Search found 567 matches

by RhythMick
Sun Oct 27, 2019 5:53 pm
Forum: Everyones Projects
Topic: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Replies: 1102
Views: 131101

Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

I think you're right that the silicon type don't need compound, but the datasheet will tell you.

If you need it I have 2 spare syringes of compound, happy to send you some, no idea why I bought three.
by RhythMick
Sun Oct 20, 2019 6:58 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11585

Re: GM70 PP

What model Lundahl choke, where in the filter chain and how is it wired?
by RhythMick
Sun Oct 20, 2019 6:56 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11585

Re: GM70 PP

For me I think having the bias supply absolutely ripple free as far as possible is paramount. Irrelevant for me as it happens as I've switched to cathode bias, but when I had fixed bias I went for separate choke filtered PSU right back to separate tx secondary winding. I prioritised the smoothing of...
by RhythMick
Tue Oct 08, 2019 10:28 pm
Forum: Valves
Topic: Decoupling...
Replies: 53
Views: 8203

Re: Decoupling...

Ok but if you decide you'd like the chokes let me know. I have audio note probably around 20 or so sat doing nothing.
by RhythMick
Tue Oct 08, 2019 9:28 pm
Forum: Valves
Topic: Decoupling...
Replies: 53
Views: 8203

Re: Decoupling...

Foot in mouth time. I think I see what is being said. Say using my amp as an example, at idle the HT is 1000V @ 180mA = 180W. At say a power out of 30W the HT delivers the 180W plus 30W so the HT bounces around to the dynamics of the music not so much to the frequency changes but a little as the lo...
by RhythMick
Sun Oct 06, 2019 11:03 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

Well doesn't time fly. Our new arrival is developing nicely and is already outshining its older PP sibling. Very surprising - I only built this SE amp as a quick and easy rough build spare amp while I brought my PP up to the spec of Geoffs, and because I thought it was a shame to have the kit in a c...
by RhythMick
Sun Sep 29, 2019 6:18 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

Andrew wrote:
Sun Sep 29, 2019 6:12 pm
All working ok now, dare I ask?
All stable and silent (unless I'm really determined to stick my ear next to the Lowthers). The sound is awesome. Many thanks. Definitely bring this to the next meet.

The transformers I have in now are ok but borderline. I plan to swap out next weekend.
by RhythMick
Sun Sep 29, 2019 11:00 am
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

Of course. Rating 6.3v at 3A. At lower load the voltage will be a bit higher.
by RhythMick
Sat Sep 28, 2019 10:13 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

To select the TX secondary voltage required I worked on a 4v regulation loss from the peak TX voltage, so for a 6.3v RMS secondary... 6.3 x 1.414 - 4 = 4.9 ... this would be right on the edge for a 300B requiring 5v, which is why I went with a 7v. I do have a Hammond 266M12 which would give 2x 6.3v ...
by RhythMick
Sat Sep 28, 2019 7:57 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

It's it even worse than that, or am I over thinking this now?

Peak current flow will be when the secondary is at peak voltage? If that's true then peak VA for a 7v secondary with an average current draw of 1.2A will be...

7V x 1.414 x 1.2A x 1.6 = 19VA

Is that right?
by RhythMick
Sat Sep 28, 2019 5:52 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

In terms of expected power lost through heat on the boards, I was working on (7 x 1.414 - 5) x 1.2 which is 5.9W. I get that the RMS voltage of 7v is 9.9v which (less drop over the Schottky diodes) goes into the cap filter. I guess what I wasn't taking into account was the peak current draw to refil...
by RhythMick
Sat Sep 28, 2019 4:02 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

I find this helpful https://www.hammfg.com/electronics/transformers/rectifier Your 1.2A DC equates to about 2A AC when bridge rectified into a cap. Cheers, Stephen Ok thanks both. I was calculating required VA based on transformer voltage x valve current. I'll read that page properly later but it l...
by RhythMick
Sat Sep 28, 2019 1:16 pm
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

Good result. What were the toroids, so we can avoid them? https://uk.rs-online.com/web/p/toroidal-transformers/1243873/ They are spec 1.78A per secondary. The 300B draw 1.2A so should be fine. It's possible that the fault is mine of course. I built the amp upside down and realised after the first w...
by RhythMick
Sat Sep 28, 2019 9:04 am
Forum: Everyones Projects
Topic: We are delighted to announce ...
Replies: 21
Views: 1954

Re: We are delighted to announce ...

It's been a bit of a roller coaster with this SE amp over the past couple of weeks. I initially had a weekend of glorious listening with friends (ignoring the underlying hum & buzz during the quiet passages), but on the Sunday evening the noises became pronounced and we reluctantly had to switch off...