arduino code.....

Troels has two 861 2.5way designs on his website with kits or just crossovers available from Jantzen.
These are much lower priced compared to Troels's regular builds, particularly the SBA kit.
In the UK, I can get parts for the Discovery 861 ( with standard XO) for £650 + some shipping
The SBA -861-PFCR with Superior XO can be put together for £430 + some shipping.
These prices exclude wood, stuffing, etc.

http://www.troelsgravesen.dk/Discovery-861.htm
http://www.troelsgravesen.dk/SBA-861-PFCR.htm

I would appreciate some thoughts on these designs, and whether the Discovery kit is worth the extra.

which OEM drivers are these? Looks like from EU.

I have a set of Corel Beta 8 that has not been used. I'm thinking of using it in a rear loaded horn cabinet. I have also considered a taped TL. However, I have read that TL puts a lot of pressure on the cone and it is therefore good if it is a fairly rigid cone. Since the cone is quite light, I think it is not suitable for that.

But what is really my question is that I would like to take the hard top end off (peak at about 10K). There is a diagram for a nocth filter, but I would probably rather make it as a 2-way. The obvious thing would be to supplement with a super tweeter, but after what I've seen that GR Research does, I'm more inclined to make it as a traditional 2-way and let an ordinary tweeter work down to maybe 2K Hz (Corel 8 also has af big dip at 2,3K). According to GR Researsh, cutting at very high frequencies is very, very critical in terms of placement in order not to get counterface. Danny shows an example with his own full tone unit. What is your experience, should you look at the fact that it is a full tone and then just use it as a normal mid-woofer or should you rather do like the Horning Hybrid speakers, they have a super tweeter from a very high frequency together with a Lowther. Is it because he tests with 1st order that placement is more critical since the overlap is greater.

But do I ruin the whole idea with that driver if I don't take advantage of the fact that it plays over the entire spectrum.

Regards
Henrik

Sorry in advance if this opens a can of worms but a side topic in another thread peaked my curiosity on this question.

I read in multiple threads (as far back as the search function goes) that some people suggest using a regulated supply on the "gainclone" is just waisted effort and others both here and on other sites claiming good supply regulation can actually improve sound, even going so far as swearing by it sounding superior.

I'm curious of peoples opinion who have tried both and actually compared by ear both at low and high volume levels.

My guess is that far many more factors play into this than just regulated vs. unregulated voltage, but I am sure there must be some unbiased opinions here that have actually heard amplifiers employing both types that were based on the LM3886/3875/1875, etc..

Look forward to reading the replies 😎

Hi, I have a tr200 on the bench these days with some serious noise issues, due to the behaviour of the noise I strongly suspect it to be a clear error somewhere, I just cannot see it.

If loudness is on everything is fine, except if I hit the Tape/monitor switch, then noise comes back.

If volume pot is all the way to max everything is fine, turn it 1/20 back down, noise is back, no gradual change, On/Off.

Character of noise is low frequency buzz, like ground loop I believe. Level of it is very high, around moderate listening level through the speakers, and the tone controls seems to do their thing with the noise, so it happens “before” that stage.

Probably worth to mention, “crosstalk” between inputs and output stage is very high. With no input selected I can still hear the music relatively loud and clear considering it should be quiet, this follows volume pot and can be turned up and down to some extent.

Amp has been more or less fully recaped, including those ,33uf in loudness loop.

All switches and pots have been given some contact spray without any effect.

Any ideas?

The following is from the website for Coherent Audio speakers:

The Coherent “XD crossover” is exclusive to our line. This unique system uses no resistors to pad down the compression driver to match the woofer section output. The woofer has one inductor in the signal path, and the compression driver has one capacitor and optional bypass caps on it. “Impedance Matching" is then used to make the two drivers act as one in the critical midrange 800hz to 2500hz frequency range.

Click to expand...

Does anyone know how this would work? To my (limited) knowledge, one could move the crossover point by varying the values of the inductor and capacitor in such a first order arrangement and in so doing find a point where the summed frequency response of the two drivers is closest to flat. But how would one overcome the differing sensitivities? Coherent uses Radian coaxial drivers and, for instance, the LF of the 5212B has a sensitivity of 96dB, while the HF is 107dB. How does one balance that out without using resistors?

Hi, I have some of those speakers:



They are not Hi-Fi, but electric bass and electric guitar speakers and I would like to know if there are some typical hi-fi cabinet configurations that can be adapted to those speakers to help in reproducing deeper lows.

Please consider that most guitar amps reduce their feedback in low (and high) frequencies to use the resonance of the speaker/cabinet to increase the reproduced lows.

I know that it isn't an hi-fi question, but the knowledged people about how to design speaker cabinets are here.
Thanks for any possible suggestion,

Kind Regards
Roberto

Hello to all. I recently bought an HSU powered sub to connect to my VTL IT-85 integrated amp. The IT-85 has a pair of pre-out L and R jacks. When I hooked up the low level inputs of the sub to the pre-out of the IT-85 I get no sound. I use an Audioengine B-1 Bluetooth Dac which is connected to an audio input on the IT-85. I tried an RCA splitter from the AE B-1 output and connected to the HSU sub and it works fine. The only problem is the sub is at a fixed level when using the IT-85 volume control. I want to have the pre-out connection working so I have a variable volume level. Any ideas why the pre-out isn't allowing the signal to go from the IT-85 to the sub?

I get some transformer from my friends when he clean the warehouse. The transformer seem like output transformer with siemens logo. I can't find any data from google. Maybe someone can help me figure it out? The code was 71/1514, 71/1811 and 71/1516. Thanks for any help.

I have a pair of Axi 2050 for sale. 2" compression drivers. Based in UK so prefer UK sale.
They were bought fromm Nigel at Lean Business and have only ever been used in a home hifi situation. No PA use at all.
All original packing and will be double boxed.
Pictures are available on request.
After £1200 plus postage.
Keith.

Anyone got some 3a5 valves for sale in the EU preferably? Looking for 4 or 6.....

