hi
i have 2 inuke nu3000 that have the same problem, they both can power on and the only 1 channel goes from red to yellow the other channel stays red and wont work. have any of you tried the same and maybe have a solution for it??

regards
mathias

Hello

Three days ago I finished my first tube project. So, you could consider me as a newbie in tubes. The project is a single ended class A mono power amplifier without feedback. Actually it is a modified version of “Glass House 300Bse” stereo amplifier circuit designed by Andy Groves (Audio Note). In general I used the same circuitry. Major changes I did was the second 300B paralleled with the single of original circuit, the different EI output transformer equipped with a special core of 17,000 Gauss rated at 100W and 1,500Ω primary winding. Also a huge choke of 10H/310mA. At the moment I haven’t possibility to upload the schematic (with voltages marked at all critical points) because my main PC – where the plans are stored – was damaged and is at service now.
So I will make a brief description – though I think many of you have knowledge – for the rest:
Input tube is a simple pentode EF86 – you probably know that simple pentodes in input is the beloved method of Andy Groves in all Audio Note amplifiers – which obtains the full voltage gain of amplifier. It is buffered from the double output 300B tubes thru a 5687 very strong double triode configured as simple voltage follower (0dB gain). The EF86 is AC coupled to 5687 thru a 15nF “mylar in oil” capacitor. The 3rd (suppressor) grid of EF86 it is connected to cathode which is biased by the appropriate 2.2KΩ resistor to GND and bypassed thru a 220μF capacitor. A 470nF “mylar in oil” huge capacitor connected across the 3rd suppressor grid and the 2nd screen grid eliminates the Miller phenomena. The two output tubes are of the brand “Full Music” equipped with solid carbon plates (300B/c). I selected these tubes for their ruggedness compared to mesh plate ones; we need as much as possible power because our speakers are some “heavy”. Plate voltage respect to GND is 450V while the voltage across plate – cathode is 393V as cathode is biased at 57V. The output transformer (made in Greece by G. Antoniadis laboratories - Thessaloniki) proven amazingly good, as under any output load the voltage drop of primary winding is just 7V. It stays cool (not heated) yet after 2 – 3 hours of operation. With an 8Ω non-inductive dummy load connected at output and with a sinus of 0.45Vrms as stimulus in input (that is the input sensitivity or the max signal for full output power) I measured with a DSO connected across the load a peak voltage of 13Vrms, stable, from 50 up to 2,500Hz. That means a maximum output power of 21.12Wrms. Without load the peak output voltage is 19.6Vrms. Later I did the usual bandwidth test according to EIA standards (output set at -3dB of its max value) to locate the -3dB points: The low limit is 12Hz and the high 22KHz, thus bandwidth = 12 – 22,000Hz. For the record, at 10KHz = 8.2Vrms (-0.8dB), at 20KHz = 6.6Vrms (-1.6dB), at 40KHz = 4.2Vrms (-6.6dB), at 60KHz = 2.48Vrms (-11dB) and finally at 100KHz = 0.86Vrms (-20dB).
The power supply includes a 400VA mains transformer. The HT voltage is rectified by a 5C3S (Russian military version of 5U4G and more rugged) and smoothed thru a “Π” filter composed from 3 nice Mundorf M-Lytic HV+ capacitors (those with 4 pins), Allen Bradley carbon composition resistors (can withstand better in high inrush current surge pulses than carbon film) and the huge 10H/310mA choke. Separate power supply is used for the 5687. Filament voltages for all tubes (except rectifier 5C3S) are DC stabilized via three LM1084 – 5A voltage regulators. Mains power consumption after a 30’ preheat time is stabilized at 1.2Aac. Output noise, though the whole device is still “bare” (cover plates and transformer covers are still in process) and so non screened, varies between 2mV to 4mV. I hope will drop down to 0.5mV after the shielding of everything.
What impressed me from my first contact with a tube amplifier (I am a solid state guy for 35 years) is that: a tube amplifier actually does not clip the output signal be it so is overdriven. Being sure that its max output voltage capability is 13Vrms/8Ω I tried bigger sinus stimulus in input than the max 0.45Vrms. Of course it is obvious that the sinus signal starts to distort presenting a rounding and a small tilt in the “falling” edge of sinus but does not presents a hard clipping like in solid state amplifiers (the signal is “latched” at the level of supply rails and presents a straight “duty cycle” like in square waves) a thing that is very dangerous for the speakers. Instead this, the tube amplifier simply “rounds” the corners of a clipped signal. Output transformer also plays a role on this.
For audition tests, please don’t ask me. I like very much music of any kind (from rock up to classic, jazz, folk and anything sounds nice in my ears) and I hear every day enough hours. But to be focused on a sound device it should produce significant amounts of distortion! For that reason I entrust only what I can measure with my instruments and I study thoroughly the technology of electronic parts from active and passive components up to relays, switches and cables. For example, in this project I had contact with carbon composition resistors for first time in my life. Also with “Mylar in Oil” foil capacitors, tantalum resistors, those M-Lytic HV+ of Mundorf, UPOCC Silver wire etc, etc.
To the present I attach 4 screen shots I taken from my DSO that show the behavior of amplifier in square waves at the 4 most common frequencies: 100Hz, 1KHz, 10KHz and 20KHz. Also a sinus that shows the peak voltage amplitude. In all measurements a 8Ω dummy load was connected at output. When I receive back my workstation PC I will make and the FFT analysis (how much is the 2nd harmonic?) and I will upload all schematics. Pictures of device in few days when chassis will be completed.
I will appreciate very much any comment and any suggestion. Thank you very much.

I am having some problems with a pair of SB Acoustics SB17NBAC35-8 drivers.

They seem to be more than a little off factory specs.

Madisounds suggests a 17 litre box with a 2" diameter port 7" long for an F3 of ~44Hz.

This is a similar alignment to what others have used in other examples I have looked at using this woofer. It just doesn't seem to work out with the TS parameters I get off the driver with DATS V2.

Compare the results to the SB Acoustics spec sheet.

Here are two versions of Jeff Bagbys Woofer box Model and Circuit Designer spreadsheet,

First spreadsheet with spec sheet data

Second spreadsheet with DATS V2 measured data

Biggest T/S differences,

spec, factory, measured

FS, 31.5, 37.68

Qes, 0.38, 0.60

Qts, 0.35, 0.54

Vas, 45l, 21.4l

I re-calibrated the DATS v2, to make sure that wasn't the problem. I used the same 18g weight I always use.

I ran them for 1.5 hours with a 31Hz test tone before taking the measurements.

Can someone please point out my mistake, or have any ideas?

This doesn't make sense.

Thank you,

David.

Hey guys

I build a synergy horn using a huge 109x75 horn designed by Don Keele (I actually have the original prototypes).



It uses a JBL 2447 1.5" compression driver and a single 12" Beyma 12P80Fe. Anyone interested in taking a look and making some suggestions? Sadly this was measured inside, and I will not be able to bring them outside for quite a while. I included a google drive link, hope it works: 1 meter vs 2 meter _ sealed vs ported.mdat - Google Drive

At this moment the synergy is vertically alligned, not ideal but at the moment the best option due to size. I measured the right one today. This was the one I built first, and also has a port which fires out from the top over the whole width, very close to the mouth (where the drilling machine lays in the picture).

