Older Crate V1512 choke install question

[stevehoover]

Anybody out there install a choke on a V1512?

My extensively modded V5212 came out sounding killer (if any one is interested in the mods) but the little guy is giving me trouble.

I tried a 10h 100ma choke for a Vox AC 15 but the results were less than pleasing. Lower volume and when pushed hard the sound was thin and harsh.
It sounded like an impedance mismatch to my ears but that's just a guess.

Help, I don't know how to do the math!

[Enzo]

If you replacede a resistor with a chjoke in the power supply, then all the downstream voltages would have gone higher. I suspect that was the major affect on your sound. I don;t know what impedances would have changed.

[deci belle]

Steve— I'd love to hear about anything you may have done to your V15! The choke I installed from Mercury is a CloneTone MC10H, and it replaced R14.

What resistor did you replace? Maybe that's where the problem is?

[stevehoover]

V15 reprise

I haven't touched the V15 for a while, I need to revisit it.
I have learned a lot this year (I built a Lightning clone from scratch) and I plan to go back to the V15 to get it right. The one thing I noticed was how "dark" the stock speaker was.
Note to self: try other speakers before you start messing with circuitry.
The High end that I was looking for was there all along, the stock speaker was masking a lot of the chime that was already there. It sounded pretty cool with a WGS alnico clone but the cabinet layout wont let you mount one with out repositioning the chassis, (the magnet cover contacts the chassis in the stock layout).

Any thoughts on a better speaker for this amp would be appreciated,
the WGS alnico clone went into my lighning build. I would like to find something close the the stock crate as far as tone and breakup but with more top end for that EL 84 chime. Once I get the right speaker,
I plan to go back through all the mods that I did to the V15 and loose the lame ones and keep the stuff that really sounds good. I will post that for sure when I get there.

[deci belle]

I'll bet you have— hope to hear about any V15 mods you decide to tackle.
Some say a 100dB speaker is twice as loud as one with 97dB sensitivity.

Wondering when your V15 was mfgr'd. My board says 11/7/01.

Presently I'm using EL84 Mullards, a matched 12AU7 and two Tung Sol AX7s from Torres.
I've only added Mercury's OT and choke, and a ceramic Tone Tubby that's rated at 70w.

The issues I have are with the V15's gain and bass values. I generally play the amp at full volume with gain @ 2; bass @1/2 through a clean boost and/or OCD and leave the boost switch alone. I want to lower these thresholds so I can actually use all the knobs!

The mods I'm going to work through to tone down the gain and the bass are:
1. Remove C1 (1st stage cathode bypass), and if that doesn't lower the gain enough for me…
2. Lift C2 (2nd stage). Some people just cut C38 (3rd stage) instead of C1 +C2. If situations require more gain I can then swap in an AT7 or AX7 in V3(drive/reverb).
3. The V15 and V30 tone stacks are very similar and have R13 (slope resistor) that can be increased up to 100k (decreasing bass). Others have also lifted the V32's R31=220K to reduce its "boomy" quality. The equivalent resistor in the V15 seems to be R45=221K

Additionally, I'd like to consider creating a series effects loop using switching jacks, at the level pot/C22 to SEND'S tip terminal; C12 will attach to the RETURN jack's tip terminal (adding a jumper from level/C22 to RETURN'S tip SW terminal). SEND'S sleeve/sleeve SW terminals and RETURN'S sleeve/sleeve SW terminals go to ground.

V30's schematic shows that SEND'S tip SW terminal is lifted.


V32 palomino.pdf

With your recent amp-building experience, what are your thoughts on these mods, Steve?

[stevehoover]

V15 Mod thoughts

Try strapping a 220k resistor across R7 to reduce a little gain in the pre.
I also use a 12AU7 in V2 sometimes. Gain was my main complaint with this amp (too much gain). I didn't try the C1 lift that would definitely tame things down.

I ended up using the MM OT and choke and NOS tubes in my Lightning build.

The mid boost values that I have at present are R45 1meg and C41 500pf but I almost never use it

I like to have an adjustable slope control so I installed a 100k resistor at R13 and wired a mini DPDT toggle with a 33k at the top and 100k across the bottom and leads from either end of R13 to the two middle contacts.
It yields 50/100/25K for the slope resistor.