Greetings,
I have an Holfi integra amplifier, ver.1.1, I bought it thinking it would be an easy fix, but I didn´t expect to find every transistor on the power amp circuit replaced.
Can´t find any documentation online, I drawn a schematic to help me repair it. The output transistors were shorted so I replaced them, still it had full DC on the ouput, then noticed the first transistor (T1) was a 2sc2240GR and it needed more gain to get the proper bias, so I got a 2sc2240BL and solved the problem.


Now the only problem I have is no bias current on the output transistors and I find it weird to see a darlington BC879 as vbe multiplier (T6) that measures as a PNP instead of a NPN, and the pinout doesn´t seem to match the circuit board.


Does anyone know which is the original transistor? Is it viable to replace the base resistors and the transistor to a single npn instead?



Thanks.

Thanks to Planet10 for his design for my ff85wk/Blanda bowls. A friend with a vertical mill helped me machine the surface of one flat to mount the driver. Although I plan to cross them to my RS225-8 in 42 liter BR, I gave them a listen today running full range and was very impressed. The inner sandwich vent is a little tricky but do-able. I'll report back with my results on the 2-way version. Thanks again Dave.

Hello everyone,

I’m new on this forum and a novice regarding DIY audio stuff.

I recently bought a Polk R700 and a MiniDSP flex TRS which I love but then had not enough money for the amplifier. I started to look for cheap amplifier with clean output and around 200w@8R.

I came across Hypex NCore, IcePower and Pascal but even those where to costly to afford in kit. I started to look in old amps and by chance read about the Monacor IMG stageline STA800D (dual mono hypex UcD400OEM) and was able to buy one for 350€ new.

I would say that I’m 80% satisfied with the sound but that I would prefer to have a little more of “air” and resolution from the amplifier. I also want to keep THD and noise as low as possible until fed to the UcD400 module. I immediately thought of replacing the TL072 on the hypex integrated input buffer by the OPA1612 which has this slightly “airy” presentation as well as a lower THD than what the MiniDSP output is capable of.

But I don’t know anything related electronic schematics and choice of components. This is why I would be grateful if someone could look at UcD400OEM and tell if replacing TL072 with OPA1612 would work ?

I have 4 x BB1704, slightly used. $300 + pp at cost obo.

I’m located in Norway.

Pictures tomorrow.

Regards
RMalmin

Hi Guys,

I have had this project in the pipeline for a long time and finally getting some progress made on it. It will still take a while for the project to be completed but I thought I would start to post some information as a build log.

I really like the tall and thin format and think that it will fit in very well as a living room system. Inspiration came from Wesayso’s Two Towers build and the feedback on that design has given me new motivation to get going with mine. Other designs from OPC, Koldby, Halair and one I found on a Scandinavian site have all provided a wealth of information and different strategies to use.

Parts Express had a sale on TC9 drivers and after somewhat of an impulse purchase I had more than fifty of them so I had no choice but to build a line array!

I weighed up all the pros and cons and decided to keep it simple because my other speaker projects have had a habit of dragging on for years. The design I have gone for is most closely related to OPC’s in that it is a rectangular box with five separate sealed enclosures to keep the possibility of pipe resonances down and to allow the series and parallel speakers to have separate volumes.

To make my life easier I designed a cabinet in MDF that could be cut by CNC and would enable me to assemble it fairly easily. I settled on MDF because it is cheap and relatively stable after it has been cut. Plywood would need to have been assembled almost straight away to avoid warping. Birch ply is almost unobtainium in Western Australia, the only place that has it is AUD$300 per 8x4 sheet. I have used Hoop pine ply before which is also very high quality but still $200 a sheet and because it is a softer wood it warps even more unless weighed down.

I also live in a more remote part of WA almost 1200KM from the capital city so transporting sheets of wood is either difficult or costly sometimes both.

I was in Perth for the birth of my son so I was able to get the CAD design done and I had my car to take the cabinet pieces back in so the plan started to come together.

The CNC Company wanted a 2D DXF so the plans were drawn up in AutoCAD, I later created a 3D model from the 2D sketches to verify that it all fitted together and luckily it did. This is the basic design and some shots and animations from Fusion 360.

Here is a link to where the impedance comparisons started as that was useful information

Full Range TC9 Line Array CNC Cabinet

Hi every body.and thanks members of diyaudio.
I love amplifier .all of them but class D special for me.l try for 3 month work irs2092 amplifier and result equal waste time and money .
First l build schematic in datasheet .i. Use exactly same part in schematic and supply and mosfet but never work.l use +-35 regulate voltage for supply.the problem is one of. The mosfet is all time On and DC voltage -37 volt in terminal speaker.
This schematic

Professor is describing several experimental inventions....

THE BOTTLE THEORY OF SOUND

I expressed my cheerful readiness to be banker to genius.

"Thanks," said the professor, pocketing the scrip and resuming his position at the camera. "When I have pictorially captured smell, the most palpable of the senses, the next thing will be to imprison sound--vulgarly speaking, to bottle it. Just think a moment. Force is as imperishable as matter; indeed, as I have been somewhat successful in showing, it is matter. Now, when a sound wave is once started, it is only lost through an indefinite extension of its circumference. Catch that sound wave, sir! Catch it in a bottle, then its circumference cannot extend. You may keep the sound wave forever if you will only keep it corked up tight. The only difficulty is in bottling it in the first place. I shall attend to the details of that operation just as soon as I have managed to photograph the confounded rotten-egg smell of sulphydric acid."

The professor stirred up the offensive mixture with a glass rod, and continued:

"While my object in bottling sound is mainly scientific, I must confess that I see in success in that direction a prospect of considerable pecuniary profit. I shall be prepared at no distant day to put operas in quart bottles, labeled and assorted, and contemplate a series of light and popular airs in ounce vials at prices to suit the times. You know very well that it costs a ten-dollar bill now to take a lady to hear Martha or Mignon, rendered in first-class style. By the bottle system, the same notes may be heard in one's own parlor at a comparatively trifling expense. I could put the operas into the market at from eighty cents to a dollar a bottle. For oratorios and symphonies I should use demijohns, and the cost would of course be greater. I don't think that ordinary bottles would hold Wagner's music. It might be necessary to employ carboys. Sir, if I were of the sanguine habit of you Americans, I should say that there were millions in it. Being a phlegmatic Teuton, accustomed to the precision and moderation of scientific language, I will merely say that in the success of my experiments with sound I see a comfortable income, as well as great renown.

