Happy Jack Posted February 12, 2011 Share Posted February 12, 2011 Found myself in a studio with an hour to kill, and started fiddling around. I was playing a P-bass through a 1971 WEM Dominator, so just a simple Volume control, no separate Gain. It occurred to me that I should be able to get "that classic overdriven valve sound" and sensible volumes by turning the WEM up and the bass down. I spent 30 minutes alternating between bass UP / amp DOWN and bass DOWN / amp UP ... and I couldn't hear any significant difference (beyond more hum/buzz from the WEM when cranked). If the volume on the WEM is UP, then presumably both the pre-amp and the power stages will be cranked high. Shouldn't that take any level of input from the bass and overdrive it? Quote Link to comment Share on other sites More sharing options...
KiOgon Posted February 12, 2011 Share Posted February 12, 2011 [quote name='Happy Jack' post='1124953' date='Feb 12 2011, 01:51 PM']Found myself in a studio with an hour to kill, and started fiddling around. I was playing a P-bass through a 1971 WEM Dominator, so just a simple Volume control, no separate Gain. It occurred to me that I should be able to get "that classic overdriven valve sound" and sensible volumes by turning the WEM up and the bass down. I spent 30 minutes alternating between bass UP / amp DOWN and bass DOWN / amp UP ... and I couldn't hear any significant difference (beyond more hum/buzz from the WEM when cranked). If the volume on the WEM is UP, then presumably both the pre-amp and the power stages will be cranked high. Shouldn't that take any level of input from the bass and overdrive it?[/quote] Depends mostly on the output level from the P bass, what Pup is it? Quote Link to comment Share on other sites More sharing options...
Roland Rock Posted February 12, 2011 Share Posted February 12, 2011 (edited) I'm by no means an expert, but my theory is as follows: The single volume control you mention acts as the 'master volume' ie only controls the output volume The input is set at an optimum level. The input of your bass, therefore, is of crucial importance as you'd need to crank your bass volume to overdrive the preamp. Also, I find that the real grit comes from driving both pre and power amps, so you may well need to turn both the bass and amp up. I'd liken it to a stereo, where there is no gain control, and the input stage is set to 'average CD output' level, and the volume control is for output only. I could be wrong, and won't be surprised if the more techie types come up with a more convincing theory! Edited February 12, 2011 by Roland Rock Quote Link to comment Share on other sites More sharing options...
icastle Posted February 12, 2011 Share Posted February 12, 2011 [quote name='Happy Jack' post='1124953' date='Feb 12 2011, 01:51 PM']If the volume on the WEM is UP, then presumably both the pre-amp and the power stages will be cranked high. Shouldn't that take any level of input from the bass and overdrive it?[/quote] No. The classic distortion sound comes from the pre amp gain being turned up so that it distorts. On a single volume control amp like the WEM, it was designed to avoid what you were trying to do. The pre amp gain is preset to a maximum fixed level so it can produce maximum volume but can't be induced to distort. Quote Link to comment Share on other sites More sharing options...
Roland Rock Posted February 12, 2011 Share Posted February 12, 2011 Ah, ok So no matter how much signal you pump into the little rascal, it will 'limit' the signal that goes into the power amp? How annoying. Can it be bypassed, or can you 'raise the ceiling' a bit? Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted February 12, 2011 Author Share Posted February 12, 2011 [quote name='icastle' post='1124976' date='Feb 12 2011, 02:19 PM']No. The classic distortion sound comes from the pre amp gain being turned up so that it distorts. On a single volume control amp like the WEM, it was designed to avoid what you were trying to do. The pre amp gain is preset to a maximum fixed level so it can produce maximum volume but can't be induced to distort.[/quote] Fascinating. So can you only get "that classic overdriven valve sound" by pushing the output valves really hard? That can't be right, surely, or my Orange Terror Bass (valve pre / SS power) wouldn't sound the way it does. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted February 12, 2011 Share Posted February 12, 2011 [quote name='Happy Jack' post='1124988' date='Feb 12 2011, 02:42 PM']Fascinating. So can you only get "that classic overdriven valve sound" by pushing the output valves really hard? That can't be right, surely, or my Orange Terror Bass (valve pre / SS power) wouldn't sound the way it does.[/quote] That is just preamp drive, doesn't have the same compression effect that power amp drive does, and the drive is 'girthier' as well as you can describe it in words, you kind of have to have the bass in hand to appreciate it, because it is compression, and this not immediately audible. Basically to get that distortion you need to be hitting valves with more signal than they can take, rather than just opening them up. Each 12ax7 has two stages inside, so single valve drives either run one into the other so the second distorts, or have some solid state clean boost first. Really thick drive sounds are loads of small gain stages, and the power section drive is another on top Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted February 12, 2011 Share Posted February 12, 2011 This is like chinese whispers! If the signal in is already distorted by another way like a pedal then the amp would just amplify that and give you an overdriven