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Passive tone control

March 12, 2016, 2:43 pm
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O.B. Newbie help?

March 12, 2016, 3:11 pm
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Hello everyone. So I am looking to do a small dipole O.B. For my family for the family T.V. Room. I didn't want to to buy a sound bar and knowing I have a lot of extra wood around that's taking up some space in the garage. I wanted to build a simple O.B. So what program do I need to get started? So The design is after the no more O.B. Dipole from tekton speakers with 2 fostex drivers. ( not trying to copy but, was told they don't offer it anymore? So Please help I need it. Thanks Jeff

P.S. There's a picture of the design I am thinking of? Cheers Jeff

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Hiwatt custom tranformer 70v bias question

March 12, 2016, 3:38 pm
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Am 90% complete with my hiwatt DR103 (4xel34) clone but want to do improve the anemic bias circuit. Haven't purchased a PT yet but am looking at betting a custom toroidal build with a 70v bias tap as the stock 50v is not enough they run hot usually around 38v. There is a mid circuit with one pot I was going to use. Need to know if a 70v tap will work if so what value should my resistors be. Thanks in advance.
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SU-Z780 Technics new Class A amplifier lights but no sound no relay click

March 12, 2016, 4:18 pm
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Hi All,

I have had this amp since new in the 90s.

whilst playing some music it stopped suddenly and the VU lights stopped working along with the sound to the speakers.

I turned the unit off. unplugged every thing except the power cord.

I turned it on again and all the lights came on, however the speaker relay has not clicked like it normally does a few secs after pressing the power button.

I took the cover off the unit and looked and smelled for anything burnt but nothing. The main fuse is of course fine as the power is on. There's a large chip(~50mm) and another 15mm connected to the one mammoth heat sink and a Fan off that. I can see the speaker relay ...well the only one there.

Apparently(from the user instructions) there is a protection circuit that resets itself after a speaker short or overload, but that's not helping as I've got every thing disconnected and I cannot see it anyway.


I tried connecting a CD source to the RCAs but nothing.
I tried the headphones jack, but also nothing.
I've read on this forum that the speaker relay might need replacing.
I've ensured that only one of the 2 speaker circuits is turned on.
I've checked that the VCR switch that diverts the input monitor is off.

there is no schematic on the operating instuctions so I am flying blind here.

are there any internal checks that I can make to help identify the components to replace ? like perhaps bypassing the speaker relay ?

thanks guys, judging from other threads, you have a good community here.
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Dumb Question about Crown XLS402

March 12, 2016, 4:39 pm
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Hey guys,

I've been given the task of putting together a stereo for a a 600sqm (6500sqf) warehouse. It's roughly rectangular, so no real concerns about anything fancy. There is a fairly limited budget for the system, so my plans were:

-Crown XL402 amp (bought second hand for an absolute steal) running at 4ohm (400Wrms/channel)
-2 pairs of 8 ohm 12' PA monitors in parallel (yet to purchase)

Obviously SQL isn't a major concern, it just needs to be relatively loud.

I have one question about the amp - grabbing a manual off the net, the only mention of inputs are female XLR on the back that are balanced. This is fine, except there's a matching pair of male XLR jacks right next to them. These aren't mentioned anywhere in the manual, nor on the amp. On the PCB they are designated 1A/1B and 2A/2B respectively.

Question is this - is this a pass-through connector for hooking up more amps, or is it just abother input option?

Attachment 537086

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Lite Audio MV-01 / MV-06 remote controlled volume/input selector

March 13, 2016, 1:05 pm
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Just bought a Lite Audio MV-01 / MV-06 remote controlled volume/input selector and hooked it all up what i thought was correct, to my dit tube preamp everything works but Iam getting an irritating hum I think its a ground issue any help would be great .
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Schematic for my ridiculous amp is partly complete.

March 13, 2016, 1:18 pm
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Greetings. :D This is my big project. It is an Asymmetric Split-Stereo Guitar Amp. 7 Valves, 4 Transformers, 2 Tone Stacks, 2 Channels,2 Speakers, 11 Pots, 5 Switches and a special cross-connect system. Class A and AB simultaneously. Single-ended and push-pull at the same time. There's a lot of ground to cover. I learned (and borrowed) quite a bit from DvNator at "Chasing Tone". DvNator's Amp Projects | Tube Guitar Amp Stuff He's got an excellent website that he frequently updates with lots of schematics, sound-clips and explanations.

