Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jamesedmunda on July 26, 2019, 06:54:14 pm

Title: silvertone 1484 sounds dirty
Post by: jamesedmunda on July 26, 2019, 06:54:14 pm

Can anyone help me. The amp sounds pretty good but I think it's a little dirty. The red is the volltages I'm seeing. All new elecrolytic caps, any out of tolerance resistors replaced. I used a 10 uf instead 5 in the can. the inputs are fender, high low, new Classic tone OT. tubes are strong. Does the voltage coming out of the Tremolo light side of LDR look right. Trem works good so the bulb is working. The 6l6's are drawing about 35ma I also replaced the diodes with 14007's. Any help much appreciated.

Title: Re: silvertone 1484 sounds dirty
Post by: tubenit on July 26, 2019, 09:01:00 pm

I'm thinking you want more headroom?   On the B+ rail  R58 & R59 are 68k resistors.  You could consider lowering the values there using correct wattage resistors to increase the voltages on V1 & V2 plates? 

Maybe something like 33k for R58 and 22k for R59.  You'd have to experiment with that.  With 12AX7's, I am usually wanting the voltages on the plates to be 160v -200v for a cleaner tone and close to 140v for more of a tweed tone. 

Another options may be to try a 12AY7 in V1?

With respect, Tubenit

Title: Re: silvertone 1484 sounds dirty
Post by: choosebronze on July 26, 2019, 11:38:55 pm

I'm not trying to be a smart ass but isn't that how 1484's sound? I mean, they aren't renowned for clean tone, right? They're dirty amps.

Title: Re: silvertone 1484 sounds dirty
Post by: sluckey on July 26, 2019, 11:50:52 pm

I had a brand new one in the '60s. It was a clean sounding amp.

Title: Re: silvertone 1484 sounds dirty
Post by: nandrewjackson on July 27, 2019, 01:41:53 am

+1 *tubenit*


Lower those power rail resistors, 22K each


Any gut shot pics?

Title: Re: silvertone 1484 sounds dirty
Post by: tubenit on July 27, 2019, 06:24:45 am

Quote

I had a brand new one in the '60s. It was a clean sounding amp.

  per Sluckey

This YouTube video demos/confirms that the 1484 is reasonably clean amp which the owner confirms.

Title: Re: silvertone 1484 sounds dirty
Post by: ginger on July 27, 2019, 10:52:53 am

I've repaired two in the last year.. was also expecting dirty . They sounded thick , yet pretty clean ... if the bias is close to what it's supposed to be .

Title: Re: silvertone 1484 sounds dirty
Post by: ginger on July 27, 2019, 10:59:30 am

This a 1485... same amp , only with two output transformers... not fun to service .

Title: Re: silvertone 1484 sounds dirty
Post by: choosebronze on July 27, 2019, 11:04:17 am

Yea sorry I had the model numbers confused. I looked them up. The only Silvertone I've played was a 1482.

Title: Re: silvertone 1484 sounds dirty
Post by: jjasilli on July 27, 2019, 11:14:16 am

Seems that clean/dirty is on a continuum.  In the middle is a range which some people consider clean, others dirty.  Tubenit's clip sounds dirty to me, though he anD sluckey might consider it to be clean.


I consder bargain basenent guitar amps generally to sound grungy. To me that's their "charm" thiugh that renders them one trick ponies.  YMMV

Title: Re: silvertone 1484 sounds dirty
Post by: jamesedmunda on July 28, 2019, 10:38:22 am

Thanks guys switched r58 +59 to 22k and r27 to 150k to get the plate voltages up and it sounds good.
 Turns out my main problem was the speaker.