Search found 92 matches

by oldhousescott
Sat Feb 09, 2013 8:21 pm
Forum: Technical Discussion
Topic: Please help. (Weird acting input resistance)
Replies: 12
Views: 1737

Re: Please help. (Weird acting input resistance)

Did you put back the same resistor you took out? It sounds like you put back a much lower value resistor, maybe 4k7 or 470 ohms. The pedal has a low enough output impedance that it can drive that low of an input impedance, but it would make a regular guitar output sound dull and weak. 470k should be...
by oldhousescott
Sat Jan 19, 2013 4:05 am
Forum: Technical Discussion
Topic: Volume Pot Taper On Vox AC 30
Replies: 6
Views: 3072

Re: Volume Pot Taper On Vox AC 30

Bourns has amp pots also.
by oldhousescott
Thu Sep 06, 2012 7:06 pm
Forum: Technical Discussion
Topic: where to go to to have faceplates made?
Replies: 38
Views: 8859

Re: where to go to to have faceplates made?

Jeanne at BNP and Sandy at Precision Design are both top drawer. Highly recommended.
by oldhousescott
Sat Aug 04, 2012 1:15 am
Forum: Technical Discussion
Topic: Acoustic Bolt on Neck
Replies: 16
Views: 4709

Re: Acoustic Bolt on Neck

Certain Epiphone acoustics from the '70s had bolt-on necks similar to an electric bolt-on.
by oldhousescott
Fri Jul 20, 2012 3:33 am
Forum: Technical Discussion
Topic: Ampeg GVT15 - What circuit is that?
Replies: 2
Views: 1808

Re: Ampeg GVT15 - What circuit is that?

My guess would be a bridged-T filter with the pot in the bottom for more or less mid cut.

If you ask Pyotr nicely, he might just tell you.
by oldhousescott
Thu Mar 08, 2012 2:15 pm
Forum: Technical Discussion
Topic: Fake PI
Replies: 16
Views: 3626

Re: Fake PI

You will have a helluva time emulating power tube grid conduction without having a power tube to cause stuff to clip earlier.
Couldn't you do something with zeners and regular diodes to simulate the grid conduction? Maybe something like this:
by oldhousescott
Wed Nov 09, 2011 2:43 pm
Forum: Technical Discussion
Topic: Tone Stack Simulator and "Designer"
Replies: 1
Views: 1156

Re: Tone Stack Simulator and "Designer"

Grab a (free) version of SPICE or pSPICE and model your circuits. It won't give you the interactive control like the TSC, but you can run frequency plots at various settings to get a visual of what your stack is doing. I used B2 Spice Lite to model the D-stack and make some changes that bring it mor...
by oldhousescott
Fri Oct 28, 2011 7:28 pm
Forum: Technical Discussion
Topic: Transformerless Reverb
Replies: 10
Views: 4662

Re: Transformerless Reverb

I "borrowed" the design that Carvin uses in their Vintage series of amps for a D-style amp conversion. I bought an Accutronics/Belton tank with the high input impedance, and used a single 12DW7 -- the 12AU7 side for the drive and the 12AX7 side for the makeup. Worked well enough, not surf quality, b...
by oldhousescott
Mon Oct 17, 2011 8:19 pm
Forum: Garage Talk
Topic: adams amps malware?
Replies: 2
Views: 1491

Re: adams amps malware?

Yeah, I got the same message last week. I used the wayback machine to find the info I was looking for at that site. I don't know if the site is actively maintained, but I hope it can be remedied.
by oldhousescott
Mon Aug 29, 2011 8:43 pm
Forum: Technical Discussion
Topic: Running My Fender Hotrod Deluxe without powertubes?????
Replies: 11
Views: 1891

Re: Running My Fender Hotrod Deluxe without powertubes?????

Stick a shorted plug into the power amp in jack and that should kill the sound.
by oldhousescott
Mon Aug 29, 2011 8:41 pm
Forum: Technical Discussion
Topic: Tweed Overdrive w/2CF
Replies: 3
Views: 1177

Re: Tweed Overdrive w/2CF

Know, too, that unless explicitly stated otherwise, these are all built, tested, and tweaked designs. I know 10thTx spends a lot of time getting the right combination of clarity, note bloom, touch sensitivity, harmonics, etc., at least for his own sensibilities, in each of these designs. He is indee...
by oldhousescott
Tue Jul 19, 2011 7:36 pm
Forum: Technical Discussion
Topic: Seeking more clean power from this design
Replies: 44
Views: 9513

Re: Seeking more clean power from this design

Check the other 56K (the cathode resistor). Make sure you've got a good ground. Also check the 1K. With only a 6V drop, it seems like something is way out of spec or not properly connected. Yes, you should have about 300v on the plate and about 50v on the cathode. As measured, you're only flowing a...
by oldhousescott
Tue Jun 28, 2011 10:28 pm
Forum: Technical Discussion
Topic: Finding the Right OT - Quad of EL84
Replies: 11
Views: 3204

Re: Finding the Right OT - Quad of EL84

Unless you plan on going ultra-linear, the Dynaco is overkill. The TW OT is also perhaps not the best choice at 6k6 primary impedance. You could actually get by with the Fender HRD or Bassman OT at Triode Electronics. The Allen TO35MT or TO40MT would also work.
by oldhousescott
Fri Mar 11, 2011 3:48 pm
Forum: Technical Discussion
Topic: Where do I measure bias voltage?
Replies: 8
Views: 1911

Re: Where do I measure bias voltage?

Yes, you can leave the 1 ohm resistors in permanently.

When measuring, be aware that the cathode current contains both the plate and screen current.