Hi everyone,

I'm in need of a new preamp, and Pete Millett's Low-Mu Triode Preamp looks like it will fit the bill for my system:

Low-mu preamp

I'm looking for feedback on a few mods to the design, I know there's a few people here who have built or heard this design.

1. I want to use the Hammond 270FX power transformer, but its 6.3V winding can't supply enough current for all the tube heaters. Would it make sense to use a separate 6A 6.3V transformer to power the EL34 heaters, while using the main transformer 6.3V winding to power the 6AS7 heater? The EL34 heaters need to be floated above ground to avoid exceeding the heater-cathode voltage difference, so this way the 6AS7 heater wouldn't need to be elevated too. Might be possible to rectify and filter the 6.3V heater supply for the 6AS7 as well.

2. Instead of a 5U4GB rectifier, I'm thinking a 5AR4 might be a better choice. The 5U4GB heater current would max out the 5V winding on the 270FX at 3A, whereas the 5AR4 only draws 1.9A. It doesn't look like the power supply would exceed any limits of the 5AR4.

3. I think for the preamp tube itself, I'm stuck with the 6AS7 and 6H13C variants. The 7236 and 5998 tubes seem to be in short supply. Would either the 6080 or 6H13C supply more gain than the 6AS7?

Thanks in advance!

Hello,

I have a pair of 802D and 416A in good condition and I'm looking for the best cabinet/horn designs for mounting them.

Thanks in advance,
Bob

This amp came back after I rebuilt it and the sub channel failed.

Prior to the return, I rebuilt 3 of the 5 channels. Checked driver cards, rebuilt the sub driver card. Replaced all TIP102, TIP107, MPSA14, and 0.27ohm emitter resistors. Replaced ALL switches. Cleaned all controls. Redid heat compound and everything else. The amp passed all tests and I sent it off to a customer.

About two weeks go by and customer says amp is blowing fuses.

Returned to me, and I found the entire 5th channel blown. All TIP102/107 replaced again. Also put in a brand NEW FED1 driver card this time, and two new Rectifiers for the 5th channel. Amp is working again and I've tested it down to 1.5ohm in high power mode.


The customer was running it at 1.5 ohms under High Power mode, with two JL13tw3-3 subwoofers in a sealed box. Asking a lot from this amp with those dubs IMO; those subs are looking for about 1000w whereas this amp can only give about ~300w. Who knows what input level was used.


The sub channel to my surprise is running +-49vDC rail. Thats just shy of the 50v rail caps, and the TIP102/107 are only rated for 100v. Come to think of it, 49vDC is the highest rail voltage I've ever seen in a soundstream reference amp.


If I increase R102 or R104 in the PS circuit a few K ohms will that reduce rail a bit? SOA seems kind of tight with TIP102 at 49vDC otherwise. I had done something similar in a test amp prior - playing with rail voltage as an experiment. Not sure if this is the right thing to do. It would be nice to lower rail voltage to about 45vDC in high power mode.

What about using slightly higher rated, say 0.68ohm emitter resistors? Would that increase stability at all? I know the Class A amps run 1.0ohm + bypass diodes.

Thanks

I have a system in my kitchen comprised of 4 down firing 2x2 foot DML panels hung from the ceiling, a powered subwoofer, a DSP and the associated source/amp components

The DML panels start rolling off on the low end at about 300 Hz. Surprisingly with the sub's HPF maxxed out I get OK coverage from 300Hz down. However sometime when bass instruments (guitars, toms etc) are offset to one channel it can sound strange. So it would be good to have panels that could go lower.

The DML panels also need some extreme EQing to have decent frequency response.

What I'm thinking of doing is making 4 2x2 MDF panels with 1 GRS PT-2522 per panel to cover everything from 1K up, and some kind of high QTS big woofer to cover everything below that. Here is the problem though... I can't hang them very low. The baffle probably won't be more than 1 foot from the ceiling. What do you think? Could it work, possibly well enough to get rid of the sub? I know it's not ideal, but given the constraints of the room (there is literally nowhere else to put speakers) I don't have much room to work with.

