Musing about adding reverb to an amp

soma1975 · October 2023

I doubt I'd ever get around to doing any of this but my Marshall SV20 combo is my perfect amp. Except I'd love if it had onboard reverb. And a bigger speaker

If I was to rehouse the chassis to fit a 1x12" would it also be possible to fit an onboard reverb so I wouldn't have the issue of running verb pedals into an overdriven power section?

Alex2678 · October 2023

It is very complicated to add reverb to a pre-existing amp, probably more so with a pcb amp like the sv20- maybe even practically impossible though I’m not an expert.

Any inbuilt reverb you added would still come before the power section though, so if the power section was overdriving the reverb would be too

soma1975 · October 2023

Balls. Ah well.

There goes my pipe dream.

ICBM · October 2023

Reverb pedal in the FX loop. That’s really the only point of a loop on a small non-MV amp like that - most of the overdrive is still going to come from the power stage, but it will at least get it after the tone stack driver which does contribute some.

The good news is that classic non-MV amps with reverb also have that order of reverb before overdrive and sound fine, so don’t over-think it.

As Alex2678 said, modding the amp will be difficult, even to add a basic digital reverb - not impossible, but not worth the bother when it will have the same issues as an outboard unit in the loop.

soma1975 · October 2023

Cool thanks. I guess if I rehouse I could just make a space for a reverb pedal in the back. To be fair I could just stick one there now. I have never used a loop before, and I heard the SV20 one is shite. Exciting times.

Jonathangus · October 2023

Sounds like you really want to go back to the head and cab which you had (a few times

) before.

Alex2678 · October 2023

Turning the mix down should help to avoid clipping the reverb signal a bit. If I wanted to add proper reverb to an sv20 I’d probably put a surfybear in the loop

fastonebaz · October 2023

Just tape a reverb pedal to the back of it wired into the fx loop and it just means you need to plug in two plugs to switch the amp on. Probably the same net cost and much less effort.

Alex2678 · October 2023

soma1975 said:

Cool thanks. I guess if I rehouse I could just make a space for a reverb pedal in the back. To be fair I could just stick one there now. I have never used a loop before, and I heard the SV20 one is shite. Exciting times.

I’d try it for yourself, I’ve seen some people saying the loop is great, and I’m yet to hear of an fx loop that at least 50% of online commenters don’t hate. Depends how you’re using it and the pedals youre putting in it

noisepolluter · October 2023

Might you just get away with a new baffle? Mini Jubilee combo has a 12” speaker, I think that’s the same size?

(also - wouldn’t an onboard spring reverb still be going into an overdriven power section, effectively the same as using a reverb in the amp’s effects loop?)

I will say that my mini JCM800 loop is rubbish, (noisy and drops volume) but I’ve also read that the SV20 one is better. If you find it isn’t, could the circuit be modded for a better loop? The one in my DSL40 works perfectly.

edit: sorry, I’m just repeating what other folks have said

ecc83 · October 2023

Yes, this would be a serious amount of work. I added a reverb tank to a Blackstar A100 head and it was fairly easy for me as I have been buggering about with valve amps all my life. The chassis had plenty of room for the extra valve and transformer (guess whose!) plus of course I had all the resources of a very well equipped electronics workshop to call on!

Once done it was found that the circuit had a nasty 'honk' (at about 700Hz IIRC?) and I had to work up a notch filter to suck that out.

Should any one want to have a go I strongly suggest an op amp driver and recovery stage. The driver can be two NE5532 stages in parallel to give a low Z drive (or a headphone amp chip) and another op amp for recovery.

Cork sniffing valve purists might snort but IMO you don't want distortion in a 'verb circuit and in an A/B check I doubt anyone could diff' them. MUCH easier and MUCH cheaper to build and MUCH simpler to power.

Dave.

soma1975 · October 2023

Alex2678 said:

Turning the mix down should help to avoid clipping the reverb signal a bit. If I wanted to add proper reverb to an sv20 I’d probably put a surfybear in the loop

Yeah it's just that thing of reverb level changing sooo much depending on whether I engage a fuzz face or a boost or both or clean that I thought it being built in would alleviate the issue.

Ah well. Maybe just reverb with presets.

Or suck it up and play dry as a bone except delay occasionally.

soma1975 · October 2023

ecc83 said:

Yes, this would be a serious amount of work. I added a reverb tank to a Blackstar A100 head and it was fairly easy for me as I have been buggering about with valve amps all my life. The chassis had plenty of room for the extra valve and transformer (guess whose!) plus of course I had all the resources of a very well equipped electronics workshop to call on!

Once done it was found that the circuit had a nasty 'honk' (at about 700Hz IIRC?) and I had to work up a notch filter to suck that out.

Should any one want to have a go I strongly suggest an op amp driver and recovery stage. The driver can be two NE5532 stages in parallel to give a low Z drive (or a headphone amp chip) and another op amp for recovery.

Cork sniffing valve purists might snort but IMO you don't want distortion in a 'verb circuit and in an A/B check I doubt anyone could diff' them. MUCH easier and MUCH cheaper to build and MUCH simpler to power.

Dave.

As a cork-sniffing valve purist you have absolutely talked me out of giving this any further thought.

soma1975 · October 2023

Am I right in saying the SV20 loop is dogshit?

I don't have any other loop to compare it with.

ICBM · October 2023

soma1975 said:

Yeah it's just that thing of reverb level changing sooo much depending on whether I engage a fuzz face or a boost or both or clean that I thought it being built in would alleviate the issue.

Putting it in the loop should fix that, especially if you’re pushing the input with the amp volume up a long way - the tone stack driver will be overdriving and limit the level changes, then the reverb will be after that.

soma1975 · October 2023

Alright you crazy kids, I'm going to give this a go.

But first I need to buy a new reverb pedal.

Thanks all for very quickly talking me out of this bullshit notion.

soma1975 · October 2023

noisepolluter said:

Might you just get away with a new baffle? Mini Jubilee combo has a 12” speaker, I think that’s the same size?

(also - wouldn’t an onboard spring reverb still be going into an overdriven power section, effectively the same as using a reverb in the amp’s effects loop?)

I will say that my mini JCM800 loop is rubbish, (noisy and drops volume) but I’ve also read that the SV20 one is better. If you find it isn’t, could the circuit be modded for a better loop? The one in my DSL40 works perfectly.

edit: sorry, I’m just repeating what other folks have said

Re the speaker - It's been done on the Marshall forums but surely it is as much about the speaker having room to speakerate (tm) and a12" in there will be squished as anything.

Jubilee is a touch bigger I think

DIMENSIONS (INCLUDING FEET AND HANDLE)

Weight

19 kg / 42 lbs

Width

490 mm / 19.3"

Height

475 mm / 18.7"

Depth

280 mm / 11"

SV20c

DIMENSIONS (INCLUDING FEET AND HANDLE)

Weight

15.9kg / 35 lbs

Width

500mm / 19.7"

Height

460mm / 18.1"

Depth

245mm / 9.6"

soma1975 · October 2023

Jonathangus said:

Sounds like you really want to go back to the head and cab which you had (a few times ) before.

100%

I got this combo this time because it was a billy bargain. Loving it these days though to be honest.

But the head and cab looks cooler.

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Musing about adding reverb to an amp

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DIMENSIONS (INCLUDING FEET AND HANDLE)

DIMENSIONS (INCLUDING FEET AND HANDLE)