Search found 567 matches

by RhythMick
Sat Aug 10, 2019 12:49 am
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

I'm a ways behind you in terms of really developing my understanding of the behaviour of my amp in all conditions. However my ears have told me similar things. I prefer the sound of interstage coupled, all DHT, PP architecture. I prefer to minimise caps in favour of iron and I instinctively avoid si...
by RhythMick
Fri Aug 02, 2019 10:01 am
Forum: Everyones Projects
Topic: Guitar Amp for Granddaughter
Replies: 22
Views: 2728

Re: Guitar Amp for Granddaughter

Plus I'm sorry but I haven't heard any digital amp sound anything like as good as a proper valve amp. Call me old fashioned. No, but they can sound 95% as good as 20 amps and 20 cabs, and a floor full of pedals, are easy to carry to gigs, can sound good at both bedroom practice and playing with dru...
by RhythMick
Fri Aug 02, 2019 8:01 am
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 332
Views: 34221

Re: The Nemesis 813 PP Amplifier

OK, so one side ( 'E' ) is connected to the 440R resistor ( or a suitable value for 4P1L's ) and you can connect one Lehane supply across E-F ? I think things have moved on a bit from that post due to Paul's comments. I will need 2 Lehane regs but quite how I use them is up for grabs at the moment....
by RhythMick
Thu Aug 01, 2019 10:26 pm
Forum: Everyones Projects
Topic: Guitar Amp for Granddaughter
Replies: 22
Views: 2728

Re: Guitar Amp for Granddaughter

Thanks Nick/Ed, That Blackstar looks awesome :D @Ed I can’t justify building something when that Blackstar exists, so I guess that’s that. Bloody digital! Is nothing sacred? :lol: Sure you can. You'd enjoy the design and build, and how much better to be able to give your granddaughter a hand built ...
by RhythMick
Tue Jul 30, 2019 12:56 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

I would also be worried about those SMPS directly connected to the TX that serves the GM70 bias. Aren't they really noisy?
by RhythMick
Sun Jul 28, 2019 10:07 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Just a thought Steve, but with my transformer coupled all DHT PP amp I started with shared cathodes and found a big improvement from switching to separate (bypassed) cathodes. Maybe something to try one day, if you do I'd be interested in the result.
by RhythMick
Fri Jul 26, 2019 8:02 am
Forum: Everyones Projects
Topic: Guitar Amp for Granddaughter
Replies: 22
Views: 2728

Re: Guitar Amp for Granddaughter

Sounds great and is a project I'm interested in myself. Most amps are way over powered and as a result never get used in that wonderful sweet spot where the output stage starts overdriving. That's where the brown sound lives. I have it on my list to create a flea powered amp. I'd be very interested ...
by RhythMick
Wed Jul 17, 2019 9:02 am
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Well, if its regulated, one end will be the emitter of a transistor, the other the ground or a sense resistor for the supply. Remember Mark found that he could hear the cap in the integrator. It may also be a case that connecting the resistor may alter the conditions the DC supply sees. Both intere...
by RhythMick
Mon Jul 15, 2019 9:15 am
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

izzy wizzy wrote:
Mon Jul 15, 2019 7:55 am

I might try the different sides of grounding the fils...
I'd be interested if there's any difference, assuming the bias is kept constant. I only tried the connection to the positive.
by RhythMick
Sun Jul 14, 2019 10:25 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

You'd have been pulling an extra half amp through the DC boards as well remember, assuming you run 1 board per valve. An extra amp if they are in parallel.
by RhythMick
Sun Jul 14, 2019 10:23 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Surely you're going to try both and tell us which sounds best...?

:o :) :lol:
by RhythMick
Sun Jul 14, 2019 8:38 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Re -100v on the grid. Does that become -80 (or -120) if we take the filament voltage into consideration ? Would filament bias be a STUPID suggestion ? :oops: Filament bias would be one hell of a heater lol I've seen datasheets refer to setting the bias relative to the midway point. I attached the c...
by RhythMick
Sun Jul 14, 2019 5:04 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Once Steve tells us what Ia he's aiming for I can recalculate, but let's say for the sake of argument it's 80 (based on nothing more than Steve's "factor of 10" comment). You'd still need to choose relatively high virtual cathodes to make it practical. I multiply the expected dissipation by 4 and re...
by RhythMick
Sun Jul 14, 2019 4:22 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Paul Barker wrote:
Sun Jul 14, 2019 4:15 pm
Not relevant for our use of the valve. Look at the characteristic curves.
Ok fair enough. What mA would you expect through the cathode?
by RhythMick
Sun Jul 14, 2019 4:00 pm
Forum: Everyones Projects
Topic: GM70 PP
Replies: 151
Views: 11641

Re: GM70 PP

Is this the wrong datasheet? I've never used a GM70.
Screenshot_20190714_151710.jpg