SOLD
New never used.

Please send me PM to discuss price and postage.

** SOLD ** One pair slightly used (no real signs though).

See specs on web. Price new is £168.48 for one.

Please send me PM to discuss price and postage.

Hi everyone,

I have a Studer A721 that was given to me very recently and has come from a studio/radio station and it has not been in use for a number of years I imagine.

I have no experience of this deck and would like some advice on what could be the issue and where to start looking. All I can see so far is that upon applying power the relay clicks, the EOT red light is on and the capstans turn. Display does not illuminate so I cannot tell if the display is showing anything however none of the buttons are responsive.

Pressing the micro switches that are sitting right behind the cassette shell shows slow motion of the reel motors. This is all I can get out of the deck so far.
None of the 3 secondary fuses are blown, it still has all the original caps and the only measurements I took where the +/- voltages of around 22v from the 2 voltage stabilisers LM317/LM337. They measured about 5 volts higher than they should however.

I have not yet checked if I have a 5v supply as I stopped there and decided to ask for help here and hopefully what I describe above might ring a bell of common issues.

Any help would be greatly appreciated please so I get this wonderful deck going again.

Cheers 🥂

Sorry for out of topic...

I changed the output caps and rail bypass caps on my Marantz SA11S1 and now it sounds very neautral and very smooth at high frequencies. My scope shows that the rails are very clean for high frequencies, BUT, I found 120Hz ripples at around 3mv p-p. I don't think the Marantz HDAM modules have any PSSR so no wonder the player does not sound as smooth or details as other high end CD players at lower frequencies!

Unfortunately I can't fit a CCS-shunt reg there because the heat within the chassis will quickly build up.

Which is the best series regulator circuit available? I have tried the Jung Supereg but at the time I did not have sufficient build experience to build it right, I guess. But then somebody reported that the phase margin is really low with that one. Any recommendations? my requirement is that the input is about +/-15V? output is about +/-11V.

Thanks in advance.
Regards,
Bill

Per title. Will be reviewed.

Who would have thought I would be selling my favorite DAC...?? Well, I have bought the Holo May DAC and thus, do not require this DAC anymore. So it is yours to grab!

Preamplifier, DAC and Music Server all in one chassis

Preamplifier section is Mirand Preamplifier ver.1.1 with Oled display.

• 5 inputs (one use internally balanced for the Mirand DAC AK4490), 2x XLR and 2x RCA
• 2 outputs (1x RCA, 1x XLR)
• Oled display with programmable inputs (input name, volume), DAC functions
• Compatible with Apple remote (not included)

Mirand DAC AK4490

• Included with 3 different output shields (Opamps, discrete and Mirand discrete Opamps)
• PCM 384, DoP and DSD256 compatible

Both DAC and Preamp are powered by AMB Sigma 22 and Sigma 11

Allo USBridge-Sig with external MicroSD slot (I can install your distro of choice if needed)
Allo USBridge-Sig is powered by external Allo Shanti

Will let it go for SOLD$USD plus shipping + 3% Paypal. Not responsible for any import fees, customs, taxes, etc...







All the best!
Do

Due to delays in non-audio projects, I am, as they say, back on my BS.

I am putting together a PCB for a set of LR4 crossovers with a view to assembling a 2.1 computer-speaker set, with the fronts being two-way actively crossed over. Or you could think of it as a 3-way system with the LF channels mixed and run through a Linkwitz Transform.

If anyone with a clue has a few spare minutes, I would appreciate any input on the design as it progresses - it is on github. The files are for KiCad, but there's a PDF of the schematic which should be readable by anyone. I haven't started on layout for this board yet.

I will be getting a batch of blank boards made up in China and populating them by hand; reflow solder on a hotplate. Assuming they work, I may put the leftovers blank boards up for sale.

Some design assumptions, which people may or may not agree with:

• gain control trimpots for each output
• most components are SMD for reasons of space, mostly 0805 because that's what I standardised on and have reels full of
• precision thin-film resistors where required in filters
• filter caps are SMD poly, so mostly 1206-1210
• C1/C3/R1/R3 in the Linkwitz Transform have multi-footprints to support creation of exact values
• supply bypass caps are X7R (small, cheap and good enough!)
• Linkwitz Transform caps are up around 1uF therefore through-hole
• opamps I hope to be DIP-socketed but will change to SOIC if I need the space
• aiming for max 100x100mm board to fit in the cheap proto PCB services

Observant reviewers will immediately spot the, uh, inspiration drawn from Rod Elliot's (ESP) projects, for which I am extremely grateful.

I know we all love to hate on X7R caps in filters because of distortion and low effective capacitance when biased, but the classic rumble filter on a subwoofer has a bipolar electrolytic in series. Surely that has got to be worse than a big X7R being operated with approximately zero bias? Has anyone tested the difference? Or should I just make room for a 15mm KEMET film box-thing?

Hello,
I just picked up these two items, but cannot find
much information about them. Ideally, I would like
some basic operating instructions, and original
specifications. A couple particular questions -
there are two main outputs,is one pair inverting?
In order for me to get the preamp to work with a
stereo amp I must use the right output from one
set, and the left output from the OTHER set, why?
There are two phono inputs - do they both offer the
same amount of gain, or is one dedicated to MC use
with the M1 unit? The quality of components, and
construction appear to be of very high quality. Are
there any details on the design topology, and components
avaliable? Would this be a good preamp to check over,
and replace any out of spec. items, or should I spend
money on a more current design (coda maybe)?
Finally, this preamp dates from 1977, how long was it
in production, and were very many of them produced?
Lots of questions, I know, but I believe this is a
Nelson Pass designed product, so I hope I came to the
right place!! 🙂 Any help would be great,
Steve

UPDATE ** problem solved, read through to my post on pg 3 **

For the people following my Citation repair which has turned into a refurb and slight modification, this looks like the final chapter.

I've previously replaced all the passives - electrolytics are now Nichicon KZ/FG, the polys are now all Wima MKP, and the resistors are Dale metal film 1% tolerance. I've also put new mica insulators and Wakefield thermal paste in. Everything I've done has reduced noise so far, but there was one buzz that has remained consistent in the left channel. I've reached the final stage, where I tracked down the source of the buzz.

It was when I was redoing the thermal coupling that I discovered the left channel outputs were no longer the original Harman Kardon 43024216 (RCA 40636), they'd been replaced with Sony TO-3 devices, TX 183S, and they are noisy. I moved them to the right channel to make sure there wasn't anything failing in the left channel voltage gain section, and the noise followed them. I was able to get it to abate somewhat by splitting the devices across the channels, so each channel had one original and one Sony, and while that worked it also increased the distortion in both channels.

