Hi all, a few years ago I acquired a pair of Trace-Elliot Evolution 2 full range cabs from a night club and have been using them as part of a front of house system for live gigs. The original PD drivers have long expired and been replaced with Black Widow and Eminence equivalents (or as close as). The problem I find is that every so often, the RCF M73 compression drivers pop their diaphragms. Was just wondering whether anyone on here has access to the spec sheets for the M73 and its diaphragm N255-N. any info would be appreciated, Thanks

What are good levels of PSRR before you consider a regulator?

I've been working on PSRR using an Aikido-style approach to reduce 50Hz hum and noise for a complicated design - cascoded dual differential with tube ccs front end, drivers and push pull paralleled tubes OTL. Class A. Fully modelled in LTSpice.

The power supply consists of two twin-phase rectifiers to produce ±320V and ±200V rails. Without a choke and approximately 1500-2000uF on each rail results in about 1Vpp for both. The total output noise on the channel is 200mVpp currently (although there's a strong harmonic spread).

The fun is that each rail isn't a inverse of the other rail, hence I've been looking at injecting each rail's noise into certain points to result rejection.

A simple regulator on each power supply rail to give the final smooth but it doesn't hurt to get the amp noise rejection as good as possible first. As always that follows the law of diminishing returns.

I still have to circle back and tune for signal again. I would expect that adding a regulator would then see a return to psrr and then signal tuning again as the final step.

Hello diyaudio friends,


I need to get two informations about the HP Prime G2 in order to buy it, as I want to get a better and newer calculator as my old HP 28S.


At first, I want to buy that calculator WITH a battery charger that can be plugged to the 230 Vac wall connector. What is sold here is without battery charger : HP provides only two cables to be connected at the USB connector of a PC, so the battery can be charged.


Secondly, I need to know where or what to buy when the battery will be dead. There is no information available. I have found that the battery EB-L1G6LLU from Samsung would be OK for the HP Prime G2. Is that the truth ?


I have to say that this calculator is nice, but it has a small USB connector that will not last at long. Why did they provide a so poor connector in order to charge the battery ?


I have tried to get informations from HP France, but did not get any answer about their product. All what I see on the net is that HP is no more interested in selling and producing this kind of calculators ...


Thank you for any information that will help me in deciding to buy or not to buy this calculator.


Best regards 🙂


rephil

3rd group buy for Synchronous Bridge & ZENO MKII power supply

Links to second GB and first GB

Here I start the third group buy for synchronous rectifier Saligny.
Prices are same as second GB and listed on google spreadsheet.
Those interested are invited to subscribe here Saligny - Synchronous bridge 3'rd GB - November 2020 - Google Sheets
Please note that prices do not include 19%VAT (only for EU) and 4% Paypal fee.

Here is what I offer:
Saligny LC - LT4320 based, the smallest synchronous bridge in the world, mainly because there are no other manufacturers that make these 🙂 , only 10mm x 10mm, max100Hz, min6Vac to max40Vac and max5A continuous. Do not support centre tapped trafo.

Saligny Standard - LT4320 based, the bridge that cover almost all necessities, 28,2mm x 32mm, max100Hz, min6Vac to max 51Vac, max20A continuous. Do not support centre tapped trafo.

Saligny HVHF - based on AUIRS1170, the bridge that rule them all, max 100000Hz, min24Vac to max310Vac, from 3A to 10A, depending on voltage and mosfet used. This is a custom made bridge based on your requirements. Please mention in spreadsheet voltage, current and frequency, if higher than 60Hz. Support centre tapped trafo.

Saligny HVHC - A new upgraded version will available soon. This was temporarily removed from this GB.

Zeno MKII - ultra low noise regulator employing Saligny LC, able to deliver 4A and any voltage between 0Vdc and 15Vdc. Input - max 14Vac. Output - max 15Vdc.

My apologies for those who are expecting dual diode at 1200V. This is no ready, manly because of the final cost. I have used UnitedSic FET's and these are painfully expensive / wonderfully parts.
"Pain is so close to pleasure"

All orders will be shipped in payment order as soon the goods are ready. Due COVID restrictions, orders to NZ, may be shipped via UK.
All Saligny boards are hand made by me and my brother.

Regards,
Tibi

Hello,

My wife and I (actually girlfriend of 15+ years) would like to spend a weekend with our two children and our two dogs out at Sea Ranch this season. I have a functioning digitally controlled Weller soldering iron as well as a pair of Bose 901 speakers in fair shape (stands included, EQ box not) for trade in pursuit of paying for a domicile (happy to pay) so our family can experience a well-earned weekend at the coast.

Thank you so much.

I think some of you might be interested in this - a vented and "TL" alignment modeled with the same external box size and same mouth CSA.

From the looks of it, the TL approach allows for better control of resonances in the midbass area, at the expense of worse performance at higher frequencies.

Hornresp also predicts at 1.5dB difference at Fb, but I'll bet that difference will be a bit smaller when losses are taken into effect.

I am about undertake my first pre build. Any thoughts on using THIS as my power supply? The Janus shunt regulator give a voltage range of center tapped transformers but no amp ratings and the the 5V tap requires 2A the one I have chosen is 5V at 3A.

Amp goes in protect when input signal is increase. With gain set at different points it will still shutdown when I increase signal from the head unit.
Pulling R94 and d234 one at a time did not make a difference.

Any suggestions?

Symptom is no audio, power supply is fine, +/-15 is good, and output stage is oscillating correctly. I was able to figure out that there is audio present to the input of the preamp card but nothing coming out so I’m guessing an OPAMP went bad, but everything on the board is so tiny I can barely make anything out. If anyone has repaired these before, is the audio path through the JRC4560’s near the phase switch? If so I can likely follow the signal till it disappears then replace the offending IC, but I’ve never worked with this brand before.

I have this machine experiencing following issue:
sound output regardless whether in headphones or speaker terminals A/B is full of noise and weak.
Changing a DSP mode affects the type of output in some modes having more noise then in others but signal is still weak and hummy/noisy when I switch off DSP no sound at all.


Which module might be faulty? There is quite a number of boards inside this beast so I would like to pinpoint specific place.
Thank you in advance

Hello Friends,

I've got a problem with an amp on my desk right now in that the power supply measures inconsisten voltage after rectification stage, see diagram.

The yellow highlighted caps are bulged and need to be replaced, though before I go to that expense, are the caps causing the voltage issue or must I look elsewhere?

As always, your help is hugely appreciated!

Hi All,

Part of the reason I wanted to join this forum back in 2010 was the project that I'm about to embark on. I've worked as a teacher for 25 years and all this time there was a dusty old PA amp way up in the top corner shelf of my parts supply room. It turns out it was the heart of the original PA system here at the school back in the late 40s early 50s.

