Hi all.


This may see like a newbie question, but the search feature returns nothing (for me anyway).


In a differential pair where the load is not a current mirror and when only one output is used, designers typically do not put a resistor at the unused side's collector (see attached image, left).


Is there anything to gain by having the same load for both transistors (see attached image, right)? After all, when a current mirror is used, both transistors are loaded equally.


Any insight would be appreciated! Cheers.


--Christian

Not sure where to post this so decided to post here too:


Wondering if anyone here could perform any upgrades to an HDP Express II DEQX?


Looking for any recommendations, I've heard of people replacing the clock with a better one and
using better caps on the output stage. Regards,


Eli

Hi All.

I have recently completed building a pair of horn loaded two way speakers with a split crossover. The crossover is split into HF and LF sections so that one amp is used for the lows and another is used for the highs. The crossover point for this amp is 630 HZ.

My 630 HZ crossover point means that the amp driving the HF section of my speakers doesn't need to be able to put out bass frequencies. Given this fact, what are the optimal characteristics of an OPT for this HF amp?

I build tube amps, so there is no issue with building an amp that has the limitation of working only above 400 HZ (400 HZ rather than 630 HZ because I may want to use it in another 2 way that has a 400 HZ crossover). I am hoping that being freed from the requirement of having to reproduce bass frequencies will create an amp that has better mids and highs than would be the case for a normal full range amp.

The other side of this question is what would be the optimal characteristics of an OPT made for bass frequencies only? Say 400 HZ and below.

My understanding is that the parameters that make OPTs great LF performers are in conflict with the parameters that make them great HF performers. My thought is that my set up allows me to split these opposing requirements into two separate amps.

I know that this is an odd question, but any advice or input would be much appreciated. Also appreciated would be any recommendations for specific OPTs that fit these criteria. Thanks!

Hi everyone !

I have a problem with my Sure-TA2024 amplifier. After i returned from vacation my left speaker had no sound 🙁
I disassembled the unit in hope of finding a simple loose wire, but nothing.. Tried a new sound source, new sound cable, switched speakers, connecting the speakers directly to the board, nothing works. Only the right channel.

Any ideas, before buying a new one ?
Here's a picture of the board:



Regards ! 😉

Thinking about making an amplifier and while I have a collection of heat sinks here the biggest are from 200W amps and I may need something much larger.

If I was to assemble a heatsink from bits and pieces I have around is there a design calculator that is usable for vertical tunnels as I have read that vertical tunnels are more efficient than horizontally finned ones.
Is this true?

I have the large heat sink in the pictures attached but running the calculator over at Rod Elliots sound pages I get a figure of approximately 0.14C per watt which might be marginal for the power I want and need.
I want 300 watts and stereo so I would need to dissipate 600 watts from the single heat sink.
I had an idea to fit this amplifier into an old computer case I have in the shed

Bought this amp untested and of course it arrived DOA. Power supply fets (IRFZ44) had failed and although I’m not reading any shorts on the output mosfets I can tell one has definitely been replaced so it has had a failure at some point. I am trying to determine if the power supply drive circuit is intact. If I apply just remote and ground the power supply gate drive signal looks close to what I would expect

iCloud

Based off of that I dropped in a new set of IRFZ44’s and it powered up without drawing excessive current and idled with no issues. Rail voltage looked good and there was no excessive DC on the outputs. However the gate drive signal looks a lot different now unless I drop the input voltage to about 12.2 volts and then it looks like what it did before the new fets were installed. Here is what it looks like with about 14.2 volts of input.

iCloud

It’s been a while since I worked on an amp. Maybe this isn’t a big deal. I only remember seeing this one other time but the PWM chip in that amp was an SG3525. Just wanted to run it by the pros before moving forward with trying to find new outputs for the channel that has been worked on previously. I’d like a matching set of outputs in it.

Hello Everyone, i am new to this forum as well as audio repair. This is my first time trying to troubleshoot and if possible than repair my AVR myself. My AVR power led start blinking when I switch it on. I have removed the SMPS and checked the voltages. I am getting only +/-22V which is supposed to be +/-45V. All other voltages are ok. +/-45V goes to AMP pcb. I have visually inspected the SMPS pcb but I could not find any problem. Can you guys please suggest what can be the problem in this case? If required i can share schematic of SMPS. Thanks.

The S5 DAC will be out in Feb 2021.

Audial | High end audio D/A converters and amplifiers

https://www.monoandstereo.com/2008/04/interview-with-pedja-rogic-of-audial.html

A shunt attenuator in theory will vary the input impedance based on the volume setting but is this something noticeable in "the real world"? I've read where it doesn't seem to be noticeable in practice and it's arguably the most transparent solution of the three attenuators (series, shunt, ladder). I'd be "driving" it from a modern DAC ...

Hi,

I just breadboarded the input 6J4 stage of a Pete Millett design, not for that project but just to copy his operating points as a start my Darling amp...

Here it is, only the 6J4 and its plate and cathode resistors pertain Pete has a lot of optional features for this board:

Push-pull driver board

He's running a 6J4 with B+ of 293V, plate resistor of 30K and a Rk of 1K. As you can see he measures 190V right at the plate. I did the same lash up with 293V B+ and came close at 185V at the plate (slight resistor differences). Pete measured 3.4ma, I'm pretty much the same measuring across the plate resistor I get about 3.7ma. The tube grid is grounded. OK all is good, we match.

Then I went to go read the data sheet for 6J4 and it says that the max plate voltage is 150V!

https://frank.pocnet.net/sheets/049/8/8532.pdf

Finally my question is... Is the data sheet max plate voltage a hard stop or does it pertain to something entirely different? I'm confused as to why Pete Millett (a tube god) has 190V on the plate when this tube says 150V max on all data sheets.

Its more likely I probably have a big knowledge gap learning 🙂

Just ordered some IRF3205 and received IRF3205Z for a Hifonics amp I am repairing. Are these ok to use? Are they better or worse then IRF3205.

Hey guys, I know there are a lot of threads on this amp, and I have read all of them I
Could. I am having problems getting +vcc to the tl494 to get a square wave. I'm guessing something in ic5002 has the +vcc blocked. All pwr supply and output mosfets are out of the amp. I replaced both voltage regs. I replaced ic5201(battery detect). any thoughts?

