Latest NoN HRM build

roknroll · Post by **roknroll** » Thu Jul 03, 2008 12:42 am

Hello all
I just completed my 3rd build and am disappointed. I built my first 50w which was an HRM about 3 years ago. It worked but sounded terrible. After a year of monkeying with it I go t disgusted and took it apart and built a different amp altogether. My 2nd attempt was a non hrm with a built in Dlator
. I adhered to recommended parts (caps and resistors). The amp sounded good. Actually it sounded real good. BUT, it did not have THE TONE. It was such a nice sounding amp that someone bought from me site unseen. So I needed a replacement. This time I built another non hrm using proper parts and lead dress I think(copied from pics of one of ayan's amp. No Dlator, no relay switching. All hand toggles for the functions. The amp is dead quiet. BUT it is sterile, stiff, and did I say sounds like yuk. There is no rich singing looseness. My voltages are all within 5% of recommended preamp. 438 on plates of 2 new 6L6's.
Custom made 4-8-16 ohm tap Heyboer OT built like a Blackface Bassman Transformer but w/ 3 taps. Photo of guts attached. Any ideas?

Bob-I · Post by **Bob-I** » Thu Jul 03, 2008 3:11 am

Looks ok, different layout than most but not a bad layout at all.

What tubes and speakers are you using?

Where in NY do you live? I'm in NJ near Somerville so if you're in the city maybe we can find time to get together at my place. There's a train station 3 miles from here.

heisthl · Post by **heisthl** » Thu Jul 03, 2008 4:26 am

V1 Cathode resistors swapped? Please post plate and cathode voltages and PI tail voltages.

dogears · Post by **dogears** » Thu Jul 03, 2008 12:41 pm

What is that funny V1b grid resistor setup?

Also, try better quality shielded cable, especially on the clean side. The stuff you used measures close 70pf per foot (if it is what I think it is). If it is under 30pf then it is ok.

Try using 4.7uf on both sides of V1.

Your OD trim pot is awfully close th V1B. I wonder if there is any interactions there. Try disconnecting the connection from the feedback loop and see if the loop was picking up signal off of the OD pot.

bluesfendermanblues · Post by **bluesfendermanblues** » Thu Jul 03, 2008 3:18 pm

One suggestion is patience !!!

DON'T expect a new amp with new unused components to be sweet and soft sounding. It takes a month at least for the Orange Drops to "burn in"

bluesfendermanblues · Post by **bluesfendermanblues** » Thu Jul 03, 2008 3:18 pm

dbl post

talbany · Post by **talbany** » Thu Jul 03, 2008 3:53 pm

Personally I would un twist the output transformers primary wires going to the tubes. You may have some cancelations going on there...

Tony VVT

roknroll · Post by **roknroll** » Fri Jul 04, 2008 1:06 am

Bob-I wrote:Looks ok, different layout than most but not a bad layout at all.

What tubes and speakers are you using?

Where in NY do you live? I'm in NJ near Somerville so if you're in the city maybe we can find time to get together at my place. There's a train station 3 miles from here.

Thanks for the invite, that is very nice of you and much appreciated, will keep it in mind although it is quite a hike from Babylon LI.
Power tubes are 2 brand new Sovtek 6l6wxt v1 is a new sovtek 12ax7lps and v2.v3. are new jj ecc83.
I have one of each of the following Marshall 4-12 cabs loaded with 4-12 each of G12-65 Heritage, G1265 original, G12T-75 English, G12-80 English and a 2-12 Avatar open back loaded with Tone Tubby alnicos. All harsh, sterile.
Thanks
Jack

roknroll · Post by **roknroll** » Fri Jul 04, 2008 2:33 am

heisthl wrote:V1 Cathode resistors swapped? Please post plate and cathode voltages and PI tail voltages.

