Round 13--better cabinet emulated direct sounds

[dai h.]

got a used Boss PQ-50 parametric EQ which has a shelving high and low EQ capability I wanted to try on the direct sound from my Palmer PDI-03 to see if that could roll off the unpleasant sounding stuff in the high end--basically some experimentation to see if I could obtain a better sounding direct sound (something I had never been real happy with). Played with the settings (gain, EQ, etc.) and also tried recording and playing back (hoping for some degree of objectivity plus be able to hear the recorded result) and it wasn't so bad. (Signal chain 50W Marshall to Palmer PDI-03 to modded Marshall Power Brake with Rs across the two Ls as load.)

Anyway, fast forward and playing around with the configuration, I found that the basic sound quality was better when plugging the output of the Palmer into the insert jack of my Tascam 488mkII bypassing the preamp and EQ (couple transistors at the balanced input plus a couple of opamps after that). It was sort of cleaner and more dynamic (greater headroom), plus some sort of distortion was less when connecting in that manner(better sounding in the high frequencies). I tried the Palmer 1/4" speaker emulated out to the Boss PQ-50 to insert jack, then a Boss RPQ-10 (which I had modded with NJM5532s in place of the Mitsubishi M5218s) and the RPQ-10 sounded better than the PQ-50 but had less output and headroom. The aspect of the sound that was displeasing sounded sort of like when you try to plug a guitar straight into a mixer and it has sort of a grating top end unlike when plugging into a nice guitar amp and it just sounds better as you turn up.

Next, nothing between the PDI-03's unbalanced 1/4" speaker emulated out to the insert jack, and this sounds the best(I think it'd be nicer to have some additional EQ to chop some of the unnecessary bottom to get a cleaner signal to the tape). The PQ-50 seems to sound okay when recording the Palmer straight through the insert, then inserting the PQ-50 to effect the recorded gtr. sound. I wonder why all that stuff makes the Palmer signal sound so bad. With other sources (cheap mic, line level recordings, etc.) putting the signal through doesn't seem noticeably deleterious but apparently it has a horrendous effect on the gtr. signal.

[Steve Conner]

Hi Dai

I tried a similar setup with a big wirewound pot used as a L-pad, hooked up to an Alesis PEQ-450. It worked very well, I think part of the reason was that the PEQ-450 has two low-pass filters that I could combine for a really steep rolloff of the high end. I did have trouble with a kind of harsh grating sound, but it turned out I was overdriving the EQ and clipping it internally. Maybe your Palmer box has too much output for your portastudio's mic preamps, even on their lowest gain setting.

Now if only the PEQ-450 could save patches

[dai h.]

hey Steve

(arrrggh, closed my reply tab by mistake... drat! Letsee if I can remember what I wrote...lol)

I think part of the reason was that the PEQ-450 has two low-pass filters that I could combine for a really steep rolloff of the high end. I did have trouble with a kind of harsh grating sound,

Harsh grating highs are one of the most objectionable things when trying to emulate a distorted amp sound. Having LPFs helps but I'm not quite certain just having one is enough(maybe the type? or perhaps another one in series?).

but it turned out I was overdriving the EQ and clipping it internally. Maybe your Palmer box has too much output for your portastudio's mic preamps, even on their lowest gain setting.

I did try adjusting the output of the Palmer (has an output control for the spk. emulated out) as I adjusted the amp volume(which affects the gain and output and thus voltage going on into the Palmer) but maybe the Portastudio (as well as the Boss parametric EQs) don't have enough headroom? Intuitively (this may be completely wrong) I'm thinking it has something to do with the circuits using lots of feedback (the feedback is adjusted to control the gain for the mic pre input as well as the opamp circuitry??). I've also got a Marshall SE100 speaker emulator (which has active opamp circuitry to accomplish the cabinet emulation) and subjectively the Palmer sounds a bit more "natural". It seems after trying the aforementioned hookups that you can't add the circuitry in the Tascam input and Boss parametric EQs until the signal is "finished" to a certain point. What was interesting was that the high freq. EQ on the Tascam sounded better AFTER the signal was put to tape whereas before any additional EQ from the Tascam seemed to sound bad(I guess it had something to do with the HF roll off from the limited HF response of the tape recorder).

The Palmer EQ is passive, and I kind of wonder if the Palmer designer just found that passive EQing just sounded better? You have those vintage Pultec EQs for example which apparently have an outstanding reputation (witness the derivatives, clones, even DIY versions, etc.). Anyway I was looking at info I could find on the web, and it seems to me that since the Palmer, Marshall SE100 type devices tap off the spk. out, potentially there is a LOT of drive avail. if you use low values for the voltage divider off the spk. signal (one of the example circuits on the Jensen transformers site for an amp output to line level interface for example use around 220ohms and output Z is given at 100 ohms) and that appears to be enough to hang a Pultec type passive EQ network (well, or *in addition to* the Palmer EQ which seems to sound pretty good) across the output. The Palmer balanced low-Z out is given on their German site as 600ohms (10k for the hi-Z out), so it isn't as low, but (staring at the Pultec schematic for a while) it looks like I could just take the low cut portion (which is basically just a cap, pot, and resistor) and try it across the low-Z out to see if I could take out some of the lows (hopefully in a way that gives what I'm looking for). And (hopefully) the (insertion loss?) won't be enough to matter.

(what it looks like: some pics of mine attached)

pics of apparently an earlier version I found on the web:

http://www.ashrec.com/new_page_2.htm

[dai h.]

well I tried my goofy experiment, and well... it works...sorta (lol). Probably to be expected but rolling off the bottom really kills the signal at the same time. There's also some weird sounding distortion (maybe some peak in the signal from the output transformer of the Palmer Low-Z out not terminated with a low value R?). But, it's also natural sounding at the same time(not the weird distortion but the basic character of the sound). Maybe I should be using differnt values that don't load the signal down so much?

I also incidentally found that emery paper worked vigorously over corroded leads can help make them solderable again and that marking the center punched mark well is important for getting an accurate pilot hole (used some crappy DIY'ed enclosure bought for about the equivalent of a couple bucks that had some XLR connectors and a footsw. since I have about zero metalworking skills though learning a bit).

[dai h.]

okay, I tried taking the 1/4" out from the Palmer to this old tascam line mixer thing with a headphone out (8 ohms) and using that to drive the passive tone network and it works MUCH BETTER although it oscillates if I turn up the volume up from a certain point on. Has a solid state character to the sound but not horrible sounding. Think I'm going to try adding a couple of the other networks so I can at least get some idea of how it sounds with the other controls. I remembered there was a transformer store that apparently sells (their own, I think) trafos at quite a reasonable price apparently and they had a 600 to 8ohms 2Watt one so I wonder if I can use that 8 to 600 and hook it up to my reiss. Fender reverb out?