Radu’s Shiny Eyes 300B Amplifier

I am selling this excellent sounding 300B amplifier. It delivers clean 6.5 W into 4 or 8 ohms for a 1.65Vrms input sensitivity. The frequency response is 20Hz-20Khz @-0.4dB at 4W and the damping factor is 8. This higher Df is due to a 300B cathode feedback.
The amplifier uses power transformer Antek and Hammond chokes. The output transformers are from an Elekit kit. The high voltage power supply is using a CLCLC filtering and the last capacitor is a Mundorf HV+ 4 pins. Low voltage filaments are all regulated and provide soft start for 300B tubes. The high voltage uses 6CJ3 TV dampers as rectifiers. They have very fast and clean rectification and very appropriate for this design. No equivalents though.
The amplifier is a 2 stage one, a design that I find very rewarding in a cleaner sound. The driver is a Russian tetrode 6E5P in triode mode, and it is capacitor coupled to the 300B. The 6E5P is a powerful driver and very appropriate to use with a 300B.
All my builds are sturdy and meant to last forever. The parts used are high quality.
There is a delay circuit to avoid pops in the speaker. The amp is operational after 1 min when turned on.
The chassis is built in my traditional way using a top plate special order from Front Panel Express (engraved Anodized aluminum) and a genuine mahogany wood case.
I added a volume control for whoever want to use it as an integrated. Volume control is a Blue Velvet 50k Alps stereo.
The amplifier comes with all tubes except 300Bs.
The amplifier is very heavy at about 35 lbs. and measures 19”x14” (WXD).

I am open for offers. Parts and materials cost me about $1600.

Does anyone have any experience with both 8 inch woofers, SB Acoustics SB23NRX ( either 4 or 8 ohms) and Peerless HDS Nomex 830869?
Kindly share your opinion.

I want to use either of these in a 2 way with crossover around 1500Hz. Both of these seem to have high distortion past 1Khz in test results available online.
While Klippel tests available shows 75% CMS limits at 4mm for SB23 and around 2mm the 830869. This makes me wonder if the Nomex is that much worse than the SB23 in bass?!

Thanks.

I was able to buy this already

Hey all, I have a Bel Canto Evo 200.2 (Tripath based) and the Samwha caps looks to have a bulge on the top - now I have seen this before on these Samwha caps, so I do not know if this is really a problem or not. Is this normal for these Samwha caps? These are roughly 20 years old and amp playing perfectly fine - no noises or any other issues...

Are Samwha Caps good caps?

I really do not want to replace them unless they are needing to be replaced...


My adage - if its not broken, don't break it...

Hi I may buy a B1 with the black controls and want to find out how easy or difficult it wd be to add a remote pot or even a Khozmo ( not sure it wd fit)
Many thanks

attached are cross overs of basic polk sda. sda 2a
and some information about the speakers. i know it's polk and all that. but i am mostly interested in cross talk cancellation in these cross overs.

the speakers consist of two 6.5" midbasses(8ohm each) and one 1" tweeter.
inner midbass and tweeter create a regular signal of a regular 2 way speaker. i could trace this in the cross over diagram
the outer midbass driver(dimentional driver) plays out of phase signal of the opposite speaker. speakers are connected with a 2 wire cable to exchange signals from left to right speakers.
from what i've seen online this cross talk cancelation is only utilized in 150hz-2000hz region.
so there is no cross talk cancelation above 2000hz or under 150hz

below 150hz that dimentional driver helps the stereo driver with bass output. so it does not do cross talk cancelation below 150hz

i am having difficult time finding out which part of the cross over diagram turns the dimentional driver into a bass driver under 150hz

i would like to change the cross overs into regular 2 way system with cross cancelation. it looks like original set up is some sort of 2.5 way system.
so id like the dimentional driver to always do cross cancelation. not only 150hz-2000hz. but in all frequencies under 2000hz

thanks in advance. and if any other parameters are needed can provide. didn't want to make this thread two burdensome with values and graphs.
have specs for drivers and tweeter.

Hello guys, today I unsoldered a microchip from an old board, named LM324N. It's not a programmable chip but a switch or something like this. From what I have read the IC I have can be used to amplify voltage. I tried to wire it just like its written in the schematics but from 5V I get 3.8V 0_o
Actually, right now I need a voltage amplifier to amplify 5V of the Arduino pin to exactly 15V (or at least 12V if 15 is not possible).
For those who are familiar, please explain to me how this would be possible? If resistors are needed, soon I will have resistors varying from 10 to 1M ohms so tell me the exact resistance needed.
Thanks!

ERROR:0C Does anyone know the meaning of this error code?

