For Sale FS: MC Transformers and Tubes: ECC88 \ 6N23P Reflektor 1975

Up for sale is a couple of Terrapin Audio Cobalt Amorphous core MC Transformers:

mc.jpg


Can be wired as 1:10 \ 1:20 or 1:40

These have been compared favorably to many top MC step up transformers (including TX103)

1:40 is perfect for Ortofon SPU series and other cartridges with low output,

300$ for a pair

===========================


Rare 6N23P Matched Pair of Silver Shield - Holy Grail 75' SWGP Reflector ECC88 6922 E88CC 6DJ8​


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NOS

400$ for the pair


=========================



Svetlana 300B Matched Pair


300b.jpg


NOS in box - 800$


=========================================


6N30P-DR Matched Pair - NOS in Green boxes

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500$

3 Ways Compact Speaker Building Advice

Hello all;
I'm looking for some friendly advice for my speaker building project...
My current and long-time speaker project consist of
Scan Speak 18W/8531G-00 mid-woofer
Dayton RS52AN-8
and 1 tweeter needs to be selected. I'm leaning towards choosing SB Acoustics SB21RDC
Years ago I thought I would pursue an DIY compact 3ways speaker project but II spent a lot of time on jobs after graduating from college, these speakers have been in the storage for a very long time.
Now I have been bitten by the idea of building these speakers once again. Pulling the drivers out of storage, I discovered they are pristine.
After consulting I have 2 ideas as follows:
1. The general design would follow the Tony Gee L'ofeo speaker, which I find quite aesthetically pleasing. It has a volume of about 35l and is designed for SS 18Wu but I will edit to reduce the volume to about 30-32l by reducing the depth a bit to suitable for SS 18W8531. The tweeter will be mounted on top of cabinet.

2. cabinet designed based on troels Gravesen SP44. tweeter and mid will use driver i choose.
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Since I lacked the requisite knowledge and experience measuring to design my own crossovers. but i already have behringer ecm 8000 and i can learn gradually. I can also use CNC service very close to home to quickly have a cabinet
I’m looking for suggestions can make any kind of informed decision.
Much thanks

NE5532 preamp questions.

First here is the schematic.
Next here is the output

Questions.
1. With zero input and scope on output pins I see a huge voltage output off 20v peak to peak. The second I put any load across the output (Ear phones). The voltage drops to zero. What kind of load should be put across the output so I can test ?. A friend told me not to put any load. Another said 1K. Another said ear phones are ok. Is it normal for the output to behave like this with no load ?.

2. Playing with the gain control I can get a range of output.
Upstream of this pre-amp and tone control board I have a TDA7294 amp and also a LM3886 (Separate projects same pre amp). , So what voltage should I feed the upstream AMP ?. We tried feeding the amp a signal from my phone direct and the output was very disappointing. I read the data sheet for the TDA and LM multiple times but nowhere could I find a recommended input voltage. Am I blind / stupid or they expect you to know this ?.

3. Any ideas to improve or tweak this circuit ?. (Yes I know its an old design from the 50s.).
4. What could be causing the distortion on channel 2. (Blue line).
5. What is the safe upper limit on the input signal of this circuit. Various items will be hooked up to this input from CD/Bluetooth/Phone jack/MP3 player/Turn table
6. The bass and treble introduce a gain off upto 15 DB. How do I limit this to say only 6 DB.
output.jpg

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Looking for a 12" or larger Pro Audio Subwoofer, for small sealed enclosure?

Hey, I'm searching for low frequency/ subwoofer driver for an ongoing floor standing speaker project.

I currently am testing out a 12" driver with a matching passive radiator ( DSA315-8 + DSA315-PR from Parts Express). They were the first thing I tried, and they do the job without any performance issues. SPL is more than adequate, distortion is low, extends lower than I need in 45 liter cabinet, etc.

Why do I want different drivers if these are working? Using the passive radiators was a compromise I made early on, but I'm questioning if that was necessary. I would like this woofer to be sealed. Also, I'm a little suspicious of being a rookie at this and having my first impulse turn out to be the best solution. And I'm not entirely happy with the build quality and aesthetics of the drivers.

My critera is:

12" or bigger
-F3 of ~45hz, and up to ~200hz in less than 75 liters sealed cabinet
-looks like a pro audio woofer, so not a high excursion subwoofer.
-max price up to maybe $300 each?
-power handling is irrelevent, but I guess 200+ watts.
-looks ok next to my coaxial drivers, which are B&C 12FHX76


The only driver I found in my price range that is a pro audio woofer and has an F3 of ~45hz in 75 liters (sealed) is the Eminence Lab 12 woofer.
https://www.parts-express.com/Eminence-LAB-12-Professional-12-Subwoofer-Speaker-290-570

Workshop Co-ax Mini Bangers - B&C 5CXN44

Hi all!

I've just got my workshop going in my garden which is pretty small (3.5x3.5m) ad have been relying on an Echo Dot for audio and it's been getting on my nerves. So, before I get stuck in to my other 2-way I need to sort this out.

- Needs to be small
- Needs to be tough
- Needs to have a grille to keep dust at bay (valchromat dust is the worst)
- DSP / Class D

A while back I saw Scott Hinsons great speaker project using the B&C 5CXN44 and it looked really interesting. Rather than just make Scotts design I thought I'd start from the ground up and make them to my spec which is a particular heigh/wwidth to fit on my workshop shelf. Well... it turns out speakers end up looking kinda the same when you only have one driver. I majorly copied his vent assembly though. The shame.

I did some sims as an 8L cabinet, knocked up a cheap and nasty cabinet and did some measurements. Then put some offcuts in the cabinet to reduce it 7.5L and cut the pipe tuning to around 55hz. Added 45g of poly stuffing. I'm happy with the roll off in the low end but my finished cabinets will be closer to 7L to tighten it all up a bit.

My mate brought me round some offcuts of black valchromat so I thought I'd use this but the 19mm board he brought round was knackered. I laminated some 6mm MRMDF and some of the 10mm he gave me and started dimensioning it up. I'm rather route- table-happy at the moment so I routed a dado groove for some stretchers all around the inside of the cabinet to help with alignment and panel stiffness. The panels are rebate jointed. And this is where I am with the project.

I'll update as and when.

Cheers!

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Polishing a Pearl?

Hi Everyone
Years ago, I built 3 of Waynes wonderfull Pearl phonostages - the original one. One for myself, and two for good buddies of mine. Alle are enjoyed greatly to this day. But I came to think if there was anything that could be done to improve them? I remember years ago there were a "Top 10 ways to better an Aleph" kind of thread, just for the Pearl?

