John Curl's Blowtorch preamplifier part II

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I know you meant the other John, but I did buy it. And, it worked good for FM, however, whenever it finds and HD radio signal it switches automatically to HD radio. I read the manual and can't find a way to disable HD radio. If someone can tell me how, send me a PM please ... I cannot even listen to it in HD radio mode.
....
John

That, and other stuff, mods, etc... as well as links to other mods
Sony XDR-F1HD
 
Thanks for the inputs on the radio.
Working with Dick Sequerra about 25 years ago on the solid state version of the NAB FM radio, where I designed the power amp, Dick Sequerra was VERY insistent that he did not like ceramic filters, and he ultimately lost the project because he would not allow them to be used exclusively in his FM design, even a cheap one. This is probably why he is so impressed by this design.
However, I am glad for the provisions about this design, and why it hasn't taken over the world of audiophiles.
I just love my MARANTZ 10, (not B) sonically, but it is having trouble with its photoresistors as it is prone to do, and I have to pull it out of its shelf and fix it. However, now I have phono preamps all over the place, and that comes first.
Johnlaudb, you can keep to your own efforts, don't quit your day job, ;-), but it should work OK, once you put in the right cap bypassing.
I once had a similar problem with a Vendetta power supply buffer, and a 100pf cap fixed everything.
 
I have a Marantz 10 that I really love, but I have to fix it to make it useful for listening properly, again. Dick recommended the Sony, and told me that it was based on a very different technological approach than his early designs, and that he was impressed with its performance. What I am really concerned about is what analog IC circuits, whether external to the RF module or internal, and the output coupling caps. This is where many of these 'cost effective' designs fall short.

Hi John and others,

If you are in the mood for elaborated tweak (so the rest of us bloody amateurs can benefit from your or anyone else knowledge as usual;), I can supply the Sony XDR-F1HD service manual so we can all start playing with it:D
 
yeah, reminds me of this story i read a few moments ago:
Under the dash, and over my head - 2010-08-01 04:00:00 | Test & Measurement World

LSI, surface mount tech, chips you can't get without signing agreements, ...
you've really got to be dedicated to be a hobbyist these days.
:spin:

mlloyd1

The IP stuff has gotten crazy, no one is interested in anyone but the huge customers. If you saw the content protection proposals even for a buss from the trunk to dash you would be even more depressed. Someday it might be like your keys, if you lose both you have to buy the entire system. I didn't say this :)
 
MP3 & Broadcasting

Very interesting I can probably sample you from my ROKU box. How do you keep the student DJ's from preping their entire show on their Ipods? :(

Hi Scott,

I am fortunate enough to have had a couple of student station managers who are very interested in audio technology. I have given them short classes in audio engineering, and demonstrated the difference between CD and low-bitrate MP3. Once brought to their attention, they admitted that low-bitrate MP3 sounded like crap. Armed with this they strictly forbit DJs to do entire shows from iPods or laptops. Helping enforce this is the fact that the jock has to play three tracks from any disc in the playbox, and three from classic vinyl or CD from the station library each hour. All of this is entered into an on-line database:' Now Playing on WXYC 89.3 FM ' that is audited by station management. Jocks not in compliance get booted.

I know that students DO indeed do a lot of music from their laptops especially, but the station personel have been good about enforcing the no-low-bitrate over the air dictum. That being said, I have heard some really terrible sounding mp3s on WXYC.

You do what you can, and let the rest fall where it may, right?

Interesting times in radio for sure...

Howard Hoyt
CE - WXYC FM-89.3
www.wxyc.org
1st on the internet

Don't even get me started on the HD debacle....
 
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This Sony radio thing has got me interested. Thanks again for the links, that ALREADY have proven informative and educational. For example, a comment was brought up that sometimes you might want to stay in analog, and the Sony won't let you. Cut a wire, and add a cheap switch, and you have it. Also, the AUDIO output is shown. How convenient to bypass or improve! Frequency response improvements? Sure! Yet, this is serious technology, where the real engineering is beyond most of us, and is first class. Also, this starts as a very cost-effective complete system, from the get-go! This might be fun, and useful.
 
Wxyc

hhoyt

Your internet feed is great, what a coincidence the first thing out was some music from India. This will go on my favorites list.

Scott - I'm glad that what greeted you was pleasing, but please keep in mind that WXYC's free-format is ala 60s and 70s Underground FM radio, and can have it's highly challenging moments, depending on the DJ. WXYC has an excellent staff of jocks from 18 to 60 years old (including me) with a vast knowledge of music between them. One shift may be a sitar special with a jock who is himself an accomplished sitar player and be spellbinding, and the next may be a 19 year old speed metal dude. If speed metal is your thing, then you may continue to be amazed, but if not... Right now they are playing Sun Ra, who I love but who drives some orthodox jazz people nuts. If you don't mind me bragging on the station for a second, we became the first radio station in the world to stream on-line on Nov 7, 1994, we have won Rolling Stone's best college station of the year more than once (a dubious honor at times), and we do not play the normal college radio fare most of the time, much to our credit. For people who feel that life is too short to listen to the same fare over and over, WXYC can be nirvana.

Being an audio geek, I have set up WXYC so the MP3 feed is pre-broadcast limiter straight out of a PR&E (Pacific Recorders & Engineering) console with Jensen 990 opamps, into a PR&E distribution amp, and directly into MAudio fed MP3 PC. Since it is basically straight out of the board and has no limiter you may see greater than usual volume swings due to the unpredictability of the specific media level, or if the DJ is asleep at the board...on the other hand the fidelity can be quite good (for 128KB/S MP3). I auditioned Blade, Fraunhofer and Lame MP3 encoders before settling on DarkIce using the Fraunhofer codec running on a Linux box at 128KB/S. We are currently negotiating with our ISP (The University of North Carolina IT department) to host a higher bit-rate MP3 stream (192-256k) for audio geeks like us. I have an experimental stream running right now at 192KB/S from a Barix encoder running the Fraunhofer AAC encoder and it is noticeably better.

None of this MP3 fidelity can compare with a great source played at home in a good system, but it is a reality of the modern broadcast era that engineers like me have to deal with both HD foibles and MP3 stream optimization. The signal chain at WXYC is clean enough so especially listened to locally off-air on a great system it is pretty damn good (if I don't say so myself), way better than the MP3 stream at least.

Sorry to be so long winded on the subject, but high-fidelity FM broadcast signal chains has been a 25 year long obsession for me.

We now return to the Blowtorch thread, long in progress...

Howard Hoyt
CE - WXYC FM-89.3
www.wxyc.org
1st on the internet
 
Guess ya missed this when I posted a few back?
 

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