SOLD. Thanks!

Hi, this is an Amanero Combo384 purchased in 2015 directly from the company. Unopened!

AUD60 (EFT), EUR40 (SEPA), USD46 (Paypal) includes shipping to those respective locations. (Other locations pse enquire)

Pair completed boards from Hugh Dean from Aspen audio.SOLD AS IS!!!The biards are good in function,you must provide your own heatsinks and psu becose on board there are no more diodes or capacitors,also the red jantzen input caps are not more on boards and the nichicon kg also not.The price is becose of this inly 50 euro for bouth boards plus shipping inside EU that will be abouth 15-25 euro registered.Payment paypal by friends.

Amp appears to be working but no audio. I'm getting waves every where they should be. Just no audio.

Hello everybody 🙂

Can someone help me with the datasheet for these glorious triodes?
Whats a good sweet spot?

Ideally I'd like ~300W , load 10k , no Tubelab's PowerDrive

https://frank.pocnet.net/sheets/049/8/8000.pdf

Cheers

​

I'm looking into building either one or two 18" subs for home theater application, but will likely also serve double duty as subs for inside my Sprinter van on occasion.
I've never had any sub in home or car more than 12", and the goal is to get some really deep bass that can be "felt", yet still maintain a fair level of SQL.
I'd like the boxes to be not obnoxiously large or heavy, so probably somewhere between 4-8 cu.ft. for each driver.
So, for these drivers and probably any other inexpensive 18" driver (or larger) I am looking at sealed boxes.
Crown XLS 2502 is available to power the HT, and SoundQubed Q1-1200.2 available as power for van application.

I saw UM 18 for $288 recently which seemed like a great deal, but then stumbled upon the SI HT-18's in forum discussions and they seem very promising for $200.

Does anybody have direct experience with both of these in sealed box applications in the size range I am looking to build? It would be great to have an "apples-to-apples" comparison is anybody had experimented with each of these in identical boxes with identical power. I know this kind of thing can be modeled in software, but I am more interested in getting some feedback from an actual person experiencing them first-hand.
For the price of 2 UM, I could get 3 SI, but since I wouldn't use 3 drivers I guess the question becomes are the UM worth $600 vs $400 for the SI's?
Also, if it turned out that only one would up in my house and only one in the van, then would the SI handle enough power and provide similar output as the UM?

Thanks

I picked up a BAT VK-5i preamp that has a hum problem in the left channel. I found a schematic of the amplification circuitry, but I don't have any info on the input selection, volume control, power supply, etc. I haven't started digging into the potential problem(s) yet, but I'd appreciate any information anyone might have on documentation, similar problems, etc.

The preamp was sent in for service to BAT a few months ago and received new tubes and some cap replacements. But it started humming again within a month or so of getting it back. The previous owner decided it wasn't worth continuing to try to fix it, so he sold it to me as is.

I've become interested in in IanCanada's work.

I have a new DAC and Amp on the way. Which is High quality for me; Emotiva XDA-3-DAC-balanced, Emotiva XPA-1 balanced Monoblock's.

I am currently using Amazon Music, Firestick, and an older Marantz receiver SR7002, and some fairly decent Towers with good tweeters Carnegie-CST-1.

I understand recently now, that ROON and such does not accept Amazon music.

I enjoy having time with each stage of improvements.

As the next stage of listening;
It looks like initially; I will be feeding Amazon > the Marantz Receiver > digital coax to the new coming balanced DAC > balanced amps.

For one of the next stages, would IanCanada's devices be able to receive HDMI feed from the Amazon firestick? or am I missing the point?
Perhaps the Ian devices accept ethernet only? and will then need ROON and the other things that come with that?

I currently have an NVIDIA shield still in the box that I'm debating to return. I understand the NVIDIA shield $200, will accept Amazon music, and feed digital to the new coming DAC.

Advice?

150 watts into 4 ohms.
Comes with circuit diagram, power supply diagram and parts list.
£30 for both plus £5 p+p to UK or £20 p+p rest of world.

Hi every one!
I have a subwoofer Class D plateamplifier in a Audio Physics Rhea 2. Original amp is dead and i have replaced it with one Similar but not excatly same. Ut Works fine, except for it making some hum at speaker output. Could this be cause by the blue components in picture? The original amp do not have them and was complete ly quiet. Could i Just remove them for a try out?

I hope someone can offer advice to an inexperienced DiY audio tech.

I've recently come to own a Denon AU-320 step-up transformer. When connected to my phono pre-amp the signal will pass through successfully. That is the Pre-amp is set to its usual MC setting and the signal from my tone-arm passes through the AU-320 to the pre-amp and on down the line as usual. This seems to indicate the wiring of the left and right channels, from input to output are correct.

When I switch the Au-320 to use the transformers (and my pre-amp to MM) - either in 3ohm or 40omh settings, the left channel of audio drops out.
Any ideas what might cause this?

Here is more information about this unit: https://audio-database.com/DENON-COLUMBIA/etc/au-320-e.html

I've opened it up and removed the transformer, cleaned what I can with deoxit. The wiring looks original and I don't see any breaks... but if there were a break... where might it be to impact both 3ohm or 40omh settings and not the signal passthrough?

Thanks everyone.

I've got a question.

Does anyone know of a circuit that can take the vertical or horizontal sync pulse from a VGA signal and generate a sawtooth waveform?

I've got a project where I am wanting to display a VGA signal on a Tektronix XY display and want to have at least two resolutions.

720 X 576 for 5:4 displays and 800 X 600 for 4:3 displays.

The idea is I want the sawtooth waveforms to automatically switch frequencies if possible.

I could even use a switch to select two frequencies if need be, however I need to know what those frequencies need to be.

I've got a Leitch FR-684 video distribution frame that can hold 10 cards and two have daughter boards that plug in and I was going to use those two for the sawtooth generation and a third for the video as the output from the card will have the proper levels so that the displayed image looks its best.

Hello friends,

I'm owning a NewClassD Neutrino crystal oscillator generating 12.288 MHz. Due to a forced change in my project (system failure that cannot be repaired at reasonable cost) I would now need the oscillator to generate 24.576 MHz. This should be possible by changing the crystal, so I tried to find out which 12.288 MHz crystal is used on the board. Unfortunately NewClassD seems to have disappeared, so I cannot ask them...

The marking just sais "122 ADIF" which I was sadly unable to find on the web. And so I'm asking for help here to identify the crystal used and to find out with which (ideally compatible) 24.576 MHz part I could replace it.



Thanks so much for any help you can provide!
Regards,
Winfried

Allen & Heath ZED 14 mixer, schematic here:
https://www.manualslib.com/manual/2457417/Allen-And-Heath-Zed-14-2.html?page=14#manual

Is it worth it -- even a little bit -- to upgrade any of the TL072 opamps to something more snazzy? Asking mostly to learn why not, but if there is even a small benefit, I guess even great opamps are like $20. I would consider doing it on one mic pre. I asked this same question about a much worse mixer, but this one is already good. Any thoughts?

A couple of months ago I picked up a pair of over-priced derelict Dynaco MK-III tube amps.

They didn't have any rectifiers or power tubes, and one of them had a pretty well over-heated choke which had kakked its sealing wax all over the inside of the bottom cover.
So rather than trying to get them functional I decided to simply strip them down and start over. The power and output transformers were good, and that's really all I needed.