I don't really need the Pearl 2 as I have an excellent SUT for my MC cartridge, and they look to fairly similar in parts? Anyone built both and compared thoroughly?

But the PSU in Pearl 2 is more "advanced" and also incorporates more info on grounding - would this be a benefit? Also, the BA2018 linestage PSU is an example of more RC-joints in the PSU, would this be worth exploring? Are there better parts for the JFETS than the ones originally used (probably not as they were the "right" Toshiba parts)?

Best regards
Hans

Adcom GFA 555 MK II Restoration project

Im a longtime lurker here, thought id share this GFA 555 II Im working on. Right off the bat I want to thank Mr Hoppe, at Hoppes Brain for his fantastic posts about these amps, with high resolution pictures so i could copy his fantastic work. I could not have done any of this without him.

Ok, so obviously step one is to purchase an amp. I bought this off reverb. It was owned nearly its whole life by an older gentleman in florida who sold it to the guy I bought it from. Still in good working condition, although im pretty sure I could hear some artifacts in the left channel on occasion.
received_1452287525254622.jpeg


Step 2, collect parts. I ordered an input board from hoppes brain, and replacement bypass caps and resistors for the filter caps and output boards. Misc pieces were obtained locally, like the distribution block, thermal goo, power cord, etc.

Step 3 . I chose to work on each piece as i accessed it, rather than tearing the whole amp down at once. First, I installed the new bypass caps and built the input pcb.
IMG_20221022_221138257_HDR.jpg
IMG_20221022_220023903.jpg


Tip: I used water soluble flux on each component and about 770°f soldering iron. I have never used anything other than flux core solder, and this was a game changer. You just tap each component and they suck up the solder. Assembling the pcb was a breeze thanks to that and the nice documentation by Hoppe.
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SONY CDP-307ESD cracked sound

Hello everyone.
I have Sony CDP-307ESD but unfortunately it doesn't work.
2 repairmens said the Dac chip is broken and original TDA1541 chip is hard to find.
Just to be sure, I wanted to get the opinion of experienced friends here.
If the problem is in the dac chip the device will to scrap.
The sound does not come from the cd mechanism, it comes from the cd analog output over the speakers of the amp.
Video

Thank you.

Yamaha B2 restoration recap service kit fix repair capacitor from HiFiAudio?

Anyone have experience with this seller or this kit?
https://www.ebay.com/itm/165635785959
https://reverb.com/item/59396238-yamaha-b2-restoration-kit-filter-capacitor-repair-rebuild-fix

I have built 2 of the ACA and thinking about challenging myself with recapping my Yamaha B-2 myself. Why? In low volumes, the music sometimes jumps from 1 channel to the other. At medium to high volumes, I sometimes get distortion on 1 channel. I haven't been able to locate a technician I would trust within a reasonable distance so I am just guessing that this may fix my issue. For $140 and some of my time, I figure it's worth the gamble. Hopefully I am not totally off and just throwing my money and time down the drain.

Shading/filtering on a 5 coil planar tweeter (group delay ?)

Hi there, i have build a small planar driver 5.8cm wide x 22cm high, with 5 coils on them the middle being the tweeter, and flanked above and under by the same coils in parallel (next time io do them in series) and above and under those 2 are another 2 coils also in parallel.
i used caps in parallel with the coils i want to have a roll off, so it adds to the lower end but does not hinder the dispersion of the high frequencies to much.
here a schematic of the thing made up in Xsim. and how the roll off looks like and the group delay. (since i wonder if i need to concern myself about that)

1667262391400.png

1667262445801.png

1667262509447.png

They are crossed at the moment around 600 hz (should be higher but at my volume it works fine)
it greatly increased vertical dispersion, but to my ear it sounds great but maybe a bit to spacious >? i have trouble getting a rock solid phantom center in my room for ages, so i am not sure if i am hearing now a problem with phase because of this setup ? or delay ? or just my room. (normally i have more lines source like tweeters, so copuld also be this more point source style gives much more room troubles) does anyone know if the group delay as shown above is problematic ? i did measure this contraption vs a bare panel without any filtering and they both measure in rew gated almost exactly the same group delay even without crossover below 800 hz or so it rises. (my back wall starting to play up >?)BY the way how can the tweeter be a negative delay ?.....

here a rather badly taken picture of one of the shitty looking things, its just an illustration 🙂 by now the bass drivers are under and above the tweeter. sounds better!
1667262967968.png
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custom toroidal for low voltage AC input

Hi,

I'm in a quest to avoid mains into my preamp and dac chassis. I just thought I might buy a custom wound toroidal for 24V AC primary.
The power would come from a AC-AC wall wart, like this or this so, for instance, windings would be primary 0-24V, secondary 2* 0-9V and 2* 0-18V

First of all, is it even doable? I've never seen this mentioned as an option, and I've read several threads in this forum.

Thank you

Hi-Vi Swans D6.8 Bass/Mids

Hi Guys,

I have 2 pairs brand new and boxed Hi-Vi D6.8 woofers I'd like to move on.

These are a very nice 6.8" driver that reach deep in a reasonably small cabinet and have incredible power handling thanks to the 4" (yes four inch!) voice voil. They reach cleanly to about 3KHz making them great for a 2-way (see Totem audio 😉 )

Currently £130 pair new. I'm asking £50 per pair + delivery.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.

FS Swans/Hi-Vi D6.8 6.5" and Philips AD7066-W8 6.5" woofer pairs

For sale:

One pair, Hi-Vi D6.8 6.5" high-end woofers. Very similar construction to Dynaudio 17W75XL. Specs here:

Overview D6.8 Bass-Midrange_HiVi, Inc.

In great shape- virtually like new, never installed, $80.00 for the pair, plus shipping.

One pair Philips AD7066.W8 6.5" vintage woofers. Specs here>

http://www.verheijde.net/library/Philips_1978-10_CM3b_Loudspeakers_939810550011.pdf

In great shape. $70.00 for the pair, plus shipping.

I don't have Paypal- I usually work with USPS money orders. Located in Kennesaw GA. Local pickup possible- can probably meet anywhere within Cobb County GA or close nearby. USA shipping only.

Thanks!

Regards,
Gordon.

Yamaha C4 preamp.

Had just buttoned up the amp after the latest repairs. Switched on power and there was a snappy spark sound near to the power switch, the amp didn’t start working and mains power was immediately switched off at the wall plug. No magic smoke occurred.