Hello y'all,
Im building a camper-van music studio.
All powered by 12v so we don't kill batteries using an inverter.
We already have some MunroSonic Egg 100's.
I like them because they will fit nicely into the weird arc of the van roof and wont have corners to bump heads on.
The Munro amp is 240v so I want to replace it with a 12v Class D.
Can anyone recommend anything?
Really don't wanna break the bank here - I know I wont get the exact same performance as the original amp but something flat-ish response-ish just to get them going as good as possible for £150 - £350
Happy to buy a board and make my own box etc....
thanks!

This is the full heatsink casting from the L-07M. The amp died a sudden death and was not repairable. Item is in Geelong Australia and available for pick-up or post. International and Australian postage at cost plus $10- for secure packing.
I thought that as the T-03 packages were available somebody might be interested in this as it takes 6 units. The amp it came from was as most of you know good for 150 watts and while I had it it never ran too hot until the night it died.
Feel free to make a reasonable offer but I think it's worth $100-

I've just upgraded my EL34 P-P amp's power supply and I am concerned about the heat being generated by the filter resistor.

Before the upgrade, this was a straight C filter - rectifier straight into a 470uF 450V cap.

What I did was put a 200uF 450V cap and 100ohm 25W resistor in front of the existing cap. So a CRC filter.

It works. My B+ is down where I want it and I am sure there is far less ripple. However, the 25W resistor is running at 100 Celsius + after only a few minutes (amp running upside down with the bottom open).

I used this site Ohms Law Calculator to calculate the power resistor dissipation. My voltage drop across the resistor is 32 volts (based on the fact that my B+ is dropping from 426V before this change, to 394V after). So I plugged in 32V and 100 ohms on that site and it tells me 10.24 watts.

Did I screw this up, or is it normal for the 25W ceramic resistor to run this hot? I can imagine it is going to get considerably hotter when the bottom plate is installed and the amp is running upright for a few hours.

Has anyone published a schematic for a Moving-magnet head amplifier that merely loads the cartridge correctly and boosts the level, but without applying any RIAA equalization?

I understand that this sort of thing is common for Moving-coil cartridges, where a step-up transformer is either too expensive or undesired for other reasons. Such a Moving-coil head amplifier is designed to be connected to the input of a MM stage with RIAA.

I listen to all music through an excellent DAC, but there is still some music in my collection that's only available on vinyl. I have written my own RIAA equalization plugin in the digital domain, and my DAC also implements optional RIAA equalization in its DSP, and I hope this explains why I want to avoid the analog RIAA circuitry.

I've gone through an evolution of several stages so far:

1) Since I needed an adapter cable from RCA to 1/4" TRS or XLR inputs on my computer audio interface, I started by building in the 47 kΩ load in the adaptor cable. I started with the specifications for the input impedance of my audio interface, and calculated the resistor value that I needed to add in parallel to end up with 47 kΩ. This setup worked well, but the ground lug for my tonearm kept coming loose, as evidenced by obvious hum until I wedged it in somewhere.

2) After the ground lug came detached too many times for my patience, I decided to buy a cheap phono preamp with an actual screw terminal on the case. I then gutted the original RIAA circuit, measured the mounting points for its PCB, and fabricated my own passive adaptor. This time, I also added a capacitor to provide the 200 pF to 600 pF load specified by my cartridge manufacturer. The PCB is available at OSHPark. This worked well, but when I moved the cable to a different audio interface and again when I upgraded the electronics in the audio interface, the passive components are no longer loading the cartridge correctly.

3) My goal now is to build an active phono preamp, but without any of the RIAA curve. This circuit would be tailored for my specific cartridge, and the output would be at standard -10 dBV unbalanced and +4 dBU balanced levels so that any input on my various audio interfaces would work (without being fragile due to parallel resistor and capacitor combinations). I'm trying to fit everything in the same phono preamp case that I have, since the grounding screw is going to be a necessary component.

4) In the future, I hope to upgrade from MM to MC, and might just build Douglas Self's Moving-Coil Head Amplifier. I assume this could be connected directly to my audio interface instead of a MM preamp, and I could then continue to realize RIAA EQ in DSP.

By the way, I recently obtained Self's "Small Signal Audio Design" book, and this probably has everything I need. However, there are a few questions I have about my slightly atypical application that aren't directly anticipated in his text.

Despite the fact that I've not seen anyone talk about this, it seems like modern listening with DSP available might benefit from such a flat-frequency-response phono preamp. On a related note, I'd much rather archive my rare vinyl via such a flat preamp setup and then apply the RIAA curve during playback, rather than having to invest thousands into an analog RIAA EQ that doesn't suffer from the usual noise and component tolerances.

Brian

p.s. I'm planning to design around a +34V single-ended supply, since I'm a bit too cramped for space to pull off a +/-17V bipolar supply. To keep things simple, I'm using an AC wall-wart, but those have only two conductors - no center tap. Obviously, this power supply requires a virtual ground and capacitive coupling. Douglas Self recommends always using capacitive coupling on the cartridge connection to protect the cartridge from DC current. That seems like sound advice. I'm not too worried about the AC coupling on the output that my unipolar supply requires, since I'll probably use a subsonic filter that would defeat any potential advantage of DC coupling on the output anyway.

I am looking at converting the straight secondary flare of my MEH to a curved profile. (To lose sharp edges / improve mouth termination)

Is it 'good enough' just to round it over, or should it follow some sort of defined curve shape ? (tractrix etc ? )

Attached a side on view of straight vs single radius curve.

Thanks,
Rob.

Hello, inside of my Allnic phonostage is this terminal block, it connect various components in a chain like fashion. I wondering the technical name of the part, thanks!

[/IMG]

This fantastic-sounding 2-channel DAC is built upon the Twisted Pear Audio board, with the lauded ESS Sabre 9018 chip. In addition to converting CDs at the standard 44.1khz 16 bit, it will convert 24 bit 96 kHz hi-rez files, although I've never done it.
The components in this DAC are first class. The output section uses the high quality Jena Labs wire. Unbalanced RCA output jacks are Eichmann copper. Balanced XLR outputs are Neutrik. This DAC was produced by a well-regarded boutique Canadian builder Fallen Angel.

There is a single digital BNC input, with a COAX adapter; that's how I ran it.

The sound quality is stunning, rivaling the best DACs at any price.

