Crate V5 mods... anyone?

[DeanEVO_Dude]

Jim P,
I have a question for you, I want to add a volume control to my V5 and what I was going to do was replace R27 with a 10K audio taper pot, and Radio Shack has said 10k audio taper pot. R27 is a 1/2 watt resistor, and the 10K pot is also 1/2 watt... one leg of the pot tied to R16, the other leg tied to gnd. and the wiper tied to what used to be the junction of R16, R27 and pin 2 of the 12AX7/R7. Would this work OK? Are there better values for the pot and R16 that I could use for better control?

Thanks.

 

[deafelectromark]

Volume control.

Jim P,
I have a question for you, I want to add a volume control to my V5 and what I was going to do was replace R27 with a 10K audio taper pot, and Radio Shack has said 10k audio taper pot. R27 is a 1/2 watt resistor, and the 10K pot is also 1/2 watt... one leg of the pot tied to R16, the other leg tied to gnd. and the wiper tied to what used to be the junction of R16, R27 and pin 2 of the 12AX7/R7. Would this work OK? Are there better values for the pot and R16 that I could use for better control?

Thanks.

Hi,
The best place for a volume control is between the two tube sections. The wattage is irrelevant as minimal power is dissipated at these low currents. A 10K control is probably too low for a high impedance circuit, I would use at least a 250K control to not load down the preceding stage. Look back at the earlier posts and schematics and see that what you need to do is reduce the voltage going into the grid of the second half of the 12AX7 from the plate of the first half. The only 'trick' is to have it low enough to keep noise and stability under control (<1 meg or so). But if it is too low (<50K), you lose gain (and tone).
Hope this helps.
Mark

 

[deafelectromark]

Volume control

Jim P,
I have a question for you, I want to add a volume control to my V5 and what I was going to do was replace R27 with a 10K audio taper pot, and Radio Shack has said 10k audio taper pot. R27 is a 1/2 watt resistor, and the 10K pot is also 1/2 watt... one leg of the pot tied to R16, the other leg tied to gnd. and the wiper tied to what used to be the junction of R16, R27 and pin 2 of the 12AX7/R7. Would this work OK? Are there better values for the pot and R16 that I could use for better control?

Thanks.

See post #16 for my mod for a starting point. Jim P takes it to the moon and back in 20 pages if you really want to get into it, but you can make this a great amp with NO added parts and very little work.
Mark

 

[DeanEVO_Dude]

Hi,
The best place for a volume control is between the two tube sections. The wattage is irrelevant as minimal power is dissipated at these low currents. A 10K control is probably too low for a high impedance circuit, I would use at least a 250K control to not load down the preceding stage. Look back at the earlier posts and schematics and see that what you need to do is reduce the voltage going into the grid of the second half of the 12AX7 from the plate of the first half. The only 'trick' is to have it low enough to keep noise and stability under control (<1 meg or so). But if it is too low (<50K), you lose gain (and tone).
Hope this helps.
Mark

Thats where R27 is, between the two sections of the 12AX7 and after the tone control (just like the Palo. 508). The only reason I chose the 10K pot value is because R27 is a 10K value. I just noticed that the Palomino uses a 10K linear taper...
If I use, say, 100K pot, should I change the value of R15? I know that the circuit is a voltage divider, but I ain't so good with theory, so...
My intent is to keep the "gain" control on the 2nd stage of the op amp and add a volume control to the circuit (put it where the power led is and move the led above the switch). So far, with the speaker change (Ragin Cajun) I like the sound of the amp, but it is just too loud (almost never move the "volume" past 9 o'clock). I want to be able to put the "gain" up to 1 or 2 o'clock and still be able to be tolerated by the others in the house... LOL
I am also going to go back and re-read alot of this thread...

Thanks. :AOK

 

[jim p]

Volume and gain controls?

It sounds like you are going to keep the exiting volume control as a gain control and then add a volume control after the first triode stage? As stated above in another post I would go with a 100k audio to a 250k audio pot for the volume control. Remove R15 and R27 connect one side of the pot to ground the wiper to what was the junction of R27 and R15 and the top of the pot to where R15 connected to R29. The reason the 508 has 10k there was to maintain levels for the line out that amplifier had.

