Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Toxophilite on January 07, 2014, 01:53:05 pm
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Hello
I have some transformer questions to ask largely based on.. well.. ignorance!
I have a little vibrolux build I completed a month or so back using somebodies 50s hombuilt PA/instrument amplifier as a platform
It was a 2 6V^ pushpull witha 5Y3 a 12AU7 and a 12AX7
I change the 12AU7 to a 12AX7 and rebuilt the entire thing.
It sounds good albeit a little noisy.
It has quite nice Hammond transformers in it
A 272Z60 power transformer and a 1618 output transformer with 3 taps (4, 8 and 16 ohm)
I have a hammond catalog download that lists the Output Transformer as:
Push pull good with the 6F6 6A6 6V6 and 6AQ5
15 watts primary 10000 ct
A - 2 1/3 B - 2 1/4 D - 2 1/2 H - 3 W - 3 Wt - 3
The Power TRansformer has the following information:
Cy 60
Va 70
Secondary Volts 310 - 310
DCma 70
Fil#1 (rectifier) - 5.0 v 2a
Fil #2 6.3v 2.4a
A 3 1/8 B 2 1/2 D 3 3/4 H 3 5/8 W 3 1/8 Wt 4 1/2
I understand some of this but not necessarily how it applies (besides filiments etc)
Of the common fender 6V6 power amp based amplifiers
How many of them could they work for
Just the lower powered 5Y3 units ?
Or could they be good for one of the more powerful /clean GZ34 amps
Hopefully my question isn't too dim!
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Secondary Volts 310 - 310
DCma 70
This is kinda lite weight in the current. Best to stay with a smaller amp.
Fil#1 (rectifier) - 5.0 v 2a
Can heat a GZ34 just fine.
Fil #2 6.3v 2.4a
This can heat 2 x 6V6s and 5 x 12__7s.
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I have a little vibrolux build I completed a month or so back using somebodies 50s hombuilt PA/instrument amplifier as a platform
What we see of the wood cabinet looks good, as does the JBL speaker (BTW, that's an 8Ω speaker in spite of the 16Ω marking).
... hammond catalog download that lists the Output Transformer as:
Push pull ... 15 watts primary 10000 ct
...
Secondary Volts 310 - 310
DCma 70
..
Of the common fender 6V6 power amp based amplifiers
How many of them could they work for
Just the lower powered 5Y3 units ?
Or could they be good for one of the more powerful /clean GZ34 amps
As Sluckey said, you can use a GZ34.
10kΩ 15w OT is roughly like a Tweed Deluxe (we normally figure 8kΩ for it). 310-0-310v @ 70mA seems workable for a Tweed Deluxe or blackface Princeton Reverb.
10kΩ OT, 6V6's and 70mA from the PT aren't a recipe for "more power". I'd say what you have is what you have, with room to tinker the preamp. But I bet it sounds pretty good with that JBL...
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What is your biggest complaint about the amp, if any? Noise? Underpower?
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My biggest complaint would be hum at louder volumes..however that increased when I added a circuit to get the necessary negative voltage for the tremelo off of one of the rectifier plates. It's also pretty cramped point to point inside that little chassis.It is star grounded though and has had all caps replaced with new(including of course the filter caps)
If I can get a picture of the inside(I have to yank it out of it's cabinet) I'll put it up to see if someone can help with the hum factor
It's a nice sounding amp and the tremelo works well (I couldn't find a 2 meg pot so I have a 1 meg, a switch and a 1 meg resistor)
I also have an on/off switch for the negative feedback..I mostly leave it on though as I generally like the clean flatter response tones.
I also put in a baxandall type of tone control..though I might try it with the original arrangement as well.
Almost everything sounds good through a JBL! in my humble opinion.
And they're so efficient you get a lot of bang for your buck. It's about loud enough to play with a quiet band.
It's one of teh earlier Hifi models rather than a D130F.
I got it for a decent price as the fellow told me it was a recone because it measured 8 ohms.. I've since read they all do
I was thinking of gooping the surround eventually if I can find a source for an appropriate goop
The cabinet is made from a recycled antique free standing clothing cabinet that somebody had bust up. It has lovely birds eye maple veneer on the outside,mahongany on the inside and recycled hardware and grill cloth . Generally how I make most of this stuff. I usually spend my money on new internal components(resis, caps, etc)
As far as my requests for information goes. I like to tinker and I was just curious as to what I could mess around with for fun.
Also not all the information in the catalog makes sense to me with my limited electronics knowledge
I appreciate the insights
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This forum is much better than others .. what do you say now ?
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I'm enjoying myself, Thanks Floyd
Though when you commented on the other forum as Withnal, I was just waiting for the approval for this site.
All is well!
Here's a picture of the front of the little vibrolux build with the D130
Please excuse the non-mitered corners to the front trim..I was using old solid maple organ foot pedals after i had finished the cabinet and they were just about 3/4" too short on the long side to do nice mitered corners!
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... I got it for a decent price as the fellow told me it was a recone because it measured 8 ohms.. I've since read they all do
It'll likely read a bit over 6Ω DCR.
According to Harvey Gerst, who worked for JBL and designed the D130F, all D130's were 8Ω speakers because they found that attaching an 8Ω speaker to the 16Ω tap of available hi-fi's at that time sounded really good. So they marked the 8Ω speakers "16Ω".
You can also find pictures of some that say "8-16Ω" but again these are 8Ω speakers.
My biggest complaint would be hum at louder volumes..however that increased when I added a circuit to get the necessary negative voltage for the tremelo off of one of the rectifier plates. ... It is star grounded though and has had all caps replaced with new(including of course the filter caps)
If I can get a picture of the inside(I have to yank it out of it's cabinet) I'll put it up to see if someone can help with the hum factor ...
Is this the same amp as in the other thread? Just wondering because there was a chassis pic there, and going back & forth between threads is confusing (given you have at least 2 conversions from this style of donor amp).
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Sorry for the confusion
This is not the same amp as the other thread
This is a mostly finished build(using an existing amp and rewiring it from scratch)that I might tweek a bit further
I started a different thread on it, to ask about transformers in general.
And yes when I said it measured 8 ohms I meant it measured what an 8 ohm speaker would measure with an meter, Usually just over 6 ohms as you said.
The other thread is a build I'm just starting and making decisions about prior to reconstruction.