Looking inside I can see that the blue lead connected to the power switch has perished/disconnected from the switch. It was just resting on the pcb below.

Have now reconnected it. Powered on again at the wall mains plug with the C4's power switch in the 'On' position but again no response.

Fuses fine. No visibly damaged components.

How to proceed and what to check or replace?
How does one go about testing a reed relay? There's a RL 6442 (RY301) which I'd like to test but don't know how to.

Converting Hammond LR A (ex HR-40) to Hifi Mono Amp

Dear All,

i am planning to convert 2 Hammond LR A (from a HR-40 cabinet) into Hifi Mono Tube Amps.

I decided to use this AMP since it has an internal 200Hz (cycle) crossover which fits nearly to my Eminent LFT-8 speakers (180Hz cossover).
So I could use the L speaker out for the LFT-8 Bass and the H Speaker out for the other.

As afr as I understand, there is not such a lot to be modified in the LR A when used as Hifi Amp (in minimum)
- connect pin 3 and 4 (of the 6pin plug) to 110V AC
- connect audio out (signal) of preamp to pin 6 and 1 (of the 6pin plug) and to ground respectively

On an other forum (can't remember which one) I found the following information for the audio in for Hammond amps:
- solder 2 200ohm resistors in series
- solder them between audio in hot and cold
- additionally connect the two ends to pin 1 (signal) and pin 6 (signal)
- soldering point between the two resistors is connected to the ground of the tube amp
(see attached pdf file)

can anybody tell what this cirquit is worth for?

According to the information of Hammond, pin 1 and 6 are both signal inputs for the amp (no ground inputs). And since the amp is a mono amp, I would guess to connect them together to the hot out of the preamp...

any proposals from the professionals side?

Best regards from Switzerland, Thomas

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diyinhk Store

All DAC convert SPDIF to I2S signal before decode.
Everybody know I2S is far better than using one more SPDIF layer

There are many semi-solution to avoid the unlock problem of the best DAC chip ES9018 from I2S input, including changing the DPLL setting but the trade out is lower jitter rejection, use metal shielding cover the DAC chip, use super high quality clock, or use SPDIF input. All method either reduces the sound quality or the unlock problem still exist.

This 24bit 192khz USB to I2S PCB is tested with I2S input to ES9018 with NO unlock problem(default power on setting, default dpll setting, no need metal shielding cover the dac chip, no need to wait for the lock to become stable after power on)

This solution uses 49.152Mhz/45.158Mhz oscillator and it should be better than the original XMOS and other design uses only 24.576Mhz and 11.2896Mhz oscillator

Welcome to comment!

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Very short digital (S/PDIF, RCA) interconnects.

(Admin, feel free to move this to the relevant section in case I’ve incorrectly placed it, as it could be in three different sections.)


This is not really a DIY as I unable to DIY these cables. However, this is just to get the info out there.


When I purchased my Denon D-F109DAB system (receiver, CD player, network player) in 2013, I also purchased Atlas Cable’s, “Compass”, 75ohm interconnect cable, with their Achromatic RCA plugs (S/PDIF), in both 0.75m & 0.5m long. This to connect the RCA digital outputs of the CD player & the network player to the RCA digital inputs on the main receiver/amp/DAC. (Yes, I know these terminations are not as good as BNC, but I have no choice in the matter)

However, I have never been happy with the length of them as they are too long for my situation, even though they were the shortest I could find at the time at a reasonable price. Then there is the issue of “jitter” where it is considered better to have interconnects 1.5m long or circa 0.3m in length to lessen the amount that jitter can occur.

I looked at DIY making two short cables by chopping the longer 0.75m cable in half. However, after dismantling one connector I found that the centre pin is cold crimped onto the main central core! Also, their Achromatic RCA plugs are low mass versions which I haven’t seen available as separate items.

So, I contacted Atlas, who are in the same country as me, & asked if they could chop the cable in half, fit new Achromatic RCA plugs to the two new bare ends, & if they could remove the two existing outer covers/sleeves & fit the new red ones to make all the plugs match. They said they could & the price would be about the cost of one new 0.5m long “Element” cable with Achromatic RCA plugs. Apparently, my Compass model is worth keeping as not as “basic” as I thought, as it sits between the entry level Element & the mid-level Hyper cables, with the Hyper cables costing at least £114 for a single 0.5m length with Achromatic RCA plugs!

Anyway, a couple of weeks after sending them my single 0.75m cable I received two short cables with all red plugs as requested, & as you can see, a much better fit for my situation!

Now the million-dollar question:- “does it sound better?”

The only noticeable difference, to my ears, is that in sections of music which have a lot going on, i.e., loads of different instruments playing at the same time, or rapid changes in tempo etc., the music “flows” subtlety smoother than before.

Photos of before & after….

Atlas-cables-B-and-A.jpg

NE5534 LTspiceIV models

hello, attached you will find three different NE5534 models to be used with LTspiceIV. The _h1 model tries to be the most accurate with the differential input pair non-linearities, VAS slew-rate limitation, output stage non-linearities and output current limitation. The _h2 model is a simplification exhibiting a very wide bandwith, no slew-rate limitation and less THD than a real NE5534. The _h3 model is a near-ideal opamp introducing the smallest THD. See attached .zip. Those three models are compatible with the Kuroda topology and the Floating Supply Bridge topology. The behaviour of the supply pins is exact. Internally, the three models don't use any grounded reference.
Once you understand the method, you can adapt the models to other opamps.
Use more bias current in the VAS, increase the DC gain, decrease the compensation capacitor, ...
Replacing the BJT differential input stage by a NFET or a PFET differential input stage in the _h1 model is also possible, for simulating FET audio opamps.

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JAN GE 6072A Tubes

Nice quartet
I have 4 pcs. of JAN GE 6072A tubes left over from a project 30 years ago. They have been stored in a dry place in room temperature since then.
I could sell them as a quartet or as pairs.

Tube 1 and 2 are 100% NOS and come in the original boxes they were delivered in. Never used. Matched pair.

Tube 3 and 4 were bought as NOS at the same time, but they were used for approx. 20 hours in a linestage. I am quite sure that these two tubes are a matched pair as well, but I do not have a tube tester to verify. I do not have the original boxes for these two tubes.

Total for all the tubes are $279,-. Prices have went through the roof, so this should be quite reasonable.
Shipping world wide with tracking is $35. I will pack to withstand a nearfield nuclear blast, so the package will be too large to ship at letter rate.
Payment via Paypal.