Now i have to either find NOS outputs, or some vintage pulls, or more preferably some modern equivalents. I can read parts sheets but there still will be effort spent on trial and error until I get parts that play well with the rest of the circuit and sound great.

If you know of any TO-3 devices that will replace the RCA 40636 NPN in the Citation 12 amp please let me know.

I have the following :

Ian Canada Transformer I/V PCB mini KIT with lundahl ll1544a installed and i/v resistors.

180 GBP plus shipping to worldwide (free shipping within UK)

Anyone know anything about this amp? Mine seems to have a power supply out. The unit wont come on at all. But I cant seem to find parts for it.

How good is Hornresp?



So first off- I am aware that this software is free. So even if it's just a bit of fun I am definitely not complaining.

Also, I'm aware that this has probably been discussed a lot before, but cannot find any dedicated thread, other than David's pinned thread. If there is such a thread, please point me in the direction and I will duly delete this thread.


I'm working on tapped horns. My current attitude to using it is based on hoping that it 'probably gives a good general indication' of how a real built horn will sound. And I'm expecting to make at least a couple of mocks in MDF before making my final 'product'.

Is this a reasonable approach?

Are there any known ways in which the software (as excellent as I presume it is) cannot be expected to predict reality?

int'd to buy in Canada (unless post from US is reasonable)
Pair req'd
hole I need to fit is 5.5 inch dia. in floorstander box
An ideal is SEAS CA18RLY driver

not dedicated woof, it's for a 2-way
thanks NO LONGER NEEDED

Hello all,

I have had luck before here, at DiyAudio, with tools and equipment.
As many here I shop for used equipment in eBay with varied levels of success. I bought long time ago (2018) a Keithley 197A that is in great cosmetic and functional condition. It is a great meter for the price, when you can get a deal, and is very precise. I got it for less than $100 shipping included.

As most meters of this era, and particularly with these, the EL does not work. It has a power button in the back that enables this function. Using an EL driver from an old Sencore VCR test unit, to validate that the EL element is functional, and it's the driver that has the problem. I contacted Keithley, now Tektronix, and they mentioned the driver is not available. Efforts to open it up to repair were unsuccessful, as it's imbedded in some resin and difficult to troubleshoot.

Interesting enough, the Sencore has a discrete circuit with one transformer and one transistor and appears to operate also from a 5VDC supply. I am surprised no devices are available to replace this module for cheap and already to go. It is true most new equipment with LCD displays now use LED back lighting, but I was hoping for ideas or if someone has solved this problem to point me in the correct direction. A nice backlight would help the viewing of the Keithley's LCD display better

Any ideas are welcomed.

Long shot, but anyone got a silentswitcher they'd be prepared to sell on? Postage/duty/fees buying new from the diya store will be prohibitive to UK I think.

Hello Everyone,

I just completed my dual mono amp using JLE Sylph-D400M TPA3255 boards, Connex Electronic SMPS600RS running at 50v, and a BTSB to convert from single ended into balanced as well as a bit of extra gain if necessary. Apologies in advance for any poor terminology, as well as the fairly messy interior, I'm still learning.

For the most part things seem to be working, however I am struggling with resolving an odd hum / noise issue that I can't pinpoint.

When the amp is on a test bench, cover off, and nothing connected to the input, there is a very faint hum if you press your ear to the speaker. When moving your finger or object near the input wire the hum increases in volume. Moving the amp over to my stand where it will live long term, I have the very faint hum, that seems to increase slightly in noise when an audio signal passes into the amp, as well as the input seems to be picking up something that I can only describe as a periodic rustling or crackling of sorts, something you only notice when close to the speaker but a problem no less.

I've removed the RCA jacks from the chassis and left them free floating with no changes to behavior. Removing the cable shield from the main ground loop breaker seems to increase volume of the hum sound.

I feel as if I have a ground loop or I am missing something else completely in my wiring and I am at my wits end trying to pinpoint it. I've attached a picture of the amp, but I am happy to take more pictures and draw functional diagrams as needed.

I would be so very appreciative if someone could help me resolve this, I know the JLE boards and the BTSB are capable of being silent and I am fairly certain I am just doing something incorrectly.

Possibly enable a toggle, as some people have said they like this, and some do not.

I'm looking for Mini DSP Nano DIGI 2x8
This product is now out of sale from MiniDSP, and can't find anywhere else
Thanks for offers , even without PSU and box !

I'm just dipping my toe into the world of diy vacuum tube equipment, so I'm not yet sure what questions I should be asking. But, intrinsically it appeals to me to build a zero feedback single-ended tube preamp or line stage. What I don't know is the complexity or challenges of such a project. I'm seeking direction more than anything. If it's not possible, or if it's much more realistic to build a low-feedback design, etc.

Hi. For sale a complete parts kits to build the original Aikido octal tube preamp, Rev. A PCB. This is an original kit, with still unopened labelled part bags.
There was some missing resistors, and I included excellent Vishay RN60D resistors.

It is one of the best tube preamp out there, well regarded design and good sounding.

The kit includes the original PCB with documentation, all the discrete parts (except input selector, and volume pot), original kit matched tubes (Rogers NOS 6SN7), their sockets, and even the needed power transformers (Triad Split core, my favorite).
In these days of parts shortage, this kit is this easiest way to build the Aikido. Included replacement to the original coupling caps huge Russian NOS caps (large green cans). You'll also get my detailled BOM that goes with this kit.

I got this kit as payment for a work I did, but sadly I have too many projects, so this one has to go.

I`m asking only the cost of the original parts 250U$, buyer pay shipping and Paypal 3.5%fee
Keep in mind the rather large cost of similar 6SN7 NOS matched quad is also included in the price...

Already into the box, ready to ship...

Send me an email if interested.

Thanks for looking
SB

I just recapped a solid state phono preamp. Built in 1993, but new to me, it sounded fantastic before. However, I’ve seen what failed caps - both HV electrolytic filter caps and pressed paper couplers - can do to vintage gear. In my mind, the question regarding electrolytics in a power supply has always been not whether they will fail, but when. Clearly, I have nothing but disdain for the old “If it ain’t broke…” adage.

I replaced all 12 2200uF Panasonic M series, with 25V and 35V ratings, with Rubycon ZLH 2200uF/35V from DigiKey. With a 10000 hour lifespan and higher max temperature rating than the originals, as well as the added benefit(?) of lower ESR, they seemed a reasonable choice.

