Quote from: Tassieviking on February 03, 2025, 01:27:07 PMWhere did you get the cassette adaptor ?
Whats the brand and model of it ?
A nice picture speaks a thousand words.
I really like to try this as I have some old cassette players somewhere.

I got it from MercadoLivre (a Brazilian marketplace, it's kinda like Amazon), but I found one available on e-bay .

The adapter is a Coby CA-M800 "cellular phone car adapter", there's pictures of it at the end of the first video, but I'll attach them on this post too. I'm pretty sure any modern equivalent will work just as well, but you might have to remove the insulation from the cable to make the cassette player/recorder door close properly (I ended up using some thin wire off of a broken laptop screen cable and made an adapter to connect it to pedals and such).I only got this one because it was the cheapest available for me, but the fact it has 3.5mm jacks instead of a built-in cable honestly makes it work better for me.

If you do get one, fair warning: the coily cable it comes with WILL crumble. Just cut it off and keep the 3.5mm tip (if you reuse those like I do), and maybe keep the mic it comes with. For some reason they made the mic cable insulation of a different material that won't crumble, so that part is okay. It even has a lapel clip!

Quote from: joecool85 on February 02, 2025, 10:43:54 AMWhat are you using for headphone amps?  Are these Vox amPlugs?

It's all in the videos. I used a Joyo Bass and an Xvive Classic Rock
I do have a Vox Amplug 2 AC30, but didn't like how it sounded as much as these other two.

Quote from: joecool85 on February 01, 2025, 04:38:33 PMI think this sounds awesome!  Great job!

What is the signal chain though?  IE - is the guitar going straight into the cassette adapter or is there a preamp or pedal first?  Any added distortion circuitry?

The chain is:
Guitar>headphone amp>cassette adapter in recorder>out (cabinet or p.a.).

On the first video, there's a couple parts of the first clip where I lower the volume of the recorder and you can hear most of the distortion get dialed back. It basically adds crunch on top of whatever you're using to push the recorder.

[EDIT]
And for anyone curious, the schematic for these recorders is freely available on Elektrotanya: https://elektrotanya.com/sony_tcm-s63_s64v_s65_s66v.pdf/download.html

TL;DR cassete tape recorder sounds cool when pushed by a headphone amp, here's two vids showing it off.

First, recorder directly pushing the speaker cab:

Second, recorder into TPA3118 amp:

Long version:

A while ago, I acquired a Sony TCM-S64V "cassette-corder" to experiment with lo-fi recording. Recently, I discovered I could use it as a guitar amp by plugging a tape adapter into a headphone amp, pressing "play", then engaging the pause switch (which stops the motor, but keeps the audio circuit on). Since I kinda like it too much and was afraid of possibly damaging it with this experimentation, I found a similar (but more bare-bones in features) TCM-S63 "cassette-corder", cleaned and repaired it, and proceeded to use it in front of my headphone amps and got the exact same great tones as my other "cassette-corder".
It feels just like pushing the front end of a big amp.
I especially like the very compressed start of the attack in the notes. I wonder if it's core saturation from the tape heads, kinda like if you pushed a tube power amp so hard the output transformer started saturating...

I'll leave the analysis of that to you all.

Quote from: joecool85 on January 11, 2020, 04:51:08 PM

Quote from: tonyharker on January 11, 2020, 03:25:58 PM
As far as I can see these Nu-tubes are just a gimmick. You dont get a lot of gain from them so they are not going to have much effect to the signal.  Snake oil

I disagree. While I haven't played with one myself, I've listened to a bunch of clips of the Vox MV50 series, the AC in particular. It sounds fantastic! How much is the nutube and how much is the rest of the circuit if anyone's guess right now though.

This demo from 2017 shows the sound of the NuTube itself. It's indeed very tube-y:

https://www.youtube.com/watch?v=TXUYgi6GB3I

j_flanders, thanks again for the photo of the board. I decided to do a simple diagram on it of how to do the mod. I'll leave the coupling cap and bass pot I changed out of it, as I don't think it changes much in regards to the overall response of the amp.
I decided to recommend removing R8 along with the Red LEDs, as I think it muffles the amp too much.

https://imgur.com/qZBD5JF

The speaker I used is 8 Ohms, rated at 2.5 Watts. The output transformer was made to order from a brazillian transformer manufacturer (http://schatz.eng.br/), 3k:8R/4R, with bass response starting at 120Hz (due to the space I had available).
I have a switch on the speaker output to change from the 4R to the 8R tap, but looking back at it, I could probably fit 2x switching jacks in there and a larger O.T., no problem. Specially now that I got some 3" alnico speakers off eBay, with much smaller magnets.

I just need to find another fried Honeytone!