Please, feel free to pm me or shoot an email to info @ whistleraudio . com.

Happy diying. 🙂





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Waveguide adapter for XT25 and WG300, any interest?

Hello everyone,

After having received my XT25TG30 tweeters and Monacor WG300 waveguides, I started thinking about how to put the two together. I figured that an adapter flange would be the nicest way to do this, so I took my tweeters apart, measured them, and drew a flange in Freecad. I have attached two views of this flange.

Because the unit cost of CNC manufactured things goes down as numbers increase, I was wondering if more people than just me would like to have such a flange. If so, I could try to find a manufacturer and initiate a group buy.

Please do not PM me, but reply to this thread. Also, if you happen to know a manufacturer with good prices (preferably in the EU), let me know!

Cheers!

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Crescendo 17k

The guy that I’ve already repaired 2 of these amps for has another one .

The 3rd amp he has never had it repaired .

He bought a cheap oscilloscope off eBay to set the gains on these amps

He had the amp powered on and touched the positive lead to the posit r speaker terminal and then went to touch the ground lead to the negative speaker terminal and as soon as he did it blew the outputs .

What would cause the amp to blow the outputs ?
Also is there a way of avoiding this in the future if he uses the scope again to set the gains like level matching

choice of sound card for measurements and DACs

hello, can you help me choose? .
I would like to buy a sound card in the second-hand market to save money.
its use is twofold:
microphone speaker measurements is the first function.
when I am not taking measurements its function is that of the DAC converter connected to the digital outputs of an audio player without a computer (I would also like to try the DSP to equalize). consequently the outputs of the sound card will go to a pair of speakers.
I would like a good quality of mic preamps, DACs and ADCs.
I don't want to penalize the sound card for prioritizing the type of connection that goes to the computer (USB, firewire, Thunderbolt).
besides USB2 I have a PCMCIA and expresscard port. i can always buy a converter
Hello and thanks

Inverted triode DC heater elevation.

Hello, People.

I am making a hybrid headphone amplifier, for 60-600ohm headphones, using subminiature tubes with mu of 25 (planning to use "real" grounded grid amp), followed by solid state output stage (impedance multiplier circuit with LT1206 opamps).

While 600ohm headphones make use of the extra voltage gain, 60ohm ones are reaching high levels already with output from DAP I am using, at 60% of volume.

While I am still waiting for various parts to be delivered, I experimented with the "inverted triode" circuit, which has gain of approx 1/mu. It worked, and I figured out I could use it as "attentuator stage" after grounded grid stage for low impedance loads. (A switch would be used to select "Grounded grid -> IMC" or "Grounded grid -> inverted triode -> IMC".

I would like to use the same heater PSU for both grounded grid and inverted triode, which is elevated to 1/4 of B+.

But does the same principum of cathode - heater voltage apply to inverted triode, or would it now be heater - grid voltage?

Thanks in advance.

Error simulating passive radiator in WINISD

I’ve simulated in WinISD a 11 liter speaker box with a SB acoustics sb15sfcr39-4 and a passive radiator similar to the woofer but without the magnet, it has exactly the same Sd and Xmax.
I’ve readed in many sites that for a 8” woofer do you need two 8” passive radiator but in my simulation i get better result with only one passive radiator, is this possible?

NAD 705 with DC voltage on one channel

Hi experts!

Being a novis in amplifier repairs I just have to say this forum is absolutely fantastic! This is my first post ever but I have spent numerous hours to try and learn from the best. Last year I built an F6. That was so much fun and I learned a lot. Anyway, i’ve been working on an old Nad 705 amplifier that has DC voltage on the left channel and this causes the amplifier to go into protective mode and the speaker relays to open.

Right channel is ok.
I have tried to illustrate the situation on the schematic of the left channel. The blue lines indicates +8.9v to +10v. On the other channel the voltages are as the schematic shows. Between +1.2v and -1v

Is there someone that have the knowledge to point me in a direction to where the DC is coming from I would be so thankful since I’m running out of options over here 🙂
I have tested all transistors Q101,Q103,Q105,Q107,Q109,Q111,Q113,Q115 with a multimeter and a "T7 Multi function tester". Tested all resistors in this area and checked the caps for shortages (in circuit)

I have replaced C123 just to be sure.

No visual indications of heat or other distress on PCB or components.

Should i maybe replace all electrolytic caps?

Enclosing the service manual for the 705 for reference
I also found this thread from 2020 explaining almost the exact issue I have just with little higher dc voltage.
https://www.diyaudio.com/community/threads/nad-705-in-protection.356159/

I am using a light bulb current limiter when taking voltage measurements

Best regards,

Daniel E

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Finding saved drafts when posting new thread

Hi,

I am new here, trying to post a thread and saved it as a draft. However, returning to it at a later point, I cannot find where I could restore or find the saved draft. When posting a new thread I only see the option to either "Save draft" or "Delete draft".

Where may I find my saved drafts then?

Thanks in advance and kind Regards,
Martin

Crown XLI 1500 vs Behringer KM 1700

Which amplifier would you choose between Crown XLI 1500 and Behringer KM 1700?
Crown XLI 1500 delivers the power stated by the manufacturer and also has some more power reserve.
Behringer KM 1700 specifications only mention a max power rating (peak) and Behringer states that the expected continous power rating should be about half the declared max power rating, so one never knows for sure exactly how much power can deliver continuously into the given load.
Construction wise, Crown XLI 1500 seems to be a class A amplifier with chinese made toroidal transformer (Guangdong NRE Technology) and 4 capacitors of 63V/10000 uF.
Behringer KM 1700 is declared to be a class H amplifier and, as far as I know, it may use the same Chinese suplier for the toroidal transformer (Guangdong NRE Technology) and use 4 capacitors of 63V/10000uF also.
Is there any room for modifications on any of these two amplifiers to improve their performance and reliability?
Thank you kindly!

Tekton Perfect Set. Thoughts?

Since the beginning of Tekton's new array/matrix drivers, using 6 tweeters as mid surround 1 tweeter, there were alot of people discarding this as gimmick/insanity.
I was one of them. And now I have a Perfect Set at home, I can hear/understand the logic behind it.

The mid is truly one of the fastest I've heard. And the imaging (governed by the mid+high) is unbelievable. Its slightly less solid than the best 5 figures fullranger (heard from audio show, I never own them), but is way better than a traditional 2/2.5/3 ways setup.
That's also enhanced by the fact that it can be used with SET tube amp.