Hi,
I've got two synchronous SPDIF-like sources coming from the same equipment.
Each source goes into a separate WM8804.
The sources are synchronous. Does it make sense to run one WM8804 in Master mode, and one in Slave mode? The idea being that there's only one PLL, so my two recovered data outputs will be in sync (and will have common BCLK and LRCLK).
If so .. according to the datasheet, BCLK and LRCLK on the slave device become inputs. This seems to be borne out by my own experiments - those inputs float, waiting to be driven.
I'm using Hardware mode, to keep it simple.
I'm setting up:
SDIN/HWMODE = 0 (hardware mode)
SCLK = 0 (slave mode)
CSB/GPO1 = 0 (SPDIF output will be taken from SPDIF RX, although I'm not actually needing that)
GPO0/SWIFMODE = 0
SDOUT/GPO2 = 1 (pullup 10k) .. together these two select 24 bit I2S
RESETB = 1 (pullup 10k)

and bringing LRCLK and BCLK across from the master device.
I'm not seeing any output .. am I doing anything obviously wrong here?

I've found some posts on this topic but nothing really satisfactory. I'm brainstorming a semi-active 3 way speaker system where the woofer (working up to 300-400 hertz) would be active but the low level input signal for its dedicated amplifier would be taken from the speaker level that's driving the mid and tweeter (which are passive).

I know this has been done before and is being done for example in the new Paradigm Founder 120H speakers. Unless those speakers suck, which I don't think they do since they are the flagship of the line, it appears that this can be successfully pulled off.

I understand that the one seemingly obvious downside is that you are compounding the inherent distortion of two amplifiers but since there is no mid and treble frequencies involved and most amplifiers have low enough distortion in that range I'm assuming any deleterious effects would be inconsequential.

My question is to those that have experience in this or can shed some well informed light on the subject. How much would you lose in transparency and dynamics (if at all) in those first few octaves (up to 300-400hz) by converting the speaker level down to line level? Is there a better way to implement this asides from using just resistors? What drawbacks are there to doing this?

Edcor xpwr131-120 PT, 350-0-350(tested), 6.3v 4a, 5v 3a.​

https://edcorusa.com/products/xpwr131-660v-175ma-ct-6-3v-4a-ct-5v-3a-ct
New transformer, never used. The transformer is not very quiet, it can produce noticeable buzz.

$70 shipped

OTL CIRCUIT from pioneer old model










vdo OTL pioneer???2 - YouTube

Hello,

Does anyone know of a class D single-ended design that is made up of discrete components primarily? It would be preferred it if has a self-oscillating feedback loop used for the comparator.

T

I have a pair of speakers using the focal 8k 5412 subwoofer one is not working ( open circuit). Try as I may I am unable to find a replacement speaker, voice coil or substitute speaker ( would need two ).
Any thoughts here greatly appreciated.

Merry Christmas and Happy New Year!!

It’s hard to believe it is already that time of year again. The holidays are here and with that, an opportunity to reflect on the year we are leaving behind and to look forward to all the possibilities that a new year brings.

We recognize that 2021 came with its own set of challenges. I thank you for your support to make the reissue of TU-8600S sucessfully available to you in November.

Here are the highlights for 2022:
1. TU-8900 with Audio Note Tantalum Resistors and copper caps
2. KT170 SET amp from Sunvalley


Thank you for your support !!
Victor , Koda (my dog) and Tobby (my cat)

Thinking of building my own HiFi RCA stereo ground loop isolator with 1:1 ratio for transformers.

Trying to mimic Supra AGS-10k
Frequence intervall: 15 Hz - 22 kHz
In- and Out Impedance: 10 kOhm
Ratio: 1:1

Any suggesstions for this DIY project?

That Supra AGS-10k costs around 60 euro so if i can build a similiar cheaper im happy. If not im buying it.

Use for reciever sub preamp and subwoofer amp.
Having issues with noises from PC via HDMI and antenna cable tv to antenna socket/wall. Humming in subwoofer.

I have for sale a Rockford Fosgate Power 300 with 3 good channels. The 2 front channels work and the rear right channel works. The rear left was toast not working. I sent it to Evans at Desert Audio Specialist and they said it couldn’t be fixed.

Note: I am selling this amp as a 3 channel amp with 3 working channels.

See attached pictures.
$300 OBO

Friends,

Just got word that Ed Dell, the man who started Audio Amateur, Glass Audio, Speaker Builder and later AudioXpress died earlier this week. Ed just turned 90 two weeks ago.
Another loss for the diy community. Ed probably did more for the audio hobby then anybody else.
I had the privelige to meet him a few times, last a few years ago when I interviewed him.

jan

See also http://www.diyaudio.com/forums/everything-else/200752-ed-dell-audio-amateur.html

hello guys

What do you think about PT2325 for volume control?


I plan to use PT2328 with WIMAs MKS2 1uF 63V 5% for IRS2092 amplifier.




