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Tube pre into a solid state
Tube pre into a solid state
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Old 8th March 2011, 02:59 AM   #1
stolenband is offline stolenband  United States
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Default Tube pre into a solid state

Hello to all.

i want to make a tube pre-amp to try to integrate some tube sound into a solid state amp. And wondering if this is anything worth trying. I will be trying at my own construction of a pre amp. I plan to run it like this:

Guitar --> pre amp --> solid state head --> effects loop --> speakers

would this work at all?? and is there any benefits here??

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Old 8th March 2011, 03:55 AM   #2
bunkie is offline bunkie
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I think you want the effects loop between the pre amp and the power amp, not between the power amp and the speakers.

Lots of commercial amps (Marshall ValveState for example) have a tube preamp and a solid state power amp, so this is a very workable idea.

However, in my opinion, most of these amps fail to work as well as all-tube amps because they are usually done to keep costs down. It's cheaper to do an SS power amp than a tube one of any given wattage. The problem is that the typical SS guitar power amp is as cheaply made as can be. Small power transformers, small power-supply filter capacitors and poor attention to detail make for mediocre results. Again, this is my opinion, others may disagree.
Peter Hansen
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Old 8th March 2011, 04:02 AM   #3
century tek is offline century tek  United States
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I don't disagree, but I will say that both do work. A lot of people have solid state preamps going into tube amplifiers, and vice-versa. I guess it just depends on your ears and dollar budget.
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Old 8th March 2011, 04:35 AM   #4
stolenband is offline stolenband  United States
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I am getting a line 6 or ibanez ss amp. I am moving on from combo amps, trying to get a stack, so if i use the tube pre, will it get it to sound any closer to true rube amp??
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Old 8th March 2011, 07:56 AM   #5
tinitus is offline tinitus  Europe
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Tube pre into a solid state
I expect a guitar tube pre to be relatively tricky, with regards to impedances and gain structure
been looking at a Summit pre
if I remember correct it has both SS and tube curcuit, and a blend fuction
no doubt a tube could give you tube sound, but not automaticly

been thinking about going the opposite route
to build a cheap tube power with EL34
and use maybe Tech 21 Sansamp bass driver
or even build my own pre too, with combined Jfet and tube gain

with commercial amps, note if it takes balanced signal only, or have multiple options
and input from guitar may need to be very high impedance, megaohm
with onboard guitar pre it may be different
the Summit has switchable input impedance, so maybe it could be a matter of simple resistors
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Old 22nd August 2012, 04:58 PM   #6
Jules01983 is offline Jules01983  United Kingdom
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Default tube pre/SS power amp hybrid

I've been considering this idea myself based on the Marshall VS100 that I have. The power amp stage of that failed and I managed to rig a Velleman K8060 power amp into the place of the failed Marshall unit. It works but is messy. Thinking I would like to make a cut-down version of the VS100, I have been pondering the building of my own tube pre/SS power Amp. I have just cut and pasted various parts of the circuits of the VS100, K8060 and Ampmaker SE5 that I built last year together and wonder if anyone with more experience than me (shouldn't be hard to find!) could pass an eye over it. I know it's not going to sound that good from the price of it and any suggestions for easy/V-cheap improvements would be gladly received. Mainly I just would like to know, Is it just going to go BANG and take me with it or does this look like it might work?
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Old 22nd August 2012, 05:00 PM   #7
kevinkr is offline kevinkr  United States
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Tube pre into a solid state
Old thread moved to Instruments & Amplifiers since it is guitar amp related.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 22nd August 2012, 06:31 PM   #8
cyclecamper is offline cyclecamper  United States
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I've had a lot of great results with tube preamp and ss power amp, as well as all-tube. Transistor front ends...are really tricky and IMHO not as versatile.

Note that my stuff is designed to be versatile, but not to switch sounds instantly during performance. I can get any sound I want but it takes some tinkering.

My favorite is two Fender preamps sections in series, with a bypass switch around the second one. Jerry Garcia did OK into an Alembic preamp that was basically the two preamp channels of just about any Fender tube amp, except Jerry put the two preamps in series, just running a cable from the output of one into the input jack of the other.

This allows you to use 4 12AX7 stages:
An input buffer for some gain. Leave out the second input jack and the series resistors. You can connect the input more directly to the grid of the first tube stage for much better sensitivity, just by leiminating the resistor netowrk at the input that provides two input jacks for each channel. Wasteful unless you have a stereo guitar. The circuit between the particular pickups and volume pot in the guitar is really critical...remember when for a few years steroes had switches to match the input to the turntable cables and cartridge? Well, for guitar all the same concerns apply.

side note: Right after the first stage and before the first tone stack I usually provide an output jack (with a second volume, on the back panel) where there is still maximum dynamic range (before any tube compression), for driving the voltage-control section of an auto-wah or trigger-filter...sense here for the control voltage, but apply the filter to the output of the preamp.