The dimensions are 32 cm x 32 cm x 9 cm. Unit weighs over 8 lbs. There are some minor imperfections on the sides of the fascia, and a bump on the top left corner of face plate, not very noticeable, but I wanted to mention everything for the buyer. You will NOT be disappointed in the sound!

$395 includes postage in the USA.

Hi, first time poster 🙂

I recently have built a power amp based on Hypex NC122MP board. I bought a Ghent Audio connection kit, and it went quite smoothly. The only issue I have is a humming noise in both speakers, not very strong, barely perceptible from the listening position, which seems to be specifically related to the input connection.

For reference, in the NC122MP, the inputs are mapped to the following pins of the J4 H-Box connector:
- for channel 1:
--- pin J4.1 - inverting signal ("-")
--- pin J4.2 - non-inverting signal ("+")
--- pin J4.3 - ground
- for channel 2:
--- pin J4.16 - inverting signal ("-")
--- pin J4.15 - non-inverting signal ("+")
--- pin J4.14 - ground
I use the Ghent Audio h-box connector to attach shielded 3-wire input cables, connected to the RCA sockets. "+" goes to RCA pin. "-" and "ground are soldered together, attached to RCA sleeve, and are grounded tot he chassis.

Here is what happens:

Case 1: Amplifier powered on, connected to 2 speakers, all wires disconnected from the J4 H-box -- dead silent
Case 2: Amplifier powered on, connected to 2 speakers, input wires, connected to the RCA input sockets, with sleeve grounded, are connected to J4 H-box, nothing plugged into RCA input sockets -- humming noise
Case 3: Amplifier powered on, connected to 2 speakers, input wires, connected to the RCA input sockets, with sleeve grounded, are connected to J4 H-box, a source (network streamer with volume control) is plugged into RCA input sockets -- very slight humming noise, I really need to put my ear to the speaker
Case 4: Amplifier powered on, connected to 2 speakers, all wires disconnected from the J4 H-box; 1 single wire, 2-3 cm long, attached with a JST connector to J4.2 (channel 1, non-inverting signal, or "+") - same humming noise in channel 1 speaker as in case 2.

Basically, looks like
- powered on, connected to speakers, but with nothing attached to input pins, the amp is dead silent (except the usual slight pop when powering the amp on or off).
- attaching anything at all to "+" signal inputs provokes humming in the corresponding speaker.
- attaching an actual source on the other end of the connection cable does not stop, but attenuates the humming.

Any advice on possible causes, or troubleshooting hints would be much appreciated. Thanks.

Hello

I have some reel to reel tapes from when my siblings and I exchanged conversations with our dad who was on a course in Philadelphia. These are from the mid 60s.

One of them plays fine on the machine that I have, but 3 of them sound like chipmunks talking.

Would this problem be solved with a reel to reel machine that could vary the playback speed?

If so, where could I find someone who had one?

I found this forum and was hoping that this would be a good place to start my search.

Thanks, in advance, for you help with this.

Grant

8 ohm, 50 watt should do me. I'm assuming non-inductive. Suggestions please.

Steve

My dearly beloved CD-94 has a spindle problem. Laser moves up and down after closing the tray, but the disk is not spinning. When I put the machine on its side, press on/off button, it makes 1 rotation, and then stops.
Should I now replace the complete drive?

Your advice is very much appreciated

Eira

Hello everyone,

I'm looking for wire-to-wire and wire-to-chassis connectors for max 50V/5A DC. Use cases are 5V and 12V DC, 2-3A. Goals are

• connect a DC12V power module to a wire coming out of a device.
• connect a DC12V power module to a socket on back of a chassis.

Obviously the power module output should be female to be safe from accidental short-circuit when hanging around, and so the male parts should be on the device side.

I don't want any of those coaxial cheap models like on wall-PSU, they are unstable, cheap, and voltage drop is just too high. 4mm banana not wanted, that should look professional, not "lab on an excursion".

Best would be with some lock-in mechanism, preferably by rotation or screw, not by plastic clips that break after 5 manipulations. Should be either solderable and by screws, and preferably some multi-vendor standard that I would find at Distrelec, Mouser or the other suspects.

Hints welcome 🙂
Charles

I’m patiently awaiting for the MD-1 to arrive so I can try it out with the hopes that it will be a good candidate for mobile audio.

Are there any users of this bargain priced Bluetooth/Flash memory/DAC?

ZS-MD1 HiFi DSD Digital Player CSR8675 Bluetooth 5.0 DAC 384K 32Bit DSD256 tps | eBay

Hi, I recently bought a Teradak 2.7D NOS and it has clicks and pops problems on both channels. I removed all TDA1543 and tested them individually one by one but the click is always there. The problem happens with all the interfaces, USB, Toslink and SPDIF. I suspect that it can depend from Jitter also if I cannot explain how I can have it when I'm connected to USB as Tenor7022 and WM8055 are using same 12Mhz 1ppm oscillator.
Someone else had the same experience and could help me to solve this noisy issue ?

crossover dunce
If I were to use two identical FR units (per side) and put an inductor on one, that one would be 90 degrees out of phase from the other..is this right?

EICO ST70; 2 output transformers and 1 power transformer set.

Specs:
OPT: Primary Impedance: 6.6K ohm (no UL tap, used 7591 in Pentode)
Secondary taps: 4, 8, 16 ohm
Each good for 40 watts

PT: Primary: 115VAC
Secondaries: A bunch, never considered. Thrown in as an extra.

All measured OK for resistance/continuity all primaries and secondaries. No open or shorted circuits.

All end bells pulled and glass beaded -ready for paint. Original hardware included in a bag.

Originally acquired for the OPTs for a P-P 300B project for an Oregon Triode Society build.

In John Atwood’s testing and measurement of vintage output transformers, these EICO ST70 OPTs were only bettered in BW and quality by Harmon Kardon Citation II transformers.

$130 shipped -CONUS only (they are heavy)

I have a Threshold 400a with a malfunctioning meter board which I thought I'd rebuild since it's out. There are 2 transistor marked TN2002 which I can not find. I've gone to Alltransistor.com trying to find a replacement but no luck.

Would anyone know a substitute transistor?

Thanks,

Eric M.


**** OK, tried attacking from other direction. Schematic labels transistor as A42 (a Threshold house #) but you people here already assigned a part number of MPSA42 in the post

A42 in Threshold amp

If I missed anything, please post up.
Thanks

Since building a common cathode 12B4 preamp it has been plagued with 60Hz hum. The hum is constant through the speakers regardless of volume. The hum is faint, only noticeable when no music is playing, very annoying though!