The cross-connect system allows the user to mix pre and power amps. I'm going to make this easier on myself by establishing terms. The top pre-amp is called "Pentode", the bottom pre-amp is "JCM". The top power-amp is "SE", the bottom power-amp is "PP".

  • Pentode starts with a bypassable EF86 gain stage. This stage also features a tone shaping trick that I borrowed directly from DvNator. When S1 is open, the stage adds a treble peaker. When S1 is closed, the stage adds a mid-scoop. Closing the bypass switch removes the stage from the circuit. The next gain stage leads into a Baxandall tone stack, and then a gain recovery stage and into the cross-connect.

  • JCM starts with a typical Marshall gain stage, the standard treble peaker and a second gain stage which leads into the cross-connect.

  • SE goes from the cross-connect to a 6V6 SE output stage. There is an 8 ohm speaker wired into the circuit and an Ext. Speaker out.

  • PP goes from the cross-connect into a gain stage, a cathode follower stage and then into a FMV tone stack that features another trick that I learned from DvNator. The Brit/American switch alters the character of the tone stack, from an approximation of the Fender frequency response on one end to an approximation of the Marshall frequency response on the other. (If anyone is curious - the American notch is a pretty close match for Fender blackface. The Brit side is much like the Marshall tone stack, but lossier.) Then on to a LTPPI with Presence control, a PPIMV (installed on the back of the amp) and ECL84(6F4P) power tubes. The output tubes will be controlled by VVR, (power amp only). Then on to the OT, speaker and Ext. Speaker out as it was for the SE circuit.

When the cross-connect is wired straight across you've got two amps in stereo. The first is basically a Fender Champ with a Baxandall tone stack and the option to goose it up by using an extra gain stage. The second is essentially a small-scale Marshall amp, loosely based on a JCM.

When you cross-connect them though, it gets a little bit interesting.
The JCM circuit drives the SE power amp with no tone stack in the way. The Pentode pre-amp on the other hand progresses through both a pre-distortion Baxandall tone stack and the post-distortion, post-cathode follower FVM tone stack.

Click the image to open in full size.
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Critique of Phonograph Conversion Amp Plans

March 13, 2016, 1:23 pm
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Hi! New guy here -- thanks for having me! :)

I'm fairly new to the world of electronics, and the most ambitious project I've completed to date has been performing the Lyle Mods to my Marshall Class 5 amp. (Successfully, even!)

But I got the bug bad. :) My copy of Morgan Jones' Valve Amps book isn't even here yet, but I've already gotten started...

I've salvaged an old Capehart-Farnsworth AM/FM Radio & Phonograph to do my first salvage amp creation. So far, there's a lot that's very familiar. But, of course, this didn't start life as a guitar amp so there's some oddball stuff, too.

The good news is I got a power transformer, output transformer, Alnico speaker, and tubes and bases for a rectifier, pre-amp, and output tube.
Plus a lot of caps and resistors which may or may not be very useful -- and a pile of other junk that certainly isn't.

I've studied the schematic and stripped it down to what I think are the bare bones of what a very basic guitar amp would need. Like so:

Click the image to open in full size.

Now, I'll freely admit I've completely cribbed this off of C-F's original schematic. Aside from a LOT of deletions, and adding an input jack, I haven't changed anything. While I had some wacky ideas about making this into something it isn't, I really don't need to buy a bunch of new parts when this might not work at all, and also -- these parts DID work well enough together at one point. I'm not likely to blow out this fragile speaker* or burn up the OT or whatever, by sticking with this layout.

[* -- The speaker is a nice big 12". But it is LIGHT, with a very small alnico magnet and about a 1" or so voice coil. I don't think I'll be rattling the windows too badly with this one. But it might sound cool for late night practice...]

But the cap and resistor values I see in the tone stack don't look like numbers I'm familiar with. I see 3.2 Meg. Ohms on the tone pot. Wow. And about half that on the volume pot. I know the screened frequencies cut out by these will be a function of both the resistance and capacitance in the circuit, but is this even close to right for a guitar?

And what about moving the tone stack in front of the pre-amp? I didn't, but wouldn't that give me control closer to the final product?

I sure do appreciate any thoughts, comments, warnings, improvements, suggestions, or just well-wishes. :)

Thanks!