Between stage 1 & 2 is a volume and tone stack, but what matters most is the bright switch which puts a cap across the volume pot. The value of the cap determines the frequency where this "bright" treble-pass comes in and the "volume" knob setting also affects how steep the curve is.

The next stage 2 regains the output lost in the tone stack. If overdriven, it can add some post-preemphasis distortion too.

Now we're between the two channels. This is a great place to add an effects loop for additional distortion devices.

That goes right into the next stage 3 (or a bypass switch), which would have been the input to the second channel, but now in series with the output from the first channel. This is like Jerry's cable between channels...you can optionally put a volume pot between. This tube generates most of the compression and distortion. Because it is between the pre-emphasis curve from the "bright" switch and the post de-emphasis curve of the next tone stack, you can control the tone (bass/treble) of just the distortion seperately from the guitar tone. For instance, for a creamy distortion that's not irritating, you can set the first volume low with the bright switch on, then the treble turned down on the second tone stack...the guitar tone gets treble boosted and cut, and sounds about right, but the distortion generated after the first tone stack only gets its irritating treble cut.

Then there's the second channel's volume & tone stack. You don't need a bright switch in this one.

Stage 4 regains the losses of the 2nd tone stack and drives the power amp.

You need a volume control on the power amp input and/or a volume on the output from the preamp. You might also put jacks for the effects loop here, it's a great place to add reverb, echo, chorus, flange, phase-shift, pitch-shift, tremoolo, true vibrato, etc. after the real string-touch, tone, distortion etc. are established.

One more thing I should mention: If you're using a solid state power amp, you want it to faithfully reproduce the sound of the preamp, without adding any distortion of its own, as the solid-state distortion is not very "musical" to say the least. So I usually recommend 4 to 10 times more rated power than if you were using a tube power amp. And if the ss power amp has a switfhing power supply or it itself a switching-mode amp, that's great, but then double the required rating spec again. a 100-watt (continuous) rated switching-mode amp might not make a 101-watt output at all, not even for a millisecond duration.

I don't like starved-plate stages...if you want that buy a Chandler or Blue Tube or any of their ilk and stick it in the effect loop or between pre and power amps. A solid-state preamp with one starved-plate tube will not sound like I want.

Another thing worth trying it to build the preamp into a floor box with some footswitches. Shorter cable run to the guitar. Knobs are convenient if you're young enough to stoop over, without feedback problems approaching your backline.
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Old 22nd August 2012, 06:55 PM   #9
cyclecamper is offline cyclecamper  United States
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One other thing: If you have two tube stages in series, both driven outside their linear range and into a bit of compression and distortion, it sounds different than jsut driving one stage harder. A 'scope picture doesn't always correlate well to what you hear...but there's a theory flaoting around that the distortion is mostly to the peaks, and when you shift phase by going thru a stage, then apply more distortion, it's to a different area of the waveform. Just one thing to keep in mind. Sometimes for some sounds it's essential to have more than one tube stage adding its signature, and sometimes you don't want those sounds added in parallel.

The Fender circuit is simple and well-understood. That's why I recommend two, with a lot of volume controls between stages and at output (but not at input, I don't even like the volume controls in most guitars). Consider a volume pedal after the first tube stage (a poorly-named drive or gain pedal, it also controls distortion), and another volume pedal at the output to the power amp (like a master volume, it does not affect tone). I've had some luck with a pedal housing a dual linear pot, with some resistors and trim pots to alter the curves and ranges, wired oppositely, so at one extreme the pedal turns up the early "gain/drive" volume and the master volume down, at the other extreme the pedal turns down the early "gain/drive" and the master up. It's a pedal that allows you to fine-tune the exact guitar touch that will cross the line from clean to dirty.

Clean is clean, and two preamps is series can be adjusted to add a little gain at each stage with all stages within their linear range and have a wonderful clean tone, especially with that first bright switch. Of course you've got to decide what knd of dirty you want. I make two broad classifications: auto-correct and emotive. The distortion I call auto-correct makes every note sound the same; same attack, same tone, same compressed volume, it automatically corrects the shortcomings of your fretboard taps, hammer-ons, pull-offs, and sweep picking to make every picked note the same. As spell-check is to your computer writing, so auto-correct distortion is to your guitar playing. Transistors can do this kind of high-gain distortion, as can a hard-driven Marshall. The other kind of distortion is more emotive, and allows you to do clean single-note picking with some dynamic range, yet pick harder to get some bite like a singer's voice or sax or trumpet when over-driven for very emotive phrasing, and it adds a lot of rich complexity, beats, overtones, harmnics etc. when multiple strings are excited.

Good luck to all.

Last edited by cyclecamper; 22nd August 2012 at 07:01 PM.
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Old 23rd August 2012, 12:00 AM   #10
Minion is offline Minion  Canada
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I use a 2 channel DIY tube preamp with a DIY solid state power amp , though it sounds awesome it needs the FX loop because without my EQ and DBX compressor (and some other stuff) it sounds not nearly as awesome .....
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