I've been reading up on Octal Amps from this time and realized that 1. I have the tubes (I've tested the amp and it still works and I have many other tubes as well -- looks like there used to be radio courses here back in the 60s) 2. I have lots of extra parts -- and some interested students 3. It looks like an old Princeton Amp with a 5V3, 6SC7, 6SL7, and two 6V6s.

Here are some pics... I'd like to keep this project short and sweet and cheap -- my budget for this year is blown. The circuit board is small and it looks like a lot of the soldering is point to point.

I've looked at Rob Robinette's site which was very helpful but I'd like to hear your opinions on this project. I've already relocated the output transformer to the top side 'cause I think it looks cool. What do you think?

IMG_7871.jpg - Google Drive
IMG_7872.jpg - Google Drive
IMG_7874.jpg - Google Drive

Hey all,
Over past few months I've toyed around with the idea of building a tube amp from a kit, and just the other day this DIY built amp came up on craigslist.

The listing stated:

"This was built by a local hobbyist who passed away awhile back. I bought it from his estate. I tested it for a good 30min before purchase and it sounded absolutely wonderful. But, when I got it home it has a crackle. I can only assume something shook loose in transit. I have zero repair skills and have bought something else. I wish I could get it working. The 30min I tested it sounded magical."

When I got it home I plugged it in, connected it to some speakers, and all tubes lit up, there wasn't any crackling, however there is a low background hum, and more importantly a fairly loud oscillation which comes and goes, oddly when I push down firmly on the front of the amp by the volume knob I can get it to stop, although it seems to come back when music is on. Strange.

Now going from "I'd like to build a kit" to "I'm trying to troubleshoot a kit of man who has passed on" might be jumping into the deep end a little bit, but I guess we'll see if I'm biting off more than I can chew here.

So first, does anyone recognize this build? If it's a common design maybe I can find the schematic and work off that.

Secondly, where might one start to troubleshoot these problems? I would assume the oscillation first, and then maybe the hum after.

Thanks for your input!

Presenting thread here: Babelfish M25 R.2/SET amp


Schematic and pcb screenshot post #1 , plenty of pictures after .

Tips and Tricks thread - will open, sooner or later

Reading entire thread is advisable , same as inquiring any technical question there : Be sure that you are aware of all things electrical and mechanical !


Pcbs are made for UMS , mounting directly to heatsink


Do not hurry - read , think , ask and only when you feel that you want it and can make it , proceed ...... advice which I'm finding applicable on practically anything .

For anything else , write either here , send PM or directly to >zenmodiyaudio@gmail.com<

Prices are mostly dictated with small scale nature of operation (as always is case) and time/work involved in matching and soldering little buggers.

For ordering , contact me at above written e-mail addy .





Kit options :

Option 1.
- LCH pcb ,
- RCH pcb ,
- all smd buffer JFets (Toshiba 2SK2145BL) presoldered ,
- smd precision CCS chips presoldered
- all smd caps and resistors presoldered ,
- 4pcs of 1uF MKC caps (for important bypass positions) enclosed.

Full price , including Paypal fee and P&P for registered shipping all around the Globe - 135E

Option 2.
- LCH pcb ,
- RCH pcb ,
- all smd buffer JFets (Toshiba 2SK2145BL) presoldered ,
- smd precision CCS chips presoldered
- all smd caps and resistors presoldered ,
- 4pcs of 1uF MKC caps (for important bypass positions) enclosed.
-all multiturn trimpots
-output mosfets , 2 pairs , IRFP240 & IRFP9140
-TP2640 tiny mosfets for SET amp - source follower/level shifter duty
-cascode bjts
-optocouplers
-all electrolytic caps (all Panasonics ,except Elna Silmic II for one signal route position)
-one-pin sockets for special resistor positions
-all (MF 600mW) resistors
-T0220 heatsinks - 4pcs
-etc.

to recapitulate - everything what goes on pcbs , excluding signal xformers and pcb/mosfet mounting screws/nuts/washers ;

Full price , including Paypal fee and P&P for registered shipping all around the Globe - 185E



If I have everything in drawers in moment of order , can ship in a week time;
If I don't have any of normal parts in drawer , shipping could be delayed up to 3 days;
If I don't have pcbs in drawer , shipping could be delayed up to 2 weeks;
If I don't have most critical part for getting in my neck of wood - CCS precision chips , shipping could be delayed up to 3 weeks.
All in all - you all know that ZM is slow, but inevitable

Handy Addendum (in short : HA!):

-Cap Bank pcbs - set of 2pcs; dual rail, CRC (pads, if you want differential CLC), snap-in up to 35mm Dia, resistor and pads for LED, position for 10mm NTC connecting Audio GND to chassis;
-NTC pcb/ FW style Soft Start - set of 2pcs; each having place for 2 independent NTCs;depending of arrangement of primaries of Donuts you're using. you'll need either one pcb for two Donuts, or one pcb per Donut

HA! set is 25E more

see pics for HA!; lazy to search do I have photo of NTC pcb, but who cares

I want to buy 1 Black forest pcb for M2x.
If you got one leftover,otherwise I´ll buy 2..

I have the pleasure to sit with the brilliant Bruno Putzeys from Hypex Audio fame. It's no secret that he truly broke ground to make Class D amplification mainstream within the HiFi community.


Kii Audio, Purifi Audio, Mola Mola & Hypex | Bruno Putzeys | Ep 31 - YouTube

Afternoon.





i picked up a damaged nad 3130 recently and decided to repair it as i have a good front cover spare.


in the pictures you will see circled in red the parts i replaced as they were all faulty, the 2 resistors were scorched,but the resistances seemed ok.


the rectifier was faulty-replaced with an 8amp unit

the 2 no T4a fuses were blown-replaced
the 2 no power caps were replaced with new ones
Q 418,417 and 416 were all faulty,Q 415 was only showing a reading of 3.5v so i replaced that as well
the 2 scorched resistors were replaced


now i finished doing this about 10am and have had it on since,using all the outputs, then all of a sudden the sound on one channel started getting very distorted and then i heard the resitor burn out, so i turned off straight away and opened it up to fine R412 totaly killed, but fuses still in tact.i couldnt see anything else visualy that looked burned.



im thinking over current? but at the moment ive not looked at it and proberbly wont get a chance untill next week now, so i wondered if you guys had any thoughts.