If you want you can remove R7 also. If you need more bass change C24 to 50nf to 100nf but for overdrive you don't want a lot of bass going into the overdriven tube so stock value may be good for what you are doing.
You could also go all tube by moving the gain control to where R15 and R27 is and adding a master volume at R16 look around it has been covered in previous posts.

 

[DeanEVO_Dude]

It sounds like you are going to keep the exiting volume control as a gain control and then add a volume control after the first triode stage? As stated above in another post I would go with a 100k audio to a 250k audio pot for the volume control. Remove R15 and R27 connect one side of the pot to ground the wiper to what was the junction of R27 and R15 and the top of the pot to where R15 connected to R29. The reason the 508 has 10k there was to maintain levels for the line out that amplifier had.

If you want you can remove R7 also. You may want to change the value of C1 to 220nf the overdriven tube will sound better with less bass and reducing C1 will do that.

Yes, that is exactly my intent... To clarify, I want to put the wiper (onward towards R7 and pin 2 to gnd at minimum volume, right? So, counter-clockwise ties wiper to ground and clockwise (max volume) ties the input of R15 straight on to the tube (pin 2). Thanks.
What is the impact of removing R7? Will it change the tone (frequency respons)? or just the voltage going into the 2nd stage of the 12AX7 (level/volume)?

 

[jim p]

Yes how you are going to connect the pot is correct removing R7 will give you a bit more signal to the control grid it would matter more if you had a master volume at the R16 location for this mod not much difference.

 

[DeanEVO_Dude]

Yes how you are going to connect the pot is correct removing R7 will give you a bit more signal to the control grid it would matter more if you had a master volume at the R16 location for this mod not much difference.

Excellent! I have a 500K auido taper for "just such an occasion." :dude

To all who have posted replies, thank you very much! :AOK

 

[jim p]

Warm or cold bias?

Warm or cold bias? Being you are going to over drive the tube you may want to change how the first triode stage is biased. If you look through the posts you should find a link to a web page that goes through tube bias and tone. In short using a high value cathode resistor from approx 5k to 7.5k is cold biased with the tube near cutoff leading to a crunchy rock tone. Warm biased is when you use a low value approx 750 ohms so the tube is near saturation for more of a blues tone. If you have enough tube stages being overdriven sometimes the setup is 1st stage warm 2nd stage cold or the reverse. Using the op amp you will only have one tube overdriven with the volume control between the tubes.

PS: Was thinking about the warm and cold bias points a bit more and on the down side if you do this to the first tube in the amplifier it may limit your clean headroom. With the op amp because you can get less than unity (1) gain it may not be a problem. But if a tube by itself was the first stage the signal from the guitar could be great enough to cause saturation or cutoff. So with tube only it may pay to play with the bias point if you have a master volume pot connected to the EL84 and just on the second triode.

 

[DeanEVO_Dude]

Sorry for all the questions, as I said before, "I ain't no engineer"... lol

Any way, here is my current plan for the next step of mods on this amp (added the 500k volume in place of R15 and R27). The amp is still too loud, so I want to make the following changes:
R10 - 68K (still debating this)
R13 - 150K
R14 - 68K
and add 27K in series with CW-1

The rest of the circuit around the op amp remains unchanged. What are the effects of these changes on the frequency of these circuits specifically, will/should I need to adjust the values of any of the 4 caps (C21, C24, C26, and C27) to keep the frequency response (for the most part) unchanged (I don't mind if it gets a little darker, just not brighter).

By the way, jim, I am thinking about your suggestion on changing C1... Undeceided as yet. Thinking about a switch to swap 2 or 3 different cap values there. Still may remove the op amp altogether in favor of your "straight to the 1st triode" with the high freq. emphasis circuit.

 

[jim p]

Too loud?

I have to take some more time to see what effect some of the value changes you are posting would have on the frequency response of the op amp circuit. Changing R10 will have no real effect on this amplifier if it was a tube amp with it connected to the control grid it would lower the high frequency response. You say the amp is still too loud? So that makes me think you want an overdriven amplifier sound at low volumes, if that is the case you may need to consider adding an attenuator such as an l-pad which you can find in previous posts. The other way to go is to add a variable voltage regulator circuit to reduce the plate supply of the EL84 that is also covered in earlier posts.
Going back to the op amp circuit increasing the value of R13 is not a bad idea you could even remove it. One thing you do not want to do is to have high gain in the op amp circuit so you have clipping in the op amp so removing or increasing R13 will lower the overall gain in the op amp stages. You can also lower the value of R19 and R20 to increase the supply rails of the op amp for more headroom in the op amp stages say to 50 or 75 ohms instead of the stock value of 150 ohms.