The chassis are both fairly pitted, and there isn't much that can be done about that, and a liberal application of metal polish didn't erase the pits, but these are not meant to be show pieces, they're meant to be working examples in my primary system.

My plan is as follows:
Modify the input circuit to get rid of the admittedly not-that-good-sounding 6AN8 input/phase splitter tube.
I settled on an elegant input circuit designed by Kara Chaffee and written up in an article in AudioXPress, March 2001.
It uses 1/2 of a 12AT7 (a tube I really like the sound of) as the input stage and a 6CG7 dual triode as a long-tailed pair phase splitter. It also has a clever variable feedback circuit.
Retain the tube rectification, which I think is important.
Remove the selenium stack and replace it with a modern diode.
Remove the can capacitor and replace it with a modern replacement circuit - I chose the design from Sheldon Stokes's "SDS" Cap Board having had positive experiences with it on previous Stereo-70 restorations.
Install modern ceramic tube sockets, and replace all the ancillaries - switch, speaker terminals, input jack, power cord - with new modern equivalents.
Remove the redundant wiring for powering a partnering preamp from the front panel socket but keep that socket for bias measurement.

So step 1 is done - strip the chassis, remove all the tube sockets. This particular amp was factory built, and the sockets were riveted, so those had to be drilled out.
(photos of the "before" are not the amp in question - this clearly was not factory built, but is in very similar condition to its mate which is the stripped chassis)

Comments are welcome.

This is spurred by post #48 at
https://www.audiosciencereview.com/forum/index.php?threads/human-speakers-81-dk-review.50915/page-3
"The woofer is supposed to naturally roll off ...in order to gentle cross with the tweeter that uses a single capacitor as the whole filter crossover" to which I replied "Once upon a time, I made something like that. And recall some drivers like that. Nowadays, I've been looking at a lot of different types and sizes of woofers and NADA. Nothing seems to roll off smoothly any more."
?!?
Am I blind? Missing something? Everything seems to have resonances on the top end and gyrations in frequency response...

Hi,
Can I put a switch to bypass the EQ section of a tube preamp (ON-ON, 6 legs switch I guess?)?

Here is the EQ:


I can provide the full schematic if needed.

Hello, i have a small sub and i connected with audio eng A1 the thing is i am note sure i can tell the difference , the small sub is the yamaha https://www.ebay.ca/itm/295322537940

Is any reall difference between the 2 in music, can someone feel the difference ?

Objective: check the square wave output of 10w amp design.
I've copied from Mike Engelhardt quick start video which uses "pulse 0 1 0 1u 1u .5m 1m" expression
I also include:
.tran 3
.plot V(out)
.four 1K V(out)
Result-
Fatal error: This .four requires 0.001 second of time but only 0 second was simulate

1) I'm wondering if I'm misinterpreting the QSpice quick start guide!
2) I placed a 6ohm resister load to OUT - should I delete this? Without shows a broken square wave of sorts!

Thanks

Hi the ones on ebay like this https://www.ebay.co.uk/itm/284655593945 apols about the spam but at least known.
I have a question as the ouputs have a positive / negative and a ground?
How do you wire the speakers up IE positive/negative of the speaker cable should go to which when used a stereo amp?
Is it so if you where going to use it in bridge mode, it has x3 connectors for each channel output?
Edit apols a rooted out my better reading specs.
Its L+/L- V+/Gnd R-/R+ it was my eyes, apols.

Hi I'm looking for some kind soul to facilitate the buying of some phono sockets from ebay.com as they won't ship to the UK.

Can any one help? You will need to be US based to purchase

Thanks

Chris

I've been tinkering with audio gear mods for years. My current modding project (a Sony QS-series SACD player) has two electrolytics in the signal path, one after the DAC I/U-converter stage, and one after the differential opamp stage. I started thinking on the possibility to remove the signal path electrolytics altogether.

So, how much DC offset is too much, so that you would not remove the signal path electrolytic capacitors? 1 mV or what?

Folks,

I've been building this 300B amp for the past year or so. I want to use regulated DC for the filaments. I have done the math on linear regulators and found that I will end up dissipating more power in the filament regulators under worst case conditions than the amp will deliver to the speakers. I find that ridiculous... Needless to say, I started dabbling in switchmode regulators. They actually work really well...

So I was thinking. Wouldn't it be nice with a universal switchmode filament regulator? Universal, as in programmable by a resistor change to different output voltages. I'm thinking to support 2.5 V for 2A3 and the like, 4.1 V for the Russian tubes, 5.0 V for 300B, 6.3 V for just about everything, and 12.6 V for the tubes with series filaments.

Are there any other common filament voltages that should be supported?

I'm thinking to use an LM3102 as it allows me to hit the above voltages without too much fuzz. Its max output current is 2.5 A (just enough for a 2A3 I think). It's also in a package that's hand-solderable by most humans.

I'm throwing this out there to get the process started and to gauge the level of interest in such a project.

~Tom

THIS GROUP BUY IS OFFICIALLY CLOSED

Since I'm a glutton for punishment, and I don't want to leave anyone out:

This is an ACA Mini PCB with artwork designed by Mark Johnson following the Nelson Pass circuit. It is very close to the artwork released by Nelson Pass for the boards which were given to some lucky participants of the Burning Amp Festival. Mark was gracious enough to produce a number of his boards and give them away: I was one of those recipients. I have built the amp using this "Almost Clone" board and it works and sounds fantastic. It was suggested that a group buy for this "Almost Clone" board get started...so here we are.

This group buy will run with the quantity limited to 20, and the time limited to two weeks, whichever comes first. This thread is for those OUTSIDE OF THE CONTINENTAL U.S. ONLY. If you live within the CONTINENTAL US please post HERE.

Photo's of a completed amp can be viewed in the ACA Mini thread #462

Of course you will be using the Nelson Pass article for a description of the circuit, build guide, and biasing instructions found at the beginning of the ACA Mini thread #1

Cost of the board will be $12 with you paying the actual shipping cost from my address in Hudsonville, Michigan 49426 USA. Please check the actual shipping cost before adding your name to the list.

To purchase a board simply copy the post with the current list of names, add your name and quantity, update the total, and paste to new post.

This Group Buy will end on January 22, 2022 at 12:00pm EST

Thanks for looking,
Kevin

Hi all,

I am just putting the finishing touches on a Dual PSU Aleph J. It is my second Firstwatt Clone build, the first being an F6 that went off without incident and has been running great for about 2 years now. I have following the build guide, and the same procedure as the first time, but this time around when I powered up the amp for the first time, LED 2 on one of the amp boards is blinking. The other amp board seems to be functioning normally. I have attached images to show how everything is currently wired up, please excuse the mess as I will be tidying everything up once it's all functioning and biased.

I have inspected all the components to the best of my ability and everything seems to be oriented correctly. I couldn't find any cold solders either. I tested both PSUs prior to assembly, and found a consistent reading of 24.6VDC and -24.6VDC respectively on both PSU boards. My lightbulb tester also behaves normally when the amp boards are disconnected, but the lightbulb dips and then goes full bright when one or both amp boards are connected.