If anyone who have heard/auditioned the Tekton Perfect Set (or other tekton multi array models), are there any equivalent speakers out there, custom/manufacture/DIY?

Marantz XLR Pinout Rantz & Internal Wire

Hey Gents, I'm really enjoying the community here reading the many posts. I now have a Marantz SC-11S1 Preamp, and what a fine piece of gear it is.

Having a look, it's first-rate all the way. Highly documented issue, how/why in the world did Marantz swap the XLR pins 2>3, with 3 being hot. I got this beast home, started testing - no magical sound - until I started reading. I modified my cables to accommodate pin-3 being hot, and sure enough magical sound..

It's a bit of a disappointment I have now a 'special' unit requiring special XLR interconnects.. It's not the end of the world, quick mod, but really not free to use any old cable.

And motivations behind it? Marantz to Marantz would work just fine, in phase, pin-3 to pin-3, but start hooking up non-Marantz or XLR>RCA cables, you're listening to inverted phase and it's not usually magical. What a way to throw off buyers. It's also kind of interesting their bi-amp capability, where they propose 2 preamps with 2 power amps, great way to move a lot of expensive boxes!

I am thinking of replacing the internal signal wire to silver, I've attached the service manual and wondering if anyone might have any comment. I've ordered some JST EH style connectors and my plan is to make the internal interconnects as a quick replace / swap - no solder, etc. I'm zoning in on J102, and Tone J601 / J602 - Thinking of leaving the phono alone, as I can't foresee any phono use. What do you guys think? see anything I'm missing, or opinions?

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ADAU1701 possibilities regarding FIR calculation

Hi,
I plan to build a project related to a (long) FIR filter implementation [SPDIF In -> DSP for FIR filtering -> SPDIF Out that will feed a separated DAC chip].

Maybe the FreeDSP boards using the ADAU1701 could be a solution, but I have read in this thread, post#30, as a reply to FIR filter calculation, that:
ADAU1701 works with Rephase out of the box so to speak, limited amount of taps available though <500.

and it is unclear if the 500 Taps limit is due to Rephase, to the ADAU1701 or to the FreeDSP boards ??

I don't plan to work with Rephase, but if the ADAU1701 cannot perform more than 500 Taps in a FIR Filtering, I need to know and identify a more powerful DSP.

Thank you for your reply,

Free DSP All-in-one Arduino connector

Hi,
By reading the documentation on the FreeDSP All-in-one board, I see the pinout of the Arduino connector, fig.22:
Capture.JPG

I am familiar with the Arduino boards, and unless I miss something, I know all these pins except "WP" : the I2C bus (SDA,SCL), +5V, GND, are known, Reset can probably be picked up somewhere on the Arduino, but what is the WP pin ?

Thanks

replacement potentiometer for TDA7297

I am looking for a replacement good quality potentiometer for my modded TDA7297 amp. Must fit on the original board and 50K resistence. I am looking at this on ebay https://www.ebay.com/itm/161972882607?hash=item25b6560caf:g:GB4AAOSwuAVWuVcJ&amdata=enc:AQAHAAAAsIP1zNYVqx9GEzhSgKCnsy7nJIR7jVskGQDCqmI8Ebsbw0SPN3wyQkVG18nTiKpK7L2FDcE6o90SG50+RUgAxCDFzye/w31yigA0BstGB2KemDgxzJeiw78ZvDbfh101vwoWcLYc/G8lELXo3pDB4D1wvUfigvFkNv5glpaERRNIlZ6MO0VWAv0BwOhr0tHQYZjfIInAa2E+1llqj+wZjs5gJOnOj9hOoBn0eIM2sxa6|tkp:Bk9SR4j0qKGFYQ I would prefer a single pot with a good quality, 1. would the pot above work? 2. recommend another of perhaps better quality ?

thanks

GSG Full Marty Classic 21" B&C x 2, Behringer NX6000D, Two Stereo Integrity SQL-12 D2 with boxes.

Looking to sell my GSG Full Marty (classic design) 21" B&C Subs. Finished in 3 coats of black Duratex. with Speakon connectors. Drivers are like new. Very little theater time (plenty of music though).

Asking $old for the pair.

Dimensions:28.50” wide, 23.50” deep, 42.00” tall
(71.8cm x 59.7cm x 106.7cm) assembled

Removed Behringer amp from the listing.

Also have two Stereo Integrity SQL-12 D2 subs in like new condition. Currently installed in Denovo 1 cuft MDF boxes finished in Duratex with Speakons. Have original boxes. Sold with the enclosures, $sold without. No shipping on the Sub/enclosure but would ship the Subs in original shipping boxes at buyers expense.

Local pickup on the subwoofers in Southwest Missouri for the Martys and SQL in the enclosures. For a serious buyer with cash in hand I can meet within a reasonable distance of Springfield MO.

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Substrate (SS) pins on LSK389/489?

Gang,

Asked Linear Systems and no response.

Anyone know what to do with the SS pins (are they tied together, I would imagine so will test) on the LSK389/489 SOIC packages?

I use these in a simple buffer at IDSS on a +/-6V system on a guitar pedal. Yay I know over doing it is my specialty 🙂

Do I ground these, -V, +V or just ignore them?

Thanks,
Gordon

PSU1 with a twist for Miro Ad1862 dac

Have a set of PSU1 designed for Miro AD1862 dac. Output +/-5V and +/-12V. Originally designed with 78xx and 79xx regulator ICs, have replaced them with LT1963 and LT3015. Bought from a fellow member here but have not put it to use. Caps are all Nippon Chemi Con with wima bypass. Schottky diodes. 75usd inclusive of shipping worldwide.

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Damping resistor before or after XO

I've played a bit with Xsim just with dummy drivers, as I don't have concrete measurements. I then made diagrams of different 2-way speakers to see what the components do and the different correction notch that people use. I am aware that the curve I get in Xsim is not the curve the speaker gets as I do not take into account the driver's characteristics. But playing with it has given me a lot of insight I didn't have before.

Often the tweeter has a higher sensitivity than the bass and needs attenuation. I see that some have the resistor before the XO itself and others have it after. But will it depend on the individual situation whether one or the other is an advantage. A filter is shown here. I've put the resistance both before and after the 3rd order filter, to see what it does if it's on "Value" or "short", that's a smart function in Xsim, so I can see the difference in the curves in Xsim.

But is it for impedance reasons that you do one versus the other or why?