Any thing you can note from the measurements? Some notes:

-80-17khz right now. I might boost the sealed option to also achieve more output down to 60hz.

- the measurement of the ported option included for reference.

- I'm particularily intersted in the huge change when moving away from the horn. The LF response gets completely 'distorted' Maybe because of the slit being positioned on the top, firing down? At 1 meter the mic would pick up more direct, and 1 meter a lot more would be reflected.

- as mentioned in the REW files, the 900hz XO is only there to block out the peaks beyond the 700hz xo from LF to HF. The crossover from high to low happens at 700hz, with the LF rolling of on its own.

- I calculated a 0.120ms delay based on the acoustic reference option from REW. Is there anything in the files that can confirm the delay is adequate? I doubt its correct though.

I sell the complete set of original transistors to build the A75 amplifier from Thagard-Pass, enough to put together two driver boards, all matched and identified with stickers and numbers. I bought this set from a builder or hobbyist from Australia, it comes with a report from Kansas, apparently there was a buying group which selected a large number of transistors. It comes with an original history report and with the printouts of each transistor and an original from AudioAmateur magazine in which the publication appeared between the end of 92 and the beginning of 93.
The transistors are still in their respective original static anti-static protectors.
After many tribulations, new realizations about sound and its reproduction, I have arrived at my own conclusions. After so many projects I have ruled out the construction of this amplifier.
Interested contact me by private.
Best regards to the gentlemen of this wonderful forum

Hi


I have replaced the output transformer and all the tubes in this amp about 3 months back. It was working fine except for a very slight hum from the speakers. Now it is back with low volume and distorted sound .With the master volume at 5, low, mid and treble at 5, as I increase the channel volume it sounds OK until 3 and above 3, it does not seem to increase much but starts to distort badly. There is not much increase in volume from 3 to 10, but severe distortion. I have checked all the caps and resistors, and they are OK. One side of the plate winding has a DC resistance of 40 ohms, drops 2.7 volts across at a plate voltage of 470 volt. So dissipation is at 31.7 watts per pair. Dissipation the other side is 33.3 watts. It is biased low, but I think this should not be the cause for such low volume and bad distortion. One thing I noted is that when I plug the speaker into the Ext speaker socket, there is no sound. Schematic attached. Please assist.


Thanks

Sorry, this happens on both channels.

Hello,
I'm testing (almost permanently) the following snubber RC filter between plate to screen in UL mode.

Is this a sort of "conjunctive filter" or RCA "corrective filter" ?

Usually should it be between plate and B+?

On simulation it slight increases HF (and "airy" in listening) and not the contrary.
Can you please explain?

Dear All Expert,

My Tektronix 577 curve tracer has been working in the previous couple of years. Recently the CRT beam sometimes come off. Sometimes, I can get the beam appear by switching the switch on collector supply and the test fixture. But, now, I can not get the beam back again.

I think it is the problem of CRT display. Both Collector supply and step generator seems working OK.

Any help will be highly appreciated.

Best Regards

Eric

This is the Gated Impulse measurement of:
Tweeter Focal Audiom TD5
Mid ATC SM75-150S
Woofer Focal Audiom 15 WX

Crossover with Hypex Filter Design at 500Hz and 2KHz
Crossovers LR4 order all of them
Gain Tweeter Channel 0
Gain Mid Channel 2.5dB
Gain Woofer 10 dB

Measurement only reliable above 300Hz (if I've done correctly)
Doesn't look good to me?

I'm looking for a power amp that can reproduce infra-sound from near DC to 30Hz or so. This amp needs to power a subwoofer that is rated at 150 watts RMS into 8 ohms. My research has determined that a direct coupled amp design is the way to go but so far I cannot find a suitable amp. The closet that I have come is a vintage Technics SU-V3 Stereo Integrated DC Amplifier with a FR of 2Hz to 100kHz. Unfortunately it's power output is only 40 watts per channel into 8Ω (stereo). I then thought that I could build an amp on a board but I am having trouble finding a suitable design. Can anyone point me to a design or a consumer amp that can meet my needs?
Thanks,
Scott

I just received this little JLH beauty. Already really impressed with it, but would like to try swapping the output caps for something of better quality.

My JLH is supposed to be "2017 model" with MJ15025 & MJ15024. Looking at schematics online, I was expecting the output cap to be 2200 uF. However - mine seems to be 1500 uF. Would that be a mistake?




Any suggestions as to what to replace i with? Should I go with another 1500 uF or replace it with 2200uF? Any particular brands to look for?

TIA

I have a pair of 18SOUND 6ND430 16Ω woofers for sale.

They are brand new and unused. In the original factory boxes.

Looking for around $180 for the pair and I will ship for free in the USA 48.

PM me if you are interested, I am open to offers that are reasonable.

Thanks

So, I'm building my first DIY DAC with TPA parts, and I definitely want to use an external I2C controller, but I'd rather not have to have a separate control line and electronics or relay to control the DAC reset.

I'm wondering if there isn't a software solution to my problem. I haven't seen anyone propose this solution yet, although it's hard to catch up on many years of posts.

What I am planning is to leave the onboard controller in place, but replace the firmware with stripped down code that removes all of the support for being an I2C master on the bus, i.e. it will never talk to the DAC over I2C.

It's whole purpose in life will be to simply do the initial hardware reset sequence via gpio when power is first applied, and do nothing else.

If I decide that there is something else I want the onboard controller to do with the other GPIO's local to the DAC board, I can add code to make the controller an I2C slave, assign it an address that doesn't conflict with the DAC, and then send commands to it.

What I may do at first (during a transition to developing my own external controller code) is replace one of the current gpio switch settings to control whether or not to enable the onboard controller to be a master. That way I can keep the current code with the one difference, i.e. look at the switch at startup and only talk on the I2C bus as a master if the switch is set, otherwise have it be a reset only controller, i.e. I can still use the onboard controller for it's original purpose when I don't have my external controller being an I2C master.

Has anyone already tried this idea? Does anyone see any problems with it? The external controller (assuming it is in the same power domain) would have to wait the requisite reset time before it should attempt to talk to the DAC.

Hi, I’m going to build a pair of floor standing speaker. I have a certain number of drivers in my hand. They are 0.75" & 1" tweeters, 1.5" dome & 6.5” cone midranges, 8" & 10" woofers. I now have a problem to make a decision of what way I should go, between 3 or 4 ways. These are the sets that I try to match by myself.

3-way;
Tweeter: 1”
Midrange: 6.5”
Woofer: 10”

4-way;
Tweeter: 0.75”
Midrange: 1.5”
Mid-bass: 8”
Woofer: 10”

Crossover points are around 130 and 2500 Hz for 3 ways, and 130, 500 and 5,000 Hz for 4 ways. These are chosen according to the drivers are taken from commercial speakers.

