Search results

So here's my latest DIY amp, the Cockeyed Monkey . . . I always like to try some things that are "new to me" in my builds and this one has several elements that I've been meaning to try for a while. I had never built a directly coupled amp so I figured it was time. I decided on using this...

Heard the sad news yesterday that Tom Leadon has died. Tom was a wonderful guy, warm, gracious and a superb musician. Here's the article from the local paper about his passing as well as some links to obituaries from Rolling Stone and Variety...

I'm using "cockeyed bridge" rectification on my currently breadboarded amp project. It uses a 6AX4GTB damper diode to provide a slow startup. Works great but instead of getting voltage drop through the tube, as you would normally expect, I'm getting voltage gain. Anyone know why?

I recently noticed this new preamp that uses directly heated tubes. Many people prefer the sound of directly heated triode tubes, though they are typically used as output tubes in SE (single ended) amplifiers. The most commonly used DHT output tubes are the 2A3 and the 300B, both of which...

A while back, in my search for interesting oddball tubes, I came across the 5A6 which is a directly heated beam tube with a 9 pin mini base. I've attached the data sheet. A search here and elsewhere came up mostly empty. There were a couple of references to it being used as a preamp tube...

Here's my latest project, which I had breadboarded for most of last year. Yeah, I'm slow. Most of the discussion about Single Ended Triode amps (and amps in general) seems to center on the type of output tube that's being used. Traditionally, the SET outputs are all directly heated. Many...

While I'm still trying to decide which DIY project I want to pursue next, I revisited a couple of previous projects (PP 6B4G and SE 1625 guitar amp) and plan to restore a vintage amp or three. The first vintage up to the bench is a Motorola HS-711 PP 6BQ5 console amp that's being set up for...

So I started working on another Magnavox Build . . . With a (somewhat different) twist. The last one, based on the 175/185 chassis, used 6N6G output tubes and turned out really well in terms of sonics. Cosmetically . . . well, I dropped the ball on that aspect. But, did I mention that it...

So I've been busy in the shop the past several months . . . I posted earlier about the Voice of Music SE 6BQ5 with Local Feedback and my DIY Preamp, the Boogie Factor 1626. https://www.audiokarma.org/forums/index.php?threads/voice-of-music-se-6bq5-w-local-nfb-build.926391/...

So I'm thinking about trying either some Russian 4P1L (a directly heated pentode) or its cousin the 12P17L (an indirectly heated pentode) in PP and I'm trying to get an idea of what OT primary value would be most suitable. I know tubes are fairly forgiving when it comes to differences in load...

Thought I'd post about my recent preamp build using the 1626. First, some background . . . I've been breadboarding a basic preamp circuit with a variety of tubes. This has gone on, somewhat sporadically, for the past couple of years. In all I think I tried at least 8 different tube types...

So I finished my Voice of Music SE 6BQ5 project which involved the addition of a Local NFB scheme. Thanks again to everyone who gave me advice in my earlier thread here: https://www.audiokarma.org/forums/index.php?threads/looking-for-comments-on-this-local-nfb-scheme.921524/ I also got help...

In another thread I mentioned that using resistors with wattage ratings of 3x the actual dissipation was considered standard engineering practice. I mentioned that I sometimes use up to 5x the actual dissipation. I figure that the resistor is less likely to fail, that the amp will run cooler...

I'd like to hear some comments on the local NFB scheme in this schematic I found. Also on its use of a 1N4007 in the G2 supply. I have a SE VM that originally had the preamp section connected with an umbilical. I want to drive it with either a stand-alone tube pre I built or a SS pre. So I...

A few questions about powering up a dormant M-60. I asked about using a variac with this quite a while ago but never got to it. I bought the amp years ago and turned it on (no variac) and played it for a couple days, so it was working. I know nothing about SS or circuit boards. My experience...

In the Magnavox 9300 mega-thread by @dcgillespie, @6DZ7 just questioned whether the modded version of that amp, which produces more power and draws more current, might be pushing the PT too much. I thought I'd start a new thread about this since it would not apply exclusively to that amp...

How do you calculate the output impedance of a simple, single triode section, cap output, preamp? I know the plate resistance of the tube affects this. What's the formula?

So I've been breadboarding preamps using some atypical tubes including a couple of directly heated "battery tubes". I think I mentioned one, the 1LE3, in a previous post. It sounded great but it's very microphonic, which seems to be a common complaint about these battery types. How...

One of the preamp designs I'm breadboarding uses a DHT "battery tube", the 1LE3. I'm using battery grid bias. I've got a question about how to wire the filament battery. I'm using a single AA rechargeable which is housed in a plastic battery holder. Since I don't have a resistor on the...

So I've been scrounging around various bits and pieces for power transformers that might be useful in preamp builds. One of the possible donors is a Wollensak reel to reel chassis. I actually have a pair of these. Unfortunately, the PT would only be useful with very low current tubes since...

So I've been playing around with some very simple, single stage, preamp designs on a breadboard and I have some questions about cap outputs. Being mostly a copy and paste builder, I took a cap output section from a schematic I found and used it with parts I had on hand. I dug up the -3db...

I've been using PSUD to sim some possible PS designs for a preamp. When calculating some configurations I get a warning message. In case you can't read it, it says: "A current sink has pulled the voltage below zero for more than 5 mains cycles, at time 0.0834375". How serious is this...

Testing some tubes on my Hickok 600A but found no test data for 6V7G or 1LE3. Anyone know the settings?

I recently came across an old junked console amp, actually an AM-FM receiver, that ran SE 12C5s. That's a 7 pin beam pentode that runs on low voltage and puts out 2.3w max, probably more like 1.5w with reasonable distortion levels. Found the Sams and the OTs have a 2k primary and 8 ohm...

I recently saw a design that uses battery grid bias with an input transformer. I've used battery grid bias before but with an input cap so I'm interested in trying it with a transformer, which eliminates the need for the cap. The input transformer used was a Lundahl LL1676 2:1. I looked it up...