Do I need to have two decoupling capacitors? 1uF at output of PT2325 like datasheet and 10uF of input for IRS2092? Or is it possible to have only the bigger one? Would 15uF be better for IRS2092?




On schematic one resistor and capacitor have no value.


Will 100R be good and 100nF ?


Thanks


I modded a Sony BDV-E2100 with 3 PCM5102A as DAC and its works great.

I have also the 6 channel IRS2092 amplifier.


Thanks

I want to try the soldering paste method, and notice that the paste comes in different temperature ranges. I wonder what you all would use for transistors that are approx. 2.9 mm x 1.4 mm? And if you have any other tips or suggestions as to what equipment you use, that would be appreciated also.

Here's a pic of one on a penny:

Hello all,

I have an Amcron DC300A here with one IOC light that stays on all the time, but there is no audible difference between each channel.

Do the more experienced DC300A techs here have any idea what this could be? It is a recent change to an amp that was doing a great job prior to this warning!

Thanks in advance!

On the old forum, clicking on a link always opened in a new tab. This has now changed so that a link to another thread or post on diyaudio.com opens in the current tab, but a link to another site opens in a new tab.

I think it was much better when all links opened in a new tab, as it makes it much easier to go back and forth between different but related treads.

Yes, of course I know that one can right click on a link and select "Open in new tab" but I still think the old way was more user friendly.

Edit - if it's relevant, I use Edge browser.

**************
Other than that, now I have got used to it, I like the new format very much, congratulations to the team. Creating posts with attachments or images has become much more intuitive.

guys can you tell me bit more about these transistors? they came out of Marantz 1060, only markings on them is '702 FP' they were in place of 2SA493 so they are PNP and measured hfe is about 75...

Hi Everyone, after a protracted hiatus from the forum and analogue audio, I decided to re-enter the fold! I got to dust off my Audio Electronic Supply SE-1 amp with 300B tubes and my AES AE-3 preamp, that I put together about 20 years ago.

Now that I have some free time on my hands, I realized that there must be loads of modifications that can be done on both units to enhance the sound. Does anyone have a list of mods or suggestions on how to re-energize these 2 great units?

Thanks for your help and advice!

Roger

using the first commercial aperture - the slanted parallelogram (which was shortly followed by their "lemon" shaped opening.

RJ8




one might try the JBL shape lens R-J vented - or simply over the cone of their direct radiator speaker

Ok, I'm new here, so have mercy... I recently acquired an older Hafler DH500 that had been partially dismantled, in the process of attempted re-assembly, I downloaded the maual, schematics, etc from the web. However, the manual info only appears to pertain to the PC-19 boards, it seems thereare some differences between the pc10 and the pc19, connection-wise, and would appreciate anyone being able to provide the wiring info necessary to get this back together. Specifically, the wiring of the output fets to the pcb(6 wires), as the boards were pulled from the heatsink assembly.

Having watched some videos it has me wondering what exactly classifys a project as DIY. I have always thought that a DIY project meant that the project was entirely a project made by a person and didn't evolve a PC board that was made in China from a borrowed or stolen audio design made by some company usually here in the U.S. that was trying to scrape out a living producing a useful meaningful product. I guess DIY now means buying a Chinese PC board that is a copy of say an American design ordering parts stuffing the board putting it in a store bought chassis which usually doesn't compliment the device spending several hours in simple hole punching and wiring and then patting oneself on the back for a successful DIY project. How could I have been so mistaken? To actually think that one would spend time to either come up with a design or to modify a design that was out there and then either make a PC board of their own or wire something point -to-point in a hand made chassis or a chassis that they designed and then sent specs to a metal shop to be made if they didn't own tools and machinery necessary to fabricate the item themselves.

Like I said I'm probably wrong about my concept of what is DIY. Yet, when I look at some of the pictures of completed projects I can see readily that most of these DIY projects were well thought up. Power transformers and output transformers mounted to metal plates that were carefully laid out to exacting tolerances. Holes drilled around tube sockets to allow for air transfer and positive cooling effects. Wire supplying heater circuits twisted and carefully arranged so that hum will be minimized. Color coded wiring in some instances that allows for instant recognition of exactly when that wire is going. Resistors and capacitors with leads insulated and leads bent o so carefully.

Like I said I thought DIY was making something that for the most part you designed something that you have dreamed about something that when completed becomes a part of you and completes you. So, maybe I'm wrong or maybe I'm still 3 sheets in the wind from last night hell I don't know. Maybe this afternoon when I sober up I'll dig out a project that I scribbled down on paper several years ago along with a piece of copper plate and an old wooden base I made a while back and simply say what the hell I'll give it a try because its been a while since I made something from scratch something I'll call a DIY project.