Edward Page Mitchell, December 1875
(The phonograph was conceived in 1877, perhaps July, by Thomas Edison; working by December 1877.)

Hello

I am using a P-1a and P-3a (modwright II) which both have the option of using an I2s input and ouput. The stock cable is not that good but no one seems to make a sensible priced replacement.

I have been able to source some 999 silver teflon coated wire and deicided to make my own replacement but I do not have any details of the pin conifguration. I think that only four pins were used and one is not but not certain.

I do remember that this may have been information already on the site and I have tried a number of searches using different words and names but have not been able to find anything.

If someone could either send me a link to the thread that has this or provide me with the details I would be very grateful .

I recently acquired an all original Technics SL-6 at a bargain price. It performs well but not flawlessly, and a quick check of the electrolytics suggests their replacement might be a good idea. Considering those caps are now pushing 40 years old (the plastic cover has a 1983 date code), it's probable that they're now at the ends of their operational lives.

Ordinarily this would be a piece of cake, but there are two 47 uF 16 V non-polar electrolytic caps across the stator coils as shown in the attached files. There's no exact replacement available at the usual suspects (Mouser, Digi-Key, etc.), so as I see it, I'm faced with executing the least worst of several unsavory options. They are (listed in no particular order):

1. Do nothing. Pros: Cheap, Easy Lazy; Readily available (as laziness tends to be). Cons: Failure in the near future likely; Subsequent destruction of motor driver IC likely (used AN6636 ICs are difficult to source at best).
2. Replace each with two 100 uF @ 16 V polar electrolytics bodged "+ to +" or "- to -". Pros: Cheap; Easy to source; Likely to fit. Cons: Ugly; Lots of conflicting advice regarding advisability and long-term reliability.
3. Replace each with one 47 uF @ 50 V film. Pros: Readily available; Permanent fix. Cons: Minimum voltage of 50 V is 3X over spec; Off board mounting required (no space); Relatively expensive; Mechanically less robust.
4. Replace each with one 47 uF @ 16 V dipped ceramic. Pros: Cheap; Easy; Likely to fit well. Cons: Possible issues regarding differences in ESR between the types; Lots of conflicting advice regarding advisability of the practice.
5. Replace each with one 47 uF @ 16 V bipolar/nonpolar Electrolytic (Surface Mount). Pros: Cheap; Readily available; Electronically mirrors existing installation. Cons: Ugly; Will need to bodge wires to solder pads; Mechanically less robust.
6. Replace each with one 47 uF @ 100 V bipolar/nonpolar Electrolytic (crossover type). Pros: Cheap; Readily available; More or less electronically mirrors existing installation. Cons: Off board mounting required (no space); Mechanically less robust; Lifetime and temperature rating unknown.

So what I'd like to know is if any of you have faced a similar circumstance or had any wisdom you could share on the subject. What did you do? How did it work out? And are there other options I might have overlooked? Enquiring minds want to know!

BTW, I understand there are some who take the "if it ain't broke, don't fix it" approach, and I respect that. But that's another topic for another thread.

Thanks!

*****SOLD*****
This is a I2S to simultaneous mode TDA1541 dac board designed by Miro. I have built two sets with two TDA1541 chips that i bought.

The 14 decoupling caps for the TDA1541 chip are CDE 0.1uf orange drops. Decoupling caps for the psu are Wima mks, and electrolytics are mainly Elna Silmic II. Resistors used consist of TAMA electric , Vishay and the IV resistors is non-inductive, non-magnetic, copper leaded Nikkohm. Logic chips are decoupled with high quality Kemet SMD x7r capacitors. The electrolytic caps may have some minor burn marks on the plastic sleeves due to my own carelessness during various desoldering to test different caps for sound. But i assure you that they are really minor.

This dac is designed by Miro and more info can be found here :
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-268#post-7159210

Miro also designed the PSU for this dac (not included in this sale):
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-268#post-7159234
Please study the power supply requirement carefully if you intend to use your own psu.

Important things to note :
1. If you intend to have no capacitor at the output, it is advisable to have a dc protection board as explained in the post:
https://www.diyaudio.com/community/...s-input-nos-r-2r.354078/page-285#post-7187720

2. Since i do not have the intention to add a DC protection board, i simply add output caps at the output and i did not further explore the dc offset trimming. But please be aware that DC will be present in the absence of the input signal as mentioned in the thread.
Please follow the instructions by Miro on the trimming of the offsets. You will need to explore this on your own, with your i2s source connected.

3. The only item not provided on this board is the two single Op amp for IV. The rest of the components are completely populated, including the new TDA1541A chip, which is only used for the testing of this DAC.

Of course, the board has been tested and playing well. Price for the board is 185USD, including shipping worldwide registered and paypal fees absorbed by me. And as usual i will buy coffee for Miro.

Hello,

I am trying to build my first tube preamp prototype based on RCA 12AU7 line amplifier drawing in the Tube Receiving manual.

I am trying to figure out how to handle the grounding for the HV/LV linear regulator supplied 12AU7 preamp. Anyone know best practice? Are the grounds referenced to Chassis earth ground or am I to keep them isolated?

Hi everyone,

I'm new to speaker design and I just started learning some theory and trying to design a set of bass-reflex speakers. However, I stumbled upon some information about transmission lines and now I have some questions that I can't really find answers to online.
First and most important question I have: I don't really understand where ports end and transmission lines begin. I've prepared a drawing with ports of different lengths and shapes (in the attachment). Can you tell me at which point on my picture the port becomes a transmission line?
Second question: if I decide that my port is so long that it qualifies as a transmission line does this mean that I have to stuff it with damping material?
Final question: Why do all the transmission line designs that I see use a full-range driver? I really haven't seen many tweeters on those designs.
Thanks in advance!

For sale: Philips OM931 hybrid power amplifier module as sold in the late 70s and begin 80s. High specs and good sound. In total 3; 1 is new and unused, the other 2 are taken from an working amplifier as used by me (these sare ideal for a repair job or for some amplifier project). Price is 20 euros for the 3. Payement by PayPal or IBAN/BIC.

