Search found 1839 matches

by roberto
Mon Jan 23, 2023 8:05 am
Forum: Technical Discussion
Topic: LND150 replacement options
Replies: 29
Views: 2741

Re: LND150 replacement options

I like the IRF style devices as a loop follower. On the return side the LND-150 is great. Unfortunately, most suppliers are talking late 2023 for stock again. I agree, nowadays there are probably better options than the IRF series, but as a general concept I prefer to have a device that can handle ...
by roberto
Mon Jan 23, 2023 7:57 am
Forum: Technical Discussion
Topic: LND150 replacement options
Replies: 29
Views: 2741

Re: LND150 replacement options

That particular device is going down the way of the dinosaur, so it may not have been the best example. So you call that prehistoric when you in 2023 propose a very dangerous schematic with an IRF820 that is more than 40 years old? :D Don't make your bitterness hide your brain. A device can either ...
by roberto
Sat Jan 21, 2023 11:45 pm
Forum: Technical Discussion
Topic: LND150 replacement options
Replies: 29
Views: 2741

Re: LND150 replacement options

They do operate very well when used in a cascode configuration, however. LND150's also work very well when used in cascodes. If two devices are needed for the return, I absolutely drive them from the source through a pmosfet and give feedback from drain to the gate to triodize the curves. Sounds wa...
by roberto
Sat Jan 21, 2023 11:41 pm
Forum: Technical Discussion
Topic: LND150 replacement options
Replies: 29
Views: 2741

Re: LND150 replacement options

Why not? They work fine as source followers as do a wide array of other devices. Their small size and sufficient no-heatsink wattage make them ideal for source followers. There are other components that do source following way better than them, EG the STU9HN65M2 able to strongly drive even heavy lo...
by roberto
Sun Jan 15, 2023 9:11 pm
Forum: Technical Discussion
Topic: LND150 replacement options
Replies: 29
Views: 2741

Re: LND150 replacement options

I would not use then on the buffering send stage of the loop, instead other choices like the very old IRF820 or modern upgrades are better. For the return stage both a DN2540 or a DN3545 can be used. Check an high voltager depletion mosfet on major sites and pick the one available, then play with it...
by roberto
Fri Jan 13, 2023 1:39 pm
Forum: Technical Discussion
Topic: Output Transformer primary impedence
Replies: 3
Views: 417

Re: Output Transformer primary impedence

It would most probably give too much 2nd harmonic. You could try it and play with the PSU to lower the voltage, increase the current through the tube and find a sweet spot for that tube. Another option could be to install an EL34 to fully use the 5k instead of the 8k, if the PT can give enough curre...
by roberto
Wed Jan 04, 2023 11:25 pm
Forum: Technical Discussion
Topic: 10K screen grid resistor?
Replies: 12
Views: 991

Re: 10K screen grid resistor?

It could be used as an "effect" on the power amp, causing strong compression when the secondary emission takes place.
Another reason could be that they developed the amp using tubes with weak screen grids, so they protected them this way.
by roberto
Sun Jan 01, 2023 6:30 pm
Forum: Technical Discussion
Topic: Single Ended Amps - Opinions
Replies: 91
Views: 11141

Re: Single Ended Amps - Opinions

Before the coupling cap.
by roberto
Fri Dec 30, 2022 7:09 pm
Forum: Technical Discussion
Topic: Cathode follower for compression
Replies: 11
Views: 1085

Re: Cathode follower for compression

Thanks, why back to 100K at higher volumes? What you do by lowering the 100k to 47k is exacerbate the compression of the stage at lower volumes. When you crank the volume, you will find too much compression, and need to go back to 100k (or at least increase this value). Please note that this is val...
by roberto
Thu Dec 29, 2022 1:36 pm
Forum: Technical Discussion
Topic: Cathode follower for compression
Replies: 11
Views: 1085

Re: Cathode follower for compression

I'm not sure we are talking about the same mod because I'm not familiar with the specific reference, but I modded some Bassman in the past by lowering the cathode follower resistor from 100k to 47 to 68k depending on the taste of the owner of the amp. It was switchable with the amp not running (beca...
by roberto
Mon Dec 19, 2022 9:01 pm
Forum: Technical Discussion
Topic: Hum neutralizing circuit
Replies: 11
Views: 1434

Re: Hum neutralizing circuit

It's an old idea reproposed 10 years ago on tubecad:
https://www.tubecad.com/2012/05/blog0229.htm

Image
by roberto
Mon Dec 19, 2022 10:46 am
Forum: Technical Discussion
Topic: CUSTOMAUDIO OD100
Replies: 20
Views: 2627

Re: CUSTOMAUDIO OD100

Interesting, so it still has the 2.7K/.22uF bypass on the 3rd stage? I thought the standard had less gain than the OD100SE. One of the lead channel I liked most was developed together with a friend on the CAE 2nd and 3rd cold stages with partial bypass. First two coupling caps were (IIRC) scaled do...
by roberto
Fri Dec 16, 2022 12:13 pm
Forum: Technical Discussion
Topic: CUSTOMAUDIO OD100
Replies: 20
Views: 2627

Re: CUSTOMAUDIO OD100

bepone wrote: Fri Dec 16, 2022 9:20 amto me looks like LM338K, regulator for 12V DC for the heaters..
Yes, it's for DC heaters (see connections on its right).
by roberto
Thu Dec 15, 2022 3:42 pm
Forum: Technical Discussion
Topic: CUSTOMAUDIO OD100
Replies: 20
Views: 2627

Re: CUSTOMAUDIO OD100

I copy here some comments written by bnouille (Bruno Durand IIRC): OD100 SE+ is just basically the same as the 3+ .Same clean and lead channel .The so called "crunch" channel is just the lead channel with one R value lowered for less gain somewhere ( can't remember which one cause it's been a long t...
by roberto
Thu Dec 15, 2022 10:51 am
Forum: Technical Discussion
Topic: CUSTOMAUDIO OD100
Replies: 20
Views: 2627

Re: CUSTOMAUDIO OD100

I've now seen you have a site and you build Dumble-like amps.

I think the best option for you is to ask directly to a forumer called "Husky" (should be here too) for an official reply.
It can also be a better reference for the customer, even more if he is a tournist.