Diagramoversigt 725.jpg

sealed mains/subs for light PA: when do thermal issues start?

I am contemplating building a system for "light" PA. For smaller events, indoors, etc I observe that a well-designed vented system is not really being pushed anywhere near its limits.
But that system might also be working for 6 hours straight.

Assume a good-quality 12" PA woofer (with 2.5" VC) and 1" CD/horn, along with 18" subs (with 3" VC) in a 4 cu ft cabinet. Put them in sealed cabinets and play for hours on end.

Around what wattages will these motors start to heat up enough to be a problem?

Will an aluminum panel or fin radiator inset into the cabinet wall achieve any useful heat transfer?

Motu ultralite mkV SE out

I am planning to use a mkV for my crossover and have downloaded the manual. The manual is specific about not shorting the neg out to ground like many diff out systems suggest when driving a SE input. So my question is should I add a Diff->SE converter on the output of the mkV or just use the pos/gnd as the input. The mkV uses the Sabre 2 ESS DAC's which I thought had more distortion if you only used one leg of the output. Conversely, at these performance levels, building a diff->SE converter may cause just as much degradation. Suggestions?

For Sale - DIY Pass B1 Buffer Preamp

I have fairly long, 20 foot, lengths of interconnects to my amplifiers and relatively high, 97dB, efficiency speakers so I was intrigued by the circuit. I built it as much as an excercise as something that could realistically surpass my present preamp. Imagine my shock, as a diehard Tube Head when I auditioned the finished product and found it to be nearly a match for my far more expensive (parts cost) 76 Line Stage. It's so amazingly neutral and tonally balanced from bottom to top with the ability to convey authoritative bass and delicate treble.

My 76 Line Stage is still slightly better and this little wonder is better off with someone who will use it daily. Keep in mind it is totally passive, just a volume control, a switch for the two inputs, and the low voltage elctronic buffer that makes the magic. It is not recommended for those with less than highly efficient or difficult to drive speakers.

The build includes Clarity CSA output capacitors, PTFE insulated wiring, Vampire CmHex RCA's, and a 100k PEC KKA series pot. Included is the way above average Meanwell 24 Volt SMPS power supply and a custom high frequency filter for it (the small PCB shown). Link to my all DIY system https://cgi.audioasylum.com/systems/12417.html

My cost of parts is $330 including the nice but not lovely Hammond box and I would like to get $325 including shipping to the lower 48. Payment is by US Postal Money Order only.

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Goto driver system

Here for sell a very rare Goto Unit system located in Italy. It is four ways horn system. Starting from the tweeters they are SG-16 BL , the mid-high are SG-370 with the original SG-600B horns, the mid-low are SG-505 DX with original SG-150B horns. They are state of the art horn drivers, very heavy, and big. Paired with those drivers there are the basshorns they are made of plywood on Goto Unit design with two 15" RCF woofers each. It is possible to buy only the three ways Goto. Asked price €. 12.000

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list of tannoy speakers... mid 60s

Do you know where I can find a list of Tannoy home speakers made in the 60s?

This last weekend I heard a pair of mid 60s Tannoys that left me speechless. The guy was playing a Jadis integrated amp, low power and he played a CD of female singers.

It floored me.

Now then, I've been looking into a high efficiency speaker and those Tannoys would fit the bill but I have no clue how much they would cost. The fellow said the name but I plum forget. Of course he won't sell those, they are his private stash... I asked.

The speakers were homely... walnut, old style burlap like grill. a little over 2 feet tall, about 1 1/2 wide and foot deep. The grill came out with a brass key! The baffle was finished with cork. The drivers were coax... 10 or 12 inch with a tweeter in the middle. I don't remember if it was ported.

Just standing six feet in front of them, in a old office in an old building filled with all kinds of sumptuous components in various states of repair ( High End repair shop in West LA ), I felt like dancing. These are seriously good sounding speakers.

They sounded LIKE MUSIC.

I wonder if I can afford them.. but first, I need to figure out what they're called. If I can find on online list I can likely find them, if not I'll have to call that fellow again.

For Sale Caddock MP915-0.20R-1% thick film resistors

I have 26 pieces Caddock MP915-0.20R-1% thick film resistors without use .
I’m asking for 26pieces €40.

Power Rating: 15W with Heatsink / without Heatsink 1,25W
  • Product Range: CADDOCK - MP915 Series
  • Resistance: 0.20ohm
  • Resistance Tolerance: ± 1%
  • Resistor Case Style: TO-126
  • Resistor Element Material: Metal Film
  • SVHC: 03-Aug-2001
Price + PayPal 4% + register shipping expenses.

Shipping form Finland

Rgds
Finwbu

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MULLARD 3-3

Hello guys! I built the Mullard 3-3 according to the original Mullard schematic.

I have 2 problems:
The R15 resistor (after the EZ81) gets very hot, a 2W type 330Ohm isn't lasting very long. a 5W 330Ohm resistor gets very hot.
Second and frightening problem: The mains transformer is vibrating. This vibrations causes hum to hear coming from the speakers and you can feel the hum!!
Caused by too much current flow? The amp sound great but you can hear the mains transformer humming and vibrating.

I use a transformer kit from primary windings (UK).
I use this mains transformer : https://primarywindings.com/product/mullard-5-10-mono-mains-transformer/

Cabinet wall vibration in relation to internal pressure of loudspeaker - Questions

I am trying to understand the difference, if any, of cabinet vibration at the 1st modes (first breathing modes of loudspeaker cabinet resonance) if it is within the pressure frequency region. For a smaller cabinet the frequency band-width where sound acts in pressure mode is wider. So if the first resonant modes fall in this region is more of the energy (back wave of driver) transferred to the vibrating cabinet walls than if this first resonance was further up and passed the pressure zone? I guess this question would be similar to the concept Room Gain/Car Gain and if there is an effect caused by the walls/doors/panels of the room/car vibrating at frequencies where room/car gain comes into play. What would the consequences be?

Now to complicate things what if we also have a port/passive radiator present (open window, or car door to the outside).

What I have read is that if a port is present on a cabinet, lets say tuned to 50hz, there is only a depressurisation of the cabinet at frequencies up to twice the tuning frequency. So past 100hz (and if the loudspeaker is small enough) pressure is maintained above said frequency. So if a cabinet had its first mode below the 100hz, lets say 80hz, it could affect the port output. I would assume it would act like another mass spring system (another port)? Would the presence of the port mitigate the cabinet vibration so that it is less prevalent than if no port was present?