Hello there.

Are someone here using icepower 500a? I have 1 unit and its break, blown up something like thst. The main issue is the thick resistor LTO 30 5ohms the t220 package resistor. The problem is the thick resistor blown. I replace wirewound resistor 50w 5omhs. And Its working great sound i think its back to normal ( i wish 🙂 ) but after 20 to 30mins the thick resistor is too hot you can cook egg on the top of it 🙂 i try to search in electronics store here in PH , but sadly no available 🙁 ..... is there anyone here replace or bypass this resistor? Thank you

Adcom 5300 a match for Spendor SP100 speakers and Audio Research SP9 Mark III preamplifier?

I found a box of 50 of them for near nothing and they have not been opened. I've never heard of them used in audio tube gear.

What do you guys think?

Attached is the schematics and gerber files for anyone who wants to build this.

Rectifier bridge heatsink - HSS08-B18-CP
Heat sink clip for H SS08-B18-CP - HSC-06
Heatsinks for LM338 - FA-T220-64E

Any suggestions on layout improvements or schematics are welcome and appreciated!

I’m having a hard time finding a in-line fuse holder for 4/0 gauge wire .

If I make a fuse holder myself what should I use to the blocks brass,copper,aluminum ?

Since the fuse holder will be under the hood I don’t want it to corrode and give me issue down the road

Hello dear people and dear usual suspects. . . . . ,

does anyone here on the forum have any idea for which Fb the Pensil 12. 2p or the Triton TML
and the Classic GR Mar-Ken12 ov8 have been constructed???

Merry Christmas to all global DIY people, dear crossover free disputants and a good Fullrange 2023

Regards Stefan

Aleph J builder from Wisconsin, USA

Hi all,

First post to the group. I’ve loved reading through so many posts, here and in the Planet10 speaker forums.

A friend turned me onto the Pass designs and I’ve been doing a ton of research and decided that I’ll build an Aleph J. The rave reviews of it make it irresistible. So I ordered a board set and the semis from the DIY store. As I peruse the BoM on this, there are several options for devices. Are they ordered by preference, class, or any other criteria? Or no particular order?

My current stable includes a pair of Klipsch Heresy IIs, JBL L-20Ts, Technics SE-A70 Class A-ish (so it says on the label) amp and SU-A80 preamp, a Denon DP-47F turntable, and a couple of Proton cassette decks, all of which I bought while stationed in Japan in the 80s on the USS Midway . I never have been able to keep a CD transport alive for some reason! I must admit that I love my “vintage” equipment (tough to hear myself say when I remember buying them new) and the collection sounds great in my own ears. But I don’t know what I don’t know. I recently bought a Schiit Modi DAC for streaming to get a feel for what better digital is supposed to act like. It’s a starter DAC before moving up the food chain. Looking forward to seeing what true high-end audio sounds like in my own house. I did work in a hifi shop in Memphis for a while so have experienced higher end solid state and tube amps along with similar speakers from the likes of Totem, Energy, and others. So ready to step up my game.

I was an avionics tech in the Navy, working on F/A-18s during the Gulf War and taught discreet electronics, digital, and radar as well. So I know my way around schematics and soldering irons. This is going to be great fun!

~Chris

NEED 2, Thanks

I was asked about power resistor inductance and whether it's an issue in spaker crossovers or not. I ran the MLSSA through its paces on some items in my parts box in the past, I think the attached tells the tale.

Thought I'd share it here.

Dave

I am attempting to use a Shure Beta 56A to mic a sousaphone for live performance. Because the performer will be moving around the stage quite a bit, I am attempting to design a wireless transmitter rig that can mount to the bell. So far, I have used a GoPro mount attached to the bell with threading adapters to allow the microphone to sit comfortably at the sound source without shifting or excess body noise. See photo below for reference



Samson makes a wireless transmitter unit that is specifically designed to mount on horn bells. Because this is the ideal form factor, I want to connect the Shure Beta 56A to the Samson ATX transmitter. See picture below for setup.



The main problem with this approach is that the mic's rated output impedance is 150 Ohms (290 Ohms actual) whereas the transmitter's input impedance is 3k Ohms. For reference, the transmitter has an input gain range of 20 dB. The output from the mic is standard XLR and the input on the transmitter is mini XLR.

Is there any battery powered mic preamp that would work in this setup to change the mic level output to the line level input needed by the transmitter? As long as it has small form factor, there are plenty of places to tuck such a device. Am I totally barking up the wrong tree? Is there another way to approach this entirely? Thanks in advance for any advice!

I have a very nice setup Id like to sell consisting of the Sonic Frontiers Power-3 monoblocks, Line-3 tube preamp, SFT mkii processor,
CD transport and Jitterbug all in black faced finish. Also am including bi amp version Mirage M-1 floor standers. Most include original boxes
and paperwork with thesecomponents except for speakers. This is your chance at a very high end turnkey setup that most would take years
to build and match.
Get this complete for 10k USD in SE Michigan will not be shipping. PM for details and appointments

Hi. I am based in Lutterworth Leciestershire. I have a Roksan kandy MkIII which has a Tentlabs clock & PSU following mods by Colin at Chevron Audion (Derby). It has just packed up with a blown fuse but with no obvious damage to the internals. I have replaced the fuse with the same result. Does anyone know who would be able to look at it and comment on & carry out any repair. I am happy to travel etc. I have emailed Colin but I'm not sure if he is still active. I was last in touch with him 5 years ago. Many thanks Adrian.

I finally was able to get my variable voltage reference designed for HV power supplies up and running, it works extremely well. Its designed to generate a a stable low noise VR between ~25V to 95V. Excuse the component values, particularly C1 I haven't decided on a final value for the feedback. The VR Im using now is a fixed design, but Im sure the variable will work just as well.

Wanted krell ksa clone amp, what's out there. UK based .

Hi guys,

Hope your well, I wanted to share with you a horn that I have designed with the help of a spreadsheet, here’s some beauty shots.