Checked resistors they are correct.
V1 pin1 194
V1 pin6 197
V1 pin3 1.54
V1 pin8 1.47
V2 pin1 201
V2 pin6 209
V2 pin3 1.92
V2 pin8 1.79
V3 pin 1 288
V3 pin 6 280
V3 pin 2 2.2
V3 pin 7 2.7
V3 pin 3,8 4.9
V4,5 pin 3 444
pin4 443
37 ma

roknroll · Post by **roknroll** » Fri Jul 04, 2008 2:44 am

dogears wrote:What is that funny V1b grid resistor setup?

Also, try better quality shielded cable, especially on the clean side. The stuff you used measures close 70pf per foot (if it is what I think it is). If it is under 30pf then it is ok.

Try using 4.7uf on both sides of V1.

Your OD trim pot is awfully close th V1B. I wonder if there is any interactions there. Try disconnecting the connection from the feedback loop and see if the loop was picking up signal off of the OD pot.

V1b grid resistor is correct, although I used a 500pf cap it is not ceramic disc. I will make that change and see what happens.
Nom. Capacitance Conductor to Conductor @ 1 kHz: 34 pF/ft
Nom. Cap. Cond. to other Cond. & Shield @ 1 kHz: 67pF/ft
I am only using 1 conductor so I am not sure which catagory it fits in to.
Will change 5.0 uf to 4.7.
Thanks for your input
Jack

roknroll · Post by **roknroll** » Fri Jul 04, 2008 2:46 am

talbany wrote:Personally I would un twist the output transformers primary wires going to the tubes. You may have some cancelations going on there...

Tony VVT

Thanks I will try this as well.

Jack

phsyconoodler · Post by **phsyconoodler** » Fri Jul 04, 2008 3:00 am

Punt the Sovteks!~ Those are amoung the most sterile sounding tubes especially preamp.
JJ's for preamp or Tung Sol.The Sovtek power tubes are ok but there are better.Tung Sol,TAD,Svetlana.All are worlds better that Sovtek.
Also get some hours on the build.They start to sound best after about 40 hrs of use.

Also the grid wires are very long.That only adds to your pf/ft when using shielded cables.I like to have my tubes closer to the board and the pots close too.

heisthl · Post by **heisthl** » Fri Jul 04, 2008 3:20 am

Cathode of V3 should be 50 to 55 volts or therabouts.

dogears · Post by **dogears** » Fri Jul 04, 2008 6:07 pm

No need to change 5uf to 4.7uf. I was thinking the aluminum one was a 1uf

Also, I would change the shielded cable. I think the 67pf may be what you are experiencing. Conductor to shield. Use some good cable. It is noticeable.

roknroll wrote:
dogears wrote:What is that funny V1b grid resistor setup?

Also, try better quality shielded cable, especially on the clean side. The stuff you used measures close 70pf per foot (if it is what I think it is). If it is under 30pf then it is ok.

Try using 4.7uf on both sides of V1.

Your OD trim pot is awfully close th V1B. I wonder if there is any interactions there. Try disconnecting the connection from the feedback loop and see if the loop was picking up signal off of the OD pot.
V1b grid resistor is correct, although I used a 500pf cap it is not ceramic disc. I will make that change and see what happens.
Nom. Capacitance Conductor to Conductor @ 1 kHz: 34 pF/ft
Nom. Cap. Cond. to other Cond. & Shield @ 1 kHz: 67pF/ft
I am only using 1 conductor so I am not sure which catagory it fits in to.
Will change 5.0 uf to 4.7.
Thanks for your input
Jack

roknroll · Post by **roknroll** » Sat Jul 05, 2008 3:21 am

heisthl wrote:Cathode of V3 should be 50 to 55 volts or therabouts.

heisthl
Thanks for that clue. I did some checking and realized I completely left out the 24k tail resistor.

I did untwist the ot primaries
Voltage at the catode of V3 is now in the low 60's.
What is the favorite low pufs shielded cable around here at the best price?
How is Gepco XB401 17.5 pF/ft between conductors,
31 pF/ft between one conductor and other tied to shield
24g
.32/ft at 100 foot rolls
BTW the amp sounds excellent now through a Marshall 412 g1265
Thank you all who wrote back.
Regards
Jack

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