sound. Its just that the OP's amp has no way of getting at the adjustment like most of us with a pre amp valve can to send a driven sound from the pre to the output stage. It wont clean a dirty signal. A valve pedal would do it but it seems most of what we talk about in valve amps comes from the preamp valve rather than the output stage hence the common place valve pre SS output for a best of both and reliability. So if your going to use a preamp valve style pedal you may aswell just use a SS amp too go with it. Probably why it sits in a studio rather than being rocked out with every weekend poor little WEM Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted February 12, 2011 Share Posted February 12, 2011 There isn't only one flavour of dirt. The best drive sounds come from adding dirt at multiple stages a little bit at a time. If you feed an amp a dirty signal, it can either make it the same but louder, or distort it more, making an increasingly dirty signal at each stage. The power amp distorting is another link in the chain, but a necessary step in getting that to drive is hitting it with a lot of signal that it correspondingly produces a lot of signal, and thus, generally, a lot of volume, and with the power stage, you don't have much by way of means to cut that volume. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted February 12, 2011 Share Posted February 12, 2011 And if being used at a gig big enough for a big old Ampeg its probably going from a DI box and no one in the audience hears the drive you have painstakenly created anyway unless its mic'd up even then the pa wont sound exactly like your beloved valve amp. Quote Link to comment Share on other sites More sharing options...
Roland Rock Posted February 12, 2011 Share Posted February 12, 2011 I'm finding this very interesting and informative. Sorry if it's deviating from the OP, but I have another question: If you have a signal which is getting progressively dirtier after driving the pre and power sections, why is it not possible to cut the volume with the master volume and still achieve the same dirty tone? Is this because it's also necessary to 'open up' the power valves (with master volume) to achieve the power amp drive? Basically I'm unsure as to the relationship between the master volume and the power section. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted February 12, 2011 Share Posted February 12, 2011 [quote name='Roland Rock' post='1125037' date='Feb 12 2011, 03:30 PM']I'm finding this very interesting and informative. Sorry if it's deviating from the OP, but I have another question: If you have a signal which is getting progressively dirtier after driving the pre and power sections, why is it not possible to cut the volume with the master volume and still achieve the same dirty tone? Is this because it's also necessary to 'open up' the power valves (with master volume) to achieve the power amp drive? Basically I'm unsure as to the relationship between the master volume and the power section.[/quote] The master volume is generally just before the power stage, at the end of the preamp, the power valves clean limit is the 'watts' rating of the amp, and you generally have to be asking more of them than that before they dirty up, so with a SVT that gonna be somewhere over 350w actual output, which is very loud, loud enough until you get a very large venue (large enough for a decent sound man), you amp sound is going to dominate it's sound field. I am tending towards around 100w rated amps for my dirt, and even then it is mostly preamp dirt, got a 70w incoming that should give me the rest. Quote Link to comment Share on other sites More sharing options...
Roland Rock Posted February 12, 2011 Share Posted February 12, 2011 You the man Mr F, Stupidly, I had always thought that the master volume was at the very end of the chain. That makes sense, and also explains why I love my 100w amp so much! Cheers Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted February 12, 2011 Share Posted February 12, 2011 (edited) [quote name='Roland Rock' post='1125037' date='Feb 12 2011, 03:30 PM']I'm finding this very interesting and informative. Sorry if it's deviating from the OP, but I have another question: If you have a signal which is getting progressively dirtier after driving the pre and power sections, why is it not possible to cut the volume with the master volume and still achieve the same dirty tone? Is this because it's also necessary to 'open up' the power valves (with master volume) to achieve the power amp drive? Basically I'm unsure as to the relationship between the master volume and the power section.[/quote] This is what an attenuator (spelling?) does I think? The idea being to have the valves overdriven to your taste then dissipate the unwanted volume as heat instead. Although I used to play in a band with a guy who had one that never turned the attenuator down (Up If you like) and just used the amps master volume knob still because it sounded better! I know the Guitard term has been looked upon badly recently but...... Edited February 12, 2011 by stingrayPete1977 Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted February 12, 2011 Author Share Posted February 12, 2011 [quote name='KiOgon' post='1124957' date='Feb 12 2011, 01:55 PM']Depends mostly on the output level from the P bass, what Pup is it?[/quote] Should have responded to this earlier ... it's a Korean-built [i]Duncan Designer[/i] split humbucker, which is (obviously) a Seymour Duncan design. Doesn't have anything like the oomph of the SD 1/4-lb in my Bravewood, but there's nowt wrong wi' it. Quote Link to comment Share on other sites More sharing options...