Does anyone have any ides of what it could be? Am I missing something super obvious because I have been looking at the amp for too long today? Any assistance would be greatly appreciated as I am totally stumped.

Thanks so much and feel free to ask any follow up questions. I will keep an eye on the thread and respond asap.

Cheers

Hi guys, have any of you used this DSP? can you help me with room correction settings, because I tried to follow something like this video, but after activating "AutoQ and after L+R... nothing happens because it goes back. Maybe it has incorrect settings?

Hi, I have a pair of Sun Audio SV-300B mk2 amps which I guess are around 25 years old now.
They sound clear and detailed, but have a slighty forced edginess to the sound at times which I would like to improve on.

Most of the caps fitted are the original electrolytics and I'm interested to see if I can get an improvement in the sound by changing them all out for MKP film caps, so no electrolytics anywhere.
The general advice has always seemed to be "sure, that would be nice, but they will be huge and expensive" but it seems like that is not necessarily the case any more. Plus, in a simple amp design with mostly point to point wiring, there is some room to be creative with placement.

So I have got myself a load of Kemet C4AQ caps as they come in the specs I want at reasonable sizes/prices and they seem to be well regarded here.
I am now planning out how best to approach this.
I don't want to entirely bastardise these lovely amps, but it seems like I can probably do this in such a way as they look identical externally and if it's not a success, this change can always be reversed if I want.

I'm interested in any general advice on the plan, whether there's any considerations I may have missed, and any practical tips for working with these type of caps, like how others have mounted them. I may make some hold-down straps, or I'm wondering whether sticky pads or glue onto the flat chassis plus the soldered connection could be mechanically sufficient for most of them. I'd like to understand whether all 4 legs should be connected or can I snip/bend 2 of them out the way. That kind of thing.

here's the schematic


here's the existing layout internally



47uf+47uf cap from the CLC and the 2 x 100uf 300B cathode resistors poke out the chassis at the top, but they take up little room internally so can probably stay in place (disconnected)



Here's a very rough test-fit of how the C4AQ caps could be placed (bottom left ones will fit further in with the electrolytics removed). It'll be tight in places, but it looks totally practical to get them where I want.




I feel I should assess the 47uf + 47uf in the B+ CLC whilst I do this as the Power Transformer gets quite hot in use and I wonder if that's cos 47uf is a bit large for a 5U4G input cap. So maybe that will end up being 40uf + 75uf instead. I have some different capacity options coming and plan to scope the various ripples.

The voltage ratings for the cathode bypass caps are excessive, but if they physically fit (which they do) is there any negative to that?
What do you think?
Any input gratefully received 🙂

Famous Partridge DK 7441 SE OPT for sale. The DK7441 is the "unpoted" Version of the TK 7441 (Primary 2k3/3k5).
Asking EUR 1500.-

I would like to use the parts I have for DIY PSX, I have 25v & 35v Toroidal transformers. Below is the schematic I intend to use. My questions are

1. 25v toroid will give me 35v DC, which is less than the original transformer voltage inside the Cyrus 2, and 5v less than PSX, will it be a pointless exercise building an external power supply like this?
2. 35v Toroid will give me 50v DC, which is 10v more than supplied by PSX, will it blow the Cyrus 2?

Any help would be appreciated.

I used Toshiba jfet's in my pro audio product designs for over 25 years. I am now retired and I still have a large selection of the following real Toshiba JFETs..

2SK170 BL and GR sorted (Vgs using 49.9 and 22 ohm source resistors) and unsorted, many of them still in sealed bags of 200 ea.
2SK74 BL and GR sorted
2SK389 BL (pulls, tested)
2SJ109 BL (pulls, tested AND NOS in sealed bags of 200 ea)

The pulls came from older products that were going to be thown away. We pull the Toshiba JFETs off using a hot-air rework station.

These are the real thing. I purchased them 9,000 at a time (boxes of 3,000).

If any one is interested in buying some of these, let me know. I'm not interested in selling one's and two's of these parts, so please don't ask.

Fred Forssell
fred (at) forsselltech.com

Would you please recommend a switching solutions how to select 2 amps with one set speakers

Is It better to use switch or relay solution

I am looking for an inexpensive pre-built high voltage field coil speaker power supply. I have a couple of Jensen A12's with 5 to 6k ohm coils, so I am looking for a DC supply about 300 Volts and 100 ma, adjustable voltage or current.

I can see some HP instrument supplies like the HP 6186B DC Supply and also Fisher Biotech FB 650. Since the high impedance coils require low current, I would think the HP lab supplies might work well. The Fisher Biotech supply is for electrophoresis and biology research, so there are a lot of these high voltage DC supplies available since they are used widely to induce gradients in gel beds.

Deep within other PSU discussions a poster mentioned the Fisher FB 650 was a heavy iron design and might have better quality power than other modern circuits. I am not ready to build or purchase a high fidelity PSU and would like to just start with a good quality used supply borrowed from another industry or purpose.

Any ideas?

Jamie

Can’t find anything meaningfully more powerful than the good old B&Q 1000ASP (600W @ 8 ohm). Would've thought the market would have made some progress since 2007 (power, price).

I’m looking for something on the order of a Behringer NU6000 (approx. 1,000W @8 ohm), which I have but want module format for another project.

This is for hifi (up to max 400 Hz) so no loud fan requirement.

Integrated power supply is preferred.

Hello!

I am in need of some additional gain (at minimum +12dB) but both the voltage is limited to 3 volts and it needs to be extremely basic (preferebly single FET) as to fit onto a 5x2cm veroboard.
The only control I need is volume.
The purpose is to boost the signal level of a passive electric bass.

Do you have any suggestions?

A friend of mine is a HAM operator and needed to replace this tube in his transmitter. He asked if it could be used in a home stereo amp. In his application it runs 3600VDC on the plate, and around 700ma plate current. I simply don't know.

https://www.tube-data.com/sheets/140/8/8877.pdf

When viewing a multi page thread with my phone I cannot select to go to a random page like I can with my computer I am only allowed to either go one page or right back to the beginning of the thread (page one).Is this normal or is there a fix ?

*THIS GROUP BUY IS OFFICIALLY CLOSED *

This is an ACA Mini PCB with artwork designed by Mark Johnson following the Nelson Pass circuit. It is very close to the artwork released by Nelson Pass for the boards which were given to some lucky participants of the Burning Amp Festival. Mark was gracious enough to produce a number of his boards and give them away: I was one of those recipients. I have built the amp using this "Almost Clone" board and it works and sounds fantastic. It was suggested that a group buy for this "Almost Clone" board get started...so here we are.

This group buy will run with the quantity limited to 50, and the time limited to two weeks, whichever comes first. We will be shipping to addresses within the continental US during this first group buy. Depending of the success of this buy there may be another and the parameters may be broadened to include the rest of the world. For now I'm trying to keep this thing as simple as possible.

Photo's of a completed amp can be viewed in the ACA Mini thread #462

Of course you will be using the Nelson Pass article for a description of the circuit, build guide, and biasing instructions found at the beginning of the ACA Mini thread #1

Cost of the board will be $12 with $5 in shipping to an address within the Continental USA.

To purchase a board simply copy the post with the current list of names, add your name and quantity, update the total, and paste to new post.

