|
Dirty-South Blues Harp forum: wail on! >
blues deluxe reissue for harp
blues deluxe reissue for harp
Page:
1
ludashoeless
6 posts
May 29, 2012
11:19 PM
|
I play guitar through a blues deluxe reissue and just recently picked up the harp. I'm just wondering, would my blues deluxe be a good harp amp?
Thanks
|
5F6H
1214 posts
May 30, 2012
7:27 AM
|
It's not the best amp in the world for harp...but it's not the worst either. It may be very touchy on the volume control, you might find input #2 easier to manage.
A lower mu PI tube (12AX7 next to the power tubes), like 12AT7/5751 might help...but of course this will affect the guitar tone too (this might not be a bad thing, they can be quite "woofy" amps).
If you are handy with woodworking tools & have a couple of speakers handy, converting to 2x10" might be a better compromise for good performance with both harp and guitar (the amp also has a 4ohm speaker tap isolated on the circuit board). Cannabis Rex gets a lot of mentions as a good 1x12" harp friendly speaker, but really for harp a 1x12" might struggle with feedback unless the bias is cooled off to >20mA per tube...& this may sound thin & sterile for guitar?
Otherwise, as you have one...& use it for guitar, you may as well use it for harp too, it'll handle at least medium sized gigs without needing to be mic'd.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
ElkRiverHarmonicas
1065 posts
May 30, 2012
10:39 AM
|
I'm no expert on amps, but could you resolve the touchiness by putting in a different potentiometer or putting a resistor in in the circuit in front of it?
----------
David
Elk River Harmonicas
Elk River Harmonicas on Facebook
"It's difficult to think anything but pleasant thoughts while eating a homegrown tomato." - Lewis Grizzard
"Also, drinking homemade beer." - David Payne
|
5F6H
1216 posts
May 30, 2012
11:17 AM
|
Indeed David, that's exctly what I have done in the past. The volume control is only 250K (with 100K in series beforehand), which sounds like it should be better for harp, giving more sweep. But the good thing about 1Meg volume controls is that they leave a significant amount of series resistance (best part of a meg) in front of the working portion of the pot (sometimes as little as 20-30K), calming down high end & resulting feedback. Increasing the value of R6 in the Blues Deluxe does the same thing, 470K works well, you could go up to 750K total for R6.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
Stevelegh
525 posts
May 30, 2012
2:36 PM
|
It's got every potential to be a great harp amp.
Read this:
http://www.justinholton.com/hotrod/
|
5F6H
1217 posts
May 31, 2012
1:34 AM
|
...or this...
Fender 1x12” Blues Deluxe/4x10” De Ville (not the ‘Hot Rod’ versions).
1) Re-bias Sovtek 5881, or Chinese ‘Coke Bottle’ 6L6 (softer attack, if a bit “fizzy”) power valves to 7-15mA for 4x10” De Ville or 15-20mA for Blues Deluxe/De Ville with 12”s, by increasing value of R87 bias load resistor (I would use a 100K 0.75W cermet pot, wired as a variable resistor). Fitting a resistor in parallel to R84, bias dropping resistor, to reduce its value, may also be necessary.
2) Increase value of R91, preamp suply dropping resistor, to 47K 3W. You are looking for 160v (+/- 10v) on plates of the 12AX7 in V1.
3) Replace C1, first stage cathode bypass cap, with 220uf 25v electrolytic cap, observing correct polarity.
4) Increase value of R3, input load resistor, to 5.6Meg, or 8.2Meg 0.5W.
5) Add 330K 0.5W or 470K 0.5W resistor in series with R6, resistor feeding the volume pot.
6) Try various valves (5751, 12AT7, 12AY7) in V3 (the phase inverter, next to the power valves). I normally find that subbing V1 & V2 with lower mu valves just results in a dull tone.
7) On the 4x10” Blues De Ville, rewire the speakers in parallel for a 2ohm load. Replace the speaker jack and extension jack set up with one standard shorting jack and isolate the unused speaker taps (8ohm green wire and 4ohm green/yellow wire). Connect the white, 2ohm speaker tap and the negative feedback loop to the hot terminal of your new speaker jack socket and the black common wire to the ground & switch terminals. Later 4x10” De Villes had ceramic Eminence speakers, I prefer the Eminence Legend 102 alnicos fitted to earlier amps.
8) The Blues Deluxe also has a 4ohm speaker tap, ideal for converting to 2x10” with just a new baffle board. When taking this route I’d recommend Phillips 6L6WGB, or TAD 6L6WGC biased to 25-35mA. If you can afford a new cabinet, then 3x10” is a possibility & highly recommended. Use three 8ohm speakers in parallel off the 4ohm tap. Use a 5751 PI valve & bias Sovtek 5881 power valves to 15-25mA.
Run the amp with the ‘Drive’ channel de-activated. The effects loop reduces losses in the input circuit when using an effect pedal, but also bumps up the gain… maybe preferable for low volume situations?
...principals apply equally to the Hot Rod models, but you have to account for the differing resistor & cap numbers.
The Blues Deluxe will take JJ6V6s with a rebias (brighter sweeter high end, but more compression, try 17-19mA) & factory recommended speaker load, this is because it uses a much higher primary impedance on the output transformer (~7K) than the Hot Rod Deluxe & either the Blues Deville or Hot Rod Deville (all around 4K, standard for Fenders with 6L6), thus you don't need to correct speaker impedances.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
Last Edited by on May 31, 2012 5:05 AM
|
Post a Message
|