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kicker l7 2 ohm

March 13, 2016, 1:40 pm
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hi, im new to this site. Im looking to change my setup. currently i have 2 kicker l7 10 inch 2 ohms with an audiopipe aplc 6002 2000 watts for bass. i want to keep the l7. the reason i want to change it is that after i turn it up it seems like it gets to its capacity and sounds a little distorted. im wondering what amps wound be recommended to push the l7 to the max without them sounding distorted. thanks for your input.

also is saw some critical mass 2500 on fleabay for reasonable price($600). are these amps as good as they portray to be. or are they just pricey and overrated.
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arc xdi 1200.6 slight speaker hiss

March 13, 2016, 1:48 pm
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I've had this amp for a few months now, bought it used. I noticed a hiss coming from my speakers with the volume all the way down. Naturally, I eliminated all but the amp, as well as shorting the rca inputs. On the bench i can produce the same results, noise level is the same even with inputs shorted out. It sounds like normal gain hiss, as if the gain were cranked all the way up, but is there even if the gains are all the way down. Given, it does increase if i turn the gain up (starts to sound louder near half way up).

Numerous times, I let it go, reassembled it and put it back. But now that I have installed a Rockford Fosgate 360.3, it's irritating me again.

Worth noting that the larger toroid near the edge also has a high pitched whine that varies in pitch when i push on it. I scoped the area and all "seems" well. Gate driving does not vary and is a solid square wave. I ordered some high temp rtv silicone and I will try to get it to shut up. The whine is noticeable if i have the back hatchs to the trunk open, but otherwise it is not. Unsure if that is related, but thinking not. Speaker hiss does not vary with the inductor whine.

I've been in contact with Brad @ Arc and he has been very helpful. I froze the area near ch1-4 outputs and noticed a change in the sound of the static. I replaced the two 3.3u caps to no avail. I did not have a lot of hope with that anyway, as the static is present on all 6 outputs.

Scoped various rails, all seem relatively clean. Even went so far as trying probing a .1u across various filter caps to see if i could hear a difference, nope.


As I said, from time to time i shrug it off and tell myself it's normal for a class D, but it seems like it should be better.

Any advice? :dunno:

Also, it's a beautiful and powerful amp besides this issue. I've considered trying to send it back, but would rather sort it out and keep it :).
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Pye HF25 Tube Monoblocks: Restoring Legends

March 13, 2016, 1:51 pm
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Hi Guys

I've asked a few questions elsewhere on diyforums about these amplifiers and one of the most vexing questions was how to re-apply/restore legends after repainting.

I've finally settled on laser-printed waterslide film and silver foil overlays on the original corroded legend plates.

Having never worked with waterslide film until now, I made a test today, using all the etch prime paint, light blue base coat and finally acrylic clearcoat I'm going to use for the actual restore.

I have the matching Pye tube pre-amp and sanded down to bare aluminium one of its cover plates for my try-out as I wanted to see if all goes according to plan. The first paint application (painted with my airbrush) was the grey etch primer for aluminium, then the matched light blue paint.

I let these two coats dry overnight and then applied a random-choice laser printed text.

When all the moisture had been expelled underneath the sticker, I applied acrylic automotive-type clearcoat over the entire surface.

I think this looks OK as one cannot really see the type's cutting edges unless observed from closer than about 3".

I'm also showing the refurbished legendplates. These were aluminium foil applied over the corroded originals. I cut away the sticker over the stamped serial numbers so that's what you see there.

I will soon start with the work proper as I have obtained all of the absent bits such as an original Bulgin on/off switch, one Bulgin power plug and two tubes which I needed.

bulgin

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Morel 536/8 series Junk?

March 13, 2016, 1:52 pm
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I have been looking at the CAW / EW / ECW 536 series of drivers. I have noticed that the cheapest (CAW536) has the most reasonable response curve, and thereby, less of a fortune spent on the crossover. The other two are significantly more expensive because of superior parts (apparently). Having said that, I have heard some pretty bad press about them... miserable distortion.

Have any of you experienced this? If you were left to your decision about these 3 drivers, which would you choose? At the moment, the cheapest one seems to be the best because the response curve isn't as much of a mess.

What are your opinions?

Morel CAW 538 5" Cast Frame Woofer

Morel EW 536 5" Woofer

Morel ECW 536 Coppersleeve 5" Woofer
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feedback from UK

March 13, 2016, 2:02 pm
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Click the image to open in full size.