Hi all,

I have the following for sale:

MiniDSP 2x4 HD, kit, new in box - $100 (one left)
MiniDSP 2x4 HD, full, new in box - $125
MiniDSP 4x10 HD, full, new (never assembled), not in original box - $300
MiniDSP UMIK-1, like new - $50

Behringer Ultradrive Pro DCX2496 - $100

Lake Audio LM26-U - $1,000 (retails for 4x this)

Please email or reply here...
db@aforara.com

Thank you!
Rob

I rebuilt this driver with all premium passive components and the original Toshiba transistors. For some reason I can't get it to balance. The bias adjustment has almost no effect (.01-.05v)

Everything seems fine until we hit the darlington. The transistor seems to bench test okay but the hFE is too high for my multi-meters to measure. I swapped it out for a KSD1692-D(Y) and it made no difference at all.

Point 'U' is a constant -2.59v. The pot lets that side of the voltage divider to swing from 1.8-2.53v so it should balance but nothing happens.

(large)

The power rails are all 2v higher due to the Schottky efficiency from the power supply and ultra-low resistance traces. Any chance that would affect the bias due to the diode on the one side of the bridge?

Or is there something downstream that is pulling the bias out?

Thanks in advance.

Hi, i have a boozehound phono pre I built a couple of years ago, been happy with it until yesterday when the left channel suddenly went quiet. I believe the problem is the jfet on the output stage.
My question is: can I replace just the bad jfet, or do I have to match it with either the input jfet or the output on the other channel?

Can’t recall what was in the original kit and Unfortunately boozhound seems to be out of business.

I believe the topology is similar or close to the la Pacific phono pre.

Complete Module Driver and Power with DHT 6B4G

Hello everyone,

There in some time, I realized this development and this card gain for Power single-ended triode 6B4G.
Since these objective performance was considered excellent, it continues to be a hit with music lovers and DIYer.
Subjective for their performance will of course be related to the quality of the output transformers used and the power supply. (Preferably based tube What else!)

I present the module in a few lines I present below:

This compact card (100 x 160) offers a full floor mono power. It uses a famous triode 6B4G a comparable type 2A3 in a single-ended configuration and one ECC88 ECC81 or a cathode follower configuration bootstrapped.

This configuration offers many advantages such as wide and very low distortion bandwidth. The results are tuned up to the great musical qualities of the triode.

In addition, many features of the card, and it also includes the power to the cathode of the power triode. It uses fast recovery diodes (35ns) in TO220 (16A) followed by a smoothing capacitor, a regulation (of course adjustable) and perfect decoupling and a low output impedance.

It also has all the necessary quick and easy connection connectors. No son to weld!

If need more info. Do not hesitate.

Photos and information in French in my Blogg:
Pilote &puissance Single ended 6B4G

Also note that you can check the thread below for information, diagrams and additional notes:
MATCH 6B4G Sovtek_ 6C4C Nos - ELEKTOR

Important information: Please note that this is not a kit, I did not realize that indicates what documents or welding and soldering, it is much too complicated. I book more readily complete modules, welded, cleaned and tested, simply connect with the elements annex but no less important as the power supply, and of course the TRS.

To a lesser extent people with experience may have PCBs and using diagrams and pictures it is relatively simple to achieve complete assembly without errors.

Best regards. Tony

For sale,

FaitalPRO 6HX150 Mounted in baffle for test decided to go different route.

Rdy to ship in original packaging.
$350

Thanks

Anyone purchase any replacement shielded coax for vintage Mac products? I have a few C26s and C28s and I need to replace some of the shielded coax. Some is 1 conductor with a ground grain, some is 2 conductor with a ground drain. I know I can search the internet but thought I'd check with the group here first! Thanks in advance.

Hi all,

Iam sure someone would have posted these questions already, but I need help with choosing the right amplifiers for my exact speakers. Iam not from electonics background so most of DIYs i see are helpful until I start looking at the Class D apms which confuses me.

So any help would be appreciated.

The system came with a player and amp all built into one case. I left it for a few months without usage and ants turned it into their house. There are no spares available since its very old, but the speakers are very good. So wanted to try and use them with a few inputs like, Optical, Headphone, USB, HDMI, etc. At least the ones that are possible.

My hometheatre is Sony DAV-DZ370 5.1 1000W RMS. Details below,
Front L & R, Rear L & R and Center Speaker Details. All 5 are of same configuration.
Wattage: 143 W
Rated Impedance: 3 Ohm
Type: 65mm Cone
Full Range Bass Reflex, Magnetically Shielded

Subwoofer Details
Wattage: 285 W
Rated Impedance: 1.5 Ohm
Type: 165mm Cone
Subwoofer Bass Reflex

Original Amplifier details
Stereo Mode: 108w + 108w @ 3 Ohms, 1 kHz, 1% THD
Surround Mode: RMS Output Power FL/FR/C/SL/SR 143w per channel @ 3 Ohms, 1 kHz, 10% THD
Subwoofer: 285w @ 1.5 Ohms, 80 Hz, 10% THD

I was thinking of a few TPA3116 but the Ohm rating threw me off. Any suggestions on how to reuse the speakers alone please. I don't want to waste them since they are in excellent condition.

Link to hometheatre manual: Access Denied

Hello,

I have a 12W 211 amp, which was finished by a friend who cannot recall all details and the amp is currently waaay tooo HEAVY to move easily from it's position on a shelf without a lockdown illegal additional pair of hands.

I have been taking some images with a phone from the underside to see what I can learn and this has prompted a couple of questions on impedance. Of course all will be answered to some extent with my ears once I can move the damn thing and rewire the output transformer to see but in the mean time for my much needed education:

I have 8 ohm speakers, the output is currently wired to 16 ohms, who will this affect the performance.

The primary is wired to 10K, but has a 7.6K option, and this suggests as mine is 1000V and 12 W class A design I should consider the 7.6K....
http://www.tubecollectors.org/archives/vt4c.pdf
BUT everyone seems to sell 10K primary output transformers for the 211 (does everyone expect to run 1250V?)

Thanks

Hi, I built years ago 2 mono speaker amps, based on Mini Aleph 10W class A cards I ordered on ebay. It served me well for years (except for the heat..), but I can't use it anymore as a speaker amp (moved to a small apartment in Paris).

I connected my HD600 to the Mini Aleph outputs, and was pleased with sound, except for the bass section which was muddy and lacking impact compared to other dedicated headphone amps I own. The HD600 is a 300ohm HP, and is not reputed to response well to EQ, and I can confirm that.

Is there something I could try to improve this aspect, like swapping resistors or else ?

Have a nice day
Pierre

Can I just put a 16 ohm (32 ohm?, 64 ohm?)10 watt resistor across the outputs? I'm not sure I want to screw around with all the diodes in a 'catch diode' scheme. It's for a SMSL SA-50. I'd just hate to have it blow one day.. thank you.

Hallo friends,

I have a problem of the stereo lamp which dosen't work. of course the lamp's ok.
Radio works perfect except the light.
There is no faulty semiconductor or any other component.
I have tried some ferrite and turned back the original positions. nothing have changed.
Is there any idea about the problem.

