Search found 16 matches

by Ken S
Mon Jun 26, 2006 12:03 am
Forum: Inductors
Topic: Choke for RIAA
Replies: 8
Views: 13291

Wow, sounds like this would take more technical know-how & time than I have. Ermm... Perhaps it'll be better if I went commercial.

Thanks anyway Dave. :D
by Ken S
Sat Jun 24, 2006 3:13 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

I think you owe it to yourself to give it a try. Above you mentioned that you were using a .04 gap for the 1:1's by this do you mean a .04 gap which is a .02 spacer (yellow). Since each core requires two spacers they add so two yellows gives you a .04 gap as read on the L vs. I plots. Hmm... Ok. Wi...
by Ken S
Sat Jun 24, 2006 2:00 am
Forum: Inductors
Topic: Choke for RIAA
Replies: 8
Views: 13291

Oh crap! I was hoping that you would've and that you could easily whip up a set. I'm willing to try something out, but I'm a total novice when it comes to RIAA compensation (How it works, what to listen for etc.), so the chances of me running around in circles is pretty high. I have personally never...
by Ken S
Sat Jun 24, 2006 1:42 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

Hey Ken, thanks for the input. did you ever try the Large 1:1 as a plate choke and cap couple to the output (parafeed)? I did try the 1:1 briefly as a choke., but then switched to a true 1:1 configuration, liked it immediately and never went back. :oops: I do remember that the low mid and mid mids w...
by Ken S
Fri Jun 23, 2006 2:33 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

I'm sorry; this has taken so long and also because I only managed to do the very minimal amount of bread boarding. I was hoping to do more in the future, but this has taken too long already and I'm not sure when I'll be able to get to it again. Here are the observed results. Small lam OPT with large...
by Ken S
Thu Jun 22, 2006 3:03 pm
Forum: Inductors
Topic: Choke for RIAA
Replies: 8
Views: 13291

Choke for RIAA

I've seen some circuits that use a choke and cap/resistor combo for RIAA ccompensation. What are the benefits to having the choke there? Indeed, whey even the need for one? I've seen similar circuits without the choke.
by Ken S
Sun Jan 22, 2006 5:31 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

The custom power transformers for the amps are due in about a week and hhopefully I'll get on to breadboarding soon after that.
by Ken S
Fri Dec 16, 2005 1:44 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

They come out at about 230 ohms.

When gapping the cores, you would use a shim on each of the lamination poles, ccorrect? So 1 choke would need 4 shims?
by Ken S
Wed Nov 16, 2005 6:45 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

Yep. I think the shum2 will be a better choice in terms of perfoemance and it'll also allow me some flexibility to try other drivers tubes, such as the 45 or even a low power PX4.
by Ken S
Fri Oct 07, 2005 8:54 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

Dave,

I didn't think it would be that troublesome. In that case, please leave the feedback winding then. Thanks.

Ken
by Ken S
Tue Sep 20, 2005 1:24 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

This is my proposed schematic. I've dashed the IT loading resistor & one connection on the OPT because I'm not sure if they are correct or necessary.

Image
by Ken S
Tue Sep 20, 2005 5:33 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

I can do that, but you might want to consider slipping some nickel in for the first 1:1 to mix it up a bit. So we are talking a nickel/amorphous mix? For the cathode feedback, how many dB are we talking about? Something small, say 5-8db? I could do up the following to give you a bunch of options to...
by Ken S
Mon Sep 19, 2005 6:02 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

Yep, this exactly what it is. You connect the tube's filament curcuit through a dedicated winding in the secondary to give you feedback. Generally accepted as a better option than running the feedback from one of the speaker output taps. Hi again, Do you mean "cathode feedback"? I have bui...
by Ken S
Mon Sep 19, 2005 4:58 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

You connect the tube's filament curcuit through a dedicated winding in the secondary to give you feedback. Generally accepted as a better option than running the feedback from one of the speaker output taps. DA30 looks vaguely 300B-ish in terms of characteristics (apart from lower plate dissipation)...
by Ken S
Mon Sep 19, 2005 4:12 pm
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

Ken has never designed an amp from scratch so lets encourage him over to the dark side. I'm not a total novice, but I tend to throw stuff together without any testing and just solving the problems as they occur. In looking at the curves, I'd look at operating the tube at ~325V 70ma with -80V bias. ...
by Ken S
Sun Sep 18, 2005 9:35 am
Forum: Transformers
Topic: DA30 Amplifier
Replies: 24
Views: 28133

DA30 Amplifier

Contacted Dave via email for some ideas a couple of days ago and now will transfer the discussions here. The DA30 tube Also called the PX25A which is a low mu (3.5) version of the PX25 (8 ish). At 500v on the anode it can provide 11w (A bit optimistic I think) of audio power from a 5-6k output trans...