dlite build with nasal quality on od

[phillyhudson]

I have a dlite type build with transformers from a deluxe reverb.[2 6v6,s] and i cant seem to do anything about a nasal quality it has.I,ve tried all the usual changes to no avail.I,ve built a 124 with trannys from a twin and that sounds great but am at wits end with smaller amp.I just wondered if the transformers are giving it a different sound coz the pre/power amps are almost exactly the same in both amps but one sounds like it should and the other doesnt.
also big big thanks to all people on this forum who continually give their time and expertise to help part time solderers like myself.
phil

[Fischerman]

Have you tried preamp out from one amp into the power amp in of the other...then switch roles? That would tell you if it's the power section or not.

[phillyhudson]

just tried that thanks and it makes it much better putting the dlite pre thro 124 power which must mean its something in the dlite power stage.
I,ve used the usual 4 x 47uf with 2k2,22k and 2k2 between them and 2x 100uf caps with 220k between them with a 470r as choke so what do you think might be causing the trouble ?
thanks in advance
phil

[dogears]

Add another 470 across the choke resistor. Or change to a real choke. Much less nasal I bet.

Also, make sure the Dlite presence is wired the Dumble way. Pot not grounded. Just the cap and 390r. Do you have the stack wired with the bass pot lugs connected? They should be.

just tried that thanks and it makes it much better putting the dlite pre thro 124 power which must mean its something in the dlite power stage.
I,ve used the usual 4 x 47uf with 2k2,22k and 2k2 between them and 2x 100uf caps with 220k between them with a 470r as choke so what do you think might be causing the trouble ?
thanks in advance
phil

[phillyhudson]

just tried adding other 470r on choke and already have bass pot lugs connected and the presence [not going to ground] i have switching in with 390 r on a relay when the od is engaged and nothing when the clean channel is on.
Still the same !
I,ve also just double checked all voltages which seem to be ok.
the next stage is going to be building a big bonfire in the garden and throwing it on top !

[10thTx]

Since you have referenced it being in the power amp:

Just a thought ......... I have an amp (Carolina Blues Rocket) that has alot of Dumble preamp topology. Using Tung Sol 6V6 tubes ....... it sounds somewhat nasal to me. Using JJ 6V6 ....... it sounds much better and clearer with less nasal tone. The Tung Sol 6V6's almost sounded like using a wah pedal at halfway. Using 5881's ....... it sounds better still.

With respect, 10thtx

[dogears]

Try changing CL2 coupler to a .02uf

Also, lower V1 bypass caps to 4.7uf

Let me know....

just tried adding other 470r on choke and already have bass pot lugs connected and the presence [not going to ground] i have switching in with 390 r on a relay when the od is engaged and nothing when the clean channel is on.
Still the same !
I,ve also just double checked all voltages which seem to be ok.
the next stage is going to be building a big bonfire in the garden and throwing it on top !

[Normster]

The first D'Lite prototype used a Deluxe Reverb OPT and never sounded quite right. That's why I went to the Vibrolux iron. You can try increasing/reducing the size of the feedback resistor to flatten the frequency response, but IMHO, the DR iron just doesn't cut it for a Dumble style amp.

OTOH, Bob-I has built some pretty stellar amps using small iron so maybe he can give you a few tips on how to tweak out the nasally tone.

[Fischerman]

Just an observation (you might have already noticed this phillyhudson), but there are at least two ways to approach this (let's rule out the 'bonfire' option for now ):
1) Mod the power amp to work with your 'nominal' ODS preamp
2) Mod the preamp to suit the power amp you already have

Neither is necessarily better than the other (that I know of)...just two different approaches. Sounds like Scott is trying to mod the preamp to suit the power amp you already have and then others are advocating modding the power amp (up to swapping out the OT). It might be that you need to do both but IMO you might want to focus on one or the other at first.

Just curious but what impedance cabinet are you using? If you are using the wrong impedance cabinet for that OT then you'll reduce bandwidth and that can contribute to a nasally tone. A Deluxe Reverb OT should be for an 8 ohm cabinet.

[phillyhudson]

thanks for all the suggestions lads !
I,ve already tried the bypass 4.7uf cap and .02 CL2 coupler but still the same - its actually not that bad a sound but not quite what I,m after.
I,ve got a couple of OT,s knocking around from some different english amps - going to see if any of these will work.
I,ve actually got some decent sounds out of adding a dumble style lead on to a 70,s carlsbro 50 top amp [partridge trannys] - I know its not a dumble but i still like the sound of it.here,s an example - not very good recording but guitars-ok its a les paul with 2 x12 eminence rwb
http://profile.myspace.com/index.cfm?fu ... =362766265
thanks for continued suggestions - if I wanted to try a fender type tranny would the vibrolux be the best to go for ?
ta
phil

[dogears]

Phil,

If you swap iron, go all the way and make it a 50 watt. Use a new PT and OT. Get the biggest OT you can fit. You won't regret it.

[phillyhudson]

could I use the trannys from 50 watt carlsbro 50 top amp ?
http://www.chambonino.com/carlsbro/carl50top.html
with two 6v6's ?
hopefully, yet resigned to dissapointment,
phil

[dogears]

6L6 baby!

[phillyhudson]

aha ! gawd bless ya guv , will start on sorting out the chassis tommorow - is it worth just changing OT first and seeing the difference ? or just go the whole hog and change both ?
gratefully relieved ,
phil

[jelle]

Hi,

I've used partridge iron in my HRM ODS. Great iron! I'd suggest to use the PT and use ca 100uf filtering for the plates of the two 6L6GC's. Use a choke and 470 ohms screen resistors. NFB from the 4 ohms tab.

Have Fun!

jelle