Magnatone Panaramic Amplifier

[dmp]

I've had a 1961 Panaramic amplifier for years, it's cool, but has a pretty honky sound. I don't use it much as it is.I recently found this video and my amp sounds really similar (go to end to hear the amp). I think there are a few components causing this - maybe with a slight modification the sound would really open up.

The true vibrato is fine (and awesome). Ignoring that, the amp is pretty close to a 6g2 (brown princeton).
Major differences that might account for the 'honky' sound?Initial ideas: the blocking caps before the 6v6 are 0.01uf instead of 0.1uf, which creates a high pass at 72 Hz vs 7.2 Hz. The phase splitter also has some goofing stuff going on with the 2.2M divider.  The tone control is different than the 6g2 Princeton.

The schematic is here (I think) https://www.magnatoneamps.com/schematics/estey_96-10041.png
Although mine has 5Y3 like this version (but this is harder to read) https://www.magnatoneamps.com/schematics/estey_96-10041-revA.png

{edit: links re-linked for clarity-- PRR}

[SILVERGUN]

Major differences that might account for the 'honky' sound?

The speaker will have a lot to do with the overall sound quality.
The honkiness comes somewhat from the fact that they didn't cut mids in there anywhere.
Because of this you probably don't crank it up too high because it will sound harsh. So you are cutting treble and cutting bass and getting mostly honky mids through to a questionable speaker (assumption).
Thats my take.

[dmp]

I can play it through different speakers using the speaker out jacks. I haven't done this in awhile, but the characteristic sound is there in different speaker cabs.   
You're right though, it doesn't have a later fender style tonestack that cuts the mids.
I'd be really happy if it had more of tweed deluxe tone and I think with some minor circuit mods it could get there (example video

)The panaramic has a schumacher OT.Differences from the 5E3 seem to be what I listed above. Larger blocking caps, tone stack, and PI

[SILVERGUN]

Differences from the 5E3 seem to be what I listed above. Larger blocking caps, tone stack, and PI

Sounds like you're onto it. I would try the things you have listed, then a "better" speaker. Although, the 5E3 doesn't have a tone stack either, so that's a bone of contention.
You could add a "fixed value" tone stack if you want to drop some mids and not drill a hole. Bass never usually goes above 4 on a TMB and mids are fixed in a Blackface anyway. It will be lossy, so there's that.
EDIT - just for the record, I am not looking at the schematic, just making general recommendations based on what you are saying. I'm assuming you are reading the schematic correctly. It would be a good idea to make yourself a clean copy of your intended schematic and post for confirmation.

[dmp]

Cool - I should have said tone control, not tone stack.

I have later style Fenders, I don't need to go that far.
I don't want to change this amp too much, I think just slight upgrades - perhaps what were budgetary choices (or accordion preferences) like 0.1uf in for 0.01uf.
 

[sluckey]

Disconnect the NFB. Any better?

[dmp]

That's a much better schematic - thanks for posting it.I will try as little as possible step-by-step and see. I have a princeton build with switchable NFB and that (disconnect) is definitely something I would like to try on this one.  Good idea
After a little more reading, I think this has a DC coupled cathodyne phase inverter, with the 2.2M resistors setting the bias.

[thetragichero]

... my bad

[PRR]

> DC coupled cathodyne phase inverter, with the 2.2M resistors setting the bias.

It is different but full 20Hz, that's not your honk.

I'm not shocked at 0.01u into 220k, 73Hz. It avoids "mud" and "fainting" from heavy notes at high power. Also the NFB will claw-back some of that lost bass. Opinions vary so you sure should try bigger caps.

[HotBluePlates]

I've had a 1961 Panaramic amplifier for years, it's cool, but has a pretty honky sound. ... I think there are a few components causing this ...

What you're hearing is mostly "the sound of the pickup(s)" plus "the sound of the speaker."

You may decide that's too mid-heavy.  The best/easiest way to correct that is to grab an EQ pedal and notch out the mids.  Preferably a parametric EQ so you can sweep to figure out the offending mid-frequency.

You could get there "modifying the amp" by adding a bridged-T filter.  Funny enough this is the exact circuit a YouTube Guru rips out of Gibson amps, proclaiming it to be "tone-sucking" (maybe that one cuts mids too much, or in the wrong place).

Plenty of people would buy your Panaramic as it sits, so modding the guts is not very advisable.

... might account for the 'honky' sound?Initial ideas: the blocking caps before the 6v6 are 0.01uf instead of 0.1uf, which creates a high pass at 72 Hz vs 7.2 Hz. ...

The guitar's Low E is around 82Hz so we don't mind a roll-off just below that.

[dmp]

Pre-EQ is a great suggestion. I'll try that.
If I do anything to this amp it will be very minimal. It's super cool. Blue ajax caps, Schumacher transformers, ptp.  Two caps have been replaced that I'd like to bring back to original (0.1 and 0.022 400v) if I can ever find them.
 
Thanks for all the help
I hadn't been to this forum in a while - glad it still rocks

[dmp]

An EQ before the amp confirmed where my 'honkiness' is, about 1kHz. I just used a graphic eq (I don't have a pedal yet) and found it quickly. I have a few parametric I can try too, to bring the trough down to 500-800Hz where it is on Fenders.
I think pre-EQing an amp is amazing - thanks for the idea. Definitely thinking about building/buying an EQ pedal now.

I tried 0.1uF in parallel with the 0.01uF blocking caps, and it does improve the weight of the low end, which I like in the clean tone. But can be done with the EQ as well. I haven't tried this at high power.

And finally, I like it with the feedback disconnected. A little more distorted sound and the high frequencies are little more pronounced.  Some one had drilled a 1/2" hole back in the chassis right where the feedback connection was - maybe this mod had been done to the amp decades ago and then it had been reversed before I found it. Anyway, made it easy to put in feedback defeat switch without any destructive mods.