I was hoping that in theory I used the spreadsheet correctly by using the graph tool in illustrator and creating a 2D projection of one half of the horn which can then be swept around the central axis. Further reinforcements can been seen throughout to brace the 2mm thick structure of the horn. According to the print it would weigh over 1KG.

Would anyone like the 3D file of it?

I have already had a quote to 3D print it and it’s pretty expensive but if you have the cash to spend then I’m sure it would be a nice horn to have.

That said if anyone has any input or would like to simulate the horn to see how it’s performing then that would be productive! I’m dreaming in 3D at the moment.

I’ve kinda been put off by the project for now and plan on maybe building a K-402 because of the preferred directivity and ease of build.

Thanks!

Hi I am trying to fix my beloved f3, one board is running around 20 degree Celsius hotter than the other 35 one side 55 the other with one particular resistor getting very hot, around 130c. I have checked ac at binding posts both sides 0. Not sure what to do, or how to bias or even if this would be of any use. I have very limited knowledge of electronics, the techs in my area have refused to look at it because it is diy, or they look and say they can’t fix it after charging $100. I don’t want to give up on this amp as it gives me so much pleasure, so any advice for dummy’s would be most appreciated the value of the resistor has not changed with the excess heat
regards roger

For sale Khadas Tone Board. With 3D printed case and P089ZB filter for use with external power supply. Usb c khadas cable included, never noticed the difference with more expencive ones.

Price 75 euro plus shipping and paypal fees.

Hello,

I have a pair of Beolab 9 active speakers wich are playing fine but in the high frequency range they lack some detail in my opinion.
Looking at the service manual I can see that an ICEpower module is used for the bass driver and an Sanyo STK403-130 chip amp is used for the Mid and Tweeter.

https://datasheetspdf.com/datasheet/STK403-130.html
https://www.manualslib.com/manual/1494486/Bang-And-Olufsen-Beolab-9-6217.html

Both amps use a common switching power supply. I was wondering: would it make sense to add some high quality bypass caps to the power rail of the Sanyo chip amp or is that a total bs idea?


regards,

Eric

Hello all:

I have a pair of Jensen SG-300 (Heathkit AS-27) "Triax" 12" speaker drivers, that I currently house (on interim basis) in a pair of large, ported boxes (approx 24" wide, 36" high, 18 " deep) - designed for a full-range Wharfdale speaker driver.

The drivers are very similar in design to the Jensen G-610 (15" diameter vs mine which is 12"), with the horn integrated into the woofer, and a tweeter suspended in front (seems to me the series to which this speaker belongs was released a bit after the G-610) .
here is a link to an old ad describing the SG-300 :
http://www.tubularradio.com/jensenSigmabrochure.html

I'm unable to find evidence as to what Jensen recommended for the SG-300 in terms of speaker box, but I do understand that Jensen proposed either the Imperial or the "Ultraflex" (aka Onken box precursor) speaker box design for the G-610 - Jensen included in their designs sizes that would work for 12" speakers, so I am guessing that either design might be a nice fit for mine.

From another forum, here are some generic specs measured on someone else's pair -
SPL 98.3
Re 5.35
Fs 34 Hz
Qts .35
Le .035
Mms 40.2
Vas 15.

I would assume that these measurements give some idea about the design of the drivers, and thus what kind of box would be best for them.

They are being driven by 10 W from a SE-tube amp.

I'm looking for advice on a design for their permanent home - for 2 reasons :
1) They sound great, but I suspect that they could sound better in boxes that are optimized for them.
2) We are about to move into a condo, and floor space is a premium.

I likely would not build them myself but I think I have a contact here in Montreal who could help with the cabinet design and build. Suggestions of kits / blueprints etc. would be welcome ! I'd also be open to recommendations of folk in the Montreal or Ottawa region of Canada who might be able to help - in case my suggested contact doesn't work out.

Thanks so much !

OK, I know this topic has been done several times over the years, but the last I found was from 2012 and some of the info is now outdated. Was hoping to get a few quick pointers on the current state of things, maybe something I missed in my search.

Finally getting house plans together (after a decade of medical school etc) and am just gathering thoughts on which way to go with a theater, what will be needed, etc. Speakers would probably be self designed, multichannel active, and may consider a large number of speakers in initial design to handle whatever combination of Auro or Atmos or Neo:X or whatever might come. Currently, that might even include something like the Lexicon QLi-32 taking digital outputs directly from source or perhaps modded pre-pro, directing sound to 11 ear level and 11 overhead for a 22.2 system. Crossovers would likely be digital whether accepting digital from QLi-32 or something else requiring ADC, with a resultant boatload of DAC's afterwards.

Processing, crossovers, and DAC's for that many channels are hard (and expensive) enough, but it's the volume control that surprisingly seems one of the bigger challenges. I'd very much like to avoid truncation from digital level control.

So... trying to get my head around options for a remotely operable multichannel analogue volume control options that can handle up to say 80 channels synchronously (!!!) to see if that path is feasible. No specific budget but that is a consideration in feasibility. Would prefer to keep to under a couple of thousand USD or would seriously consider other routes (as DACs, amp channels, and everything else would already be piling up). If not feasible, the other route is DAC and volume control in pre-pro on a more reasonable 8-12 channels, then ADCs, QLi-32 or similar, boatload of digital Xover and signal correction and then DACs. I know tests have shown an ADC/DAC loop can be sonically transparent but I worry about doing that to a highly attenuated signal (low volume level settings) where I insert lots of digital xover and other processing in the middle of the loops. Seems I'd want to maintain full level through processing if possible, not be manipulating the tiny extra noise from the ADC in the digital processing chain, etc...

The previously suggested MBS MVC seemed like it might fit the bill, $399 and could be cascaded, so perhaps $4K for 10 of them... but discontinued, and seems whatever stock is left is listed at $799.

The RDL RU-VCA6A is a VCA solution that can be cascaded, but at $450 or so each that's over $6K.

The BDI ACS-400 8 channel would probably work as it seems likely they could be synchronized, but at over $1300 each (>$13,000 total) that's out.

The SPL Volume8 isn't remotely controllable or cascadable that I can tell, and expensive.

Is the nuForce MCP-18 still available? Can't find much about this one.