This Group Buy will end on January 22, 2022 at 12:00pm EST

Thanks for looking,
Kevin

I came across this and thought others' might find this interesting.
It includes building a guitar amp. I didn't do it and built my own 10W amp.
I will publish the design to the appropriate diyAudio section at a later date.

https://www.coursera.org/learn/audio-engineering?#modules

How do back to back polarised electrolytics compare with bipolars?
With back to back I can reform parts that have been sitting in a draw for years, with bipolars what happens as they sit idle?

Does anyone know of on off the shelf digital hours counter or a kit to build one that can be used to count hours of operation (for an ARC REF75SE amp)? Something that easily and automatically has a running tally of hours that the amp was turned on ? Something must exist or it looks like there are several inexpensive digital counters used for lawn tractors and similar that should be able to work for this purpose?

Anyone had opportunity to hear these drivers?

They seem to be interesting concept which seems to be working very well for pro audio purposes, especially in applications when even coverage is important.

Live CDD15 for example, seems to be highly praised, even in the same category with Meyer, L-acoustics etc...
Drivers looks to be developed with Celestion (chassis looks the same as Celestion coax-es)

I am contemplating if it would make sense to have passive variant used with A-class amp + active subwoofer.

CDD12B looks most interesting to me because starting from 12" and 15" cabinets are made out of birch plywood:

Hi all

I have a pair of SB MW19P-4 and SB TW29R-4 sitting on a shelf doing nothing which is starting to annoy me. Though I managed to get them just under half price, unused via auction, they are a pretty expensive driver for me personally to justify not using. They were meant for an active 3 way that never got off the ground. With that in mind I have decided to build a passive 2 way with them, something similar to Troels MW19P-8.

I fancy a large stand mount with a port tuning as low as feasibly possible (volume maybe 28 litres, larger floorstander if needed). I really want to use these drivers, so I am not willing to move to different drivers etc, other than that one point I am pretty flexible. I am open to correction but am pretty sure that the volume of the enclosure will directly effect sensitivty of the mid driver output and will need to be pinned down before looking into a crossover, in order to match the tweeter level.

Some googling has been done, I can't find any crossover designs for these drivers. It looks like I will need to come up with some form of design myself, I have no experience but am not afraid of maths so bring it on. I noticed this sticky: https://www.diyaudio.com/community/...igning-crossovers-without-measurement.189847/ which seems to have all the information I need, I plan to use it to design the crossover.

Overall, I want to get these driving producing music for me and have a fun build, I don't expect to have a 100% optimal crossover design. Troels crosses his speaker at 1.7khz using an LR4, from my understanding this is far more complicated and expensive than crossing at a higher frequency (which I understand may be suboptimal in comparison). Many seem to cross these Satori's around 1.8khz - 2.2khz for various applications.

So that is where I am, if anyone can answer either of my two questions that'd be great 🙂

Questions:

* Does anybody know of a crossover design from a previous project on any forums etc that would suit the drivers I am using?

* I don't expect the speaker to perform like a subwoofer but would like to get as much low end as possible. I am not restricted on volume so a 60 litre floorstander is not out of the question. I would like opinions on how much volume and how low I can design F3 before compromising the quality and consistency of the upper frequency output of the mid driver?

Thanks all

question 1: I was looking at the NE5532 datasheet and I can see typical supply current is around 8mA. (30V(?) * 8mA = .24W each)

assuming I have 30 NE5532 chips in the circuit, I somehow doubt I only need a <15W transformer (with headroom added in)?

------------

question2: is there a better specced drop-in alternative that's still inexpensive? (example: I saw that the OPA1612 is also a bipolar input that may be ok BUT it's like 8-10x the price as well)

Thanks for the assistance.

For sale are two speakers equipped with AudioNirvana Super 15 Alnico on the front and IMG Stageline (Monacor) 18" SPA-45PA on the back.
The cabinet was built by a local carpenter from 23mm birch plywood to the specifications of Dave Dicks (commonsenseaudio) (€600). It is the 8.0 (8 feet³) with external dimensions of 49x53x113cm. The surface is so far untreated and in very good condition. The speakers were finished at the end of 2019.
I bought the Audio Nirvana chasis from Dave in June 2019 (€1500,- including taxes and freight). The IMG stagelines (€400,-) are a few years older and were intended for an open baffle subwoofer, but that didn't work with my setup options. They are more or less unused.
Originally, the speakers were built to Dave's specifications as a bass reflex, but with that, there was hardly any bass possible....
It has been shown with the support of the forum (thanks again to Scottmoos and others) that the Super 15 Alnico are better suited for open baffle than for bass reflex.
So I have removed the rear panel. That was soundwise significantly better but still little bass.
Then I separated the cabinet in the middle by another bottom and installed the bass in a split rear panel. After attempts with ready-made crossovers that did not fit right, I disconnected the bass again and let the Super 15 run solo.
This already works really well. Ambitious professionals could get a lot more out of it with a miniDSP 2x4 or so and the right amps.The long backs are of course still available too.
Dave says "these are the best speakers in the world" 😉 . Meanwhile there are only the Super 15 ferrit at Dave, don't ask me why...

Conclusion: These speakers are only sold locally to collectors because of the weight and size. I could possibly deliver within a radius of 200km (Germany PLZ88481).
I hope this works out, if not we see further....
It would be a pity if the housings become high end rabbit hutches... hahaha

I am open to serious offers!
Please do not beg 😎

Anyone tried the cheap pascal modules. They are used it seems


DKK171.50 53%OFF | S-pro2 500Wx2 Top Audio Power Amplifier Board Power Amp Board Hifi Digital Amplifier Board Module
https://a.aliexpress.com/_EQ0Kdqv

Here is a thinking exercise for the FR gurus. I don't like wearing headphones, and not only because of interference with eyeglasses. I find the cut-off experience a bit unpleasant too

I am working on a project for speakers that I can place very close to the head for quiet night listening and sharing the experience with my partner. There is a thread re this in subwoofers called tiny 40hz sub. Time to sort out the satellites

Source is a headphone output, and I would like to mess with attaching some FR speakers directly to that. When I was a kid, I would buy those small stereo speaker set from the two dollar shops that have a 3.5 plug like headphones. These would be just audible when hooked up to a Walkman

I would like to plan some strategies to set up a proper version. Been looking at some mini drivers that I have access to

Visaton FRWS 5 R 2"
4x these drivers in series for total 32R per stereo channel

AIYIMA 1.5 Inch 8ohm 5W Full Range Ultra-Thin Neodymium
4x these drivers in series for total 32R per stereo channel

Hi-Res Silk Diaphragms Film Headphone Speaker Unit for AKG
8x these drivers in series and parallel gangs for total 32R per stereo channel

This is my current shortlist and approach with my limited understanding on this. Will there be a lift in system sensitivity with such an array to make the headphone output usable? Xover will be around 300hz

Any alternative approaches? Should I try to pick up the signal from the headphone out and use Class D for the stereo channels too and use a single regular FR driver?

The headphone amp is single ended tube triode 6N5P 6N5C class A

Virtually new Mackie hard disc recorder, 24 tracks simultaneous recording, mounted in Gator hard case. A number of DB25 cables for input and output are also included.

Because if bulk and lack of original box, only available for free pickup in Washington DC area (Bethesda MD).

