Pre-Amp Tube Swapping - Crate TV60?

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I just pulled a Crate Turbo Valve 60 out of deep storage. It is a 60 Watt all tube amp -- well ... all tube except for its solid state rectifier -- tubes: 12AX7 (4), 12AU7 (1), and 6L6 GT/5881 (2) . Despite Crate's highly chequered reputation, the TV60 is quite a decent amp (if you learn to use the overly complicated controls). It can be made to sound very nice, very very nice.

My difficulty with this amp is/was that the volume taper sucks, which is why the amp was in storage. The amp is just not very versatile volume wise. The taper goes from zero/off to really #@&%'n loud immediately, then to insanely loud, and then finally to Crate's signature heavy-metal angry-hornet's-nest™. So there are only two useful volume settings - really #@&%'n loud and insanely loud. It has been cynically suggested online that Crate chose this taper as a show room sales feature – “Hey, kid! Listen to how loud this amp is at 0.25. Just imagine what it would be like at 11!!! Man, you would totally rock with this amp!” The amp, with this volume taper, is a pain, both literally and metaphorically. I want something more incremental for a volume taper. I would also like a bit more clean headroom.

So I am thinking about preamp tube swapping in the V1 and/or V2 positions, and I have been looking at Youtube videos that discuss and demonstrate the swapping out of various pre-amp tube models: ECC83/12AX7, 12AT7/ECC81, 12AY7, and ECC82/12AU7.







Any thoughts, suggestions or advice? Anyone familiar with this amp? Anyone know where I can find a schematic diagram or service manual?

Thx.
 

AcornHouse

Senior Member
Joined
May 22, 2011
Messages
8,023
Reaction score
1,052
Location
Bidwell, OH
Guild Total
24
You can find the schematic in this thread.
https://www.tdpri.com/threads/crate-turbo-valve-tv6212-schematics-and-wiring-layout.1059255/

But before you go swapping tubes, I would change the master volume pot to an audio taper pot. I had the same issue with my 1st gen Hotrod Deluxe. Yes, you can swap a 12at7 for the 12ax7, but that doesn’t fix the problem, it only lowers the overall level of instant loud. An audio taper pot gives you the ability to go from soft to loud more gradually, giving you more versatility.
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
But before you go swapping tubes, I would change the master volume pot to an audio taper pot.

Thanks for the link to the schematic. Thanks also for the advice.

:)

Unfortunately the Crate is not of a point to point construction with heavy duty high quality pots attached by wires. It is pretty much all circuit board mounted. My soldering/de-soldering skills are up to clear and obvious, spacious point to point work, but I don't trust myself with small scale, cramped, close quarters circuit board work, and with good reason.

I will see what a tech can do, assuming a pot of the right size and configuration and taper can be found.
 

AcornHouse

Senior Member
Joined
May 22, 2011
Messages
8,023
Reaction score
1,052
Location
Bidwell, OH
Guild Total
24
Thanks for the link to the schematic. Thanks also for the advice.

:)

Unfortunately the Crate is not of a point to point construction with heavy duty high quality pots attached by wires. It is pretty much all circuit board mounted. My soldering/de-soldering skills are up to clear and obvious, spacious point to point work, but I don't trust myself with small scale, cramped, close quarters circuit board work, and with good reason.

I will see what a tech can do, assuming a pot of the right size and configuration and taper can be found.
The Fender is the same way, my tech had to disassemble half of it to get to the back of the board. The pot you’ll need has tabs to go into the board.
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I have been phoning around repair shops, starting with the more reputable and then working down. Things go well on the phone until I mention that the amp is a Crate. Then I am treated like the I have the plague. I have been through five shops, all of whom have declined to accept the mod job. LOL.

The first and most reputable shop suggested putting a patched in passive volume control in the effects loop as the most cost effective approach to the master volume taper issue. The other shops mostly just said, "Good bye."

I quote from the guy at the first shop (more or less):

Why put money into an amp that you won't get your money out of because no one will ever want to buy it? You could probably sell the tubes and speaker from the amp for more than the amp itself. An effects loop passive volume control is useful and not just for this particular amp. It can be used with a lot of Fender Hot Rod Deluxes and Blues Juniors which have the same master volume issue, and it is easily resold.​

I will phone a few more places and then look at effects loop volume controls.
 

AcornHouse

Senior Member
Joined
May 22, 2011
Messages
8,023
Reaction score
1,052
Location
Bidwell, OH
Guild Total
24
You’ve got some very cynical amp techs there. When I had mine done, along with some other issues common to the Hotrod Deluxes, yes, it did make it a too expensive Hotrod Deluxe if I wanted to sell it and get back what I put into it. But, it gave me an amp that I don’t see the need for ever selling; one that does more, and does it better, than any other Hotrod Deluxe out there. (That hasn’t had the same mod.) As my tech said when we were testing it afterwards, “That’s the Fender sound!”
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
You’ve got some very cynical amp techs there.

Yes. Particularly the latter techs I called.