Seems like a DIY approach might be needed, which I'm fine with, but would like to keep to prefabbed PCB's and maybe even pre-populated. Anyone know anything about the vicol audio R-2R kit solution? Remote?

Rod Elliot has a multichannel volume control based on VCA's, that seems like it could be expanded, but I'm guessing implementing a remote control might be difficult.

Any other suggestions? Something I've overlooked or not thinking about, like some cheapish studio or PA solution that could be made to work? Seems like the products offered are overpriced for what they are, especially ones that use a cheap IC and handful of analog components.

I have a NAD C320 (20+ years old now) that won't power up. The symtoms appear a little different to other threads here although I've tried to follow advice from those but to no avail.

Symptoms:
Switch on the power on front panel. Red LED illuminates few a few seconds and then rather than switch to green I hear a relay click and red light goes out.

Looking at the amp one of the big 15000uF caps was bulging so I replaced both (C417 & C418). At the same time replaced the two adjcent ones (C423 & C424). Also, based on comments in other threads replaced C420, C421 & C422.

Testing the power rails with power supply board disconnected I'm seeing +46V & -46V as well as +37V & -37V so I'm fairly confident the power supply is working and the problem is with the protection circuit, although not sure as the symptoms quite line-up (I think the red light should go on after a brief green rather than off competely).

Any tips on how to diagnose this? I have the service manual but don't really know what to measure given the symptoms above.

Hi, i see old JBL L100 woofer is directly connected to the terminal. (like to all L series)
and a new L100 Classic not.

Can i connect the direct woofer to test the low freq ?
this is a new crossover L100 Classic.

Anyone have a heatsink for this amp laying around ? I have the board .

If not is there a way to make some kind of heatsink for this amp that would be sufficient?

Anyone have any ideas ?

Hello, I have Fostex FE103En in recommended back loaded horn type enclosure (2 of them). Both dust caps are completely messed up - who has children, can understand how this can happen 😉 I too have always had had a on / off subsonic popping issue due to my OPAMP active crossover, since I have a mono sub too (cinema application). I am thinking of different ideas: Replace broken FE103En by new ones AND include series capacitor ~150uF (??) for subsonic protection OR replace them by more expensive W4-1320SJ, which has higher excursion capability, right? OR I could use the W4-1320 PLUS subsonic high pass caps. Hard to get foil type caps at reasonable size, so I may need to use bipolar electrolytics to fit into the horn enclosure.
What is your opinion?

I just realized that the typical traces on a 1oz copper PCB board dont even come up to having as much copper as a 29 AWG wire! If building an amp with point-to-point wiring we would never even consider using 29 gauge wire, we'd use 20 or 22 gauge typically. Here are the numbers I see for AWG vs PCB trace cross sectional area: First take a look at this chart of wire gauges and their cross sectional area (last column is the area first column is the gauge)

1 oz copper PCB board has a copper thickness of .0347 mm (1.37 mil). If we have a typical trace on the board that is lets say 2mm in width. 2 x .0347 gives a copper cross sectional area of only .0694 mm. I see many PCB's here that use 1oz copper and have traces of 2mm or even less for tube projects. OK now here's the kicker... Note that a cross sectional area of .09694 in the example above translates to 29 AWG wire! Huh? Is my math wrong? How can this be? A tube amp wired up with 29 gauge wire seems ridiculous, I cant even strip 29 gauge wire without damaging it. And nobody would consider doing a point-to-point amp with wire that thin. Lets see how much PCB copper trace we need to equal a 22 or 20 gauge wire... 2oz copper has a thickness of 2.8 mil (.07112 mm). So a 2mm wide trace would have a cross sectional area of 2 x .07112 = .14224 but that only puts us up to 25-26 gauge wire! OK, so I have to increase my track width to a little over 4.5 mm using 2oz copper to get me to the equivalent copper of a 22 gauge wire? Now at JLCPCB the price triples when you go from 1oz to 2oz copper, and increases again going to 3oz.

What is going on here? Is PCB copper somehow different than wires? Most of the PCB's offered here by folks are 1oz copper, shouldn't we all be using 3oz copper boards for tube work?

SOLD

Not sure how many of these actually made into the wild because they were a relatively expensive kit to build. I've enjoyed this Jeff Bagby design but I'm going through a mild redo on my home theater / music room. The kits include an upper cabinet with a 8" B&C 8MDN51 mid-range and a Denovo FL-450 compression driver in a SEOS 10" wavevguild. The bottom section is a 2 cuft ported box with the Maximus 12" woofer. All the boxes were flat packs from DIY Sound Group so they're well build and braced.

All finished in Duratex, Speakon connectors and lined with 2" denim insulation. Crossover assembled by DIYSG. I will include a few pics here tomorrow and can share more for anyone interested. I have 3 speakers for complete LCR setup. Local pickup in southwest Missouri absolutely preferred. I would consider arranging shipping but this is 6 MDF boxes and a bunch of drivers. Would be at buyers expense.

Link to the kit: Maximus-12 LXE

Asking $sold

I am dipping my toes into speaker building and have just purchased a 2nd pair of Oris BD150 horns that I can fit up with a pair of Coral Flat 8 II drivers. In an ideal simple world I would like to build some bass cabinets and fit a woofer and a simple XO and drive them all off a 22W SET 845 amp.
To be honest Xmax and Qs are a strange language to me and I dont want to stuff this all up.
What is the best driver choice for the LF driver?, I would love to have super tight musical Bass and I dont need it to go Super super low (but it does need to cross over around 150hz.
I am happy to listen to all suggestions because I really am a bit lost

Hi all,
I'm keeping myself entertained these days with a NAD 2200 project (on a preliminary observation, I like the quality at which it's put together). At turn on, Protection and Overload lights come on.

Upon innards inspection, I see a scorched area on the right channel - pictures enclosed - which at first glance made me think Q303 has shorted (which would toast R309 and the 50V rated C309). I initially only replaced Q323 (used KSA992) and Q307 (used 2N5401), plus R309, R323, and C309. Some of these were carbonized/melted, or shattered (one of the transistors). My running hypothesis was that Q303 has shorted B-C and exposed C309, R209 (and Q307) to about 100V and torched them. But for some reason I didn't replace Q303 at this step. I fired it up, and got R309 burned up again. I have a 100V rated poly cap for C309, so I think it should be fine.