PM if you need photos but really, since it is free, do really need the photos?

Been snowed in for a couple of days and playing around with odd ideas. Broke open a "new style" LED buld to investigate the series LED "filament" used in them.
It provide a contant voltage drop of exactly 82.7V from 8ma to 12ma. "Constant" in that I could not measure the slope with a 3-digit voltmeter, a better instrument would be needed.

Placed in the cathode circuit of a 12AU7 cathode follower replacing a 27K load, diode followed by an 11K load instead, it also made a very low distortion level-shifter, provided that the current was around 10ma quiestent.

I've looked around for any information on these kinds of uses, but haven't found any. Has anyone else experimented with these?

Thanks...

Might be a simple question for experts; but I'm not one of those.
My beloved loves fairylights and I need to resting the lights for next weeks party but the PSU's for half of them have died.
The little sealed units are marked as 240V in and 31V out AC
As I have all those cheap sub amplifier boards in the shed that are not worth repairing and all have good toroids what is the easiest way to wire up a power supply for the LED strings?
No flashing needed just On/Off
Now I have 28V toroids and 42V toroids and I'm assuming that 42V is too much. These toroids have three wires, two Red and one black and are marked 28-0-28.
I build speakers so working with 240 volts isn't my strong point but I'm in a hurry to get these lights up to please SWMBO
Secondly what effect would using 42V have apart from making the lights brighter? Much lower lifespan or would they simply burn out immediately?
Help needed and appreciated so TIA

Dear all,
I own a Cyrus 2 with a slightly defective volume pot that at very low level plays only the left channel.
I know it is quite difficult to find the spare part so I would like to know if there is any compatible component that can replace the original potentiometer, even loosing the balance control, which I almost never use.

Thank you for your support
Gaetano

Hi all. Recently bought a Fiio K7 non-BT version and a pair of DT700 Pro X and ATH R70X. Bought the non-BT version because it was way cheaper and I thought Bluetooth won't have much of a use since my headphones will be plugged into the K7 anyways. Alas was I wrong.

K7 comes with a usb 2.0 type b to type a cable. I plugged the cable into my android phone using an otg adapter, but the music would pause if there was any slight movement in the otg connection. Tried multiple otg adaptors but nothing worked. Bought a usb 2.0 type b to type c cable and it solved the issues for a while but again the music has started pausing with slight cable movement. I am unable to isolate the issue. What should I do. Please help, the good people of DIY AUDIO.

PS: I own a 150 dollar samsung phone. Nothing too fancy. The cables and otg connectors were all amazon bought, nothing Hi-fi.

A lot of Teslas just aren't working in the very low temperatures now covering much of the US.

https://www.msn.com/en-us/autos/new...&cvid=aa6ce07ace9944b8aa6450a66cc321a5&ei=279

As the article points out: "Electric vehicles don’t produce as much heat as regular internal-combustion vehicles, which means that an EV has to use some of its battery power to warm the car. Furthermore, chemical reactions are slowed or even stopped in cold temperatures creating an additional obstacle for the battery to overcome."

So rather than being able to use the excess heat from an internal combution engine to warm the interior you have to use current from the battery to warm it, which just drains the battery down even faster.

Not a good combination of things. And people are just abandoning their electric cars at the charging stations because the they can't run.

Hi,
I will be building a DAC / streamer that will have 3 power transformers feeding 3 power supplies and I'm looking for examples or advice on how best to wire the transformers to a power switch.

My previous projects only had 1 power transformer so wiring was more straight forward.
My plan was to go from IEC connector to a fuse then to power switch and from there to the transformers.

Do you use some type of power distribution block after the switch or just solder and heat shrink all the hot wires together?

I will be using (3) Avel Lindburg Y23 toroidal transformers.

Do you recommend a separate fuse for each power supply?

Thanks for the help!

Scott

Hi,
I am looking for a pcb for the SERVO 50 driver board from Erno Borbely. If anyone can offer a pcb foil pattern, gerbers files or possibly a finished pcb for sale?

Hi, following that topic
I would like to calibrate 8 of those amplifiers
The speakers I'm using are those 8r 30w

The power I'm feeding the amps is 24V

How can I calibrate those amplifiers?
What output I should aim for?
I have an audio interface so I can output as in wave to the amplifier input and calibrate the output using a digital multimeter

Thanks for any advise

Mega Sale of European Rectifiers 2023

RGN1054 mesh £35
AZ1 mesh £35
AZ1 £5
AZ11 £5
AZ12 £10

Over 40 tubes total, most used, all tested good.

Shipping at cost. Offers for multiple items considered. Located in Kensington, London

I want to make a two way bookshelf cut at 3.5K 18db running at 8 ohms with those speakers. How can I make the 5 ohms tweeter run at 8 ohms? Is simply using a resistor troublesome? How can I calculate the loss of sensitivity to know if I would need an l pad aswell?

I want to know some models and manufacturers of loudspeakers, where this driver is in use. I choice the 5M driver in several diy satellite loudspeaker projects several years ago in small sizes (together with Focal TC90K or TC120K). Amazing to me is, that this driver provides excellent audible results in the "full-range" mode after performing a equalizer network for the midrange. After looking of the frequency response this isn't to expect.

This driver was temporarily no longer available. Now Fane (actually Precision Devices) has re-introduce the Studio 5M.

And for the Studio 5FR there is now a kevlar successor available, the Studio 5FRK - go to
https://www.fane-international.com/view-product/STUDIO-5FRK#tab-1a
and fourth pdf attachment.

The only commercial (in the meantime vintage) monitor was the "E1" from d&b Audiotechnik - go to
the third attachment.

Who knows, in which additional commercial loudspeaker products like studio monitors and small near field monitirs the 5M and the 5FR was in use - best thanks for your advices.

Mega Sale of European Radio Triodes 2023

Euro triodes B5 base
HLA2 £10
MH4 £12
K1694 £20 new
REN904 £35
A4110 £10
E428 £10
HL4 £10
NR52 £10
354V £10
AG495 £10

Euro triodes B7 base
DDT £5
MHD4 £5
TDD4 £5 Many Mullard, some boxed
4D1 £5
HL13 £5

Euro triodes side contact
AC2 £5
CC2 £5
ABC1 £5

Euro triodes octal base
EBC33 £5

Euro triodes Mazda 8
HL41 £5
HL41DD £5
HL23 £5

Over 130 tubes total, several new/boxed, most used, all tested good.

Shipping at cost. Offers for multiple items considered. Located in Kensington, London.

Audio amplifier device review: Fosi Audio ZA3

This is the second review I have written relating to a product from the FOSI brand, the first was relating to the Fosi K5 Pro Dac Gaming Audio, you can find it here:

https://community.fosiaudio.com/threads/fosi-audio-k5-pro-gaming-dac-review.11

while this refers to the FOSI ZA3 audio amplifier, with integrated TPA3255 high-end Class-D amp. which can be used in mono mode paired with another, or in classic stereo mode.
The product comes in a black and completely metallic case, with a veryminimal control panel, which includes:

• Volume knob with integrated pressure ON/OFF system.
• On the left a toggle switch for input selection between XLR and RCA.
• On the right, a toggle switch that selects Mono/Stereo operation.

