Recent Posts

31

Tube Amp Building - Tweaks - Repairs / Re: 1968 Fender Vibrochamp AA764 Resto

« Last post by shooter on December 07, 2025, 08:13:18 am »

where you riding a Horse with no name when you stumbled on that Sun-baked beauty??


speaking of Sun, it's about time you give it a push back across the equator, bite chilly n dark up Norte'

32

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

« Last post by EL34 on December 07, 2025, 07:19:32 am »

I am not concerned with real members that post here
I am concerned with spammers that register on a normal IP and then a couple days later they use a VPN
I have plenty of those guys with zero post and no activity on the forum
Those guys get deleted
In your case Joel, You have 188 post
I doubt your are here to cause trouble

33

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 pbman1953 on December 07, 2025, 07:15:28 am »

I really appreciate everyone's help but let's take it from a different angle.


My amp uses a .1 and .047 cap for the bass circuit. An old Bassman uses a .1 and a .1. Does anyone know what the Bassman Bass knob frequency is? 


If I know that I can easily read the graph once I start entering different values

34

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

« Last post by kagliostro on December 07, 2025, 05:15:48 am »

A few years ago, we at DIYItalia stopped accepting registrations from abroad due to the high number of spammers.

But I understand that's not a good thing for EL34world. There's also an e-commerce section, and preventing customers from registering is inappropriate.

Franco

35

Tube Amp Building - Tweaks - Repairs / Re: 1968 Fender Vibrochamp AA764 Resto

« Last post by TIMBO on December 07, 2025, 04:22:32 am »

And cleaned

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Tube Amp Building - Tweaks - Repairs / Re: 1968 Fender Vibrochamp AA764 Resto

« Last post by TIMBO on December 07, 2025, 04:20:31 am »

Chassis stripped

37

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

« Last post by Joel on December 06, 2025, 11:58:54 pm »

I understand your frustration.  However, I will not stop using a VPN for two primary reasons:
1. My online safety is more important than belonging to this forum.  Don't get me wrong, I love this forum.  It's been a great resource to me on my amp building journey, and the people here have been consistently awesome.  I don't want to get kicked.  But I will if it comes down to a choice of VPN vs EL34world.
2. The Australian Defence Force *highly* recommends its members use a reputable VPN, amongst other things, for cybersecurity.  They have *very* good reasons for making this recommendation. 

It's true that a determined hacker could probably defeat most defences I could marshal (heh!  get it?).  Cyber-crimes, like other crime, is predominantly crime of opportunity.  For me, a VPN reduces opportunity by making me a slightly more difficult target to track.

This website is a fixed target.  You need castle defence strategies and I'm no expert.  I'm just sorry I'll be caught up in the crossfire.

38

Tube Amp Building - Tweaks - Repairs / Re: 1968 Fender Vibrochamp AA764 Resto

« Last post by tubeswell on December 06, 2025, 04:35:35 pm »

Jealous. I saw one at Pete's music shop in King Street, Newtown last time I was in Sydney, but didn't have the spondoolies to collect it at the time.

39

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 tubeswell on December 06, 2025, 04:32:33 pm »

If you twiddle around with the tone controls in the spice model, you'll see the TMB tone stack boils down to 2 basic filters that are also present in the classic fender Treble/bass tone stack - but with the addition of a mid pot that controls the amount of 'scoop'.


The two main filters are:


1) a low-pass R/C filter where the amount of bass can be 'bled out' by the Bass knob at full CCW cut, or dialled back in with full CW rotation; and
2) a high-pass C/R filter controlled by the treble knob. At full CW rotation the treble pot is a straight high-pass filter, a


With each of the pots a full cut, the highs and/or lows are attenuated.


The mid pot is a another R/C filter that depending on the rotation, either dumps the mid frequencies to ground or puts the mid cap 'in parallel' with the bass cap (depending on the rotation of the Bass pot) so as to put more 'mids' back into the signal path.


Merlin's books cover the math.

40

Tube Amp Building - Tweaks - Repairs / Re: 1968 Fender Vibrochamp AA764 Resto

« Last post by TIMBO on December 06, 2025, 03:45:16 pm »

Thanks mate,
I think I'll totally dismantle the chassis so I can give it a good clean and work back from there.
I'm not 100% sure of the story of this amp, I'm assuming that the original PT was to be replaced with the Ferguson PT166 325-0-325 @60mAs
and Hammond PT was also purchased as it was a better vintage look.
FENDER.PDF
The original schematic calls for 315-0-315 HT so I guess the 325-0-325 will have to be close enough