I know that the best choice for most people is 3 way, but as I saw many hi-end designs were 4 ways in 80s. So, I’d like to know your opinion and suggestion. Thanks in advance.

Sold.

Thanks, Don

Hello! In search of an 8" Philips woofer: AD80652/W6, 8 ohm version. Will take a single or a pair. Thanks!

Greetings to all, I am a new user and I am pleased to meet who has my same passion 🙂

Case: both horn and compression driver are unknown model of unknown brand. These were found in 1980s Ecler TRO-120 Speakers. Re=10 ohm, 1.75" titanium diaphragm, dented suspension, axial slots and mixer, 1" exit. Oversized magnet. (fig.1, fig.2, fig.3)

(Measurement: Focusrite 2i2, Behringer ECM8000 on stand, SpecraPlus)

- Unmodified response: brown trace (fig.6): severe high Q dips in HF output (8Khz, 13Khz, 17Khz, 19Khz, 20Khz).

- What starts turbulent ends turbulent: Standing waves can ruin HF horn response (fig.7).

- Horn has sharp borders on cavity perimeter (fig.4). (I suppose the horn is an "eye copy" from another classic model, which includes a bullet piece. Precision in machining suggests China. In practice these borders are creating standing waves at HF.)

- Horn machined to remove borders (fig.5): orange trace (fig.6): 19Khz dip is removed, more low end output, less 14Khz peaking.

Looks very cool!

No idea on the price yet.

I really like the 4 outs, making it easy to XO between woofer and tweeter, or sub with speaker set. If they offer the same kind of plugin that comes with the miniDSP HD, this should be fun!

Great idea! Perfect for a WAW approach.

miniDSP Webshop | DSP solutions ... shd-series

hello my friends!

what do you think about this setup in my new sourround speakers?

dayton rs150p-4 6" and seas ht1396 tweeter

I have a xsim simulation to this and a setup file,if someone want to change my setup.

I have the Problem that the Pre-Amplifier Stage gets hot and burns. What could the reasons for that be ?


Thanks for your answers

I've gone through so many project ideas and drafts trying to figure out what I'd like to build to replace my existing system (SVS Prime 5.2) but I keep coming back to the same basic problem - I need a horizontal matching center channel at 8.25" or less of height. And I don't want to build just any old design either, I want it to be something special in some way. I figure that it's time to flip the script and start from the center design.

I'm looking for fairly wide HT coverage, not one sweet spot. Size constraints mean that I'm most likely looking at an MTM or WTMW configuration (more on that in a second). Some controlled directivity would be nice but I'm not making it a priority. And then there's the problem where horizontal speakers generally don't provide good off axis characteristics. That got me thinking, why not do a design with a coaxial or full-range center, flanked by some woofers crossed low enough to avoid combing/lobing? Then I can use the same design but larger woofers in the towers.

Alright so obviously I'm not the first person to think this and there are some existing discussions, but mine is a little different. I'm planning to make this an active speaker powered by a Hypex 2-way or 3-way DSP plate amp, and I'm willing to put some money in compared to many of the well known DSP designs. Call it...$800 flexible ballpark for amp, driver, misc non-wood parts, less is appreciated. It seems like it's hard to predict the behavior of coaxial drivers from the spec sheet charts alone, so I'm looking to drivers that are known to perform well but could really be cleaned up with some DSP.

From here I need some help putting me on the right basic track for reading/research/planning. What would be some good drivers to consider? What woofer xover point am I aiming for to avoid off-axis issues? I was thinking of using the Seas clear-cone seen in the Loki design. (Although the simplicity of the xover in the Loki calls into question whether an active biamp is really useful here.)

Any information or input is appreciated, particularly comments that get me closer to a highly performing but unique speaker.

Dear DIY Friends.

I just purchased the book written by Mitch Barnett :

Accurate Sound Reproduction Using DSP.

This book was recommended to my by a french person on a french audiophile forum.

I have a hard time understanding what "exactly" I need to start following the mesurements in the book ?

What I have is this :

PC AMD A6 6400 k APV with Radeon HD Graphics 3.90 GHz
8 GO RAM 64 BITS with a Solid State Hard Drive.
I have a simple Xonar Sound Card ASUS Xonar Se Interne 5.1 canaux PCI-E - (5.1 canaux, 24 bit, 116 DB, 110 DB, 24 bits/192 kHz, 0,00251%)

Windows 10
RME Digiface USB
2x Alientek D8
2x Line Array speakers with 12 medium and 21 tweeters each one
I need to buy a microphone but the one recomended in the book
Behringer ECM 8000 only costs 30 euros/USdollars.

Is this a good mike ?

I also need a mike pre amplifier, what should I purchase ?

and a Sound Level Meter,

I will buy the Galaxy Audio Check Mate CM 140

Then the book says :

Acourate (le logiciel) uses ASIO as the audio driver and protocol to communicate directly with the sound card or external Analog to Digital, Digital to Analog (A/D D/A) converter bypassing windows audio subsystem. It is recommended that the A/D D/A converter employed use an ASIO driver, typically supplied with the A/D D/A converter, ASIO4ALL can be used if one's converter does not have an ASIO driver. The recommended default sample rate value for taking acoustic measurments should be setto 48 kHz.

Whaoo, this part makes me a little bit confused.

Is there anyone that can help me ?

After the initial setup has been done,

I feel that looking at the book that

this is feasable, although I am not a technical person.

I will try.


Hope that you are all well in spite of the viruses.

All the best, Raymond.

Does anyone know where I can get aluminum ribbon assemblies for Decca Kelly/London tweeters, as shown in the attached image?
The aluminum ribbon in one of the tweeters has rips on the edges
I've tried to email few people from England and Germany who sell these assemblies on their website, but have not heard from them
Alternatively, please let me know if you have the tools to make these ribbons
Thanks!

I bought a Pathos Aurium Headphone amp/preamp. It’s rated 12V 5A, question is is it possible to use anything more powerful than a 12V power supply? Say, like the 24V Meanwell power supply recommended on diyaudio store?

I’m no expert. Does hifi equipment adapt to “overpowered” power supplies? I want to upgrade the power supply on my TC Electronic BMC-2 DAC too, and that is rated 12V 1A.

Please help me decide. Better to stick to 12V as recommended, or diminishing returns on changing stock for something like 15V power supply? Thanks!

Hi Gentlemen,

I am finally getting around to building a pair of the Wooden Design Redeye speakers which use a single Aurasound NS3 driver. I have the drivers and understand the plans, but am unclear about the damping scheme. The design specifies where the damping material is to be placed and says that Ultratouch 1/2 inch or equavalent material is to be used. I'm wondering if 1/2 inch parts express sonic barrier iowb cekk foam is OK to use since I don't have quick access to Ultratouch 1/2 inch. If not, what is an equavalent material available in the USA?
Also, since the last manifold entry point at the top of the speaker is only 1 inch tall, wouldn't putting 1/2 inch of either Ultratouch or sonic barrier foam overly restrict air flow even though the entry point is 4 inches wide?
And one last question, how does one, "adjust from there if needed." I am eager to see how this design compares to my Pico Neos which use the same driver in a bass reflex cabinet.