Hi all,

So I'm currently playing with this cheap but neatly built active crossover from Breeze Audio (China cheapie).

Ever since I've started using it I started hearing fluctuating high pitch noises in the tweeters, like a whistling sound that comes and goes; it is fluctuating in level and in position, going from one channel to the other like a UFO or just in both; then disappearing. sometimes a lower frequency buzz comes along.

My speakers are 104dB horns and compression drivers, I think it would be much fainter on regular cone/dome speakers, probably barely audible.

I've been experimenting with cheap Chinese discrete op-amps wich went quickly out as they had very bad DC offset; I now use OPA2132 but with all op-amps tried I was getting these interferences.

At first I've been using this device with ultra cheap, unshielded interconnects and I thought they were the reason, but now with shielded interconnects the noise still comes and goes, although it is maybe fainter? (not sure here).

I have a wi-fi modem just a meter away from my stereo equipment; not an ideal situation but I didn't have any issue so far. There's also an office with about 6 computers just above my head. Parts of the electric circuit are shared as this is an old house.

The crossover itself is enclosed in a nice, all aluminum, thick box that should provide some protection against RFI...
I've received yesterday some bag full of cables and tweaks from a friend; there are some ferrite beads to clip on cables, various sizes, I've tried few locations but while it seemingly improved on some stuff (probably placebo!) it didn't help with the noise so far.

Is what I'm hearing really RFI or are my OPA2132 oscillating (but I've never ever had an OPA2132 oscillating...)? I could add some 0,1uF MLCC cap under each chip and see if the noise goes away... but its fluctuating nature makes me think more of interferences...

There have been several requests for a simple and cheap high power amp for DJing or PA recently.

The circuit below is the Elektor PA 300 in a high power version. You can easily bridge it to deliver more than 1kW RMS into 8 Ohms.

Have fun!

10v/ms vs 30-35v/ms?i see meny amp brands new models with 10v/ms slew rate.can compare with 35-40v/ms amps on sound reproduction performance?

Sorry, does anyone know the Pascal PN:U-PRO2S how to synchronize the frequency of IRS2097S ?

I have Pair of Nemo and last year one of then (left Channel) seems to breaking up the sound. I called Electrocompaniet and they told me to send it to service center to replace the output Relay. so I did and after that Amp sounded way more open to the right channel. but right channel was still not sounding bad but one can figure out the sound from left (with New relay) was far better than the right one. Fast Forward 6 months right channel has developed the same fault, sound is now breaking up just as it was in left channel before replacing the relay. my frustration is I asked service center if its recommended to replace the replay on both channels and I was told why repair if its not broken. regardless to what they said, I now need to go through the same exercise I again.😡

But wait a minute, I realize that output replays can be cleaned up. I am trying to DIY the cleanup part before I send it to repair. If cleanup can solve my problem I would be a happier DYIer 😀. but I need community's support to guide me how to identify the relay and how to reach there. I know Nemo is just 2 AW250 stuck together 🙂 so if anyone has done it on AW250, that would just make it perfect.

Appreciate your response in advance.

Playing around with different woofers to be used with my Fostex ff85wk. Can I use it open baffle like several of Martin J King's projects or is it still best in some kind of MLTL or BR perhaps integrated into my woofer box design? Thanks for any and all suggestions.

Good day everyone.

I came across this diy phono amp kit on eBay and I’m wondering what was this referred from? Some other listing mentions “German” design but no actual model or brand names.

When first powering this amp it drew no current and no lights came on. Powersupply was shorted and I replaced mosfets, gate resistors, buffer transistors and UC3526adw. After replacing all this the amp power light still doesn’t light and gate drive is different amongst the two banks of outputs.

I had read several places that it's a good idea to delay the turn-on of B+ to the plates until after heaters are on. Something about not hitting the anodes with high DC voltage until the heaters are working. But then more recently I've read the opposite, that you shouldn't delay B+, but rather should perhaps switch it on first. Not sure of the rationale given for this approach.

Can anyone (or lots of anyones) provide some thoughts on this? I just don't have enough experience or theoretical knowledge to make sense of these two options.

Thanks!

Got my hands on a pair of Martin Blackline X12 pro speakers and decided to pull one of them apart to see inside as well as some basic measurements. If you're not familiar, this is their entry level 12" LF + 1" CD horn cab (assembled in China).

This speaker appears to use OE version Celestion drivers, likely made to Martin specs. The cabinet fit and finish is first class, considering this is a far east made product. Lots of nice CNC work went into it. The grille is secured with its own spring tension and rests in slots cut into the sides, so no screws used. The downside is removing them without marking up the exterior coating, since you have to pry against the woodwork to remove the grille. The enclosure has a decent amount of internal bracing and effectively helps minimize panel resonances (as seen in the system impedace plot). Lots of fly points available on all sides of the cab, so its very versatile. This makes a great floor wedge too, as you can rotate the waveguide for horizontal use.

First listening impressions are very good. They sound very balanced and actually very neutral for a PA cab, but the low end is a bit lean. They can play quite loud without signs of strain or harshness. For 650 bucks a piece, they are a hidden gem especially when compared to other passive cabs around that price point.

The crossovers are very well made and I'm impressed they only used metal film caps and air cored imductors, even on the LF low pass, so no core saturation or distortion as well as any electrolytics to deteriorate. The caps in series with the HF driver are PP while the parallel caps are MKT. Thats very smart cost cutting. The crossover circuit uses a 2nd order LP filter and 3rd order HP with CD compensation, which gets around using a resistor pad through a very small 0.8 uF cap in series, so in theory the HP is electrically more like a 2nd order design and apparently enough to flatten the upper HF with a slight rise in HF response past 10 kHz. Again, very clever.

Both LF and HF are clearly Celestion pieces. The HF driver looks internally and sounds like a CDX 1-1745. The non-metallic diaphragm makes for a smooth sound and reminds me alot of the popular B&C DE250 driver. There is no hint of harshness and you would be hard pressed to tell your listening to a compression driver on a CD horn. Not sure about the LF unit, as it doesn't measure or look like any of their off shelf models. The crossover point is around 2100 Hz. Thats a bit high for a 12" LF driver which will hurt off axis midrange, but it still sounds great. The cone appears to be made out of their Kevlar loaded paper formulation. Its a very stiff cone compared to other paper cone drivers. The surround is fairly narrow and won't facilitate larger amounts of cone excursion, however would help with midrange linearity.

Overall a great speaker, but really needs a sub to cover most of the range. Considering this, it's one of the better PA cabs I've heard under 1000 bucks. No, I'm not being paid to say this, just giving credit where it is due. Wondering if these could be improved upon through some basic tweaks ie. extra enclosure damping material.