 

[jim p]

Standby switch?

If you are thinking about adding a standby switch this Carling switch model 2GG51-73 that they have at Antique Electronic Supply (P-H520) fits right in place of the stock switch http://www.tubesandmore.com/?OVRAW=marshall+amp+parts&OVKEY=amp+marshall+part&OVMTC=standard I don’t want to get into the debate of need for having a standby switch. In the past I did not think they were necessary over time through some of the things I have read about tubes I think it can’t hurt the choice is yours.

 

[DeanEVO_Dude]

I have to take some more time to see what effect some of the value changes you are posting would have on the frequency response of the op amp circuit. Changing R10 will have no real effect on this amplifier if it was a tube amp with it connected to the control grid it would lower the high frequency response. You say the amp is still too loud? So that makes me think you want an overdriven amplifier sound at low volumes, if that is the case you may need to consider adding an attenuator such as an l-pad which you can find in previous posts. The other way to go is to add a variable voltage regulator circuit to reduce the plate supply of the EL84 that is also covered in earlier posts.
Going back to the op amp circuit increasing the value of R13 is not a bad idea you could even remove it. One thing you do not want to do is to have high gain in the op amp circuit so you have clipping in the op amp so removing or increasing R13 will lower the overall gain in the op amp stages. You can also lower the value of R19 and R20 to increase the supply rails of the op amp for more headroom in the op amp stages say to 50 or 75 ohms instead of the stock value of 150 ohms.

Yeah, too loud for me... Just slight turns of the dials, if 7 o'clock is at min, going past 8 o'clock is loud. I need "baby is sleeping, shhhhh" kind of volume with the dials that low (yeah, no amp overdriven, that what pedals are for). I am just trying to get a minimium amount of gain out of the op amp. I have been using an online "op amp gain calculator" to determine my resistor values. Basically, what these values give me is at 12 o'clock on the "gain" knob a gain value of 1.2 or so, max on the dial gives about a 4.8 (that is total from input on 1st stage to output on 2nd). I like distortion and boost from those little boxes you put between your guitar and amp. And, yes, I am try not to overdrive the op amp at all costs. So, with a gain of 1.2 on stage 1 and variable gain of .5 to 4.0 on the second, I should reach that goal. At any rate, one mod at a time... maybe the tone stack next... :deadhorse:
Anyway, thank you very much for your vast knowledge and your willingness to share it with us hackers. :thankyou

P.S. If it is of any help, my first tube amp was a Fender Champ 600 RI... talk about not loud at all, even when cranked from what I remember. Nice amp, should have never sold it.

 

[jim p]

Volume problem?

Thinking about your problem with the volume level makes me wonder if it is just the sensitivity of the controls that is the bother. On the volume control you just added maybe a lower value pot would have been the better choice. You could also put a resistor in parallel across the pot to reduce its sensitivity say 100k you could use the one you removed at R15 if it is still in one piece.

 

[mars2010]

hello, i've read through all these mod posts and i've done some minor changes to my v5. i changed the stock speaker for a jensen mod 10-50, i changed the sovtek 12ax7 for a groove tubes 5751, i changed the sovtek el84 for a mullard el84. i get a nice clean sound up to about 6 on volume, then a fuller overdrive sound past that. i keep the tone between 6-8, the bass is tight, the highs and mids are well balanced. i tried the amp out live with drums and piano in a small church, i actually had to turn down to about 4-5 on volume to blend in nicely. overall, i love this little amp and after a lot of research i think these simple mods made it much better...

 

[DeanEVO_Dude]

Thinking about your problem with the volume level makes me wonder if it is just the sensitivity of the controls that is the bother. On the volume control you just added maybe a lower value pot would have been the better choice. You could also put a resistor in parallel across the pot to reduce its sensitivity say 100k you could use the one you removed at R15 if it is still in one piece.

After a little more playing on the amp, I think you are right on your diagnosis, Dr. :dude I think that I will get a 250K pot and try that instead of the 500k I have in there now. So far, I am liking what the amp is sounding like, though I am leaning towards your mod for removing the op amp from the circuit, though I have not done my gain-reducing mods yet (this weekend's project).