Aside from the recap itself, I disconnected both the hot and neutral lines at the IEC (with standard EMF filter) as well as the power LED leads at the separate preamp board to gain sufficient clearance to rotate the PSU board 90 degrees to get at the underside. Both were reconnected, but at the moment the LED is disconnected to rule out a short there (meter says there is not). Nothing else, including transformer leads, was disconnected.

After the soldering on the board was complete, I cleaned up both old and new flux residue with 91% isopropyl and a cotton swab. I’ve been unable to retrieve a few strands of cotton that were trapped by the cut leads.

The board itself is translucent white or “clear” Fiberglas with no solder mask.

Now, as soon as power is applied to the IEC (no power switch), the fuse immediately blows, leading me to believe there’s a short somewhere, but I can find no solder bridges, all the caps are aligned properly with respect to polarity, and all the cap leads have been trimmed.

I’m at a loss, and the only possibilities I can think of seem unlikely:

• the isopropyl damaged the board
• I damaged the IEC internal filter components with excess heat
• I damaged the new caps while soldering
• Low ESR is causing current to surge initially
• Bad karma/juju

I’ve been DIYing for over 20 years, so I like to think I know how to handle an iron, but I admit I’m still getting the hang of my new Hakko. I seem to need higher temps than I think I should to get solder to flow well, but I can recognize when an iron is too hot.

I’m hoping that I’m missing something obvious. Thoughts, anyone?

Hi.
I intend to make a Linear Power Supply of 5v 3 amps, using a 9 volt transformer. Since I dont want the chassis to be bulkier due to the transformer inside, I wish to keep the Transformer away in a seperate enclosure and then extend the secondaries for about two feet to a smaller board which will house the rectifier and the filter caps and the regulator. I wanted to know if it's better to keep the transformer alone at that distance or wire the rectifier closer to the transformer and then wire the 2 feet cable out of it (DC) to the smaller board to connect the rest of the circuit.

Thank you

2 For Sale - These drivers are mounted within an enclosure designed by BG. The driver element is mounted in an extruded aluminum housing with a PVC outer shell. The unit can be used as-is or remove the PVC ‘enclosure’ and mount the driver in-wall for home theatre application or remove the raw driver from the housing for your own design. The pic shows the notch filter that is recommended for these units. These drivers have had virtually no use and have remained in a canvass storage bag for years. They are heavy so I would prefer a pick up in Davis California (just west of Sacramento). Here’s some manufacturer info:

Bohlender Graebener RD50 Planar Transducer
The RD series of loudspeaker drivers offer the systems designer the advantages of a thin-film, line-source transducer with very high-performance potential for fixed installation sound reproduction. Unlike most exotic driver types, the RD series models feature unmatched bandwidth, power handling and ruggedness, as well as the ease of an almost entirely resistive load to the amplifier. The RD Series feature linear, push-pull Ceramic 8 motors linearly driving a polyester diaphragm whose moving mass is actually less than the air load. The bandwidth of the RD Series drivers is extraordinarily large, and is usable from as low as 150Hz to beyond audibility. Program power handling of the RD50 driver is 150 watts. The diaphragm is protected within a chassis made of three layers of heavy gauge, self-reinforced steel.
Specifications: • Power handling: 70 watts RMS/270 watts max • Nominal impedance: 4 ohms • Re: 4.0 ohms • Frequency range: 150-18,500 Hz • SPL: 88 dB 1W/1m • Net weight: 25.2 lbs. • Dimensions: 51-1/2" L x 4-11/16" W x 1-1/2" D.

$800 for the pair

DTQWTII by Troels Gravesen from Argentina

Hello everyone :

I have finally begun to build this great project Troels Gravesen. I read many favorable reviews for great sound the same, I hope not disappoint my expectations.

I mounted the tweeter waveguide, reinforced the crossovers and I had to make a mounting plate for binding post

I will continue to report progress as the construcccion.

Regards

45 Type Push/Pull
How many here use or have heard one of these type amps? What are the important factors here in this being able to produce quality sound of this tube with out the noise???
Can this amp achieve the sound quality of an SET amp?

I've been given a small grant by my College to design some high/mid frequency horns.

It's my understanding that the throat (acoustic) impedance of that the horn presents to the compression driver should be equal to the (acoustic) source iimpedance of the driver; the reactive part of the source impedance when the driver is oscillating into open air is reduced to near 0 by the gradual flaring of the horn, meaning more power is transfered as sound. If the throat impedance of the horn isn't properly matched to the source imepedance, it will increase the reactive part of the impedance as well. This throat impedance is in turn determined by the size of the mouth, the horn's shape, and the length.

If this understanding is correct, my question is:

How do I calculate or measure this source (acoustic) impedance of my compression drivers? There doesn't seem to be any charts on the spec sheets for ACOUSTIC impedance, and none of the texts I've read so far go into any detail about measuring the source impedance short of solving the full circuit (which I'm not confident doing, but may end up being the avenue I have to take.)

I feel like I may be misunderstanding the relationship between the source impedance and the throat impedance; perhaps the source impedance is determined by the throat impedance (or the throat impedance presented to the source is really the only one that matters), and therefore the horn only needs to be designed with a mouth impedance, length, and profile that yield the desired throat imepdance response. This would mean that the throat impedance would just have to be determined in such a way that it was purely resistive through the desired frequency range.

Am I understanding this correctly, or am I completely off point?

Hello fine people,

My DAC pile includes a later Schiit Modi 2, the one that's powered through the computer USB.

This model is not recognized by my PC (nice build desktop) unless it is physically warmed up on my space heater (alu enclosure approaching 40c).

What part of this DAC would not work at ambient temp around 25c? The problem seems to be with the USB interface in the Schiit, but I don't understand why being too cold would be a factor. Maybe there's an easy way to tinker and make this work.

I’m wondering if anyone is familiar with the EPOS ES22 and how it’s possible to gain access to the drivers? Other models had large bolts clamping the front and real baffles, however I’m not sure how the 22s are constructed.

Cheers,

Pete

An Analytical Approach to Linear Audio Frequency Power Amplifier Design: Selected Papers: Amazon.co.uk: Kiwanuka, Michael: 9781803691602: Books

Blurb from Amazon:

This book is essential reading principally for designers of linear audio frequency power amplifiers and more generally students and amateur enthusiasts of audio frequency electronics.

