Search found 13 matches

by Liquids
Fri Oct 19, 2012 1:34 pm
Forum: Technical Discussion
Topic: voltage divider for screen grids
Replies: 93
Views: 31342

Re: voltage divider for screen grids

Is it better to have a 220K to ground from each screen resistor? Yes, this is the way you want it. Each screen resistor gets its own divider resistor to ground. Least amount of heat this way as well if divider resistor is a high(ish) value. Won't this cause each screen only to 'see' it's own voltag...
by Liquids
Wed Oct 17, 2012 3:56 pm
Forum: Technical Discussion
Topic: voltage divider for screen grids
Replies: 93
Views: 31342

Re: voltage divider for screen grids

Sounds good. Does this affect the voltages downstream to the preamp? It is an option - it can if you want it to; it can have no effect if you'd like things to otherwise remain as-is. It just depends how you wire it, intentionally or inadvertently... The voltage divider does create a 'load' on the B...
by Liquids
Tue Oct 16, 2012 1:51 pm
Forum: Technical Discussion
Topic: voltage divider for screen grids
Replies: 93
Views: 31342

Re: voltage divider for screen grids

The thing I was wondering about using a voltage divider to set screen voltages in an output stage is: Allowing for the required amount screen current, wouldn't you need to set up the resistances in the divider so that they pass a relatively high amount of current through the divider - such that any...
by Liquids
Mon Oct 15, 2012 7:52 pm
Forum: Technical Discussion
Topic: voltage divider for screen grids
Replies: 93
Views: 31342

Re: voltage divider for screen grids

Sorry to ressurect this. I've been messing with the concept of using a voltage divider for the screen voltage in my amp (Ampeg V4b). The V+ is 520-540+ volts depending upon where I plug it in...and in general, I'd like to reduce the screen voltage. I tried utilizing the center tap of the standard vo...
by Liquids
Wed Feb 29, 2012 8:57 pm
Forum: Technical Discussion
Topic: SRZ 6545
Replies: 20
Views: 7915

Re: SRZ 6545

Hard to make out the capacitor values from the photos - but they are much appreciated. The tone stack seems particularly unclear (250pf, 47n, 100n?), likewise I'd assume the mica cap across the phase inverter is probably smallish - maybe 47pf or 100pf but curious nonetheless. Does anyone have sharpe...
by Liquids
Mon Oct 03, 2011 2:04 pm
Forum: Technical Discussion
Topic: Mesa Lonestar Special schematic needed
Replies: 24
Views: 11897

Re: Mesa Lonestar Special schematic needed

I wired up a clone of the lead channel yesterday, and I liked it quite a bit. Instead of the EQ I just used a passive bass control, since I am running the preamp into my amp which has EQ on it. The preamp has a bit of that characteristic muddy tonality of 'dumble' style amps, so I'd say that some mo...
by Liquids
Mon Sep 26, 2011 7:52 pm
Forum: Technical Discussion
Topic: Ampeg V4 Hum Challenge
Replies: 14
Views: 7908

Re: Ampeg V4 Hum Challenge

selloutrr wrote:6L6 are not intended to exceed 500V it's a gamble using them in a V4.
Same gamble as running 350v maximum plate voltage rating 6V6s in deluxes and silverface champs, no?
by Liquids
Mon Sep 26, 2011 7:40 pm
Forum: Technical Discussion
Topic: Ampeg V4 Hum Challenge
Replies: 14
Views: 7908

Re: Ampeg V4 Hum Challenge

As a counterpoint: 7027s were probably re-pinned, high quality 6L6GCs with a rating of 35W rather than 30W. The Ampeg didn't make use of the 'extra pins' 6L6GC's so they're a direct swap on that level. JJ pins and brands some as 7027s if you MUST have them...even eurotubes says just use the 6L6GCs. ...
by Liquids
Mon Sep 26, 2011 6:29 pm
Forum: Technical Discussion
Topic: Mesa Lonestar Special schematic needed
Replies: 24
Views: 11897

Re: Mesa Lonestar Special schematic needed

The LSS is a good sounding amp IMO. It can be difficult to tweak, but there are alot of good sounds available. It doesn't have alot of headroom so tt can be a bit on the mushy and/or dark. It is often difficult to get the highs right, at least for me. The choice of rectifier playes a big part here....
by Liquids
Mon Sep 26, 2011 5:10 pm
Forum: Technical Discussion
Topic: Ampeg V4 Hum Challenge
Replies: 14
Views: 7908

Re: Ampeg V4 Hum Challenge

I'm a Ampeg V4(-b) owner and I love mine. Be sure to check out ampegv4.com if you haven't. Using a variac is not really necessary if you are replacing caps with quality electrolytics in the power section. If you were using NOS electrolytics or firing up the amp for the first time in x_years with all...
by Liquids
Sat Sep 24, 2011 12:00 am
Forum: Dumble Discussion
Topic: Building a Preamp
Replies: 10
Views: 2877

Re: Building a Preamp

Luthierwnc - my V4 is actually a V4-b, so no 'verb :wink: I took what I could get with limited cash, an amazing price, and the motivation to fix her up...and it's by far my favorite amp. I have two now, although the recent one is in pieces and awaits some TLC to get her running again. But I love the...
by Liquids
Fri Sep 23, 2011 3:30 pm
Forum: Dumble Discussion
Topic: Building a Preamp
Replies: 10
Views: 2877

Building a Preamp

I've got a tube-preamp prototyping chassis (it's legitimately cake pan) running in the last week or so. I love my amps (Ampeg V4) and I run any amps I play clean - very clean - and loud as possible in the setting, using drive from pedals I've crafted myself into a rack reverb/delay for space and dep...
by Liquids
Tue Aug 30, 2011 3:37 pm
Forum: Technical Discussion
Topic: Ampeg Reverberocket II GS-12R project
Replies: 11
Views: 9367

Re: Ampeg Reverberocket II GS-12R project

Nicely detailed posts! I just scored a Reverberocket 2. Mine seems pretty nice. I'm debating about a transformer replacement, though mine works fine (and the amp score - though cheap - left me broke for the time being)! Curious about the tone, and a 4 ohm tap would be nice. I really like the sound o...