Bottlehead Forum

General Category => General Discussion => Topic started by: xcortes on February 12, 2012, 05:33:57 AM

Title: What I'm up to
Post by: xcortes on February 12, 2012, 05:33:57 AM: Many projects on this side:

I purchased a NOS Panasonic Strain gauge cartridge. I've designed and started building a mega preamp for it using 437A tubes. All regulated and with four MQ pieces of iron in the PS. Per channel, of course!

I've started preparing to build an all SET OTL system with the 800 Philips widerange drivers and Ionovac tweeters (Ha Doc, how about this project for them). Still need to get high impedance woofers. I'll start with modifies Cracks to prove the concept before building 6c33 amps.

I'll install switches to short the primaries of my six amps (and the 5 in the HT too).

I'll rebuild six amps as low power DC 300Bs for a friend to demo his commercial horns at RMAF in October.

I'm planning a system office with Jordan minimonitors and Aurum Cantus tweeters with Griffin's design but with pllxos and SETs.

And finally. I've been known for trying things outside the BH world in the past. This time I purchased an EAR amp to use with my Quads. 32 watts of pp class a triodes sans feedback. So far the combination is magical. Now I know why Tim de Paravicini is famous and where the Quads reputation comes from. If I didn't know better I'd say this amp was SET and designed by PJ!

BTW Doc, you said the Quads highs were like plastic. Well, you were being nice, 'cause the mids sound plasticky too. But what they do they do very, very nicely.

Good Sunday all!
Title: Re: What I'm up to
Post by: Jim R. on February 12, 2012, 05:48:35 AM: Xavier,

Wow, lots of cool projects in the works there. If you come to RMAF, let us know -- would love to meet you in person.

Let us know how things progress -- that's a pretty ambibitious list of projects there :-).

-- Jim
Title: Re: What I'm up to
Post by: xcortes on February 13, 2012, 05:21:23 AM: Already changing the plan. I have an unused Seduction that can be modified for the Strain Gauge cartridge. Not enough current on the PT to bias the cartridge so I'll do it with batteries. But SR.

Sure thing about RMAF Jim. I'd love to be there. But October looks very complicated to me both in terms of work and personal. We shall see.
Title: Re: What I'm up to
Post by: saildoctor on February 13, 2012, 05:38:43 AM: Hi Xavier- I don't know if this info is any use to you, but I just got through modifying my seduction to use a gas reg tube and with bridge rectification/ choke input I have the PT1 drawing about 25ma and so far seems stable. How much current would it take to bias the cartridge?
Title: Re: What I'm up to
Post by: xcortes on February 13, 2012, 05:43:49 AM: Hi Kerry, Yes, I saw your post. Good Job! I'd be needing at least another 4mV (ideally 5mV) per channel. A 3mV C4s (plus its biasing diodes). You did go to 30mA, right?

I posted a dedicated thread here:

http://www.bottlehead.com/smf/index.php/topic,2629.0.html (http://www.bottlehead.com/smf/index.php/topic,2629.0.html)
Title: Re: What I'm up to
Post by: Grainger49 on February 13, 2012, 06:20:55 AM: Xavier,

I'll be interested in hearing about SET 6C33C output transformers. I have a pair and have been thinking about a scratch build. My problem is the transformers. Surely it should be Parafeed, right?

BTW, Jim Griffin lives about 1 1/2 hours away from me. I spent a wonderful afternoon listening to all sorts of fascinating designs in his basement. A very nice guy!
Title: Re: What I'm up to
Post by: xcortes on February 13, 2012, 06:27:45 AM: Hi Grainger. I'm actually thinking about OTL amps with these. I purchased a pair of 800 ohm Philips "fullrangers" to build an OTL SET system.
Title: Re: What I'm up to
Post by: Grainger49 on February 13, 2012, 06:31:09 AM: Well, I read that wrong! Thanks!
Title: Re: What I'm up to
Post by: Paul Joppa on February 13, 2012, 10:27:55 AM: Quote from: Grainger49 on February 13, 2012, 06:20:55 AM
Xavier,

I'll be interested in hearing about SET 6C33C output transformers. I have a pair and have been thinking about a scratch build. My problem is the transformers. Surely it should be Parafeed, right?

BTW, Jim Griffin lives about 1 1/2 hours away from me. I spent a wonderful afternoon listening to all sorts of fascinating designs in his basement. A very nice guy!
Magnequest makes a suitable transformer. PB (Caucasian Blackplate) built an amp around it a while back.
Title: Re: What I'm up to
Post by: Grainger49 on February 13, 2012, 10:47:10 AM: Paul, Thanks!
Title: Re: What I'm up to
Post by: saildoctor on February 13, 2012, 04:43:31 PM: Unfortunately I did not try out 30ma. I decided to not push my luck and set the C4S feeding the rest of the preamp at 25ma. :) After awhile I might try bumping it up a little more.
Title: Re: What I'm up to
Post by: Paul Birkeland on February 18, 2012, 07:30:00 AM: Man, you are going to be busy this year!!! The 6C33 is a decent little tube, just be prepared to have a giant chassis if you use Mikey's iron in your amp, those chokes are very large.
Title: Re: What I'm up to
Post by: xcortes on February 18, 2012, 07:39:17 AM: I was going to use these with the 800 ohm speakers so no iron. But they arrived destroyed so the project is on hold now!