The first guy, however, was friendly and was just trying to give practical advice, I think. He was also very busy doing work on vintage point-to-point gear - he seems to be the local go to guy. He can pick and choose his jobs.

And Crate has earned themselves a bad reputation, both fairly and unfairly.

I remember reading a story in an amp forum online. A guy was relating how he was always getting dissed for his sound/tone at gigs because of his Crate amp. So he removed the Crate badging and replaced it with name plates from some junk machinery making the amp look like some boutique item. Suddenly he was getting compliments and questions about the amp. Amps, like books. sometimes do get judged by their covers.

I will persist here. I only paid $80 for the amp. There is room for some expenditure on the beast.

And it is an "interesting" amp with the ability to swap power tubes between 6L6s and EL34s. Crate claims the amp is auto-biasing in its power tube section. It seems to work. I like the Fender-ish sound of the stock 6L6s better than the Vox/Marshall-ish sound from the EL34s.

It also has a balanced attenuated XLR line out for connection to a PA system, indicating that Crate (hopefully) imagined the amp being used as professional gear. It is not a feature that would be added as a cost cutting thing. I have never used the amp in a situation where I needed more volume out of it, however, so I have never tried this feature.

The owner's manual:

 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
Ironically Crate tried to hide their bad reputation under a Blackheart badge.



Wonder if they tried to get a Jett endorsement.
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I may end up trying the FX loop vol control option if I can't find someone to do the circuit board vol pot swap out.. It is an inexpensive way to go. I dislike clutter, though, and this option is cluttery.

I can buy a ready-made one for $40+/-, or I can build one out of $20+/- of parts, less if I use the cardboard box option. ;)

Ready-made example:


Schematic, design drawing, and parts list at bottom of this thread:



Overly long and talkative instruction/demonstration video on building and using an FX loop vol control:



A humorous Russian builds one inside a cardboard gift box without soldering anything and then demos it:

 
Last edited:

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I stripped parts (pots and jacks) off a dead Trace Elliot Brat circuit board and salvaged pin connectors out of plugs to connect to computer motherboard Firewire and USB headers (this so I didn't have to solder to the pots and jacks which are designed to be soldered into a circuit board). I also cut up some old speaker wire - too heavy and inflexible for this purpose - oh well - live and learn. And I put it all together in a Ziplock refrigerator container which has become separated from its lid.

And it works beautifully, except that I don't like the audio taper on the 25K pot I used - something larger next time.

This all is only a proof of concept exercise, I will go and buy some good stuff now to build a real one.

Screenshot from 2021-10-06 17-02-32.png

The beast tamed below, sweeter and milder - notice how all the metal caps on the control knobs fall off on Crates of this age:

Screenshot from 2021-10-06 17-01-44.png

I will still probably try putting a 12AT7 or 12AY7 in V1.
 

Guildedagain

Senior Member
Gold Supporting
Joined
Jun 8, 2016
Messages
4,686
Reaction score
2,410
Location
The Evergreen State
You might be deluding yourself that this is a good quiet amp because it's too big and loud. It's a 50lb 60W amp, it's made to do just what you said it does, get crazy loud at the touch of the volume knob.

I recently switched to a single 6V6 Class A Champ style amp, while still possibly irritatingly loud in a bedroom context, it makes a much better sounding bedroom amp the my bigger louder amps, it's so much better, I could sell the other amps. Realistically, amps that big are only for playing with a band, made to be loud, and I shouldn't play that loud in the bedroom context, it's pretty rough on your ears over time.

If it's too loud, you're too old.

Truer words never said.


All that will happen by switching to weaker preamp tubes is less gain, possibly better headroom, none of which have anything to do with playing alone or in a setting where "it's too loud".

Also, the right pedal can really control overall volume, as any good preamp would.

I just landed on "the" holy grail pedal, a bit bulky but... quite possibly the best preamp-overdrive I've experienced to date, a B.K. Butler Tube Driver with Bias Knob, unreal, nothing like it, and I recommend turning up the volume on the amp, open it up and let the juice flow, and underdriving it with a preamp that has it's own filthy gain.

Your dream tone is not going to come from a big amp in a small room, but from a small amp made to be quieter than a gigging amp.

This is it for me, I can stop shopping and start shipping ;]

P1040254.JPG


This Garnet is very strange, builder may have been high... the TONE works in reverse, which is why it is turned like that, it works as a treble attenuator going clockwise, very strange, and the volume and reverb knobs are interactive. Any more reverb than this at this volume level goes and the reverb is way over the top. Turning all three knobs to ten gets you the best tone I've ever heard from a small combo, not loud, just perfect, and then there's that overdrive.
 
Last edited:

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
You might be deluding yourself that this is a good quiet amp because it's too big and loud. It's a 50lb 60W amp, it's made to do just what you said it does, get crazy loud at the touch of the volume knob.