I have a modushop slimline case to use for an amp build & am a bit unsure about how best to safely ground the chassis.

It is made from anodised aluminium panels on the sides/front/back and painted steel sheets for the top/bottom. These are joined together via a number of grooves in the side panels. If I put a ground lug into the base alone then I'm not confident the base panel is going to make a secure connection to all other panels even if I grind/sand away the covering where the panels meet.

Alternatives I've thought of include running additional cables from that ground lug to each panel or attaching some internal metal brackets to join adjacent panels.

Any recommendations/tips on how to deal with this would be much appreciated.

Some pics to illustrate

the grooved side panels:



the top/bottom attach via a bolt slid into the 1st channel, panel is then screwed into that bolt



the front and back then attach via screws that are threaded into the next slot down, I think the panel is anodised after threading.

I'm trying to follow Rod Elliot's instructions for making an Expanded Scale Voltmeter and I need a little bit of help and/or confirmation, please.

I have an analog meter that has a printed scale from 100vAC to 130vAC that I'd like to use to measure AC mains voltage. I am hoping someone can confirm my calculation of Rz which biases the zener diode in the attached schematic.

Here is what I have so far:
The meter coil measures 216R. Full scale deflection requires 87.3mV at 0.4mA.

I'll rectify the 120vAC mains voltage to DC, so the 100v to 130vAC range printed on the meter faceplate translates to a range of 141v to 183vDC, thus I have a 42vDC range to work with. I have calculated the value of Rmult as 42v/0.4mA = 105k ohms. For adjustment, I plan to use a 100k fixed resistor in series with a 10k pot.

To be able to measure DC voltages from 141v to 183v (and ignore voltages below ~141v), I was going to use two Zener diodes in series (100v + 39v). I am unsure about how to calculate the value of Rz so that it places a ~10% current load on the Zener stack. Rod indicates to use Ohms Law, but I am unable to duplicate his calculation of 470R for his example and implement it with my own set of numbers.

Is the following correct?
If I use 1w Zeners (100v + 39v), the maximum current draw will be 1w/139v (lowest measured voltage) = 7mA (max rating of 1w zener). Looking to limit current draw to 10% of this figure, my target should be a current draw of 0.7mA.


Using Ohm's Law, Rz = 42v (max net voltage) /0.7mA for Rz of 60k. Is this correct?
Or should the calculation of Rz be 183v (max total voltage) / 0.7mA for Rz of 261k?

I'm confused...

Thanks for any help here!

Hello DIY enthusiasts.

I have all the components for the above speakers (woofers, tweeters, and all crossover components) for a pair of these speakers. This design is on Troel's website under the Seas section ('Seas 5-inch Projects'). I have the W15LY001 woofers. All of the components are brand new, and I am prepared to give them away for free, but I will not pay shipping costs to the person that wants them.

I have health issues and am unable to undertake projects like this anymore.

If you are genuinely interested in building this design, and not just adding to your spare component collection, please message me and we will take it from there.

Joe H.
Vancouver, Canada

Hi all 🙂

I ordered and received an AMP10BASIC (41Hz Audio:AMP10-BASIC kit) from 41Hz Audio. It arrived in good time, but the forums are STILL down and I can't access the build instructions.

Several emails to the store owner have gone unanswered (but that seems to be the norm having done some searching).

Can anybody help out with instructions? I'm not confident enough to solder it based solely on the schematic.

Many thanks!

I'm wondering where there the best place to go to place an add for a Leak stereo 50 tube amp.

In case anyone is interested in why I'm looking:

I was given this amp by a deceased engineer's wife looking to clear her house.
It appears that the original owner (Scott Kent, well know audio engineer known for Revox A77 upgrade service) had provided some of his own maintenance being a proficient EE and liked to keep his gear optimized. I also bought a few of his 90's era Lexicon reverbs (300 and 200). My initial intention for the amp was to remove and test the transformers for use in a project of mine I had set out to do months ago.

I came to this forum to ask some questions about the transformers and one of the posters commented that these transformers could be very valuable to someone who is passionate about restoring these vintage tube amps. After some pondering I had to agree plus my project would probably do just as fine or better with some of the offerings from Triode Electronics - in particular the Dynaco stereo UL transformer bundles. This poster left a link that led to the same amp I have for nearly $2000 but, it definately looked allot prettier than mine! The fact that I cut the wires to the transformers to remover them for testing may have lowered the value, I don't know.

But, suffice it to say I would be happy either getting the cash or trading it for the Dynaco replacement transformers that were found in the ST70. I'd even consider lightly used.

If there is a particular place where folks who find value in these amp please let me know. I'll place the add and see how things go.

Thank you!
Best,
Phil Donovan
617-470-9821
donovanphillyboy@aol.com

Hi:
I have Sams Photofacts from Vol 1 and up. They were in about 6 or 8 filing cabinets , now in cardboard documents boxes.
I am in Charleston SC.
Email me at njvet01@yahoo.com
Come and get them.
Ed

Hi,

I'm on a journey of building my first portable "boombox".
As this is on a really tight budget, over the past couple of months I have been gifted and buying several parts. It seems that the only thing I still need is the subwoofer.

A quick overview of what I already have:
- Arylic up2stream amp 2.1 2.1 Amplifier with 100W+50W *2 for DIY Audio-Arylic.com
– arylic
- Dayton audio LBB-5S with accessoires: LBB-5S 18650 21V Lithium-Akku-Platine mit Balance & Ladeschutz - SoundImports

For the speakers I have:
- 2 pioneer 2-way speakers: Support for TS-A6958 | Pioneer
- Dayton audio passive radiator 12 inch: Looking for a Dayton Audio DS315-PR woofer? - SoundImports

Now it seems that I only need a subwoofer to start building the enclosure.

I had my eye on the GRS 10SW-4:
Looking for a GRS 10SW-4 woofer? - SoundImports

Now, my knowledge for all the parameters of a subwoofer is not great, but I saw that the Qts is important for what type of enclosure it needs (sealed, vented) and it seems the Qts of the GRS is 0.63 and it seems like the passive radiator would not have a great effect on that?

Another subwoofer I was looking at is (which is already a lot more expensive) is the Visaton W 250 S - 4:
https://www.soundimports.eu/en/visaton-w-250-s-4.html

But that's more of a midwoofer I think? Seeing the frequency response.
But that woofer has a Qts of 0.35 which would maybe be better suited for the passive radiator?

Unfortunately my knowledge for all these different parameters is not great, so my questions would be:
- Would the GRS subwoofer be a good combination with the passive radiator?
- Or does anyone have a recommendation for a budget subwoofer which would go nicely with the rest of my parts?