Realized my lack of diligence and got Q303 replaced (used 2N5550), but lost another R309 upon firing up. I am assuming whatever happened here (Q303 measures dead short BE, and low resistance CE - acts as a junction) took down more parts, and so somehow I still have a high drop over R309.

My conundrum is that the catastrophic failure doesn't really allow me to analyze the stages and figure it out. My plan is to start pulling legs of parts around there to check them (especially the diodes all around there), which would be all offline work.

Thank you for thinking on this with me.

For those who are tired of DIY . Very good condition , box and accessories. 70 LBS shipping from 48212- $1100

So I'm hooking up a fosgate t400x4 which will be on 4 -2 ohm 6.5 mids and tweets,with a fosgate t1000 BDCP on 1 fosgate t1d415 (DVC) thats 1000 watts rms(fosgate always underated,even the amps birthsheet is at 1540 watts rms at 2 ohms).So,I know this is overkill,but I don't mind the money cause overkill doesn't hurt.Getting the big 3,and I'll have a 2500 watt cap,I'm gonna run 1/0 from the battery to a splitter,splitter will have4 awg pure copper to the t400(which will have at least 100x4 rms(about 29 amps)) then a 50 amp anl fuse to THAT amp.....then 2awg to the cap,then to the t1000 to a 125 anl fuse(or 100,not sure cause at 1500 it pulls 109 amps,prolly a 100 fuse say(which max is about 1500 watts rms,but prolly never even need it figuring the 15 maybe will run 1200 rms max on a deep note)so my question is.....about the grounds.....since the t400 is split on 4 awg and the t1000 is on 2 awg,should I just ground each amp with the gauge going into the amp straight to a chassis bolt?Like 4 awg ground for the t400 and a 2awg ground for the t1000? Or should I use a block?I was just gonna use the same cable gauges going into each amp coming out as a ground to the same spot.Or do i need to use 1/0 as ground for both amps being that's what i used before the split.I was thinksince it's overkill I could just use the same gauge coming out of the amps as a ground as goin in.Also far as the t1000 into the DVC 15 speakerwire is 4 gauge copper enough?or maybe go 6? Also 1 more question to add,since I have 1/0 positive from the battery do I have to have 1/0 on the big 3 coming from the alternator to the neg of the battery? Thanks in advance for your help...this is bustin my brain a bit and I'm kinda ocd so I like to be perfect lol.

Hi,

I recently tried my long unused Stax SR5s & SRD6 S/B energizer.
Sadly, I found out that I have low output and distortion.

Any ideas?

Thank you,

Alex

PS I am handy with a soldering iron & multi-meter.

Item: California Audio Labs Aria mk III CD Player, all tube output.
Location: Melbourne, Australia.
Item Condition: Very Good.
Reason for selling: Not used after upgrade to Wadia 861.
Price: US$400 + postage.
Payment Method: Pickup - Cash, Bank deposit, wire transfer.
Extra Info: Have this wonderful sounding player for last 4 years, and it has been sitting in it's box for the last two years after I upgraded to the Wadia. Comes with original box (although pretty worn down), manual, and remote. Everything on the player works but it doesn't like CD's that are too scratched up, or else it skips. For it's age, it's in really good condition and there are no real cosmetic issues. Very minor scratches and marks here and there, but nothing major. Face is very clean. Not sure on the age of the player - 90's?. Sold as is. 230/240V operation. Left, right, and digital RCA outputs.
Pictures: Upon Request.

Just upgraded my pc from 8700k to 12400, probably a 20-20% improvement in speed.

So powered up the pc and lots of noise in the video on screen.
It just kept telling me windows had a problem and had to restart, which it did indefinitely.
So got my flash drive out with Win 11 on it and installed it.
Then went through Microsoft interrogation before I could get to the Windows start page.
Then put vivaldi (email, browser) back on but couldnt for the life of me find where the email client was.
Then tried to install iphoto express (a picture editting program which worked previously.
Its a 32 bit program and now wont install.
And not finished yet.....

I received an amplifier for repair. There was a lot of DC on the output and the servo could not take care of this. The problem was easy to fix as the diff amps their cascodes and current mirrors did not use matched devices for both the positive and negative complementary front end. I put in matched devices and the the servo took care of the then 10mV offset. Now it is <3mV. It is loosely based on Bob Cordell's output stage with a conventional fron end (Diff amp well degenerated and the VAS runnig at about 20mA. The bias spreader is made from a pair of NPN and PNP TO220 devices which are clamped to one of their respective sex output devices.
The amplifier runs off a +/-90v rail and uses a triple output from page 99 (figure 5.1b) of Bob's first edition book.

The bias spreader uses a 25 turn pot so very fine adjustment is available. The spreader also monitors the emitter voltage of the first pair of drivers which are alos TO-220.
The output devices are 2SC5200 and 2SA1943 all matched. The drivers are the same as the outputs. 0.33R emitter resistors are used with base stoppers of 3R9 on each output device, 4R75 on each driver and 100r on each base of the first triple drivers. there is no oscillation that I can see up to 100MHz.

There are 12 up and 12 down output devices on a massive heatsink! Weighs abour 12Kg alone. The power supply is a switchmode with PFC front end so it is well regulated. Runs at about 70KHz and he uses 35,000mfd on each rail. The PFC supplies the great regulation.

The re of the 12 // devices is small indeed

Now trying to set the bias to allow the amplifier to run in class A up to maybe 50 watts is my client's request. So first I want to set bias so that crossover THD is very small.

Referring to the attched PDF, the crosscoupled resistors on the pre-pre driver is 158R and that of the drivers is 15R (To allow all base charge to be swept away quickly).

Again referring to page 101-103 of Bob's book, he talks about this 26mV across each emitter resistor and having an optimum bais current PER DEVICE of 79mA. With 12 devices that is almost 1amp of idle current. No problem as the power supply and heatsink are up to the task. I checked the bias spreader that it was reducing it's voltage by about 2.2mV/deg C.

