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  Heat management with Power Scaling??
Posted by: makinrose - 04-02-2019, 08:06 PM - Forum: Power Scaling - Replies (1)

With Power Scaling when is additional heat sinking and/or a fan necessary? Is there a certain temperature at which one should worry? I'm guessing chassis up in the cabinet designs are more problematic that the typical Marshall configuration.

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  New PSU kits +/-12V
Posted by: K O'Connor - 03-15-2019, 05:19 PM - Forum: London Power Kits & Mods - No Replies

Hi Guys

We have two new power supply kits to support low-voltage circuitry, such as for switching and opamps. The kits provide symmetric voltage outputs aka "split rails" of +/-12Vdc at two different power levels.

PM12-6 provides +/-12V at 175mA

PM12-12 provides +/-12V at 350mA.

PM12 has universal mains fusing, and uses Hammond semi-toroidal PTs, metal-film resistrs, and 10,000-hour caps.

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  Reverb Feedback Issues SOLVED
Posted by: makinrose - 03-12-2019, 12:07 AM - Forum: Personal Projects - Replies (9)

I've been having problem with new build. It's essentially a Deluxe Reverb Combo but with some added decoupling and improved grounding. The issue I'm having is with the reverb tank.  Outside of the combo the reverb is quiet and operates as it should. When placed inside the combo the reverb starts to feedback building into loud howling.  Moving the tank around, flipping is orientation,  and padding the reverb bag really hasn't helped at all. I've tried a few different tanks and am at my wits end about what I'm doing wrong.  Huh  Any ideas?  Thanks for everyone's help!

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  ToT + Resonance
Posted by: sinusoids - 03-10-2019, 08:48 PM - Forum: TUT Q&A - Replies (7)

I'm now in the planning stages of building a new amp head from scratch.  Plenty of chassis room to work with.  This will be my first LPSP,  I am looking forward to that.  Plan now is the to build the power supply, PA and preamp from ToT but with eyelet cards. 

"thunderous smooth" described in TUT caught my attention - I do not like bright tones or hard distortion.  Would the Active resonance presence circuit, fig 6-34 of TUT, work well in the ToT PA?  I'd use both 12AX7 tubes in the EQ network shown.  Would it work following C1 of the PA, fig 6-2 of ToT, with an added coupling cap?  0.47u?  Would a a larger OPT be a little smoother than the 1608 in the circuit?  I have a single 6lb 6.6k OPT that I could use.  6V6, 5881, 6Pi3C-E and 6L6 all are to be tried.  I will add a triode/pentode switch.  I plan to use the bias supply as described in ToT . 

I want to lay out the circuit cards and build this up from scratch.   I mostly play rhythm, the other guitarist I play with has a bright setup and I try to keep things lower (tone wise) and slightly clean to over-driven.  P-90s are on the guitar.

Thanks for any input from anyone, anywhere here.

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  power supply to separate box
Posted by: TiCatFan - 03-08-2019, 03:39 PM - Forum: Power Supplies - Replies (3)


I am contemplating putting preamps in a separate box from the power amp and power supply in a unit I am currently building. I was wondering if this is possible or safe? Are there any special types of connectors that would work really will for this? Anything I should consider for the wiring between the boxes? My concerns are about the plate voltages and heaters. The power supply is the PSU-25.


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  Pots! What brands are good?
Posted by: makinrose - 02-25-2019, 04:53 PM - Forum: Wiring - Replies (7)

What brands of pots do you guys use?  I lots of builder seem to favor the old style CTS pots but I've been using Alpha with no complaints for years.  There a lot of good prices on pots on AliExpress but I'm not sure of the quality. Does anyone have any experience with those brands? Thanks guys!

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  New member
Posted by: sinusoids - 02-14-2019, 12:55 PM - Forum: New Member Introductions - Replies (2)

After all these years, reading the books, I have joined the forum.  I have built several of the TUT amps, modded more, installed SV1 and 2 and bias kits and built a couple of audio amps (PP and SE) based on and from POP.  Also have read (and built a few projects from) glass audio, audioxpress and VTV.  And I really enjoy this as a hobby.  

Presently building the ToT amp on 2 chassis to enable easy, easy mod and experimentation.  Power supply and PA on the bottom chassis and the pre mounted above, with the hammond chassis cover on top and 12AX7 under.  I also sold my most used combo, bought a 2x12 sealed pine cab on ePay and am loading with 1 driver (taking the idea described in SPKR).  I did not opt for a Force12.  like to hear one in it though.


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  Help with Relay Switching ala the Jim Kelly Project SOLVED
Posted by: makinrose - 02-09-2019, 02:17 PM - Forum: Switching - Replies (3)

Hey guys I started a build that uses the simple relay circuit from the Jim Kelly project in TUT 5 and need some help. I haven't done any relay switching before so my problem is not leaping out at me.  

The pre-amp I'm using different than the Jim Kelly but the concept of how I wanted to switch the channels is the same.  My problem is the when I switch channels the relays I'm using are make no connection at all when the panel channel switch is in the open position.  When it is closed and grounding the relays go the Normally Closed position. 

I'm using the Hammond 272JX and using the 5V taps with the same power supply circuit as the Kelly project.  I'm using this 12V relay:

With the panel switch closed I'm getting ~12 VDC on the positive terminal on the coil and 0 VDC on the negative terminal.  With the panel switch open I'm getting ~13.5 VDC on both the terminals. 

Any ideas?  Thanks!

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  10W amp
Posted by: jmcd - 01-27-2019, 10:58 PM - Forum: Personal Projects - Replies (12)

Hi Gang,

My latest build uses KOC's 10W power transformer (by SumR), KOC's 3H choke (by Hammond), a power-supply PCB (my own design, but borrowed KOC's bias supply), and a turret board for the pre- and power amp. It's got quite a bit of gain on tap. Vintage and modern modes accessible via the front-panel Era switch.

[Image: RD9gikNh.jpg]

[Image: JFKxoVIh.jpg]

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  Silverface Bandmaster Reverb
Posted by: TiCatFan - 01-19-2019, 07:36 PM - Forum: Personal Projects - Replies (13)

The Bandmaster has been out of service for a long time, 25 years maybe? Retired, getting back into electronics. Working on the power supply. Wondering if anyone could suggest good suppliers of electronic parts ( caps, resistors ect), preferably in Canada.


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Come in where it's warm!
A warm welcome to those interested in tube and hi-fi audio! Fans of Kevin O'Connor's The Ultimate Tone (TUT) book series form a part of our population. Kevin O'Connor is the creator of the popular Power Scaling methodology for amplifiers.
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