Crate V5 mods... anyone?

[SciHi]

Is this thread dead? HELLOOOO!!!

HELLO and welcome. Jim P. had posted very early some fixes if you want to keep the opamp, I think most of use just removed it and modded from there... It is hard to get much headroom, at any volume, out of a single EL84. You can get good overdrive and it will get loud when the EL84 is being driven hard but none of the little 5 watt single end tube amps have much for clean headroom. The speaker is probably the biggest single improvement to the amp, in my opinion, the most important first mod. My experience is the tubes have much less impact, unless you want to run a lower gain tube such as a 12AY7. Put in a decent speaker, and keep the gain turned down and it should at least be usable.

 

[cebreez]

Thanks SciHi! I was feeling really alone in here! I understand what you are saying. I didn't see jim p's earlier post and what I'm finding out is the older post seem to lose there pictures. Could just be my crappy computer though. I understand what you are saying but let me interject with a personal observation and please feel free to call me foolish. Like I said I know just enough to be dangerous. I built successfully the "Noisy Cricket" amp and at first was very pleased till I realized for old deaf ears it just was not loud enough and broke up way too soon. I know why and thats okay but before I took the soldering iron back to it I did a little test and plugged it into my pedal board to see how close it was to an overdrive circuit. It just made everything louder, much much louder but did not overdrive or distort the signal at all. Why.... ? My point is I believe the op amp circuit in the Crate V5 is doing exactly the same thing. It is not there to overdrive the preamp tube just to compress and amplify the input signal giving us more headroom. When I changed out speakers I got phenomenal results from a relatively cheap speaker with a bigger magnet. Now i would like to use the input circuit(the op amp) and extend the frequency range (more lows and highs) on command with a better tone circuit. I like the op amp because there is so much you can do in that little space and never have to touch the tubes or drive circuit. Like putting a performance chip in your car or cleaner gas and getting better performance without having to crack open the engine. I hope all this makes sense.... it does in my head but then again that is another matter. HA!

Thanks SciHi....

 

[cebreez]

P.S. I saw jim p's original post but none pictures were there to show what he did. The guy really knows what he is doing but I had a hard time following his explanations. I wish I had been a member then and gotten into the discussion. I believe he was on the right track but I would have loved to coax him into a different direction. When I get this figured out and eventually I will, I will do my best to post the schematic markups. I totally disagree with the "sledgehammer" idea. This amp is a real sleeper and has almost everything you would find in amps costly "x infinity" more. I am thinking too about a different output transformer to boost this to a 10 or 15 watt amp but haven't gotten past the input circuit yet.

 

[tunghaichuan]

P.S. I saw jim p's original post but none pictures were there to show what he did. The guy really knows what he is doing but I had a hard time following his explanations. I wish I had been a member then and gotten into the discussion. I believe he was on the right track but I would have loved to coax him into a different direction. When I get this figured out and eventually I will, I will do my best to post the schematic markups. I totally disagree with the "sledgehammer" idea. This amp is a real sleeper and has almost everything you would find in amps costly "x infinity" more. I am thinking too about a different output transformer to boost this to a 10 or 15 watt amp but haven't gotten past the input circuit yet.

You might have to replace the power transformer as well as the output transformer. Boosting the amp from 5 watts to 10-15 watts is not as easy as it might seem. There are several ways you could go about it.

You could add another EL84 in parallel to give you 10 watts, but you'd have to use an output transformer with half the primary impedance as the existing unit. You'd have to replace the power transformer with one that has double the current capacity as the stock unit.

If you wanted to move up to a larger, single power tube, you could probably get 10 watts out of a 6L6GC tube in SE. But again you'd have replace both stock transformers with appropriate new units.

For 15 watts in SE operation, you'd need to go to a 6550 or a KT88.

All of the above are for single ended operation, and the larger the tube, the heavier the transformers get to handle the increased current. These transformers also tend to be very expensive.

You could completely gut the amp and build in a push pull circuit using two EL84s or 6V6s. But then you have to add a phase inverter to operate the amp in push pull. This is in addition to the existing preamp circuit. The transformers would be smaller and lighter, but the question is: do you have enough room in the chassis for the extra circuitry?

Modding a 5W amp into a 10-15 watt amp is not an economical way to get a killer practice amp. Really, you'd be better off buying a commercial amp that already has the features you want.