There is no IR receiver for remote control, so everything is managed locally like the 'PURE' amplifiers, without too many frills.

The equipment includes :

• Amplifier.
• 48 VDC 5 A or 32 VDC 5 A power supply.
• The manual.

The amplifier features on the back :

• 2 Balanced XLR inputs
• 2 speaker outputs for cable / connector 2-8 Ohm
• 1 exit for SUB
• 2 classic RCA inputs
• 1 Jack 12 V trigger input (for remote ON)
• 1 input for 32 VDC / 48 VDC power jack

The specifications are as follows:

Channel: 2.0Amplifier
Chip: Texas Instruments TPA3255
SINAD: 89dBSNR: ≥106dB
Dynamic Range: ≥106dB
THD: <0.006%
Speaker Impedance Compatibility: 2-8Ω
Rated Power Output:
With 48V/5A PSU
Stereo: 180Wx2 @4Ω
Mono: 235Wx1 @4Ω
With 32V/5A PSU
Stereo: 95Wx2 @4Ω
Mono: 110Wx1 @4Ω
Frequency Response: 20Hz – 20KHz(±0.1dB)
Input Voltage Range: DC 24-48V

The power supply in my case is 48 VDC 5A, with considerable dimensions.




My first listening test was as seen in the photo below, conceived by connecting the XLR inputs present in the ZA3 to a Fiio K5 docking station, which also offers 2 3.5 mm jacks as balanced output on R and L.
The source associated with the docking is a Fiio X3 2nd generation, one of the first portable Fiio players with that form factor (I also own the X1) which it closely resembles.)




Let's not forget the speakers connected to these 2 jewels, 2 Indiana Line Tesi 560.
They seem to have been created for each other, connected and off you go, no background hiss and a lot of beautiful sound. I'll start by saying that this is the first time I've used balanced cables with XLR connectors and from the little I know they are used for connecting microphones and audio systems with mixer, immune to disturbances due to large cable distances.
Contained in the Fiio there are many songs in FLAC format, therefore with great definition in detail, and when listening with this ZA3 amp I was able to appreciate the spatiality of the reproduced sound expressed as separation between audio channels at the moment of generation but reunited once reached my ears. This is honestly the first thing I appreciated, the second is that my 11 year old son, climbing the stairs while I was listening, exclaimed 'GREAT SOUND', all his father...


My second listening test was, as can be seen from the photo below, conceived by connecting the RCA inputs of the ZA3 to a decidedly more recent portable player in my possession, namely a HIBY R5 Gen2, taking advantage of the headphone output connected to the specific cable.

For this test I moved to a desktop context, i.e. on my desk where I plan to keep my FOSI ZA3 connected to the PC through a Cambridge Magic 100 DAC, and in this case the speakers were downsized to the smaller Indiana Line Note 250 X.
'Nothing else matters' by Metallica is the first song in FLAC format taken from the Sinology Server where I keep the liquid music, which I play with the listening system, and I must say that apart from the slight lack of deep bass due to the not generous Woofers of the speakers, the spatiality remains precise and defined even at high volumes.
Then switching my HIBY to class A mode, warm nuances are added to the spatiality I was talking about before.
'Unfinished sympathy' in the orchestral version of Hooverphonic live at koningin elisabethzaal 2012, adds the theatricality of large live environments and the singer's incredible voice seems to come to life on my desk.
I now want to propose the various disassembly phases of the ZA3, useful for upgrading the two operational amplifiers that FOSI indicates can be replaced with other types of op-amps with characteristics of truly demanding audiophiles.

• With a light lever (with the help of a plastic tool) I extracted the volume knob which is only stuck by interference in the plastic body inserted into the aluminum knob.

• With this 10 mm insert applicable to a screwdriver, I unscrewed the nut and removed the washer to allow the detachment of the front panel. Needle-nosed pliers are also fine.

• I proceeded by unscrewing the two screws on the rear panel.

• Now with the same wrench I removed the two screws from the lower part of the ZA3.

• This is the result of the disassembled components.

• It is therefore possible by sliding them, extract the front panel with the two fixing rods, and then the sound card containing the amplification components.

By KonusAg

Good morning,
I bought this CD player to repair it, and I will briefly tell you its story, as I rebuilt it.
The CD was working fine until it stopped reading. The previous owner bought a new pickup, installed it, but he did not realize that he doesn't remove the "jumper" soldered to protect the optical pickup from electrostatic discharges. Not seeing a positive results, the previous owner, he mistakenly thought it could be cold welds or cracked by time. Here he made a total disaster .... he took the soldering iron and went over all the pins of the microcontrollers without using flux or anything else. End result: he reassembled everything without realizing he had short circuits and turned on the player, blew a fuse and threw in the towel. : evil:: evil:: evil:

So when the Denon arrived to me, nothing worked. Time to make a long diagnosis to notice the short-circuited pins, I took the flux, the magnifying glass, and with a lot of patience I restored all the soldering on the pins of the 2 microcontrollers. The work was very decisive in fact the cd player finally turned on again 🙂. Then I removed the tin jumper on the optical pickup, but to my sad surprise the player still can't read CDs.

When i turned on, the word DISC appears for a few seconds, and then disappears, and all the mechanics do not respond (the drawer does not open / close, the disc does not turn even if loaded by hand, and the pickup does not even try to find the CD). If, on the other hand, I put the USB mode on the front panel, I turn it off and on again, the drawer opens and closes with the button, but the reader continues to not read anything, the disk does not spin anyway and the USB detects them but does not read it. .. nothing more.

If I enter, with a combination of keys, in the diagnostic mode of the reader and launch any test, the display gives me the following error: E4-05. The service_manual shows E4-05: "Decoder bus error (Error in communications with CD decoder)"

Now I don't know how to proceed anymore. I did a check of all the components with the multimeter (diodes, smd capacitors, resistors etc ...) and everything is ok. I have also checked the main voltages and they are in line with the datasheet.
What do you suggest ??

I enclose service manual:
https://www.vintageshifi.com/repert...ge.php?pdf=Denon-DCD-710AE-Service-Manual.pdf

I have a bit of a long-winded question here so please bear with me...

I few years ago I decided to do a home theater room/audiophile listening room. I've barely watched movies in here. I've spent countless hours listening to music, though. I setup it up originally with Klipschorns as the mains, Heresy as the center, Klipsch Chorus I's as the side surrounds and Cornwall 1's as the rear surrounds. A single REL HT/1508 subwoofer. It was very dynamic and loud.

My equipment was and still is: JBL SDP-55 Home Theater processor, Jeff Rowland Continuum 500 along with 4 Jeff Rowland monoblock amps for all the surround channels. I used an Emotiva for center channel and Atmos ceiling speakers. This is when I discovered listening to music in multichannel stereo. I would turn off the Emotiva amp and play just 6 channels. I thoroughly enjoyed this for a lot of different music. It was quite immersive.

I rebuilt and restored a Thorens TD125 MKII turntable and matched it with a GoldNote Phono preamp with separate power supply. I thoroughly enjoy this as well. The turntable setup is strickly 2 channel stereo.