Thanks!
Jay

In the early 2000s, I worked at a large factory, where they introduced the Western ISO9001 management system instead of the previous enterprise standard, which had been operating at this factory since Soviet times. I was responsible for this implementation of ISO9001 in the sales department, in which I worked as a boss. What was my surprise that most of the points of ISO9001 almost coincided with the old Soviet standard of this enterprise. For example, a clause about a response or invoice being sent to a purchase request should be sent to the client no later than 3 days, etc. the coincidence was approximately 95%, it was simply written in different words and slightly different in nuances.

What was my surprise when later working at other enterprises, I was faced with the fact that in the West and especially in Japan, less often in Taiwan, many companies absolutely did not meet the requirements of ISO9001. I agree that it can be argued that not many companies for various reasons can not allow or do not want to have such an ISO9001 certificate. But it’s obvious that it is possible not to have such paper, but it is quite possible to observe elementary rules, such as in the case that I described earlier, where there was my own internal enterprise standard, which practically did not differ from ISO9001. On the other hand, it should be noted that many companies in the West respond to the request very promptly. Especially German and American firms. A logical question arises, what can be connected with a low production culture? By the way, my suspicions were confirmed after I received samples, products of various companies, and those companies that responded as quickly as possible had the best quality products. With the exception of Japan, where product quality may be high, but there are no answers for their reason, obviously Japanese chauvinism. Those who want to argue with this, let them first analyze what components are used by Japanese manufacturers. In serial production, only Japan-made components will be used in 95%.

But returning to the topic of operational communication with customers, I can definitely say that the higher the quality of service, the higher the quality and products, too. Moreover, I think that not only in industry but also in the service sector is such an analogy visible, for example, in restaurants.

Hi!
I just received (bought) a complete kit of Millennium Xp amplifier from Lc-Audio. But... I can't use it...

I discovered, as you can easily see from the joint schematic, that the input impedance is 2K !! Yes, 2 KOhm!!

Now, I have a simple valve preamplifier, SRPP with a coupling capacitor of 0,47 uF..... I have big problems:
first because the gain of this stage has hardly decreased from this low resistence,
secondly because It cuts all the slow frequency!
I calculated, I need at least a coupling capacitor of 20uF (!)
Too big, to expensive a good one, and too poor will be the sound with this big capacitor.


Now, my questions:

1. Is it possible that the big (really) Lars Clausen, has made a circuit of a PWA with only 2 KOhm input Z? No Power Amplifier has so low input impedance...

2. According to who is so kind to help me, is it possible to increase this input resistance up to, for example, 20-50 KOhm? What will the consequences be?

3. You know what is the gain of the VAS? Because LC audio didn't decleare it on their "cook book"...

4. Any other suggestion?

Thank you very very much in advance.

P.S. I already send TWO e-mail to LC-Audio, of course, but after 10 days I didn't receive ANY answer. It's odd, but It is.

Hello all,


I've recently built ESP / Rod Elliott's P101 Lateral Mosfet amp. The listening impression is simply amazing!
However, as I also want to quantify what's amazing, I decided to do a couple of square wave measurements using 1k, 10k, 20k signals, and then doubts arise.
Please see attached. It's one channel measured directly with the square wave at the input.
What worries me, and can't find yet an explanation is the overshoot at the bottom, and the fact that the amplitudes do not match between the upper and the bottom part.
The power supply was checked, and it's within 0.1V (+ve and -ve supply rails). Input signal is also to be trusted, it's generated by the scope, and I've checked before with wavegen linked to the input, and what comes out is perfect.
Output devices are Exicon 10N20/10P20 pairs, two of them (populated the whole board as in the high power P101).

I've also tried to simulate the schematic with models from Exicon, and it presents the exact same behavior, therefore I think that something needs to be adjusted.

Any ideas why is this happening?

PM me if you have a pair or more 🙂

Hello you all,
I'm working at the project of the pictures. It's a current amplifier with no feedback able to provide 1W to 600 Ohm load with 0,04% of distortion. It can provide till 3W with 0,08%, so it can be used also for high impedance speaker like the famous Philips 9710.
The circuit is based on two part:

1. V-I converter
2. 6 time current multiplier

In other words, the amplification is due a mirroring of the the original signal and this allow to the circuit a very low distortion without feedback.

Comments and advice are welcome

Hi guys!

I just joined the forum! I am looking for some advice on the construction of a concrete speaker for a design project. In short I am studying engineering and for one of my courses I want to design a speaker using concrete. I already know how to create curved surfaces in concrete but I also want the speaker to sound somewhat decent, or at least design the shape that way. The choice of a subwoofer is based on the sole fact that there are less variables to consider. It would be a passive subwoofer and the budget for the driver is less than 100€.

Any help on specific parameters i should take in account for my build? I want to collect some theoretical background on sound engineering to support my design choices. I'm all ears!

cheers, Nathan

I have a Sansui A80 amp that has a strange issue (to my mind).
I've replaced the PS caps and when I turned the amp on through my dim bulb, the lamp stayed bright. I noticed that the speaker switch was on and when it was turned off the lamp dimmed. When I turned the amp on with the speaker switch off the lamp dimmed immediately and didn't brighten after the speaker switch was turned on.
The other issue, which may be associated is when the amp is turned off and after perhaps 10 seconds there is an echo-y thump from the speakers. I know that I can get around the problem by turning the speakers off first but it seems to me it shouldn't be like this. Any ideas please?
Regards John L.

I have 2 bits of 25mm thick perspex here, one is circular and is 303mm wide with a 7mm hole in the centre, the other is square and 300mm. The circular one was going to be used as a turntable platter hence the hole in the middle. It would need some more machining but gives you a start.

Circular piece - £20

Square Piece - £10

Delivery is £7 each (or both packaged together

Hi All,


I've been intrigued by class D as of late and I'm thinking of making a couple boards up as an experiment. The NXP TDA8953/54 seem to be the most powerful monolithic ICs I can find but I'm having trouble dissecting the schematic. There are a few things that don't makes sense to me. Attached is a screen shot of the schematic with some features circled.

• Purple: What is the purpose of coupling the outputs to the supply rails? Is it to make PS noise common mode at the outputs? Would CVP1 and 2 be serving a similar purpose?
• Green: Is there a reason these caps need to be terminated to the negative supply rail? Would terminating them to ground be any different functionally? Maybe I missed this in the datasheet.
• Yellow: Since the inputs are AC coupled and there are no requirements for setting DC bias on these pins can I assume the inputs self bias? Is this common for class D chips?
• Orange: RVDDA and RVSSA seem to serve no purpose becuase they terminate back to the power supply bus (VDD and VSS). It looks like a schematic error (I checked some of theri other chips and it is the same) should these be dedicated for VDDA and VSSA?

'


As an aside, is anyone seeing a difference between TDA8953 and 8954?