This 26mA through each emitter resistor does not ring true to me. What if your resistors are 0.1 ohm then 26mV across each represents 0.26A per device of idle current!

Back to the triple. There are 6Vbe drops so the bias spreader needs to develop at least 3.6 volts + the drops across the 0.33R emitter resistors.

I have a meter from top emitter to bottom emitter which gives me the idle current of one pair of devices. This voltage/0.66 = idle current for one pair.

I have a second meter across the bias spreader.

I have my Audio Precision reading THD and I am also looking at the THD residual on a second scope.

When I try to adjust idle current to be 100mA per device (1.2 amps total) I have to push the bias spreader voltage close to 4 volts. This does not sit well with me.

The THD is quite low at midband (<0.006%) driving an 8 ohm load. At 20KHz it is <0.07% when sweeping power from 1 watt to 350 watts.

However as I said above my client wants about 50 watts of pure class A meaning about 3.5 amps peak of idle current = about 600 watts of idle heat.😎

Look forward to some insight.

Hi

I need some help in troubleshooting this amp. When I first got the amp, channel 1 was working fine but channel 2 has no sound. When I turn on the amp, the green LEDs come on, then after a second the channel 1 relay clicks, the green LED turns off and the red ODEP turns on. But on the second channel, there is no relay click and both the green and red ODEP LEDs are on and there is no sound. After about 30secs the second channel relay clicks on for a split second and turns off. This keeps repeating about every 30 secs. I placed a DMM across the channel 2 speaker terminals. There is positive voltage present, and it keeps going down. When the voltage falls below approx 8volts, the relays clicks on for a split second and when the relay is on, the voltage shoots to approx 80volts. After a split second the relay turns off and the voltage keeps dropping down until it reaches approx 8 volts and the relays turns on again. This keeps repeating constantly. I have checked all the predriver, driver and the power transistors. There is no shorted component. Can someone assist with this. I have downloaded the service manual but the schematics are missing. Pls assist.

Thanks

I am in the process of building a 5.1 LM3886 amplifier. I'm at the point where I'm ready to assemble the channels. I've been slowly stocking up on LM3886 chips (which is hard to do given the availability) over the last few months. Mouser + Digikey haven't had any stock, and I haven't wanted to order from Aliexpress for obvious reasons.

I found these at two different locations in Europe, mostly audio/video repair companies here in Spain that had stock listed on the website. None of these were 'good deals' price-wise: they were mostly around 25 euros per chip.

I realize you can't tell much just by looking at them, but anything obvious I should be on the lookout for? In general I have 7 chips, one has darker white markings (not raised, it feels smooth). The other ones have slightly faded markings, like the chips are sort of older. I just want to avoid using a fake chip if I can.

Hello!

I have long been fascinated of the Dunlavys and would likte to build omething alike the SC IV.

Ia hve read and read and read everything i can about them and alo ought out what drivers they used. I didnt find exactly all drivers but a fair deal of them, but they are all out of production except their D27TG35 tweeter. I think their mids were Vifa M13 of some variant, and P13 in the SC6. I would like to build a pair for myself and my studio If i could buy the original driver i would have done that, but it is out of question.

So, I turn to you. I can get hold of the PDFs of the original drivers used in the SC, but my thinking is this that these drivers are atleast 30 year old designs. There has to be similiar driver today that are a bit more modern, with for example ventilation under the spider, copper in the motor, and more evolved motors and hopefully other upgrades.

Iam quite knowledgeable of speaker building and these arent my first project, far from it. Im able to simulate and create crosovers with my Line Audio OM1 meaurement microphone and Holmimpule and ARTA, crosovers I simulate at the moment with Xsim until i have learnt vituixcad.

The SC uses an ordinary old Vifa D26/7, my idea is to change it out to a waveguided tweeter with the 105mm diameter as D27 has, probably the Wavecore TW030WA11 or 12 depending on what the ohter drivers will be 4 or 8 ohm.

But, I am kind of stuck on what to use as mids and woofers.. One idea I had was using Peerless SLS as woofers as they shall be closed boxes true to Mr. Dunlavys ideal.

But when it comes to mids, I really dont know what tp go with.. Can you give me some ideas, but REMEMBER, all drivers suggested should be suitable for first order crossovers.

Im fully aware that there will be alot of components in the crosssover to beat the drivers in form for true first order crossovers.


What do you think?

I aim for a height of the speakers at around 150-160cm high, with about 30cm baffle width. Depth, will be whats necessary.

True to Dunlavys ideas, the baffle will be stepped and drivers time aligned, that is just a must in all speakers i build, the benefits are so good that i realla cant understad why people dont do it...

Sounds like a good idea in my head, but what do you guys feel?

Best wishes, MIJK

I picked up a couple of 50s/60s tube testers. Both work, but they don't quite agree with each other on the strength of any given tube. For some tubes, the FC-2 nails the Vu meter past 100%.

I don't know anything about these things, but it looks like a very simple circuit.

1) Is one of these capacitors key to the reading on the tube?
2) On a "device" like this, can I get away with replacing that 0.5uf 200v capacitor with two 1uf100v in series? That's what I have on my bench, and I don't really feature ordering parts for a thing like this, if possible. I think I have the .01uf and .002uf.

Any experience on working on these things would be welcome.

schemo: TV-II
schemo: FC-2

First pic, TV-II
Pic 2&3 FC-2

Hi all, I recently was given my dad's old 7240PE which he said just stopped working one day. Taking a look inside I saw all of the 4a and 5a fuses had blown. For the rest of this post I will be referencing the service manual found here: https://www.audioservicemanuals.com/n/nad/nad-60-7600/nad-7240/15238-nad-7240-pe-service-manual

My first step was taking out the driver transistors (Q427,428,429,430) and putting new fuses back in. Turning it on, R495 burst in a flame of glory. It's worth noting that the fuses did not blow, but I'm still a little concerned to do any further damage. Because of this I plan on proceeding with caution... and with the help of the internet.

I've poked around with my DMM and noticed that C427's points on the board are shorted even after I desoldered it (the cap itself was fine). Any ideas where to go next?