I can hear the toroid transformer hum if I put my head very close to the transformers themselves. I don't think it is DC on the mains as I understand that DC on the mains doesn't affect small toroid transformers like mine very much.

Amp is star grounded with the common star point leading back to a bridge recto || resistor || cap isolator which then goes to chassis ground.


What I've tried:
- different 12B4 tubes
- shielded wire for all signal wires
- adding foam insulation under the toroid transformers themselves


Schematic:
Forgot to draw another stage of RC filtering, 270R with a 30uF to ground. Input selector for three inputs. Mute circuit to short the output to ground for 30 seconds upon start up. IEC filter for the 120V mains.
The PSU is the PS-1
PS-1 Solid-State Regulator Kit

Hello all, i need some help from expert people about croossover design.
I have some normal hifi speakers model jbl l830. They are monitors/bookshelf.
Since i m in lockdown at home because i m positive to covid and i have some sb acoustics drivers around for serveral months (plan to build a good speaker) i start to look at jbl croossover and to my understanding i tried to swap the original jbl tweeter for my sb acoustics satori tw29rn-b-4. I got a mdf base for the sbacoustics tweeter and put it on top.It sounds ok and i like the sound but i see jbl tweeter are only 3.3 ohm.
I attached the jbl schematic. I appreciate if someone with experience could look at it and see if the satori is working ok with that type of croossover or if is needed to change some values. I have some resistors laying around and also some caps and coils. I m using the orginal croossover but with better parts, better caps and a better coil in woofer.
Thks[emoji846]


View attachment 918329
View attachment 918330View attachment 918331

King of Reggae

I built a pair of Econowaves four years ago with Dayton Audio D250P-8 1" Polyimide CDs bolted to Dayton Audio H6512 6-1/2" x 12" waveguides, using the Large Advent woofers in LA cabinets. I use the Zilch-designed XO. I like 'em! These days most of my listening is with a pair of Omega alnico speakers, but I've always wanted to "scale up" the Econowaves. I like horns for their dynamic impact, two-ways for their simple crossovers, and high sensitivity (95dB+) because I like SET amps.

How about the FaitalPRO LTH142 1.4" 60 x 50 Elliptical Tractrix Horn with . . . ? Lots of blanks to be filled in!

More voltage on screen than plate?

Just finished a new build based on this design. I used some unused 3.5k ohm transformers I had from a previous kit build which indicated a 46% UL tap. When testing voltages I'm seeing 331 B+, 320 at the plates but 326 at the screen. I'm assuming that I probably need a larger value resistor than the 100 ohm I've got in there based on the triode set-up of the design. Any recommendation on voltage I should be seeing at the screen and/or a resistor size I should be shooting for? I'd rather start off with some intelligently sourced ideas than keep swapping resistors in a cramped chassis. Thanks all!

Hi everyone! I'm an EE, but pretty newbie to DIY vacuum amplifiers. After weeks of researches on books, forums, and youtube videos, I've some idea of how hi-fi schematics work. I'm now trying to finalize a schematic decision in order to order parts that I need. However, I've got few questions.

First of all, I can hear you all asking "What do you want?". Here's what I want:

• 6V6 SE
• 8-10 Watts Output
• Ultra-Linear (Maybe switched triode)
• 12AX7 preamp
• Diode rectification
• Mid-level volume operation
• Input will be line level (from pc or turntable with line level amp)
• Pure-natural sound

Now, here are my questions.

Power Supply
I'm planning to use a transformer with no tap (because it's cheaper) and diode bridge. I know I can use higher capacitance values w.r.t. tube rectifier and this will improve my ripple rejection. However, is it ok if I use no choke in that case (they are expensive)?

Preamp Tube Selection
In preamp stage, I've read that 12AU7 is not as linear as 12AX7. That's why I'm preferring 12AX7 even though it has unnecessary amount of gain for me. Would you suggest using 12AT7 or should I go with 12AX7?

Preamp Design
I've seen something as 4S universal preamp for 12A*7. Many schematics around the web uses a variation of this preamp. However, I've read somewhere that it is a "fiasco" and there shall not be something called universal preamp. I've seen many references on how to design output stage, but I don't really know how to design preamp stage. What do you think about this 4S Universal Preamp? What should I consider for an 12AX7 preamp?
Here is the schematic I'm talking about.


Negative Feedback
I've seen some very good sounding design that has no NFB. Would you suggest NFB or not? Why?

Some Designs I've Found

This one also uses the "4S Universal Preamp"

This one is from kleydejong of tdpri.com. I'm planning to build something like this, maybe without NFB. What do you think about this?

Thank you! 🙂

I'm trying to learn anode and cathode load line plotting Google style and have one small question... Some of the tutorials tell you to sum the value of the cathode and plate resistors in computing the current, and other tutorials neglect to even mention this and just tell you to use the value of the plate resistor. It doesn't seem to matter much with maybe a 12AX7 where the cathode resistor might be 1K and plate 100K, thats only a 1% difference.

Is it best practice to routinely just sum Rk and Rp so the total current across the tube is accounted for?

No sound until I back the power supply down to about 11.5V. Then it's faint but changes with the gain. I purchased Perry's manual and have been reading and re-reading the power supply and x94 operations. Some things point towards the transformer. I was also considering the voltage regulators. Nothing looks burnt and no shorts on the outputs but no voltage, either. 26V AC between center legs of Q9 an Q13(right of power terminal). 12.4V DC on the RCA shields. I have some higher than I would expect voltage on TL494 Pin 8, 11, & 12: 24.8V DC. Here are the other DC measurements:

Pin 1: 2.15
Pin 2: 2.45
Pin 3: .0076
Pin 4: .0013
Pin 5: 1.5
Pin 6: 3.4
Pin 7: 0
Pin 8: 24.8
Pin 9: 10
Pin 10: 10
Pin 11: 24.8
Pin 12: 24.8
Pin 13: 5
Pin 14: 5
Pin 15: 5
Pin 16: 0

( SOLVED) I was thinking about going active speakers so I thought of making some small multichannel power amps using the LM3886. Used the schematics for here:
https://www.circuitbasics.com/wp-co...-an-LM3886-Circuit-Schematic-with-Diode-2.png

Just changed a few things to use components I have around. Like 10µ in the input and filtering as I have enough of those. I use a UPC1237 for protection so I only put a 30k resistor at pin 8 (mute). PSU is +/- 23V. And I added a 270p between the positive and negative input.

