Recent content by SciHi

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...

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...

I was talking with Rock Mumbles this evening and he reminded me of the power tube fixes for this amp. First, the screen resistor needs moved to the correct position, then the EL84 bias needs corrected, depending on the size of the cathode bypass cap, 240-270R cathode resistor. I also added a...

Since the stock tone pot has the wiper to ground, I converted it to a Marshall normal channel tone control. I can post a partial schematic for this mod when I return home after the 4th... http://mhuss.com/18watt/schematics/18wattLite.gif OK, maybe this will help.

Sold 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...

So does the volume pot actually work? Crate pots have a high failure rate, my master volume on my v18 broke near the ground, so there was no signal sent to ground, just a variable resistor in line, it was loud, ugly, and noisy. Use your vom to test make sure the pot has continuity to ground...

Missed this earlier, but many say that you should not use the 12at7 in preamp gain stage (designed for 12ax7), even more important in v1 position and with only one preamp tube. The 12ax7 may be too much gain, I would recommend going with 5751 if you want a lower gain tube (or reduce gain with...

For the preamp v1a and v1b cathode bypass caps are C1 and C8, so I run both of these at 1uF on the v5. I have dark HBs (DiMarzio) and really need to keep a tight bottom end and use the coupling cap (C2) and tone stack to limit the bass/gain in the preamp. The tone stack reduces significant...

I mic mine in church but only run the preamp gain on about 3 or 4. I spend a lot of time on SEWATT valve junior forum, most of the technical discussions are relavent to the v5 or any single ended amp. Here is a quote from cGil in regards to the EL84 (discussion is about vj, C5 = C9 on v5)...

I wonder if you haven't cut some volume by too low of bypass cap value on the EL84. I know lifting the cathode bypass cap is like a 1/2 power switch, I think this is what JimP was getting at with his post. I actually went higher value on the EL84 bypass cap, you can get low voltage 220 or 470...

So what else did you do? I put R11 (1M) across the input jack, removed R10 and everything between it and R1 (including R2), so R1 is the input grid resistor which should be in the range of 68K - 10K in most peoples opinion. A 1 M should reduce signal. I removed C3 but also moved the grid...

Right here: http://www.thefret.net/showpost.php?p=120172&postcount=28

I have found that the v1a cathode bypass cap and/or first coupling cap control the flabby bass. For HBs I have used either 0.68 or 1 uF cathode bypass caps, you can go a little higher with single coils, ~2uF. Or use a real small coupling cap, like the vj fender/voxy mod value, 0.0022uF, my v5...

That is correct. The other mods are for other reasons...

I posted this earlier: http://www.thefret.net/showpost.php?p=140280&postcount=261 Maybe a litttle more conventional SE master volume and it worked great. I know Jim has had the discussion earlier about the grid resistor before or after the pot (or grid load), but after the pot is a little...