Thanks in advance!

Hi,

I have found this quite old topic:
Kiwame resistors

comparing the KOA Speer SPR carbon resistors versus the well known KIWAME carbon.

I use very often the Metal KOA Speer resistors, but I mainly have 2 questions:

a-/.how would you define the sonic differences between carbon and metal resistors ?

b-/.what are the conditions were you preferred Carbon resistors over their Metal counterpart ?

Thank you very much,
P.S.: I see that this topic should be moved to the "parts" forum (sorry),..., maybe a moderator can to this... Tks

I recently realized I effed up and reversed the screen and suppressor on a PCB for 6P45S.

The thing is though, isn't it a beam tube? I know I'd still have a triode if I tied suppressor to plate instead of cathode, and in the past when I push things like this, I'm worried about something burning out, but this is a beam forming plate, no? In theory it should not only work well as a triode but handle extra Pd since it's a plate not a wire?

I don't want to waste a pair of 6P45S trying this before some other people think I'm sane here. I've already had one tube plate cap come off, and another roll off of the table and smash...

Worst case? In a week the corrected boards will come.

I'm getting ready to build a bucking transformer / amp power switching box. So basically power cord-->fuse-->switch-->6.3V bucking transformer (6A)-->power outlets. There will be 2 outlets at full wall voltage and 2 with approx. 6.3V subtracted. Tube amps (with vintage power transformers) into the bucked voltage outlets, and a solid state bass amp into the wall voltage outlet. The switch will switch all 4 outlets.


My question, is it preferable to switch both hot and neutral or just hot? Location is U.S., (120V AC), most electronic equipment switches hot only, but this is not exactly the same, as the switched power exits the unit.

Hello, I own an original Pass Aleph 1.7 preamplifier.; here's my question:
are the 4 inputs electrically identical?

This is the manual:
"Next to the inputs on the rear panel, the preamplifier offers tape outputs through both XLR and RCA connectors. This output is a direct connection to inputs 1, 2, and 3 when they are selected from the front panel. Input 4 is deliberately not available through the tape output connection. Input 4 is designated for use with a tape recorder if you have one, and we have arranged that it will not place its output on the tape out, which will prevent you from accidentally creating a feedback connection with your tape machine."

My technician claims that output 4 is quieter and with less distortion than the others.
Questions:
1) Is it a smart move to use input 4 for the main source (cd)?
2) Is it useful or wrong to use the xlr shorting plug even in the inputs that I don't use at all?
3) What is the optimal setting between the gain potentiometers and the volume control?

Thanks.

I’m having a bit of trouble with this amp, mainly to identify some parts, mainly resistors along the drive circuit near the output mosfets. RES1, RES6...

Hi friends
I had the occasion to get a FR 24 mk ii for little money, so couldn't resist.

The tonearm seems to be in good condition, I haven't been able to test it yet.
I am on the lookout for a good cartridge for it, and haven't found any information about the mass of the arm, so maybe can somebody here tell me the number? (All I could find was that it was playing very nice with "most" cartridges. So, not that much, or precise, information)

For reference, I have attached everything related to the arm I have found.
(The txt file "ve_fidelity_research_fr_24_mk2_jp-ocr-DE" is a german OCR-translation of the manual, edited a little bit. Lots of nonsensical stuff in there.)

PS: I am wondering if a AT33PTG/II would be a good fit? I hear a lot of good opinions about AT carts...

PPS: I am still not decided what Turntable I should use it with.
So far, I have some at hand: Thorens TD 125 mk 2, TD 150, Systemdeck III and another nice british one which I don't recall the brand. (That's quite nuts, I know. Once I settled on one, I'll sell the others)

Hi everyone,

Long time lurker but first time poster here. I'm already most of the way through building my Statement II floorstanders, which means I'm about to face up to the shortcomings of the remainder of my system - I think I'm going to need your help!

Mr Noisy

I have speakers placed over wood surface with decolam and the satellites sound very sharp, shrill and piercing, I've tried EQing but has no reduction in sharpness untill I turn below 12dB, at that level many others are getting obscured, is there a free de-essing or dynamic equalization software available for PC?

The frequencies I've tried reducing are between 5KHz to 13KHz, I've noticed that reducing frequencies between 1KHz to 5KHz is also having an effect on the sharpness, I'm confused why this is happening, shouldn't the shrill sounds be in treble region only, are there any sharp sounds in mid-range as well?

Hey all!

I am looking for a rotary switch, a 3-position switch for "Bass Turnover Freq." for Pioneer SA-8500 II integrated amplifier.

Rotary Switch original part number: ASD-057.
Knob original part number: AAB-116.
Tone Control Board (Control Amplifier as Pioneer calls it): AWG-044

If any of you people have one SA-8500 II for spare parts let me know. If pulling that switch out is too much trouble I am willing to buy complete Tone Control Board (Control Amplifier Assembly) with all the switches and pots (and knobs too).

Anyway, switch is a must for me. Knob is a plus thou I am not that concerned about the knob because I can probably get that knob from many other Pioneer models from that or similart era. The whole board is also OK.

Please, let me know. Drop me a line or PM me.

Thanks in advance!

Stay safe everyone,

Krešo

PS: Yes, if eny of you is wondering, I am looking all over the place, eBay, this, that, vintage switches etc. etc. etc. so in case I have missed some good place that carries what I need, your input is highly appreciated and more than welcome!

I just built an HDAM (V1.3) "preamplifier" I bought off Ebay. I knew it would sound good and I figured, why the heck not?

Check this thing out, and yes, it does sound really good.

Yes, it is just simply sitting on top of the inner surface in an aluminum chassis box that I grounded. It is not screwed in, just sitting there.

What did I change from the kit as I built it? I threw out the resistors, 5% carbon film things and used mostly Dale RN55 resistors that I matched by hand. Then I matched the supplied transistors and stuck them together with heat shrink and some thermal grease. The supplied capacitors, 10 pF and 100 pF were replaced with Polystyrene types the ones supplied were ceramic axial ones.

The unit was on for maybe 10 minutes or less when I took the measurements. The only adjustment is for zero DC offset, which was done. It seems to be happy sitting around 1/2 a mV on each channel.

I'm feeding it +/- 20 VDC from an HP 6237B power supply 'cause I didn't have a transformer handy.

Here is the unit I bought on Ebay: NEW Marantz HDAM Circuit Preamp Kit Class A Output with 3-Bit Input Select | eBay It is item # 183526337118.

This kit sat here for months before I decided to build it today. I think there are still a couple left. The schematic is too blurry to make out any detail, but it is there.