Thanks,
Brian

This is a massive bearing from the biggest deck in Rega's product line up at the time. If you are wanting to build a similar mass loaded turntable and are wondering what to do about the bearing, then this is the bearing for you.

£40 - bearing inc delivery

An unused Rega RB250 for £120 inc

£5 postage in UK

Bought for a turntable I never got round to building..

Deall forum members,

after having finished my little Class-D project for the kitchen's "hifi" - I'd like to move to a new project.

I have 2 matched pairs of Ulyanov 6C33C-B (6S33S-V) tubes, so 4 tubes alltogether. I got them from my father, he's a big EL34/KT88 builder but these are some different animals and I thought I give it a try here and ask if there're ANY special considerations we need to take into account when building a stereo amp with these. I would like to make him a stereo integrated amp for Xmas 2019, a good one.

Tubes are new. If they're matched pairs REALLY - who knows, anyone can state anything on the internet, right ? Anyway, the stamps on the glasses are matching. They're here and I'd like to get some really great triode sound out of them.

I read some issues regarding these tubes about reliability, or at least - put it that way - the quality spread seems to be big. What's the truth behind that, shall we be worried ? These tubes are easy to get cheap here from the neighbouring country, Ukraine, nevertheless I'd like to employ some basic protections in the circuit, either in the design itself or using a small microcomputer (like an Arduino) to monitor current, voltages, power-on hours and setting/modifying bias automatically, or even turn-off the amp via relays if that's the case. Maybe you have some basic hints what we need to take into account with these tubes .. ?



Design considerations for now:
- we read the article with Tim Mellow's OTL design but we think we might stick to a good old classic design with OT which doesn't stress the tubes at all.

- I'd like to have a good, reliable, great sounding Class AB, 2 tubes per side in pushpull, toroidal OT (from Transformatory toroidalne - Producent transformatorow Toroidy.pl) calculated into 6+ Ohms (8 in reality but most 8 ohm drivers go reasonably below 8 Ohms in reality so we design the OT to 6 Ohms then and using the amp with nominal 8 Ohm speakers) and then it should be fine. XLR inputs, fully balanced design with good common mode noise rejection - that's all I have in mind right now.


My question rather focuses on reliability, stability and longevity but if somebody has an already-finished good schematics, go ahead..

Hi!

I think I need some help, because I feel frustrated. Where to begin? As the title says, I am not satisfied with my system's high frequency reproduction. When listening, the high frequencies always calls attention to itself over the rest of the range. I can attenuate any part of the high frequencies of the speakers (thanks to the DSP) but then the sound becomes dull, airless etc and still hearing "anomalies" that is not natural to my ears. Like ssss, ccc maybe a little lower frequency thsss. So overall, like a high pitched sibilance

The problem appears in the higher range, clearly not in the crossover region which is acoustical LR4 at 2100Hz now. The worst range is maybe 6-7 kHz and up.

The midrange driver cone-break-up around 4-5 kHz is well attenuated and EQ-ed out (ok, I know the time domain problems of the break-up either), so I don't think that is a problem.

As I sit closer to the speakers for less room effect, the main signature remains unchanged.

The system is a Hypex Fusionamp based 3-way (analogue or digital input, it doesn't matter). The problematic range comes from a pair of Scan-Speak D3004/6600. Previously a SEAS 27TFFC was used which was (audibly) clearly worse than the SS Illuminator but the problematic range was lower in frequency if I remember correctly.

In other (commercial) designs I heard the 6620 version of the Illuminator dome and the sound signature was similar. Even the Classic D2905/9700 was very similar with the overly shiny, fake, piercing top-end (as I heard).

A very good tweeter sound I heard was some B&W metal dome, but the influence of the metal membrane resonance was audible with certain sounds.

Maybe it's possible that I'm overreacting or draw false conclusions but for example the usual Multiplex cinema I go to, I really like the overall sound where nothing sticks out of the soundtrack.

So what can I do to get better treble? Do you think the SS tweeter simply is not for me? I can not think of anything else. But if anyone has any other idea, I'd be happy to.


Thanks!
Denes

Does anyone have one?
cheers

Since I stopped using KT88/KT120/6550 etc, I no longer need 800VCT.

Small dent as in picture.

$120 or best offer.

I recently acquired a pair of B&W DM602s2 speakers. Like seemingly most of these, the original metal dome tweeters had been pushed in. One of them wasn't too bad and I was able to remove the diaphragm and get the dome mostly back into shape. The other was much worse and is in fact torn. Replacement diaphragms and complete tweeters are listed on the B&W site, but are no longer available. Ebay has produced nothing but a bunch of similarly damaged tweeters, mostly at exorbitant prices for something that is basically a paper weight.
For those not familiar, these speakers are generally well regarded but are sometimes considered a bit "bright" on the top end. They are an 8ohm speaker with an SPL of 90dB@1W/1M. The 7" bass driver is 8Ohm, but the tweeter is a 4Ohm, with a 3.4Ohm resistor on the crossover. The crossover is at 4k Hz.
I found a site with tested parameters of the DM60xs3 tweeter which is very similar to the s2 models.


BW Bowers Wilkins Tweeter Loudspeaker Measurements and Information


I would like to use these from Parts express as replacements. Hoping the slightly lower efficiency might resolve the slight brightness of the original tweeters and bring these back to life.


https://www.parts-express.com/pedoc...me-neodymium-tweeter-4-ohm-specifications.pdf


These are another option I found that is relatively simple for me to mount:


https://www.parts-express.com/pedocs/specs/275-053--dayton-audio-ND25FN-4-specifications.pdf


Any input would be appreciated.


Thanks,
Speedmadness

Hello Gents,

I would like to build a metronome style cabinet for Alpair 10.3m and 12p ( I already have a pair of each). After much digging around on this forum and other places, I haven't found specific dimensions for alpair drivers. I have been to frugal horn's metronome page and checked out the table, but I don't understand how to calculate specific dimensions for the alpairs. Is it as simple as matching similar size driver for example: build the cabinet for Fostex 207 and mount the alpair 12p or are there enough differences in drivers that the dimensions of the cabinet need to be specifically matched to each driver? If the later, how do I calculate this (bear in mind my math knowledge is about algebra 2 level with a touch of geometry and no trig and 15 years rusty).

I've already built a super pensil 12, and will probably do a quick and dirty sp 10, and maybe a frugal horn too for comparison. If the sound of either of those is significantly better than the metronome, I may stick with the sp/fh, but the WAF of the metronome is huge. To quote the wife when I showed her a bunch of pics of some gorgeous pensil style cabs and a simple metronome: "Those just look like speakers. The metronome looks like a nice piece of furniture."

I have an Audio Innovations s300 that I really like.
However, the gain is too high using a 2V line input. I just move the pot from the intial 7 to 8 o'clock positon and it's already too loud.
Besides using resistors before the volume knob to attenuate, is there a better way to reduce the gain?
Please see the attached schematics of the amp and preamp section.
It'a pp ecl86 with no feedback. I hope those familiar with tube amps could provide some advice. Thank you.

Been lurking for a while. Trying to troubleshoot some issues. Seems like a knowledgeable group, so I finally decided to create an account.