For those of you parusing this thread who have one of these amps, the speaker that I chose was an Eminence Ragin Cajun (CL purchase 6 month ago, $40). I have a Eminence Redcoat Ramrod in my H & K Edition Blue which I like alot. Some day, I might try that in this little V5.

 

[deafelectromark]

Glad to hear about your simple success

hello, i've read through all these mod posts and i've done some minor changes to my v5. i changed the stock speaker for a jensen mod 10-50, i changed the sovtek 12ax7 for a groove tubes 5751, i changed the sovtek el84 for a mullard el84. i get a nice clean sound up to about 6 on volume, then a fuller overdrive sound past that. i keep the tone between 6-8, the bass is tight, the highs and mids are well balanced. i tried the amp out live with drums and piano in a small church, i actually had to turn down to about 4-5 on volume to blend in nicely. overall, i love this little amp and after a lot of research i think these simple mods made it much better...

You're on the right track.:applause
Mark

 

[bfglp]

hey new guy here. my v5 arived today nice cheep auction buy. swaped the junk plastic speaker for a clestion g10d 30 i had laying around, made a huge diffrence.

is there a mod for just bypassing the opamp?

 

[jim p]

No op amp mods

There are a couple of mods posted for how to bypass the op amp #168 here http://www.thefret.net/showthread.php?t=9379&page=9 is one that I posted and there are a few more.

 

[bfglp]

thanks thats exactly what i wanted.

 

[jim p]

Belton Digi-reverb PCB

I am in the process of getting together some reverb kits for three people at this point. The cost is approx 55 bucks for the DIY you assemble the PCB kit using the Belton Digi-Reverb module. I have posted information about it here http://www.thefret.net/showthread.php?t=9379&page=21
If you are interested you can get a hold of me over at SEwatt http://www.sewatt.com/forum by posting a message to Fondue, thanks.

 

[jim p]

Low budget Belton reverb mod

The following are instructions and schematics are for a cheep way to add the Belton Digital reverb to the Valve Jr amp, but the Crate is similar so you can basically do the same thing. If you use the +15 volt supply for the +5 volts install a resistor of 62 to 82 ohms 1 watt to 2 watts in series with the regulator. Best to go with the TO 220 regulator and a 62 ohm 1 watt resistor in series.
Cheep reverb mod with Belton module on stock VJ or similar amplifier. The input signal to the reverb module is going to be a voltage divider connected to the plate of the first triode after the coupling cap. You can go with a direct connection of a 220k resistor in series to the input of the reverb module or use a 2.2nf to a 4.7nf capacitor in series. Having the capacitor will reduce the bass into the module and increase the gain at low frequencies of the first triode. Taking the input of the reverb here will reduce the gain of the first triode by approx 20%. Also if there is a tone stack or tone shaping network before the volume control the reverb input and output will bypass it. For the output of the reverb a 10kA to 25kA pot connected to the reverb out will act as a level control. The wiper of the reverb level pot should be attached to the control grid of the second triode through a 220k resistor. Another 220k resistor should be installed between the control grid of the triode and the wiper of the volume pot. These resistors will raise the impedance of the control grid making it more sensitive to noise pick up. So they should be installed at the socket pin of the tube.
The power for the reverb module will come from the heater supply. Using two Schottky diodes with the anode of one connected to one of the heater secondarys and the anode of the other connected to the other anode secondary with the cathode tied together. Connected to the cathode should be a 2200uf 16volt cap this will provide approx 7.6 VDC for the input to a three terminal 5 volt regulator. You should use a LDO (low dropout voltage) regulator for this Mouser has this in a TO 220 package LD1117V50 you should be able to use a TO 92 package as well such as this one LM2931AZ50R with a power dissipation of approx 300mW max. At the output of the regulator I would install another 2200uf 16 volt cap. This power supply implementation requires the amp to have a DC heater supply if not you will need to add a full wave bridge rectifier for the raw supply into the +5 volt regulator. You can find the data sheet for the Belton module here http://www.belton.co.kr/index.php?mm_code=75&recomm=B&class_code=CLS0002105 they have the module for 15 bucks at Antique Electronic supply I would go with the medium delay.
I do not think this is the best way to install the module into the amp but it is the cheapest way to go.
Pin connections to module
Pin 3 to volume control ground.
Pin 4 to 220k resistor connected to coupling cap of first triode stage.
Pin 2 to top of reverb level pot
Pin 5 to ground side of heater filter cap
Pin 7 to output of +5 volt regulator