So, I got the bug and decided I wanted to change out all my speakers. I think commenced to selling off all my speakers and chose to build the Troels Gravesen's The Loudspeaker 1's for my front mains. I have communicated with Troels for what he would recommend for surrounds and didn't really get a good response. He pointed me to some other speakers in his catalog. They won't be timber matched. For movies, this isn't a huge deal, but for multichannel stereo music it would be a very big deal.
I have been dragging my feet in getting the TL1's completed. I've acquired all the drivers, crossover components and the Hypex amps for the bottom end, semi-active. When I was purchasing drivers, I went ahead and bought another pair of the 18 Sound mids and 18 Sound compression drivers with horns. These are all the same drivers Troels spec'ed for the TL1's.

Would it be possible to use the 18 Sound mids and 18 Sound compression drivers w/horns to make a 2 way setup for my side and rear surrounds? A 2 way reflex setup. In otherwords, a ported cabinet tuned to 18 Sound spec's for the mid driver?
The mid driver is 10NMBA520 midrange driver model. Would this matchup well with my whole setup and the REL sub taking up the slack on the bottom end for the surrounds?

This has really been eating at me for quite a while now. Hopefully there will be plenty here with some insight.

And YES! I'm INSANE!!!

Last year, I bought a 1960 Harman Kardon Citation II for a winter project. I keep a bunch of pictures of my progress here: https://photos.app.goo.gl/LSk2ugZ4eXJEJcaP9
Basically, I gutted out the box, re-using the choke, power and output xfmrs and most of the stuff on the back panel like those dual pots that I couldn't find anywhere and the bias meter and switch, and speaker terminals. From there, I used the original assembly manual for assembly. The power tubes are 6550.

After it was assembled it passed the resistance test and double checked every device and connection.

After presetting all the pots (balance to middle and the 4 Bias pots full clockwise), I inserted all 10 tubes and measured the 15 ohm resistor (voltage drop from power tubes cathode pin 8 to ground with 4-5 volts (should have been 1.5 volts in order for the bias meter to be set correctly). of course, the bias meter was pegged and the tubes began to get really hot after just 1 minutes, so pulled the plug. It's enough to say that any adjustment in the pots would have made the bias current even higher, so I had to sit and scratch my head.

I read a post by SY who says: Pull the output tubes. Turn the amp on. CAREFULLY check the voltage at the plates and screens of the KT88. It should be the full B+. Now, run the bias pot to one end and check the grid voltage. Run it to the other end and check the gid voltage. You should see something like -60V at one extreme and -25 at the other. If the voltage doesn't vary or you get wildly different numbers, you've found the fault.

I dont know if SY is right, but the voltage test in the back of the assembly manual says there should be -50 volts at the screens (tube terminal 5)

I I pulled the output tubes and while my B+ is 500 vdc (400vdc with power tubes inserted), with all bias pots turned fully clockwise I am reading -23v at the screens (tube terminal 5) and when I rotate the bias pot all the way to the other end, voltage goes to zero (same on other 3 tubes). This appears to be a problem I need help with. Some say I should increase the cathode bias resistor to reduce the cathode current, so I doubled it and all that happened was my voltage drop across that resistor doubled. Adding that resistance didn't change the cathode current at all and forces the bias meter with twice its rated current and that's not good. I put it back the way the book says and continued scratching my head. Another poster said to increase the resistor to tube terminal 5 to reduce the current, but that ended up increasing the cathode current (which did not make sense to me).

I'm hoping there is someone out there who knows the secret handshake and puts me back on track before I completely destroy this thing.

Thanks,
Walt

No longer looking as I have just purchased what I need, but cant figure out how to delete this post. maybe admin can delete it for me. thank you.

I would like to pass a spdif cable through a hole in a wall, to connect a home theater and a computer in different rooms. The hole already exists and I wouldn't like to enlarge it, but the problem is the optic cable terminals won't fit through it. I have a limited budget and wouldn't like to spend on extra tools to crimp the cable (I don't even know if that would be possible). Is there a type of optical cable with removable terminals? I wasn't able to find anything like that on my local stores. Any suggestions would be appreciated, thanks.

Morning, I have a NAD T743, using PSB bookshelves and Sony Active sub-woofer. I want a 2.1 sound to hear that bass what to do? Please help.

Hi,

Revisiting this design and I know there is still some interest in its capabilities. I was lucky enough to be given, some decades ago, the Babani loudspeaker cabinet book, first published in 1957. Full of treasures!!

Hidden away is the karlson K15 cabinet plan.

Obviously designed before software and intrigued as to the driver it was matched to, I worked on the principle that the recommendation may be for something like an Altec 604 or similar. The Heritage site has measured the TM parameters of these drivers, and in accordance with a lot of "horn designs", the Qts for instance is a low .25ish and free air resonance around 30Hz ish!

I imagine in today's terms it could be looked at as a bandpass design with the rear cabinet ported to the front creating a BP6 alignment? Obviously we have a "distributive/multiple port?" acting on the front chamber.

I established the rear cabinet is effectively 5cuft. The port was originally 4.5 ins in width and later changed to 3.5ins. Simulating this, assuming a correction factor (K) of around .7, the tuning frequency worked out to around 60-65 Hz.

Plotting bass responses with a variety of 15" drivers in a reflex box, the high tuning frequency inevitably created a peak in the response and an impedance curve with two very different peaks.

So my question, am I missing something, is it just mis-tuned or is this a requirement to account for loading the rear chamber into the front chamber?

Anybody! Thanks for any inputs and observations!

Hey!
I have just successfully finished repairing the Midrange of a SF Cremona (series 1). I purchased it from Scan Speak (not SF) and it works perfectly well.
This makes me wonder ... Has anybody tried to upgrade the Tweeter with the Scan Speak latest generation tweeters, without changing the cross-overs? The customized SF faceplate (with its cutout) can be substituted (I imagine) and the holes geometry/dimensions seem almost identical.
Any experience out there/here?

Thanks in a advance!

Hi, back here after a couple years. My buddy and I came up with a build which we feel is pretty good. We're trying to make a quality boombox that is really a general purpose computer and can run "Personal Voice Assistant" software. Think Alexa. We recently did a build, having acquired a shiny new Raspberry Pi 5, after 9 or more months and found we were rusty. I had been documenting the software side on github and decided to also describe the hardware side, so I can remember how to build these babies.

It would be nice to know what this community thinks - what's good about the build, and what can be improved? Here's the document, under the heading of "Free and Open Source Hardware" (FOSH):

https://github.com/mike99mac/minimy-mike99mac/tree/main/gcode

More pictures will be added after the next build, but this should be more that enough to get started with.

Thanks. -Mike Mac

P.S. If you're interested in the software documentation, it is just up one directory.

Hi, I'm Mike from NY. I was somewhat active some time back, but haven't been hanging out here. But I have been busy with audio. I'm trying to build a boombox that is really a general purpose computer and put some personal voice assistant code on it. Think Alexa. The devil is in the details on the software side. But you guys are interested in the hardware side, and I recently documented the entire build in annoying detail. What would be the right forum to discuss this and point people to the docs? Thanks.

I need help! I have an old STAX SR-gamma and I want to replace its old dirty head pad (not ear pad) to a new one. Is there anybody who can tell me how to remove the old one?

