Valves for fx loops

[Transcend]

hey guys i currently use a JJ ECC83s in the loop and when the loop is in use i find the amp is a touch darker and not as tight its the same with just a patch lead.

I know i can modify the circuit to counteract this and that the SLO loop has a few issues which im currently working through.

But i was wondering if different valve types would also change it.

Thanks in advance

[JacksonRR]

Yeah, different valves are always going to have at least a subtle effect in almost any circuit. For a real transparent loop, solid state is where it's at. JJs are known to be a bit softer and darker. Other end of the spectrum, as I see it, are the Chinese valves.

[Transcend]

Yeah i know for a really transparent one SS is where its at im just trying to get through this with as little surgery on the amp as possible.

[Dmoney]

i think the SLO loop is pretty poorly designed and placed, in a way. It's a cathode follower driving an FX insert, i assume because of the likelihood of driving high impedance bits. The return is a gain stage and a cathode follower driving the tone stack.

I'm sure switching valves for the send or return stages will make a difference, but I don't think it's designed with transparency in mind. As such, I'd wonder just how transparent you can get it since all those stages are always in the signal path for both channels whether you are using effects or not. The driver and the recovery stage are 2 whole 12AX7's, rather than something like the decatone loop which is within 2 triodes of the same valve, which I feel is a situation where changing the valve would make a bigger difference. if that makes sense.

Maybe I'm wrong, but that's my thoughts on it.
what are you using in the loop? maybe it's a buffer making the tone a bit darker?

I wonder if the SLO chassis would take a metroamps loop mounted sideways, or something similar. I know its a lot of work but maybe in a future build it could be worth thinking about. Building the SLO without the loop, then inserting and SS loop between the tone stack and the MV.

[Transcend]

i think the SLO loop is pretty poorly designed and placed, in a way. It's a cathode follower driving an FX insert, i assume because of the likelihood of driving high impedance bits. The return is a gain stage and a cathode follower driving the tone stack.

I'm sure switching valves for the send or return stages will make a difference, but I don't think it's designed with transparency in mind. As such, I'd wonder just how transparent you can get it since all those stages are always in the signal path for both channels whether you are using effects or not. The driver and the recovery stage are 2 whole 12AX7's, rather than something like the decatone loop which is within 2 triodes of the same valve, which I feel is a situation where changing the valve would make a bigger difference. if that makes sense.

Maybe I'm wrong, but that's my thoughts on it.
what are you using in the loop? maybe it's a buffer making the tone a bit darker?

I wonder if the SLO chassis would take a metroamps loop mounted sideways, or something similar. I know its a lot of work but maybe in a future build it could be worth thinking about. Building the SLO without the loop, then inserting and SS loop between the tone stack and the MV.

yeah these are my main worries with it all to be honest. As you know im aware of the poor design & placement.

I've tried various units in there and they all had the same effect. I've done a bit of googling and it seems almost everything has this issue other than the rocktron Xpression that keeps the signal in the analogue domain unless using stuff such as pitch shifting and one of the mega expensive TC units.

To be honest im not too bothered about it being transparent as i know its not going to happen.

just hoping and all that.

I very rarely use fx loops anyway

[JacksonRR]

I wonder if those solid state 12ax7 replacements came down in price any? These ones, I mean.
http://www.wattgrinder.com/TGDescription.htm

[HTH AMPS]

The loop in the SLO100 is part and parcel of the tone that amp has - take away one of the CF stages and you lose some of that tone.

IF you want a transparent loop, just build the SLO 'as is' and connect the existing loop with a solid wire.  You then have the option of inserting the loop where you want - you could insert it where the existing loop is positioned (in terms of the circuit) or maybe place it after the tonestack right between the treble pot wiper and the PI's input cap.

Oh, and I'm assuming you'd be using the Metro Amps loop.

   

[Transcend]

yeah i figured i would have to do that i'll look into the metro loop.

Cheers

[Dmoney]

soldano actually recommend the loopless slo for studio use, and mike soldano reportedly prefers the sound of the loopless version, which is minus 1 valve.

[HTH AMPS]

soldano actually recommend the loopless slo for studio use, and mike soldano reportedly prefers the sound of the loopless version, which is minus 1 valve.

I assume he just takes out one of the CF stages - that would certainly change the tone of the amp to a more 'raw' and less smooth tone.  My first SLO-inspired amp used this topology and was great - more Marshally and less compressed than a SLO circuit.

[Dmoney]

yeah. I think you can do it by taking a valve out and moving 1 grid wire.
seen some examples of loopless SLO's but never studied them close to see exactly what they do, but I imagine it ends up the same as the Avenger preamp.