 

[bfglp]

finnished the no opamp mod and im very pleased with my v5 now. this mod and a celestion speaker give me nice bell like tones with my strat with moderate tube brakeup when cranked. thanks!

just wanted to add that it now sounds more like my ol champ. i also pluged it into my 210 closed back cab with g10 35's and broke out my les paul :happy sent me to tone heven.

 

[Monodexterous]

Mission Accomplished

Short story told long... My son is an aspiring blues harp player living in NYC. We chatted often about the virtues of tube amps in creating that wonderful overdriven sound from the early blues recordings. He bought a Crate V 5 from GC in NYC maybe 2 years ago. It had some difficulty right off the bat. The magnet fell off the speaker!? you can imagine the effect that had on the sound, which was already cheesy because of the flimsy stock speaker.
Anyway, he brought the amp home to Philly, and left it with me while he was touring in a traveling theater production. I replaced the stock speaker with a Jensen C10R. I was concerned about getting a speaker with a larger magnet because of potential size issues. No problem it fit right in an the improvement in sound was apparent and impressive, altho a little harsh an no bottom end. Googling Crate V5 mods, i came upon this site and thread. It was my good fortune to read Deafelectromarks assessment of the design and his comments about the simple mods he did which apparently had a great effect on the sound of this little amp. I corresponded with Mark, and being cautious about doing such a mod myself and fearing electric shock or worse, I sent the whole chassis to Mark. Mark and I dialoged many times about the progress, during which I asked him many inane questions about guitars, amps etc. My naievete was obvious but he answered my questions in thoughtful and informative manner. When I got the amp back, and turned it on, I was a little disturbed; weak sound and not real loud. Shortly thereafter a loud squeal really freaked me out. Bad power tube? I tapped the stock Sovtec EL84 and yes, it did crackle and pop. Out it came and in went a vintage GE EL84 Mark had sent along with the amp. Ahhhh! Much better, tho not a huige amount of overdrive. Corresponding with Mark about my concerns, we deceided to go with a new JJ EL84. I bought two matched from Tubedepot for 17.95 on sale. When they arrived i tore open the box, plugged one in with a new Tungsol 12AX7 and WOW!. Sweet sparkly clean tones and a throaty OD tone I was hoping for. My son came home for TG and we jammed a bit. He was totally enamored with the sound of this amp now. His harp mike will OD the amp when on about 5. With a vocal mike, it creates a Little Walter sound, and a roomy almost reverb effect. My Strat with the amp on 6-7 reminds me of Live at Leeds or some of the brighter ACDC tones. So, thanks Mark for deconstructing this little gem and bringing it back to life.
PS: My son is giving me back my BJ and taking the CrateV5, believe it or not, the Crate sounds better!

 

[SciHi]

Sold

hey new guy here. my v5 arived today nice cheep auction buy. swaped the junk plastic speaker for a clestion g10d 30 i had laying around, made a huge diffrence.

is there a mod for just bypassing the opamp?

So finally just sold the v5. Fun experience, it was sounding real good, took it to Marshall territory, with a similar Celestion G10-30 speaker, dual inputs, opamp removed, normal channel marshall tone control, and master volume, $160. I feel fair price to both parties...

 

[lute760]

Enquiry

Step by step modifications done to Crate V5 amp

1) Remove the amplifier from cabinet. First remove speaker jack then the six screws holding back cover of amplifier then with amplifier upside down remove four screws two on each side of cabinet that hold amplifier chassis in cabinet. (Note: you may want to enlarge the holes slightly in sides of cabinet and on back cover to make reinstallation and future removal easier)

2) If you haven’t already done so (you do have this unplugged right?) get out a dc voltmeter the highest voltage in the amplifier is approx. 320 volts DC measure from chassis to R25 should be 0 to 15 volts if so you are safe. This amplifier has a bleeder resistor R25 so supplies should drop after power down.


3) Remove preamp (12AX7) and power tube (EL84 6BQ5) put them some where you wont break them.

