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Old 5th February 2013, 09:10 PM   #1381
mfaughn is offline mfaughn  United States
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Here's some pics of it in its current state...
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Old 5th February 2013, 10:10 PM   #1382
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Originally Posted by mfaughn View Post
Hooked up to a set of Snell A/iii now. Sounds very good...more and more so with each passing minute. There is a bit of a hiccup though. When playing music with ridiculous amounts of low bass (e.g. Santigold - Fame) things get rough. I get distortion throughout the spectrum. When the bass hits the vocals warble. I am guessing that this is some sort of interaction with the speaker because when I bi-amp the speaker so the DCPP is getting the full signal but only handling the mid/tweets then everything is fine. While the DCPP does make a spectacular boom I am just fine with the bi-amp situation (400wpc of iron-fisted Ashly). I'd still like to understand what is going on here for sure though.
That just sounds like simple clipping to me. Don't forget, the stock DCPP only has approx. 20 watts/ch. With average efficiency speakers, it's not that hard to push the amp beyond it's happy place.

jeff
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Old 5th February 2013, 10:51 PM   #1383
mfaughn is offline mfaughn  United States
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Originally Posted by vinylkid58 View Post
That just sounds like simple clipping to me. Don't forget, the stock DCPP only has approx. 20 watts/ch. With average efficiency speakers, it's not that hard to push the amp beyond it's happy place.

jeff
Yea, I suppose that's it. I hadn't really experienced that quite so dramatically before but then I don't often listen to tracks with that much low bass so hot in the mix. I wasn't listening that loud. I guess I should be getting a little more than 20wpc using 6.6K iron (but not enough to make a significant difference).

Anyway, still pleased as punch
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Old 6th February 2013, 05:03 AM   #1384
rknize is offline rknize  United States
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Quote:
Originally Posted by mfaughn View Post
Yea, I suppose that's it. I hadn't really experienced that quite so dramatically before but then I don't often listen to tracks with that much low bass so hot in the mix. I wasn't listening that loud. I guess I should be getting a little more than 20wpc using 6.6K iron (but not enough to make a significant difference).

Anyway, still pleased as punch
Your DCPP is in better shape than mine. After all that hot-rodding at 80+WPC it went back into a box and has been sitting there since.

I haven't been on the forum as much lately, so I am not up to speed on your build. What OPTs are you using? I wonder if you opted to connect the GFB or not? Maybe it would help some if your speakers are difficult to drive at those frequencies.
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Old 6th February 2013, 10:12 AM   #1385
roline is offline roline  United States
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I'm using a total of 570u in the B+ at 460V. I have an excellent sustained low end capability with 6GV5 tubes in one amp and 6LB6 tubes in the other. I'm also using 6.6KRa hammonds, a set of 40 watt and a set of 60 watt in the larger amp. The 6.6 K iron runs longer in class A power than 4.3k iron and sounds sweeter with less feedback.
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Old 6th February 2013, 10:43 AM   #1386
mfaughn is offline mfaughn  United States
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GFB is hooked up. My iron is 6.6K from a Knight kit using a Mullard 5-20 circuit. At one point I think I figured out that they were made by either Central Transformer Company or Quality Transformers & Coil Co. (both Chicago companies).

It just occurred to me that before I get everything settled and buttoned up I could try out a different set of iron with it just to see how they sound. I've got some iron from an HK amp that used 7355. Supposed to be pretty good stuff. Primaries are around 4.3K. Hmmm. Maybe...
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Old 3rd May 2013, 05:42 PM   #1387
6L6 is offline 6L6  United States
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A quick question for the really smart people -

My C30 (in the B+ regulator circuit) appears to be bad. It is a 10uF 450V.

Can I replace it with a 22uF 450V? I have a few on hand, or should I wait and order the 10uF? I'm not entirely clear on what that capacitor does, and don't want to mess anything up.

Click the image to open in full size.
(image from P.Millett website)
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Old 3rd May 2013, 05:58 PM   #1388
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Quote:
Can I replace it with a 22uF 450V?
Yes. The cap is the active element in a ripple filter / capacitance multiplier. The larger cap will make the B+ come up a bit slower, which should not be a problem.
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Old 3rd May 2013, 06:08 PM   #1389
6L6 is offline 6L6  United States
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That was really quick! Thanks George!!

And thank you for explaining what that part of the circuit is. I really appreciate it.
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Old 5th May 2013, 04:56 PM   #1390
6L6 is offline 6L6  United States
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While I had the amp apart I replaced C30, D9 (which was bad) and Q2. The PSU hum, caused by the faulty regulator is now gone! Hooray!

It's still a bit hummy, (on the outputs) but much better. Trying to determine what that is...
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