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Old 2nd December 2010, 03:57 PM   #201
djn is online now djn  United States
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Hi D, I will be tri amping with my TMOTL so is there any freq range that you would say sounds better than others?
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Old 2nd December 2010, 06:04 PM   #202
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Hi D, I will be tri amping with my TMOTL so is there any freq range that you would say sounds better than others?
In general I find the amp a bit to rich in the highs for my taste. I will report back when I do the 12AT7 switch to see if that helps.
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Old 2nd December 2010, 06:35 PM   #203
djn is online now djn  United States
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Thanks D. I run the big Heils for tweets crossed at 7khz so I don't really need any more sizzle up there. I run a midrange tractrix horn with the JBL 2441 CD from 500hz to 7khz and the Lambda TD15 from 500hz on down.

I am building three amps at the moment and trying to figure out which one will be the best match for the three drivers. I suppose I will find out after they are all built.
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Old 2nd December 2010, 08:43 PM   #204
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Seems this project is off to a bumpy start. Out of 4 6C33C tubes received, 1 has a broken glass envelope and the getter is completely gone, one has an almost black getter, and two look OK. I have several more on the way but don't expect them for several weeks.

No standard steel Hammond chassis this time. I'm putting this in a custom homemade chassis with aluminum top plate and oak sides. This is going to be a work of art. And BIG. 4 output tubes per channel will be accomodated. The aluminum top plate should arrive today so I can lay out the components and start drilling holes soon.
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Old 2nd December 2010, 08:55 PM   #205
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In general I find the amp a bit to rich in the highs for my taste. I will report back when I do the 12AT7 switch to see if that helps.
I like the way you breadboard the project, building on an open plywood platform. Easy to make changes and prove a design before committing to a nice chassis with a project that doesn't sound right.

Wish I had learned that years ago, but that's how I do it now.

Stuart
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Old 3rd December 2010, 02:49 PM   #206
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Originally Posted by sepolansky View Post
I like the way you breadboard the project, building on an open plywood platform. Easy to make changes and prove a design before committing to a nice chassis with a project that doesn't sound right.

Wish I had learned that years ago, but that's how I do it now.

Stuart
I agree. I like the test setup. Very easy to tweak the amp that way. I need to start doing that.

Very interesting amp. Reading all about it now.
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Old 5th December 2010, 11:11 PM   #207
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Well not to be a downer but I am just about to abandon this OTL as the Glen Orr 6AS7 OTL I just built blows it away.

I have been listening to the Glen Orr amp now for 3 days an it is as close to my rebuilt NYAL OTL3's in sound as any other otl I have built has come to sounding as nice and in some ways better. Great stage, solid bass nice mids. Mellow sound but clean and under control. I am currently using 5 NOS NIB GE 6AS7GA and they do sound better then my NOS NIB GE 6080's but not by much. If you want a nice DIY OTL I suggest you build this amp.
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Old 6th December 2010, 02:06 AM   #208
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Not a downer - appreciate the opinions. I'm committed to completing the T Mellow OTL but after that I may try the other one. All parts are in except the tubes
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Old 22nd December 2010, 12:38 PM   #209
nafunga is offline nafunga  United Kingdom
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Default Tim Mellows OTL with LESS than 6C33C's!

Hi All,
Recently finished my variant of Tim Mellows OTL. I've used 6C41C's in place of 6C33C's as, for me, around 6W is sufficient and I don't need all the extra heat. (although, this weather?!) The circuit is exactly as Tim did it except that I've used 500mA meters in place of 1A. I run the 6C41C's at 100mA not 200mA and the HT fuses are 500mA too. One thing I did change was the working voltage of C18 in the -430v section as 250v was exceeded. So a 385v rating was used. After a weeks use, the amp. has settled down with bias and balance pot settings remaing stable - and it sounds - GOOD too! I realise that using the 6C41C's compromises the output impedance and damping factor but it still sounds very nice compared to other more conventional amps I have built. My son in law was so impressed that he wants me to build him the original version to (possibly!) replace his 300B amp I built him a few years back! All in all, a very nice sound, thanks to Mr Mellows unusual (and rather novel circuitry - who'd have thought of a dc coupled driver for 6C33C's using an EF86!!) Picture attched.

'Happy Christmas@

David.
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File Type: jpg OTL 004.jpg (136.8 KB, 495 views)
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Old 22nd December 2010, 12:46 PM   #210
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Beautiful. Well done.
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