Hello, I am building a SET utilizing a 3C24 tube and Monolith output transformers. There are different connections for 4/8/16Ω outputs. I'd like to be able to switch between the different taps. I'm planning on individual binding posts but want to switch the different connections shown below.


I want to use a single throw/triple pole switch so as to change the connections for the 16Ω wiring shown.
A to C will be on one pole (one side of the "throw")
B to D will be another pole ( same as above)
B to C will be on the third pole on the other "throw"

My question is will the Carling Miniature Switch be adequate for the task. The amp will put out about 5-6 watts and the switch is rated for 5A@125VAC or 28VDC.

Is there a better solution?

Hello, I bought a very nice looking tube tester: the RCA Wt-100A.
Is there anyone who owns a manual and wants to share it with me? I really would like to restore the tube tester, and use it as soon as possible.
Kind regards,
Roeland De Vriese

Good day guys, having issues with this amplifier (green board) have all the necessary voltages in fact I’m having my rail to rail oscillation (highside and lowside drive signal) but I know reasons im not getting any audio on my output pin from my preamp board..I have audio on U101 output, not much around U103 none on U104 (in fact I’ve replaced all 4 IC’s for good measure). Is there something I’m missing, all resistors checked off good.

Hi,

I have a PSU Hypex SMPS400A400 that is dead. I want to repair it but some of the components are exploded.
Could you please indicate the reference of the following components:

T14 (located near to the diodes bridge rectifier)
D43, T7 and R23 which are SMD components located just below the main capacitors.

Thank you in advance

Hi
Just ordered F6 pcbs
I have a 2 x 24 500VA toroidal
can the 24 volts be dropped to 18v or am I chasing my tail.
I have done a search on this and there are many different ideas if this can be done or not
I was hoping to use what I have on hand.

THX
Brian

hello!
I'm looking for a new amp to power my PA subwoofers. they are loaded with 8x PD.185C003, each with an A.E.S rating of 1500W. they can either be hooked up as 1 channel with 4Ohms or 2 channels with 8 Ohms each, or 4 channels with 4Ohms each. its intended for outdoor festivals, so the more power the better 🙂 any suggestions? im tempted to try a cheap chinese lab clone (sinbosen), but thats probably a bad idea....
cheers, lisette

As described here:https://www.diyaudio.com/community/...-platform-feedback-wanted.380360/post-6883244 One of the very few features I was using in the old platform. Right click on posts total would show up posts per member.

I derived the title of this thread [Analog Pulse Line Level] from this Forum's title of [Analog Line Level].

Its objective is to add a different food and fiber for thought and analysis. .

1. Analog Pulses are generated from the precise rectification of Analog Signals.

2. Analog Pulses are processed/amplified in DC circuits.

3. Analog Signals are lastly reconstiuted from their Analog Pulses.

This approach to processing works. Please use the thread [as reference] which is entitled "Class aP amplification" in the Pass Labs Forum.

Anton

The amplifier I built about two years ago has one channel causing crackling sounds when no signal is present. I also noticed crackles when there was a signal. My suspicion is there is a leaking component which is causing the generation of these unwanted sounds. I am posting to ask what tests I should do before I open the amplifier's box to look inside. The amplifier is a large amplifier using four pairs of {2SA1943, 2SC5200} with their emitters connected to the rails albeit through 0.22R wirewound resistors. The collectors are of transistors on each rail as connected together and feed energy to the speaker through a 0.1R resistance. The latter, is connected to ground to provide some negative feedback for the driver stage. When I was in the final stages of this amplifier build I had to add 3.3R resistors to the driver's emitters. The resistors are in series with the 0.1R resistance. Without the 3.3R resistance, both channels clamped onto one rail whenever I tried to adjust the amplifier's quiescent current. The latter was impossible without these resistors.

Please note, although the schematic has DC offset correction circuitry I omitted this in my build.

I have not seen any reviews of the SB Audience Bianco 25CD anywhere on the web. Other than it is a newer driver, any reason for this? I am new at looking for CD tweeters so I could easily miss something glaring. Some points on the driver:

SB Audience :: BIANCO-25CD-P

AES power Handing 20W with a 2.5khz crossover. This is lower power handling and a higher crossover point than most compression drivers. This is due to the 25mm voice coil.
However, the frequency response is quite flat down to 1000hz.

With a 109dB sensitivity, this looks like it could work well in a home setting with a much lower crossover than recommended.

SB does not publish distortion graphs. This makes knowing how this would perform at a lower crossover frequency unknowable.