But when I power these up I have a DC offset of 8-9 VOLTS!

First I tought of a bad connection or wrong components. But I now made a second one (without the UPC1237) and I have identically the same thing. Any ideas where to check because this is getting seriously on my nerves.

Hello everyone!

I am totally new on this area and I wishing to learn from this community that have a big amount of knowledge.

See you soon in the forum!

I'm building a Millenium 5-20 Valve amplifier but only have a 115V output transformer.

The transformer is rated at 220VA so should be good for 115V at about 2A.

My amplifier requires 450VDC at 250mA.

I'm using 1N4007 and 220uF caps in the multiplier.

Why is the voltage regulation so poor ?

Testing the multiplier with a 70W load I get the desired 415VDC but it is still over 500VDC off load.

I'm looking for a budget sensitive way of making a USB to I2S device, but where it's the i2s slave. I'd normally go for a SiLabs CP2615 for USB to I2S, but it is only capable of master.

I only need 2 channels in and out, at 24/48 only.

I've looked at the Teensy Audio project, but it seems to be limited to 16 bit (at the moment). I've also looked into the XMOS XUF208, which is capable but a somewhat complicated toolchain and a little overkill for a simple task.

Would appreciate any thoughts or pointers 🙂

---SOLD---

I was curious about Bob Cordell's Super GainClone and Klever Klipper so when I came across a set of boards that allowed me to easily test both, I jumped at the opportunity. You can see my measurements here: Review: Cordell Super GainClone & Super GainClone with Klever Klipper – Neurochrome

The Super GainClone performs pretty well, actually. It offers slightly lower THD+N than the 'naked' LM3886 at higher power levels. I wasn't as impressed by the Klever Klipper, but each to their own. This board allows you to disable the Klever Klipper by removing a jumper.

You can find the BOM for the circuit in Post #1 of this thread: Bob Cordell's Super Gain Clone PCB (LM3886) and a stripped-down version: Compact3886

Anyway. I have two boards as shown in attached image. One is fully assembled. The other one is ready for you to assemble. What you see is what you get.

I have gotten my technical curiosity satisfied so I have no further use for these. I'm selling them for the cost of parts, so $59 USD + shipping.

I ship world-wide and can take payment by credit card or PayPal. If you're in Canada, I can take payment by eTransfer as well.

Shipping by Canada Post to the US is $10 for standard airmail. $15 if you'd like tracking as well. Canada Post delivers in about 3-6 weeks these days. Shipping to Europe and Canada is ~$5 more.
I get excellent rates with FedEx and UPS and can get the box to your door in a few days for about $20-25 (US, Canada) and more like $30 for the EU.

Above shipping rates are estimates. Please contact me by PM or email (add @neurochrome.com to my user ID) if you're interested in these. Include your shipping address and phone number (needed for customs) and I will get an accurate shipping quote to you.

Cheers!

Tom

I've been drawing up the FH1 bin from cobbled together plans off the web. The dimensions I'm using suggest the horn gets 'pinched' in the 90 degree bend.

Is it like this in the original or are the measurements I'm using wrong ?

Thanks,
Rob.

Hey peoples,

Anyone know much about this pre amp? I aquired it not long ago and cant find any info at all on the web about it.

Its a fantastic preamp mind, dont use the phono stage as i have a heavy modified CA 640p which i use instead (from details posted on here).

Tx muchly!

Hi everyone!

I recently got an old 1970s regulated power supply unit off of ebay. I´ve tried looking for info on the manufaturer and had no success...


I want to ask you if anyone knows what is meant with the resistor connection thats printed on the positive outputs labeled V and I. This might be a newbie question, but i haven't had experience with this kind of PSU.

Thank you for your help!

Hi
My original Alpha 230 is getting a bit cranky so it is probably time to do a recap before something craps out.
Does anyone have a good parts list or parts source recommendation for this unit?
I have a copy of the digital copy of the Service Manual, but the parts list is a bit of an eye test for me.
Looking for any sage advice to get going.

Thanks!

My Beta unit is probably also going on the bench once I get the Alpha back

It is affordable, is extremely simple to build, small, and according to HR simulations the output looks very respectable. Group delay and excursion also look reasonable with the $50 SWE-10S4 drivers that i used in the sims.. .

Tinkering around with Hornresponse a while back i came up with this design... I never built one (and i probably never will because i have already moved on to other ideas that i want to pursue) but i thought i would post this on DIYaudio to see if anyone finds it interesting or useful .. I was also curious to see what the big-brained subwoofer gurus had to say, be it good or bad ..

I refer to it as a constricted transflex, but its like a tapped horn that is squeezed down in the middle, and it is also like a pipe-resonance mode based (instead of helmholtz mode) series tuned 6th order bandpass box ..
The drivers need to have an FS close to FB, along with tight suspensions and strong motors to work properly in this box...

I found two different ways of simulating it in HR, one utilizes the compression chamber function, and the other doesn't , but as far as i can tell both sim methods are valid and produce a very similar response and output ... I will post both sets of HR inputs.

As you can see one of the drivers can be physically mounted in reverse and the phase flipped to make this a push-pull (actually push-push right?) to cancel some distortion.. I know the "PP" feature has been something that some folks on this site have been using lately in other designs, so call me trendy 😛 ...

According to sims two of these cabinets (combined total of 200 liters) can handle 1000 watts without pushing the 10S4 drivers past their excursion ratings of 10mm one way, and output should be just under 130db with solid response all the way down to 40hz in halfspace .. Seems great for 2 small boxes that could be built in less than a day, using only 200 dollars worth of drivers total !

In a car or a truck (1/8th space or .5pi) the output is pretty obscene with one cabinet making 135db with only 500 watts input power , but of course only down to 40hz which is fine for much music but not all (depends on your personal preferences right?)

I didn't show any cabinet bracing in the sketch but its easy enough to improvise those ...

The response graphs remind me of some of the old MTL-1X Manifold-horn cabinets that EV used to make for dual 18" woofers, which is not suprising because those were also series tuned 6th order bandpass boxes, only much larger ...