A first-principles analytical approach is here preferred because it engenders an intuitive appreciation of the workings of linear audio frequency power amplifiers, and it provides the engineer and researcher with a sound foundation for further work in the field.

Among other matters, the author cogently and succinctly

1. Evaluates the merits and demerits of two pole Miller minor negative feedback loop frequency compensation (TPMC) and localised two pole Miller minor negative feedback loop frequency compensation (LTPMC) and develops clear, systematic means by which these frequency compensation networks may be optimised.

2. Tenders two novel feedforward-compensated push-pull folded cascode transimpedance stage (TIS) designs in which slew asymmetry is banished.

3. Renders two novel feedforward-compensated push-pull transimpedance stage (TIS) designs based on the complementary emitter-coupled transistor pair of Sziklai et al.

4. Assesses the value of Burwen’s Inductive Frequency Compensation (IFC) in context.

5. Presents six idiosyncratic audio frequency power amplifier designs compensated with optimised LTPMC networks and incorporating non-invasive anti-saturation measures.

6. Examines monolithic/discrete composite linear audio frequency power amplifiers and their frequency compensation.

7. Describes how Safe Operating Area (SOA) protection networks may be correctly and accurately designed so that they remain inert when the amplifier does not require protection.

8. Gives an account of error feedback correction and presents three novel error feedback correction circuits.

9. Discusses output-stage-inclusive single pole Miller minor negative feedback loop frequency compensation (OSI-SPMC).

The author gives all credit to Almighty God, the fount of all knowledge and without whom nothing is possible, through His son, Jesus Christ.

Finally, the author hopes devoutly that adopters of this book will derive as much pleasure from reading it as he did from writing it.

Click to expand...

The author has kindly provided LTspice files of three of his designs with "robust compensation". These files contain all the required models embedded in the schematics, so they are ready to run without any extra effort:

Is any one familiar with nakamichi pa-7 soft start circuit?
Looking to buy this amp but the seller says pa-7 soft start circuit is blowing fuses but it's ok to by pass this circuit..amp sounds good with circuit bypassed



Would anyone elaborate on it? What could be the root cause

I used to always use ALPs pots in almost everything I built. Then a friend introduced me to Allen-Bradley MilSpec pots. As you an imagine, they are of incredibly sturdy construction and work very well. I have found a new and I think higher standard of pot.

Has anyone else had a similar experience?

On my quest to find a voltage stage for my 6a3 project I tested a 12ay7. And much to my surprise, it is very linear. Hopefully, the images attach, but at 84Vpp, the 2nd harmonics are almost 90dB below fundamental. Take the 3rds and 5ths with a grain of salt, I used my phone as the generator, and they poke out even on the baseline measurement. If I am not mistaken, Cmiller isn't crushing either at a little over 50pF. The tube tested was a Groove Tubes brand. Literally made for guitar amps. The test was performed with a hybrid mu follower, using the mu out into a 100k load. The operating point was 200Vak @1.3ma. The plan is to rc couple it to a source follower for powerdrive. Why aren't these little triodes used more?

I am looking for a remote volume control for my preamp which already has a remote volume control. Huh?

What I am looking for is rotary volume control that can control the volume control on my preamp which already is operated via IR. Ideally this would be a learning type. The reason I am looking for this is that I am tired of pressing buttons up and down and want to turn a knob. I am sure many face this same dilemna we would prefer to use a rotary knob.

I think the creative one would simply get a knob from a broken receiver and use an Arduino circuit and then build it from there. I am looking for a ready made solution.

My dream would come true if this remove would fit in my hand and made from metal. It needs to be solid with a decent metal knob or something that operates smoothly and feels good.

In the old days my Laserdisc player had a remote control with a jogging function.....yeah something like that.

Anyone have any ideas? Maybe someone can design and make one?

Luxman DML-01 Dual monolithic IC's as the title says. These were used in a number of Luxman amps such as the 5M21/5M20, 5L15, M12 & L10.

These IC's were problematic and as I found out you ended up with a nice doorstop when they failed and fail they would. I certainly wasn't the first but I found a work around and since then quite a number of wonderful Luxman amps have lived to create music another day.

Due to the number of inquiries I've had over the course of time I thought I'd come up with something that one without the technical ability or means could pretty much just drop in place. All you need to do is be able to de-solder/solder some pins, use a DMM and follow some simple instructions.

Pictured is my solution to the original IC. With a labour of love and that sense of diy pride I hand make each one. I don't think they are too bad either if I do say so myself 🙂

Some members have reported missing posts in the latest posts feed.

If you see this happening and can provide screenshot evidence, please add it here.

I am building my first tube amp, it's exciting and can seem daunting too. I am hoping not to make any costly mistake.

Transformers are Edcor XPWR035 and CXSE25-8-5K.

I intend to do a first build with tube rectification and affordable Sino tubes like 6L6.

I have salvaged caps. Would these do for C1 and C2?:

120uF 400V 105C
150uF 400V 85C

I am not sure about both the voltage rating for peak B+ and the temp rating as 85C seems low.

I just got a very collectable Philips CD650 CD player.
I opened it up and someone put a whole lot of what what seem like foam rubber disks on IC's capacitors and the board itself. I have looked at other pictures of this model and these disks are not there. I have never seen disks like this before.

My question is what purpose could they possibly serve (and what are they )????

Hi

Great new forum update.

Unfortunately it does not appear to work with Tapatalk , which makes using it on the phone much easier.

Tried logging out, and now there is a login error.

Anything that needs to be done on the back end for the forum to work in mobile apps like Tapatalk?

My old but loved Toshiba SD9500E wont switch on, power light comes on but wont switch on. Lots of the PSU caps were out of spec but nothing major. the problem seems to be a burned out transformer on the SMPS PSU Board.

But where in the world might I find a replacement transformer or a replacement board. Any one know of any possible sources for old boards.

I am in the UK but happy to source from abroad if needs be









many thanks for looking

Ian

He was only 68. Taxi Fare spinning right now...

RIP my friend.

I am planning to do couple of about 150 liter subs to my living room. This driver looks interesting. Any experience?

I recently purchased a DATS V3 to measure some drivers I have lying around and each free air measurement is wildly different than the other (for the same driver). I'm getting QTS swings of 0.6 or more and the frequency curves look completely different each time. Anyone have any advice on this? I appreciate it!

The iec socket on the F6 amplifier uses a fuse on both the line and neutral. Should the neutral pole have a larger amperage fuse?

Hello,
could some expert please confirm whether this is an original Altec 515B cone or an aftermarket one. Never seen such a cone on original Altec speakers, hence my question. Could maybe made by GPA?