I have thought of buying a pair to play with but I have nothing to compare them to.

Thoughts? Should I get my feet wet or save my money for something better?

I've noticed in troubleshooting my CS-800 power amp that I'm going through triacs. There are other intermittent issues that could also be the root (not so good connections from the 4 pin power amp board differential plug) and I've seen rail voltage at the speaker terminals at times and not at others... having trouble tracking it down.

But the question for this thread:

Can the DC offset that occurs without a speaker load to absorb it cause the triacs (and OT) to fail? By DC offset, I mean, turn on gives 20VDC for a second and turn off also produces this as the caps discharge. It takes a minute to completely drain without a load. If I have a speaker connected, it's just a thud and the speaker load soaks up the voltage instantaneously.

I'm just trying to figure out why the triacs are so short lived. I have been troubleshooting at times without a speaker connected and wonder if this DC is being picked up and the output crowbarred on startup.

Hi all,
Is it possible to bias a 555 in class A? And would it be safe? Even less than 30w pc would be enough...
Thanks

I noticed a slight buzz in a high end power amp that was isolated to the right side channel and doesn't increase when adding volume to source material. Roughly two months ago for the first time I heard this audible buzz. It went away after I powered down then back up, all seemed fine and quiet as usual. Until yesterday when I caught it for a second time several weeks later.

These amps have one of the quietest noise floors (madrigal design group Proceed amp2). This interference pest noise in the one side is not loud but it is apparent straight away with the volume lowered.

I'm a complete novice when it comes to repairing circuits, I can handle soldering but not much more than that. I'm able enough to slide the top off and inspect for a bulgy or leaky cap, things of that nature. Some guidance is appreciated.

Of the top do the symptoms sound like its something minor like that? I recall fifty send caps being the gremlins behind sporadic intermittent audible noise in amplifiers before. Since this is one of my very favorites I'll cross a couple fingers.

I'll track down the other schematics, I know they exist on the web in a pdf as I ran across those illusive pages before, saved in my previous laptop I no longer have.

https://manualmachine.com/proceed/pcd/2347143-schematic/

Hi Everyone,

For Aleph2 600VA transformer monoblock, which one is correct Secondary VA rating. I need to create +/-40 volt symmetric psu.

SECONDARY : 0---40 V./ 600 VA,
0---40 V./ 600 VA

or

SECONDARY : 0---40 V./ 300 VA,
0---40 V./ 300 VA

Is above correct way to write that I need symmetrical/In phase secondary to create +/-40V?

Hi, I'm Alan, from Scotland but live in California.

My beloved 66SE ki amp has stopped working, the indicator diodes go on but there's no audio output from either speaker outputs or headphone socket.

I'm handy with an iron but have never used a multimeter although I'd be prepared to have a go if I had a pointer.

Any chance anyone could point me in the right direction? Do I need schematics for example?
Cheers
Alan

Hello everyone, my name is Mattia, I bought this Scott MDX i62 stereo in 2005 / 2006 and it worked fine all these years till the last 3 months. Audio started to disappear when it was turned on, and then it would randomly come back after 5 or 10 minutes. Then it became 20 minutes, then 30 and now it's just permanently mute. It turns on fine but no audio.


Is there anything I should check that caused this problem? the audio board seems to be fine overall and I see no burnt capacitors at the outputs. The only thing I've tried so far is a reflow with hot air and flux. Thanks in advance, if Anybody can help 😊

Hello.
NAD C370 INTEGRATED Amplifier.
Protect mode.
If I deconnect CZ404 no protect mode.
Amplifier works fine,but only left channel.
I desoldered all power transistors all 6 transistors are ok.
I replaced bad caps on protect circuit,no results.
+64v & -64v are ok.
Q413 Q415 Q417 Q410.....OK
Q411 Q418 Q414 all ok.

No damaged parts.

SM

https://elektrotanya.com/nad_c370_sm.pdf/download.html

Just to create a change of subject,

Does anyone have details of Passlabs history, the early days etc.

I find it interesting to trace how people got into a specific field or career and how they progressed.

Perhaps Mr Pass can provide use with some insights!

regards

macka

Is either of the most commonly used enclosure types like Bass reflex, MLTL or various types Transmission Line more excursion efficient than others.
By excursion efficient, I mean more port output against actual woofer cone movement.
Or does any of these type of enclosure has loading over a wider range of frequency?

I am planning for tuning frequency of around 32-38Hz for a two way using 7 inch driver. So, any band pass or tapped horn type enclosure with limited bandwidth won't likely work. I want a design that gives me the most SPL for whatever limited excursion I have from a 7 inch woofer.