I am looking forward to hearing your thoughts and reading you comments regarding this design. 🙂

Hi guys,

I think this is kind of a newbie question. but... What output transformer spice model do you usually use in your simulations?

I'm using the XFRM_NONLINEAR from the breakout lib, but I this model doesn't include the dc impedance and I think doesn't properly model the reactance either.

thanks for the attention
-Miguel

What are your subjective experience with decoupling the rectifier diodes? I dont mean a snubber across the secondary but rather a cap across each diode. With 1nf mkt caps across the silicon diodes im using to feed my 1875 amp, i notice a significant difference in the sound. With the decoupling in place the sound is heavier, darker (less treble energy) and the sound stage more closed in. Without the decoupling i get most of the lost ambience back but knowing that much of its sound character could be due to the unfiltered harmonics of the diodes i cannot decide which configuration is a superior

Hi

Regarding Technics SU-3500 I was thinking to use some higher ripple low impedance Panasonic FMs instead of Nichicon KZ which have poor ripple for the voltage regulator .

Is about four 220uf caps connected to the voltage regulators .

Those voltage regulators are 2SD390A I posted a photo . Those 220UF caps are connected to TR501 506

Panasonic FM have very low ESR and the ripple is almost triple compared to Nichicon KZs. There is any chance that this ultra low ESR and huge ripple might cause the regulators to malfunction or ultra heat ?.

I am trying to bypass the ballast in this projector I got for free so I can LED mod it. I have found the wires going from the ballast to the main board. I found the pin for the transmit optocoupler, and I shorted it to ground. Before I did this, the fan would ramp up and down 3 times over the span of a minute and then flash the power led. After I did this mod, it now goes green for a few seconds then cuts to the flashing red. If I shine a light, I can see the eiki boot logo until it realizes that there is no lamp. I found the thermistor and I heated it and saw the resistance dropped to 0 ohms, so I tried shorting the pins for it but it had no effect.

Using SPL & Impedance graphs to generate ZMA & FRD files for crossover modeling

Is there a way to use the data in freq. response and impedance graphs to generate FRD and ZMA files?

I've heard the term 'graph grabbers' but I don't know where to find them, or how to use them. I assume this is a software to interoperate graphs somehow? Any pointers greatly appreciated! 🙂🙂🙂



Hi, I'm new here so correct me if I'm wrong but...
As I understand it:
FRD files = Frequency Response data
ZMA files = Impedance data
Correct?


I need both ZMA and FRD files to use crossover modeling software however...



Manufacturers often share Frequency Response data and Impedance data as PDFs or PNGs but (with the exception of Dayton Audio) rarely FRD and ZMA files.





Dayton are great but I don't want to be reliant Dayton components solely for the reason they're the only drivers I can model with.


Thanks in advance <3

I have a QUAD CD 66 with a very dim display.

The 2 bulbs seem to be fairly bright.

The display is all correct but is hardly readable.

The circuit uses an obsolete LC7582


Anyone have any idea where I should look?


Andy

Hello all,
Grandkids are getting old, so I'll finally have some time to get back to the bench.
Will be building one of two topologies, both loosely based on Decware's SE84 series.
One is 6922-IT-EL84 ( TS ).
the other is EF86(TS), RC coupled to EL84 ( TS ).
the power supply will be identical for either.
Config will be C-L-C-L-C ( for power tubes ), tube rectified. Would like to keep the first rectifier under 8 uf for various reasons. Which brings me to my question.
All parts used ( have everything in hand ) will be top notch. Years ago when I modded the crap out of my SE84CS I swapped all the lytics out for ASC motor runs and loved what they did. the last two caps will be ASC, which brings me to the first cap after the rectifier.

I've got a bunch of ASC 15uf X386 caps, so a pr in series will get me at 7.5 uf for the first cap. My question to you guys.

Should I keep that cap as an ASC motor run cap, or would a higher quality ( say Mundorf ) foil cap be better sonically in that position ? I'm trying to squeeze as much out of the circuit as I can, and don't want to limit it because of one cap.

So, keep the ASC in that first position or look for a true film/foil?
Aas always, thanks in advance for your advice,

Cheers, and be safe,

Crazy Bill

A while back I built this tiny amp and really liked the 1 w or so output. Has anyone here built it and know the output impatience. I know I could measure it but the oscilloscope isn't working right now and it's cold in my unheated work space anyhow.

Hello All,
Awhile back I bought a pair of these for a 211 project. I was somewhat skeptical because of the price ($74USD each), but I took a chance and bought them based on a few positive comments I found when researching interstage transformers.

As usual, there are a lot of opinions floating around but not much data (or measurements) to show you how the device performs.

I built a test circuit (gain of 100) to give me approximately 300VP-P to see how the 126B would perform. Test circuit consists of SRPP 6SN7GT / 6BX7GT with 6BX7GT sections paralleled, running 30mA's thru the 126B.
6BX7GT Operating Parameters:
B+: 275VDC
Voltage across tube: 247.5VDC
5VDC loss across 126B
22.5VDC bias
750 Ohm cathode resistor, bypassed with 100uF cap

I terminated the secondary with 100pF and 560kOhm for testing. I also removed the 560kOhm resistor and the frequency response was still flat with no peaks or ringing.

Attached are a few measurements.

I've always wanted to make my own amplifier but I've also been hesitant to do so.
I've not even started the little chip amp project I bought the makings for.
but I find I need a new amplifier for subwoofer duties as the one I have been using just died.

I've gone back to the ESP website and reread the project I was thinking about. Rod Elliots MOSFET high power amp the Project 101.

I have a couple of big toroids here as a starting point.
2 * 500 VA
Hoping to find a mentor locally but that has been hard lately with lockdown etc.

Rod E's page does say they if making the high power version you need really big heat sinks and active cooling. Is it possible tho to have heat sinks that are too large?
I have come into the possession of a large heat sink.
It's 3700grams, multi finned, 270mm tall, 180mm wide and 75mm deep

I think it came from a rooftop solar array originally, the donor never said but he's a solar installer
Adequate?
Too big?

I have some G4S10 thyratrons. Have been playing with ideas such as guitar effects and synth use, but why not rectification. The thyratron rectifiers I've seen are using the grids to control the output, kinda half wave PWM of sorts. But I just want to use them as rectifiers, no fancy control.
I see on one thread here that the grids should go to the power transformer, leave plates floating, and that's it. But surely that can't be right? The grids are only to turn the device on. As a rectifier it should be on the whole time.
So is it not right to connect the grid to the cathode?
Also, I see claims of 'choke input only' but thyratron's magnificance is their incredible pulse current durability, is it not? So I'd think a cap input supply is no prob...?
Any tips before I wire this up? Thanks.

