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Hum debug, or humbug if you prefer.

May 31, 2020, 8:24 pm
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Recently purchased an already built pair of M125 amps and an SP9 preamp. When all hooked up I get about a 4db hum from both speakers, one about 5db, the other about 3db.

I pulled the RCA cable out of the preamp and shorted it while it was connected to the M125. and got silence. So the problem seems to be coming from the preamp and/or its interaction with the monoblocks.

For additional testing I lugged my Adcom GFA 555 II (heresy, an SS amp) in and hooked it up. I turned everything on and I got a much louder hum (probably more sensitive). Interestingly (to me at least) If I power off the preamp but leave it attached to power, the hum decreases a little, but it is still there.

If I disconnect the Adcom from the preamp or I hook my source (a computer) directly to the Adcom, dead silence.

The preamp has a 3 wire power connector. The M125 which is has the lower volume hum has the ground lug cut off (previous owner). The Adcom has a two prong power cord with one lug larger than the other.

What should I do to further troubleshoot this issue?

Or if someone knows precisely what the issue is and how to fix it this would be good too.
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Trade Icepower 500A Modules for Hypex UCD400 HXR Modules

May 31, 2020, 8:52 pm
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Trade Icepower 500A Modules for Hypex UCD400 HXR Modules...

I have a pair to trade...maybe more...
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BIAS/IDLE current for Creek 4040 s3

June 1, 2020, 12:05 am
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Hi guys, just wondering whether you could help me, I am in the process of recapping an old creek 4040 s3, though, I cannot source a service manual, do you know the bias value and measuring points?

Thank you!!!!!
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Volume and port size help

June 1, 2020, 12:11 am
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Hi all

I am just about to build a sub box to match my full range speakers which are loaded with Fane Sovereign 12-250TC.

I will be using a Fane 18XB 8 ohm and I think I will be building a Butterworth B4 ported box which I can change but does need to be reflex style box as I do need to keep the weight down and the driver needs to be shown.

Due to it needing to match the FR speakers and fit where it needs to go the external size will be 960h x 650w x 450d but internally I can build volume to suit. I will be using 18mm plywood for the build.

I just want to confirm that I have it planned correctly with the following internal dimensions.

154.12 litres
F3 = 39.64 Hz
FB = 40 Hz

Port
Dv = 15cm
Lv = 10.39

I am struggling with the ports as well. I would prefer one large rectangular port at the base of the box, but I cannot find any calculators online for that, can I just take the area of the round port and use that?

As you can see I do have a lot of volume to play with internally so I am open to suggestions in how I can get this box to function the best I can.

I have also included a photoshopped image of what I am trying to achieve which is very loosely based on an early King Tubbys Hometown Hi Fi and V Rocket.

Thanks


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Universal HV boards

June 1, 2020, 12:26 am
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Ive designed and ordered these universal HV rectification boards. They are designed to suit the majority of power supply applications below 500VDC.



The boards measure 51x150mm and have M4 mounting holes 5mm from the corners and in the center of the board 5mm from the edge. Due to its size it should mount conveniently against the wooden chassis of most amplifiers.



The electrolytic footprint is for a 35mm snap-in capacitor. and will accept the majority of twin pole electrolytics.



See the attached schematic, the board is made to be used with either solid state rectification or tube rectification if D1 and D2 are jumpered and D3, D4 left out.

The first capacitor is either a 35mm diameter snap-in (c3 ) or one or two 37.5mm pitch Wima MKP4 4.7uF 630VDC caps for tube rectification.



Filter options are CRCRC or CLCRC, there are external connections for a choke.



The boards are tin plated and ROHS conform.

Aksing €8 per board ex postage.

Attached Images
File Type: png Universal HV board JLC.png (75.4 KB)
File Type: png UniversalHV Board.png (49.6 KB)
File Type: png UniversalHV schematic.png (38.8 KB)
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Zenon board driver

June 1, 2020, 1:42 am
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someone who has a diagram of a Zenón boart 7k driver card!!
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VFET outlet

June 1, 2020, 2:15 am
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left from my past DIY perfectly working Tokin VFET :

2x TOKIN 2SK180 one with a ding on the case but mesure well
2x Tokin 2SK182es
2x matched THF51S
1 THF51S free

asking 150€ for the entire lot free shipping for EU .

cheers:)

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TUBE 71a

June 1, 2020, 2:20 am
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selling a batch of type 71a DHT 6 globe and 2 ST shape

asking 150€ for the lot free shipping to EU

cheers

:)

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Sold

June 1, 2020, 2:23 am
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Marantz CD 67

June 1, 2020, 3:38 am
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I have marantz cd67, It is not reading CD disc. Does Not spindle, you can hear laser 3x moving up. It is old laser, so I try to increase laser power on trimmer. And in one point CD start to play, you can switch from track to track. But if you turn of player, and tur ON, it fail again. I buy new replacement VAM1202 mechanism. But same again .... On the new I didn't touch the trimmer, but when randomly pres play, and spin with the finger in same time, if you are lucky it start to play. I watch pattern when start to play, it is 1.2Vp-p, and center is 1.5Vdc. On manual new laser is 1.7Vp-p, and center is 2.5Vdc. On old laser pattern is 0.8-0.9Vp-p and center is the same 1.5V. Servo board need 5V, on the schematic after reg. it is 4R7 and 47u. when new laser tries to spindle voltage fail to 4.6-4.7V, but with old laser voltage fail to 4.2V ( maybe because increased laser power ). Does anyone have an idea?
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(2) Seas SL26R (D1003) 10" Passive Radiator (Mate to L26ROY) NO SUBWOOFERS

June 1, 2020, 7:25 am
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Variable Transconductance tubes

June 1, 2020, 8:18 am
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Friends

I see some preamp designs using transconductance valves a few times.
If I connect a variable transconductance pentode in triode mode, can it be used in audio, or will it generate a lot of distortion?