Hi there! Has anyone tried modifying a HIP4080 amplifier circuit to use a different half bridge driver?

I always found that NEO 3 pdr is a nearly perfect tweeter excepted the frequency response.
When I studied the construction, I found that this tweeter sufering of difraction because of the magnets in front of the diaphragm.

So I've design some flexible resin shape to bond on the tweeter surface (on both side).

This shape cancel the diffraction effect of the tweeter housing

It's 3D printing with formlabs flexible resin:


It's far more effective than I though, nearly perfect response (green curve after modification, red before modification)



I will give up the waveguide! :green:

## Update: I ended up buying an STA-1000D ##


Hi there. Long time since I've been logged in.


I've been running an 4x IRS2092 amp that I built myself out of L15DSMD boards and a big SMPS. Been quite happy with it. But it's not the most detailed amp, and it's not particularly quiet.


Then I started researching again, a couple of weeks ago. I'm quite keen on the Icepower 125ASX2 modules. But there's a lot of questionable Icepower modules on Ebay and Ali. They seem pretty hard to source inside Europe, unless it's from Chinese sellers with EU stock.


That's when I ran into the IMG Stageline STA-1000D, that has Pascal modules. But from my understanding, these modules are as basic as Pascal Class D modules can be. But then I started looking at the other Stageline AMP's, and the 400D and 800D uses Hypex boards with Hypex SMPS's.


The 800D uses 2 UcD400OEM V7 modules and 2 Hypex SMPS400 V14 modules.


I reckon from reading in here, that these UcD400 boards should be quieter and sound better than my IRS2090(L15DSMD) amp. There is also balanced input, and my Stream Magic has balanced outputs, so there's that.
I can't seem to find any comparison of the UcD400 to 125ASX2 anywhere. But with these boards I should be pretty sure they are not fakes at least.
I like building amps, but with 2 kids and a pretty full schedule I won't lie. A ready box containing these modules would be a lot easier to play with and modify.


Or does the OEM boards sound horrific and I should move on?


I need to do more research. If anyone has some experience or remember some threads that I can't find - anything would be much appreciated.


Source of information: Opinion on IMG Stage line STA-400D amplifier with Hypex modules | Audio Science Review (ASR) Forum

and: Finale di potenza basato su Moduli Hypex dal suono hi-fi
Link to manufacturer: IMG STAGELINE: STA-800D



Pictures of the innards:

Hello fellow audio enthusiasts!

I have a scooter sound system project in the process and I have run into a few problems! I have searched high and low for solutions and I have gotten so so many different answers and opinions. Heres what I'm trying to do

3 weeks ago I bought an electric scooter (The Raptor) and I have desperately been trying to figure out how to power my small 23w Sub that I took out of a 2.1 with sub PC speakers (Logitech Z4's). My first attempt literally almost killed me. I laugh at my major stupidity now but in all seriousness I could have died or at the least been seriously injured.Long story short I watched a video online on how to turn a car battery into a battery back up with a 12v cigarette lighter adapter. I then went out and got a 200w power inverter. I plugged in the speakers as is (in the original box). At first it worked awesome. My first test of a 20 minute trip went smooth. However my 2nd trip of an hour went horribly bad! The battery caught on fire while I was driving and caught my back trunk compartment on fire. Lets just say my bike no longer has a trunk lol.

I have been doing some research on the SLA batteries that my bike uses but I'm told that I would only get at most and hour of play time out of a charge. Which is actually pretty good for me since I never really ride the bike for "hours" straight.

Anyways now that you have a bit of background to what I have been up to here is what I have done so far and where I'm at.

I decided to try and power the full range speakers (both are 17w a piece) with an amp from a pair of USB powered pc speakers. So far they work fantastic. I bought a USB battery back up @ 3.6v and 2800 mha to power it on my bike. I took out the sub speaker and amp from inside the sub box.

Here is where I need help. I was hoping to be able to use the chips and diodes etc on the board I have and remake a new amp board specifically just to power the 23w sub. I have a better then average skills with a solder iron and I can follow direction with great precision but when it comes to knowing the details of what each chip and diode does is beyond me. I have no clue in where to begin to make a new amp board.

If someone could take a look at what I have (Pictures at bottom) and possibly help me find the proper instructions on how to build the amp and maybe any extra parts/materials I will need, so that it wont take a ton of power to run I would be so ever grateful!

FULL AMP BOARD VIEW:




SUBWOOFER SERIAL NUMBER:


AMP BOARD ID:


STA540 Amp Chip:


JRC 45650 Amp Chip:


TL074CN Amp Chip:


DIODES ETC..










Any help is greatly greatly appreciated! Thanks so much!

I have the components for Tony Gee"s Mezzo Galactica I built a variation of 6 years ago. I have cabinets also if you happen to live in Arizona. Although they are not like Tony's. I used the same Seas Excel T29CF001-E0038, the same PHL 1130 but, because of availability, I had to use Ciare’s NDH 15-4 instead of the NDH 15-3. I also used the same crossover design with components of similar quality. These drivers have not been abused.

Seas T29CF001-E0038... $200 for the pair.
PHL 1130..................... $200 for the pair.
Ciare NDH 15-4............. $325 for the pair.
Crossovers..................... $400 for the pair.

Shipping not included..

Thanks,
Evan

Could not elevating heaters on a KT120 SE cause it to howl like it’s oscillating? I just built the amp and it was amazing for about an hour then it began oscillating and the only thing I can think of is I didn’t elevate the heaters. I’ve checked all connections and voltages and I am at Witt’s end. Ideas appreciated.

FS: Almit SR-LA LFM 48, 1mm solder wire, 250g pack.

I have for sale 250g pack of high performance lead free solder wire (Almit SR-LA LFM 48, 1 mm). Few cm were used, bruto weight is 288g, so like new.

Price: 30 EUR + post costs. Payment via PP.

Hi guys

Im totally new to the Rabbit hole of Audio Appreciation.
I havnt even listened to a high end audio set up before, so i dont know what my listening style is yet.

I am about to put together a pair of GR Research diy "Bravo" speakers.
But i am unsure about what to use with lining the enclosures.

They recommended lining them with a product called "No Rez" which is a specialty product of a type of double density foam.
Unfortunately its far to expensive to import, so it was advised that i go with something like vinyl tiles or butyl rubber dampening mat.