4) Next remove knobs on front panel may require flat blade screwdriver and a thin piece of wood to work against to prevent scratching front panel. The pots are D shaft type walk then off gently. Then remove nuts holding pots and ¼ inch jack on front panel.


5) Now make note of all the connections to the PC board because you are going to remove them. If you have a digital camera now is a good time to use it. Also if you print out the schematic note wire color and location on it. The faston connectors J4 J5 J1 and J2 may be hard to remove don’t break them of pcb by working them back and fourth.

6) Next remove the six screws that hold PCB into chassis and take it out. (hope you are putting parts someplace you wont loose them)

PC Board modifications
(See attached pictures of mods and changes to schematic also pic DSCF0947.jpg in previous post is the pre emphasis mod the tone mod is incorrect in that post tie unused side of pot in tone control to wiper not ground or unconnected up to you)

1) You are going to be removing approx 10 parts. You will need solder, solder wick, soldering iron, needle nose pliers and desoldering tool. In manufacture the compnet leads have been bent so desolder a componet lead then straighten it before removing or you may damage PCB plated feedthrough.

2) This modification will use the two Op Amp stages for an input buffer and small gain to over come loss due to pre emphasis circuit that will be added. Desolder and remove volume pot from PCB. Next remove R13 this makes IC1-A a unity gain buffer. Remove C26, C24 and C27 replace C24 with a 47nF 50-100 volt poly cap.C24 sets the low frequency limit at input to the amplifier with 47nF this is approx 125 HZ 3db down (for more bass use 100nF). In the place of C27 install a 33k ¼ watt resistor this equals a gain of 1.22 for IC1-B (want to keep gain low so first stage tube will clip before the Op Amp with overdrive).
ERROR Value of C24 should be 100nF lowest frequency from guitar is 82Hz.


3) Pre emphasis circuit For the tone control to be able to cut, boost and be set for flat response the high frequencies need to be boosted first. So C25 needs to be removed if you want replaced or use it again for this mod. Install one lead of a 100nF 50-100 volt cap into plated hole (via) that is connected to pin 7 of IC1 in the second hole of C25 insert lead of 33k ohm ¼ watt resistor with a 10nf capacitor accost it then connect the other lead of the 33k resistor to the second lead of the 100nF capacitor. If you want full treble brighter you can lower value of R2

4) Tone stack and volume control Here we will put volume control after tone stack and first tube stage so you will be able to overdrive input tube and still control volume. Remove C5 C6 C28 and C4 Change C6 to a 22nF 50-100volt poly capacitor. (Here a lower value cap will raise where the tone control will cut the highs higher value will lower it.) Now the volume control remove R15 and R27 using the volume pot removed from the board you will need to bend the leads 90 degrees towards the back of the pot to attach 1 ½ inch wires to the three terminals of the pot. Also need to insulate PCB were pot was attached to prevent shorting (three layers of electrical tape works) looking at the front of the pot as use to be connected to the PCB the right side terminal connects to the plated hole C28 that connects to R29 the center terminal (wiper) connects to the plated hole of R27 that connects to R7 and control grid (pin 2) of the 12AX7. The last terminal goes to the plated hole of R27 that goes to ground. (note be careful the leads soldered to pot do not short to metal back shell of pot no sound out of amp)

5) Oscillating power tube in testing the amplifier found output did not clip symmetrically and oscillated when clipped. Based on the tube data sheets the cathode biasing is to high in value. Change R17 to 270-300 ohms 2-5 watt or parallel the 330 5 watt with another 1.5k ohm 2 watt (270 ohms)


6) That’s it now put it back together and be careful around high voltage always follow one hand rule working on tube amplifiers. The one hand rule is make sure other hand and body are not tied to ground other hand does all the probing. So tie meter or scope ground to the chassis ground then do all your measurements.

Other tweaks
From the way this amplifier is set up it may have had gain, tone and volume controls?
And they took the volume control out instead of the gain control so if you add a third 250k pot across TL01-B same as in the stock schematic this will be a gain control you should add a 27k resistor in series to set minimum gain at unity (1).