- Geraux

I ordered about 20 Pcb's for a LM555 based turn on delay, more then i ever need.

So i am selling the PCB's with a BOM and Schematic included. Or alternatively built and tested boards.



Function

The boards can be powered from 6.3VAC, once 6.3VAC is applied the relay will close in about 30-40seconds (trim-able with an on board trim-pot)



There is a footprint for a second relay, So you can switch dual mono supplies with this boards, i can supply a second relay.



The relay will switch 300VDC 440VAC and is rated for 15A.


The boards measure 49x100mm and have M3 mounting holes on 40x90mm
Connections are made through industry standard 6.3mm Fastons.



Attached you will find a schematic of the board.


Assembled and tested boards: €15. and a single PCB for €2.50



Shipping: EU only, for international DIY'ers you can ask me for the Gerbers. and i will send them to you for €1

Hello,



I'm new on this forum. I'm not an expert. I like tubes and most of my builds are simple SE tube amp. How would you ground the attached schematic ? I've seen many different layouts online. Would you add an artificial CT at T2 primary ? Should I ground the filaments 24V secondary or keep it floating ?



Tubes are in series (12A5, 6SF5, drop voltage resistor), full wave rectifier, 3-prong plug


Thanks in advance
Pat

I'm following a set of instructions to upgrade caps in a preamp.
The electrolytics I have sourced have a 2mm lead pitch, but the space on the board is a larger 10mm pitch.
Is it generally OK to bend leads 'flat' to the PCB...or can the (small) electrolytic 'fly' above the surface using a more gentle bend??


Should the replacement component pitch be closer to the available PCB pitch is what I'm asking I suppose! 🙂

Can someone help me with .zma & .frd for SS 18W/8545-00?

Hi, First time posting here.

I bought a bunch of All American Five radios with the idea of gutting them, essentially just keeping the vintage shell and the chassis. And then building a small 1 or 2 tube amp with bluetooth input. Basically a vintag-y tabletop bluetooth player for gifts. (Yes I realize that it would be cheaper, easier, and probably sound better if I bought a bunch of Chinese class-d amp boards, but my friends all know I build tube guitar amps, and I can't go around giving them all guitar amps!). I don't need more than 170v so I can use an admittedly-inexpensive 120/120 transformer and a solid state rectifier, but then I got thinking....

First of all, I totally get why the AA5 design was a safety disaster, and I get why iso transformers protect the against the situation where the presumed-neutral wire shares a common ground with the circuit (because it may in fact be hot). But...

If the picture below represents my design without a transformer, what is the advantage of putting a transformer between A-B? I'm trying to understand the scenario where the transformerless design is less safe. Are there other considerations (noise, etc).

It seems like heresy to ask these questions. I got my head taken off over at a guitar amp forum just for asking, and never got an answer that I could understand. I'm happy to do it "just because" (which was the answer I eventually got), but I really would like to understand.

btw, someone will ask "what about the heaters?. I have no interest in stepping wall voltage down to 6.3v with resistors, zeners, mosfets, or capacitors - too many issues there - so I will get small 120/6.3v transformers for that. I'm just wondering if I can keep my "iron" to one inexpensive transformer.

Thanks. Be nice.

Just finished my first amp project, Walton audio 300b mono block and it sounds great. On power up, I get a lot of popping and hissing that goes away after 5 to 10min and would like to know if a time delay would help this? Not even sure what one is, just have done some reading on them.

Thanks

Sale:
6B5 Sylvania - 2 pc. for $16 ea.
6C4 - 3 pcs. for $8 ea.
6F6 RCA - 1 pc. for $8
6F6 Ken-Rad - 1 pc. for $8
6F7 Ken-Rad - 1 pc. for $8
CRC-6J5 RCA - 1 pc. for $8
6L6 RCA - 1 pc. for $16
6L6G RCA - 1 pc. for $22
6SN7GTB GE - 1 pc. for $22
CRC-6V6 RCA - 1 pc. for $8
25L6GT Sylvania - 1 pc. for $16
42 Purotron - 1 pc. for $22
42 Radiotron - 1 pc. for $22
80 Ken-Rad - 1 pc. for $22

For cleaning mechanical switches I normally use KONTAKT 60, followed by a flush of KONTAKT WL.
Normally, this works O.K.
Recently, after some time, the treated switches again had contact problems.
Then I used WD40, and the switches seem to stay O.K., also after several days.
Is WD40 really a good contact cleaner?
I had succes with WD40 with a Onkyo and a Kenwood amplifier.

im looking for a high efficiency tweeter that can tolerate a first order xo centered around 3khz for use with the audax pr170mo mid.

the efficiency to match should be over 95 db

The only tweeter i found that can work would be the seas t35
SEAS The Art Of Sound Perfection

what are my other options?
thanks!

Hi,

I'm looking for some something to fill my 18" Mogale Super Scooper but with coronavirus and shipping/production from the EU times are tough. The PD1850 and Void 1000 are both made in the same place and I would like to finish my project during this down time.

Can anyone suggest a worthy replacement that is available in the US? Even better would be in or near NYC. Inventory from US speaker could suffice if they have the part.

Thanks!

Does anyone have a source for Philips/Signetics NE5532As in DIP form? I could probably also use an ON Semi one if in DIP form. I'm trying to avoid the T.I. chips and their renowned distortion compared to the originals.

SOLD
Up for sale are two complete assembled Gyrator boards from Bartola.
They are ideal for low current DHTs like 26 and 01A but other tubes also can be used but please consult Ale from Bartola valves!



All the parts used are high quality! I will include also 0.1uF obbligato 630V film caps! I used matched 2sk170BL transistors also!

Price: 35 USD / assembled board

For actual pictures of the boards please send me your e-mail.

I am shipping worldwide!

Can you help with 4k5 class d amplifier limiter clip peak circuit

I worked on a Rockville amp yesterday and found that both of the output inductors were cooked. I haven’t found any other damaged components in the amp. It looks like a very new amp, less than a year old.

I know that vibration damage is a major factor for these inductors to fail, but I’m not sure that vibration caused this failure. What else could cause the output inductors to cook.

David

I have a Taramps HD 8000 on the bench that has significant ringing on one side of the output transistors, and uneven voltage on the speaker terminals. I’m thinking the the higher voltage present on the positive terminal is be induced by the ringing. I tried wiggling the output inductors for both sides and it didn’t affect anything.

I’m getting 176 volts rail on both sides, but I’m suppose to get half rail voltage at the speaker terminals. I get 88 volts on the negative terminal and 96 volts on the positive side. I see these same voltages at the output mosfets as well.

I am attaching screen shots of the drives on each side.
Scope settings are 5v 10us probe is set to x10.

Has anyone seen this before? Suggestions?

David.

Hello all, I have an old pair of heath amps, usually I'd be on here blathering on about issues with the Power amp, an AA-121 (EL-34 PP stereo)- but now I am going to blather on about an issue with the matched preamp.

The Preamp is an AA-141A unit and what has happened is that I lost plate voltage the other night running the tuner quietly.

