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  Traynor Mark 3
Posted by: jmcd - 12-07-2018, 01:00 AM - Forum: Personal Projects - Replies (1)

After re-reading the tube amp FAQ on the LP website, I got a hankering to modify a Traynor Mark 3 with the standard preamp (LPSP). I found a reasonably priced combo in which the stock speakers were replaced by a pair of 16-ohm Jensen Nighthawks. The stock 

The stock speakers are 8R in parallel, so I'd like to know whether the Mark 3 can withstand this impedance mismatch.

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  Master volumes
Posted by: jmcd - 11-24-2018, 03:11 PM - Forum: Preamp Mods & Design - Replies (10)

Here are a few questions about master volumes (not all of which are conventional preamp MVs, so feel free to move this thread elsewhere).

1. According to TUT, the addition of a series 100k resistor between the wiper of a conventional preamp master volume and the PI fixes the low-end roll off. But how does this happen with a series resistor and the series capacitor?

2. In the long list of FAQs on the LP site, it states that the LP-MV automatically keeps the depth of the presence effect proportional to the signal size. Is the LP-MV identical to the bootstrapped MV shown in TUT4 (the one with the dual-ganged pot), or is there an additional circuit to vary the depth of the presence effect?

3. I have yet to try the SL-MV, but I am guessing that it has no effect on the presence control. Is this correct?

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  London Power 3 channels amplifier project
Posted by: Vostre Roy - 11-21-2018, 03:20 PM - Forum: Personal Projects - Replies (17)

Greetings to all!

I've mentioned in some other threads that I'm in the process of building a 3 channels, 50w amplifier using London Powers kits. This is the 6th amplifier I'm building out of a kit but it is by far the most ambitious project I've started, I will take my time and try to do it right as this has the potential to be the ultimate amp for my need.

Here's a list of the kits I'll be using with this amp:

- LP-Pre 2 channels Preamp

- Z-Pre 1 channel high gain Preamp

- BFX Effect Loop

- 2xPA66 (4 power tubes capacity)

- PSU-TPA power supply

- 2x RLY Relay kits (for channel switching)

- SV1 Power Scaling

- GND Galactic Ground

Now for this project and the previous I've done (Ceriatone HRM100 MKII), I've done the layout on AutoCAD in order to make sure that everything will be drilled properly. The chassis I'm using is an Hammond 1441-32BK3 (17x10x3). Here's what the layout looks like as of today, since I'm not going home until next week I might tweak it a little bit but I think this should do the trick just fine

Front panel:

Back panel:

Top view (looking at the board on the socket side):

ISO Front view (didn't took much time on it, just to give a rough idea so the tubes and transformers look like crap):

ISO Back view:

If any of you think of any improvement or mistake I might have done, please feel free to share it. I'm not an electronic expert, just an hobbyist DIY guy.


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Posted by: Dshepp806 - 11-19-2018, 12:05 PM - Forum: New Member Introductions - No Replies

Greetings to all!   

Being a RUSH disciple and having worked professionally with the group over the years, I must admit I wish I were Canadian!  Aside.

I'm an engineer (old fart from the tube fidelity world) who designs and builds effect pedals, as well as custom tube amplifiers (for about 28 years).  I've had many mentors over the course of my learning bust MUST state that Kevin has been one of the MAIN mentors in my bag.   Glad to see this site up and going.  I had NO idea so I'm stoked and ready to rumble....spend some more money with Kevin as his books have been happily used and physically abused.

Thanks for what you taught me, Kevin!  I'm a big fan who looks forward to future interactions.

My best, to all in this group!

Doyle Sheppard

Sheppard Designs

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  Peavey Classic 30 - screen resistors (or their lack of)
Posted by: Tomislaw - 11-16-2018, 06:30 PM - Forum: Preamp Mods & Design - Replies (3)


I have this Classic 30 that's been sitting in a corner for quite some time and I thought I'd upgrade it a bit. I had been altering some capacitor values before, but thought the circuit could be improved in some way safety-wise. I'll be adding individual bias pots for each tube as well as measuring jacks, but what struck me right from the start was the lack of proper screen protection. TUT suggests providing individual 2,2K/2W screen resistors for each tube in those low-wattage EL84-driven amps which is exactly I'm going to do, but one EL84 in each pair has a 100R resistor on the screen supply. I gather that's a protection against oscillation between doubled up tubes, but will they still be neccessary once the 2,2K resistors are in place? 