To be clear this is about reducing vibration of the enclosure not about internal resonance/reflects or whatever its called (a complete noob here)
Although, in thinking about it, i would not have thought that the No Rez did anything for resonance of the enclosure because i was under the impression that it required a certain amount of mass/weight added to the walls for that where the No Rez is just foam.

After doing a bunch of reading online, i am trying to decide between two options.
Butyl rubber sound deadener mat or mass loaded vinyl.
And im leaning more to the MLV unless someone has good reasoning otherwise.

One concern i do have about the MLV, is that with its intended application in vehicles it is advised that you use a Decoupling layer with the MLV because it apparently is more effective when appied with some give to it as opposed to laying it straight against a rigid surface like the sheet metal of a car door ect.
So you lay down a thin layer (1/4") of closed cell foam as the decoupling layer and then lay the MLV on top of that. Would that be necessary with lining a speaker enclosure or would that use case benifit more from it being rigid against the walls of the box?

They are a 2 way ported speaker made from 3/4" MDF (well 18mm because im not is the US)

As a side inquiry, if the No Rez in the set up of these speakers isnt for resonance of
the enclosure itself, would i need to stuff them with something to replicate what ever it was ment to do?
Because even though i dont really know anything about the audio world yet, i do know that every component of the original design of these speaker matters.
From the little that i have learnt so far, i know that Danny from GR Research doesnt do anything to his speaker designs that doesnt matter, so changing one little thing will effect the intended sound of these speakers
And because i have no experience in this field, i wont know if i have messed anything up and i want to start off with these speaker just as they are meant to be so i can adjust and upgrade everything else around the speakers as my taste and appreciation grows knowing that the speaker sound just how they are meant to.

And yes i am aware of the irony of that statement in a post about changing the component of the speakers that i want to stay just as they are meant to be.
But when it costs $200 to ship a $50 product from the US to AUS, some compromises have to be made. Hence the search to find a suitable comparative alternative.

Thanks in advance.
Paul M.

Take a look at figure d below, from here Electro-acoustic models

It appears to be possible, using a torus-like baffle, to spread the interference nulls in space and time, so does something similar to this diagram actually become a viable option?

Got a mail from Mr. TI with this link:
ANALOG-ENGINEER-CALC Calculation tool | TI.com
Downloaded and installed it (it runs local on your PC), and checked out a few functions.

Screen shot shows function to find gain error versus bandwidth.

Very, very useful! Kudos to TI for making this available for free!

Jan

Hi All,

I was wondering if anyone still had any LU1014 for sale, i've had two 36v 600va tx sitting around for some time gathering dust, and i though it about time i would put them to good use in the form of an F3 build.

Cheers

Hi,

I would like to buy Twisted Pear Buffalo 2 PCB with trident regulators.

I have posted the .pdf article: LX-mini Analog crossover in the Articles
section of FIRST WATT

Hi.

I just got an Audire Forte. I checked the DC offset and one side is solid at about 10mV while the other is all over the place between 95 and 130mV. Keeps changing around and it doesn't settle anywhere. I tested the amp and it sounds fine. No hums, no pops. I'll be doing a recap on the driver board soon so I hope that will take care of the DC offset problem. I know this amp uses the MPQ6600 and I don't want to start looking for one. Any suggestions?

The channel with the good DC offset seems all original. The output transistors are the originals MJ15022 / MJ15023 (3 pairs). The channel with the DC offset issue has output transistors 2SD555 / 2SB600 pairs. These look like an old replacement and you can also see that some of the caps on the driver board are different. My question is: if they are working OK do you think I need to replace these for original MJ15022/MJ15023 pairs? Could these be causing the DC offset issue above?

Thanks.
Elias

NOS P&G faders. 5k. PGF3020. 28 pieces available. $17/each

Anyone in USA have a kit they no longer want? Would prefer to make it myself rather than buy already built.
I know they are currently available on DIYA store but silver front plate not available until April 2022
Might have to go black if lose patience.

Hi friends , ive bought sec hand para hca-1500a for cheap as untestesed ,the seller said its maybe fuses.

inside one fuses of the r channel was blown and replaced with correct one.

Anyway ive plugged it with light

bulb limiter for precaution ,the amp work normal ,dc offset ok 0mv ,bias ok (15 mv) without light bulb limiter.
The amp playing normal and stable but ive notice by ear some distortion , and then connected to amp to my test bench with 8r 100w dummy load both channels and to rta on pc.

Then i saw the problem . R channel distorted

L channel clean.
after all the tests i cleaned the amp , checked and cleaned all the fuses and their holders,repalced the protection relay ,dexoit pots ,resolder joints and wash the pcb ,tested all the semic' for shorts checked the bias again on both channels and the problem not solved.

Still got distorted r channel.
Thanks

Eldad.
Im adding pics in pdf files.

Hello,

First of all, I am a newbie on tube gear but understand that it is dangerous poke anything inside high voltage device like tube amplifier so I will take extra caution when I measure the voltage.

I had a couple of tube amplifiers before but it had testing point on top plate so not needed to open the bottom plate.

I got fixed bias 300B SE tube amp that does not have testing point so need to open the bottom plate to measure the plate voltage and plate current.

1) To measure the plate voltage, do I connect MultiMeter one probe to Pin 1 (Filament/Cathode) and the other probe to Pin 2 (Plate/Anode)?

2) I am not 100% sure where to put probes to measure the plate current. (scratch my head).

I have two multimeters with aligator clips on each end of probes so will measure both voltage and current simultaneously without moving probes to be extra safe.

I attached actual unit photo as well as schematics.

Thank you very much for your guidance in advance....

Actual Unit Photo underneath 300B tube socket


Schematic

I am trying to do some room analysis with REW. Soundcard is an RME ADI2, with a UMIK2 as mike.
Trouble is that REW refuses to use the UMIK2 for input. It correctly identifies the RME as the output device, but insists to use it also as input device.
If I look in W10 audio settings, I see the UMIK2 and can set it as the default mike and it tests OK.
I have tried both with RME's MADIFACE driver as well as the Java driver.
Any tips of what I might be missing?

Jan

Hello,

I always wanted to restore a solid state amplifier after playing with tube equipment. I wanted it to be something special, exciting, unique and decided on a V-Fet Sony and ended up with this TAN-8550, despite all the warning signs around it.

So, as soon as it arrived, I checked the famous diodes, and they were bad. That result didn't give me any hope for the V-Fets, and sure enough, 4 out of the 12 were shorted. (Interesting enough, only the 2SJ18s seems to be shorted (2 from each channel) and the rest has the same Vgs value as they are factory matched, I think.)