Lowest frequency amplified the stock value of C24 is to low 3db down at approx 270Hz the value in the mod is 47nF for 125Hz if you want you can go bigger 100nF but this may increase that annoying 60 Hz hum we have all come to love.
ERROR Should go with 100nF lowest frequency from guitar is 82Hz

On the pre emphasis mod you can change the value of R2 to increase or decrease the brightness of the maximum tone. Higher value for R2 (stock 100k) will reduce the maximum lower value increase it. If you lower the value you may want to increase the gain in the Op Amp stage to offset the loss.

Tone control pot from my results the tone is flat at the 9 o’clock position so if you use a 100k (125K) pot for the tone control this will move it to the 12 o’clock position.
Changing where the tone control operates you can reduce the value of C6 to raise or lower where the tone control operates but you should change the value of the cap in the pre emphasis circuit also (10nF across 33k ohm).

I just picked up a V5 for 20 bucks at a yard sale and wanted to try your mod,but the attachments seem to be gone.Can you repost them?

 

[jim p]

no op amp mark ups

I found the mark up and picture to go with the no op amp modification that is part of posting #168. Here are links to them http://i1020.photobucket.com/albums/af330/vactube/noopampmodification.jpg http://i1020.photobucket.com/albums/af330/vactube/noopampmodificationschematic.jpg I would call or e mail Crate to get a PDF of the schematic for the amp. All the postings that now have no attachments are almost worthless, like a car repair manual with no illustrations, but it is what it is.

As always the stock speaker is junk and the output transformer is really a 16 ohm output. For more ideas on amp mods with postings you can try Sewatt

PS without the op amp to get a treble boost change the first cathode bypass cap C1 to a 470nf minimum voltage rating 16 volts.

 

[Infernie]

Hi Guys,

I have just laid my hand on a stock Crate V5 for a cheap price. I'm going to order a new speaker and some new tubes but i want to go even further with the modding. That's how i found this thread.

I've skimmed through the pages and decided the first thing i want to do is the Gain/Volume control mod of post #147. I hope i can find some pictures somewhere or else it will be a bit tough to do.

I've yet to decide wheter to do the no op-amp mod of post #168 or not. I don't know what i will gain with it? How does it influence my sound?

One more question: are there any mods i can try to get a good warm clean sound? I mean a sound like used in this clip:Youtube: Slow dancing in a burning room or a bit more crunchy like this: Youtube: Lenny - SRV.

Anyone knows if this is possible with this amp and a stratocaster? What should i do after i did the gain/volume control knob mod? I plan to build a tubescreamer so my amp should do a good clean sound i guess?

Thanks in advance and i owe you much if you can answer my questions.

Keep on rocking!

*EDIT*

I found an interesting mod online. I tried to make the scheme out of it.

This is the orignial link: CLICK
This is my scheme: CLICK

Do you guys think this will work out and how will it work out soundwise?

 

[Christopher Whitlow]

Another way to modify the amp would be to use the tone pot for a volume pot and the volume pot for a gain pot. This involves no cuts just jumpers and removing components with one being replaced (C24)
1) Remove PCB from chassis
2) Remove R13 C26 C24( to replace with 47nf for more bass or keep as is if you wish) C6 C5 C4 and R27
3) Replace C24 with a 47nf
4) Jumper junction of C6 C5 and CW2 (tone pot) to junction of R27 and R15
That’s it now the volume pot will control the gain of 2nd stage op amp for overdrive and the tone pot will control the volume.

I introduced myself a moment ago in the newbie section.
Got this amp free on a trade with an Emminence Legend and JJ tubes. Really want to do this simple mod first, has anyone completed it yet? This is my first tube amp and it was free so what the heck right?
I only have one question, would a 12aT7 work for me to lower gain a tad? I just want a tad more headroom with a bit less gain. The loss of tone control doesnt really bother me, thats why I put nice CTS pots and treble bleeds in my guitars and my pedals all have tone knobs!
Jim and the others... wow! great info thanks so much for posting all the replies!

 

[tunghaichuan]

I only have one question, would a 12aT7 work for me to lower gain a tad? I just want a tad more headroom with a bit less gain.

Welcome to the forum.

If you want a lower gain 12AX7, try a 5751 or a 12AY7/6072.

The 12AT7 isn't a lower gain 12AX7, it has different specs and operation points. Other than sharing the same pinout and dual triode configuration, the two are more dissimilar than similar.

Having said that, there is nothing wrong with trying a 12AT7. It won't hurt anything, and who knows, you might even like the tone.