Halffast
48 posts
Jul 07, 2016
6:14 AM
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Based on research and youtube videos , I've got a Special 6 on the way . I like the sound of this amp stone stock but know it is commonly modded in many ways . Most of the mods were for guitar use . I was wondering what mods are being done for harp ? I use an Akai DM13 mic through reverb and delay pedals and prefer a bit cleaner tone . Of course I'll try this out first , but am looking for recommendations to shape the tone in different ways . Tube and speaker swaps are common , but which ones ? Also saw that pots can be fairly easily used in place of the resistors for bass , mid , and treble to give adjustability . Any and all opinions would be appreciated .
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rogonzab
965 posts
Jul 07, 2016
6:31 AM
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http://www.modernbluesharmonica.com/blues_harp_forum_search.html
LOTS of info.
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Sorry for any misspell, english is not my first language.
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Killa_Hertz
1670 posts
Jul 07, 2016
5:05 PM
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Good choice. I love mine. I also absolutely love the DM13. I've tried many mics and always come back to the cheapo dm13. .. lol.
There are two main mods.
The Jim Rosen mods (which i have)
And the Alnicomagnet mods.
A quick Google search should bring them up
They are all fairly easy to do. Just makes it a little dirtier and feedback resistant. Althought i didn't have to do them myself because i bought it already modded from bealzebob. I love it.
A line out is also a good idea. Again plenty of info out there on them. Google search "VHT Harp Mods"
Good luck
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Barley Nectar
1239 posts
Jul 07, 2016
5:06 PM
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Cleaner, reduce gain with tube swaps. Use a vocal mic like an SM57, SM58, Audix Fireball. Get a Weber 10F150 speaker. Remember this, you have a 6W amp that is very good for harp as is. It will never be a Super Reverb or a Twin...BN
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Kingley
4023 posts
Jul 10, 2016
1:38 AM
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My two cents worth.
Don't bother changing the speaker. The stock one is fine. Change the preamp valve (tube) for a 5751. Put a JJ 6V6 in the power valve.
Then follow either the Jim Rosen mods or these from Mark Burness (5F6H). Providing you know how to solder, they'll only cost you a few dollars and take about 20 minutes to do.
Here's the Mark Burness suggested mods. I did them in my VHT and it sounds great.
"FreeWilly, there's a few other things you can try, you have done a couple of these already. I do not own & never have owned a VHT Special 6 (but never say never...), these suggestions are just that, suggestions:
C8 - 4.7uf is too small, 25uf/25v would be better, no need to go much bigger with a small amp. Observe correct polarity (waisted end to valve pin).
R12 - Bypass with plain wire, this turns off your "treble pot"...which you can't adjust otherwise (whether in clean or boost modes).
R13 - This is the "bass" resistor 33K is quite small a value, I'd look more at 150K to 220K (bass full up).
C11 - remove.
C13 - remove.
Optional/fine tuning:
C15 try removing, this will lower gain at the power tube, if it kills the amp tone, just refit (observing polarity).
R17 - Run a 33K or 47K 1/2W resistor from the valve side of this resistor to the hot speaker jack terminal - this makes a 'negative feedback loop', I normally prefer a loop on SE amps as they can be a bit bitey without. If your amp has a 4/8ohm speaker use a 22K resistor. WARNING: After fitting this loop, your amp may howl as soon as you turn it on, this is because it was built without a loop and OT polarity didn't matter - now you have a loop it does! If you get howling either detach the loop, or switch around the blue & red wires from the output transformer primary, that connect to 6V6 pin 3 & "B+ 1".
R8 - I like 2K to 2.2K 1/2W here to reduce fuzziness with a mic.
R5 - Try larger values to brown off the tone, the bigger you go the less voltage on the preamp valve & grindier the sound, I'd guess at ~47K (2-3W rating) might be around your useful limit?
The footswitchable "clean/boost" is a resistor that almost disconnects the tone stack, perhaps leaving the amp not quite identical to a 5F2A, but along similar lines.
Observe proper safety protocols (with the amp unplugged from wall AC, throwing the standby into "play" mode should drain your caps via R25)".
Last Edited by Kingley on Jul 10, 2016 1:39 AM
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jimr
94 posts
Jul 10, 2016
3:39 PM
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Rossen is spelled with two S's.
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Kingley
4025 posts
Jul 10, 2016
10:25 PM
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Sorry Jim. Duly noted for future reference.
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Chaz
3 posts
Jul 11, 2016
5:20 AM
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My first amp and I still have it... sounded very good out of the box, but I just can't help myself... plenty of great advice, links... I kept it simple: Swapped speaker for Eminence Ramrod. After break in it had definitely some more punch, depth and bottom end to my ears. I have heard good things about the Eminence Lil' Buddy (a bit softer around the edges) in there as well. Mine already had JJ 6v6's, so I left those, but I switched out the pre-amp tube to either a JJ 12au7 (sweeeet tone, can completely pin the volume knob and the tone control becomes useable) or a JJ 5751 (more power with still a decent amount of headroom and nice tone) depending on the situation and my mood.
And I took the logo plate off because that font is just plain old hideous! LOL
Last Edited by Chaz on Jul 11, 2016 5:23 AM
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artcarny
15 posts
Jul 12, 2016
2:56 PM
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Last Edited by artcarny on Jul 14, 2016 10:18 AM
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artcarny
16 posts
Jul 14, 2016
10:21 AM
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Couldn't stand that VHT logo either. Made my own based on the Special 6 script.A designer from VHT contacted me when he saw it on a guitar forum.Said he wanted one.I told him to start making them that way.
Last Edited by artcarny on Jul 14, 2016 10:22 AM
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Bugfan
44 posts
Jul 14, 2016
3:55 PM
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My special 6 I changed the input resistor R7 to 5 Meg, cut the C11, changed R10 from 180k to 100k, Changed R12 from 27k to 1.5k. Sounds great for harp with std speaker - more bass , less treble and has a slight natural reverb to it .
I have now got the special 44 and building it into a 1949 Fender TV front Pro Amp with a 15" Alnico from WGS. Sounds pretty cool so far. Will change the coupling caps for more bass and may do similar tone stack mods to above. The variable watts is great - not so much for volume but more that you can dial in the amount of breakup.
@artcarny - I like that logo - might do a smaller version on my 44 when completed instead of the Fender logo plaque that was on the 49 Pro amp....sort of looks like an old truck logo eh!
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Halffast
49 posts
Jul 15, 2016
12:55 PM
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Just got mine and I'm impressed . Only got to play with it for about an hour . Did a gig with it last night . Smaller venue (with a 15 seat bar , 8 booths , three very long tables , and a few odd 2 tops ) that seats about 75 to 80 . Amp was plenty loud for me and the guitarist/vocalist . Played my Akai DM13 through my reverb pedal , delay pedal , and Nady mixer . Used the Hi input and high power . Tone was set on 9 o'clock with volume at about 2:30 . Mic pot was set about halfway and I turned the mixer volume down until I didn't get feedback ( about 12 o'clock on the mic channel and the master on full ) . This gave me a nice , clean sound that had decent bass without too much treble with a loose cup of the mic . Cup it harder and dig in and it had some grunt . Right out of the box , without speaker break in time , I couldn't have asked for anything more . I think the speaker will be fine but would like to run the amp through a nice 12" cabinet once just to hear it . Will eventually try the tube swap dealios just because everybody else does it . Still like the idea of individual bass , mid , and treble pots . My buddy on guitar asked about adding a line out to run through his PA system if we play outside or at a larger venue . Great sound with many , fairly easy, mod options for $200 . It was definitely the best choice for me .
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