My AK4399 dual was feed SPDIF data to AK 4118.

However if i would like to input IIS instead of SPDIF, how to?


Any diagram? Thx

Hi
Selling Najda DSP unit, fully functional, in nice casing with special made front.
When interested please PM me, can send pics, price is fixed, 500 Euro.
Shipping in Europe only, cost of shipping for buyer.
Tojoko.

Hi,

Does anyone knows what drivers for mid/bass and treble are used in Philips Fidelio PS1/12?

Thanks

Hello to all this is my first post on this forum. I own a MARANTZ CD5005 and I have done following upgrade:

• Changed all electrolytic capacitors of the analog and digital PSU. I added also some bypass (Audyn QS6 0.47 uF and Chinese MKP 400 V 1.5 uF). I have substituted N4003 Diodes with UF4007 (I had already) and for the output stage I have used Schottky diodes. Moreover I have bought from aliexpress some discrete voltage regulator and they works great.
  LINK: Hi end Class DC to DC Transistor Discrete Linear High Speed Regulator Module Voltage Regulator Replace LM78XX Upgrade LT317|Battery Accessories| - AliExpress
• Changed all the electrolytic capacitors of the digital board inclusive the ones the DAC (Elna Silmic II oversized). This was the first big tremendous step in having a wide stage and monster bass...my neighbor have noted...🙂
• Changed all the Mylar capacitor of the output stage with Amtrans AMCH, changed all resistors with PRP PR9372 Series Metal film, changed all electrolytic with Nichicon KZ and SIMIC II, de soldered the SMD opamp NJM2068 and installed discrete Op amp bought in aliexpress. (1pcs HIFI OP03 Full Discrete Component Field Effect Input Dual Op Amp Module Model Parts|Parts & Accessories| - AliExpress Used 10uF Audyn cap QS6 decoupling capacitor instead of the 100uf electrolytic.

The sound is great, the speed, the details, also the softness...but is still digital some how in the high range (violins and trumpets for examples).
I have also used bitumen pads where I could , changed analog power supply cable with a shielded one and used some ferrite rings.

I would like to improve the clock. I have also measured with the oscilloscope the clock and it does not seem very stable you can see in the video as soon as I am being able to attached it.

I have written to Tent labs and Guido told me that its clock is not compatible with 1.8V power supply of the IC27 CDCE913PWR.
On the other side Fidelity audio suggested me to buy their C3 PRO Low Jitter Clock...
I have measured a Clock signal at pin 11 of IC27 and it has a Vpp of about 3.2V... IC27 power internal power supply is 1.8V , but the chip uses for teh outputs 3.3 V power supply, so I imagine that the output clock of Vpp 3.2 V is been supllied from 3.3V
What I can do to improve the clock..
Can anyone help me?
Thanks to all.


CD5005 tweakings fotos:





Video Clock Signal
https://mega.nz/file/2kp3wYrZ#1Xr1gYQw5BFdsH7usXMYZ9Eg_KbGV-IZd_4qMTrBT4s


Image of clock wiring

Dipoles! Perhaps someone could help me with something I've been struggling to understand?

It's clear with a simple baffle that level will drop around 6dB/octave as cancellation occurs dependent on baffle size.

Now take the situation of a box with a driver on the front and back, the rear driver in reversed polarity. No pressure change inside the cabinet will allow the drivers to extend down to their fs. Their Qts could be managed or increased by either adding series R or placing a baffle between the driver internally with an acoustic resistance?

So cancellation between the rear of the drivers is avoided and the "transmission line" distance between them will limit the usable frequency response. The polar response is easily plotted with simulation programmes...

But. Finally. Here's my question!! Clearly there will now be a delay between the wave travelling around the cabinet to cancel with the rear driver so how is it possible to predict the bass frequency response given the driver implementation is now different to the flat baffle example. Am I getting close thinking it's now equivalent to the front baffle width + 2 x half (1 x full cabinet depth!) the cabinet depth? But of course that doesn't take into account the delay time between the drivers due to horizontal separation....or does it !! Confused!

I am wondering what makes a MOSFET a good MOSFET as a buffer to drive the grid of a power tube (aka "PowerDrive")?

The older Tubelab docs show the 2SK2700, which is obsolete. The newer Baby Huey uses the STU9HN65M2 or FQFP2N60C parts. I am not surprised that these are N-channel high-voltage parts.

What other specs are important when choosing a MOSFET for the driver stage?

I want to create a acoustical system with both the cardioid radiation of a resistance enclosure, coupled with a quarter wave tube tuned to the driver Fs. Which one of the two models, 1 and 2, correspond better to the design intention?

Hi,

I have broken power amp in integrated Accuphase E460. Power mosfets are obsolete 2SJ618 / 2SK3497. I replaced it with FQA36P15 / 28N15 used by Acu in newest E800 integrated amp. The main problem is with biasing. New mosfets need more biasing voltage (Vgs(th) is 2x higher). So I change the R11 to higher value. Everything works but in this case drivers (2SA1837/C4793) dissipating too much and have about 70*C (38*C with standard biasing voltage). I thought to change them to mosfets like IRF610/9610, they have the same pinout but Vgs(th) similar to new output mosfets. It could work without problems ? I will be grateful for help. Schematics below are from E550 not E460, but they are the same like in 460, only rail voltages are 2x higher.

Unit powers up and works .

But it seems like the sub outputs are muted very low output .

Any ideas on where to start ?

I am teaching myself how to design and build amplifiers and I started by replicating the input/VAS in Sloane Figure 4.10a on a breadboard. I have a Tektronix 2246A scope, an Instek GPE-3323 power supply (channel A common grounded, channel B positive grounded for +/- rail voltage) and an Instek GAG-810 signal generator and a handful of DMM's. All the bench equipment is plugged into the wall grounded.

The figure indicates the scope, signal generator and +/- power grounded, which I assume is the earth ground on the equipment plugs. But where do the circuit grounds (transistor collector, NFB and input) get connected? When I float the rail voltages, all the voltages check with the LTspice readings. However, if I connect the circuit ground to the power supply earth (green plug) things go haywire. If I raise the voltage beyond 10 volts or if I touch the input ground with a DMM lead, the Instek power supply trips to constant current and the voltage drops.

