Effects loop for SV20ish amp

[audiosalvage]

Hello. I have a newly built 1987 plexi circuit which is cathode biased. I'm very pleased with the sound, but I'd really love to add my reverb and delay pedals. Using them in front sounds terrible. I'm currently using an attenuator and experimented with running the LINE out into the reverb and then into a second amp. Sounds okay with reverb but the delay sound like crap. I dug into the secret sv20 schematic and am attempting to replicate their FX loop section. It does however require a 9v source, how do I get that from my amp? I have the 275-0-275 PT with 6.3v heater taps.
Does anyone have ideas or suggestions?

[Littlewyan]

It's unlikely to sound good in the SV20 loop depending on how you run the amp. If you run it for overdrive then the amp will distort the reverb and delay which will again sound crap. The loop sits between the preamp and poweramp and most of the overdrive comes from the power amp.
What sounded bad about the delay from the lineout?

[Ten Over]

Hello. I have a newly built 1987 plexi circuit which is cathode biased. I'm very pleased with the sound, but I'd really love to add my reverb and delay pedals. Using them in front sounds terrible. I'm currently using an attenuator and experimented with running the LINE out into the reverb and then into a second amp. Sounds okay with reverb but the delay sound like crap. I dug into the secret sv20 schematic and am attempting to replicate their FX loop section. It does however require a 9v source, how do I get that from my amp? I have the 275-0-275 PT with 6.3v heater taps.
Does anyone have ideas or suggestions?

The SV20 schematic must not be all that secret because I have it in my personal library.

Aren't there a lot of complaints about that SV20 loop? Maybe the loop in the reissues would be a better choice to copy. Powered by a 47k/10W dropping resistor and a couple of zener diodes from the HT. A wide array of Op Amps can be substituted for the TL072.

[pdf64]

Why not a LND150 based loop, then there’s no need to drop HT to LT?

[audiosalvage]

I wanted to use a loop so I'm not tied to using another amp just to get effects. Someone suggested trying a non buffered loop dirctly between the stack and PI. I might start there, if that does not work, I will probably build a LND150 based circuit. a shame I ordered some TL072s already.

[pdf64]

Ok but bear in mind the points made in the first reply, ie there’s going to be most clipping happening after any fx loop within the amp.
A dedicated wet amp is the only way around this. A small cheap solid state combo is ideal for a wet amp. I bought one off ebay for 10 pence.

[audiosalvage]

Built a high voltage effects loop using lnd150s and got a whole lotta loud blaring noise with the volume me knobs down. Tried the unbuffered aproach and found it to be to my liking. A bit of loss but sounds natural with nothing added. I can live with that

[bepone]

For this amp, i would build a follower with LND150, in follower 1:10 reducer and from bottom part i would take signal to output send jacks.. return will go to master volume and then to PI.

Like seen, here is used one LND150, only for follower, marshall amps doesnt need return stage booster IMO.

LNDs are back everywhere so now is time for restock lifetime supply

Besides LND there are many other nice fets nowadays .

[audiosalvage]

I don't have a master volume nor do I want one for this amp, maybe that's the problem

[bepone]

great so reducer of your preamp volume by factor of 10 is exactly what you need. you will get overdrive and volume gradually increased , not like before , volume raise fast to 100% and then start the overdrive

[Ten Over]

Built a high voltage effects loop using lnd150s and got a whole lotta loud blaring noise with the volume me knobs down.

Was that the Mojotone design?

[audiosalvage]

Why yes, yes it was. so far a waste of my money and time

[audiosalvage]

With plain old passive loop, I can run reverb and delay, but I run flanger and chorus in the front door. The loop HATES my chorus. I don't use overdrives anymore because the amp itself is overdrive heaven.

[statorvane]

Why yes, yes it was. so far a waste of my money and time

I have built that loop several times - no issues. Put one in my son's JCM-800 clone, my 1987 clone and a single ended amplifier. I added trimmer pots but I don't think they are really necessary.

Chorus and Reverb sound great. I haven't tried a delay pedal yet.

[audiosalvage]

Maybe it's my layout, but I'm going to put my soldering iron down and just ply for a while, I might go back to it on a wintery day.