I changed the cathode resistor R22 to 190 ohms to try and run the EL 84's a little easier. They were biased really hot.

My board is from July of 01.

I don't know...I have mixed emotions about this amp. It was the first new amp that I had bought in many years, but PCB's are such a pain to work with.
Now that my Lightning based amp is finished (It's very different from a stock Lightning but absolutely rocks), I'm inclined to clean this one up and move it.
I can get enough out of it for a set of Iron for another build.

My latest build is a point to point, cathode biased single ended and KT66 powered with a JTM45/ JTM50 front end. Even point to point is easier than a PCB!

I like my V15 and My US made MM OT equipped V5212 really sounds great,
but they will be the absolutely last PCB amps that I own. You just can't believe how much easier and more rewarding a turret board or point to point amp is to work on. Orders of magnitude easier!
Cheers,

[deci belle]

Thanks for all the welcome suggestions, Steve— I especially like the cathode resistor mod you noted to ease up on the power tubes! But if the power tubes are running too cold, could that possibly contribute to the thin/harsh sound you described in your first post??

I'm with you on point to point— it's the logical evolution and I'm looking forward to it. I'll arrive when I've had it with the Crate school of ampage!

I will be studying all the mods you noted closely, and will consider the mid-boost values as well; I'm into baby-steps now and your feedback is sincerely appreciated, Steve!

[deci belle]

Try strapping a 220k resistor across R7 to reduce a little gain in the pre.

Without changes to the 2nd stage's (R6) cathode resistor, won't the change to R7 (plate load resistor) be creating an imbalance somewhere down the line?

[deci belle]

Cut the Caps

I removed the first two stages' cathode bypass caps (C1 and C5). In post#5, I erroneously stated removing C2— DON'T lift C2! Things are quiet and clean at full volume until around 5 on the gain knob, after which it starts to do it's class A routine. The change has tamed the boost switch/tone circuit, too. I'm running a buffered 48v 30dB clean-boost behind an OCD, that seems to be enjoying this mod. It's even good with ES-175 with boost on and the bass turned up to 2 (I used to have it OFF all the time).

[deci belle]

I highly recommend installing .47µF 50v capacitors instead of the 2.2µF caps in C1 AND C5, especially if using single coils.

Originally I tried no cathode bypass caps, but it wasn't a satisfying tone— even with humbuckers.

The .47µF caps provide a much more rounder sound than just running the gain stages without any cathode bypass caps— which lacked body to my ears. The .47µF caps butter up the signal throughout the gain settings. Without any bypass caps the amp sounded kind of weak and made a "motorboat" noise at max gain. The signal feels smoother now.

I'm able to use the full range of the gain pot as well as the bass and mid-range tone pots too. My V15 has never sounded better. As I stated earlier, I have a 12AU7 in the V3 driver/reverb.

[hoksila]

tube juggling

thanks everybody! great info...

[hoksila]

tube juggling

swapping an ay7 in v1-leaving ax7 in v2 and swapping an at7 in v3 i'm thinkin more clean head room a little sweeter more bloomy breakup,a little sweeter high end (ay7) and a little more sensitivity to touch and guit vol.pot.
I saw a cupla cats swapping an au7 in v1, but that just seems like it would just kinda lay there and not do anything (20v) i want the ev breakup but i want some gain stuff too. oh yeah, got a v1512 w a tone tubby for 175... sweet...
any thoughts or advice would be great. thanks.

[Guitarist]

Hoksila seems to have some great advise with the 12ay7. If you do this you can parallel the 100k plate resistor with another.
Pulling out cathode caps rarely helps the tone.

[hoksila]

ay7

hey guitar!
big improvement w ay7(40)in v1! where gain was already to hot at 8,9 oclock w ax7 now i'm clean up to 12,1oclock.Sweeter Breakup, way more responsive to touch and guit vol tone pots. i understand the function of the lower power ay in v1(input) but blind on a recomendation i put an at7 in the pi(v3).how does the lower power in the at7 effect the el's? is it doing anything?all it really does is split the signal to the el's as far as i know... well like they say... If it works,Do'nt Fix It !
It sounds great, particularly w my 67 epi riviera w minibuckers!!!
thanks yall !