-Chris

For Sale: Tang Band W8-1772. Purchased for unfinished back-loaded horn project. One driver is new in box, never mounted. The other was mounted and tested for a few hours max. Asking $400 for the pair. Incredible life-like sound for acoustic music.

Brief history: haven't done thermionic stuff for about 8 years.

When last we spoke. I had several Rat-Lab test set-ups, and was seriously trying to pin-down the best circuit and operating points for a truly simple 6AV5 SE amp using George's SSE board...

Then Real Life intruded. Like George, I worked in a highly cyclical, boom-bust industry (in my case, the "upstream" oil & gas business). It has always been a roller coaster ride, but in 40 years I had survived every single purge & layoff by making myself as big a bargain as possible, which usually meant 50-60 hour weeks, and jumping into stuff which made everybody uncomfortable. The last 8 years have been like that, on steroids, but nothing that I haven't seen since I started in the early 1980s.

Until this year. On April 15th, I was laid-off. On April 25th, I turned 67. On April 26th, my (former) company declared Chapter 11.

(A) I re-read my posts here from ~2012. Honestly I barely recognize that guy, but perhaps I can live-up to his ambitions...

(B) I discovered that I had made a Simple SE flexi-amp, using the SSE board, a healthy PST & choke, and dual sockets for both the 6L6/EL34 family AND the 6AV5..see photos below.

(C) It APPEARS that folks (at least in the US) are still interested in the 6AV5 in SE application, but there doesn't seem to be any longer term data on running the thing CRANKED, ie at roughly double the rated dissipation.
I think I can work on that; otherwise, my heirs will find themselves staring into a box of 6AV5s making unkind comments about me, God Rest His Soul.

Here's some photos of where I am now.

1. very old 6AV5s test mules of uncertain provenance (was gonna say parentage, but it was Sylvania what birthed 'em; ALL my 6AV5s are Sylvania...) GLOWING at 25 watts dissipation: 380V plate, 61V cathode across 780 ohms, 78 mA x 319V = 24.95 W

After a few hours at this op point, these old horses just started spitting & DIED.

(2) the open-back shop speakers. Rat shack 8" so-called "full range" with little Foster horns in ancient surplus kitchen cabinets dyed red. Can't remember the cross-over, but it's low-order and pretty high frequency IIRC. Ain't climbing up there today to find out. This set-up ACCIDENTALLY works good, as the Homasote ceiling reflects the bass nearly perfectly. Very Very open, natural lively. I am seriously tempted to get some 12" Eminence Delta 12LTAs for these boxes. There it is again, WHO AM I KIDDING? Old downside is that at higher volumes, the tools on the galvanized pegboard can start to rattle (see: ZZ Top "LaGrange") which always makes me think the 80 year old Thordarson PST is coming apart

(3 & 4) the Simple SE Flexi-Amp with "auxiliary" sockets, Gen 1.
Should have added an OCTAL input tube socket with off-board biasing (e.g. NiMH batteries, which I really like).
I might actually DO a Gen II...

Current status:
Replumbed the P/S to give ~

• 410V plate (increased C1 from 2.2uF to 18uF), which of course makes the nice THordarson Swinging Choke less relevant.
• Raised Cathode Bias resistors to ~1000 ohms (2 x 10 W in series)
• Running a "new" set of 6AV5s; at 120VAC in off the Variac, I get 409VDC plate, 67VDC cathode for 67mA x 342V =22.9W dissipation. No glow on these puppies with the lights out.
• Contemplating wiring-up a 120V hour meter I found in the stash, to actually KEEP TRACK. Novel idea, huh?

Near this operating point seems to be the sweet-spot for a Simple SE implementation of a 6AV5 SET amp. IMHO, this MAY be the cheapest best SET I have built.

I had an old engineering professor (Fred Hooven, you could look him up) who said that "Engineering is doing for 50 cents what any JACKASS can do for $5". I do believe that's what George has accomplished with the Simple SE board...

More later, muchachos..

I'm using Daphile for a while as I'm running my server in a virtual machine (Oracle Virtualbox).

Ran without any issues but I recently noticed that sda2 is full. I would like to extend this partition. I know this is more or a Linux question than an LMS question but would appreciate any pointers on how to do this.

Hello all,
I just finished my first tube amp! It is basically the Mullard 5-20 circuit and it works and sounds good. The problem is that at around 3.6kHz the transformer seems to be squealing at that frequency. Into a dummy load at 10W, the sound is really quite loud! I'm pretty sure it is the transformer having tried two sets of output tubes from different manufacturers and the frequency and level is the same.
Is this normal or does it indicate some problem in the transformer? The transformer is an open one without bells (just whistles 😉 ) if that makes a difference.
Thanks for your help!

I want to re-use the RCA analogue ins and rewire as analogue outs as I need additional analogue outs to run in parallel to feed a 10X10 miniDSP HD so I can add subs to work with 7 channels.

Any ideas which components I should desolder to disconnect the RCA's to the existing circuit I'll hardwire from the other analogue out connections to the back of the RCA sockets for parallel connections (So I have two separate connections for each output and not need to build 'Y' cables)

It just feels sensible to remove the input connections on the board for the unused inputs. I can take out the resistors but it looks like the relays will still be connected ?

Its the 8 unused red RCA's I want to repurpose and dont want to desolder these from the board but do want to disconnect the signal to the board

There is a little bump on one dome but no consequence on the sound (2nd pics)
Ask 550€ + worldwide shipping (Price new around 1150 Euros)

Dear All,

I need a pair of Esotar T330D tweeters for my new speakers....units have to be in mint conditions, possibly in their original box. Price should be reasonable😀
Thanks in advance.
I'm a reliable buyer (please see massimobar in ebay members), I live in Italy so in case of purchasing you have to ship overseas. Payment via paypal.

Thanks in advance

Massimo

I'm looking for a pair of Dynaudio Esotar T330D tweeters.
If available, please, PM me

Hi guys,

please assist with part number for ic circled in picture

Anyone have any ideas on how to remove the fixative on these boards safely and not damage the board.

I think that many members might/should�� find this post helpful because with an oscilloscope we can test a used amplifier -for example- and find out if it is in good working condition or not (we all know that there are many problematic used amplifiers for sale and sometimes they sell for a lot of money) and also we might want to check our old amplifiers.

I would like to buy an Oscilloscope and use it simply for measuring audio amplifiers' output power and distortion using a square wave.
As simple as that. I would like to get an accurate measurement, quickly in order to check amp's condition/power.

I know that we need a square wave input source, an oscilloscope and a dummy load 4/8 ohms.

