Search found 803 matches

by Thermionic Idler
Mon Jan 17, 2022 3:35 pm
Forum: Everyones Projects
Topic: Single-Ended Pentode Redux
Replies: 72
Views: 1249

Re: Single-Ended Pentode Redux

Steve - I'd be interested on your thoughts on the sound of the JJ 6V6 versus the old stock ones - I've only ever used old stock in the 6V6 driver position of my 300B's, but have been pondering trying some new JJ's as I think one of the ones in there at the moment is going weak. Right! JJ 6V6S are v...
by Thermionic Idler
Sun Jan 16, 2022 7:30 pm
Forum: Everyones Projects
Topic: Single-Ended Pentode Redux
Replies: 72
Views: 1249

Re: Single-Ended Pentode Redux

I have a pair of NOS, French Mazda 6V6 from the 1950s in the amp at the moment and they are lovely. I have 2 NOS black glass Brimar and 2 grey glass Sylvania, plus a pair of new production JJ 6V6S, so plenty to be going on with. A nice, sweet and detailed 4 and a bit Watts or so, vs the 9..ish Watt...
by Thermionic Idler
Sun Jan 16, 2022 7:26 pm
Forum: Everyones Projects
Topic: Single-Ended Pentode Redux
Replies: 72
Views: 1249

Re: Single-Ended Pentode Redux

I only have a few Brimar 6V6s but would like to hear how the cheap Russian ones sound. Pretty lifeless when used as 300B push-pull drivers, I bought a matched quad and took them out after a day, it was like the Dementors had descended. I currently have old-stock Tung-Sol, much better. That said, at...
by Thermionic Idler
Sun Jan 16, 2022 7:14 pm
Forum: Everyones Projects
Topic: Single-Ended Pentode Redux
Replies: 72
Views: 1249

Re: Single-Ended Pentode Redux

Yes, I think the 6V6 SEUL with Schade feedback is certainly a definite candidate for putting in a proper enclosure. That's three amps then: 2W DHT SET 4.5W 6V6 SEUL 60W solid state with built-in phono stage. Quite a productive and enjoyable few weeks. Lovely. Valve buffer for the NVA thingy anyone?...
by Thermionic Idler
Wed Jan 12, 2022 6:27 pm
Forum: Beginners
Topic: Two-chassis phono stage - grounding question
Replies: 3
Views: 177

Two-chassis phono stage - grounding question

So I have one metal chassis containing the phono stage circuitry with step-up transformers, and there will be another containing the power supply. An umbilical cable will connect the two with the ±12V supply. The chassis with power transformer and power supply board will obviously be connected to sa...
by Thermionic Idler
Wed Jan 05, 2022 4:41 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

So I've decided to bring this thread largely to a close for now. I'd originally decided to combine the projects into one thread because I was working on them simultaneously, driven by this mad idea I had to integrate the power systems together. As we know, that hasn't worked out exactly as I'd expec...
by Thermionic Idler
Tue Jan 04, 2022 6:44 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

More listening this afternoon - I have to say this phonostage is a keeper, it's starting to bed in now and is sounding more and more musical and detailed - with all the details in their correct place. I really cannot recommend this highly enough - the PCB is priced reasonably, although with Pete bei...
by Thermionic Idler
Sun Jan 02, 2022 5:13 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

Not sure why measuring the DC resistance would help you any. Correct, it wouldn't, because I'm an idiot. I just started responding by writing out the test procedure and then realised in neither case would I be measuring the coils in parallel instead of in series. Even more duh! Maybe I should just ...
by Thermionic Idler
Sun Jan 02, 2022 2:47 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

I think the order the lead out wires gives a good hint as to the phase. Or at least in the ones I have had they do. Put them in series and measire the voltage across the two ends. Oh yeah, I don't really need a scope to do that do I... duh! :oops: :lol: Actually, measuring the secondary coil resist...
by Thermionic Idler
Sun Jan 02, 2022 2:31 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

Thinking of upgrading the linestage transformers to Toroidy audio-grade ones when refitting the previous power supplies, as it looks like I *just* have enough space and they seem like good value. I really wish they would indicate phase with their wiring colours though - the dual rail supply needs a ...
by Thermionic Idler
Sat Jan 01, 2022 7:25 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

I'm still not clear-headed after last night, but I'm a bit confused by the behaviour around C3. Just looking at it (I've not emulated anything), but C3 charges through the 2 x 150R resistors and discharges through the 2 x 1N4148s + the resistors, which means it won't do anything much to the Vcc lin...
by Thermionic Idler
Sat Jan 01, 2022 5:11 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

Placed an order to AMB for the PCB and some of the parts for the sigma22 supply, and Digikey for the rest - where it is currently -32C! :bigsmurf: I specced mostly Nichicon UFW's for the electrolytics, but there are a couple of UKW's in there as well. The board will be configured to put out ±12V. I'...
by Thermionic Idler
Fri Dec 31, 2021 7:11 pm
Forum: Everyones Projects
Topic: Millett LR + TP Opus + AMB α24 reboot
Replies: 150
Views: 8248

Re: Millett LR + TP Opus + AMB α24 reboot

Have the batteries got any caps across them? There is this odd idea that seems to regard batteries as perfect voltage sources. That may be true if you are powering a bulb and measuring with a constant load. Well, there is a large 4700uF cap across the supply lines from the battery packs to the Sile...
by Thermionic Idler
Fri Dec 31, 2021 5:34 pm
Forum: Beginners
Topic: Toroidal transformer interference
Replies: 1
Views: 225

Toroidal transformer interference

Take a 15VA toroidal transformer with mains supplying the primary, and draw a certain amount of power through it within its design spec. Take a 150VA toroidal transformer with the same mains supplying the primary, but draw the same power, at the same current and voltage as you did for the 15VA trans...