Thanks

Aldovan :p
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brutus bre 2000.1 unidentified ic

June 1, 2020, 8:56 am
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Click the image to open in full size.Click the image to open in full size.trying to find replacement ic for these help !
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FS: Open Baffle Full range & EL84 SE amplifier

June 1, 2020, 9:51 am
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I`m posting the Ads here, there may be interested buyer in the Montreal Area... And since I know that this is the kind of stuff we DIYer like, here it is... A very good price to play with SE amp and open baffle...

See on Canuck: FS: Full Range Open Baffle speakers and tube amplifier system For Sale - Canuck Audio Mart

For Sale complete system (DIY) includes SE Tube amplifier EL-84, with tube rectification and two matching Full range Open-Baffle speakers, all DIY made. System is working fine, part of an Estate sale, and sold as is. Since it is very large and heavy, local sale and pickup in Montreal/Laval Area only.

Amplifier: Very nice built with audiophile parts (Kiwame, Mills resistors, Cerafine & Solen caps, CLC filtering, point-to-point assy. Includes an ALPS volume control. RCA inputs and speaker binding posts. Tube complement: Tube rectifier EH 6CA4-EH, gold pin, 1x ECC81 Telefunken, 2x EH EL84

Speakers: Open baffle design, Full range 12'' 'Zenith' 49CZ903 (Actually selling for 279U$ on ebay...), Super Tweeter: Big-Air Acoustics S-CFM, Super tweeter cap Obbligato Oil, 1.25'' wood front pbaffle, very nice condition.

Driver on ebay: Matched Pair Vintage Zenith 12" Speakers Woofers P/n 49CZ903 1960 Very for sale online | eBay

Would like to sell the kit, and since the price is way under the cost of parts, price is firm at the moment.
That's an excellent price for anyone that woudl like to try or experiment with a nice SE amp and Full range drivers...

Accept Cash on delivery, EMT bank transfer or Paypal (add 3% fee or 'Friend and Family)

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Koda ... says Hi

June 1, 2020, 10:03 am
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WTB: Seas FU10RB 4" driver

June 1, 2020, 10:40 am
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Hi

I want to buy 2 of the Seas Prestige FU10RB drivers that are either new or in good condition used.

Located in California, though shipping for these should be cheap so anywhere in US is ok

Thanks

S
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Car Audio DIY Crossover Design Help

June 1, 2020, 10:41 am
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So I'm going to change my car audio system to the following:

Woofer/Midbass: Dayton Audio RS180-4
Tweeter: Dayton Audio ND25FN-4

Firstly, does this combination seem good? Looking at the frequencies and from what I've read about the RS180-4 drivers, they need crossing over about 3khz for best performance and the tweeters should be okay crossing over above 2.5khz.

I've had a go at designing a crossover on xSim and wondered if the more knowledgable on the forum could point out my errors.

Any help would be greatly appreciated!

Click the image to open in full size.
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LXmini Clone

June 1, 2020, 10:52 am
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As proof of the concept, I decided to make a clone of the LXmini speaker.
The results are excellent both audible and measurable.
The drivers I used are Mivoc swm 68 and TC9FD18-08 which in my opinion is a far better driver than Seas FU10RB (H1600-04).
I ordered the Seas L16RN-SL (H1480) waiting to arrive to make the final version.
If someone is an expert in designing parts for a 3D printer, they might be able to contribute to the design by designing the upper part that comes on the tube.
Off axis measurements are 0-22-45.
The microphone I use is Umik-1. It has a horrible feature to bring down the response over 18khz so I don't know the real situation above.
Crossover is terrible minidsp 2x4.
Attachment 849297
Attachment 849298
Attachment 849299
Attachment 849300
Attachment 849301
Attachment 849302
Attachment 849303
Attachment 849304
Attachment 849305

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Hello from Germany

June 1, 2020, 11:03 am
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Hi, I'm new to the Hi-Fi world and I love to learn things. I've been considering investing in a Hi-Fi system for my desktop and my living room alike. I figured: why not do everything by myself? I have time, am patient and unequivocally wish to enjoy the process of searching for the right parts, understanding how it all works etc.

Any advice for a neophyte like me ? :)


I only have a pair of Focal Spirit One S Headphones on my desk... hopefully it'll soon change with your recommendations (i.e. DAC, AMP, Speakers...): I'm open to any suggestion. Where should I start ?


Thank you for reading this!
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FS: Amp Camp Amp V1.6 Kit

June 1, 2020, 11:17 am
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New, unbuilt kit with all components in their original, individual packages.
$325 plus shippng.
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