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Cornet 2 tube phono stage (~100KB) - Page 2

post #16 of 32
Thread Starter 
I'd rather smell a custom title than smoke, myself.
post #17 of 32
Quote:
I'd rather smell a custom title than smoke, myself.
Oh,I dunno man,depends on what's smoking
post #18 of 32
Thread Starter 
I finished this up a little while ago, but then some non-audio crap (tons of rain in a short timeframe) forced me to set all aside for a while. I have finished the phono stage, and have heard (only) four albums through it so far. So nothing conclusive yet, as I have a very long way to go with break-in. I am building an inverse-RIAA circuit, which I will then stream music from my netwerk through, into the phono stage... probably for a week.

Initially, it does sound pretty good. It was a bit harsh, so it's really too early to say. Even the tubes are new... I'm not about to install anything real nice until all else is sorted out. Also, there is a slight hum with the amp vulume up pretty loud. Granted, it would be unlistenably loud at that setting, but I think I can do better with some revised wiring from the board to the panel. I did not use the board-mounted jacks, fwiw.

Plan is to revise the jack leads, finish inverse RIAA and burn in. Then report back here with (hopefully) great news.
post #19 of 32
Quote:
I am building an inverse-RIAA circuit, which I will then stream music from my netwerk through, into the phono stage... probably for a week.
you lost me on that one Mark.why would you stream through your phono stage and not through a line stage ? Adding another "device" in the signal path is never a good idea if it can be avoided plus any errors in either the inverse RIAA network or RIAA EQ network can be grossly exxagerated if they should fall in the exact same places.
I am sure you have a reason but I can't see it with all the trees in the way
post #20 of 32
Rick, I think he's doing that for burn-in.
post #21 of 32
Quote:
I am building an inverse-RIAA circuit, which I will then stream music from my netwerk through, into the phono stage... probably for a week.
OK I see where that could mean burn in but I don't see why an inverse network would be needed for that either
post #22 of 32
Quote:
Originally Posted by rickcr42
OK I see where that could mean burn in but I don't see why an inverse network would be needed for that either
If you take a the line level feed from the sound card and run it through this phono stage what is the the internal "RIAA filter" going to do to it?

I believe the rational is that by adding a inverse RIAA network Mark would end up with something closer to what the phono stage will sound like when used with a Turntable.
But I could be mistaken.
post #23 of 32
Quote:
If you take a the line level feed from the sound card and run it through this phono stage what is the the internal "RIAA filter" going to do to it?
Treat is as any other signal obviously.We do not "pre equalise" to burn in equalizers nor do we create inverse filters to burn in filters (such as a crossfeed network) or bandwidth limit to burn in a selective sectrion of the audible spectrum.The RIAA feedback curve is for listening and not for circuit function which would be quite happy playing a non-pre-equalised and crappy sounding signal.
The only thing I see as essential would be a straight -40dB pad at the input to prevent overdriving and overheating the stage.
Unless I am missing the obvious here the need for a Anti-RIAA filter not needed for simple buring in but would be nice to have to trim the EQ "nulls" asumoing dead accurate on the negative filter
post #24 of 32
Quote:
Unless I am missing the obvious here the need for a Anti-RIAA filter not needed for simple buring in but would be nice to have to trim the EQ "nulls" asumoing dead accurate on the negative filter
Bingo.
Give the man on the top of mount rickster a cookie.
Analysis of the output across both filters would produce an effective way to troubleshoot the preamp... or verify it's accuracy.
Back in the early 80s there was a "calibration album" that you could buy to verify that your entire system was performing "as planned" but for life of me I cannot remember what the name of it was... old age creeping in?
post #25 of 32
Quote:
Analysis of the output across both filters would produce an effective way to troubleshoot the preamp... or verify it's accuracy.
This is not a scratch build but a semi kit from verified plans so why would anyone need to verify the accuracy when the very anti filter would be just as suspect ? Who is veryifying that ?And with what ?
post #26 of 32
Thread Starter 
I'm using the streaming music simply to avoid excessive wear and tear on a CD player during burn-in.

As for the inverse RIAA, I have it, so I will use it. I also prefer to break in the phono stage with a signal that is essentially the same as the signal it will normally process, just as though I were playing hundreds of albums through it on a turntable.

I built the inverse RIAA for the purpose of testing. I can apply a square wave through the iRIAA to the phono stage and check the output on the scope. Also, I can then use the same iRIAA to compare the Cornet to my other phono stage, and to any other phono stage, for relative comparison.

As also noted, I can use it to play a CDP through the Cornet or any other phono stage to how the output sounds compared to straight off the CDP.

**********
In other news, I have not started burning it in yet.
My dryer crapped out the other day, so I spent a long time disassembling that in order to replace the belt and tension idler arm assembly. It's a Swedish dryer, so I could not find any directions, and instead took the slow approach, taking a TON of notes on what wiring goes where, and what torx bolts go in which locations. It took me about two hours to get it all apart to the point where I could remove the motor... a little scary.

The shaft for the idler arm broke off and was still in the motor casting, so I had to take apart the motor itself and drill out the stud residue. On the upside, everything is as clean as a whistle now. If DHL fails to deliver my parts, I'm going to go postal.

I believe that when the dryer was delivered and set up, it was not exactly levelled, so the cabinet was slightly racked, causing some misalignment of the geometry. The drum rollers are still good (mounted on huge SKF ball bearings!), and the motor is prime. So after I install the new tension ider, I will make sure the thing is tuned up right.

Funny thing- I also will be adding some dynamat to the inside cabinet panels, to get rid of the resonating sound that emanates when it tumbles! I'm such a tool. Any other Tool-Time mods I should consider before I finish it up?
post #27 of 32
Hehe, dryer mods? I can see the "post pics of your appliance mods"-thread
If you haven't already, putting the dryer on soft (rubber) feet will usually dampen the noise a lot (spikes may be a bad idea, but you could try it and post your impressions )


/U.
post #28 of 32
Thread Starter 
There is also plenty of room behind the front panel for some circuitry. Maybe a noise-cancellation amp, mike, and some full-range speakers?

Actually, I did note that the levelling feet have very thick rubber pads already. I mean, they are 2" in diameter and 1.25" thick! I was pretty surprised to see that. It's an Asko dryer, and has otherwise been good. Looking inside, it's pretty evident that there was some misalignment, and the clearances are tight. The ribbed belt was in NASTY condition.
post #29 of 32
Voodoochile,

Are you close to posting any impresions yet?

I've had my eye on this kit for a while now.
post #30 of 32
Thread Starter 
I should be good to go by the mid to end of next week. I just got my gear back in place after Boston. Last week I was sort of wrapped up in trying to get things together for that.

My dryer is now excellent, though! The thing is beautifully smooth and quiet; adding the panel damping seems to have helped much. As of last week, all domestic appliances are in good working order, so I'm getting back to the workbench finally.
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