I am just looking to see what if anything I can do with this amp. I may be only deluding myself that the Crate is a good amp. LOL. I suppose what I am looking to do is to see if I can transform a Crate Heavy-Metal Carrion-Eating Devil-Dog Dire-Wolf into an elegant gazelle of a Jazz amp. I do not dislike the amp. I paid next to nothing for it, but it has never been very useful to me.

When in the past, I compared it to a friend's 60s 100 Watt Fender Twin, I found that the Twin sounded better, way better (hey, no surprise here) and that the Twin was more versatile in that it would function well at a much wider range of volumes, including relatively low volumes. The Twin did not fully wake up until cranked a bit more but it could be employed in a wide variety of settings. It could be used in his living room without rattling the windows, doors, furnace ducting and pictures on the walls. Without the FX loop volume control or without a different taper master volume pot, the Crate cannot do anything except be LOUD.

An amp that would suit my current purposes, my 50s Gibson GA-20, I gave to the friend above as present in thanks for some great kindness on his part to my family, my parents - he had always coveted it anyway, both as a collector and a musician. It has now supplanted the Twin for jams and small gigs (in conjunction with his 50s Fender reverb unit) because the two can be loaded into the trunk of his car easily, neither needs castors, and there is no danger of getting a hernia while moving them about.

But anyway, I have a lovely solid-state 50 Watt Yamaha G50-112 II that does a pretty convincing impersonation of a warm clean tube amp thanks in part to Mr. Rivera. And it will play quietly, very nicely.

I also have my lovely 50s or ealy 60s 5 Watt tube head but this is a rock/blues monster at any volume.

View attachment 26458

This Garnet is very strange, builder may have been high... the TONE works in reverse, which is why it is turned like that, it works as a treble attenuator going clockwise, very strange, and the volume and reverb knobs are interactive. Any more reverb than this at this volume level goes and the reverb is way over the top. Turning all three knobs to ten gets you the best tone I've ever heard from a small combo, not loud, just perfect, and then there's that overdrive.

If you are not experienced in working with tube gear and do not know how to discharge capacitors safely (using your body is a very bad idea), leave the amp a week or more before opening it. Then have a look to see if the pots are mounted to the face plate and then old-school connected to the circuitry by wires or if they are soldered into a circuit board. If they are old-school wire connected, someone may have accidentally reversed the end connections on the pot. A connection between the ends should read the full resistance value of the pot (+/- a small percentage) on a multi-meter and should not change at all when the knob is turned. The third connection is the wiper - the connection for the contact that moves along the strip resistor in the pot, changing the effective length of the strip and thus resistance as it moves. A connection between an end and the wiper will change readings on a multi-meter either from the full value to zero or from zero to full value depending upon which way the knob is being turned and upon which end is connected with the wiper.
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I took the Crate apart yesterday, in part to clean it and in part to map the tube sockets. There is no indication on the outside of the amp as to what the sockets are, V1, V2, etc, and no indication of what tubes go in them, 12AX7 or 12AU7 (reverb). The sockets are numbered on the circuit board but not as V1, V2, etc, and it is only by reference to the schematic that their function can be ascertained.

The tubes are all original. I know this because I know that the person I bought the amp from did nothing with it. The 4 12AX7s are cheap no-name Chinese-made 12AX7As. A real, vintage, American-made 12AX7A is the holy grail of pre-amp tubes for audiophile systems. I doubt that the Chinese tubes are 12AX7As in anything but labelling. The 12AU7 is a vintage, American-made, Philips tube, probably acquired by Crate on the cheap as NOS. The 6L6s are Sovteks.

Interestingly and annoyingly, the pots soldered into the circuit board are not labelled with specs, but rather with Crate-proprietary parts codes. Doing a bit of Ralph-like digging through various amp forums, I found a post from an elderly repair tech who had Crate parts lists, which list pot values - good luck replacing a dead pot if you don't have access to the parts list. So, the problematic master volume pot in the Crate here is an audio taper pot but with a 15% taper rather than the 10% taper that would be more common for North American gear. At the half-way mark, a 15% taper pot reads 15% of rated resistance. It gets louder faster than a 10% taper. Whatever, the pots are cheap plastic shafted things.
 

Canard

Member
Joined
Sep 30, 2020
Messages
564
Reaction score
546
Guild Total
4
I searched around and found some relatively lowish mileage Fender-badged Sovtek 12AX7s from a Gen 1 Hot Rod Deluxe that had been upgraded to Groove Tubes, long, long ago.

I also found some quite low mileage and much newer JJ 12AT7s.

I put the 12AT7s in the V1 and V2 positions, and I put two of the Fender/Sovtek 12AX7s in V3 and V5, leaving the Philips 12AU7 in V4.

It is a totally different amp - quite well mannered with lots of clean head room, and the Master volume control works much better.

Channel 2, however, does not kick butt anymore. It was nice having this option. I will try putting another Fender/Sovtek in V2 tomorrow.

It would probably sound better again with new tubes rather than cheap used ones, but this was a very low cost experiment, and I am most pleased with the results so far.
 
Top