Diving into the dust and the dirt of the online auction sites and using search phrases like "assorted to-3 lot", "nos transistor lot", "Sony transistor to-3" and alike, I could be able to score a couple 2SJ18s with different ratings (all being 53 and above, 53 being the lowest mentioned transistor in the service manual). After my luck run out, I have reached some people from here for more spares and ordered a few 2SJ18s from different sources.

Now, my question is, after hopefully having more than 4 what supposed to be 2SJ18s, how can I match hem among themselves and with the ones that were already installed in the amplifier. I have this simple curve tracer from PEAK the DCA75 but the voltage settings are beyond me. I am a "push the green button, wait for the OK sign" kind of a guy when it comes to solid state. In the manual, it mentions about which resistors to change to which value if unmatched transistors are to be used, but I want to get as close as possible.

It would be great if this thread turns out to be a "screen capture" of today, the challenges, difficulties and problems that some one could face if they chose to restore a TAN-8550 and also a how-to / not-to guide, as I haven't seen any complete thread about the restoration of this amplifier. And some threads date back to 2002...2005.

Best Wishes,
Dirk

Hi i tried to gett a LarsHolt 7252 fm module to work but it Will not do it what
I am going to with it somebody that has schematics obuit the module

Lasse Sweden

Hi. Here I am again with my vintage amplifier copy.
Just when I thought that I was finally done something has to go wrong again...
I was working on the vintage amplifier that I copied from the old solid state radio. It is based around ac187k, ac188k complimentary pairs for the outputs and silicon transistors for all the other stages. I know it is not the best circuit (no thermal compensation or emitter resistors) but now I really want to finish it plus that circuit was in that old radio from the 70s and still works after rough conditions in the workshop of my grandparents.
Anyway. As I was finishing up the whole amplifier module it was working fine but one channel shorted the outputs without any overheating or anything strange. I just touched the input for "buzz test" and it shorted after 1 second.
The other channel works fine for now but I am scared of destroying another pair of transistors...
So here are my questions:
1 was maybe 16v too much for the circuit?
2 what is the maximal safe voltage?
3 can it be converted to silicon transistors?
4 why do you think the transistors failed (they were stone cold!!!)
I personally suspect that I damaged the transistor in previous attempts (I accidentally swapped emitters and collectors around) and it broke down.
This was supposed to be a fun project but it turned into frustration... But I want to finish it now because I want to understand what went wrong.
Here is the circuit diagram of the radio and some pictures...

Hi, I am planning a build with the Dissipante 3U chassis. I was thinking to use the same power connector from the back panel kit, the Schurter 4304 6090 IEC Power entry module. I found this on Mouser, however it specifies IEC C14 or C18 compatibility. Looking for mating power cords on Mouser, no luck. Is this actually the correct power entry module for NA use? I'm certainly no expert on power connector specs, any feedback or suggestions welcome. Thanks.

The most common complaint about diyAudio I've heard over the years is that you have to often wade through thousands of posts to find out how to build something. Often there are little nuggets of information interspersed over the posts, and it's very easy to miss something. For this reason, getting started with DIY audio has been much harder than it should be, especially for newcomers.

When I originally started diyAudio, it was actually to collate online a list of audio projects people could build. Over the years it's grown into much more than that of course, and I am blessed to be a part of this amazing community. However having a single place to find a project, get the information you need, and start building has always been elusive.

I'm happy to announce a solution for this problem - diyAudio Guides, available at http://guides.diyaudio.com.

Right now it's in "beta" and we're putting in the work to set the communicative and visual standard that others can follow. It's not currently linked from diyAudio.com, nor is it open to the public to contribute. But when it's ready, I'm hoping it will form an integral part of the community, especially for newbies, and it will be open for every member to contribute in the way they feel capable - projects, build guides, construction technique, soldering tips, anything that can help other members realize their DIY dreams.

diyAudio Guides runs on another platform, and has a "SSO" (Single Sign On) that is linked to your diyAudio user ID. When you go to Guides, you should be automatically logged in there, and you can comment straight away on any individual step of a guide (which I think will be very helpful).

The plan is that at the end of each guide the corresponding discussion on diyAudio is pulled through or you are directed back to diyAudio for more detailed discussion. We'll work that out later. Right now, it's a bit of a hack, but once we move to our next forum platform over the next few months, we will be able to custom code a nice solution to deeply integrate Guides into the structure of diyAudio.com itself so it's one cohesive platform.

So.. this is just the first announcement. Right now we've only got one guide in there, that's the Amp Camp Amp March 2018 Build Guide. Pretty soon we'll have all of 6L6's other amazing guides, and over the next few weeks work out any bugs. If you have a guide you'd like to contribute, please get in touch via contact@diyaudio.com - we'd love to have you be a part of this early-stage fleshing-out of diyAudio Guides.

I'm very excited about the future for diyAudio in 2018. New forum software, the diyAudio Guides section, and the store finally (hopefully!) being permanently in stock of beginner level kits to get people started in the hobby. We'll be very busy keeping the engine room of diyAudio running...

If you have any feedback, comments, complaints, or bug reports about diyAudio Guides, please post it in this thread.

I need some recommendations for enclosure plans, drivers and most importantly the amplifier modules.Id like to spend no more than $4000.00.
Feel free to chime in if you think I‘m making the wrong move, I just want to consolidate space and have a less intrusive looking audio system.

Anyone tried these 6A 650V GEN6 SiC Schottky Diode as filament bias in DHT?

hello , im puzzled by the freq response of my dual 6" bass drivers , wired in parallel , 3 way foorstander ( SD Acoustics 'SD5' , from 2001 )

drivers unknown, no labels , but seem to be giving an incredible in room response of +/- 1db 30-1khz, which seems bizarre ( well that seems incredible to me )

basically, im trying to lower the crossover point to 200hz , but i can not get the woofer to stop outputting , its pretty flat to 1khz ( I used a textbook filter of 6.7mh + 100uF 2nd order ) ....those values should produce approx a 200hz crossover with 4ohms

the drivers have combined DCR of 3.3R , plus 0.8R inductor DCR

please see the graphs , one taken 10cm away, with the above filter applied ( both 1/48 smoothing)

other graph is with no filter , taken 40cm away

- I dont understand how 6.7mH + 100uF can produce a crossover point at 1khz?

Hello, thanks for stopping by.

I build my own tube amps, pres, FX and things, and have an opportunity to bid on some older equipment that my company needs to move on. They just purchased some very expensive high end scopes, signal generators and power supplies.