Any insights would be helpful.
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  • Locked
Masking

It's almost fashionable to complain about wearing a mask. But the fact is, I haven't had a singe instance of cold or flu symptoms since Covid appeared and I started wearing a mask in public places. That is unprecendented.
If I had previously known this would be the case, I would have started wearing one much earlier.
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Dual Opposed 10s (or 12’s) in 16” cubed box.

I’ve been thinking about new subs for my modest townhouse home theatre and came across the SVS 3000 micro. By all accounts a fantastic sub woofer, producing deep clean bass. All from <11 cubed with dual opposed 8” woofers!
But it comes at a steep fiscal cost!

So, I was wondering if anyone knew of (or could help with) a design that is modest in size, deep in extension and compromised in maximum output?

I don’t need 115dB of 20hz output, I live in a townhouse and share a wall with a neighbour (like a lot of people do!), but I do want clean articulate bass with a bit of rumble on demand for movies and music.

I don’t know where to begin in designing this ( what T/S parameters to look for) so if anyone could even suggest drivers or specs to search for it’d be appreciated!

Design goal:
16” cubed enclosure (external)
<25hz response
Reasonable SPL & power handling ability
Affordable

I’d love to hear your thoughts or suggestions?
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Driver Placement Relative to Port in a Bass Reflex

Hi all,

A simple question for discussion. Mainly looking for measurements or some links that explain it technically, but happy to hear user experience too:

Does the driver placement relative to the port in a bass reflex enclosure matter?

To further clarify, I'm wondering if the vent pole of a driver is near the entrance aperture of the port internally, if it matters, or if it needs to be as far away on the port side, or far away opposite the port side (the most indirect pathway for airflow) and if so, why? If it does have a negative impact, is it only on paper or does it manifest audibly? Let's assume the port is sufficiently large to not create noise from excessive air velocities, say, over 18 meters per second or similar for argument. Lastly, does it change with the frequency (ie, does it matter or is it different from say 17hz vs 25hz just as examples)?

Very best,

A-B Testing, L-R Testing, a new old methodology?

(First I'd like to re-post to the Lounge a highly relevant 🙄 self-test from https://www.diyaudio.com/community/...e-crossfeed-stereo-sound.391630/#post-7160131 )

Everyone please join a fun psychoacoustics experiment.

While listening to music:
o Close both eyes, sound becomes clearer, fuller, more delineated and organic (i.e. "BETTER"), in particular bass sounds louder; YES/NO?
o Open both eyes, instruments (individual or section) are more precisely imaged/located (especially how far from you), compared to eyes-closed; YES/NO?
(Now the fun part)
o Close left eye and open right eye, the left half soundstage is more precise, but the right half sounds BETTER; YES/NO? Of course
o Close right eye and open left eye, the right half soundstage is more precise, but the left half sounds BETTER. YES/NO?
Please respond with your results!

Now, if you agree with me (YES/YES/YES/YES), the question is WHY? (My hypothesis/explanation to be posted later.)

As for relevance, any listening test (including by oneself) must ensure the testers are consistent eye-wise. And there's a natural extension to A-B testing, or rather L-R testing!

Proton 300 Radio replacement woofer?

I'm a fan of these beefy radios. I've discovered that the woofers frequently fail at even moderate volume when playing bass notes. Maybe age, maybe abuse?

The speakers crack up and distort. Cones look OK and reproduce fine at low volume.

Is there any repair?

I'm looking for a drop-in replacement on Parts Express, etc. Their customer service said very unlikely and suggest I go thru their options and modify mounting holes, etc. as needed.

Any experience on this forum?

dizmayed

Tannoy K3809 - hardened cloth surround issue - solved

I'm lazy , so there are excerpts from my correspondence on Tannoy Yahoo group; all quotes - Mighty ZM :clown:

I'm putting this here as future reference for some other desperate Tanner ; I must admit ( or I'm just boasting ) - I'm always having serius backup for all things speakers - from Aleksandar RAAL ....... even if I'm always stubborn and I'm bugging him only post hoc ..... to be sure that I didn't blew something :rofl:

K3809 - cloth surround impregnation solvent ?

as I wrote - pair of K3809

cloth surround , no back cone ribs
Fs is high - around 70Hz on both drivers
I contacted Tannoy Support , but they can't help - all they can recommend is
reconing , which is out of possibility , counting on fact that drivers are in
excellent condition and just slightly used (well - same as they aren't used at
all )

so - anyone having real life experience , regarding solvent for surround
impregnation ?

whatever , guy at Hasling Audio Systems Denmark is doing exactly the same for SH
Altec's , so I think same is possible for Tanns

TIA

Tnx for reply ;

There is no particular info on Altec related link , but point was that planned
procedure was implemented ...... I sent e-mail to Danish guy , asking for his
recipe , if nothing else , as starting point .

Whatever - K3808 (3809) are having impregnated cloth surround , not paper ;
that's visible on many pictures on net , and "cloth surround" is having exactly
that name in related info

In any case , if I succeed in "operation" , I'll share my findings

of course - "Danish guy " wasn't prepared to share his recipe ; I don't blame him 😉
that's why I'm sharing mine :rofl:

besides Sam R's problem with teared surround ......... and strictly speaking of hardened cloth surround - I'm stubborn and there is no way I'm going to change them .....

I would go to generic soft (probably acquired from Sonido guys in Hungary )
cloth surround , but will ever never invest money in new cones or - God forbid!
- neoprene surrounds 😉

I remember some guys at Diyaudio speaking of
2-Butoxyethanol - Wikipedia, the free encyclopedia
so I plan to start with that

Hardened cloth surround problem solved !!
soaking both sides of surround , using small brush , with plain Ethanol 95-96% ,
brought Fs from 71Hz to 29Hz .