I need the service manual of the Jeff Rowland Model 2 or, at least, a schematic.
Can anyone help me? I will pay for postage and packing if sent by mail.
Thank you very much.
Stefano

Hi there, I've built a Circlotron amplifier with two very simple independent floating power supplies that each use CLC filtering. If I wanted to employ more sophisticated feedback regulation, could this be achieved by putting a 1:1 isolation transformer at the regulator outputs? Many thanks in advance!

I find myself contemplating the fate of this item on my workbench, and I'm curious to hear your insights. Would you recommend scrapping it, or perhaps responsibly disposing of it at the nearest recycling center? Your thoughts are much appreciated!

Good day,

Some months ago, I finished an OTL based on 17KV6 valves, which puts out 10W into 72R. It is based on Futtermann, +-150V Power supply and auto bias with 220R and circa 90mA idle per valve. https://www.diyaudio.com/community/threads/beam-power-pentode-otl.391888/

I also have a stash of 22JF6 which I want to use for a more powerful AB OTL amp to drive a 50R load (9x ~6R woofers in series). I want more power and less heat in the amplifier, so this time I decided to use fixed bias on the output tubes, but hat do double on the number of output valves, to get close to 50W into 50R.

For 50W into 50R, I need 1A Rms, or 1.4A peak, which is 0.7A per valve. Furthermore, developing 50W over 50R requires 50VRMS at the output, or 140Vpp, or 70Vpeak from each valve. Using +-155V power supply (and circa 150V at G2), it means that each valve operates between 150V and ~90mA at idle, and 80V and 700mA at peak. The blue trace connects there two points, looks doable (and with that I mean the worst case for the valve, where the G1 is at 0V (same potential as cathode, so limit of class 1) and 150V at G2, the plate is able to go down to 80V and pass 700mA).

I built the amp, much like its smaller brother. I use a 500VA transformer with 2x 115V secondaries, that go into a diode bridge and CRCRC (1200uF per C, 3R per resistor) for the positive and negative rail. Output is about +-160VDC.

For the fixed bias I, for the moment, made three separate power supplies, A, B and C. I have a single transformer with 3x 27V AC secondaries, each fed into a bridge and filtered with 2x470uF, 20k and 390k bleeder. Close to the valve and the 130k grid leak I have 50uF local decoupling. These three supplies are completely independent from each other. Supply A is connected to the upper cathode of the 1st channel, Supply B is connected to B-, and provides bias for both channels, supply C is connected to the upper cathode of the 2nd channel. I feed the primary of this transformer with a VARIAC, to allow bias adjustment.

I built the amp (both channels) and let it run at idle, with al bias values at around -29V (in relation to the respective cathode). I apply 1kHz sinewave to the 1st channel and it starts clipping at circa 12W (measured 25V RMS into 50R). That means that each valve is only accomplishing 0.35A peak…

I measure around and finally put my DVMs across the bias supply A-A1, B-B1, and C-C1. All bias values where at -29V at idle, but when I start increasing the level, the value of bias A-A1 starts going up, at the 12W it is at -35V. The value at B-B1 goes to about -30V, the value at C-C1 (which has no signal applied, so still idle) stays at -29V. Why does that happen?

(20k and 390k filtering on the bias is a bit on the high side, I could well use 1k and 20k bleeder, current consumption of the bias would still be below 2mA.)

Looking at the scope it is clear that the top of the sine is clipped, implying that the top tube can’t pass more current, which is understandable at it is biased at -35V, while the lower is at -30V, with both getting the same signal from the concertina?

The driver (using a E180F) is fed from a separate 300V DC supply, the heaters are all fed from AC. At idle and up to 10W the amp is working very fine (I already got rid of oscillations, a different story…), only when requesting more power, it is somehow, I think, current constrained and altering the bias supply value.

I also thought about the resistance in series with G2 causing too high a drop, limiting voltage at G2, which is essential to pass more current – I will still measure that!

Originally, I had 10R resistors in each cathode to help equalize current over both valves. With peaks of 0.7A, these would develop 7V local feedback, so I (temporarily) bypassed them, but did not make a difference for the output power.

Many thanks for all of your comments and ideas!

How much do rectifier tubes influence the sound of your amplifier? I have Mono blocs that I enjoy, but though the designated writings says 5u4GB by Sylvania they are different size, but similar shape.

When I saw Papa's new SIT muffs on the street I couldn't resist and had to give one whose features I had not seen before a thorough workout. After stimulating that special muff (oops, I meant simulating, but you knew that), I recommend that you give it a try too.

Papa's SIT/NFET mu follower follower is shown in the last schematic of the Nelson Pass paper “BAF 2022 SIT Power Amplifiers” https://www.diyaudio.com/community/attachments/baf-2022-sit-amplifiers-pdf.1101782/, shown in the first image below. The paper shows circuit parameters and performance results for the PFET muff. When I simulate the NFET version of the muff using the same parameters I get the essentially the same results. The second image shows the circuit, power spectra, and waveforms at 1W, 5W, 25W and 45W into an 8R load. The power spectrum has a nice rolloff characteristic. The idle power dissipation is 60V*3A=180W per channel.

In this thread I will show simulation results using variety of parameter combinations using the circuit shown in the second image.

Friend of mine asked me about making a 1960s/1970s type of speaker. Big baffle. I need some advice on the woofer. I'm pretty sure the midrange I'll be using is 92.5dB/2.83v, so I'm looking for a highish efficiency woofer. I'd like 8", but not sure those will go deep enough, so I'm considering larger. These may cross around 400hz to the mid. Currently considering Beyma 8P300Fe/N, BMS 10RS300, Eminence 10" Kappa Pro LF, Eminence 12" Kappalite 3012LF, and Eminence Deltalite 2512 II. Any other drivers and considerations I should consider?

I bought this unit for parts and was able to traced out an issue with a voltage regulator that got it playing music again. However, the screen is very faded. I did the simple item of checking the solder connections for the display. But I think it is backlit by a bulb and that bulb has gone bad. Below are some photos.



You can see the bulb I am referring to in the second image. I am not sure how to deal with that. It looks like it is self contained and I don't want to destroy the display trying to get better lighting, but I would like to fix it if its possible. The other though I had was to jerry-rig an led next to it to pass light in, though that seems like a bastardization in this unit.

Anyways, I've attached a service manual for the unit if anyone has any thought of repairs or things to check.

Best regards!

Hello everyone. On this past New Year's Day, I pulled the trigger on a really clean, good looking Altec Lansing 710a stereo receiver on Ebay. The unit is most certainly clean, especially being of 1973 vintage. The unit works, it's just that it can't fully amplify 2 book-shelf Klipsch speakers. No matter how I hook it from the back, sound comes out of both speakers, but it's always one that is isn't quite right. So transistor, capacitor etc. problem? Whatever. I tried buying a reproduced service manual of this exact receiver off the website where the guy did everything old school and from home. I'm forgetting his name and business, but I found out earlier last week he had sadly passed away. His website and sheer dedication was very endearing! Just like many others not being able to set an account on "Hifiengine', in this thread, can anyone get me the service manual for this Altec 710a stereo receiver? It would be very appreciated. This is a very nifty discussion forum, many knowledgeable people abound!!

https://www.canuckaudiomart.com/det...-amp-camp-amps-class-a-stereo-or-mono-blocks/

Not mine, no connection.