After poking around with the meter, I have determined that the B+ tap on the power transformer has gone open. Must've popped the winding. It still powers up and I have filament heat and a pilot light on the front, so I know that at least the 6 volt taps are still working, but that doesn't amount to a **** hole in a snow bank without voltage on the plates.

Now, the heathkit part number on the top of the xfmr is 54-71, and after googling around I have come up with zilch, so I may have to order an aftermarket unit.

The question is, what the hell am I looking for. I've never had to buy a transformer before.

With a designed input voltage of 117VAC I have 2 6.3V taps for the filaments and a 238V tap after a couple of Selenium diodes for the B+ supply. I never had a meter on the winding while it was working, so I dont know what the actual voltage on the winding was. These numbers are "what I should have" according to the schematics.

What does having a transformer re-wound usually cost?

Let me know if you have one for sale.

Hi,

I would like to know where I can find the Denon DN-951-FA Calibration Procedure, I have a unit with the 85 ERROR in the front screem all the time and I read that is due to necessity of a calibration procedure.

Any idea?

Thanks anticipated

Hello,


I picked up this solid state Marshall Mosfet 100 guitar amp for $5.



It obviously didn't work when I brought it home. It would make sound and seemed to work until I inch the master volume up past three. Then it just squeals and makes robot noises.


After messing around with it, I discovered that If I put a jumper between the circuit ground and the chassis, it would work perfectly. No squealing, no robot noises, just guitar noises.



I checked the voltages across the filter caps, and when the circuit ground is disconnected from the chassis, they go wild. They overshoot the rated values, and are crazy volatile. When the ground is connected the chassis, they are nice and steady. It does use a bipolar power supply. My current hypothesis is that the circuit ground has no reference to hold it at a steady 0 V, so it goes all wild until connected to earth ground? I don't know enough to know anything for certain.



I'm glad I figured this out, but I have no idea why this fixes it. I also have no idea what had been done to it before I got my hands on it.


If anybody understands why this happens, and why connecting the circuit ground to the chassis fixes it, please let me know. I want to learn.

Anyone interested in these HQ 25W Class A modules. They are really quite good.

They do need large heatsinks and +/- 24V PSU.

Hi guys,
Does anyone recognize this device?
Regulated voltage stabilizer with E130L pass device(ef83,ecc283 plus some OA2..)
Unfortunately,there is no labeled anywhere.But looks like professional,with some germans inscriptions.
I appreciate schematic,tech. manual or any info.
Many thanks,

Hi Folks;

New to audio forums, but not forums as a species. Have finally returned to my (audio) roots. Stuck in the '70's and '80's, so don't beat me up too bad. Seem to have an affinity for JVC and Technics, but am constantly on the lookout for anything kinda cool. Of course, being car-poor, it squeezes the budget. I have waaaay too many cars. But, I digress.

Anyway, happy to be here and will try really hard to not make a fool out of myself. Remember, newby on the premesis...

Thanks to all,

Mike

Hi diyaudio world. i need help & guidance.
i want to make a dedicated stereo tweeter amplifier
& active crossovers. As you have guessed; i have very little knowledge about active crossovers, related equation & math.

i want to use tweeters with my sealed woofers
(not sub woofer). i'm currently using lm3886 stereo with those woofers without any active crossover.
The frequency response of my woofers is good upto 2-3Khz approx & that is just my guess because the manufacturer didn't provide much information about those woofers. Actually i don't need high level accuracy, just good music 🙂

For tweeter amps i'll use chipamp like 1875 or maybe tda2050 but i need help to make active crossovers for
tweeters. A good schematic diagram & some advice
enough for me.
as much as i know-
1)Sealed box exhibit a shallow roll-off of about 12dB/octave compared to bass reflex with 24dB/octave roll-off slopes.
2) sensitivity of tweeter & woofer should be same or at least very close.

i have some ne5532 & tl072 op-amps in my hand & i want to use them. i hope I've been able to explain my problem 🙂

I guess Im stubborn, chose a material with an unknown expansion rate. 3/4" Bamboo board. One site says it has alot of movement, another says its pretty stable.

As this is only the outside of the enclosure, I planned on lining the interior with another layer of 3/4" ply or 1/2" MDF.

I know if I simply glue the interior panel to the bamboo, the boo will eventually split from shrinkage. Even if it is stable, I doubt it is as stable as MDF or plywood.

My plan is to run a bead of adhesive down the center of the widest panel on the inside) (its the side panels and 1'3" wide) and leave outer edges of bamboo to more or less slide against the interior panel (that will be cut 1/4" narrower) I was thinking of may be a few dabs of silicone in the corners between the 2 and or may be adding a slot in the interior material and snugging up a screw with washer so there could be a little movement.

Beyond that, Im not 100% sure, has anyone here worked with dissimilar materials and accounted for movement ? Curious how you did it !

Hello All.

I built a Decware SE84CS based clone a few years ago and was intending on documenting the build and posting photos but never got around to it. I came across the photos on my hard drive a few days ago and decided to finally do it. I, like many others, have a lot more time on my hands than usual...

Folks, are there any replacements for the above mentioned tubes?

I did a search on them, wasn’t able to find anything. My preamp is using them, wanted to buy a spare set, but there’s virtually nothing on the web.

Thanks in advance.

I have an out of warranty Behringer Inuke 1000DSP with a faulty B channel.
If I attach a dummy inductive load to the B channel, the unit will initialise when I power on the unit with the A channel stabilising and channel B tripping. Has anyone any ideas where I should start looking?


Thank you

Hello,

I have the following audio tubes for sale. More will be added from time to time. If you have any questions or would like a shipping estimate please feel free to PM me. Thank you.

For sale is a pair of Amperex 6DJ8 ECC88 vacuum tubes. $35 plus shipping. Both tubes were produced by Philips in their Heerlen, Holland plant and these pair of tubes have the code sequences of GAO delta9H3 and GAE delta2G4. Both tubes have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142 tube tester. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1:
Triode 1: 101%
Triode 2: 102%

Tube 2:
Triode 1: 101%
Triode 2: 102%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube by one step and noting any significant reduction in emission performance. These tubes performed very well in this regard.




For sale is a pair of Tung Sol 6V6GT vacuum tubes. $35 plus shipping. These tubes feature brown bases as well as smoked glass. They are in very nice shape save for a minor crack in both bases of the tubes. These can be seen in the first and second photo. These do not seem to affect the structural integrity of the tube. These tubes have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142 tube tester. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: 90%
Tube 2: 91%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. These tubes showed some reduction in emission but this reduction was not excessive.




For sale is a pair of General Electric 12AX7 ECC83 vacuum tubes. $25 plus shipping. Both tubes, although the first is labeled Zenith, were manufactured by General Electric. These tubes have been tested for shorts, grid leakage and emission on a Sencore TC-142. The results are as follows:
Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1:
Triode 1: 101%
Triode 2: 100%

Tube 2:
Triode 1: 90%
Triode 2: 91%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. The first tube showed no reduction in emission whereas the second showed some reduction but this was not excessive.