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  Coupling Cap Types and Voodoo Parts?
Posted by: makinrose - 11-14-2018, 01:16 PM - Forum: TUT Q&A - Replies (6)

I was wondering what people's opinions were on coupling cap brands and materials.  There lots of expensive parts out there that in the fine print seem to be  polyester or polypropylene caps in fancy large packages.  Is that any difference in sound? Can there be? or is it just a money grab? 

My experience has been that I can hear difference between different material types.  To me polyester/mylar caps sound a little warmer and less detailed than polypropylene.  Ceramic tend to more gritty and harsh. New paper type caps sound a lot like polyester but maybe a little less bright.

The other thing I've found I really cannot tell much if any difference between brands and construction types of the same material.  For example the little Panasonic radial polyester caps sound much the same as the Mallory 150 film and foil polyester. For that reason I'm really skeptical that spending $5 to $15 on coupling caps is worth while. Does the size or construction have noticeable tonal effect? 

What's the lowdown on it?   Thanks! I'm really interest to hear everyone's thoughts.

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  pickup noise
Posted by: jmcd - 11-11-2018, 05:01 PM - Forum: Preamp Mods & Design - Replies (5)

Ok, I'm gonna keep things rolling here in the 'design' section, with yet another question for the gang. I've been following KOC's galactic grounding and decoupling scheme pretty closely, and my builds are typically quiet. However, one thing I have noticed is that I hear pickup noise with my guitar plugged in, volume (of guitar and amp) up, and my hands muting the strings. My guitar has two humbuckers and a three-way switch; and the noise changes as I switch the PUP selector. 

My question is this: Is there any way to mitigate this noise inside the amp?

-- John

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  zener diode bounding circuits
Posted by: jmcd - 11-08-2018, 02:18 AM - Forum: Preamp Mods & Design - Replies (3)

I'd like to know more about the variations of the zener diode bounding circuits that are peppered throughout TUT and seen in some popular modded-Marshall preamp designs (Jose/Cameron/Friedman/Fortin). Here are some specific questions for starters:

1. Sometimes there is a 10k resistor (and large-value coupling cap) off of the cathode follower. Why is this used, and what are the drawbacks of adding it?
2. Some incarnations of the circuit replace the usual large-value coupling cap with a 100n cap as part of the shunt circuit (that is, in series with the compliance resistor and zeners). I get that this cap would keep DC off of the zeners, but I'm not sure how the value of the cap would be chosen. 
3. Some of the modded-Marshall designs listed above put the Master volume immediately after the clipping circuit and before the tone stack. Others put the Master after the tone stack but put a 1M resistor in parallel with the zeners (or in this specific case, transistors). What is the rationale behind this load?

I could draw out some schematics tomorrow if need be.

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Heart Welcome, New Citizens!
Posted by: King TUT - 11-06-2018, 11:05 PM - Forum: New Member Introductions - No Replies

Hello Citizens!

The Pharaoh wishes to welcome all Citizens old and new  Heart

You may feel especially glad that the age of pyramid building is over... for now...
So live happy free lives with music and song!
Power Scale all your amplifiers and have a lifetime of musical enjoyment!

I suppose there is no need to shout those things since everyone here is trying to preserve one's hearing....

The Pharaoh's enthusiasm comes from seeing His Citizens so happy!

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  Hello from Western Canada
Posted by: jmcd - 11-06-2018, 05:35 PM - Forum: New Member Introductions - Replies (1)

Hi All,

I'm John.

In the late 90s I purchased a book titled "Inside Tube Amps", by Dan Torres. The 'lethal voltages" warnings in that book scared me off for another decade, and so I didn't dig into an amp until 2010. My first build was an Allen Accomplice kit. Around the same time I purchased the entire TUT series. Now, there is no turning back....

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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.
Please remember these three principles: respect, sharing, community.
Not familiar with The Ultimate Tone book series? See discussion topics, or click here to visit London Power/Power Press Publishing.

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