I haven't decided on the woofer yet.

Thanks.

Kicker said they don't hand out schematics anymore....
I need to repair this amp and I know that I need to replace all of the irf3205's but I'm not sure if anything else is damaged. anyone have a schematic or experience with this particular model??

I just grabbed Thorens TD166 in pretty bad shape, cheap. One motor winding blown, repaired now. Badly scratched faceplate, had to completely sand it down to bare aluminum. There was no headshell, and I was amazed that it goes for as much as 85eur on ebay! That was it, I had to buy a 3d printer and make one of my own.

I have a Marantz MM 500, 5 channel power amp that is causing me some troubles 😉

All channels work, but then from time to time the sound in the right channel simply disappears! .... the next day it is back again.
I have measured if there is some DC on the output, and there is not ... so the output is not burned ... also as the sound returns 😉

I'm thinking that it might be the relay, or some muting in the input .... not sure ...

Have been trying to locate a service manual on the internet, but only found the sites pushing (public knowledge) for money ... not supporting that.

Thanks in advance

Hi everyone!




This is my first post, but I read the Forum for years.


I have been given a Technics SU-V90D in an unfortunate state, completely disassembled and with a handful of components in a bag.


It has taken me a long time to start it up, it had a large number of broken active components, not only in the power stage, but also in the previous one, input selectors and even in the LED controllers.

After all these problems that have arisen in the repair, the ampli turns on perfectly, closes the protection relay and sounds really great with headphones, but with 8 ohm speakers a strong distortion appears.


There are no short circuits, no noises and nothing heats beyond normal.

In no case is there continuous current at the output.

The problem I think is coming because I can't adjust the bias of the AB class exit stage. According to the manual, there should be + 1v and -1v in the driver bases. I have 2,8v at the base of the positive driver and 1v at the base of the negative driver.


Now the weirdest thing is coming: this happens with the standard operational, the M5219P. If I put another, like the NE5532, then I have -2,8v at the base of the negative Driver, and -1v at the base of the positive. With another quality opamp, the JRC2043D the voltage goes to 3,2v and 1,4.
I just tried an NEC 4570 and the same, 2,8v and 1v, both positive. I clarify that I have the operational ones with sockets, I don't know if it influences anything.


The voltages in the opamp IC 501 are correct except those mentioned, and correct are in the pair of output transistors.


I have reviewed, checked or replaced all the components of the bias circuit of a channel, since this happens in both channels at the same time, which puzzles me even more, since apart from the opamp IC401 they are two separate stages, and all the chip voltages are correct.


I have verified that the bias adjustment accentuates the problem, so I have it to a minimum.


All the semiconductors I use are 100% original, bought by ebay in Japan, Germany and the USA.

I read that this Technics technology consists of a class A amplifier followed by a power stage in class AB. I explain myself fatal, but I have read some documents on the internet to understand the operation of the amplifier.

As far as I understand, the class A part is working perfectly, as I say, with headphones it sounds spectacular.


If you look at the scheme attached, the voltage amplifier goes to the output through a resistance of 1 Ohm.


I put the service manual in 3 RAR, is almost 10MB.


I have analog and digital scope, multimeter, audio generator and all habitual stuff.


Thank you for reading. Any input is welcome.
Regards!!!

I just bought a Staco type 1010 autotransformer at an estate sale. the previous owner had put it in his own case but the way he configured it is not what is shown in the manual.

the 6 page manual is: https://www.stacoenergy.com/images/...nd-test-sets/stacovt/user-manual/003-1003.pdf

he has wired 2/5 as input and 3/4 as output (diagram is on page 2 of the manual)

when I test the output the range is around 6 to 180 volts.

is there a safety reason that I should rewire it to 1/4 and 1/3 as in the manual ?

did he do this configuration intentionally to get significantly increased voltage ?

Hi All, this forum looks like just what I've been searching for!

I want to add a line level input to my 1st gen Amazon Echo, which uses a Texas Instruments TPA3110D2 Class D amp chip (useful teardown of the Echo is here: https://www.ifixit.com/Teardown/Amazon+Echo+Teardown/33953). I'm aware that they can be setup to run as Bluetooth speakers, but I'm specifically looking to add a hardware input here.

Does anyone have any thoughts on how this could be achieved, or examples of similar projects that have added aux inputs to a device with this kind of chip?

Thanks!

Whenever someone quotes another post I see it translated to my system's other language? The original post remains the same, only quotes are concerned

Hi,

I am currently working on this amp. The problem is that the amp is totally dead (no power). It has two power switches, one is a master switch and the other is a main zone switch. Both switches have no response at all. Does anyone has a schematic for this amp. Pls assist.