I was hoping that some of you might comment on these models so I may better pick one or two to bid on. Thank you! There is:

BK Precision 3017A Function generator
Wavtek FG2C Function generator
Leader LFG-1310 function generator

and for power supplies:

BK Precision 1746B DC power supply 16V @ 10A
Harrison 6286 power supply DC 1-24V, @ 12A

I notice that the the BK and Leader function generators have sweep and/or burst functions which I'm thinking are good features for testing audio equipment.

There is also a Fluke 8050A digital multimeter which looks like something good to have around besides my typical DMM.

Thanks for commenting!
Best,
Phil Donovan - building up an electrics work/build/test bench

I'm trying to decide if I want to build the VFET kit I won in the lottery, 2nd round. I'd like to know if anyone has compared the characteristic sound of the M2 with the VFET amp. I've built 2 M2s and this amp has become my every day amp driving my horns, even replacing my DHT amps. I just don't know for sure if I want to build another low wattage amp. Any experience is appreciated.

Regards,
Milkduds

Hi i recently purchased one of the above amplifiers in working condition off trade me but would like to know more about the company ect or even get some service info schematics ect.
judging by the date codes on the devices i would say the amp was manufactured about the middle nineties but have been unable to find any information on the net any help would be greatly apreciated.
Thanks Peter.

I'm still building my 3-way which is a combination of a bass-reflex low cabinet (2x Visaton W250S), a mid horn (Visaton DR45+M300) and high horn (Visaton TL16H).

But I'm unsure about the low-mid. They (Visaton literature) let that mid horn go down to 800HZ. Looks low for such a speaker for me. While at the same time going up to 800Hz for 2 25cm speakers looks high. The distance between them is coming below a wavelength.

Now I have from a previous build a couple of Fostex FE208Ez around. The full-range I did with them isn't for me as they lack seriously in the low end. But they do sound great in the voice range. They have a good efficiency as well. So it looks as if they might be a good mid-low (400-3000). I dropped the parameters in an online calculator and this shows up as a 4.2 liter closed box. Seems very small but OK.

Anyone experience using this speaker this way?

I dived deep into this subject like many others. It would be great if we could use this thread to just share our projects and our experiences. Might they be technical (implementations) or listening reviews (subjective no problem it is just about sharing your experience)

I would like to avoid discussions if this all make sense, again, just sharing your work and experience.

Reason is, we might pick up ideas on implementation or also find inspiration to try out other clocks in our DAC systems.

having said so, also non DAC applications would be welcomed here (like ethernet switches for example or ADC ?)

Looking forward to your inputs and many pictures. I will take the lead with Post #2 🙂


.

Hi guys, I had a dead Xetec Gravity G500 monoblock on hand, the power supply keep dropped into the short circuit protection mode. Someone has messed with it before but seemed no luck yet more torn PCB pads.

After I remove the module with defaced chip, which I think most likely to be the Class-D modulator, the amp was able to power up without any output.

I wanna ask is anyone had the schematics or able to identify the defaced chip?

I'm considering trying to build an IoT soundlevel meter and wondering if modern 24bit ADCs can support such a use-case.

I'm hoping for a dynamic range of about 120dB, and power draw around 10-20mW (just for the ADC not including draw from the driver and other components). Not too sure about other specs yet.

I saw the upcoming ad4630 which with about 20 averages and scaled down CNV clock gets within the ballpark I think. Prototyping with that package doesn't look fun though and I don't know when the part will be available.

LTC2500 looks like it could be an option, again with some use of averaging.

Anything else I should consider?

If this is my first ever ADC design project and I'm also pretty green with MCUs should I start with an easier task and work up to this? I was eyeing the older AD7766; although it won't meet my specs it looks a bit more simple and like I may be able to use it with an Arduino fairly easily. Suggestions welcome.

Hello all, just picked up a pair of mk iii’s, and looking for advice. I’m new to working on tube amps, but I know what sounds good to me. I’m using these guys, through a Tad-150 preamp (pretty decent Chinese/slightly modded by a guy that used to sell them in Chicago) , and vandersteen 2ce sig II speakers.
Pretty revealing speakers. I listen mainly to rock, so I want it to sound right-
Full and driving. Don’t care for classical, or being able to determine the orchestra
Hall size. Do listen to plenty of acoustic music, jazz, whatnot- and I’ve been a musician for 30 years- so I know exactly how certain instruments sound.

First impression of these dynaco’s- they are good amps. Very musical, with great separation. Not much to complain about. They are stock- rebuilt with new caps, selenium rectifier changed. 550 filter caps.

However- they are a little lacking- a bit thin sounding. Reverb stands out way too much. They’ve got decent low end, and plenty of highs, decent mids, but seems like something is missing. And that reverb area- really sticks out.

I’ve read tons about them, and am not sure what to attack. I thought maybe negative feedback- and I disconnected the 680 resistor and added a 250k pot after it, and it did make a useful control, but the range I got from the pot was way too much, slightly moving it up made a huge difference- mids popped out huge, and gain went up big time. This would be a nice control to have, but this pot was way overkill. I also tried the feedback at the 8 ohm tap, but that was a little too much as well. Anyhow- like I said, I’m new to this and have no idea really- this feedback system is beyond me, and it might not be the right area to mess with.

These mk iii’s replaced a TAD-60 power amp, fairly similar- 60 wpc from 4 kt88’s. It did have a feedback control, and it was quite useful. The tad might have a bad opt, is the only reason I switched.

So what do you guys suggest? I’ve done speaker placement , and my room is small, so nowhere else to go there. Acoustic guitars are missing their full sound. Too thin. Something is missing, or maybe something is standing out too much. I’m guessing missing.

I chose these amps, from what I read about them, good solid amps, USA made, every component easily replaceable, with good transformers, simple- and probably a good intro to messing with tube amps. And I needed something to do locked in the house! Which they have delivered already in spades!

Hey all,

I work for a small production company and was recently tasked with installing XLR inputs on our Fostex 6301B full range monitors. I simply drilled a hole in the housing, rivet mounted the XLR input, and (I think foolishly) wired the pins of the TRS connector to the XLR connector.

Now the speaker has a few symptoms it didn't before. Sometimes it will operate smoothly, sometimes it will get fuzzy and distorted, and other times the volume will modulate while the signal cracks and distorts.

I am wondering if a direct link with the pins is the issue but am not sure. I would love some experienced help with getting the speaker operational again.

Here is a link to the circuit diagram.

Fostex 6301BEAV Service Manual (Page 9 of 12) | ManualsLib