I'm expecting that Fs will rise to spec. 35Hz , when solvent evaporate
That's what we are calling just Pure Alcohol , and you can buy it in every
drugstore.
So much speaking of recone and surround replacement 😉

I'll keep you informed , of course ;

even in case that Fs start rising again , I'll just repeat procedure , removing
old impregnation as much I can , and brush new tacky layer above it

then it will permanent solution

no damage , certainly ;

I'll post few pics in few days , after having definitive conclusion about
longevity of cure

Update : after 24h rest and solvent evaporated - two steps forward , one step back 😉

steps forward are :
1 - impregnate is not brittle and cracked (inducing noise , especially
detectable at Fs)
2 - everything looks just nice , almost as new

step back - Fs is back on 71Hz 😉)

whatever , I'll proceed with more cleaning of old impregnate , and then try to
seal it with tacky surround goo , which will (hopefully) prevent repeated
hardening

will keep you informed

OK

K3809 - cloth surround impregnation solvent ; hardened cloth surround - high Fs
- issue SOLVED

procedure finished and confirmed
after 24h (and more ) of solvents evaporating , Fs is still good : 33-35Hz

RECIPE

what you need :

1.small brush , semi hard m ~8mm wide , same as kids are using for painting in
school
2.Ethanol 95% (pure alcohol)
3.Acetone with oil ( nothing else than nail polish remover )
4.mouse glue (yes , that organic everlasting sticky goo)
5.Vaseline
6.cotton cloth ( old T shirt or whatever)

brush - buy it anywhere , mouse glue - anywhere , everything else - nearest drugstore

important to say - surround was originally threated from upper side , mostly ;

just slight residue of original rubbery impregnate is visible from bottom side
of surround

procedure for upper side of surround:

using brush - from upper side - soak surround with ethanol ; it's best to soak
it in parcels of 10cm , then rub it with same brush ; whenever you fill brush
with residue , wipe it on cloth

repeat procedure until you make two full circles (so entire surround perimeter
is twice treated)

move to second speaker ,same procedure , again two circles ;

repeat same soak-rub-wipe-soak-rub-wipe procedure on both speakers , until you can see clear fabric of cloth , without any trace of rubber

it's fun , but only if you have some muzak and coffee 😉

after few steps in procedure you'll see what's happening ; if you think that
you'll gain anything with another soak-rub-wipe circle , just do it

leave speakers 12h , to let Ethanol to evaporate

now - put some mouse glue on small (coffee cup) plate , add acetone and dissolve it to something liquid as milk

using brush - put that mixture on upper side of surround ; if you see that your
mixture on plate is going firmer , add acetone and mix ; when you treat entire
surround , take just acetone with brush and treat entire ( already impregnated )
area with it , to make it more uniform

leave it for 12h

now - bottom side of surround :

soak brush in acetone , rub it firmly in Vaseline , then put that mixture on
entire bottom side area ; goal is to have tiny layer of vaseline on bottom side

leave it 12h

measure Fs

easiest way of measuring Fs - use sine signal generator with 50R output
impedance , connect it to bass terminals , put CRO probes on terminals

sweep frequency from 100Hz down ; when you see biggest sine amplitude , there is Fs

another possibility for measuring - instead of sig gene - use Sig Jenny program
( wave gene with counter ) , sound card to small amp , amp to bass terminals ,
AC voltmeter to terminals

put few volts of sine to bass , sweep from 100Hz down , when you see biggest
reading on Vac meter , that is it

mine are at 31 and 33 Hz , I'm not loosing sleep because of using mouse glue and
vaseline on piece of cloth 😉



then one guy is saying that Mouse Glue is forbidden in some EU countries ; my reply :


in that case - just buy softest surround impregnation goop ; easy to do on line
, if living in Europe

unfortunately - Serbia , where I'm living - somehow isn't in Europe , so I'm
Paypal-less 😉

that means that I'm just lazy to chase soft surround impregnation goop from
Europe , taking in account that there is no domestic one

then guy asked where to search for surround impregnation goop ;

my reply :

sorry - just google ;
search for something like this : Speaker Repair Adhesive, Sealer, Cloth Surrounds, Foam Surrunds, MI-1291

but , it's wise to buy only after confirmation from seller that really soft
thing is in question

Zen Mod

then guy asked for difference sound-wise , pre and post procedure ; my reply :

sound-wise - taking in account that my pair is most mint pair I ever had
opportunity to even see (except surround condition - most probably as result of
no-usage for all long years ), I'm eager to say that they're sounding just as
proper pair of K3809 😉

right now being in stage of preparation of making boxes for them , I'm having
fresh experience just listening them in bafle-less iteration ; even like that ,
there is proper difference in bass , comparing to prior (surround treatment )
performance

whatever , fact that plain and common Ethanol is sufficiently good as solvent
for old impregnation , was nice surprise ....

Zen Mod


I hope you enjoyed little story :clown:

In case that I remember to get cam to my workshop tomorrow , I'll make few pics and put it here , along with few pics of same drivers prior to fun procedure

tone control preamplifier

Hello
greetings can anyone help me out i am trying to make this simple
tone control as i am not a pcb designer can this tone control be
made on a double sided pcb with lots of ground plane and SMD
components.I have made it on a dot pcb with LM4562 can it be bettered
with OPA1612 IC . Sorry for asking so many questions
warm regards
Andrew😕

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ADC0804 Relay Attenuator

64 step relay attenuator using an ADC0804 8-bit ADC.

I am not using the 2 lowest lsb's.

The biggest problem when using something like an ADC0804 together with relays for attenuation purposes is that you can get situations where one relay releases(breaks) before other relays has time to operate(make). This is especially a problem with 100000>011111 transitions where you risk having no attenuation if the first relay turns off before the 5 other relays activates.

The solution is to implement a make before break action. This is usually done by having a microcontroller control all the relays which makes it easy to insert delays that give you the desired make before break action.

However, what if we could use the characteristics of the relays to get the same desired make before break action?

Looking at the datasheet for the excellent low signal relay Omron G6K-2P-Y it is shown that operate and release times are identical at 3mS MAX with 1.4mS as a typical value. Bummer. However, when designing with relays it is good practice to include a flyback diode to protect the BJT or FET used for switching on/off the relay. The downside to this is that you get longer release times, usually on the order of 5+ mS.

In this case the longer release times should in theory give you enough time delay between the making and breaking of the relays to avoid the no attenuation situation.

This is what I have tried to implement here.

The pot should be wired so that when it is turned fully ccw, you get the full voltage to the ADC which makes all the relays go on and giving you full attenuation. Now as you turn the relay the voltage drops, turning on/off relays as you go. Since we have slowed down the release time due to using a flyback diode all the relays should in theory ensure you get a make before break action at all times.

Does the theory hold true in real life? I do not really know but I have convinced myself that it would work just fine.

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For sale Too much Stuff

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McPHAR 127 Power Supply

Hello all,

Does anybody have any information on this unit? Seems to date back to the late 40's or early 50's. Meters full scale indicate 500V and 300mA. Uses 2x 83v, 4x 6L6G, 1x 6SN7 & 1x NE56. Any info appreciated.

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