Carlos

Unfortunately one of my driver in Ergo IX is not working
If any one have a new or used one please let me know

Regards

Some requests have been made for how browsers should handle back button behaviour:

1. After visiting a thread via the front page pressing the back button should ideally change the visited link you are returning from into the visited link style
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A technical review of the possibility of fulfilling these requests will be performed.

Seasons greetings all.

My preamp, a Yamaha C4, works and sounds excellent.. apart from a hum!
Am having ridiculously immense difficulty locating the source of this.
Lots of reflowing of solder and switch cleaning haven’t yet resulted in discovering the cause. It can be heard on all inputs but is loudest when ‘Phono’ is selected.

Question:
Can anyone tell me if the following statement allows one to determine the area of the amp where the hum fault is most likely located?

With INPUT selecting Phono the following occurs:
When PHONO is set to Phono-3 MC the hum is equal on both channels.
When Phono 1, or Phono 2 is selected the hum is much stronger through the left speaker.

Also might anyone have a reasonable circuit board diagram of the C4, my own copy is virtually illegible.

Probably not new to many, but I was just ordering some stuff from DigiKey and saw their ads for DKred. One off boards for buck-50 an inch. That actually changes some ideas I have.

Are there similar other serivces?

Hi all,

Looking at first DIY built. I want to use the DIYSG Helix TM kit in the small Denovo floor stander cabinet. Essentially, my thoughts are to cut a hole in the front baffle of the Denovo kit, and seal the Helix baffle to it (so it will be elevated off the front of the cabinet 3/4". I would obviously have to flush trim the Helix baffle (9.25" wide) to line up with the sides of the Denovo cabinet (8" wide). I would do whatever the biggest round over I could get away with and still blend with a round over on the rest of the front edge of the cabinet. My question is, would the Helix crossover need any kind of adjustments in order to do this, to make up for the shorter baffle width?

I am trying to pick a wire gauge for wiring up a SUT. Is there a benefit to smaller gauge wire say 24 or 22 AWG vs the 20 gauge I have in stock?
Assume that I don't have a problem with purchasing a few feet of whatever gauge is appropriate.

Hello team,
Please consider customized sticky threads, linked to the actual user. The user would be able to add/remove sticky threads on their own. For example in the Valves/Tubes thread there are 8 stickies. Some of them really should stay there, but I never visit others, and I would add some of personal interest. The default should be the bare minimum like High Voltage Warning and perhaps Photo Gallery. These should be "hard sticky", others flexible.

Anyone know what is the value of the red capacitor? I cant see the label clearly. It is added between the secondary side of psu. Is it a ceramic capacitor?

There is some great shops out there guys, nice work. To the shall we say less than greatly priviliged with awesome workshops 😉. We have to work with what we got. I got access to set up my very own work shop and its been a while since having that in condo life. All of about 8x8 feet for my grand get away. I can share as soon as I'm finished setting it up with power and other small details. My table saw will have to stay outside for now. I have used it rain and shine, not a big deal.

I might be able to squeeze a tuner amp and some speakers. Always nice to have music to work with.

I thought it would be fun to share minimalist work shops out there if you want to join, welcome.

Looking to buy a quad of used 6550's for my Allen model 75 mono block power amplifiers. Had recently purchased a new quad of Tung Sol KT 88's for them and I absolutely don't like the sound. So, I thought I would try some used 6550 WE Sovtek tubes and give them a try. I had always liked the sound of this brand in different power amps. So, looking at two different used quads that were measured on a Maximatcher with the following measurements. One quad has specs of 31-35ma/ 4.02-4.28 mMhos and one quad has 43-46ma/4.57-4.97mMhos. Which quad would be better?

https://www.moon-audio.com/furutech-outlet-cover-102-d.html
The writeup is hilarious

I've been looking for a replacement for a couple days, and the closest I've come is the below options. Would these be suitable replacements, or is there a better option I haven't come across yet?
They are from an Alpine MRV-1507 on the audio board is where I have one shorted, and that part seem to be end of life.

These seem promising other than the gain bandwidth:
https://www.mouser.com/ProductDetail/?qs=5C9Q4QJFsuOFzbCX6nRlHg==
https://www.mouser.com/ProductDetail/?qs=Mv7BduZupUjGQix8c1RZeA==

For sale , 2 Altec Peerless 15095A and 1 Altec Peerless 15095 line transformer,
Price $80.00 each or all three for $180.00 Plus shipping
Sold