For sale is a pair of General Electric 12AX7 ECC83 vacuum tubes. $35 plus shipping. These tubes feature long, grey plates and halo getters. They have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1:
Triode 1: 97%
Triode 2: 98%

Tube 2:
Triode 1: 99%
Triode 2: 99%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube by one step and noting any significant reduction in emission performance. Both tubes performed excellently.




For sale is a pair of RCA smoked glass 6V6 vacuum tubes. $30 plus shipping. These tubes have the date codes of "57-43" and "58-30". These tubes have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:
Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: 92%
Tube 2: 98%




In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube by one step and noting any significant reduction in emission performance. These tubes performed very well in this regard.


For sale is a pair of Sovtek 5881/6L6WGC tubes. $30 plus shipping. Although one of these tubes has been labeled by Mesa they were both manufactured by Sovtek in Russia. Both tubes have coin bases and two flying saucer getters. They have been tested for shorts, grid leakage and emission on a Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emissions:
Tube 1: 93% Tube 2: 94%

Both tubes have had a life test performed upon them which involves reducing the filament voltage fed to the the tubes by one step on the tester and noting any drop off in emission. Both tubes did extremely well in this regard.



For sale is a General Electric 5 Star 5751 tube. $20 plus shipping. These 5 star series tubes were part of GE's "High Reliability" line that were manufactured to tighter tolerances and with better materials. This tube has black plates and has triple mica construction. It has been tested for shorts, gas and mutual transconductance on a Hickok 546. The results are as follows:

Shorts: PASS
Gas: PASS
Mutual Transconductance:
New = 1250 umhos
Tube 1: Triode 1: 1000 umhos Triode 2: 900 umhos




For sale is a RCA 5751 tube. $15 plus shipping. This tube has black plates and a halo getter. It has been tested for shorts, gas and mutual transconductance on a Hickok 546. The results are as follows:

Shorts: PASS
Gas: PASS
Mutual Transconductance:
New = 1250 umhos
Tube 1: Triode 1: 1000 umhos Triode 2: 1100 umhos

Hi Everyone,


Since I am stuck at home in lockdown, I might as well repair amplifiers 😀.


I am currently trying to repair a Nad C315BEE. It stays in protection mode.



I replaced some dying capacitors in it as a first step. Most of the capacitors located near the heatsinks were obviously dead.


The thing is... it still stays in protection.


I cannot find anything wrong with this amplifier : power supply rails are all working, no shorted transistor...


The only thing I can see: it does not amplify anything.


I use a smartphone with a signal generator application.
560mVpp coming out of the phone, 400mVpp going into the power amplifier (and coming out of the preamplifier), 180 mVpp coming out of the power amp with a heavy distortion.
Both channels behave in the same way.


I am kind of puzzled right now...



I have seen another thread where the owner had to replace the protection circuit, but I assume that even if my protection circuit is bad, the rest should be working?



Any thoughts ?

Hi folks,

I have a pair of ScanSpeak 22W/8857T‘s on hand and was looking to build a center channel with them, but I feel they’re too big for my use so I’d like to buy a pair of 18WU’s (either four or eight ohm version will work.

Selling the 22W/8857T‘s for $325 for the pair plus shipping. They’ve barely been used, they weren’t the right driver for my project and are leftovers.

Russ

New member and was directed from another forum to ask the experts here.

I can answer question as needed so I don't want to make this a long first post. I want to provide correct information and don't want to fill this with irrelevant data since I'm new at this.

Rebuilding some 1990 speakers and used Clarity CSA capacitors. I replaced the outer rings on the woofers as well. D'appolito style Clements 206di.

OK now the sound prior to the rebuild was very warm with great mid, lower frequency spatial qualities. 30 years on the caps and the repairs on the outer rubber rings pushed me to where I am today.

Doing a frequency sweep confirmed my observation while playing the modified speakers. Tonal balance seems to tip upward and mid/low tonal volume around 100-120 hZ, to be exact 104-108 is the low spot.

Is this the sound signature of these caps? Thanks in advance!

I hope this post finds all of this community safe during these troubled times.
Music has certainly done much to keep my spirit going.
______________

Sheltered in place, I have a bit of time for the next set of optimizations of my speakers.

Background

I have configured a pair of Hypex Fusion FA123 plate amplifiers using the Hypex software. I have now tri-amplified my speakers & they sound great or at least better in almost every respect to the prior iteration of the system.

I have currently set up 2nd order crossovers.
I have had it suggested to me that 4th order would work even better, but I frankly don't have a clue about implementing them with the Hypex amps.

Any suggestions or context about trade-offs one way or another appreciated.

Equalization

I do think I have something to gain by applying the Hypex equalization capabilities.

To prepare to do this, I have assembled the following:


What do I do now?

Clearly outside my knowledge base, but I have the time to follow guidelines and do any required research.

Any guidance appreciated.

Happened to mention to the nurse at my local health centre that I had a pile of sound equipment sitting here that could be used for announcements and did they think it would be of help, immediate response was YES PLEASE, we are trying to get a message out that the chemist is closed for 2 hours each day, that would be a massive help.
So sat here now putting together what I can for a portable system and another to go on my shed roof in the middle of the village, also volunteered to try and help get as much sorted elsewhere in my local area as possible.
Just maybe something useful we can do with all this kit sitting around doing nowt.

Hi all,

I am working on an Aragon 8008BB. One channel blows the negative fuse on power up a few times. I have verified there is no short in the power and speaker wiring and then taken out the assembly (PITA!!) and desoldered every power transistor and bias transistor and tested them. All junctions tested fine and I tested the driver transistors on the board for diode drops and they look fine too. Did that to the pre-drivers as well. Bias pot tested in range.

Not able to find any smoking gun, I want to get everyone's thought as to what else I should look at before I put it back together and most likely go back to blowing fuses.

Thanks in advance!

PS. Measured power supply voltage at +/-74V with the fuses not installed. The other channel works fine.

Hello everyone!

Thanks to all of the useful information from you guys, I was able to narrow down the problem on my 6N2/EL34 kit amp build to the output transformers. I had installed both of them backwards due to the lack of markings and the fact that the winding connections to the poles were covered. I should have probably tested them with my multimeter retrospectively, but an oscilloscope and sample tone helped me figure out and rectify the issue.

My amp now makes sound, however there is a constant hum present on one of the channels, even when there is no audio input connected. I swapped both of my output tubes and the hum was present on the other channel, so my tube might just be bad. I’ve ordered a matched set, but I am quite concerned about my heater voltages. The 6.3V tap from my power transformer reads 7.3 volts and I’m sure that’s the cause of all of the tube/hum issues.

Would it be a better idea to put a 1 ohm 10w resistor between the transformer and the filaments, or build a 5A DC regulated power supply (probably based on the LM317)? Also, my amplifier has the filaments directly connected to the 6.3V input. Would it be wise to add in a small value capacitor and a couple of 2W 300-600 ohm resistors between the filaments and ground?

Any help is much appreciated! Thanks!