 

[cebreez]

I totally get what your saying and all options that I have considered. Wasn't thinking about the power transformer, good point. Definitely not enough room to start adding more tube circuitry. Larger tube...? Well...? Maybe. Expense is definitely the issue. I have a larger tube amp but not really wanting to go that route. Want to keep this one small and compact. Played with my BBE Sonic Maximizer in front of the Crate today and love the tonal difference it made. Gave it clarity and very nice harmonics. Liked it so much I ordered a pcb for a look-a-like on "madbeans.com". Might try to incorporate that on the input or in place of it. Also considered a nice 4 knob preamp pedal circuit for the same reason. Would add the necessary gain and EQ on the front end while still keeping it clean and low noise.

 

[cebreez]

I know a couple of good pedals in front of the Crate would probably do more for the tone than all my tinkering but I really want to keep this thing portable with no extra pedals to carry or plugs to plug in.

 

[SciHi]

... Now i would like to use the input circuit (the op amp) and extend the frequency range (more lows and highs) on command with a better tone circuit. I like the op amp because there is so much you can do in that little space and never have to touch the tubes or drive circuit. Like putting a performance chip in your car or cleaner gas and getting better performance without having to crack open the engine. I hope all this makes sense.... it does in my head but then again that is another matter. HA!

Bent on keeping that opamp, well check out Verne's posts over at HC, "Supercharging a V8." http://acapella.harmony-central.com/showthread.php?1519445-Supercharging-a-V8

The V8 is the V5's big brother. First thing Verne did was put in a high quality chip! Replaced the TL072, check it out, and Verne is still around and could help out keeping the opamp intact. You can compare the schematics and see where the V5 cut a few corners to "cheapen" up the amp.

Here is a favorite quote of Verne's:

"The problem with the opamp implementation as found on the V8 – particularly the hiss and extremely low amount of clean headroom – isn’t the USE of an op-amp, but the CHOICE of op-amp. The TL072 is a cheap [20 cents in quantity] component that probably introduces as much noise as using a tube, so it defeats the purpose. Because of its low headroom, it actually introduces a bunch of noise that keeps you from really cranking the gain to its sweet spot.

The “fix” is to replace it with a TLE2072. This is one of Texas Instruments Excalibur series and is renown for being the best of the best. You can get this chip from Mouser for around $2.50. The only complicating factor is that SLM soldered the TL072CN to the circuit board."

 

[cebreez]

Awesome.... Im checking it out now! Thanks SciFi!!

 

[jim p]

A big problem for headroom in the V8 is the power supply for the op amp is only +/- 8volts so you can have clipping with low gain on the op amp. The V5 has +/-15 volt rails and you could up them to +/- 17 to 18 volts no problem if you want. I think any op amp is going to change the tone with approx 30 transistors and feedback inside the op amp it is not the same as going straight into a tube. The V5 is the V8 but using the gain control as the volume control and removing the volume control and line out.

 

[cebreez]

Yeahhhh.......... well....... :thwap I totally agree with you!!! I really do! Does make you wonder why the "geniuses" put it there to start with. Seems like a big waste of time and money. Honestly in the end I will probably do exactly what you are suggesting but in the meantime Im going to see what kind of fun I can have with this. Like you did...

 

[cebreez]

Anyone wanting to relive this discussion. Im starting my mods any day now. The new thread will be here: http://www.thefret.net/showthread.php/19149-Crate-V5-quot-MODS-quot-will-commence!

 

[nbs2005]

Links to the actual Mod pics

Hi, Trying to bring this back from the dead. I want to do the mod described by deafelectromark which is about the skill set I have. (OK, that might be more than I have). I'd really like to see some of the pictures that were posted for that back in the day and are now dead links. It would really help me in my project.

BTW, this has been a great thread.

 

[marnold]

Hi, Trying to bring this back from the dead. I want to do the mod described by deafelectromark which is about the skill set I have. (OK, that might be more than I have). I'd really like to see some of the pictures that were posted for that back in the day and are now dead links. It would really help me in my project.

BTW, this has been a great thread.

I think you may be out of luck since he hasn't visited The Fret in over seven years. You could try emailing him via his profile and hoping against hope that he has the same email address.

 

[nbs2005]

I sent him an email. It did not bounce, but I haven't heard anything back either. If anyone has done this mod and is still on the board, I'd greatly appreciate a picture of the work done.

Thanks,

J

 

[nbs2005]

Hey all, one more update. I took the v5 to Steve Moratto, he's an amp builder in Ajax just outside of Toronto. For $125 Canadian, he turned this into a pure tube tone monster. That included new pots. He's a great guy with a great reputation in Ontario. You can reach him here http://www.morattoampshop.com/ And no, I'm get nothing for this; just wanted to promote a fellow Canadian.