Recent Posts

51

Tube Amp Building - Tweaks - Repairs / Re: I think I had an idea for a "new PPIMV" that represent a Constant Load for PI

« Last post by acheld on December 06, 2025, 10:22:18 am »

I like the idea but am skeptical that the pots would be so precise.   But maybe they are.  I guess linear pots would be close enough.

Interesting!  Let us know how that works . . .

52

Tube Amp Building - Tweaks - Repairs / Re: Please do not use VPN's

« Last post by acheld on December 06, 2025, 10:17:58 am »

Thanks for sharing that info.  Helps put things in perspective.

53

Tube Amp Building - Tweaks - Repairs / Re: Can you tell the the frequency of a tone control is by it's resistors and caps ?

« Last post by Rontone on December 06, 2025, 09:31:57 am »

Would Tone Stack Calculator help?

https://www.duncanamps.com/tsc/

Edit: There is also TSC online through browser here - https://www.guitarscience.net/tsc/info.htm?

There is a Fender tonestack in there that can be altered to these values, and you can study the frequencies on the graph

The schematic shows a 10nF cap for the bass cap in the tonestack? That has quite a large drop from the original 100nF

54

Tube Amp Building - Tweaks - Repairs / I think I had an idea for a "new PPIMV" that represent a Constant Load for PI

« Last post by kagliostro on December 06, 2025, 09:14:08 am »

Previously I was thinking to use a pair of SF using two mosfet, one for each brench of the PI but this thing seems to be way simpler

the difficult thing was to find a 4 ganged pot with the correct resistance value, but it is on the market

the idea is an L-PAD/PPIMV



Franco

55

Tube Amp Building - Tweaks - Repairs / Re: Testing Bad Filter Cap with a scope for 120HZ hum

« Last post by wsscott on December 06, 2025, 09:08:17 am »

Interesting, although I removed the ground wire connection on the RCA Reverb Input jack, I still have reverb and I can control it on/off with the foot pedal.  How is that?

As to the hum, with the Reverb On, the hum is louder than when it is turned OFF, but probably not as loud as before when the jack was still wired to the buss ground.

The Reverb Intensity pot increases the loudness of the hum, as well as the amount of Reverb.

I haven't checked the scope for 120hz signal readings, but I assume its still there in the same places as before, since that's the hum I'm hearing--I think.

So I would say its better, but I would like it to be quieter--if that's achievable with this circuit.

56

Tube Amp Building - Tweaks - Repairs / Re: 2 questions- Tube values and pot value

« Last post by pbman1953 on December 06, 2025, 08:18:22 am »

I had a chance go back and forth with the 680 & 1500. I left the 680 because compared the 1500 sounded cloudy, where the 680 was crisper.

57

Tube Amp Building - Tweaks - Repairs / Re: Please do not use VPN's

« Last post by EL34 on December 06, 2025, 08:07:44 am »

There are some days I have 10 attempt's to join the forum from known IP's in the spammer database .

Russia, Ukraine and Netherlands are the most frequent.
TOR exit nodes can be anywhere in the world and they use those also.

I have people try to join that flat out are using a VPN even though it says in the agreement to not do that.
Many of the attempts are hacker bots
Once someone fills in the anti spam join questions, the hacker bot can spam membership join attempts

I have to constantly change the memberships join question answers once the bots are setup with the correct answers

It's a daily battle
Just be thankful someone is actually on top of the situation so we can all have a safe place to come and enjoy amp discussions

58

Tube Amp Building - Tweaks - Repairs / Re: Please do not use VPN's

« Last post by shooter on December 06, 2025, 07:55:44 am »

Unfortunately "digital warfare" is here to stay, fortunately we have the best gremlin fighters in the world here 

the only social media platform I'm on is a STRICT Constitutional 1st Amendment site, so the whole world hates the place since you can freely say things that polite society hates.  The IT-guys have to block entire country IP addresses just to stem the attacks.  The owner regularly posts letters from guvmints demanding information on users, his reply is always a nice letter telling them to "pound sand" 


that might be something to watch for behind the curtain here, 95% of all spam came from just 2 places, India and Israel

59

Tube Amp Building - Tweaks - Repairs / Can you tell the the frequency of a tone control is by it's resistors and caps ?

« Last post by pbman1953 on December 06, 2025, 07:53:31 am »

The book that came with this amp doesn't list the frequencies for it's main tone knob set. The bass control  has a main roll in this amp. If it's all the way down there isn't any sound. My question is if you can tell what the frequencies are based on what Fender used for the resistors and caps?


I'd like to lower the frequency of the Bass control, if possible.


Thanks

60

Tube Amp Building - Tweaks - Repairs / Re: Please do not use VPN's

« Last post by EL34 on December 06, 2025, 07:22:15 am »

Sorry, I can't control what the UK does
Maybe you should get rid of that Lefty government who prosecutes people for on line comments and a horrible immigration policy?

It's way more important to keep the forum free from spammers and Hackers
It's a constant battle keeping them out

Do you guys not remember what happened to other forums that were attacked?