icastle Posted February 12, 2011 Share Posted February 12, 2011 [quote name='Happy Jack' post='1124988' date='Feb 12 2011, 02:42 PM']Fascinating. So can you only get "that classic overdriven valve sound" by pushing the output valves really hard? That can't be right, surely, or my Orange Terror Bass (valve pre / SS power) wouldn't sound the way it does.[/quote] Nope. T'other way round mate - it's the pre-amp valves you need to push hard. Quote Link to comment Share on other sites More sharing options...
umph Posted February 12, 2011 Share Posted February 12, 2011 [quote name='icastle' post='1125340' date='Feb 12 2011, 07:44 PM']Nope. T'other way round mate - it's the pre-amp valves you need to push hard.[/quote] classic overdriven valve sound is combo of pre and power clipping evenly. Not a fan of preamp distortion as it tends to sound thin. Pentodes produce much nicer harmonics and compression Quote Link to comment Share on other sites More sharing options...
JimBobTTD Posted February 13, 2011 Share Posted February 13, 2011 [quote name='Happy Jack' post='1125105' date='Feb 12 2011, 05:35 PM'][/quote] Quote Link to comment Share on other sites More sharing options...
Subthumper Posted February 14, 2011 Share Posted February 14, 2011 [quote name='Mr. Foxen' post='1125014' date='Feb 12 2011, 03:09 PM']There isn't only one flavour of dirt. The best drive sounds come from adding dirt at multiple stages a little bit at a time. If you feed an amp a dirty signal, it can either make it the same but louder, or distort it more, making an increasingly dirty signal at each stage. The power amp distorting is another link in the chain, but a necessary step in getting that to drive is hitting it with a lot of signal that it correspondingly produces a lot of signal, and thus, generally, a lot of volume, and with the power stage, you don't have much by way of means to cut that volume.[/quote] Hi, interesting you should say about the multiple or cascaded gain stages as I recently serviced a Burman guitar amp with such a pre amp. Its a completely different way of getting your sound as it is possible to affect the tone and not just the gain and drive of the circuit by adjusting the three gain controls. Sounded fantastic and got me thinking it would be fab for a bass pre amp (if maybe with a little less gain and tweeking of the tone stacks). Not sure what the Burman bass amps had in terms of controls so maybe one the Burman owners could fill us in. Sorry to hijack the original thread but had to chip in. Cheers Just Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted February 15, 2011 Share Posted February 15, 2011 [quote name='Subthumper' post='1127835' date='Feb 14 2011, 11:53 PM']Hi, interesting you should say about the multiple or cascaded gain stages as I recently serviced a Burman guitar amp with such a pre amp. Its a completely different way of getting your sound as it is possible to affect the tone and not just the gain and drive of the circuit by adjusting the three gain controls. Sounded fantastic and got me thinking it would be fab for a bass pre amp (if maybe with a little less gain and tweeking of the tone stacks). Not sure what the Burman bass amps had in terms of controls so maybe one the Burman owners could fill us in. Sorry to hijack the original thread but had to chip in. Cheers Just[/quote] I plan on using my Burman for bass, but mostly the top end stuff. I think the Burman thing is adding control to various steps of the gain stages, that otherwise would be fixed, it sort of removes the 'signature tone' of an amp and gives loads of flexibility. A mate used a Pro4000 for bass, and it is the same control as my 70w one, first gain and 2 band EQ, then the 3 gains, then a three band EQ, you can patch in after the first gain/eq. Quote Link to comment Share on other sites More sharing options...
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