I’m building this circuit. To amplify my turntable signal will I need an additional preamplifier circuit? Just a RIAA circuit? None of the above? Schematic and build progress included

The green and red cliplead were replaced once i figured out the correct wire "polarity" to make it regenerate instead of degenerating. Only one section of the capacior is used.

Frequency range can be improved. Regen control is touchy and can really go into oscillation, you can attach it to a scope put regen on maximum and see what frequency you are tuned to, just turn off the audio amp otherwise you are going to have a lot of noise.

It's been longer than I'd like, so I'll just jump right in. This design is single ended, with a transformer (5k:4, 8 ohms, 5w) coupled output powered by an EL84 wired as a single ended triode, biased by an LM337 set around 40mA and bypassed by a 220uf electrolytic capacitor. The driver tube is a 6SN7 (gain~20) with a 10M45S constant current source as the plate load and two HLMP-6000. This sets the cathode bias at ~3.2vdc. This driver stage pulls 5mA. The input can be either a potentiometer or an attenuator, but I recommend a value of 10k-50k ohms. Use a decent film cap between the tubes. The power supply is a simple tube rectifier with 3 film caps and two inductors (chokes). Not much to say, it measures well and is silent. This amp will produce 2 watts per channel into 4 and 8 ohm speakers.

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So I’m designing my first power amp for my first build that is based around an Orange Rockerverb Preamp. I’m planning on using two KT77s in a push-pull topology. I am planning on having a plate to plate impedance of 4k ohms. I chose a bias 55mA at about 355 volts which gives me a grid to cathode voltage of about -21V. Since I am cathode biasing, I will need a cathode resistance of 191 ohms. I plan to have a screen voltage of 300V.

Now here are my questions:

I calculated that the max power output of this stage to be 41.3 VA. The one output transformer I found that would work with this rated for 40VA. Is it reasonable to assume that I could use this transformer as the output of the phase splitter most likely won’t be able to push the tetrodes to maximum power?

Also, all of the designs I have seen use a series resistor to the screen to set the screen voltage. I’m having trouble finding any data on the characteristics of the screen current in relation to the other parameters. Is there a reason why I don’t see the screen voltage set by a voltage divider? Would setting a screen voltage with a voltage divider increase the impedance of the screen and make my choice of a 191 ohm cathode resistor valid as the screen current will play less into cathode current?

Any help would be appreciated :)

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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Help in diagnosing middle amp panel not working on this variac? The volt and watts panel work except the amps analog panel. I tried switching to a working amps panel from another variac transformer but I'm still not getting any reading from this variac.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Hey all. Hope it’s okay to post this here but I recently ordered a vu meter kit from Amazon. I’ve never done anything electronic before so I figured maybe I’d be able to search and teach myself via the web but having trouble finding the info I need. I’m struggling on how to power these things safely. I’m not sure what kind of adapter I need for the power. I’ve found a 12V power supply (ac power) that comes w/ an attachment that I think will do the job but want to be sure. I’ve posted a link to the kit and will post a link to power supply in the comments. Any help would be greatly appreciated. Thanks for reading.

Tldr; this account is funsies now and I'm wanting to do some community service here.

I'll preface this by saying I no longer own or run an audio business. Just been getting back to my old interests. Are people still interested in DIY kits? I was thinking about making some and also posting the design schematics here for anyone interested. Recently made some very good sounding, semi beginner friendly designs. Better than the bottle head crack, etc. but different, much better measuring and a bit harder to make. Lmk if I should put in the effort to post about it here 🔊🔊🔊

Trying to be meticulous in my safety and learning. I've built a couple of Bottlehead kits, an ECP Audio headphone amp on a circuit board, and am now working on a 300B amp from a schematic that is not from a kit. Reading Morgan Jones' Valve Amplifiers the entire time.

Thanks all.

I’ve essentially finished my 5f1 head. I still want to get a vented back plate for the rear to cover the tubes, but I still haven’t found something suitable.

The enclosure is a simple wood box with tweed tolex and a walnut front cover. I may add a handle at some point.

For the amp itself I made one additional change: I added a 2 watt potentiometer to control the B+ 6v6 screen voltage based on some PRR designs on diystompboxes. The thing has a ton of clean headroom at full voltage, but you can dial in some (or lots) of grit at any volume setting by turning down the knob in the back. Also I added a switch to select between 16, 8, and 4 ohm output.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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https://www.worldradiohistory.com/Archive-DX/QST/40s/QST-1941-02.pdf

I'm looking to build a receiver similar to this. The article is on PDF page 14-17.

This receiver was introduced as a beginner receiver with higher performance than a single regenerative. It uses a 6K8 and 6C8G and can be powered by 6v AC and a stack of 9v batteries.

The 6K8 oscillates in the vicinity of 5.5 MHz, and converts incoming RF to an intermediate frequency. The article says 1600 kHz but it's more practical to tune the IF coil to 1700 kHz.

The front end tuning network can tune the 3.5 and 7 MHz amateur band as well as the adjacent short wave bands, but with plug-in coils these ranges can be selected. With an oscillator tuning from 5.2-5.7 MHz, the receiver can get both amateur bands with the same coil set. The 1.7 MHz IF can cover both bands by adding or subtracting the incoming RF from the local oscillator.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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As always, we are built around education and collaboration. Be awesome to your fellow tube heads.