Buy one of these little digital Oscilloscope kits:

DSO138 - https://www.ebay.com/itm/263551058348
DSO150 - https://www.ebay.com/itm/223308701225

They're plenty good for most applications, and cheap to replace if you ever fry them.
And while at it, get some "proper" probes as well:

https://www.ebay.com/itm/153317744094

That looks like a 9mm potentiometer to me. Check the measurements in milimeters and see if they match.
Fun fact, if you ever need to use those in a perfboard or protoboard, you can mount them diagonally. The clearance for the holes in that orientation is perfect for them.

Just a small update to this project.

To deal with the noise issue I mentioned on my last post, I tried many things but none of them worked. I ended up using a different DC-DC converter board, which is smaller, and that allowed me to place it further from the preamp tube and, thus, avoid inducing noise onto it.

The board in question is this, from eBay seller VFDClock: https://www.ebay.com/itm/141728332617
Still has plenty of power to feed this amp, no problems. I just needed to adjust the bias on the 5902, by increasing the cathode resistor from 330R to 1k. Works great!

Here's an easy way to do it. Get one of these:

https://tekbotic.com/products/universal-3-5mm-jack-bluetooth-car-kit-hands-free-music-audio-receiver-adapter

And just connect the headphone output from it into your LM386 amp. You can find them by looking up "bluetooth headphone adapter", and there's many different prices, sizes and shapes.

I've used one just like the one on the link, to have my Talk-A-Phone (tube-intercom-turned-guitar-amplifier) as a little "vintage boombox" to play some tunes when I'm relaxing at home, but I currently use it with a pair of Sony Ericsson Bass Reflex earbuds as my daily-driver bluetooth headset.

Quote from: ehsan_zt on March 05, 2018, 02:39:23 PM
2- Another interesting thing I found out was this video:
https://www.youtube.com/watch?v=rRAv76ylAcI
what this guy did is he simply removed C12 2A274K!
I tried this,and it's AMAZING ! when you remove C12, amp will sound clearer and there is an increase in volume. I really suggest trying this and removing it or replacing it with something lower (like 2A272K).
I'd love to know the science behind it,if some one can explain?!

C12 is part of a filter on the second op-amp. It goes in parallel with the feedback resistor R15, but isn't completely across the feedback loop because of R17.
I believe it's a low-pass filter (again, I'm not super well versed in filters), which would explain the change in volume. I'd guess it's there to remove some of the harshness coming from the preamp, and possibly to limit the volume some before it hits the power amp.

Personally, I'd rather play around with the filter instead of just removing that capacitor. You might be able to emulate a cab if you do some clever use of that op-amp. Perhaps copy the values from something like RunOffGroove's Thor output circuit? Or more appropriately, their Britannia circuit? Food for thought.

Get in contact with Retro Radio Farm at https://www.retroradiofarm.com/pages/sell-to-us
They have a lot of interesting radios, and maybe they might either buy yours or exchange it for a more interesting one off their catalog (pretty sure they could easily add a guitar input if you talked to them about it).

I wouldn't gut this particular radio, because it's in very good shape, and it probably just needs a little cap job or something simple like that.

If you really want to build something yourself, I'd advise you look for radio shells/cabinets to turn into a guitar amp, or even buy a cheap "retro bluetooth speaker" that looks the part and gut it (which I'm actually in the process of doing).

But, at the end of the day, the radio is yours and yours is the choice of what it's destiny is. Good luck with it either way!

The heat sink was originally on the switching transistor for the High-Voltage board, but since the circuit pulls only about 5 watts for the B+ rail, the thing doesn't even get warm enough to the touch (the board can handle loads up to 45 watts, so 5 is almost a joke for it). I removed it from the transistor because the board fit in the enclosure better that way.

I had to put it back in the new position to work as a shield for the 6N21B tube, because the switching noise from the transformer was being induced onto that tube. The shielding worked perfectly well, being grounded to the common of the circuit.

A better solution would be adding a piece of metal attached to the chassis, sitting between the tube and the High-Voltage board's transformer, that wrapped around the tube a bit, for proper isolation.
It works as a proof of concept, at the very least. But now that I know, I can avoid this issue on future versions of the project, should those come to be. Wink wink 

Recently, I finished a project I've been work on and off over the last year. It's a subminiature tube amp fitted inside of a Honeytone mini amp enclosure. The original circuit board was busted beyond repair, and I had gotten some subminiature tubes to play with, so I decided to put them to good use.

Here's the final result:

https://www.youtube.com/watch?v=B79d7bydqr0

Check the video's description for the schematic, layout, pics, etc.

Or you can see those and more over here:

https://drive.google.com/open?id=1v7-ppCu_mGSNfZdqfjUrZtzhPhdUXQ48