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From: paul.

Dear Victor,

The TU-8200DX went together like a dream....what a lovely kit! The end result is very pleasing, and I am now running some valves (tubes!) in. The instructions were generally very good, though the resistors table for the main board is just too ambiguous to 'tick off'. I preferred to use the pcb layout diagram and use that instead. Maybe the one bit of feedback that I'd offer Elekit is to improve the instructions in that area. I'm an ex-RAF electronics technician so I guess I fall in the 'professional' category of constructors ;-)
After you sending me the upgrade resistors, I got the bug to upgrade so ordered some Mundorf capacitors from a hifi component dealer here in UK...so my TU-8200 is specc'ed pretty well. I bet you're not short of photos but thought I'd send you a few. All I need to do now is find a label that says 'Made in England'. Haha.

Best regards Victor, thank you for being such a great chap to deal with!

Paul


Click the image to open in full size.
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FS: Behringer ECM-8000 calibrated by Cross-Spectrum + M-Audio Mic Pre

March 13, 2016, 2:07 pm
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Includes original case, and calibration file on CD as per Herb Singleton of Cross Spectrum. Excellent condition for the mic. I'm throwing in the M-Audio Mic Pre which provides phantom power to the ECM-8000 + associated cables for free (XLR shielded cable, loop back cable for the mic preamp, and USB cable).

$60 + shipping.

Will ship anywhere, PayPal preferred.


Best,

Anand.
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F.S Hypex SMPS600

March 13, 2016, 2:10 pm
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Scanspeak (Rega) D2008 7203 like 8511?

March 13, 2016, 2:24 pm
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Hi. Newbie here.
Have a pair of Rega ELA mk 1.25 and have picked up a pair of Linn Kabers for 100 GBP. Don't like the early mk1 ceramic tweeters in the kabers. I understand that scanspeak D2008 and Hiquphon OW1-92 are drop in replacements.
Really like the sound of the Regas tweeter at 4k plus. Much more open and the boxes vanish where the early kabers tweeter doesn't. So...
The ELAs have an oem driver from Scanspeak D2008/7203. Reputedly they have no ferro and have been tuned to match the crossover in the ELA which would suggest they might be closest to the 8511, with the 7203 no longer available and the 8512 having ferrofluid and a higher resonance point of 800hz compared with 650hz - but what should I put in the kabers? Can't afford the Hiquphons. Could cannibalise the Regas, but this seems a shame. How similar could the 7203 and the 8511 be? Hoping that someone on here has been there done that, or has an insiders view. Can anyone help.

Thanks Andy B
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Why do high-Q drivers exist?

March 13, 2016, 2:37 pm
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Low Q drivers are very useful in that they can be put into horns, vented boxes, APs, etc. Semi-high Q (0.4-0.8) speakers can be put into sealed boxes, TLs, TQWTs, open baffles, etc. What I don't get are High Q speakers (0.9-1+). You can't really build a proper enclosure for these, and whatever you make the system Q will never be lower than that. Considering the optimal Q is 0.707, why would anyone make a driver with Q higher than that? I feel like I'm missing something here...
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toriod transmofer

March 13, 2016, 4:35 pm
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how do i get 9-12v ac from this transformerOutput Power: 132W
Insulating strength: 10Mohm, AC2000V/1min
Input Voltage (AC): 115V /230V 50Hz/60Hz
Output Voltage (AC): 0-200-220-260-280-320 (100mA) x2
0-6.3V (2A) x2
0-5V (5A)
0-18V (1A)
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Dead OCM 55...

March 13, 2016, 4:53 pm
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Hi,

is there anyone out there that could help me with a Belles OCM 55 line preamp schematic?

Thanks, Dirk
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Totally stupid!!

March 13, 2016, 5:35 pm
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http://forums.mustangworks.com/showthread.php?t=29134

All I can say is: I couldnt believe what i was reading!!!!!!!!! (By page 3 its literally out of control :D (So far thats as far as i have read))

At least the guy didnt post this UNDER HIS OWN NAME!! (Like ppl do on facebook for example (TOTALLY STUPID))

I wonder if the guy had a camera in the car?? (Im wondering how he discovered what they did)


All kinds of dishonest/UNTRUSTWORTHY people in this world....... (I cant believe the thread hasnt been locked!!)
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