I'd appreciate any help on how to properly set up the test equipment because I have checked and tripled check the connections and they are correct.

There is scarce availability of horns for 2" compression drivers without 18TPI screw on adapters.

I'm running my driver at very low SPL but would like to experiment with a wider range of horns. The airflow diameter will be restricted before opening up in this scenario.

I purchased ADM25-50, hoping to couple the horn with drivers, but this adapter is meant to be used the other way around.

Do you know where to find a 1 3/8 male-to-male threaded coupler?

Thanks in advance!

With the Allo Piano 2.1 on a Pi3B the gpio available gives i2c connections for sda and scl.... there is a gnd and 5v too but the i2c backpack is 3.3v for the Pi gpio compatibility.

I have cut the backpack traces so as to feed 5v to the 20x4 lcd and so need 3.3v for the backpack operation.

Can I supply the 3.3v from another supply ? gnds tied together.

Or does the 3.3 need to be Pi derived ?
In which case can I use an Ams1117 to drop the 5v from the allo hat and gnd to give 3.3v for the backpack...?
5pcs DC/DC 4.5V-7V to 3.3V AMS1117-3.3V Power Supply Module Voltage Regulator | eBay

Seeking some advice and opinions.

I've been designing amp attenuators on the Marshall forum, and there's been quite a few successful builds. These take a signal from the amp OT, send it trough a switched network of inductor and resistors, to go to the speaker. It works great but so far there's no line-out. Also, I'm not contecting to any chassis or ground so far.

The attenuator can be used as a load box too, and id like to put up a simple and versatile line out, to go to external cab sim, IR box or mixer. Some such units do this just with a pot and resistor to make an unbalanced output, others like Suhr use a transformer and give a balanced option to an XLR socket. Im thinking it should be possible to get balanced, without a transformer

What are your views? and what about grounding?

I was thinking about using a balanced resistor circuit to feed a reduced signal derived from each end of the OT, to the hot and cold pins of an XLR. The XLR ground could be referenced by equal resistors to half way from hot to cold, or maybe lifted?

I am looking for the Transcendent Sound T16 OTL Amp Schematic and or Manual.
Contacted TS and Bruce expressed no interest in my request.

Thanks

After the last changes in amplification (right now), I have a lot of good tubes that I’m not going to use, so I post them for sale. Al lof them are in perfect working condition and barely uses because I had several amps. All of them are paired pairs or quads. If there is any interest, please, let me know:

Svetlana C Winged EL34 paired Quad. Paired and selected by TAD, al lof them come from the same production batch. Perfect working condition and used less than 100 hours.
Price for the Quad 160€


SYLVANIA 6SN7GTB Quad or two pairs. NOS tubes paired as a quad that I can Split into 2 pairs. Uses for 30 hours. Very strong values as printed in the tubes. Original NOS tubes from the 60s imported from USA.
Price por a pair: 60€
Price for a Quad: 100€


SYLVANIA 6SL7GT pair. “JAN” (Joint Army Navy) grade.
SOLD

General Electric 6SL7GT pair. NOS tubes imported from USA. Used for 80 hours.
Price for the pair: 60€



ONE BRIMAR 6SN7GT NOS made in England. NOS tube in perfect condition (used 20 hours) very hard to find. The best batch with Orange printings.
Price: 40€


GE 5AR4 / GZ34 Quad.
SOLD

Pair of Genalex Gold Lion KT88 Reissue (Russian made). Paired and used for 150 hours.
Price for the pair: 70€


Electro Harmonix KT88 NEW. Never used. In original box . Price 30€



Pairr of Shuguang KT88 (G.E.C. copy) used for 200 hours. Great quality. 25€ for the pair


12FQ7 Pair. One National made in Hungary. Second one should be too, but markings has gone. Used for 300 hours.
Price for the pair: 25€


12BH7A-STR pair. Used for 200 hours. Price for the pair 25€

SbAcoustics Satori Berillyum TW29BN

Hello.
In this 2021 I promised to retire, so here, for sale some NEW, aboslutely NEW, never used, not installed, not measured. Boxes only opened for pictures purpose.

1 pair Satori TW29BN-B 8 ohm

1 pair Satori TW29BN-B 4 ohm

Neither of them has been installed or measured.
Absolutely new in box.
Retail price for these magnificent tweeters is more than 600€ for a pair.
Asking 430€ plus fees and shipping.

Some pictures:

Why does my phono preamp have two output coupling capacitors, while my preamplifier has four input coupling capacitors? I hope I said that right, feel free to correct.

I have a fine pair of drivers that came with this mechanical drawing in a pdf file. But it I print it out it looks like it is only half scale and I would like full size printout to help with drilling. I know the PDF reader has some resizing capabilities but it says the current image is 117 % and it will only enlarge to 200% and even then it only prints roughly 1/2 the image. Anyone able to help me with a quick file conversion ?

Hello from Vancouver .... LONG time lurker, I believe this is my first post.


A few years ago I rebuilt a Sony TAN 8550 VFET power amp.


To be honest, I was never blown away.
Not enough low end grunt, given the power, size of the transformer, etc.


I recently came across some Mundorf low ESR high current filter caps and wonder if they might help the cause?


I've used their filter caps before in Luxman products, and was very happy.


My question ... can a low ESR, high current cap transfer TOO much current to the VFETs (10,000 uf) and damage them, or make them run hotter? Because they run pretty hot as it is.



Do caps in any way limit current and act as protection for the VFETs?


These transistors are unobtanium, hence the question.


Many thanks!

I have to pull out this circuit board in a 17-year-old Belles 21A preamp for a relay switch repair. Should I consider preventive maintenance by replacing or upgrading any of these four electrolytic capacitors that are near the power supply transformers and heat sinks?


The top blue cap is 1500uF 250V.
The top black cap is 100uF 250V
The bottom blue cap is 220uF 35V
The bottom black cap is 2200uF 35V

This is a crossover from a BIC America V-820 2-way speaker made in 1994. I want to know: 1) are both orange-yellow caps bipolar/not polarized? 2) are they the type they call electrolytic? 3)What does the blue one do, what type is it, and what does "4.5K 100V MER CH" mean? Accepting any and all advice on cap upgrades. Thanks!