I am considering buying this one:

A. Hantek DSO 2C10 with 2D10 signal sourse

Hantek Digital Storage Oscilloscope 2CH 100Mhz 1GS/s DSO2C10+2D10 Signal Source | eBay

or this one:

B. Hantek DSO5102P

Hantek DSO5102P Digital Oszilloskop 2 Kanale 100MHz 1GSa/s

What do you think about the above oscilloscopes and would you buy another for that purpose?

Looking forward for your replies. Please correct me or write about anything on this subject.
We need to be able to check our amps.
Thanks for your time!

You can see the photographs of my continuing DAC project:
http://stereomecmuasi.com/forum/viewtopic.php?f=46&t=965

Regarding the MOSFETS and JFETS are they matched per channel or is the whole set matched, the 8 MOSFETS and the 4 JFETS?

In other words, do you match 4 MOSFETS and 2 JFETS or do you match the 8 MOSFETS and the 4 JFETS?

Thx

Hi,
I have just picked up 2 pairs of these. They are early models and have a few missing/non working panels. The bonus is there is a full set of spare panels for one pair which are in unopened boxes. I've yet to open and confirm.

They have both been a bit modified. Crossovers removed and run using digital cossovers (deqx). Covers and stands a bit scratched and battered. A 15inch woofer in place of 2 panels in one.

I will post a few pictures if anyone is interested. I haven't opened up any of the burnt panels as yet and it might be a few days before I can fire either of them up.

Hoping someone has some experience of these and I haven't wasted my money.
Regards,
kffern

I bought this amp off eBay and the seller said it worked but it doesn’t you can hear some music sometimes in the back ground when I connect a iPad to it but mostly a humm. I want to fix it does anybody know how and where I would start to find the problem I’ve looked at the insides and everything looks good but I’m not a professional so maybe I missed something.

I have for sale a Rega P5 with Neo power supply.
I bought this from a Rega salesman about a year ago.
He added a DIN connector to the base of the RB700 tonearm.
I added the Neo power supply and a Groovemaster Reference sub platter as I didn’t care for the pitch stability. This totally solved it.
I have been a long-time Thorens user and wanted to check out a different setup while I was rebuilding my primary Table.
I collect vintage cartridges so I like a detachable headshell.
I have several new spare belts and the original sub platter.
It has been in my possession for about a year and a half.
Cartridge not included, but I have several available if needed.
Asking $1200 + shipping.
Thanks

Hi folks,

Instead of letting a full width slotted port for reflex / MLTL , do you think it would be a wise idea to divide the slot into sections of smaller width, hence giving it somewhat of a bracing?

Best regards,
Alexander

The Bedini 150 MKII sounds good but has been running for 33 years and it's time for a refresh. I've read around the net and two things came up.

1. upgrade the transistors were from the MJ15024 to MJ21194 - NPN

2. change out the yellow caps hanging off the boards to something much better. I don't know what caps these are and can't find a schematic.

Is there anything else I should do? Thanks in advance for your help.

Trying to work up the courage to build a PLLXO.

LF will be handled by the amplifier which is also has a volume control for level matching. Am I envisioning this correctly? If I got it all right, what do I need to buy?

Thanks in advance.

I'm working on installing an active (solid-state) effects loop in my 1969 Bassman. It was originally AC568, but over the last couple decades it's had some mods (AA864 phase inverter and a 2204-esque preamp on the Bass channel).

I gathered all the information I could get my hands on, and cribbed bits and pieces from different places to come up with the simplest circuit I could manage. It uses an IRF840 for the send buffer, and an LND150 for recovery.

I'm having a devil of a time with oscillation (90-120kHz) and motorboating (~4Hz). The buffer seems to be fine, so the problem appears to be on the recovery side.

I've tried multiple different tweaks along the way, including fixed bias for the LND150, lots of different values for Rs and Rd, lower Rg (down to 47k), high-value gate stoppers (up to 68k), etc. The closest I got to clean was using fixed bias at ~15V, but it still motorboated when the master got above about 7.

It oscillates even with volume, send, and return all turned down. Motorboating starts as soon as the return or send is turned up a little. There are some combinations that don't oscillate; in particular, turning the return all the way up makes it more stable (although there are still plenty of send pot positions that make it freak out again).

Notes:

• Some items have been omitted from the schem for clarity - 12V protective zeners on both MOSFETs, bypass switching
• It's currently built on miniature breadboards. I've left at least one empty row between all connections. They are sitting between the power transformer and the tagboard. Lead dress isn't great, but there aren't big gobs of wire floating around.
• B+ is sourced from the last preamp node. Yes, 220V is super low; the Bass-side preamp flows a lot of current, including the previously-unused triode.
• Voltages are at idle - had to disconnect the return to get there.
• I ran out of 100nF caps, that's why there are 150s in there.

I swear, everything single project I touch oscillates like mad. It's crazy-making. I spent eight hours today trying to resolve this. That's eight hours I would much rather have spent playing. I've easily spent three times as long chasing oscillations than I have doing everything else combined (designing, building, etc.)

I feel like I'm missing something dumb. What is it?

I have for sale a stereo set of the Mark Audio alpair 10,3 Gold, specially produced for the Unmonday company.
The speakers are barely used, like new.

Alpair 10.3 | Markaudio

Unmonday 4.3 | Inner Magazines



140EUR + shipping + paypall

Hi,
I have a pair of Focal Chorus 714S that I got from eBay, both tweeters blown. I know that replacement tweeters would mean redesign of XO, but has anyone attempted this before or know where you can get replacement tweeters, voice coils, diaphragms etc ? Any ideas most welcome! Thanks

Hey there.

I have a Leak 50 stereo that I had originally intended to use for the transformers in a stereo amplification system for an instrument/line level.

I removed the transformers to test them. Both output transform coils all are intact and gave dead on values when I performed an ac voltage inputting test and did the math for impedance ratio to validate that the taps were what they supposed to be - both transformers 4, 8 and 16 ohm taps with a primary impedance of 7,000 ohms. The power supply also measured predictable voltages across its coils - HV, 6.3V and 5V. Of course, they measured a little higher due to the no load condition on the PT.

A poster responded to my thread on this amp with the comment that this amp could be very valuable to someone who was passionate about restoring rare vintage amps, and that I would be equally or better found in using say, the Dynaco replacement transformers as found at Triode Electronics.
After some thought (and a little guilt) I decided that perhaps this would be the way to go. Maybe myself and who ever go their hands on this amp would be much better off in their venture instead of raping a rare vintage amp for its transformers. Don't get me wrong, I was very excited to use the trannies for my next project but, would probably do fine or better with something like the Dynaco replacements.

So, if you are interested, feel free to contact me, you can even call and we could facetime - I could show you the amp and transformers as they are and perform any testing that gives you confidence in the tranny functionality.

Thanks for coming by,
Best,
Philip Donovan
617-470-9821
donovanphillyboy@aol.com